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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AVR32 AVR32 architecture is enabled.
38 AX25 Appropriate AX.25 support is enabled.
39 BLACKFIN Blackfin architecture is enabled.
40 DRM Direct Rendering Management support is enabled.
41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
46 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
52 LIBATA Libata driver is enabled
53 LP Printer support is enabled.
54 LOOP Loopback device support is enabled.
55 M68k M68k architecture is enabled.
56 These options have more detailed description inside of
57 Documentation/m68k/kernel-options.txt.
58 MCA MCA bus support is enabled.
59 MDA MDA console support is enabled.
60 MOUSE Appropriate mouse support is enabled.
61 MSI Message Signaled Interrupts (PCI).
62 MTD MTD (Memory Technology Device) support is enabled.
63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
65 GENERIC_TIME The generic timeofday code is enabled.
66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
72 PCIE PCI Express support is enabled.
73 PCMCIA The PCMCIA subsystem is enabled.
74 PNP Plug & Play support is enabled.
75 PPC PowerPC architecture is enabled.
76 PPT Parallel port support is enabled.
77 PS2 Appropriate PS/2 support is enabled.
78 RAM RAM disk support is enabled.
79 ROOTPLUG The example Root Plug LSM is enabled.
80 S390 S390 architecture is enabled.
81 SCSI Appropriate SCSI support is enabled.
82 A lot of drivers has their options described inside of
83 Documentation/scsi/.
84 SECURITY Different security models are enabled.
85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
87 SH SuperH architecture is enabled.
88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
90 SWSUSP Software suspend is enabled.
91 TS Appropriate touchscreen support is enabled.
92 USB USB support is enabled.
93 USBHID USB Human Interface Device support is enabled.
94 V4L Video For Linux support is enabled.
95 VGA The VGA console has been enabled.
96 VT Virtual terminal support is enabled.
97 WDT Watchdog support is enabled.
98 XT IBM PC/XT MFM hard disk support is enabled.
99 X86-32 X86-32, aka i386 architecture is enabled.
100 X86-64 X86-64 architecture is enabled.
101 More X86-64 boot options can be found in
102 Documentation/x86_64/boot-options.txt .
104 In addition, the following text indicates that the option:
106 BUGS= Relates to possible processor bugs on the said processor.
107 KNL Is a kernel start-up parameter.
108 BOOT Is a boot loader parameter.
110 Parameters denoted with BOOT are actually interpreted by the boot
111 loader, and have no meaning to the kernel directly.
112 Do not modify the syntax of boot loader parameters without extreme
113 need or coordination with <Documentation/i386/boot.txt>.
115 There are also arch-specific kernel-parameters not documented here.
116 See for example <Documentation/x86_64/boot-options.txt>.
118 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
119 a trailing = on the name of any parameter states that that parameter will
120 be entered as an environment variable, whereas its absence indicates that
121 it will appear as a kernel argument readable via /proc/cmdline by programs
122 running once the system is up.
124 The number of kernel parameters is not limited, but the length of the
125 complete command line (parameters including spaces etc.) is limited to
126 a fixed number of characters. This limit depends on the architecture
127 and is between 256 and 4096 characters. It is defined in the file
128 ./include/asm/setup.h as COMMAND_LINE_SIZE.
131 acpi= [HW,ACPI,X86-64,i386]
132 Advanced Configuration and Power Interface
133 Format: { force | off | ht | strict | noirq }
134 force -- enable ACPI if default was off
135 off -- disable ACPI if default was on
136 noirq -- do not use ACPI for IRQ routing
137 ht -- run only enough ACPI to enable Hyper Threading
138 strict -- Be less tolerant of platforms that are not
139 strictly ACPI specification compliant.
141 See also Documentation/power/pm.txt, pci=noacpi
143 acpi_apic_instance= [ACPI, IOAPIC]
144 Format: <int>
145 2: use 2nd APIC table, if available
146 1,0: use 1st APIC table
147 default: 0
149 acpi_sleep= [HW,ACPI] Sleep options
150 Format: { s3_bios, s3_mode, s3_beep }
151 See Documentation/power/video.txt for s3_bios and s3_mode.
152 s3_beep is for debugging; it makes the PC's speaker beep
153 as soon as the kernel's real-mode entry point is called.
155 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
156 Format: { level | edge | high | low }
158 acpi_irq_balance [HW,ACPI]
159 ACPI will balance active IRQs
160 default in APIC mode
162 acpi_irq_nobalance [HW,ACPI]
163 ACPI will not move active IRQs (default)
164 default in PIC mode
166 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
167 use by PCI
168 Format: <irq>,<irq>...
170 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
171 Format: <irq>,<irq>...
173 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
175 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
176 Format: To spoof as Windows 98: ="Microsoft Windows"
178 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
179 acpi_osi="string1" # add string1 -- only one string
180 acpi_osi="!string2" # remove built-in string2
181 acpi_osi= # disable all strings
183 acpi_serialize [HW,ACPI] force serialization of AML methods
185 acpi_skip_timer_override [HW,ACPI]
186 Recognize and ignore IRQ0/pin2 Interrupt Override.
187 For broken nForce2 BIOS resulting in XT-PIC timer.
188 acpi_use_timer_override [HW,ACPI}
189 Use timer override. For some broken Nvidia NF5 boards
190 that require a timer override, but don't have
191 HPET
193 acpi.debug_layer= [HW,ACPI]
194 Format: <int>
195 Each bit of the <int> indicates an ACPI debug layer,
196 1: enable, 0: disable. It is useful for boot time
197 debugging. After system has booted up, it can be set
198 via /sys/module/acpi/parameters/debug_layer.
199 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
200 Available bits (add the numbers together) to enable debug output
201 for specific parts of the ACPI subsystem:
202 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
203 0x10 namespace 0x20 parser 0x40 dispatcher
204 0x80 executer 0x100 resources 0x200 acpica debugger
205 0x400 os services 0x800 acpica disassembler.
206 The number can be in decimal or prefixed with 0x in hex.
207 Warning: Many of these options can produce a lot of
208 output and make your system unusable. Be very careful.
210 acpi.debug_level= [HW,ACPI]
211 Format: <int>
212 Each bit of the <int> indicates an ACPI debug level,
213 1: enable, 0: disable. It is useful for boot time
214 debugging. After system has booted up, it can be set
215 via /sys/module/acpi/parameters/debug_level.
216 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
217 Available bits (add the numbers together) to enable different
218 debug output levels of the ACPI subsystem:
219 0x01 error 0x02 warn 0x04 init 0x08 debug object
220 0x10 info 0x20 init names 0x40 parse 0x80 load
221 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
222 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
223 0x10000 resources 0x20000 user requests 0x40000 package.
