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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 (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 1: enable, 0: disable. It is useful for boot time
221 debugging. After system has booted up, it can be set
222 via /sys/module/acpi/parameters/debug_level.
223 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
224 Available bits (add the numbers together) to enable different
225 debug output levels of the ACPI subsystem:
226 0x01 error 0x02 warn 0x04 init 0x08 debug object
227 0x10 info 0x20 init names 0x40 parse 0x80 load
228 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
229 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
230 0x10000 resources 0x20000 user requests 0x40000 package.
231 The number can be in decimal or prefixed with 0x in hex.
232 Warning: Many of these options can produce a lot of
233 output and make your system unusable. Be very careful.
235 acpi_pm_good [X86-32,X86-64]
236 Override the pmtimer bug detection: force the kernel
237 to assume that this machine's pmtimer latches its value
238 and always returns good values.
240 agp= [AGP]
241 { off | try_unsupported }
242 off: disable AGP support
243 try_unsupported: try to drive unsupported chipsets
244 (may crash computer or cause data corruption)
246 enable_timer_pin_1 [i386,x86-64]
247 Enable PIN 1 of APIC timer
248 Can be useful to work around chipset bugs
249 (in particular on some ATI chipsets).
250 The kernel tries to set a reasonable default.
252 disable_timer_pin_1 [i386,x86-64]
253 Disable PIN 1 of APIC timer
254 Can be useful to work around chipset bugs.
256 ad1848= [HW,OSS]
257 Format: <io>,<irq>,<dma>,<dma2>,<type>
259 advansys= [HW,SCSI]
260 See header of drivers/scsi/advansys.c.
262 advwdt= [HW,WDT] Advantech WDT
263 Format: <iostart>,<iostop>
265 aedsp16= [HW,OSS] Audio Excel DSP 16
266 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
267 See also header of sound/oss/aedsp16.c.
269 aha152x= [HW,SCSI]
270 See Documentation/scsi/aha152x.txt.
272 aha1542= [HW,SCSI]
273 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
275 aic7xxx= [HW,SCSI]
276 See Documentation/scsi/aic7xxx.txt.
278 aic79xx= [HW,SCSI]
279 See Documentation/scsi/aic79xx.txt.
281 amd_iommu= [HW,X86-84]
282 Pass parameters to the AMD IOMMU driver in the system.
283 Possible values are:
284 isolate - enable device isolation (each device, as far
285 as possible, will get its own protection
286 domain)
287 amd_iommu_size= [HW,X86-64]
288 Define the size of the aperture for the AMD IOMMU
289 driver. Possible values are:
290 '32M', '64M' (default), '128M', '256M', '512M', '1G'
292 amijoy.map= [HW,JOY] Amiga joystick support
293 Map of devices attached to JOY0DAT and JOY1DAT
294 Format: <a>,<b>
295 See also Documentation/kernel/input/joystick.txt
297 analog.map= [HW,JOY] Analog joystick and gamepad support
298 Specifies type or capabilities of an analog joystick
299 connected to one of 16 gameports
300 Format: <type1>,<type2>,..<type16>
302 apc= [HW,SPARC]
303 Power management functions (SPARCstation-4/5 + deriv.)
304 Format: noidle
305 Disable APC CPU standby support. SPARCstation-Fox does
306 not play well with APC CPU idle - disable it if you have
307 APC and your system crashes randomly.
309 apic= [APIC,i386] Advanced Programmable Interrupt Controller
310 Change the output verbosity whilst booting
311 Format: { quiet (default) | verbose | debug }
312 Change the amount of debugging information output
313 when initialising the APIC and IO-APIC components.
315 apm= [APM] Advanced Power Management
316 See header of arch/x86/kernel/apm_32.c.
318 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
319 Format: <io>,<irq>,<nodeID>
321 ataflop= [HW,M68k]
323 atarimouse= [HW,MOUSE] Atari Mouse
325 atascsi= [HW,SCSI] Atari SCSI
327 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
328 EzKey and similar keyboards
330 atkbd.reset= [HW] Reset keyboard during initialization
332 atkbd.set= [HW] Select keyboard code set
333 Format: <int> (2 = AT (default), 3 = PS/2)
335 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
336 keyboards
338 atkbd.softraw= [HW] Choose between synthetic and real raw mode
339 Format: <bool> (0 = real, 1 = synthetic (default))
341 atkbd.softrepeat= [HW]
342 Use software keyboard repeat
344 autotest [IA64]
346 baycom_epp= [HW,AX25]
347 Format: <io>,<mode>
349 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
350 Format: <io>,<mode>
351 See header of drivers/net/hamradio/baycom_par.c.
353 baycom_ser_fdx= [HW,AX25]
354 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
355 Format: <io>,<irq>,<mode>[,<baud>]
356 See header of drivers/net/hamradio/baycom_ser_fdx.c.
358 baycom_ser_hdx= [HW,AX25]
359 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
360 Format: <io>,<irq>,<mode>
361 See header of drivers/net/hamradio/baycom_ser_hdx.c.
363 boot_delay= Milliseconds to delay each printk during boot.
364 Values larger than 10 seconds (10000) are changed to
365 no delay (0).
366 Format: integer
368 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
369 bttv.radio= Most important insmod options are available as
370 kernel args too.
371 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
372 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
374 BusLogic= [HW,SCSI]
375 See drivers/scsi/BusLogic.c, comment before function
376 BusLogic_ParseDriverOptions().
378 c101= [NET] Moxa C101 synchronous serial card
380 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
381 Sometimes CPU hardware bugs make them report the cache
382 size incorrectly. The kernel will attempt work arounds
383 to fix known problems, but for some CPUs it is not
384 possible to determine what the correct size should be.
385 This option provides an override for these situations.
387 security= [SECURITY] Choose a security module to enable at boot.
388 If this boot parameter is not specified, only the first
389 security module asking for security registration will be
390 loaded. An invalid security module name will be treated
391 as if no module has been chosen.
393 capability.disable=
394 [SECURITY] Disable capabilities. This would normally
395 be used only if an alternative security model is to be
396 configured. Potentially dangerous and should only be
397 used if you are entirely sure of the consequences.
399 ccw_timeout_log [S390]
400 See Documentation/s390/CommonIO for details.
402 cgroup_disable= [KNL] Disable a particular controller
403 Format: {name of the controller(s) to disable}
404 {Currently supported controllers - "memory"}
406 checkreqprot [SELINUX] Set initial checkreqprot flag value.
407 Format: { "0" | "1" }
408 See security/selinux/Kconfig help text.
409 0 -- check protection applied by kernel (includes
410 any implied execute protection).
411 1 -- check protection requested by application.
412 Default value is set via a kernel config option.
413 Value can be changed at runtime via
414 /selinux/checkreqprot.
416 cio_ignore= [S390]
417 See Documentation/s390/CommonIO for details.
419 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
420 [Deprecated]
421 Forces specified clocksource (if available) to be used
422 when calculating gettimeofday(). If specified
423 clocksource is not available, it defaults to PIT.
424 Format: { pit | tsc | cyclone | pmtmr }
426 clocksource= [GENERIC_TIME] Override the default clocksource
427 Format: <string>
428 Override the default clocksource and use the clocksource
429 with the name specified.
430 Some clocksource names to choose from, depending on
431 the platform:
432 [all] jiffies (this is the base, fallback clocksource)
433 [ACPI] acpi_pm
434 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
435 pxa_timer,timer3,32k_counter,timer0_1
436 [AVR32] avr32
437 [X86-32] pit,hpet,tsc,vmi-timer;
438 scx200_hrt on Geode; cyclone on IBM x440
439 [MIPS] MIPS
440 [PARISC] cr16
441 [S390] tod
442 [SH] SuperH
443 [SPARC64] tick
444 [X86-64] hpet,tsc
446 clearcpuid=BITNUM [X86]
447 Disable CPUID feature X for the kernel. See
448 include/asm-x86/cpufeature.h for the valid bit numbers.
449 Note the Linux specific bits are not necessarily
450 stable over kernel options, but the vendor specific
451 ones should be.
452 Also note that user programs calling CPUID directly
453 or using the feature without checking anything
454 will still see it. This just prevents it from
455 being used by the kernel or shown in /proc/cpuinfo.
456 Also note the kernel might malfunction if you disable
457 some critical bits.
