| blob | 44d1bd142edf83fdf7c83ee509c44c0b6b20a136 |
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 (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 .
105 In addition, the following text indicates that the option:
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.
111 Parameters denoted with BOOT are actually interpreted by the boot
112 loader, and have no meaning to the kernel directly.
113 Do not modify the syntax of boot loader parameters without extreme
114 need or coordination with <Documentation/i386/boot.txt>.
116 There are also arch-specific kernel-parameters not documented here.
117 See for example <Documentation/x86_64/boot-options.txt>.
119 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
120 a trailing = on the name of any parameter states that that parameter will
121 be entered as an environment variable, whereas its absence indicates that
122 it will appear as a kernel argument readable via /proc/cmdline by programs
123 running once the system is up.
125 The number of kernel parameters is not limited, but the length of the
126 complete command line (parameters including spaces etc.) is limited to
127 a fixed number of characters. This limit depends on the architecture
128 and is between 256 and 4096 characters. It is defined in the file
129 ./include/asm/setup.h as COMMAND_LINE_SIZE.
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.
142 See also Documentation/power/pm.txt, pci=noacpi
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
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).
162 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
163 Format: { level | edge | high | low }
165 acpi_irq_balance [HW,ACPI]
166 ACPI will balance active IRQs
167 default in APIC mode
169 acpi_irq_nobalance [HW,ACPI]
170 ACPI will not move active IRQs (default)
171 default in PIC mode
173 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
174 use by PCI
175 Format: <irq>,<irq>...
177 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
178 Format: <irq>,<irq>...
180 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
182 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
183 Format: To spoof as Windows 98: ="Microsoft Windows"
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
190 acpi_serialize [HW,ACPI] force serialization of AML methods
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
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.
217 acpi.debug_level= [HW,ACPI]
218 Format: <int>
219 Each bit of the <int> indicates an ACPI debug level,
220 which corresponds to the level in an ACPI_DEBUG_PRINT
221 statement. After system has booted up, this mask
222 can be set via /sys/module/acpi/parameters/debug_level.
224 CONFIG_ACPI_DEBUG must be enabled for this to produce
225 any output. The number can be in decimal or prefixed
226 with 0x in hex. Some of these options produce so much
227 output that the system is unusable.
229 The following global components are defined by the
230 ACPI CA:
231 0x01 error
232 0x02 warn
233 0x04 init
234 0x08 debug object
235 0x10 info
236 0x20 init names
237 0x40 parse
238 0x80 load
239 0x100 dispatch
240 0x200 execute
241 0x400 names
242 0x800 operation region
243 0x1000 bfield
244 0x2000 tables
245 0x4000 values
246 0x8000 objects
247 0x10000 resources
248 0x20000 user requests
249 0x40000 package
250 The number can be in decimal or prefixed with 0x in hex.
251 Warning: Many of these options can produce a lot of
252 output and make your system unusable. Be very careful.
254 acpi_pm_good [X86-32,X86-64]
255 Override the pmtimer bug detection: force the kernel
256 to assume that this machine's pmtimer latches its value
257 and always returns good values.
259 agp= [AGP]
260 { off | try_unsupported }
261 off: disable AGP support
262 try_unsupported: try to drive unsupported chipsets
263 (may crash computer or cause data corruption)
265 enable_timer_pin_1 [i386,x86-64]
266 Enable PIN 1 of APIC timer
267 Can be useful to work around chipset bugs
268 (in particular on some ATI chipsets).
269 The kernel tries to set a reasonable default.
271 disable_timer_pin_1 [i386,x86-64]
272 Disable PIN 1 of APIC timer
273 Can be useful to work around chipset bugs.
275 ad1848= [HW,OSS]
276 Format: <io>,<irq>,<dma>,<dma2>,<type>
278 advansys= [HW,SCSI]
279 See header of drivers/scsi/advansys.c.
281 advwdt= [HW,WDT] Advantech WDT
282 Format: <iostart>,<iostop>
284 aedsp16= [HW,OSS] Audio Excel DSP 16
285 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
286 See also header of sound/oss/aedsp16.c.
288 aha152x= [HW,SCSI]
289 See Documentation/scsi/aha152x.txt.
291 aha1542= [HW,SCSI]
292 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
294 aic7xxx= [HW,SCSI]
295 See Documentation/scsi/aic7xxx.txt.
297 aic79xx= [HW,SCSI]
298 See Documentation/scsi/aic79xx.txt.
300 amd_iommu= [HW,X86-84]
301 Pass parameters to the AMD IOMMU driver in the system.
302 Possible values are:
303 isolate - enable device isolation (each device, as far
304 as possible, will get its own protection
305 domain)
306 amd_iommu_size= [HW,X86-64]
307 Define the size of the aperture for the AMD IOMMU
308 driver. Possible values are:
309 '32M', '64M' (default), '128M', '256M', '512M', '1G'
311 amijoy.map= [HW,JOY] Amiga joystick support
312 Map of devices attached to JOY0DAT and JOY1DAT
313 Format: <a>,<b>
314 See also Documentation/kernel/input/joystick.txt
316 analog.map= [HW,JOY] Analog joystick and gamepad support
317 Specifies type or capabilities of an analog joystick
318 connected to one of 16 gameports
319 Format: <type1>,<type2>,..<type16>
321 apc= [HW,SPARC]
322 Power management functions (SPARCstation-4/5 + deriv.)
323 Format: noidle
324 Disable APC CPU standby support. SPARCstation-Fox does
325 not play well with APC CPU idle - disable it if you have
326 APC and your system crashes randomly.
328 apic= [APIC,i386] Advanced Programmable Interrupt Controller
329 Change the output verbosity whilst booting
330 Format: { quiet (default) | verbose | debug }
331 Change the amount of debugging information output
332 when initialising the APIC and IO-APIC components.
334 apm= [APM] Advanced Power Management
335 See header of arch/x86/kernel/apm_32.c.
337 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
338 Format: <io>,<irq>,<nodeID>
340 ataflop= [HW,M68k]
342 atarimouse= [HW,MOUSE] Atari Mouse
344 atascsi= [HW,SCSI] Atari SCSI
346 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
347 EzKey and similar keyboards
349 atkbd.reset= [HW] Reset keyboard during initialization
351 atkbd.set= [HW] Select keyboard code set
352 Format: <int> (2 = AT (default), 3 = PS/2)
354 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
355 keyboards
357 atkbd.softraw= [HW] Choose between synthetic and real raw mode
358 Format: <bool> (0 = real, 1 = synthetic (default))
360 atkbd.softrepeat= [HW]
361 Use software keyboard repeat
363 autotest [IA64]
365 baycom_epp= [HW,AX25]
366 Format: <io>,<mode>
368 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
369 Format: <io>,<mode>
370 See header of drivers/net/hamradio/baycom_par.c.
372 baycom_ser_fdx= [HW,AX25]
373 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
374 Format: <io>,<irq>,<mode>[,<baud>]
375 See header of drivers/net/hamradio/baycom_ser_fdx.c.
377 baycom_ser_hdx= [HW,AX25]
378 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
379 Format: <io>,<irq>,<mode>
380 See header of drivers/net/hamradio/baycom_ser_hdx.c.
382 boot_delay= Milliseconds to delay each printk during boot.
383 Values larger than 10 seconds (10000) are changed to
384 no delay (0).
385 Format: integer
387 bootmem_debug [KNL] Enable bootmem allocator debug messages.
389 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
390 bttv.radio= Most important insmod options are available as
391 kernel args too.
392 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
393 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
395 BusLogic= [HW,SCSI]
396 See drivers/scsi/BusLogic.c, comment before function
397 BusLogic_ParseDriverOptions().
399 c101= [NET] Moxa C101 synchronous serial card
401 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
402 Sometimes CPU hardware bugs make them report the cache
403 size incorrectly. The kernel will attempt work arounds
404 to fix known problems, but for some CPUs it is not
405 possible to determine what the correct size should be.
406 This option provides an override for these situations.
408 security= [SECURITY] Choose a security module to enable at boot.
409 If this boot parameter is not specified, only the first
410 security module asking for security registration will be
411 loaded. An invalid security module name will be treated
412 as if no module has been chosen.
414 capability.disable=
415 [SECURITY] Disable capabilities. This would normally
416 be used only if an alternative security model is to be
417 configured. Potentially dangerous and should only be
418 used if you are entirely sure of the consequences.
420 ccw_timeout_log [S390]
421 See Documentation/s390/CommonIO for details.
423 cgroup_disable= [KNL] Disable a particular controller
424 Format: {name of the controller(s) to disable}
425 {Currently supported controllers - "memory"}
427 checkreqprot [SELINUX] Set initial checkreqprot flag value.