224 The number can be in decimal or prefixed with 0x in hex.
225 Warning: Many of these options can produce a lot of
226 output and make your system unusable. Be very careful.
228 acpi_pm_good [X86-32,X86-64]
229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
233 agp= [AGP]
234 { off | try_unsupported }
235 off: disable AGP support
236 try_unsupported: try to drive unsupported chipsets
237 (may crash computer or cause data corruption)
239 enable_timer_pin_1 [i386,x86-64]
240 Enable PIN 1 of APIC timer
241 Can be useful to work around chipset bugs
242 (in particular on some ATI chipsets).
243 The kernel tries to set a reasonable default.
245 disable_timer_pin_1 [i386,x86-64]
246 Disable PIN 1 of APIC timer
247 Can be useful to work around chipset bugs.
249 ad1848= [HW,OSS]
250 Format: <io>,<irq>,<dma>,<dma2>,<type>
252 advansys= [HW,SCSI]
253 See header of drivers/scsi/advansys.c.
255 advwdt= [HW,WDT] Advantech WDT
256 Format: <iostart>,<iostop>
258 aedsp16= [HW,OSS] Audio Excel DSP 16
259 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
260 See also header of sound/oss/aedsp16.c.
262 aha152x= [HW,SCSI]
263 See Documentation/scsi/aha152x.txt.
265 aha1542= [HW,SCSI]
266 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
268 aic7xxx= [HW,SCSI]
269 See Documentation/scsi/aic7xxx.txt.
271 aic79xx= [HW,SCSI]
272 See Documentation/scsi/aic79xx.txt.
274 amijoy.map= [HW,JOY] Amiga joystick support
275 Map of devices attached to JOY0DAT and JOY1DAT
276 Format: <a>,<b>
277 See also Documentation/kernel/input/joystick.txt
279 analog.map= [HW,JOY] Analog joystick and gamepad support
280 Specifies type or capabilities of an analog joystick
281 connected to one of 16 gameports
282 Format: <type1>,<type2>,..<type16>
284 apc= [HW,SPARC]
285 Power management functions (SPARCstation-4/5 + deriv.)
286 Format: noidle
287 Disable APC CPU standby support. SPARCstation-Fox does
288 not play well with APC CPU idle - disable it if you have
289 APC and your system crashes randomly.
291 apic= [APIC,i386] Advanced Programmable Interrupt Controller
292 Change the output verbosity whilst booting
293 Format: { quiet (default) | verbose | debug }
294 Change the amount of debugging information output
295 when initialising the APIC and IO-APIC components.
297 apm= [APM] Advanced Power Management
298 See header of arch/i386/kernel/apm.c.
300 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
301 Format: <io>,<irq>,<nodeID>
303 ataflop= [HW,M68k]
305 atarimouse= [HW,MOUSE] Atari Mouse
307 atascsi= [HW,SCSI] Atari SCSI
309 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
310 EzKey and similar keyboards
312 atkbd.reset= [HW] Reset keyboard during initialization
314 atkbd.set= [HW] Select keyboard code set
315 Format: <int> (2 = AT (default), 3 = PS/2)
317 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
318 keyboards
320 atkbd.softraw= [HW] Choose between synthetic and real raw mode
321 Format: <bool> (0 = real, 1 = synthetic (default))
323 atkbd.softrepeat= [HW]
324 Use software keyboard repeat
326 autotest [IA64]
328 baycom_epp= [HW,AX25]
329 Format: <io>,<mode>
331 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
332 Format: <io>,<mode>
333 See header of drivers/net/hamradio/baycom_par.c.
335 baycom_ser_fdx= [HW,AX25]
336 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
337 Format: <io>,<irq>,<mode>[,<baud>]
338 See header of drivers/net/hamradio/baycom_ser_fdx.c.
340 baycom_ser_hdx= [HW,AX25]
341 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
342 Format: <io>,<irq>,<mode>
343 See header of drivers/net/hamradio/baycom_ser_hdx.c.
345 boot_delay= Milliseconds to delay each printk during boot.
346 Values larger than 10 seconds (10000) are changed to
347 no delay (0).
348 Format: integer
350 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
351 bttv.radio= Most important insmod options are available as
352 kernel args too.
353 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
354 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
356 BusLogic= [HW,SCSI]
357 See drivers/scsi/BusLogic.c, comment before function
358 BusLogic_ParseDriverOptions().
360 c101= [NET] Moxa C101 synchronous serial card
362 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
363 Sometimes CPU hardware bugs make them report the cache
364 size incorrectly. The kernel will attempt work arounds
365 to fix known problems, but for some CPUs it is not
366 possible to determine what the correct size should be.
367 This option provides an override for these situations.
369 capability.disable=
370 [SECURITY] Disable capabilities. This would normally
371 be used only if an alternative security model is to be
372 configured. Potentially dangerous and should only be
373 used if you are entirely sure of the consequences.
375 ccw_timeout_log [S390]
376 See Documentation/s390/CommonIO for details.
378 cgroup_disable= [KNL] Disable a particular controller
379 Format: {name of the controller(s) to disable}
380 {Currently supported controllers - "memory"}
382 checkreqprot [SELINUX] Set initial checkreqprot flag value.
383 Format: { "0" | "1" }
384 See security/selinux/Kconfig help text.
385 0 -- check protection applied by kernel (includes
386 any implied execute protection).
387 1 -- check protection requested by application.
388 Default value is set via a kernel config option.
389 Value can be changed at runtime via
390 /selinux/checkreqprot.
392 cio_ignore= [S390]
393 See Documentation/s390/CommonIO for details.
395 cio_msg= [S390]
396 See Documentation/s390/CommonIO for details.
398 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
399 [Deprecated]
400 Forces specified clocksource (if available) to be used
401 when calculating gettimeofday(). If specified
402 clocksource is not available, it defaults to PIT.
403 Format: { pit | tsc | cyclone | pmtmr }
405 clocksource= [GENERIC_TIME] Override the default clocksource
406 Format: <string>
407 Override the default clocksource and use the clocksource
408 with the name specified.
409 Some clocksource names to choose from, depending on
410 the platform:
411 [all] jiffies (this is the base, fallback clocksource)
412 [ACPI] acpi_pm
413 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
414 pxa_timer,timer3,32k_counter,timer0_1
415 [AVR32] avr32
416 [X86-32] pit,hpet,tsc,vmi-timer;
417 scx200_hrt on Geode; cyclone on IBM x440
418 [MIPS] MIPS
419 [PARISC] cr16
420 [S390] tod
421 [SH] SuperH
422 [SPARC64] tick
423 [X86-64] hpet,tsc
425 clearcpuid=BITNUM [X86]
426 Disable CPUID feature X for the kernel. See
427 include/asm-x86/cpufeature.h for the valid bit numbers.