459 code_bytes [IA32/X86_64] How many bytes of object code to print
460 in an oops report.
461 Range: 0 - 8192
462 Default: 64
464 disable_8254_timer
465 enable_8254_timer
466 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
467 over the 8254 in addition to over the IO-APIC. The
468 kernel tries to set a sensible default.
470 hpet= [X86-32,HPET] option to control HPET usage
471 Format: { enable (default) | disable | force }
472 disable: disable HPET and use PIT instead
473 force: allow force enabled of undocumented chips (ICH4,
474 VIA, nVidia)
476 com20020= [HW,NET] ARCnet - COM20020 chipset
477 Format:
478 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
480 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
481 Format: <io>[,<irq>]
483 com90xx= [HW,NET]
484 ARCnet - COM90xx chipset (memory-mapped buffers)
485 Format: <io>[,<irq>[,<memstart>]]
487 condev= [HW,S390] console device
488 conmode=
490 console= [KNL] Output console device and options.
492 tty<n> Use the virtual console device <n>.
494 ttyS<n>[,options]
495 ttyUSB0[,options]
496 Use the specified serial port. The options are of
497 the form "bbbbpnf", where "bbbb" is the baud rate,
498 "p" is parity ("n", "o", or "e"), "n" is number of
499 bits, and "f" is flow control ("r" for RTS or
500 omit it). Default is "9600n8".
502 See Documentation/serial-console.txt for more
503 information. See
504 Documentation/networking/netconsole.txt for an
505 alternative.
507 uart[8250],io,<addr>[,options]
508 uart[8250],mmio,<addr>[,options]
509 Start an early, polled-mode console on the 8250/16550
510 UART at the specified I/O port or MMIO address,
511 switching to the matching ttyS device later. The
512 options are the same as for ttyS, above.
514 If the device connected to the port is not a TTY but a braille
515 device, prepend "brl," before the device type, for instance
516 console=brl,ttyS0
517 For now, only VisioBraille is supported.
519 earlycon= [KNL] Output early console device and options.
520 uart[8250],io,<addr>[,options]
521 uart[8250],mmio,<addr>[,options]
522 Start an early, polled-mode console on the 8250/16550
523 UART at the specified I/O port or MMIO address.
524 The options are the same as for ttyS, above.
526 no_console_suspend
527 [HW] Never suspend the console
528 Disable suspending of consoles during suspend and
529 hibernate operations. Once disabled, debugging
530 messages can reach various consoles while the rest
531 of the system is being put to sleep (ie, while
532 debugging driver suspend/resume hooks). This may
533 not work reliably with all consoles, but is known
534 to work with serial and VGA consoles.
536 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
537 Format:
538 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
540 crashkernel=nn[KMG]@ss[KMG]
541 [KNL] Reserve a chunk of physical memory to
542 hold a kernel to switch to with kexec on panic.
544 crashkernel=range1:size1[,range2:size2,...][@offset]
545 [KNL] Same as above, but depends on the memory
546 in the running system. The syntax of range is
547 start-[end] where start and end are both
548 a memory unit (amount[KMG]). See also
549 Documentation/kdump/kdump.txt for a example.
551 cs4232= [HW,OSS]
552 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
554 cs89x0_dma= [HW,NET]
555 Format: <dma>
557 cs89x0_media= [HW,NET]
558 Format: { rj45 | aui | bnc }
560 dasd= [HW,NET]
561 See header of drivers/s390/block/dasd_devmap.c.
563 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
564 (one device per port)
565 Format: <port#>,<type>
566 See also Documentation/input/joystick-parport.txt
568 debug [KNL] Enable kernel debugging (events log level).
570 debug_locks_verbose=
571 [KNL] verbose self-tests
572 Format=<0|1>
573 Print debugging info while doing the locking API
574 self-tests.
575 We default to 0 (no extra messages), setting it to
576 1 will print _a lot_ more information - normally
577 only useful to kernel developers.
579 debug_objects [KNL] Enable object debugging
581 debugpat [X86] Enable PAT debugging
583 decnet.addr= [HW,NET]
584 Format: <area>[,<node>]
585 See also Documentation/networking/decnet.txt.
587 vt.default_blu= [VT]
588 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
589 Change the default blue palette of the console.
590 This is a 16-member array composed of values
591 ranging from 0-255.
593 vt.default_grn= [VT]
594 Format: <green0>,<green1>,<green2>,...,<green15>
595 Change the default green palette of the console.
596 This is a 16-member array composed of values
597 ranging from 0-255.
599 vt.default_red= [VT]
600 Format: <red0>,<red1>,<red2>,...,<red15>
601 Change the default red palette of the console.
602 This is a 16-member array composed of values
603 ranging from 0-255.
605 vt.default_utf8=
606 [VT]
607 Format=<0|1>
608 Set system-wide default UTF-8 mode for all tty's.
609 Default is 1, i.e. UTF-8 mode is enabled for all
610 newly opened terminals.
612 dhash_entries= [KNL]
613 Set number of hash buckets for dentry cache.
615 digi= [HW,SERIAL]
616 IO parameters + enable/disable command.
618 digiepca= [HW,SERIAL]
619 See drivers/char/README.epca and
620 Documentation/digiepca.txt.
622 disable_mtrr_cleanup [X86]
623 enable_mtrr_cleanup [X86]
624 The kernel tries to adjust MTRR layout from continuous
625 to discrete, to make X server driver able to add WB
626 entry later. This parameter enables/disables that.
628 mtrr_chunk_size=nn[KMG] [X86]
629 used for mtrr cleanup. It is largest continous chunk
630 that could hold holes aka. UC entries.
632 mtrr_gran_size=nn[KMG] [X86]
633 Used for mtrr cleanup. It is granularity of mtrr block.
634 Default is 1.
635 Large value could prevent small alignment from
636 using up MTRRs.
638 mtrr_spare_reg_nr=n [X86]
639 Format: <integer>
640 Range: 0,7 : spare reg number
641 Default : 1
642 Used for mtrr cleanup. It is spare mtrr entries number.
643 Set to 2 or more if your graphical card needs more.
645 disable_mtrr_trim [X86, Intel and AMD only]
646 By default the kernel will trim any uncacheable
647 memory out of your available memory pool based on
648 MTRR settings. This parameter disables that behavior,
649 possibly causing your machine to run very slowly.
651 dmasound= [HW,OSS] Sound subsystem buffers
653 dscc4.setup= [NET]
655 dtc3181e= [HW,SCSI]
657 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
658 earlyprintk=vga
659 earlyprintk=serial[,ttySn[,baudrate]]
661 Append ",keep" to not disable it when the real console
662 takes over.
664 Only vga or serial at a time, not both.
666 Currently only ttyS0 and ttyS1 are supported.
668 Interaction with the standard serial driver is not
669 very good.
671 The VGA output is eventually overwritten by the real
672 console.
674 eata= [HW,SCSI]
676 edd= [EDD]
677 Format: {"off" | "on" | "skip[mbr]"}
679 eisa_irq_edge= [PARISC,HW]
680 See header of drivers/parisc/eisa.c.
682 elanfreq= [X86-32]
683 See comment before function elanfreq_setup() in
684 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
686 elevator= [IOSCHED]
687 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
688 See Documentation/block/as-iosched.txt and
689 Documentation/block/deadline-iosched.txt for details.
691 elfcorehdr= [X86-32, X86_64]
692 Specifies physical address of start of kernel core
693 image elf header. Generally kexec loader will
694 pass this option to capture kernel.
695 See Documentation/kdump/kdump.txt for details.
697 enforcing [SELINUX] Set initial enforcing status.
698 Format: {"0" | "1"}
699 See security/selinux/Kconfig help text.
700 0 -- permissive (log only, no denials).
701 1 -- enforcing (deny and log).
702 Default value is 0.
703 Value can be changed at runtime via /selinux/enforce.
705 es1371= [HW,OSS]
706 Format: <spdif>,[<nomix>,[<amplifier>]]
707 See also header of sound/oss/es1371.c.
709 ether= [HW,NET] Ethernet cards parameters
710 This option is obsoleted by the "netdev=" option, which
711 has equivalent usage. See its documentation for details.