428 Format: { "0" | "1" }
429 See security/selinux/Kconfig help text.
430 0 -- check protection applied by kernel (includes
431 any implied execute protection).
432 1 -- check protection requested by application.
433 Default value is set via a kernel config option.
434 Value can be changed at runtime via
435 /selinux/checkreqprot.
437 cio_ignore= [S390]
438 See Documentation/s390/CommonIO for details.
440 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
441 [Deprecated]
442 Forces specified clocksource (if available) to be used
443 when calculating gettimeofday(). If specified
444 clocksource is not available, it defaults to PIT.
445 Format: { pit | tsc | cyclone | pmtmr }
447 clocksource= [GENERIC_TIME] Override the default clocksource
448 Format: <string>
449 Override the default clocksource and use the clocksource
450 with the name specified.
451 Some clocksource names to choose from, depending on
452 the platform:
453 [all] jiffies (this is the base, fallback clocksource)
454 [ACPI] acpi_pm
455 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
456 pxa_timer,timer3,32k_counter,timer0_1
457 [AVR32] avr32
458 [X86-32] pit,hpet,tsc,vmi-timer;
459 scx200_hrt on Geode; cyclone on IBM x440
460 [MIPS] MIPS
461 [PARISC] cr16
462 [S390] tod
463 [SH] SuperH
464 [SPARC64] tick
465 [X86-64] hpet,tsc
467 clearcpuid=BITNUM [X86]
468 Disable CPUID feature X for the kernel. See
469 include/asm-x86/cpufeature.h for the valid bit numbers.
470 Note the Linux specific bits are not necessarily
471 stable over kernel options, but the vendor specific
472 ones should be.
473 Also note that user programs calling CPUID directly
474 or using the feature without checking anything
475 will still see it. This just prevents it from
476 being used by the kernel or shown in /proc/cpuinfo.
477 Also note the kernel might malfunction if you disable
478 some critical bits.
480 code_bytes [IA32/X86_64] How many bytes of object code to print
481 in an oops report.
482 Range: 0 - 8192
483 Default: 64
485 disable_8254_timer
486 enable_8254_timer
487 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
488 over the 8254 in addition to over the IO-APIC. The
489 kernel tries to set a sensible default.
491 hpet= [X86-32,HPET] option to control HPET usage
492 Format: { enable (default) | disable | force }
493 disable: disable HPET and use PIT instead
494 force: allow force enabled of undocumented chips (ICH4,
495 VIA, nVidia)
497 com20020= [HW,NET] ARCnet - COM20020 chipset
498 Format:
499 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
501 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
502 Format: <io>[,<irq>]
504 com90xx= [HW,NET]
505 ARCnet - COM90xx chipset (memory-mapped buffers)
506 Format: <io>[,<irq>[,<memstart>]]
508 condev= [HW,S390] console device
509 conmode=
511 console= [KNL] Output console device and options.
513 tty<n> Use the virtual console device <n>.
515 ttyS<n>[,options]
516 ttyUSB0[,options]
517 Use the specified serial port. The options are of
518 the form "bbbbpnf", where "bbbb" is the baud rate,
519 "p" is parity ("n", "o", or "e"), "n" is number of
520 bits, and "f" is flow control ("r" for RTS or
521 omit it). Default is "9600n8".
523 See Documentation/serial-console.txt for more
524 information. See
525 Documentation/networking/netconsole.txt for an
526 alternative.
528 uart[8250],io,<addr>[,options]
529 uart[8250],mmio,<addr>[,options]
530 Start an early, polled-mode console on the 8250/16550
531 UART at the specified I/O port or MMIO address,
532 switching to the matching ttyS device later. The
533 options are the same as for ttyS, above.
535 If the device connected to the port is not a TTY but a braille
536 device, prepend "brl," before the device type, for instance
537 console=brl,ttyS0
538 For now, only VisioBraille is supported.
540 earlycon= [KNL] Output early console device and options.
541 uart[8250],io,<addr>[,options]
542 uart[8250],mmio,<addr>[,options]
543 Start an early, polled-mode console on the 8250/16550
544 UART at the specified I/O port or MMIO address.
545 The options are the same as for ttyS, above.
547 no_console_suspend
548 [HW] Never suspend the console
549 Disable suspending of consoles during suspend and
550 hibernate operations. Once disabled, debugging
551 messages can reach various consoles while the rest
552 of the system is being put to sleep (ie, while
553 debugging driver suspend/resume hooks). This may
554 not work reliably with all consoles, but is known
555 to work with serial and VGA consoles.
557 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
558 Format:
559 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
561 crashkernel=nn[KMG]@ss[KMG]
562 [KNL] Reserve a chunk of physical memory to
563 hold a kernel to switch to with kexec on panic.
565 crashkernel=range1:size1[,range2:size2,...][@offset]
566 [KNL] Same as above, but depends on the memory
567 in the running system. The syntax of range is
568 start-[end] where start and end are both
569 a memory unit (amount[KMG]). See also
570 Documentation/kdump/kdump.txt for a example.
572 cs4232= [HW,OSS]
573 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
575 cs89x0_dma= [HW,NET]
576 Format: <dma>
578 cs89x0_media= [HW,NET]
579 Format: { rj45 | aui | bnc }
581 dasd= [HW,NET]
582 See header of drivers/s390/block/dasd_devmap.c.
584 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
585 (one device per port)
586 Format: <port#>,<type>
587 See also Documentation/input/joystick-parport.txt
589 debug [KNL] Enable kernel debugging (events log level).
591 debug_locks_verbose=
592 [KNL] verbose self-tests
593 Format=<0|1>
594 Print debugging info while doing the locking API
595 self-tests.
596 We default to 0 (no extra messages), setting it to
597 1 will print _a lot_ more information - normally
598 only useful to kernel developers.
600 debug_objects [KNL] Enable object debugging
602 debugpat [X86] Enable PAT debugging
604 decnet.addr= [HW,NET]
605 Format: <area>[,<node>]
606 See also Documentation/networking/decnet.txt.
608 vt.default_blu= [VT]
609 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
610 Change the default blue palette of the console.
611 This is a 16-member array composed of values
612 ranging from 0-255.
614 vt.default_grn= [VT]
615 Format: <green0>,<green1>,<green2>,...,<green15>
616 Change the default green palette of the console.
617 This is a 16-member array composed of values
618 ranging from 0-255.
620 vt.default_red= [VT]
621 Format: <red0>,<red1>,<red2>,...,<red15>
622 Change the default red palette of the console.
623 This is a 16-member array composed of values
624 ranging from 0-255.
626 vt.default_utf8=
627 [VT]
628 Format=<0|1>
629 Set system-wide default UTF-8 mode for all tty's.
630 Default is 1, i.e. UTF-8 mode is enabled for all
631 newly opened terminals.
633 dhash_entries= [KNL]
634 Set number of hash buckets for dentry cache.
636 digi= [HW,SERIAL]
637 IO parameters + enable/disable command.
639 digiepca= [HW,SERIAL]
640 See drivers/char/README.epca and
641 Documentation/digiepca.txt.
643 disable_mtrr_cleanup [X86]
644 enable_mtrr_cleanup [X86]
645 The kernel tries to adjust MTRR layout from continuous
646 to discrete, to make X server driver able to add WB
647 entry later. This parameter enables/disables that.
649 mtrr_chunk_size=nn[KMG] [X86]
650 used for mtrr cleanup. It is largest continous chunk
651 that could hold holes aka. UC entries.
653 mtrr_gran_size=nn[KMG] [X86]
654 Used for mtrr cleanup. It is granularity of mtrr block.
655 Default is 1.
656 Large value could prevent small alignment from
657 using up MTRRs.
659 mtrr_spare_reg_nr=n [X86]
660 Format: <integer>
661 Range: 0,7 : spare reg number
662 Default : 1
663 Used for mtrr cleanup. It is spare mtrr entries number.
664 Set to 2 or more if your graphical card needs more.
666 disable_mtrr_trim [X86, Intel and AMD only]
667 By default the kernel will trim any uncacheable
668 memory out of your available memory pool based on
669 MTRR settings. This parameter disables that behavior,
670 possibly causing your machine to run very slowly.
672 dmasound= [HW,OSS] Sound subsystem buffers
674 dscc4.setup= [NET]
676 dtc3181e= [HW,SCSI]
678 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
679 earlyprintk=vga
680 earlyprintk=serial[,ttySn[,baudrate]]
682 Append ",keep" to not disable it when the real console
683 takes over.