428 Note the Linux specific bits are not necessarily
429 stable over kernel options, but the vendor specific
430 ones should be.
431 Also note that user programs calling CPUID directly
432 or using the feature without checking anything
433 will still see it. This just prevents it from
434 being used by the kernel or shown in /proc/cpuinfo.
435 Also note the kernel might malfunction if you disable
436 some critical bits.
438 code_bytes [IA32/X86_64] How many bytes of object code to print
439 in an oops report.
440 Range: 0 - 8192
441 Default: 64
443 disable_8254_timer
444 enable_8254_timer
445 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
446 over the 8254 in addition to over the IO-APIC. The
447 kernel tries to set a sensible default.
449 hpet= [X86-32,HPET] option to control HPET usage
450 Format: { enable (default) | disable | force }
451 disable: disable HPET and use PIT instead
452 force: allow force enabled of undocumented chips (ICH4,
453 VIA, nVidia)
455 com20020= [HW,NET] ARCnet - COM20020 chipset
456 Format:
457 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
459 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
460 Format: <io>[,<irq>]
462 com90xx= [HW,NET]
463 ARCnet - COM90xx chipset (memory-mapped buffers)
464 Format: <io>[,<irq>[,<memstart>]]
466 condev= [HW,S390] console device
467 conmode=
469 console= [KNL] Output console device and options.
471 tty<n> Use the virtual console device <n>.
473 ttyS<n>[,options]
474 ttyUSB0[,options]
475 Use the specified serial port. The options are of
476 the form "bbbbpnf", where "bbbb" is the baud rate,
477 "p" is parity ("n", "o", or "e"), "n" is number of
478 bits, and "f" is flow control ("r" for RTS or
479 omit it). Default is "9600n8".
481 See Documentation/serial-console.txt for more
482 information. See
483 Documentation/networking/netconsole.txt for an
484 alternative.
486 uart[8250],io,<addr>[,options]
487 uart[8250],mmio,<addr>[,options]
488 Start an early, polled-mode console on the 8250/16550
489 UART at the specified I/O port or MMIO address,
490 switching to the matching ttyS device later. The
491 options are the same as for ttyS, above.
493 earlycon= [KNL] Output early console device and options.
494 uart[8250],io,<addr>[,options]
495 uart[8250],mmio,<addr>[,options]
496 Start an early, polled-mode console on the 8250/16550
497 UART at the specified I/O port or MMIO address.
498 The options are the same as for ttyS, above.
500 no_console_suspend
501 [HW] Never suspend the console
502 Disable suspending of consoles during suspend and
503 hibernate operations. Once disabled, debugging
504 messages can reach various consoles while the rest
505 of the system is being put to sleep (ie, while
506 debugging driver suspend/resume hooks). This may
507 not work reliably with all consoles, but is known
508 to work with serial and VGA consoles.
510 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
511 Format:
512 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
514 crashkernel=nn[KMG]@ss[KMG]
515 [KNL] Reserve a chunk of physical memory to
516 hold a kernel to switch to with kexec on panic.
518 crashkernel=range1:size1[,range2:size2,...][@offset]
519 [KNL] Same as above, but depends on the memory
520 in the running system. The syntax of range is
521 start-[end] where start and end are both
522 a memory unit (amount[KMG]). See also
523 Documentation/kdump/kdump.txt for a example.
525 cs4232= [HW,OSS]
526 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
528 cs89x0_dma= [HW,NET]
529 Format: <dma>
531 cs89x0_media= [HW,NET]
532 Format: { rj45 | aui | bnc }
534 dasd= [HW,NET]
535 See header of drivers/s390/block/dasd_devmap.c.
537 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
538 (one device per port)
539 Format: <port#>,<type>
540 See also Documentation/input/joystick-parport.txt
542 debug [KNL] Enable kernel debugging (events log level).
544 debug_locks_verbose=
545 [KNL] verbose self-tests
546 Format=<0|1>
547 Print debugging info while doing the locking API
548 self-tests.
549 We default to 0 (no extra messages), setting it to
550 1 will print _a lot_ more information - normally
551 only useful to kernel developers.
553 decnet.addr= [HW,NET]
554 Format: <area>[,<node>]
555 See also Documentation/networking/decnet.txt.
557 vt.default_blu= [VT]
558 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
559 Change the default blue palette of the console.
560 This is a 16-member array composed of values
561 ranging from 0-255.
563 vt.default_grn= [VT]
564 Format: <green0>,<green1>,<green2>,...,<green15>
565 Change the default green palette of the console.
566 This is a 16-member array composed of values
567 ranging from 0-255.
569 vt.default_red= [VT]
570 Format: <red0>,<red1>,<red2>,...,<red15>
571 Change the default red palette of the console.
572 This is a 16-member array composed of values
573 ranging from 0-255.
575 vt.default_utf8=
576 [VT]
577 Format=<0|1>
578 Set system-wide default UTF-8 mode for all tty's.
579 Default is 1, i.e. UTF-8 mode is enabled for all
580 newly opened terminals.
582 dhash_entries= [KNL]
583 Set number of hash buckets for dentry cache.
585 digi= [HW,SERIAL]
586 IO parameters + enable/disable command.
588 digiepca= [HW,SERIAL]
589 See drivers/char/README.epca and
590 Documentation/digiepca.txt.
592 disable_mtrr_trim [X86, Intel and AMD only]
593 By default the kernel will trim any uncacheable
594 memory out of your available memory pool based on
595 MTRR settings. This parameter disables that behavior,
596 possibly causing your machine to run very slowly.
598 dmasound= [HW,OSS] Sound subsystem buffers
600 dscc4.setup= [NET]
602 dtc3181e= [HW,SCSI]
604 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
605 earlyprintk=vga
606 earlyprintk=serial[,ttySn[,baudrate]]
608 Append ",keep" to not disable it when the real console
609 takes over.
611 Only vga or serial at a time, not both.
613 Currently only ttyS0 and ttyS1 are supported.
615 Interaction with the standard serial driver is not
616 very good.
618 The VGA output is eventually overwritten by the real
619 console.
621 eata= [HW,SCSI]
623 edd= [EDD]
624 Format: {"of[f]" | "sk[ipmbr]"}
625 See comment in arch/i386/boot/edd.S
627 eisa_irq_edge= [PARISC,HW]
628 See header of drivers/parisc/eisa.c.
630 elanfreq= [X86-32]
631 See comment before function elanfreq_setup() in
632 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
634 elevator= [IOSCHED]
635 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
636 See Documentation/block/as-iosched.txt and
637 Documentation/block/deadline-iosched.txt for details.
639 elfcorehdr= [X86-32, X86_64]
640 Specifies physical address of start of kernel core
641 image elf header. Generally kexec loader will
642 pass this option to capture kernel.