713 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
714 Format: <io>[,<irq>]
716 failslab=
717 fail_page_alloc=
718 fail_make_request=[KNL]
719 General fault injection mechanism.
720 Format: <interval>,<probability>,<space>,<times>
721 See also /Documentation/fault-injection/.
723 fd_mcs= [HW,SCSI]
724 See header of drivers/scsi/fd_mcs.c.
726 fdomain= [HW,SCSI]
727 See header of drivers/scsi/fdomain.c.
729 floppy= [HW]
730 See Documentation/floppy.txt.
732 force_pal_cache_flush
733 [IA-64] Avoid check_sal_cache_flush which may hang on
734 buggy SAL_CACHE_FLUSH implementations. Using this
735 parameter will force ia64_sal_cache_flush to call
736 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
738 gamecon.map[2|3]=
739 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
740 support via parallel port (up to 5 devices per port)
741 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
742 See also Documentation/input/joystick-parport.txt
744 gamma= [HW,DRM]
746 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
747 Format: off | on
748 default: on
750 gdth= [HW,SCSI]
751 See header of drivers/scsi/gdth.c.
753 gpt [EFI] Forces disk with valid GPT signature but
754 invalid Protective MBR to be treated as GPT.
756 gvp11= [HW,SCSI]
758 hashdist= [KNL,NUMA] Large hashes allocated during boot
759 are distributed across NUMA nodes. Defaults on
760 for IA-64, off otherwise.
761 Format: 0 | 1 (for off | on)
763 hcl= [IA-64] SGI's Hardware Graph compatibility layer
765 hd= [EIDE] (E)IDE hard drive subsystem geometry
766 Format: <cyl>,<head>,<sect>
768 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
769 size of <nn>. This works even on boxes that have no
770 highmem otherwise. This also works to reduce highmem
771 size on bigger boxes.
773 highres= [KNL] Enable/disable high resolution timer mode.
774 Valid parameters: "on", "off"
775 Default: "on"
777 hisax= [HW,ISDN]
778 See Documentation/isdn/README.HiSax.
780 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
781 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
782 On x86-64 and powerpc, this option can be specified
783 multiple times interleaved with hugepages= to reserve
784 huge pages of different sizes. Valid pages sizes on
785 x86-64 are 2M (when the CPU supports "pse") and 1G
786 (when the CPU supports the "pdpe1gb" cpuinfo flag)
787 Note that 1GB pages can only be allocated at boot time
788 using hugepages= and not freed afterwards.
789 default_hugepagesz=
790 [same as hugepagesz=] The size of the default
791 HugeTLB page size. This is the size represented by
792 the legacy /proc/ hugepages APIs, used for SHM, and
793 default size when mounting hugetlbfs filesystems.
794 Defaults to the default architecture's huge page size
795 if not specified.
797 i8042.direct [HW] Put keyboard port into non-translated mode
798 i8042.dumbkbd [HW] Pretend that controller can only read data from
799 keyboard and cannot control its state
800 (Don't attempt to blink the leds)
801 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
802 i8042.nokbd [HW] Don't check/create keyboard port
803 i8042.noloop [HW] Disable the AUX Loopback command while probing
804 for the AUX port
805 i8042.nomux [HW] Don't check presence of an active multiplexing
806 controller
807 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
808 controllers
809 i8042.panicblink=
810 [HW] Frequency with which keyboard LEDs should blink
811 when kernel panics (default is 0.5 sec)
812 i8042.reset [HW] Reset the controller during init and cleanup
813 i8042.unlock [HW] Unlock (ignore) the keylock
815 i810= [HW,DRM]
817 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
818 indicates that the driver is running on unsupported
819 hardware.
820 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
821 does not match list of supported models.
822 i8k.power_status
823 [HW] Report power status in /proc/i8k
824 (disabled by default)
825 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
826 capability is set.
828 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
829 See Documentation/mca.txt.
831 icn= [HW,ISDN]
832 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
834 ide= [HW] (E)IDE subsystem
835 Format: ide=nodma or ide=doubler
836 See Documentation/ide/ide.txt.
838 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
839 See Documentation/ide/ide.txt.
841 idle= [X86]
842 Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
843 Poll forces a polling idle loop that can slightly improves the performance
844 of waking up a idle CPU, but will use a lot of power and make the system
845 run hot. Not recommended.
846 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
847 to not use it because it doesn't save as much power as a normal idle
848 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
849 as idle=poll.
850 idle=halt. Halt is forced to be used for CPU idle.
851 In such case C2/C3 won't be used again.
852 idle=nomwait. Disable mwait for CPU C-states
854 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
855 Claim all unknown PCI IDE storage controllers.
857 ignore_loglevel [KNL]
858 Ignore loglevel setting - this will print /all/
859 kernel messages to the console. Useful for debugging.
861 ihash_entries= [KNL]
862 Set number of hash buckets for inode cache.
864 in2000= [HW,SCSI]
865 See header of drivers/scsi/in2000.c.
867 init= [KNL]
868 Format: <full_path>
869 Run specified binary instead of /sbin/init as init
870 process.
872 initcall_debug [KNL] Trace initcalls as they are executed. Useful
873 for working out where the kernel is dying during
874 startup.
876 initrd= [BOOT] Specify the location of the initial ramdisk
878 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
879 Format: <irq>
881 inttest= [IA64]
883 iommu= [x86]
884 off
885 force
886 noforce
887 biomerge
888 panic
889 nopanic
890 merge
891 nomerge
892 forcesac
893 soft
896 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
897 off
898 Disable intel iommu driver.
899 igfx_off [Default Off]
900 By default, gfx is mapped as normal device. If a gfx
901 device has a dedicated DMAR unit, the DMAR unit is
902 bypassed by not enabling DMAR with this option. In
903 this case, gfx device will use physical address for
904 DMA.
905 forcedac [x86_64]
906 With this option iommu will not optimize to look
907 for io virtual address below 32 bit forcing dual
908 address cycle on pci bus for cards supporting greater
909 than 32 bit addressing. The default is to look
910 for translation below 32 bit and if not available
911 then look in the higher range.
912 strict [Default Off]
913 With this option on every unmap_single operation will
914 result in a hardware IOTLB flush operation as opposed
915 to batching them for performance.
917 io_delay= [X86-32,X86-64] I/O delay method
918 0x80
919 Standard port 0x80 based delay
920 0xed
921 Alternate port 0xed based delay (needed on some systems)
922 udelay
923 Simple two microseconds delay
924 none
925 No delay
927 io7= [HW] IO7 for Marvel based alpha systems
928 See comment before marvel_specify_io7 in
929 arch/alpha/kernel/core_marvel.c.
931 ip= [IP_PNP]
932 See Documentation/filesystems/nfsroot.txt.
934 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
935 See comment before ip2_setup() in
936 drivers/char/ip2/ip2base.c.
938 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
939 See header of drivers/scsi/ips.c.
941 ports= [IP_VS_FTP] IPVS ftp helper module
942 Default is 21.
943 Up to 8 (IP_VS_APP_MAX_PORTS) ports
944 may be specified.
945 Format: <port>,<port>....
947 irqfixup [HW]
948 When an interrupt is not handled search all handlers
949 for it. Intended to get systems with badly broken
950 firmware running.
952 irqpoll [HW]
953 When an interrupt is not handled search all handlers
954 for it. Also check all handlers each timer
955 interrupt. Intended to get systems with badly broken
956 firmware running.
958 isapnp= [ISAPNP]
959 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
961 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
962 Format:
963 <cpu number>,...,<cpu number>
964 or
965 <cpu number>-<cpu number> (must be a positive range in ascending order)
966 or a mixture
967 <cpu number>,...,<cpu number>-<cpu number>
968 This option can be used to specify one or more CPUs
969 to isolate from the general SMP balancing and scheduling
970 algorithms. The only way to move a process onto or off
971 an "isolated" CPU is via the CPU affinity syscalls.
972 <cpu number> begins at 0 and the maximum value is
973 "number of CPUs in system - 1".
975 This option is the preferred way to isolate CPUs. The
976 alternative -- manually setting the CPU mask of all
977 tasks in the system -- can cause problems and
978 suboptimal load balancer performance.