685 Only vga or serial at a time, not both.
687 Currently only ttyS0 and ttyS1 are supported.
689 Interaction with the standard serial driver is not
690 very good.
692 The VGA output is eventually overwritten by the real
693 console.
695 eata= [HW,SCSI]
697 edd= [EDD]
698 Format: {"off" | "on" | "skip[mbr]"}
700 eisa_irq_edge= [PARISC,HW]
701 See header of drivers/parisc/eisa.c.
703 elanfreq= [X86-32]
704 See comment before function elanfreq_setup() in
705 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
707 elevator= [IOSCHED]
708 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
709 See Documentation/block/as-iosched.txt and
710 Documentation/block/deadline-iosched.txt for details.
712 elfcorehdr= [X86-32, X86_64]
713 Specifies physical address of start of kernel core
714 image elf header. Generally kexec loader will
715 pass this option to capture kernel.
716 See Documentation/kdump/kdump.txt for details.
718 enforcing [SELINUX] Set initial enforcing status.
719 Format: {"0" | "1"}
720 See security/selinux/Kconfig help text.
721 0 -- permissive (log only, no denials).
722 1 -- enforcing (deny and log).
723 Default value is 0.
724 Value can be changed at runtime via /selinux/enforce.
726 es1371= [HW,OSS]
727 Format: <spdif>,[<nomix>,[<amplifier>]]
728 See also header of sound/oss/es1371.c.
730 ether= [HW,NET] Ethernet cards parameters
731 This option is obsoleted by the "netdev=" option, which
732 has equivalent usage. See its documentation for details.
734 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
735 Format: <io>[,<irq>]
737 failslab=
738 fail_page_alloc=
739 fail_make_request=[KNL]
740 General fault injection mechanism.
741 Format: <interval>,<probability>,<space>,<times>
742 See also /Documentation/fault-injection/.
744 fd_mcs= [HW,SCSI]
745 See header of drivers/scsi/fd_mcs.c.
747 fdomain= [HW,SCSI]
748 See header of drivers/scsi/fdomain.c.
750 floppy= [HW]
751 See Documentation/floppy.txt.
753 force_pal_cache_flush
754 [IA-64] Avoid check_sal_cache_flush which may hang on
755 buggy SAL_CACHE_FLUSH implementations. Using this
756 parameter will force ia64_sal_cache_flush to call
757 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
759 gamecon.map[2|3]=
760 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
761 support via parallel port (up to 5 devices per port)
762 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
763 See also Documentation/input/joystick-parport.txt
765 gamma= [HW,DRM]
767 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
768 Format: off | on
769 default: on
771 gdth= [HW,SCSI]
772 See header of drivers/scsi/gdth.c.
774 gpt [EFI] Forces disk with valid GPT signature but
775 invalid Protective MBR to be treated as GPT.
777 gvp11= [HW,SCSI]
779 hashdist= [KNL,NUMA] Large hashes allocated during boot
780 are distributed across NUMA nodes. Defaults on
781 for IA-64, off otherwise.
782 Format: 0 | 1 (for off | on)
784 hcl= [IA-64] SGI's Hardware Graph compatibility layer
786 hd= [EIDE] (E)IDE hard drive subsystem geometry
787 Format: <cyl>,<head>,<sect>
789 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
790 size of <nn>. This works even on boxes that have no
791 highmem otherwise. This also works to reduce highmem
792 size on bigger boxes.
794 highres= [KNL] Enable/disable high resolution timer mode.
795 Valid parameters: "on", "off"
796 Default: "on"
798 hisax= [HW,ISDN]
799 See Documentation/isdn/README.HiSax.
801 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
802 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
803 On x86-64 and powerpc, this option can be specified
804 multiple times interleaved with hugepages= to reserve
805 huge pages of different sizes. Valid pages sizes on
806 x86-64 are 2M (when the CPU supports "pse") and 1G
807 (when the CPU supports the "pdpe1gb" cpuinfo flag)
808 Note that 1GB pages can only be allocated at boot time
809 using hugepages= and not freed afterwards.
810 default_hugepagesz=
811 [same as hugepagesz=] The size of the default
812 HugeTLB page size. This is the size represented by
813 the legacy /proc/ hugepages APIs, used for SHM, and
814 default size when mounting hugetlbfs filesystems.
815 Defaults to the default architecture's huge page size
816 if not specified.
818 i8042.direct [HW] Put keyboard port into non-translated mode
819 i8042.dumbkbd [HW] Pretend that controller can only read data from
820 keyboard and cannot control its state
821 (Don't attempt to blink the leds)
822 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
823 i8042.nokbd [HW] Don't check/create keyboard port
824 i8042.noloop [HW] Disable the AUX Loopback command while probing
825 for the AUX port
826 i8042.nomux [HW] Don't check presence of an active multiplexing
827 controller
828 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
829 controllers
830 i8042.panicblink=
831 [HW] Frequency with which keyboard LEDs should blink
832 when kernel panics (default is 0.5 sec)
833 i8042.reset [HW] Reset the controller during init and cleanup
834 i8042.unlock [HW] Unlock (ignore) the keylock
836 i810= [HW,DRM]
838 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
839 indicates that the driver is running on unsupported
840 hardware.
841 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
842 does not match list of supported models.
843 i8k.power_status
844 [HW] Report power status in /proc/i8k
845 (disabled by default)
846 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
847 capability is set.
849 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
850 See Documentation/mca.txt.
852 icn= [HW,ISDN]
853 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
855 ide= [HW] (E)IDE subsystem
856 Format: ide=nodma or ide=doubler
857 See Documentation/ide/ide.txt.
859 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
860 See Documentation/ide/ide.txt.
862 idle= [X86]
863 Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
864 Poll forces a polling idle loop that can slightly improves the performance
865 of waking up a idle CPU, but will use a lot of power and make the system
866 run hot. Not recommended.
867 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
868 to not use it because it doesn't save as much power as a normal idle
869 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
870 as idle=poll.
871 idle=halt. Halt is forced to be used for CPU idle.
872 In such case C2/C3 won't be used again.
873 idle=nomwait. Disable mwait for CPU C-states
875 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
876 Claim all unknown PCI IDE storage controllers.
878 ignore_loglevel [KNL]
879 Ignore loglevel setting - this will print /all/
880 kernel messages to the console. Useful for debugging.
882 ihash_entries= [KNL]
883 Set number of hash buckets for inode cache.
885 in2000= [HW,SCSI]
886 See header of drivers/scsi/in2000.c.
888 init= [KNL]
889 Format: <full_path>
890 Run specified binary instead of /sbin/init as init
891 process.
893 initcall_debug [KNL] Trace initcalls as they are executed. Useful
894 for working out where the kernel is dying during
895 startup.
897 initrd= [BOOT] Specify the location of the initial ramdisk
899 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
900 Format: <irq>
902 inttest= [IA64]
904 iommu= [x86]
905 off
906 force
907 noforce
908 biomerge
909 panic
910 nopanic
911 merge
912 nomerge
913 forcesac
914 soft
917 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
918 off
919 Disable intel iommu driver.
920 igfx_off [Default Off]
921 By default, gfx is mapped as normal device. If a gfx
922 device has a dedicated DMAR unit, the DMAR unit is
923 bypassed by not enabling DMAR with this option. In
924 this case, gfx device will use physical address for
925 DMA.
926 forcedac [x86_64]
927 With this option iommu will not optimize to look
928 for io virtual address below 32 bit forcing dual
929 address cycle on pci bus for cards supporting greater
930 than 32 bit addressing. The default is to look
931 for translation below 32 bit and if not available
932 then look in the higher range.
933 strict [Default Off]
934 With this option on every unmap_single operation will
935 result in a hardware IOTLB flush operation as opposed
936 to batching them for performance.
938 io_delay= [X86-32,X86-64] I/O delay method
939 0x80
940 Standard port 0x80 based delay
941 0xed
942 Alternate port 0xed based delay (needed on some systems)
943 udelay
944 Simple two microseconds delay
945 none
946 No delay
948 io7= [HW] IO7 for Marvel based alpha systems
949 See comment before marvel_specify_io7 in
950 arch/alpha/kernel/core_marvel.c.
952 ip= [IP_PNP]
953 See Documentation/filesystems/nfsroot.txt.
955 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
956 See comment before ip2_setup() in
957 drivers/char/ip2/ip2base.c.
959 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
960 See header of drivers/scsi/ips.c.
962 ports= [IP_VS_FTP] IPVS ftp helper module
963 Default is 21.
964 Up to 8 (IP_VS_APP_MAX_PORTS) ports
965 may be specified.