643 See Documentation/kdump/kdump.txt for details.
645 enforcing [SELINUX] Set initial enforcing status.
646 Format: {"0" | "1"}
647 See security/selinux/Kconfig help text.
648 0 -- permissive (log only, no denials).
649 1 -- enforcing (deny and log).
650 Default value is 0.
651 Value can be changed at runtime via /selinux/enforce.
653 es1371= [HW,OSS]
654 Format: <spdif>,[<nomix>,[<amplifier>]]
655 See also header of sound/oss/es1371.c.
657 ether= [HW,NET] Ethernet cards parameters
658 This option is obsoleted by the "netdev=" option, which
659 has equivalent usage. See its documentation for details.
661 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
662 Format: <io>[,<irq>]
664 failslab=
665 fail_page_alloc=
666 fail_make_request=[KNL]
667 General fault injection mechanism.
668 Format: <interval>,<probability>,<space>,<times>
669 See also /Documentation/fault-injection/.
671 fd_mcs= [HW,SCSI]
672 See header of drivers/scsi/fd_mcs.c.
674 fdomain= [HW,SCSI]
675 See header of drivers/scsi/fdomain.c.
677 floppy= [HW]
678 See Documentation/floppy.txt.
680 gamecon.map[2|3]=
681 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
682 support via parallel port (up to 5 devices per port)
683 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
684 See also Documentation/input/joystick-parport.txt
686 gamma= [HW,DRM]
688 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
689 Format: off | on
690 default: on
692 gdth= [HW,SCSI]
693 See header of drivers/scsi/gdth.c.
695 gpt [EFI] Forces disk with valid GPT signature but
696 invalid Protective MBR to be treated as GPT.
698 gvp11= [HW,SCSI]
700 hashdist= [KNL,NUMA] Large hashes allocated during boot
701 are distributed across NUMA nodes. Defaults on
702 for IA-64, off otherwise.
703 Format: 0 | 1 (for off | on)
705 hcl= [IA-64] SGI's Hardware Graph compatibility layer
707 hd= [EIDE] (E)IDE hard drive subsystem geometry
708 Format: <cyl>,<head>,<sect>
710 hd?= [HW] (E)IDE subsystem
711 hd?lun= See Documentation/ide/ide.txt.
713 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
714 size of <nn>. This works even on boxes that have no
715 highmem otherwise. This also works to reduce highmem
716 size on bigger boxes.
718 highres= [KNL] Enable/disable high resolution timer mode.
719 Valid parameters: "on", "off"
720 Default: "on"
722 hisax= [HW,ISDN]
723 See Documentation/isdn/README.HiSax.
725 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
726 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
728 i8042.direct [HW] Put keyboard port into non-translated mode
729 i8042.dumbkbd [HW] Pretend that controller can only read data from
730 keyboard and cannot control its state
731 (Don't attempt to blink the leds)
732 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
733 i8042.nokbd [HW] Don't check/create keyboard port
734 i8042.noloop [HW] Disable the AUX Loopback command while probing
735 for the AUX port
736 i8042.nomux [HW] Don't check presence of an active multiplexing
737 controller
738 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
739 controllers
740 i8042.panicblink=
741 [HW] Frequency with which keyboard LEDs should blink
742 when kernel panics (default is 0.5 sec)
743 i8042.reset [HW] Reset the controller during init and cleanup
744 i8042.unlock [HW] Unlock (ignore) the keylock
746 i810= [HW,DRM]
748 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
749 indicates that the driver is running on unsupported
750 hardware.
751 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
752 does not match list of supported models.
753 i8k.power_status
754 [HW] Report power status in /proc/i8k
755 (disabled by default)
756 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
757 capability is set.
759 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
760 See Documentation/mca.txt.
762 icn= [HW,ISDN]
763 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
765 ide= [HW] (E)IDE subsystem
766 Format: ide=nodma or ide=doubler or ide=reverse
767 See Documentation/ide/ide.txt.
769 ide?= [HW] (E)IDE subsystem
770 Format: ide?=noprobe or chipset specific parameters.
771 See Documentation/ide/ide.txt.
773 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
774 See Documentation/ide/ide.txt.
776 idle= [X86]
777 Format: idle=poll or idle=mwait
778 Poll forces a polling idle loop that can slightly improves the performance
779 of waking up a idle CPU, but will use a lot of power and make the system
780 run hot. Not recommended.
781 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
782 to not use it because it doesn't save as much power as a normal idle
783 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
784 as idle=poll.
786 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
787 Claim all unknown PCI IDE storage controllers.
789 ignore_loglevel [KNL]
790 Ignore loglevel setting - this will print /all/
791 kernel messages to the console. Useful for debugging.
793 ihash_entries= [KNL]
794 Set number of hash buckets for inode cache.
796 in2000= [HW,SCSI]
797 See header of drivers/scsi/in2000.c.
799 init= [KNL]
800 Format: <full_path>
801 Run specified binary instead of /sbin/init as init
802 process.
804 initcall_debug [KNL] Trace initcalls as they are executed. Useful
805 for working out where the kernel is dying during
806 startup.
808 initrd= [BOOT] Specify the location of the initial ramdisk
810 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
811 Format: <irq>
813 inttest= [IA64]
815 iommu= [x86]
816 off
817 force
818 noforce
819 biomerge
820 panic
821 nopanic
822 merge
823 nomerge
824 forcesac
825 soft
828 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
829 off
830 Disable intel iommu driver.
831 igfx_off [Default Off]
832 By default, gfx is mapped as normal device. If a gfx
833 device has a dedicated DMAR unit, the DMAR unit is
834 bypassed by not enabling DMAR with this option. In
835 this case, gfx device will use physical address for
836 DMA.
837 forcedac [x86_64]
838 With this option iommu will not optimize to look
839 for io virtual address below 32 bit forcing dual
840 address cycle on pci bus for cards supporting greater
841 than 32 bit addressing. The default is to look
842 for translation below 32 bit and if not available
843 then look in the higher range.
845 io_delay= [X86-32,X86-64] I/O delay method
846 0x80
847 Standard port 0x80 based delay
848 0xed
849 Alternate port 0xed based delay (needed on some systems)
850 udelay
851 Simple two microseconds delay
852 none
853 No delay
855 io7= [HW] IO7 for Marvel based alpha systems
856 See comment before marvel_specify_io7 in
857 arch/alpha/kernel/core_marvel.c.
859 ip= [IP_PNP]
860 See Documentation/filesystems/nfsroot.txt.
862 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
863 See comment before ip2_setup() in
864 drivers/char/ip2/ip2base.c.
866 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
867 See header of drivers/scsi/ips.c.
869 ports= [IP_VS_FTP] IPVS ftp helper module
870 Default is 21.
871 Up to 8 (IP_VS_APP_MAX_PORTS) ports
872 may be specified.