980 iucv= [HW,NET]
982 js= [HW,JOY] Analog joystick
983 See Documentation/input/joystick.txt.
985 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
986 specifies the amount of memory usable by the kernel
987 for non-movable allocations. The requested amount is
988 spread evenly throughout all nodes in the system. The
989 remaining memory in each node is used for Movable
990 pages. In the event, a node is too small to have both
991 kernelcore and Movable pages, kernelcore pages will
992 take priority and other nodes will have a larger number
993 of kernelcore pages. The Movable zone is used for the
994 allocation of pages that may be reclaimed or moved
995 by the page migration subsystem. This means that
996 HugeTLB pages may not be allocated from this zone.
997 Note that allocations like PTEs-from-HighMem still
998 use the HighMem zone if it exists, and the Normal
999 zone if it does not.
1001 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1002 is similar to kernelcore except it specifies the
1003 amount of memory used for migratable allocations.
1004 If both kernelcore and movablecore is specified,
1005 then kernelcore will be at *least* the specified
1006 value but may be more. If movablecore on its own
1007 is specified, the administrator must be careful
1008 that the amount of memory usable for all allocations
1009 is not too small.
1011 keepinitrd [HW,ARM]
1013 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1014 in oops dumps.
1016 kgdboc= [HW] kgdb over consoles.
1017 Requires a tty driver that supports console polling.
1018 (only serial suported for now)
1019 Format: <serial_device>[,baud]
1021 l2cr= [PPC]
1023 l3cr= [PPC]
1025 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1026 disabled it.
1028 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
1029 C2 power state.
1031 libata.dma= [LIBATA] DMA control
1032 libata.dma=0 Disable all PATA and SATA DMA
1033 libata.dma=1 PATA and SATA Disk DMA only
1034 libata.dma=2 ATAPI (CDROM) DMA only
1035 libata.dma=4 Compact Flash DMA only
1036 Combinations also work, so libata.dma=3 enables DMA
1037 for disks and CDROMs, but not CFs.
1039 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1040 when set.
1041 Format: <int>
1043 libata.force= [LIBATA] Force configurations. The format is comma
1044 separated list of "[ID:]VAL" where ID is
1045 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1046 matching port, link or device. Basically, it matches
1047 the ATA ID string printed on console by libata. If
1048 the whole ID part is omitted, the last PORT and DEVICE
1049 values are used. If ID hasn't been specified yet, the
1050 configuration applies to all ports, links and devices.
1052 If only DEVICE is omitted, the parameter applies to
1053 the port and all links and devices behind it. DEVICE
1054 number of 0 either selects the first device or the
1055 first fan-out link behind PMP device. It does not
1056 select the host link. DEVICE number of 15 selects the
1057 host link and device attached to it.
1059 The VAL specifies the configuration to force. As long
1060 as there's no ambiguity shortcut notation is allowed.
1061 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1062 The following configurations can be forced.
1064 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1065 Any ID with matching PORT is used.
1067 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1069 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1070 udma[/][16,25,33,44,66,100,133] notation is also
1071 allowed.
1073 * [no]ncq: Turn on or off NCQ.
1075 If there are multiple matching configurations changing
1076 the same attribute, the last one is used.
1078 load_ramdisk= [RAM] List of ramdisks to load from floppy
1079 See Documentation/ramdisk.txt.
1081 lockd.nlm_grace_period=P [NFS] Assign grace period.
1082 Format: <integer>
1084 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1085 Format: <integer>
1087 lockd.nlm_timeout=T [NFS] Assign timeout value.
1088 Format: <integer>
1090 lockd.nlm_udpport=M [NFS] Assign UDP port.
1091 Format: <integer>
1093 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1094 Format: <irq>
1096 loglevel= All Kernel Messages with a loglevel smaller than the
1097 console loglevel will be printed to the console. It can
1098 also be changed with klogd or other programs. The
1099 loglevels are defined as follows:
1101 0 (KERN_EMERG) system is unusable
1102 1 (KERN_ALERT) action must be taken immediately
1103 2 (KERN_CRIT) critical conditions
1104 3 (KERN_ERR) error conditions
1105 4 (KERN_WARNING) warning conditions
1106 5 (KERN_NOTICE) normal but significant condition
1107 6 (KERN_INFO) informational
1108 7 (KERN_DEBUG) debug-level messages
1110 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1111 Format: { n | nk | nM }
1112 n must be a power of two. The default size
1113 is set in the kernel config file.
1115 logo.nologo [FB] Disables display of the built-in Linux logo.
1116 This may be used to provide more screen space for
1117 kernel log messages and is useful when debugging
1118 kernel boot problems.
1120 lp=0 [LP] Specify parallel ports to use, e.g,
1121 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1122 lp=reset first parallel port). 'lp=0' disables the
1123 lp=auto printer driver. 'lp=reset' (which can be
1124 specified in addition to the ports) causes
1125 attached printers to be reset. Using
1126 lp=port1,port2,... specifies the parallel ports
1127 to associate lp devices with, starting with
1128 lp0. A port specification may be 'none' to skip
1129 that lp device, or a parport name such as
1130 'parport0'. Specifying 'lp=auto' instead of a
1131 port specification list means that device IDs
1132 from each port should be examined, to see if
1133 an IEEE 1284-compliant printer is attached; if
1134 so, the driver will manage that printer.
1135 See also header of drivers/char/lp.c.
1137 lpj=n [KNL]
1138 Sets loops_per_jiffy to given constant, thus avoiding
1139 time-consuming boot-time autodetection (up to 250 ms per
1140 CPU). 0 enables autodetection (default). To determine
1141 the correct value for your kernel, boot with normal
1142 autodetection and see what value is printed. Note that
1143 on SMP systems the preset will be applied to all CPUs,
1144 which is likely to cause problems if your CPUs need
1145 significantly divergent settings. An incorrect value
1146 will cause delays in the kernel to be wrong, leading to
1147 unpredictable I/O errors and other breakage. Although
1148 unlikely, in the extreme case this might damage your
1149 hardware.
1151 ltpc= [NET]
1152 Format: <io>,<irq>,<dma>
1154 mac5380= [HW,SCSI] Format:
1155 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1157 machvec= [IA64] Force the use of a particular machine-vector
1158 (machvec) in a generic kernel.
1159 Example: machvec=hpzx1_swiotlb
1161 max_loop= [LOOP] Maximum number of loopback devices that can
1162 be mounted
1163 Format: <1-256>
1165 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1166 should make use of. maxcpus=n : n >= 0 limits the
1167 kernel to using 'n' processors. n=0 is a special case,
1168 it is equivalent to "nosmp", which also disables
1169 the IO APIC.
1171 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1172 equal to this physical address is ignored.
1174 max_luns= [SCSI] Maximum number of LUNs to probe.
1175 Should be between 1 and 2^32-1.
1177 max_report_luns=
1178 [SCSI] Maximum number of LUNs received.
1179 Should be between 1 and 16384.
1181 mcatest= [IA-64]
1183 mce [X86-32] Machine Check Exception
1185 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1187 md= [HW] RAID subsystems devices and level
1188 See Documentation/md.txt.
1190 mdacon= [MDA]
1191 Format: <first>,<last>
1192 Specifies range of consoles to be captured by the MDA.
1194 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1195 Amount of memory to be used when the kernel is not able
1196 to see the whole system memory or for test.
1197 [X86-32] Use together with memmap= to avoid physical
1198 address space collisions. Without memmap= PCI devices
1199 could be placed at addresses belonging to unused RAM.
1201 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1202 memory.
1204 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1205 E820 memory map, as specified by the user.
1206 Such memmap=exactmap lines can be constructed based on
1207 BIOS output or other requirements. See the memmap=nn@ss
1208 option description.
1210 memmap=nn[KMG]@ss[KMG]
1211 [KNL] Force usage of a specific region of memory
1212 Region of memory to be used, from ss to ss+nn.
1214 memmap=nn[KMG]#ss[KMG]
1215 [KNL,ACPI] Mark specific memory as ACPI data.
1216 Region of memory to be used, from ss to ss+nn.
1218 memmap=nn[KMG]$ss[KMG]
1219 [KNL,ACPI] Mark specific memory as reserved.