966 Format: <port>,<port>....
968 irqfixup [HW]
969 When an interrupt is not handled search all handlers
970 for it. Intended to get systems with badly broken
971 firmware running.
973 irqpoll [HW]
974 When an interrupt is not handled search all handlers
975 for it. Also check all handlers each timer
976 interrupt. Intended to get systems with badly broken
977 firmware running.
979 isapnp= [ISAPNP]
980 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
982 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
983 Format:
984 <cpu number>,...,<cpu number>
985 or
986 <cpu number>-<cpu number> (must be a positive range in ascending order)
987 or a mixture
988 <cpu number>,...,<cpu number>-<cpu number>
989 This option can be used to specify one or more CPUs
990 to isolate from the general SMP balancing and scheduling
991 algorithms. The only way to move a process onto or off
992 an "isolated" CPU is via the CPU affinity syscalls.
993 <cpu number> begins at 0 and the maximum value is
994 "number of CPUs in system - 1".
996 This option is the preferred way to isolate CPUs. The
997 alternative -- manually setting the CPU mask of all
998 tasks in the system -- can cause problems and
999 suboptimal load balancer performance.
1001 iucv= [HW,NET]
1003 js= [HW,JOY] Analog joystick
1004 See Documentation/input/joystick.txt.
1006 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1007 specifies the amount of memory usable by the kernel
1008 for non-movable allocations. The requested amount is
1009 spread evenly throughout all nodes in the system. The
1010 remaining memory in each node is used for Movable
1011 pages. In the event, a node is too small to have both
1012 kernelcore and Movable pages, kernelcore pages will
1013 take priority and other nodes will have a larger number
1014 of kernelcore pages. The Movable zone is used for the
1015 allocation of pages that may be reclaimed or moved
1016 by the page migration subsystem. This means that
1017 HugeTLB pages may not be allocated from this zone.
1018 Note that allocations like PTEs-from-HighMem still
1019 use the HighMem zone if it exists, and the Normal
1020 zone if it does not.
1022 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1023 is similar to kernelcore except it specifies the
1024 amount of memory used for migratable allocations.
1025 If both kernelcore and movablecore is specified,
1026 then kernelcore will be at *least* the specified
1027 value but may be more. If movablecore on its own
1028 is specified, the administrator must be careful
1029 that the amount of memory usable for all allocations
1030 is not too small.
1032 keepinitrd [HW,ARM]
1034 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1035 in oops dumps.
1037 kgdboc= [HW] kgdb over consoles.
1038 Requires a tty driver that supports console polling.
1039 (only serial suported for now)
1040 Format: <serial_device>[,baud]
1042 l2cr= [PPC]
1044 l3cr= [PPC]
1046 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1047 disabled it.
1049 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
1050 C2 power state.
1052 libata.dma= [LIBATA] DMA control
1053 libata.dma=0 Disable all PATA and SATA DMA
1054 libata.dma=1 PATA and SATA Disk DMA only
1055 libata.dma=2 ATAPI (CDROM) DMA only
1056 libata.dma=4 Compact Flash DMA only
1057 Combinations also work, so libata.dma=3 enables DMA
1058 for disks and CDROMs, but not CFs.
1060 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1061 when set.
1062 Format: <int>
1064 libata.force= [LIBATA] Force configurations. The format is comma
1065 separated list of "[ID:]VAL" where ID is
1066 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1067 matching port, link or device. Basically, it matches
1068 the ATA ID string printed on console by libata. If
1069 the whole ID part is omitted, the last PORT and DEVICE
1070 values are used. If ID hasn't been specified yet, the
1071 configuration applies to all ports, links and devices.
1073 If only DEVICE is omitted, the parameter applies to
1074 the port and all links and devices behind it. DEVICE
1075 number of 0 either selects the first device or the
1076 first fan-out link behind PMP device. It does not
1077 select the host link. DEVICE number of 15 selects the
1078 host link and device attached to it.
1080 The VAL specifies the configuration to force. As long
1081 as there's no ambiguity shortcut notation is allowed.
1082 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1083 The following configurations can be forced.
1085 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1086 Any ID with matching PORT is used.
1088 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1090 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1091 udma[/][16,25,33,44,66,100,133] notation is also
1092 allowed.
1094 * [no]ncq: Turn on or off NCQ.
1096 * nohrst, nosrst, norst: suppress hard, soft
1097 and both resets.
1099 If there are multiple matching configurations changing
1100 the same attribute, the last one is used.
1102 load_ramdisk= [RAM] List of ramdisks to load from floppy
1103 See Documentation/ramdisk.txt.
1105 lockd.nlm_grace_period=P [NFS] Assign grace period.
1106 Format: <integer>
1108 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1109 Format: <integer>
1111 lockd.nlm_timeout=T [NFS] Assign timeout value.
1112 Format: <integer>
1114 lockd.nlm_udpport=M [NFS] Assign UDP port.
1115 Format: <integer>
1117 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1118 Format: <irq>
1120 loglevel= All Kernel Messages with a loglevel smaller than the
1121 console loglevel will be printed to the console. It can
1122 also be changed with klogd or other programs. The
1123 loglevels are defined as follows:
1125 0 (KERN_EMERG) system is unusable
1126 1 (KERN_ALERT) action must be taken immediately
1127 2 (KERN_CRIT) critical conditions
1128 3 (KERN_ERR) error conditions
1129 4 (KERN_WARNING) warning conditions
1130 5 (KERN_NOTICE) normal but significant condition
1131 6 (KERN_INFO) informational
1132 7 (KERN_DEBUG) debug-level messages
1134 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1135 Format: { n | nk | nM }
1136 n must be a power of two. The default size
1137 is set in the kernel config file.
1139 logo.nologo [FB] Disables display of the built-in Linux logo.
1140 This may be used to provide more screen space for
1141 kernel log messages and is useful when debugging
1142 kernel boot problems.
1144 lp=0 [LP] Specify parallel ports to use, e.g,
1145 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1146 lp=reset first parallel port). 'lp=0' disables the
1147 lp=auto printer driver. 'lp=reset' (which can be
1148 specified in addition to the ports) causes
1149 attached printers to be reset. Using
1150 lp=port1,port2,... specifies the parallel ports
1151 to associate lp devices with, starting with
1152 lp0. A port specification may be 'none' to skip
1153 that lp device, or a parport name such as
1154 'parport0'. Specifying 'lp=auto' instead of a
1155 port specification list means that device IDs
1156 from each port should be examined, to see if
1157 an IEEE 1284-compliant printer is attached; if
1158 so, the driver will manage that printer.
1159 See also header of drivers/char/lp.c.
1161 lpj=n [KNL]
1162 Sets loops_per_jiffy to given constant, thus avoiding
1163 time-consuming boot-time autodetection (up to 250 ms per
1164 CPU). 0 enables autodetection (default). To determine
1165 the correct value for your kernel, boot with normal
1166 autodetection and see what value is printed. Note that
1167 on SMP systems the preset will be applied to all CPUs,
1168 which is likely to cause problems if your CPUs need
1169 significantly divergent settings. An incorrect value
1170 will cause delays in the kernel to be wrong, leading to
1171 unpredictable I/O errors and other breakage. Although
1172 unlikely, in the extreme case this might damage your
1173 hardware.
1175 ltpc= [NET]
1176 Format: <io>,<irq>,<dma>
1178 mac5380= [HW,SCSI] Format:
1179 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1181 machvec= [IA64] Force the use of a particular machine-vector
1182 (machvec) in a generic kernel.
1183 Example: machvec=hpzx1_swiotlb
1185 max_loop= [LOOP] Maximum number of loopback devices that can
1186 be mounted
1187 Format: <1-256>
1189 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1190 should make use of. maxcpus=n : n >= 0 limits the
1191 kernel to using 'n' processors. n=0 is a special case,
1192 it is equivalent to "nosmp", which also disables
1193 the IO APIC.
1195 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1196 equal to this physical address is ignored.
1198 max_luns= [SCSI] Maximum number of LUNs to probe.
1199 Should be between 1 and 2^32-1.
1201 max_report_luns=
1202 [SCSI] Maximum number of LUNs received.
1203 Should be between 1 and 16384.
1205 mcatest= [IA-64]
1207 mce [X86-32] Machine Check Exception
1209 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1211 md= [HW] RAID subsystems devices and level
1212 See Documentation/md.txt.
1214 mdacon= [MDA]
1215 Format: <first>,<last>
1216 Specifies range of consoles to be captured by the MDA.
1218 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1219 Amount of memory to be used when the kernel is not able
1220 to see the whole system memory or for test.