873 Format: <port>,<port>....
875 irqfixup [HW]
876 When an interrupt is not handled search all handlers
877 for it. Intended to get systems with badly broken
878 firmware running.
880 irqpoll [HW]
881 When an interrupt is not handled search all handlers
882 for it. Also check all handlers each timer
883 interrupt. Intended to get systems with badly broken
884 firmware running.
886 isapnp= [ISAPNP]
887 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
889 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
890 Format:
891 <cpu number>,...,<cpu number>
892 or
893 <cpu number>-<cpu number> (must be a positive range in ascending order)
894 or a mixture
895 <cpu number>,...,<cpu number>-<cpu number>
896 This option can be used to specify one or more CPUs
897 to isolate from the general SMP balancing and scheduling
898 algorithms. The only way to move a process onto or off
899 an "isolated" CPU is via the CPU affinity syscalls.
900 <cpu number> begins at 0 and the maximum value is
901 "number of CPUs in system - 1".
903 This option is the preferred way to isolate CPUs. The
904 alternative -- manually setting the CPU mask of all
905 tasks in the system -- can cause problems and
906 suboptimal load balancer performance.
908 iucv= [HW,NET]
910 js= [HW,JOY] Analog joystick
911 See Documentation/input/joystick.txt.
913 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
914 specifies the amount of memory usable by the kernel
915 for non-movable allocations. The requested amount is
916 spread evenly throughout all nodes in the system. The
917 remaining memory in each node is used for Movable
918 pages. In the event, a node is too small to have both
919 kernelcore and Movable pages, kernelcore pages will
920 take priority and other nodes will have a larger number
921 of kernelcore pages. The Movable zone is used for the
922 allocation of pages that may be reclaimed or moved
923 by the page migration subsystem. This means that
924 HugeTLB pages may not be allocated from this zone.
925 Note that allocations like PTEs-from-HighMem still
926 use the HighMem zone if it exists, and the Normal
927 zone if it does not.
929 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
930 is similar to kernelcore except it specifies the
931 amount of memory used for migratable allocations.
932 If both kernelcore and movablecore is specified,
933 then kernelcore will be at *least* the specified
934 value but may be more. If movablecore on its own
935 is specified, the administrator must be careful
936 that the amount of memory usable for all allocations
937 is not too small.
939 keepinitrd [HW,ARM]
941 kstack=N [X86-32,X86-64] Print N words from the kernel stack
942 in oops dumps.
944 l2cr= [PPC]
946 lapic [X86-32,APIC] Enable the local APIC even if BIOS
947 disabled it.
949 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
950 C2 power state.
952 libata.dma= [LIBATA] DMA control
953 libata.dma=0 Disable all PATA and SATA DMA
954 libata.dma=1 PATA and SATA Disk DMA only
955 libata.dma=2 ATAPI (CDROM) DMA only
956 libata.dma=4 Compact Flash DMA only
957 Combinations also work, so libata.dma=3 enables DMA
958 for disks and CDROMs, but not CFs.
960 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
961 when set.
962 Format: <int>
964 libata.force= [LIBATA] Force configurations. The format is comma
965 separated list of "[ID:]VAL" where ID is
966 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
967 matching port, link or device. Basically, it matches
968 the ATA ID string printed on console by libata. If
969 the whole ID part is omitted, the last PORT and DEVICE
970 values are used. If ID hasn't been specified yet, the
971 configuration applies to all ports, links and devices.
973 If only DEVICE is omitted, the parameter applies to
974 the port and all links and devices behind it. DEVICE
975 number of 0 either selects the first device or the
976 first fan-out link behind PMP device. It does not
977 select the host link. DEVICE number of 15 selects the
978 host link and device attached to it.
980 The VAL specifies the configuration to force. As long
981 as there's no ambiguity shortcut notation is allowed.
982 For example, both 1.5 and 1.5G would work for 1.5Gbps.
983 The following configurations can be forced.
985 * Cable type: 40c, 80c, short40c, unk, ign or sata.
986 Any ID with matching PORT is used.
988 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
990 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
991 udma[/][16,25,33,44,66,100,133] notation is also
992 allowed.
994 * [no]ncq: Turn on or off NCQ.
996 If there are multiple matching configurations changing
997 the same attribute, the last one is used.
999 load_ramdisk= [RAM] List of ramdisks to load from floppy
1000 See Documentation/ramdisk.txt.
1002 lockd.nlm_grace_period=P [NFS] Assign grace period.
1003 Format: <integer>
1005 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1006 Format: <integer>
1008 lockd.nlm_timeout=T [NFS] Assign timeout value.
1009 Format: <integer>
1011 lockd.nlm_udpport=M [NFS] Assign UDP port.
1012 Format: <integer>
1014 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1015 Format: <irq>
1017 loglevel= All Kernel Messages with a loglevel smaller than the
1018 console loglevel will be printed to the console. It can
1019 also be changed with klogd or other programs. The
1020 loglevels are defined as follows:
1022 0 (KERN_EMERG) system is unusable
1023 1 (KERN_ALERT) action must be taken immediately
1024 2 (KERN_CRIT) critical conditions
1025 3 (KERN_ERR) error conditions
1026 4 (KERN_WARNING) warning conditions
1027 5 (KERN_NOTICE) normal but significant condition
1028 6 (KERN_INFO) informational
1029 7 (KERN_DEBUG) debug-level messages
1031 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1032 Format: { n | nk | nM }
1033 n must be a power of two. The default size
1034 is set in the kernel config file.
1036 logo.nologo [FB] Disables display of the built-in Linux logo.
1037 This may be used to provide more screen space for
1038 kernel log messages and is useful when debugging
1039 kernel boot problems.
1041 lp=0 [LP] Specify parallel ports to use, e.g,
1042 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1043 lp=reset first parallel port). 'lp=0' disables the
1044 lp=auto printer driver. 'lp=reset' (which can be
1045 specified in addition to the ports) causes
1046 attached printers to be reset. Using
1047 lp=port1,port2,... specifies the parallel ports
1048 to associate lp devices with, starting with
1049 lp0. A port specification may be 'none' to skip
1050 that lp device, or a parport name such as
1051 'parport0'. Specifying 'lp=auto' instead of a
1052 port specification list means that device IDs
1053 from each port should be examined, to see if
1054 an IEEE 1284-compliant printer is attached; if
1055 so, the driver will manage that printer.