1220 Region of memory to be used, from ss to ss+nn.
1221 Example: Exclude memory from 0x18690000-0x1869ffff
1222 memmap=64K$0x18690000
1223 or
1224 memmap=0x10000$0x18690000
1226 memtest= [KNL,X86] Enable memtest
1227 Format: <integer>
1228 range: 0,4 : pattern number
1229 default : 0 <disable>
1231 meye.*= [HW] Set MotionEye Camera parameters
1232 See Documentation/video4linux/meye.txt.
1234 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1235 Multi-Function General Purpose Timers on AMD Geode
1236 platforms.
1238 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1239 the BIOS has incorrectly applied a workaround. TinyBIOS
1240 version 0.98 is known to be affected, 0.99 fixes the
1241 problem by letting the user disable the workaround.
1243 mga= [HW,DRM]
1245 mminit_loglevel=
1246 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1247 parameter allows control of the logging verbosity for
1248 the additional memory initialisation checks. A value
1249 of 0 disables mminit logging and a level of 4 will
1250 log everything. Information is printed at KERN_DEBUG
1251 so loglevel=8 may also need to be specified.
1253 mousedev.tap_time=
1254 [MOUSE] Maximum time between finger touching and
1255 leaving touchpad surface for touch to be considered
1256 a tap and be reported as a left button click (for
1257 touchpads working in absolute mode only).
1258 Format: <msecs>
1259 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1260 reporting absolute coordinates, such as tablets
1261 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1262 reporting absolute coordinates, such as tablets
1264 mpu401= [HW,OSS]
1265 Format: <io>,<irq>
1267 MTD_Partition= [MTD]
1268 Format: <name>,<region-number>,<size>,<offset>
1270 MTD_Region= [MTD] Format:
1271 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1273 mtdparts= [MTD]
1274 See drivers/mtd/cmdlinepart.c.
1276 mtdset= [ARM]
1277 ARM/S3C2412 JIVE boot control
1279 See arch/arm/mach-s3c2412/mach-jive.c
1281 mtouchusb.raw_coordinates=
1282 [HW] Make the MicroTouch USB driver use raw coordinates
1283 ('y', default) or cooked coordinates ('n')
1285 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1287 NCR_D700= [HW,SCSI]
1288 See header of drivers/scsi/NCR_D700.c.
1290 ncr5380= [HW,SCSI]
1292 ncr53c400= [HW,SCSI]
1294 ncr53c400a= [HW,SCSI]
1296 ncr53c406a= [HW,SCSI]
1298 ncr53c8xx= [HW,SCSI]
1300 netdev= [NET] Network devices parameters
1301 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1302 Note that mem_start is often overloaded to mean
1303 something different and driver-specific.
1304 This usage is only documented in each driver source
1305 file if at all.
1307 nf_conntrack.acct=
1308 [NETFILTER] Enable connection tracking flow accounting
1309 0 to disable accounting
1310 1 to enable accounting
1311 Default value depends on CONFIG_NF_CT_ACCT that is
1312 going to be removed in 2.6.29.
1314 nfsaddrs= [NFS]
1315 See Documentation/filesystems/nfsroot.txt.
1317 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1318 See Documentation/filesystems/nfsroot.txt.
1320 nfs.callback_tcpport=
1321 [NFS] set the TCP port on which the NFSv4 callback
1322 channel should listen.
1324 nfs.idmap_cache_timeout=
1325 [NFS] set the maximum lifetime for idmapper cache
1326 entries.
1328 nfs.enable_ino64=
1329 [NFS] enable 64-bit inode numbers.
1330 If zero, the NFS client will fake up a 32-bit inode
1331 number for the readdir() and stat() syscalls instead
1332 of returning the full 64-bit number.
1333 The default is to return 64-bit inode numbers.
1335 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1336 when a NMI is triggered.
1337 Format: [state][,regs][,debounce][,die]
1339 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1341 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1342 emulation library even if a 387 maths coprocessor
1343 is present.
1345 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1346 caches in the slab allocator. Saves per-node memory,
1347 but will impact performance.
1349 noalign [KNL,ARM]
1351 noapic [SMP,APIC] Tells the kernel to not make use of any
1352 IOAPICs that may be present in the system.
1354 nobats [PPC] Do not use BATs for mapping kernel lowmem
1355 on "Classic" PPC cores.
1357 nocache [ARM]
1359 nodelayacct [KNL] Disable per-task delay accounting
1361 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1363 noefi [X86-32,X86-64] Disable EFI runtime services support.
1365 noexec [IA-64]
1367 noexec [X86-32,X86-64]
1368 On X86-32 available only on PAE configured kernels.
1369 noexec=on: enable non-executable mappings (default)
1370 noexec=off: disable non-executable mappings
1372 noexec32 [X86-64]
1373 This affects only 32-bit executables.
1374 noexec32=on: enable non-executable mappings (default)
1375 read doesn't imply executable mappings
1376 noexec32=off: disable non-executable mappings
1377 read implies executable mappings
1379 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1380 register save and restore. The kernel will only save
1381 legacy floating-point registers on task switch.
1383 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1385 nohlt [BUGS=ARM]
1387 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1388 instruction doesn't work correctly and not to
1389 use it.
1391 nohalt [IA-64] Tells the kernel not to use the power saving
1392 function PAL_HALT_LIGHT when idle. This increases
1393 power-consumption. On the positive side, it reduces
1394 interrupt wake-up latency, which may improve performance
1395 in certain environments such as networked servers or
1396 real-time systems.
1398 nohz= [KNL] Boottime enable/disable dynamic ticks
1399 Valid arguments: on, off
1400 Default: on
1402 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1404 noirqdebug [X86-32] Disables the code which attempts to detect and
1405 disable unhandled interrupt sources.
1407 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1408 broken timer IRQ sources.
1410 noisapnp [ISAPNP] Disables ISA PnP code.
1412 noinitrd [RAM] Tells the kernel not to load any configured
1413 initial RAM disk.
1415 nointroute [IA-64]
1417 nojitter [IA64] Disables jitter checking for ITC timers.
1419 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1421 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1423 noltlbs [PPC] Do not use large page/tlb entries for kernel
1424 lowmem mapping on PPC40x.
1426 nomca [IA-64] Disable machine check abort handling
1428 nomce [X86-32] Machine Check Exception
1430 nomfgpt [X86-32] Disable Multi-Function General Purpose
1431 Timer usage (for AMD Geode machines).
1433 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1435 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1436 with UP alternatives
1438 noresidual [PPC] Don't use residual data on PReP machines.
1440 noresume [SWSUSP] Disables resume and restores original swap
1441 space.
1443 no-scroll [VGA] Disables scrollback.
1444 This is required for the Braillex ib80-piezo Braille
1445 reader made by F.H. Papenmeier (Germany).
1447 nosbagart [IA-64]
1449 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1451 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1452 and disable the IO APIC. legacy for "maxcpus=0".
1454 nosoftlockup [KNL] Disable the soft-lockup detector.
1456 nosync [HW,M68K] Disables sync negotiation for all devices.
1458 notsc [BUGS=X86-32] Disable Time Stamp Counter
1460 nousb [USB] Disable the USB subsystem
1462 nowb [ARM]
1464 nptcg= [IA64] Override max number of concurrent global TLB
1465 purges which is reported from either PAL_VM_SUMMARY or
1466 SAL PALO.
1468 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1469 one of ['zone', 'node', 'default'] can be specified
1470 This can be set from sysctl after boot.
1471 See Documentation/sysctl/vm.txt for details.
1473 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1475 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1476 Rather than timing out after 20 ms if an EC
1477 command is not properly ACKed, override the length
1478 of the timeout. We have interrupts disabled while
1479 waiting for the ACK, so if this is set too high
1480 interrupts *may* be lost!
1482 opl3= [HW,OSS]
1483 Format: <io>
1485 oprofile.timer= [HW]
1486 Use timer interrupt instead of performance counters
1488 osst= [HW,SCSI] SCSI Tape Driver
1489 Format: <buffer_size>,<write_threshold>
1490 See also Documentation/scsi/st.txt.
1492 panic= [KNL] Kernel behaviour on panic
1493 Format: <timeout>
1495 parkbd.port= [HW] Parallel port number the keyboard adapter is
1496 connected to, default is 0.
1497 Format: <parport#>
1498 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1499 0 for XT, 1 for AT (default is AT).
1500 Format: <mode>
1502 parport= [HW,PPT] Specify parallel ports. 0 disables.