1221 [X86-32] Use together with memmap= to avoid physical
1222 address space collisions. Without memmap= PCI devices
1223 could be placed at addresses belonging to unused RAM.
1225 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1226 memory.
1228 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1229 E820 memory map, as specified by the user.
1230 Such memmap=exactmap lines can be constructed based on
1231 BIOS output or other requirements. See the memmap=nn@ss
1232 option description.
1234 memmap=nn[KMG]@ss[KMG]
1235 [KNL] Force usage of a specific region of memory
1236 Region of memory to be used, from ss to ss+nn.
1238 memmap=nn[KMG]#ss[KMG]
1239 [KNL,ACPI] Mark specific memory as ACPI data.
1240 Region of memory to be used, from ss to ss+nn.
1242 memmap=nn[KMG]$ss[KMG]
1243 [KNL,ACPI] Mark specific memory as reserved.
1244 Region of memory to be used, from ss to ss+nn.
1245 Example: Exclude memory from 0x18690000-0x1869ffff
1246 memmap=64K$0x18690000
1247 or
1248 memmap=0x10000$0x18690000
1250 memtest= [KNL,X86] Enable memtest
1251 Format: <integer>
1252 range: 0,4 : pattern number
1253 default : 0 <disable>
1255 meye.*= [HW] Set MotionEye Camera parameters
1256 See Documentation/video4linux/meye.txt.
1258 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1259 Multi-Function General Purpose Timers on AMD Geode
1260 platforms.
1262 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1263 the BIOS has incorrectly applied a workaround. TinyBIOS
1264 version 0.98 is known to be affected, 0.99 fixes the
1265 problem by letting the user disable the workaround.
1267 mga= [HW,DRM]
1269 mminit_loglevel=
1270 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1271 parameter allows control of the logging verbosity for
1272 the additional memory initialisation checks. A value
1273 of 0 disables mminit logging and a level of 4 will
1274 log everything. Information is printed at KERN_DEBUG
1275 so loglevel=8 may also need to be specified.
1277 mousedev.tap_time=
1278 [MOUSE] Maximum time between finger touching and
1279 leaving touchpad surface for touch to be considered
1280 a tap and be reported as a left button click (for
1281 touchpads working in absolute mode only).
1282 Format: <msecs>
1283 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1284 reporting absolute coordinates, such as tablets
1285 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1286 reporting absolute coordinates, such as tablets
1288 mpu401= [HW,OSS]
1289 Format: <io>,<irq>
1291 MTD_Partition= [MTD]
1292 Format: <name>,<region-number>,<size>,<offset>
1294 MTD_Region= [MTD] Format:
1295 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1297 mtdparts= [MTD]
1298 See drivers/mtd/cmdlinepart.c.
1300 mtdset= [ARM]
1301 ARM/S3C2412 JIVE boot control
1303 See arch/arm/mach-s3c2412/mach-jive.c
1305 mtouchusb.raw_coordinates=
1306 [HW] Make the MicroTouch USB driver use raw coordinates
1307 ('y', default) or cooked coordinates ('n')
1309 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1311 NCR_D700= [HW,SCSI]
1312 See header of drivers/scsi/NCR_D700.c.
1314 ncr5380= [HW,SCSI]
1316 ncr53c400= [HW,SCSI]
1318 ncr53c400a= [HW,SCSI]
1320 ncr53c406a= [HW,SCSI]
1322 ncr53c8xx= [HW,SCSI]
1324 netdev= [NET] Network devices parameters
1325 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1326 Note that mem_start is often overloaded to mean
1327 something different and driver-specific.
1328 This usage is only documented in each driver source
1329 file if at all.
1331 nf_conntrack.acct=
1332 [NETFILTER] Enable connection tracking flow accounting
1333 0 to disable accounting
1334 1 to enable accounting
1335 Default value depends on CONFIG_NF_CT_ACCT that is
1336 going to be removed in 2.6.29.
1338 nfsaddrs= [NFS]
1339 See Documentation/filesystems/nfsroot.txt.
1341 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1342 See Documentation/filesystems/nfsroot.txt.
1344 nfs.callback_tcpport=
1345 [NFS] set the TCP port on which the NFSv4 callback
1346 channel should listen.
1348 nfs.idmap_cache_timeout=
1349 [NFS] set the maximum lifetime for idmapper cache
1350 entries.
1352 nfs.enable_ino64=
1353 [NFS] enable 64-bit inode numbers.
1354 If zero, the NFS client will fake up a 32-bit inode
1355 number for the readdir() and stat() syscalls instead
1356 of returning the full 64-bit number.
1357 The default is to return 64-bit inode numbers.
1359 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1360 when a NMI is triggered.
1361 Format: [state][,regs][,debounce][,die]
1363 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1365 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1366 emulation library even if a 387 maths coprocessor
1367 is present.
1369 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1370 caches in the slab allocator. Saves per-node memory,
1371 but will impact performance.
1373 noalign [KNL,ARM]
1375 noapic [SMP,APIC] Tells the kernel to not make use of any
1376 IOAPICs that may be present in the system.
1378 nobats [PPC] Do not use BATs for mapping kernel lowmem
1379 on "Classic" PPC cores.
1381 nocache [ARM]
1383 nodelayacct [KNL] Disable per-task delay accounting
1385 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1387 noefi [X86-32,X86-64] Disable EFI runtime services support.
1389 noexec [IA-64]
1391 noexec [X86-32,X86-64]
1392 On X86-32 available only on PAE configured kernels.
1393 noexec=on: enable non-executable mappings (default)
1394 noexec=off: disable non-executable mappings
1396 noexec32 [X86-64]
1397 This affects only 32-bit executables.
1398 noexec32=on: enable non-executable mappings (default)
1399 read doesn't imply executable mappings
1400 noexec32=off: disable non-executable mappings
1401 read implies executable mappings
1403 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1404 register save and restore. The kernel will only save
1405 legacy floating-point registers on task switch.
1407 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1409 nohlt [BUGS=ARM]
1411 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1412 instruction doesn't work correctly and not to
1413 use it.
1415 nohalt [IA-64] Tells the kernel not to use the power saving
1416 function PAL_HALT_LIGHT when idle. This increases
1417 power-consumption. On the positive side, it reduces
1418 interrupt wake-up latency, which may improve performance
1419 in certain environments such as networked servers or
1420 real-time systems.
1422 nohz= [KNL] Boottime enable/disable dynamic ticks
1423 Valid arguments: on, off
1424 Default: on
1426 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1428 noirqdebug [X86-32] Disables the code which attempts to detect and
1429 disable unhandled interrupt sources.
1431 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1432 broken timer IRQ sources.
1434 noisapnp [ISAPNP] Disables ISA PnP code.
1436 noinitrd [RAM] Tells the kernel not to load any configured
1437 initial RAM disk.
1439 nointroute [IA-64]
1441 nojitter [IA64] Disables jitter checking for ITC timers.
1443 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1445 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1447 noltlbs [PPC] Do not use large page/tlb entries for kernel
1448 lowmem mapping on PPC40x.
1450 nomca [IA-64] Disable machine check abort handling
1452 nomce [X86-32] Machine Check Exception
1454 nomfgpt [X86-32] Disable Multi-Function General Purpose
1455 Timer usage (for AMD Geode machines).
1457 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1459 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1460 with UP alternatives
1462 noresidual [PPC] Don't use residual data on PReP machines.
1464 noresume [SWSUSP] Disables resume and restores original swap
1465 space.
1467 no-scroll [VGA] Disables scrollback.
1468 This is required for the Braillex ib80-piezo Braille
1469 reader made by F.H. Papenmeier (Germany).
1471 nosbagart [IA-64]
1473 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1475 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1476 and disable the IO APIC. legacy for "maxcpus=0".
1478 nosoftlockup [KNL] Disable the soft-lockup detector.
1480 nosync [HW,M68K] Disables sync negotiation for all devices.
1482 notsc [BUGS=X86-32] Disable Time Stamp Counter
1484 nousb [USB] Disable the USB subsystem
1486 nowb [ARM]
1488 nptcg= [IA64] Override max number of concurrent global TLB
1489 purges which is reported from either PAL_VM_SUMMARY or
1490 SAL PALO.
1492 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1493 one of ['zone', 'node', 'default'] can be specified
1494 This can be set from sysctl after boot.
1495 See Documentation/sysctl/vm.txt for details.
1497 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1499 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1500 Rather than timing out after 20 ms if an EC
1501 command is not properly ACKed, override the length
1502 of the timeout. We have interrupts disabled while
1503 waiting for the ACK, so if this is set too high
1504 interrupts *may* be lost!