1056 See also header of drivers/char/lp.c.
1058 lpj=n [KNL]
1059 Sets loops_per_jiffy to given constant, thus avoiding
1060 time-consuming boot-time autodetection (up to 250 ms per
1061 CPU). 0 enables autodetection (default). To determine
1062 the correct value for your kernel, boot with normal
1063 autodetection and see what value is printed. Note that
1064 on SMP systems the preset will be applied to all CPUs,
1065 which is likely to cause problems if your CPUs need
1066 significantly divergent settings. An incorrect value
1067 will cause delays in the kernel to be wrong, leading to
1068 unpredictable I/O errors and other breakage. Although
1069 unlikely, in the extreme case this might damage your
1070 hardware.
1072 ltpc= [NET]
1073 Format: <io>,<irq>,<dma>
1075 mac5380= [HW,SCSI] Format:
1076 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1078 mac53c9x= [HW,SCSI] Format:
1079 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1081 machvec= [IA64] Force the use of a particular machine-vector
1082 (machvec) in a generic kernel.
1083 Example: machvec=hpzx1_swiotlb
1085 max_loop= [LOOP] Maximum number of loopback devices that can
1086 be mounted
1087 Format: <1-256>
1089 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1090 should make use of. maxcpus=n : n >= 0 limits the
1091 kernel to using 'n' processors. n=0 is a special case,
1092 it is equivalent to "nosmp", which also disables
1093 the IO APIC.
1095 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1096 equal to this physical address is ignored.
1098 max_luns= [SCSI] Maximum number of LUNs to probe.
1099 Should be between 1 and 2^32-1.
1101 max_report_luns=
1102 [SCSI] Maximum number of LUNs received.
1103 Should be between 1 and 16384.
1105 mcatest= [IA-64]
1107 mce [X86-32] Machine Check Exception
1109 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1111 md= [HW] RAID subsystems devices and level
1112 See Documentation/md.txt.
1114 mdacon= [MDA]
1115 Format: <first>,<last>
1116 Specifies range of consoles to be captured by the MDA.
1118 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1119 Amount of memory to be used when the kernel is not able
1120 to see the whole system memory or for test.
1121 [X86-32] Use together with memmap= to avoid physical
1122 address space collisions. Without memmap= PCI devices
1123 could be placed at addresses belonging to unused RAM.
1125 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1126 memory.
1128 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1129 E820 memory map, as specified by the user.
1130 Such memmap=exactmap lines can be constructed based on
1131 BIOS output or other requirements. See the memmap=nn@ss
1132 option description.
1134 memmap=nn[KMG]@ss[KMG]
1135 [KNL] Force usage of a specific region of memory
1136 Region of memory to be used, from ss to ss+nn.
1138 memmap=nn[KMG]#ss[KMG]
1139 [KNL,ACPI] Mark specific memory as ACPI data.
1140 Region of memory to be used, from ss to ss+nn.
1142 memmap=nn[KMG]$ss[KMG]
1143 [KNL,ACPI] Mark specific memory as reserved.
1144 Region of memory to be used, from ss to ss+nn.
1145 Example: Exclude memory from 0x18690000-0x1869ffff
1146 memmap=64K$0x18690000
1147 or
1148 memmap=0x10000$0x18690000
1150 memtest= [KNL,X86_64] Enable memtest
1151 Format: <integer>
1152 range: 0,4 : pattern number
1153 default : 0 <disable>
1155 meye.*= [HW] Set MotionEye Camera parameters
1156 See Documentation/video4linux/meye.txt.
1158 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1159 Multi-Function General Purpose Timers on AMD Geode
1160 platforms.
1162 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1163 the BIOS has incorrectly applied a workaround. TinyBIOS
1164 version 0.98 is known to be affected, 0.99 fixes the
1165 problem by letting the user disable the workaround.
1167 mga= [HW,DRM]
1169 mousedev.tap_time=
1170 [MOUSE] Maximum time between finger touching and
1171 leaving touchpad surface for touch to be considered
1172 a tap and be reported as a left button click (for
1173 touchpads working in absolute mode only).
1174 Format: <msecs>
1175 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1176 reporting absolute coordinates, such as tablets
1177 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1178 reporting absolute coordinates, such as tablets
1180 mpu401= [HW,OSS]
1181 Format: <io>,<irq>
1183 MTD_Partition= [MTD]
1184 Format: <name>,<region-number>,<size>,<offset>
1186 MTD_Region= [MTD] Format:
1187 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1189 mtdparts= [MTD]
1190 See drivers/mtd/cmdlinepart.c.
1192 mtouchusb.raw_coordinates=
1193 [HW] Make the MicroTouch USB driver use raw coordinates
1194 ('y', default) or cooked coordinates ('n')
1196 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1198 NCR_D700= [HW,SCSI]
1199 See header of drivers/scsi/NCR_D700.c.
1201 ncr5380= [HW,SCSI]
1203 ncr53c400= [HW,SCSI]
1205 ncr53c400a= [HW,SCSI]
1207 ncr53c406a= [HW,SCSI]
1209 ncr53c8xx= [HW,SCSI]
1211 netdev= [NET] Network devices parameters
1212 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1213 Note that mem_start is often overloaded to mean
1214 something different and driver-specific.
1215 This usage is only documented in each driver source
1216 file if at all.
1218 nfsaddrs= [NFS]
1219 See Documentation/filesystems/nfsroot.txt.
1221 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1222 See Documentation/filesystems/nfsroot.txt.
1224 nfs.callback_tcpport=
1225 [NFS] set the TCP port on which the NFSv4 callback
1226 channel should listen.
1228 nfs.idmap_cache_timeout=
1229 [NFS] set the maximum lifetime for idmapper cache
1230 entries.
1232 nfs.enable_ino64=
1233 [NFS] enable 64-bit inode numbers.
1234 If zero, the NFS client will fake up a 32-bit inode
1235 number for the readdir() and stat() syscalls instead
1236 of returning the full 64-bit number.
1237 The default is to return 64-bit inode numbers.
1239 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1240 when a NMI is triggered.
1241 Format: [state][,regs][,debounce][,die]
1243 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1245 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1246 emulation library even if a 387 maths coprocessor
1247 is present.
1249 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1250 caches in the slab allocator. Saves per-node memory,
1251 but will impact performance.
1253 noalign [KNL,ARM]
1255 noapic [SMP,APIC] Tells the kernel to not make use of any
1256 IOAPICs that may be present in the system.
1258 nobats [PPC] Do not use BATs for mapping kernel lowmem
1259 on "Classic" PPC cores.
1261 nocache [ARM]
1263 nodelayacct [KNL] Disable per-task delay accounting
1265 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1267 noefi [X86-32,X86-64] Disable EFI runtime services support.
1269 noexec [IA-64]
1271 noexec [X86-32,X86-64]
1272 noexec=on: enable non-executable mappings (default)
1273 noexec=off: disable nn-executable mappings
1275 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1276 register save and restore. The kernel will only save
1277 legacy floating-point registers on task switch.