1503 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1504 Use 'auto' to force the driver to use any
1505 IRQ/DMA settings detected (the default is to
1506 ignore detected IRQ/DMA settings because of
1507 possible conflicts). You can specify the base
1508 address, IRQ, and DMA settings; IRQ and DMA
1509 should be numbers, or 'auto' (for using detected
1510 settings on that particular port), or 'nofifo'
1511 (to avoid using a FIFO even if it is detected).
1512 Parallel ports are assigned in the order they
1513 are specified on the command line, starting
1514 with parport0.
1516 parport_init_mode= [HW,PPT]
1517 Configure VIA parallel port to operate in
1518 a specific mode. This is necessary on Pegasos
1519 computer where firmware has no options for setting
1520 up parallel port mode and sets it to spp.
1521 Currently this function knows 686a and 8231 chips.
1522 Format: [spp|ps2|epp|ecp|ecpepp]
1524 pas2= [HW,OSS] Format:
1525 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1527 pas16= [HW,SCSI]
1528 See header of drivers/scsi/pas16.c.
1530 pause_on_oops=
1531 Halt all CPUs after the first oops has been printed for
1532 the specified number of seconds. This is to be used if
1533 your oopses keep scrolling off the screen.
1535 pcbit= [HW,ISDN]
1537 pcd. [PARIDE]
1538 See header of drivers/block/paride/pcd.c.
1539 See also Documentation/paride.txt.
1541 pci=option[,option...] [PCI] various PCI subsystem options:
1542 off [X86-32] don't probe for the PCI bus
1543 bios [X86-32] force use of PCI BIOS, don't access
1544 the hardware directly. Use this if your machine
1545 has a non-standard PCI host bridge.
1546 nobios [X86-32] disallow use of PCI BIOS, only direct
1547 hardware access methods are allowed. Use this
1548 if you experience crashes upon bootup and you
1549 suspect they are caused by the BIOS.
1550 conf1 [X86-32] Force use of PCI Configuration
1551 Mechanism 1.
1552 conf2 [X86-32] Force use of PCI Configuration
1553 Mechanism 2.
1554 noaer [PCIE] If the PCIEAER kernel config parameter is
1555 enabled, this kernel boot option can be used to
1556 disable the use of PCIE advanced error reporting.
1557 nodomains [PCI] Disable support for multiple PCI
1558 root domains (aka PCI segments, in ACPI-speak).
1559 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1560 Configuration
1561 nomsi [MSI] If the PCI_MSI kernel config parameter is
1562 enabled, this kernel boot option can be used to
1563 disable the use of MSI interrupts system-wide.
1564 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1565 routing table. These calls are known to be buggy
1566 on several machines and they hang the machine
1567 when used, but on other computers it's the only
1568 way to get the interrupt routing table. Try
1569 this option if the kernel is unable to allocate
1570 IRQs or discover secondary PCI buses on your
1571 motherboard.
1572 rom [X86-32] Assign address space to expansion ROMs.
1573 Use with caution as certain devices share
1574 address decoders between ROMs and other
1575 resources.
1576 norom [X86-32,X86_64] Do not assign address space to
1577 expansion ROMs that do not already have
1578 BIOS assigned address ranges.
1579 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1580 assigned automatically to PCI devices. You can
1581 make the kernel exclude IRQs of your ISA cards
1582 this way.
1583 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1584 of the PIRQ table (normally generated
1585 by the BIOS) if it is outside the
1586 F0000h-100000h range.
1587 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1588 useful if the kernel is unable to find your
1589 secondary buses and you want to tell it
1590 explicitly which ones they are.
1591 assign-busses [X86-32] Always assign all PCI bus
1592 numbers ourselves, overriding
1593 whatever the firmware may have done.
1594 usepirqmask [X86-32] Honor the possible IRQ mask stored
1595 in the BIOS $PIR table. This is needed on
1596 some systems with broken BIOSes, notably
1597 some HP Pavilion N5400 and Omnibook XE3
1598 notebooks. This will have no effect if ACPI
1599 IRQ routing is enabled.
1600 noacpi [X86-32] Do not use ACPI for IRQ routing
1601 or for PCI scanning.
1602 use_crs [X86-32] Use _CRS for PCI resource
1603 allocation.
1604 routeirq Do IRQ routing for all PCI devices.
1605 This is normally done in pci_enable_device(),
1606 so this option is a temporary workaround
1607 for broken drivers that don't call it.
1608 skip_isa_align [X86] do not align io start addr, so can
1609 handle more pci cards
1610 firmware [ARM] Do not re-enumerate the bus but instead
1611 just use the configuration from the
1612 bootloader. This is currently used on
1613 IXP2000 systems where the bus has to be
1614 configured a certain way for adjunct CPUs.
1615 noearly [X86] Don't do any early type 1 scanning.
1616 This might help on some broken boards which
1617 machine check when some devices' config space
1618 is read. But various workarounds are disabled
1619 and some IOMMU drivers will not work.
1620 bfsort Sort PCI devices into breadth-first order.
1621 This sorting is done to get a device
1622 order compatible with older (<= 2.4) kernels.
1623 nobfsort Don't sort PCI devices into breadth-first order.
1624 cbiosize=nn[KMG] The fixed amount of bus space which is
1625 reserved for the CardBus bridge's IO window.
1626 The default value is 256 bytes.
1627 cbmemsize=nn[KMG] The fixed amount of bus space which is
1628 reserved for the CardBus bridge's memory
1629 window. The default value is 64 megabytes.
1631 pcmv= [HW,PCMCIA] BadgePAD 4
1633 pd. [PARIDE]
1634 See Documentation/paride.txt.
1636 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1637 boot time.
1638 Format: { 0 | 1 }
1639 See arch/parisc/kernel/pdc_chassis.c
1641 pf. [PARIDE]
1642 See Documentation/paride.txt.
1644 pg. [PARIDE]
1645 See Documentation/paride.txt.
1647 pirq= [SMP,APIC] Manual mp-table setup
1648 See Documentation/i386/IO-APIC.txt.
1650 plip= [PPT,NET] Parallel port network link
1651 Format: { parport<nr> | timid | 0 }
1652 See also Documentation/parport.txt.
1654 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1655 Override pmtimer IOPort with a hex value.
1656 e.g. pmtmr=0x508
1658 pnpacpi= [ACPI]
1659 { off }
1661 pnpbios= [ISAPNP]
1662 { on | off | curr | res | no-curr | no-res }
1664 pnp_reserve_irq=
1665 [ISAPNP] Exclude IRQs for the autoconfiguration
1667 pnp_reserve_dma=
1668 [ISAPNP] Exclude DMAs for the autoconfiguration
1670 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1671 Ranges are in pairs (I/O port base and size).
1673 pnp_reserve_mem=
1674 [ISAPNP] Exclude memory regions for the
1675 autoconfiguration.
1676 Ranges are in pairs (memory base and size).
1678 print-fatal-signals=
1679 [KNL] debug: print fatal signals
1680 print-fatal-signals=1: print segfault info to
1681 the kernel console.
1682 default: off.
1684 printk.time= Show timing data prefixed to each printk message line
1685 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1687 profile= [KNL] Enable kernel profiling via /proc/profile
1688 Format: [schedule,]<number>
1689 Param: "schedule" - profile schedule points.
1690 Param: <number> - step/bucket size as a power of 2 for
1691 statistical time based profiling.
1692 Param: "sleep" - profile D-state sleeping (millisecs).
1693 Requires CONFIG_SCHEDSTATS
1694 Param: "kvm" - profile VM exits.
1696 processor.max_cstate= [HW,ACPI]
1697 Limit processor to maximum C-state
1698 max_cstate=9 overrides any DMI blacklist limit.
1700 processor.nocst [HW,ACPI]
1701 Ignore the _CST method to determine C-states,
1702 instead using the legacy FADT method
1704 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1705 before loading.
1706 See Documentation/ramdisk.txt.
1708 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1709 probe for; one of (bare|imps|exps|lifebook|any).
1710 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1711 per second.
1712 psmouse.resetafter= [HW,MOUSE]
1713 Try to reset the device after so many bad packets
1714 (0 = never).
1715 psmouse.resolution=
1716 [HW,MOUSE] Set desired mouse resolution, in dpi.
1717 psmouse.smartscroll=
1718 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1719 0 = disabled, 1 = enabled (default).