1506 opl3= [HW,OSS]
1507 Format: <io>
1509 oprofile.timer= [HW]
1510 Use timer interrupt instead of performance counters
1512 osst= [HW,SCSI] SCSI Tape Driver
1513 Format: <buffer_size>,<write_threshold>
1514 See also Documentation/scsi/st.txt.
1516 panic= [KNL] Kernel behaviour on panic
1517 Format: <timeout>
1519 parkbd.port= [HW] Parallel port number the keyboard adapter is
1520 connected to, default is 0.
1521 Format: <parport#>
1522 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1523 0 for XT, 1 for AT (default is AT).
1524 Format: <mode>
1526 parport= [HW,PPT] Specify parallel ports. 0 disables.
1527 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1528 Use 'auto' to force the driver to use any
1529 IRQ/DMA settings detected (the default is to
1530 ignore detected IRQ/DMA settings because of
1531 possible conflicts). You can specify the base
1532 address, IRQ, and DMA settings; IRQ and DMA
1533 should be numbers, or 'auto' (for using detected
1534 settings on that particular port), or 'nofifo'
1535 (to avoid using a FIFO even if it is detected).
1536 Parallel ports are assigned in the order they
1537 are specified on the command line, starting
1538 with parport0.
1540 parport_init_mode= [HW,PPT]
1541 Configure VIA parallel port to operate in
1542 a specific mode. This is necessary on Pegasos
1543 computer where firmware has no options for setting
1544 up parallel port mode and sets it to spp.
1545 Currently this function knows 686a and 8231 chips.
1546 Format: [spp|ps2|epp|ecp|ecpepp]
1548 pas2= [HW,OSS] Format:
1549 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1551 pas16= [HW,SCSI]
1552 See header of drivers/scsi/pas16.c.
1554 pause_on_oops=
1555 Halt all CPUs after the first oops has been printed for
1556 the specified number of seconds. This is to be used if
1557 your oopses keep scrolling off the screen.
1559 pcbit= [HW,ISDN]
1561 pcd. [PARIDE]
1562 See header of drivers/block/paride/pcd.c.
1563 See also Documentation/paride.txt.
1565 pci=option[,option...] [PCI] various PCI subsystem options:
1566 off [X86-32] don't probe for the PCI bus
1567 bios [X86-32] force use of PCI BIOS, don't access
1568 the hardware directly. Use this if your machine
1569 has a non-standard PCI host bridge.
1570 nobios [X86-32] disallow use of PCI BIOS, only direct
1571 hardware access methods are allowed. Use this
1572 if you experience crashes upon bootup and you
1573 suspect they are caused by the BIOS.
1574 conf1 [X86-32] Force use of PCI Configuration
1575 Mechanism 1.
1576 conf2 [X86-32] Force use of PCI Configuration
1577 Mechanism 2.
1578 noaer [PCIE] If the PCIEAER kernel config parameter is
1579 enabled, this kernel boot option can be used to
1580 disable the use of PCIE advanced error reporting.
1581 nodomains [PCI] Disable support for multiple PCI
1582 root domains (aka PCI segments, in ACPI-speak).
1583 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1584 Configuration
1585 nomsi [MSI] If the PCI_MSI kernel config parameter is
1586 enabled, this kernel boot option can be used to
1587 disable the use of MSI interrupts system-wide.
1588 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1589 routing table. These calls are known to be buggy
1590 on several machines and they hang the machine
1591 when used, but on other computers it's the only
1592 way to get the interrupt routing table. Try
1593 this option if the kernel is unable to allocate
1594 IRQs or discover secondary PCI buses on your
1595 motherboard.
1596 rom [X86-32] Assign address space to expansion ROMs.
1597 Use with caution as certain devices share
1598 address decoders between ROMs and other
1599 resources.
1600 norom [X86-32,X86_64] Do not assign address space to
1601 expansion ROMs that do not already have
1602 BIOS assigned address ranges.
1603 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1604 assigned automatically to PCI devices. You can
1605 make the kernel exclude IRQs of your ISA cards
1606 this way.
1607 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1608 of the PIRQ table (normally generated
1609 by the BIOS) if it is outside the
1610 F0000h-100000h range.
1611 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1612 useful if the kernel is unable to find your
1613 secondary buses and you want to tell it
1614 explicitly which ones they are.
1615 assign-busses [X86-32] Always assign all PCI bus
1616 numbers ourselves, overriding
1617 whatever the firmware may have done.
1618 usepirqmask [X86-32] Honor the possible IRQ mask stored
1619 in the BIOS $PIR table. This is needed on
1620 some systems with broken BIOSes, notably
1621 some HP Pavilion N5400 and Omnibook XE3
1622 notebooks. This will have no effect if ACPI
1623 IRQ routing is enabled.
1624 noacpi [X86-32] Do not use ACPI for IRQ routing
1625 or for PCI scanning.
1626 use_crs [X86-32] Use _CRS for PCI resource
1627 allocation.
1628 routeirq Do IRQ routing for all PCI devices.
1629 This is normally done in pci_enable_device(),
1630 so this option is a temporary workaround
1631 for broken drivers that don't call it.
1632 skip_isa_align [X86] do not align io start addr, so can
1633 handle more pci cards
1634 firmware [ARM] Do not re-enumerate the bus but instead
1635 just use the configuration from the
1636 bootloader. This is currently used on
1637 IXP2000 systems where the bus has to be
1638 configured a certain way for adjunct CPUs.
1639 noearly [X86] Don't do any early type 1 scanning.
1640 This might help on some broken boards which
1641 machine check when some devices' config space
1642 is read. But various workarounds are disabled
1643 and some IOMMU drivers will not work.
1644 bfsort Sort PCI devices into breadth-first order.
1645 This sorting is done to get a device
1646 order compatible with older (<= 2.4) kernels.
1647 nobfsort Don't sort PCI devices into breadth-first order.
1648 cbiosize=nn[KMG] The fixed amount of bus space which is
1649 reserved for the CardBus bridge's IO window.
1650 The default value is 256 bytes.
1651 cbmemsize=nn[KMG] The fixed amount of bus space which is
1652 reserved for the CardBus bridge's memory
1653 window. The default value is 64 megabytes.
1655 pcmv= [HW,PCMCIA] BadgePAD 4
1657 pd. [PARIDE]
1658 See Documentation/paride.txt.
1660 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1661 boot time.
1662 Format: { 0 | 1 }
1663 See arch/parisc/kernel/pdc_chassis.c
1665 pf. [PARIDE]
1666 See Documentation/paride.txt.
1668 pg. [PARIDE]
1669 See Documentation/paride.txt.
1671 pirq= [SMP,APIC] Manual mp-table setup
1672 See Documentation/i386/IO-APIC.txt.
1674 plip= [PPT,NET] Parallel port network link
1675 Format: { parport<nr> | timid | 0 }
1676 See also Documentation/parport.txt.
1678 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1679 Override pmtimer IOPort with a hex value.
1680 e.g. pmtmr=0x508
1682 pnpacpi= [ACPI]
1683 { off }
1685 pnpbios= [ISAPNP]
1686 { on | off | curr | res | no-curr | no-res }
1688 pnp_reserve_irq=
1689 [ISAPNP] Exclude IRQs for the autoconfiguration
1691 pnp_reserve_dma=
1692 [ISAPNP] Exclude DMAs for the autoconfiguration
1694 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1695 Ranges are in pairs (I/O port base and size).
1697 pnp_reserve_mem=
1698 [ISAPNP] Exclude memory regions for the
1699 autoconfiguration.
1700 Ranges are in pairs (memory base and size).
1702 print-fatal-signals=
1703 [KNL] debug: print fatal signals
1704 print-fatal-signals=1: print segfault info to
1705 the kernel console.
1706 default: off.
1708 printk.time= Show timing data prefixed to each printk message line
1709 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1711 profile= [KNL] Enable kernel profiling via /proc/profile
1712 Format: [schedule,]<number>
1713 Param: "schedule" - profile schedule points.
1714 Param: <number> - step/bucket size as a power of 2 for
1715 statistical time based profiling.
1716 Param: "sleep" - profile D-state sleeping (millisecs).
1717 Requires CONFIG_SCHEDSTATS
1718 Param: "kvm" - profile VM exits.
1720 processor.max_cstate= [HW,ACPI]
1721 Limit processor to maximum C-state
1722 max_cstate=9 overrides any DMI blacklist limit.