1279 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1281 nohlt [BUGS=ARM]
1283 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1284 instruction doesn't work correctly and not to
1285 use it.
1287 nohalt [IA-64] Tells the kernel not to use the power saving
1288 function PAL_HALT_LIGHT when idle. This increases
1289 power-consumption. On the positive side, it reduces
1290 interrupt wake-up latency, which may improve performance
1291 in certain environments such as networked servers or
1292 real-time systems.
1294 nohz= [KNL] Boottime enable/disable dynamic ticks
1295 Valid arguments: on, off
1296 Default: on
1298 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1300 noirqdebug [X86-32] Disables the code which attempts to detect and
1301 disable unhandled interrupt sources.
1303 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1304 broken timer IRQ sources.
1306 noisapnp [ISAPNP] Disables ISA PnP code.
1308 noinitrd [RAM] Tells the kernel not to load any configured
1309 initial RAM disk.
1311 nointroute [IA-64]
1313 nojitter [IA64] Disables jitter checking for ITC timers.
1315 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1317 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1319 noltlbs [PPC] Do not use large page/tlb entries for kernel
1320 lowmem mapping on PPC40x.
1322 nomca [IA-64] Disable machine check abort handling
1324 nomce [X86-32] Machine Check Exception
1326 nomfgpt [X86-32] Disable Multi-Function General Purpose
1327 Timer usage (for AMD Geode machines).
1329 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1331 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1332 with UP alternatives
1334 noresidual [PPC] Don't use residual data on PReP machines.
1336 noresume [SWSUSP] Disables resume and restores original swap
1337 space.
1339 no-scroll [VGA] Disables scrollback.
1340 This is required for the Braillex ib80-piezo Braille
1341 reader made by F.H. Papenmeier (Germany).
1343 nosbagart [IA-64]
1345 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1347 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1348 and disable the IO APIC. legacy for "maxcpus=0".
1350 nosoftlockup [KNL] Disable the soft-lockup detector.
1352 nosync [HW,M68K] Disables sync negotiation for all devices.
1354 notsc [BUGS=X86-32] Disable Time Stamp Counter
1356 nousb [USB] Disable the USB subsystem
1358 nowb [ARM]
1360 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1361 one of ['zone', 'node', 'default'] can be specified
1362 This can be set from sysctl after boot.
1363 See Documentation/sysctl/vm.txt for details.
1365 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1367 opl3= [HW,OSS]
1368 Format: <io>
1370 oprofile.timer= [HW]
1371 Use timer interrupt instead of performance counters
1373 osst= [HW,SCSI] SCSI Tape Driver
1374 Format: <buffer_size>,<write_threshold>
1375 See also Documentation/scsi/st.txt.
1377 panic= [KNL] Kernel behaviour on panic
1378 Format: <timeout>
1380 parkbd.port= [HW] Parallel port number the keyboard adapter is
1381 connected to, default is 0.
1382 Format: <parport#>
1383 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1384 0 for XT, 1 for AT (default is AT).
1385 Format: <mode>
1387 parport= [HW,PPT] Specify parallel ports. 0 disables.
1388 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1389 Use 'auto' to force the driver to use any
1390 IRQ/DMA settings detected (the default is to
1391 ignore detected IRQ/DMA settings because of
1392 possible conflicts). You can specify the base
1393 address, IRQ, and DMA settings; IRQ and DMA
1394 should be numbers, or 'auto' (for using detected
1395 settings on that particular port), or 'nofifo'
1396 (to avoid using a FIFO even if it is detected).
1397 Parallel ports are assigned in the order they
1398 are specified on the command line, starting
1399 with parport0.
1401 parport_init_mode= [HW,PPT]
1402 Configure VIA parallel port to operate in
1403 a specific mode. This is necessary on Pegasos
1404 computer where firmware has no options for setting
1405 up parallel port mode and sets it to spp.
1406 Currently this function knows 686a and 8231 chips.
1407 Format: [spp|ps2|epp|ecp|ecpepp]
1409 pas2= [HW,OSS] Format:
1410 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1412 pas16= [HW,SCSI]
1413 See header of drivers/scsi/pas16.c.
1415 pause_on_oops=
1416 Halt all CPUs after the first oops has been printed for
1417 the specified number of seconds. This is to be used if
1418 your oopses keep scrolling off the screen.
1420 pcbit= [HW,ISDN]
1422 pcd. [PARIDE]
1423 See header of drivers/block/paride/pcd.c.
1424 See also Documentation/paride.txt.
1426 pci=option[,option...] [PCI] various PCI subsystem options:
1427 off [X86-32] don't probe for the PCI bus
1428 bios [X86-32] force use of PCI BIOS, don't access
1429 the hardware directly. Use this if your machine
1430 has a non-standard PCI host bridge.
1431 nobios [X86-32] disallow use of PCI BIOS, only direct
1432 hardware access methods are allowed. Use this
1433 if you experience crashes upon bootup and you
1434 suspect they are caused by the BIOS.
1435 conf1 [X86-32] Force use of PCI Configuration
1436 Mechanism 1.
1437 conf2 [X86-32] Force use of PCI Configuration
1438 Mechanism 2.
1439 noaer [PCIE] If the PCIEAER kernel config parameter is
1440 enabled, this kernel boot option can be used to
1441 disable the use of PCIE advanced error reporting.
1442 nodomains [PCI] Disable support for multiple PCI
1443 root domains (aka PCI segments, in ACPI-speak).
1444 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1445 Configuration
1446 nomsi [MSI] If the PCI_MSI kernel config parameter is
1447 enabled, this kernel boot option can be used to
1448 disable the use of MSI interrupts system-wide.
1449 nosort [X86-32] Don't sort PCI devices according to
1450 order given by the PCI BIOS. This sorting is
1451 done to get a device order compatible with
1452 older kernels.
1453 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1454 routing table. These calls are known to be buggy
1455 on several machines and they hang the machine
1456 when used, but on other computers it's the only
1457 way to get the interrupt routing table. Try
1458 this option if the kernel is unable to allocate
1459 IRQs or discover secondary PCI buses on your
1460 motherboard.
1461 rom [X86-32] Assign address space to expansion ROMs.
1462 Use with caution as certain devices share
1463 address decoders between ROMs and other
1464 resources.
1465 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1466 assigned automatically to PCI devices. You can
1467 make the kernel exclude IRQs of your ISA cards
1468 this way.
1469 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1470 of the PIRQ table (normally generated
1471 by the BIOS) if it is outside the
1472 F0000h-100000h range.
1473 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1474 useful if the kernel is unable to find your
1475 secondary buses and you want to tell it
1476 explicitly which ones they are.
1477 assign-busses [X86-32] Always assign all PCI bus
1478 numbers ourselves, overriding
1479 whatever the firmware may have done.