1721 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1722 Format:
1723 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1725 pt. [PARIDE]
1726 See Documentation/paride.txt.
1728 pty.legacy_count=
1729 [KNL] Number of legacy pty's. Overwrites compiled-in
1730 default number.
1732 quiet [KNL] Disable most log messages
1734 r128= [HW,DRM]
1736 raid= [HW,RAID]
1737 See Documentation/md.txt.
1739 ramdisk_blocksize= [RAM]
1740 See Documentation/ramdisk.txt.
1742 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1743 See Documentation/ramdisk.txt.
1745 rcupdate.blimit= [KNL,BOOT]
1746 Set maximum number of finished RCU callbacks to process
1747 in one batch.
1749 rcupdate.qhimark= [KNL,BOOT]
1750 Set threshold of queued
1751 RCU callbacks over which batch limiting is disabled.
1753 rcupdate.qlowmark= [KNL,BOOT]
1754 Set threshold of queued RCU callbacks below which
1755 batch limiting is re-enabled.
1757 rdinit= [KNL]
1758 Format: <full_path>
1759 Run specified binary instead of /init from the ramdisk,
1760 used for early userspace startup. See initrd.
1762 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1763 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1764 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1766 relax_domain_level=
1767 [KNL, SMP] Set scheduler's default relax_domain_level.
1768 See Documentation/cpusets.txt.
1770 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1772 reservetop= [X86-32]
1773 Format: nn[KMG]
1774 Reserves a hole at the top of the kernel virtual
1775 address space.
1777 reset_devices [KNL] Force drivers to reset the underlying device
1778 during initialization.
1780 resume= [SWSUSP]
1781 Specify the partition device for software suspend
1783 resume_offset= [SWSUSP]
1784 Specify the offset from the beginning of the partition
1785 given by "resume=" at which the swap header is located,
1786 in <PAGE_SIZE> units (needed only for swap files).
1787 See Documentation/power/swsusp-and-swap-files.txt
1789 retain_initrd [RAM] Keep initrd memory after extraction
1791 rhash_entries= [KNL,NET]
1792 Set number of hash buckets for route cache
1794 riscom8= [HW,SERIAL]
1795 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1797 ro [KNL] Mount root device read-only on boot
1799 root= [KNL] Root filesystem
1801 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1802 mount the root filesystem
1804 rootflags= [KNL] Set root filesystem mount option string
1806 rootfstype= [KNL] Set root filesystem type
1808 rootwait [KNL] Wait (indefinitely) for root device to show up.
1809 Useful for devices that are detected asynchronously
1810 (e.g. USB and MMC devices).
1812 root_plug.vendor_id=
1813 [ROOTPLUG] Override the default vendor ID
1815 root_plug.product_id=
1816 [ROOTPLUG] Override the default product ID
1818 root_plug.debug=
1819 [ROOTPLUG] Enable debugging output
1821 rw [KNL] Mount root device read-write on boot
1823 S [KNL] Run init in single mode
1825 sa1100ir [NET]
1826 See drivers/net/irda/sa1100_ir.c.
1828 sbni= [NET] Granch SBNI12 leased line adapter
1830 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1831 Format: <io>[,<timeout>[,<isapnp>]]
1833 scsi_debug_*= [SCSI]
1834 See drivers/scsi/scsi_debug.c.
1836 scsi_default_dev_flags=
1837 [SCSI] SCSI default device flags
1838 Format: <integer>
1840 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1841 Format: <vendor>:<model>:<flags>
1842 (flags are integer value)
1844 scsi_logging_level= [SCSI] a bit mask of logging levels
1845 See drivers/scsi/scsi_logging.h for bits. Also
1846 settable via sysctl at dev.scsi.logging_level
1847 (/proc/sys/dev/scsi/logging_level).
1848 There is also a nice 'scsi_logging_level' script in the
1849 S390-tools package, available for download at
1850 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1852 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1853 discovered. async scans them in kernel threads,
1854 allowing boot to proceed. none ignores them, expecting
1855 user space to do the scan.
1857 selinux [SELINUX] Disable or enable SELinux at boot time.
1858 Format: { "0" | "1" }
1859 See security/selinux/Kconfig help text.
1860 0 -- disable.
1861 1 -- enable.
1862 Default value is set via kernel config option.
1863 If enabled at boot time, /selinux/disable can be used
1864 later to disable prior to initial policy load.
1866 selinux_compat_net =
1867 [SELINUX] Set initial selinux_compat_net flag value.
1868 Format: { "0" | "1" }
1869 0 -- use new secmark-based packet controls
1870 1 -- use legacy packet controls
1871 Default value is 0 (preferred).
1872 Value can be changed at runtime via
1873 /selinux/compat_net.
1875 serialnumber [BUGS=X86-32]
1877 shapers= [NET]
1878 Maximal number of shapers.
1880 sim710= [SCSI,HW]
1881 See header of drivers/scsi/sim710.c.
1883 simeth= [IA-64]
1884 simscsi=
1886 slram= [HW,MTD]
1888 slub_debug[=options[,slabs]] [MM, SLUB]
1889 Enabling slub_debug allows one to determine the
1890 culprit if slab objects become corrupted. Enabling
1891 slub_debug can create guard zones around objects and
1892 may poison objects when not in use. Also tracks the
1893 last alloc / free. For more information see
1894 Documentation/vm/slub.txt.
1896 slub_max_order= [MM, SLUB]
1897 Determines the maximum allowed order for slabs.
1898 A high setting may cause OOMs due to memory
1899 fragmentation. For more information see
1900 Documentation/vm/slub.txt.
1902 slub_min_objects= [MM, SLUB]
1903 The minimum number of objects per slab. SLUB will
1904 increase the slab order up to slub_max_order to
1905 generate a sufficiently large slab able to contain
1906 the number of objects indicated. The higher the number
1907 of objects the smaller the overhead of tracking slabs
1908 and the less frequently locks need to be acquired.
1909 For more information see Documentation/vm/slub.txt.
1911 slub_min_order= [MM, SLUB]
1912 Determines the mininum page order for slabs. Must be
1913 lower than slub_max_order.
1914 For more information see Documentation/vm/slub.txt.
1916 slub_nomerge [MM, SLUB]
1917 Disable merging of slabs with similar size. May be
1918 necessary if there is some reason to distinguish
1919 allocs to different slabs. Debug options disable
1920 merging on their own.
1921 For more information see Documentation/vm/slub.txt.
1923 smart2= [HW]
1924 Format: <io1>[,<io2>[,...,<io8>]]
1926 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1927 attempt to substitute SMP alternatives once at boot.