1724 processor.nocst [HW,ACPI]
1725 Ignore the _CST method to determine C-states,
1726 instead using the legacy FADT method
1728 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1729 before loading.
1730 See Documentation/ramdisk.txt.
1732 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1733 probe for; one of (bare|imps|exps|lifebook|any).
1734 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1735 per second.
1736 psmouse.resetafter= [HW,MOUSE]
1737 Try to reset the device after so many bad packets
1738 (0 = never).
1739 psmouse.resolution=
1740 [HW,MOUSE] Set desired mouse resolution, in dpi.
1741 psmouse.smartscroll=
1742 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1743 0 = disabled, 1 = enabled (default).
1745 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1746 Format:
1747 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1749 pt. [PARIDE]
1750 See Documentation/paride.txt.
1752 pty.legacy_count=
1753 [KNL] Number of legacy pty's. Overwrites compiled-in
1754 default number.
1756 quiet [KNL] Disable most log messages
1758 r128= [HW,DRM]
1760 raid= [HW,RAID]
1761 See Documentation/md.txt.
1763 ramdisk_blocksize= [RAM]
1764 See Documentation/ramdisk.txt.
1766 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1767 See Documentation/ramdisk.txt.
1769 rcupdate.blimit= [KNL,BOOT]
1770 Set maximum number of finished RCU callbacks to process
1771 in one batch.
1773 rcupdate.qhimark= [KNL,BOOT]
1774 Set threshold of queued
1775 RCU callbacks over which batch limiting is disabled.
1777 rcupdate.qlowmark= [KNL,BOOT]
1778 Set threshold of queued RCU callbacks below which
1779 batch limiting is re-enabled.
1781 rdinit= [KNL]
1782 Format: <full_path>
1783 Run specified binary instead of /init from the ramdisk,
1784 used for early userspace startup. See initrd.
1786 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1787 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1788 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1790 relax_domain_level=
1791 [KNL, SMP] Set scheduler's default relax_domain_level.
1792 See Documentation/cpusets.txt.
1794 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1796 reservetop= [X86-32]
1797 Format: nn[KMG]
1798 Reserves a hole at the top of the kernel virtual
1799 address space.
1801 reset_devices [KNL] Force drivers to reset the underlying device
1802 during initialization.
1804 resume= [SWSUSP]
1805 Specify the partition device for software suspend
1807 resume_offset= [SWSUSP]
1808 Specify the offset from the beginning of the partition
1809 given by "resume=" at which the swap header is located,
1810 in <PAGE_SIZE> units (needed only for swap files).
1811 See Documentation/power/swsusp-and-swap-files.txt
1813 retain_initrd [RAM] Keep initrd memory after extraction
1815 rhash_entries= [KNL,NET]
1816 Set number of hash buckets for route cache
1818 riscom8= [HW,SERIAL]
1819 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1821 ro [KNL] Mount root device read-only on boot
1823 root= [KNL] Root filesystem
1825 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1826 mount the root filesystem
1828 rootflags= [KNL] Set root filesystem mount option string
1830 rootfstype= [KNL] Set root filesystem type
1832 rootwait [KNL] Wait (indefinitely) for root device to show up.
1833 Useful for devices that are detected asynchronously
1834 (e.g. USB and MMC devices).
1836 root_plug.vendor_id=
1837 [ROOTPLUG] Override the default vendor ID
1839 root_plug.product_id=
1840 [ROOTPLUG] Override the default product ID
1842 root_plug.debug=
1843 [ROOTPLUG] Enable debugging output
1845 rw [KNL] Mount root device read-write on boot
1847 S [KNL] Run init in single mode
1849 sa1100ir [NET]
1850 See drivers/net/irda/sa1100_ir.c.
1852 sbni= [NET] Granch SBNI12 leased line adapter
1854 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1855 Format: <io>[,<timeout>[,<isapnp>]]
1857 scsi_debug_*= [SCSI]
1858 See drivers/scsi/scsi_debug.c.
1860 scsi_default_dev_flags=
1861 [SCSI] SCSI default device flags
1862 Format: <integer>
1864 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1865 Format: <vendor>:<model>:<flags>
1866 (flags are integer value)
1868 scsi_logging_level= [SCSI] a bit mask of logging levels
1869 See drivers/scsi/scsi_logging.h for bits. Also
1870 settable via sysctl at dev.scsi.logging_level
1871 (/proc/sys/dev/scsi/logging_level).
1872 There is also a nice 'scsi_logging_level' script in the
1873 S390-tools package, available for download at
1874 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1876 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1877 discovered. async scans them in kernel threads,
1878 allowing boot to proceed. none ignores them, expecting
1879 user space to do the scan.
1881 selinux [SELINUX] Disable or enable SELinux at boot time.
1882 Format: { "0" | "1" }
1883 See security/selinux/Kconfig help text.
1884 0 -- disable.
1885 1 -- enable.
1886 Default value is set via kernel config option.
1887 If enabled at boot time, /selinux/disable can be used
1888 later to disable prior to initial policy load.
1890 selinux_compat_net =
1891 [SELINUX] Set initial selinux_compat_net flag value.
1892 Format: { "0" | "1" }
1893 0 -- use new secmark-based packet controls
1894 1 -- use legacy packet controls
1895 Default value is 0 (preferred).
1896 Value can be changed at runtime via
1897 /selinux/compat_net.
1899 serialnumber [BUGS=X86-32]
1901 shapers= [NET]
1902 Maximal number of shapers.
1904 sim710= [SCSI,HW]
1905 See header of drivers/scsi/sim710.c.
1907 simeth= [IA-64]
1908 simscsi=
1910 slram= [HW,MTD]
1912 slub_debug[=options[,slabs]] [MM, SLUB]
1913 Enabling slub_debug allows one to determine the
1914 culprit if slab objects become corrupted. Enabling
1915 slub_debug can create guard zones around objects and
1916 may poison objects when not in use. Also tracks the
1917 last alloc / free. For more information see
1918 Documentation/vm/slub.txt.
1920 slub_max_order= [MM, SLUB]
1921 Determines the maximum allowed order for slabs.
1922 A high setting may cause OOMs due to memory
1923 fragmentation. For more information see
1924 Documentation/vm/slub.txt.
1926 slub_min_objects= [MM, SLUB]
1927 The minimum number of objects per slab. SLUB will
1928 increase the slab order up to slub_max_order to
1929 generate a sufficiently large slab able to contain
1930 the number of objects indicated. The higher the number
1931 of objects the smaller the overhead of tracking slabs
1932 and the less frequently locks need to be acquired.
1933 For more information see Documentation/vm/slub.txt.
1935 slub_min_order= [MM, SLUB]
1936 Determines the mininum page order for slabs. Must be
1937 lower than slub_max_order.
1938 For more information see Documentation/vm/slub.txt.
1940 slub_nomerge [MM, SLUB]
1941 Disable merging of slabs with similar size. May be
1942 necessary if there is some reason to distinguish
1943 allocs to different slabs. Debug options disable
1944 merging on their own.
1945 For more information see Documentation/vm/slub.txt.
1947 smart2= [HW]
1948 Format: <io1>[,<io2>[,...,<io8>]]
1950 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1951 attempt to substitute SMP alternatives once at boot.
1953 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1954 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1955 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1956 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1957 smsc-ircc2.ircc_irq= [HW] IRQ line
1958 smsc-ircc2.ircc_dma= [HW] DMA channel
1959 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1960 0: Toshiba Satellite 1800 (GP data pin select)
1961 1: Fast pin select (default)
1962 2: ATC IRMode
1964 snd-ad1816a= [HW,ALSA]
1966 snd-ad1848= [HW,ALSA]
1968 snd-ali5451= [HW,ALSA]
1970 snd-als100= [HW,ALSA]
1972 snd-als4000= [HW,ALSA]
1974 snd-azt2320= [HW,ALSA]
1976 snd-cmi8330= [HW,ALSA]
1978 snd-cmipci= [HW,ALSA]
1980 snd-cs4231= [HW,ALSA]
1982 snd-cs4232= [HW,ALSA]
1984 snd-cs4236= [HW,ALSA]
1986 snd-cs4281= [HW,ALSA]
1988 snd-cs46xx= [HW,ALSA]
1990 snd-dt019x= [HW,ALSA]
1992 snd-dummy= [HW,ALSA]
1994 snd-emu10k1= [HW,ALSA]
1996 snd-ens1370= [HW,ALSA]
1998 snd-ens1371= [HW,ALSA]
2000 snd-es968= [HW,ALSA]
2002 snd-es1688= [HW,ALSA]
2004 snd-es18xx= [HW,ALSA]
2006 snd-es1938= [HW,ALSA]
2008 snd-es1968= [HW,ALSA]
2010 snd-fm801= [HW,ALSA]
2012 snd-gusclassic= [HW,ALSA]
2014 snd-gusextreme= [HW,ALSA]
2016 snd-gusmax= [HW,ALSA]
2018 snd-hdsp= [HW,ALSA]
2020 snd-ice1712= [HW,ALSA]
2022 snd-intel8x0= [HW,ALSA]
2024 snd-interwave= [HW,ALSA]
2026 snd-interwave-stb=
2027 [HW,ALSA]
2029 snd-korg1212= [HW,ALSA]
2031 snd-maestro3= [HW,ALSA]
2033 snd-mpu401= [HW,ALSA]
2035 snd-mtpav= [HW,ALSA]
2037 snd-nm256= [HW,ALSA]
2039 snd-opl3sa2= [HW,ALSA]
2041 snd-opti92x-ad1848=
2042 [HW,ALSA]
2044 snd-opti92x-cs4231=
2045 [HW,ALSA]
2047 snd-opti93x= [HW,ALSA]
2049 snd-pmac= [HW,ALSA]
2051 snd-rme32= [HW,ALSA]
2053 snd-rme96= [HW,ALSA]
2055 snd-rme9652= [HW,ALSA]
2057 snd-sb8= [HW,ALSA]
2059 snd-sb16= [HW,ALSA]
2061 snd-sbawe= [HW,ALSA]
2063 snd-serial= [HW,ALSA]
2065 snd-sgalaxy= [HW,ALSA]
2067 snd-sonicvibes= [HW,ALSA]
2069 snd-sun-amd7930=
2070 [HW,ALSA]
2072 snd-sun-cs4231= [HW,ALSA]
2074 snd-trident= [HW,ALSA]
2076 snd-usb-audio= [HW,ALSA,USB]
2078 snd-via82xx= [HW,ALSA]
2080 snd-virmidi= [HW,ALSA]
2082 snd-wavefront= [HW,ALSA]
2084 snd-ymfpci= [HW,ALSA]
2086 softlockup_panic=
2087 [KNL] Should the soft-lockup detector generate panics.
2089 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2090 See Documentation/sonypi.txt
2092 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2093 See Documentation/specialix.txt.
2095 spia_io_base= [HW,MTD]
2096 spia_fio_base=
2097 spia_pedr=
2098 spia_peddr=
2100 sscape= [HW,OSS]
2101 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2103 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2104 See Documentation/scsi/st.txt.
2106 sti= [PARISC,HW]
2107 Format: <num>
2108 Set the STI (builtin display/keyboard on the HP-PARISC
2109 machines) console (graphic card) which should be used
2110 as the initial boot-console.
2111 See also comment in drivers/video/console/sticore.c.
2113 sti_font= [HW]
2114 See comment in drivers/video/console/sticore.c.
2116 stifb= [HW]
2117 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2119 sunrpc.pool_mode=
2120 [NFS]
2121 Control how the NFS server code allocates CPUs to
2122 service thread pools. Depending on how many NICs
2123 you have and where their interrupts are bound, this
2124 option will affect which CPUs will do NFS serving.
2125 Note: this parameter cannot be changed while the
2126 NFS server is running.
2128 auto the server chooses an appropriate mode
2129 automatically using heuristics
2130 global a single global pool contains all CPUs
2131 percpu one pool for each CPU
2132 pernode one pool for each NUMA node (equivalent
2133 to global on non-NUMA machines)
2135 swiotlb= [IA-64] Number of I/O TLB slabs
2137 switches= [HW,M68k]
2139 sym53c416= [HW,SCSI]
2140 See header of drivers/scsi/sym53c416.c.
2142 sysrq_always_enabled
2143 [KNL]
2144 Ignore sysrq setting - this boot parameter will
2145 neutralize any effect of /proc/sys/kernel/sysrq.
2146 Useful for debugging.
2148 t128= [HW,SCSI]
2149 See header of drivers/scsi/t128.c.
2151 tdfx= [HW,DRM]
2153 test_suspend= [SUSPEND]
2154 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2155 standby suspend) as the system sleep state to briefly
2156 enter during system startup. The system is woken from
2157 this state using a wakeup-capable RTC alarm.
2159 thash_entries= [KNL,NET]
2160 Set number of hash buckets for TCP connection
2162 thermal.act= [HW,ACPI]
2163 -1: disable all active trip points in all thermal zones
2164 <degrees C>: override all lowest active trip points
2166 thermal.crt= [HW,ACPI]
2167 -1: disable all critical trip points in all thermal zones
2168 <degrees C>: lower all critical trip points
2170 thermal.nocrt= [HW,ACPI]
2171 Set to disable actions on ACPI thermal zone
2172 critical and hot trip points.
2174 thermal.off= [HW,ACPI]
2175 1: disable ACPI thermal control
2177 thermal.psv= [HW,ACPI]
2178 -1: disable all passive trip points
2179 <degrees C>: override all passive trip points to this value
2181 thermal.tzp= [HW,ACPI]
2182 Specify global default ACPI thermal zone polling rate
2183 <deci-seconds>: poll all this frequency
2184 0: no polling (default)
2186 tmscsim= [HW,SCSI]
2187 See comment before function dc390_setup() in
2188 drivers/scsi/tmscsim.c.
2190 tp720= [HW,PS2]
2192 trix= [HW,OSS] MediaTrix AudioTrix Pro
2193 Format:
2194 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2196 turbografx.map[2|3]= [HW,JOY]
2197 TurboGraFX parallel port interface
2198 Format:
2199 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2200 See also Documentation/input/joystick-parport.txt
2202 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2203 See header of drivers/scsi/u14-34f.c.
2205 uart401= [HW,OSS]
2206 Format: <io>,<irq>
2208 uart6850= [HW,OSS]
2209 Format: <io>,<irq>
2211 uhci-hcd.ignore_oc=
2212 [USB] Ignore overcurrent events (default N).
2213 Some badly-designed motherboards generate lots of
2214 bogus events, for ports that aren't wired to
2215 anything. Set this parameter to avoid log spamming.
2216 Note that genuine overcurrent events won't be
2217 reported either.
2219 unknown_nmi_panic
2220 [X86-32,X86-64]
2221 Set unknown_nmi_panic=1 early on boot.
2223 usbcore.autosuspend=
2224 [USB] The autosuspend time delay (in seconds) used
2225 for newly-detected USB devices (default 2). This
2226 is the time required before an idle device will be
2227 autosuspended. Devices for which the delay is set
2228 to a negative value won't be autosuspended at all.
2230 usbhid.mousepoll=
2231 [USBHID] The interval which mice are to be polled at.
2233 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2234 kernel's map of available physical RAM.
2236 vdso= [X86-32,SH,x86-64]
2237 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2238 vdso=1: enable VDSO (default)
2239 vdso=0: disable VDSO mapping
2241 vdso32= [X86-32,X86-64]
2242 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2243 vdso32=1: enable 32-bit VDSO (default)
2244 vdso32=0: disable 32-bit VDSO mapping
2246 vector= [IA-64,SMP]
2247 vector=percpu: enable percpu vector domain
2249 video= [FB] Frame buffer configuration
2250 See Documentation/fb/modedb.txt.
2252 vga= [BOOT,X86-32] Select a particular video mode
2253 See Documentation/i386/boot.txt and
2254 Documentation/svga.txt.
2255 Use vga=ask for menu.
2256 This is actually a boot loader parameter; the value is
2257 passed to the kernel using a special protocol.
2259 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2260 size of <nn>. This can be used to increase the
2261 minimum size (128MB on x86). It can also be used to
2262 decrease the size and leave more room for directly
2263 mapped kernel RAM.
2265 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2266 Format: <command>
2268 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2269 Format: <command>
2271 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2272 Format: <command>
2274 waveartist= [HW,OSS]
2275 Format: <io>,<irq>,<dma>,<dma2>
2277 wd33c93= [HW,SCSI]
2278 See header of drivers/scsi/wd33c93.c.
2280 wd7000= [HW,SCSI]
2281 See header of drivers/scsi/wd7000.c.
2283 wdt= [WDT] Watchdog
2284 See Documentation/watchdog/wdt.txt.
2286 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2287 xd_geo= See header of drivers/block/xd.c.
2289 xirc2ps_cs= [NET,PCMCIA]
2290 Format:
2291 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2293 norandmaps Don't use address space randomization
2294 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2296 ______________________________________________________________________
2298 TODO:
2300 Add documentation for ALSA options.
2301 Add more DRM drivers.