1929 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1930 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1931 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1932 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1933 smsc-ircc2.ircc_irq= [HW] IRQ line
1934 smsc-ircc2.ircc_dma= [HW] DMA channel
1935 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1936 0: Toshiba Satellite 1800 (GP data pin select)
1937 1: Fast pin select (default)
1938 2: ATC IRMode
1940 snd-ad1816a= [HW,ALSA]
1942 snd-ad1848= [HW,ALSA]
1944 snd-ali5451= [HW,ALSA]
1946 snd-als100= [HW,ALSA]
1948 snd-als4000= [HW,ALSA]
1950 snd-azt2320= [HW,ALSA]
1952 snd-cmi8330= [HW,ALSA]
1954 snd-cmipci= [HW,ALSA]
1956 snd-cs4231= [HW,ALSA]
1958 snd-cs4232= [HW,ALSA]
1960 snd-cs4236= [HW,ALSA]
1962 snd-cs4281= [HW,ALSA]
1964 snd-cs46xx= [HW,ALSA]
1966 snd-dt019x= [HW,ALSA]
1968 snd-dummy= [HW,ALSA]
1970 snd-emu10k1= [HW,ALSA]
1972 snd-ens1370= [HW,ALSA]
1974 snd-ens1371= [HW,ALSA]
1976 snd-es968= [HW,ALSA]
1978 snd-es1688= [HW,ALSA]
1980 snd-es18xx= [HW,ALSA]
1982 snd-es1938= [HW,ALSA]
1984 snd-es1968= [HW,ALSA]
1986 snd-fm801= [HW,ALSA]
1988 snd-gusclassic= [HW,ALSA]
1990 snd-gusextreme= [HW,ALSA]
1992 snd-gusmax= [HW,ALSA]
1994 snd-hdsp= [HW,ALSA]
1996 snd-ice1712= [HW,ALSA]
1998 snd-intel8x0= [HW,ALSA]
2000 snd-interwave= [HW,ALSA]
2002 snd-interwave-stb=
2003 [HW,ALSA]
2005 snd-korg1212= [HW,ALSA]
2007 snd-maestro3= [HW,ALSA]
2009 snd-mpu401= [HW,ALSA]
2011 snd-mtpav= [HW,ALSA]
2013 snd-nm256= [HW,ALSA]
2015 snd-opl3sa2= [HW,ALSA]
2017 snd-opti92x-ad1848=
2018 [HW,ALSA]
2020 snd-opti92x-cs4231=
2021 [HW,ALSA]
2023 snd-opti93x= [HW,ALSA]
2025 snd-pmac= [HW,ALSA]
2027 snd-rme32= [HW,ALSA]
2029 snd-rme96= [HW,ALSA]
2031 snd-rme9652= [HW,ALSA]
2033 snd-sb8= [HW,ALSA]
2035 snd-sb16= [HW,ALSA]
2037 snd-sbawe= [HW,ALSA]
2039 snd-serial= [HW,ALSA]
2041 snd-sgalaxy= [HW,ALSA]
2043 snd-sonicvibes= [HW,ALSA]
2045 snd-sun-amd7930=
2046 [HW,ALSA]
2048 snd-sun-cs4231= [HW,ALSA]
2050 snd-trident= [HW,ALSA]
2052 snd-usb-audio= [HW,ALSA,USB]
2054 snd-via82xx= [HW,ALSA]
2056 snd-virmidi= [HW,ALSA]
2058 snd-wavefront= [HW,ALSA]
2060 snd-ymfpci= [HW,ALSA]
2062 softlockup_panic=
2063 [KNL] Should the soft-lockup detector generate panics.
2065 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2066 See Documentation/sonypi.txt
2068 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2069 See Documentation/specialix.txt.
2071 spia_io_base= [HW,MTD]
2072 spia_fio_base=
2073 spia_pedr=
2074 spia_peddr=
2076 sscape= [HW,OSS]
2077 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2079 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2080 See Documentation/scsi/st.txt.
2082 sti= [PARISC,HW]
2083 Format: <num>
2084 Set the STI (builtin display/keyboard on the HP-PARISC
2085 machines) console (graphic card) which should be used
2086 as the initial boot-console.
2087 See also comment in drivers/video/console/sticore.c.
2089 sti_font= [HW]
2090 See comment in drivers/video/console/sticore.c.
2092 stifb= [HW]
2093 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2095 sunrpc.pool_mode=
2096 [NFS]
2097 Control how the NFS server code allocates CPUs to
2098 service thread pools. Depending on how many NICs
2099 you have and where their interrupts are bound, this
2100 option will affect which CPUs will do NFS serving.
2101 Note: this parameter cannot be changed while the
2102 NFS server is running.
2104 auto the server chooses an appropriate mode
2105 automatically using heuristics
2106 global a single global pool contains all CPUs
2107 percpu one pool for each CPU
2108 pernode one pool for each NUMA node (equivalent
2109 to global on non-NUMA machines)
2111 swiotlb= [IA-64] Number of I/O TLB slabs
2113 switches= [HW,M68k]
2115 sym53c416= [HW,SCSI]
2116 See header of drivers/scsi/sym53c416.c.
2118 sysrq_always_enabled
2119 [KNL]
2120 Ignore sysrq setting - this boot parameter will
2121 neutralize any effect of /proc/sys/kernel/sysrq.
2122 Useful for debugging.
2124 t128= [HW,SCSI]
2125 See header of drivers/scsi/t128.c.
2127 tdfx= [HW,DRM]
2129 test_suspend= [SUSPEND]
2130 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2131 standby suspend) as the system sleep state to briefly
2132 enter during system startup. The system is woken from
2133 this state using a wakeup-capable RTC alarm.
2135 thash_entries= [KNL,NET]
2136 Set number of hash buckets for TCP connection
2138 thermal.act= [HW,ACPI]
2139 -1: disable all active trip points in all thermal zones
2140 <degrees C>: override all lowest active trip points
2142 thermal.crt= [HW,ACPI]
2143 -1: disable all critical trip points in all thermal zones
2144 <degrees C>: lower all critical trip points
2146 thermal.nocrt= [HW,ACPI]
2147 Set to disable actions on ACPI thermal zone
2148 critical and hot trip points.
2150 thermal.off= [HW,ACPI]
2151 1: disable ACPI thermal control
2153 thermal.psv= [HW,ACPI]
2154 -1: disable all passive trip points
2155 <degrees C>: override all passive trip points to this value
2157 thermal.tzp= [HW,ACPI]
2158 Specify global default ACPI thermal zone polling rate
2159 <deci-seconds>: poll all this frequency
2160 0: no polling (default)
2162 tmscsim= [HW,SCSI]
2163 See comment before function dc390_setup() in
2164 drivers/scsi/tmscsim.c.
2166 tp720= [HW,PS2]
2168 trix= [HW,OSS] MediaTrix AudioTrix Pro
2169 Format:
2170 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2172 turbografx.map[2|3]= [HW,JOY]
2173 TurboGraFX parallel port interface
2174 Format:
2175 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2176 See also Documentation/input/joystick-parport.txt
2178 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2179 See header of drivers/scsi/u14-34f.c.
2181 uart401= [HW,OSS]
2182 Format: <io>,<irq>
2184 uart6850= [HW,OSS]
2185 Format: <io>,<irq>
2187 uhci-hcd.ignore_oc=
2188 [USB] Ignore overcurrent events (default N).
2189 Some badly-designed motherboards generate lots of
2190 bogus events, for ports that aren't wired to
2191 anything. Set this parameter to avoid log spamming.
2192 Note that genuine overcurrent events won't be
2193 reported either.
2195 unknown_nmi_panic
2196 [X86-32,X86-64]
2197 Set unknown_nmi_panic=1 early on boot.
2199 usbcore.autosuspend=
2200 [USB] The autosuspend time delay (in seconds) used
2201 for newly-detected USB devices (default 2). This
2202 is the time required before an idle device will be
2203 autosuspended. Devices for which the delay is set
2204 to a negative value won't be autosuspended at all.
2206 usbhid.mousepoll=
2207 [USBHID] The interval which mice are to be polled at.
2209 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2210 kernel's map of available physical RAM.
2212 vdso= [X86-32,SH,x86-64]
2213 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2214 vdso=1: enable VDSO (default)
2215 vdso=0: disable VDSO mapping
2217 vdso32= [X86-32,X86-64]
2218 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2219 vdso32=1: enable 32-bit VDSO (default)
2220 vdso32=0: disable 32-bit VDSO mapping
2222 vector= [IA-64,SMP]
2223 vector=percpu: enable percpu vector domain
2225 video= [FB] Frame buffer configuration
2226 See Documentation/fb/modedb.txt.
2228 vga= [BOOT,X86-32] Select a particular video mode
2229 See Documentation/i386/boot.txt and
2230 Documentation/svga.txt.
2231 Use vga=ask for menu.
2232 This is actually a boot loader parameter; the value is
2233 passed to the kernel using a special protocol.
2235 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2236 size of <nn>. This can be used to increase the
2237 minimum size (128MB on x86). It can also be used to
2238 decrease the size and leave more room for directly
2239 mapped kernel RAM.
2241 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2242 Format: <command>
2244 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2245 Format: <command>
2247 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2248 Format: <command>
2250 waveartist= [HW,OSS]
2251 Format: <io>,<irq>,<dma>,<dma2>
2253 wd33c93= [HW,SCSI]
2254 See header of drivers/scsi/wd33c93.c.
2256 wd7000= [HW,SCSI]
2257 See header of drivers/scsi/wd7000.c.
2259 wdt= [WDT] Watchdog
2260 See Documentation/watchdog/wdt.txt.
2262 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2263 xd_geo= See header of drivers/block/xd.c.
2265 xirc2ps_cs= [NET,PCMCIA]
2266 Format:
2267 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2269 norandmaps Don't use address space randomization
2270 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2272 ______________________________________________________________________
2274 TODO:
2276 Add documentation for ALSA options.
2277 Add more DRM drivers.