1480 usepirqmask [X86-32] Honor the possible IRQ mask stored
1481 in the BIOS $PIR table. This is needed on
1482 some systems with broken BIOSes, notably
1483 some HP Pavilion N5400 and Omnibook XE3
1484 notebooks. This will have no effect if ACPI
1485 IRQ routing is enabled.
1486 noacpi [X86-32] Do not use ACPI for IRQ routing
1487 or for PCI scanning.
1488 use_crs [X86-32] Use _CRS for PCI resource
1489 allocation.
1490 routeirq Do IRQ routing for all PCI devices.
1491 This is normally done in pci_enable_device(),
1492 so this option is a temporary workaround
1493 for broken drivers that don't call it.
1494 firmware [ARM] Do not re-enumerate the bus but instead
1495 just use the configuration from the
1496 bootloader. This is currently used on
1497 IXP2000 systems where the bus has to be
1498 configured a certain way for adjunct CPUs.
1499 noearly [X86] Don't do any early type 1 scanning.
1500 This might help on some broken boards which
1501 machine check when some devices' config space
1502 is read. But various workarounds are disabled
1503 and some IOMMU drivers will not work.
1504 bfsort Sort PCI devices into breadth-first order.
1505 This sorting is done to get a device
1506 order compatible with older (<= 2.4) kernels.
1507 nobfsort Don't sort PCI devices into breadth-first order.
1508 cbiosize=nn[KMG] The fixed amount of bus space which is
1509 reserved for the CardBus bridge's IO window.
1510 The default value is 256 bytes.
1511 cbmemsize=nn[KMG] The fixed amount of bus space which is
1512 reserved for the CardBus bridge's memory
1513 window. The default value is 64 megabytes.
1515 pcmv= [HW,PCMCIA] BadgePAD 4
1517 pd. [PARIDE]
1518 See Documentation/paride.txt.
1520 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1521 boot time.
1522 Format: { 0 | 1 }
1523 See arch/parisc/kernel/pdc_chassis.c
1525 pf. [PARIDE]
1526 See Documentation/paride.txt.
1528 pg. [PARIDE]
1529 See Documentation/paride.txt.
1531 pirq= [SMP,APIC] Manual mp-table setup
1532 See Documentation/i386/IO-APIC.txt.
1534 plip= [PPT,NET] Parallel port network link
1535 Format: { parport<nr> | timid | 0 }
1536 See also Documentation/parport.txt.
1538 pnpacpi= [ACPI]
1539 { off }
1541 pnpbios= [ISAPNP]
1542 { on | off | curr | res | no-curr | no-res }
1544 pnp_reserve_irq=
1545 [ISAPNP] Exclude IRQs for the autoconfiguration
1547 pnp_reserve_dma=
1548 [ISAPNP] Exclude DMAs for the autoconfiguration
1550 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1551 Ranges are in pairs (I/O port base and size).
1553 pnp_reserve_mem=
1554 [ISAPNP] Exclude memory regions for the
1555 autoconfiguration.
1556 Ranges are in pairs (memory base and size).
1558 print-fatal-signals=
1559 [KNL] debug: print fatal signals
1560 print-fatal-signals=1: print segfault info to
1561 the kernel console.
1562 default: off.
1564 printk.time= Show timing data prefixed to each printk message line
1565 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1567 profile= [KNL] Enable kernel profiling via /proc/profile
1568 Format: [schedule,]<number>
1569 Param: "schedule" - profile schedule points.
1570 Param: <number> - step/bucket size as a power of 2 for
1571 statistical time based profiling.
1572 Param: "sleep" - profile D-state sleeping (millisecs).
1573 Requires CONFIG_SCHEDSTATS
1574 Param: "kvm" - profile VM exits.
1576 processor.max_cstate= [HW,ACPI]
1577 Limit processor to maximum C-state
1578 max_cstate=9 overrides any DMI blacklist limit.
1580 processor.nocst [HW,ACPI]
1581 Ignore the _CST method to determine C-states,
1582 instead using the legacy FADT method
1584 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1585 before loading.
1586 See Documentation/ramdisk.txt.
1588 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1589 probe for; one of (bare|imps|exps|lifebook|any).
1590 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1591 per second.
1592 psmouse.resetafter= [HW,MOUSE]
1593 Try to reset the device after so many bad packets
1594 (0 = never).
1595 psmouse.resolution=
1596 [HW,MOUSE] Set desired mouse resolution, in dpi.
1597 psmouse.smartscroll=
1598 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1599 0 = disabled, 1 = enabled (default).
1601 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1602 Format:
1603 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1605 pt. [PARIDE]
1606 See Documentation/paride.txt.
1608 pty.legacy_count=
1609 [KNL] Number of legacy pty's. Overwrites compiled-in
1610 default number.
1612 quiet [KNL] Disable most log messages
1614 r128= [HW,DRM]
1616 raid= [HW,RAID]
1617 See Documentation/md.txt.
1619 ramdisk_blocksize= [RAM]
1620 See Documentation/ramdisk.txt.
1622 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1623 See Documentation/ramdisk.txt.
1625 rcupdate.blimit= [KNL,BOOT]
1626 Set maximum number of finished RCU callbacks to process
1627 in one batch.
1629 rcupdate.qhimark= [KNL,BOOT]
1630 Set threshold of queued
1631 RCU callbacks over which batch limiting is disabled.
1633 rcupdate.qlowmark= [KNL,BOOT]
1634 Set threshold of queued RCU callbacks below which
1635 batch limiting is re-enabled.
1637 rdinit= [KNL]
1638 Format: <full_path>
1639 Run specified binary instead of /init from the ramdisk,
1640 used for early userspace startup. See initrd.
1642 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1643 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1644 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1646 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1648 reservetop= [X86-32]
1649 Format: nn[KMG]
1650 Reserves a hole at the top of the kernel virtual
1651 address space.
1653 reset_devices [KNL] Force drivers to reset the underlying device
1654 during initialization.
1656 resume= [SWSUSP]
1657 Specify the partition device for software suspend
1659 resume_offset= [SWSUSP]
1660 Specify the offset from the beginning of the partition
1661 given by "resume=" at which the swap header is located,
1662 in <PAGE_SIZE> units (needed only for swap files).
1663 See Documentation/power/swsusp-and-swap-files.txt
1665 retain_initrd [RAM] Keep initrd memory after extraction
1667 rhash_entries= [KNL,NET]
1668 Set number of hash buckets for route cache
1670 riscom8= [HW,SERIAL]
1671 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1673 ro [KNL] Mount root device read-only on boot
1675 root= [KNL] Root filesystem
1677 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1678 mount the root filesystem
1680 rootflags= [KNL] Set root filesystem mount option string
1682 rootfstype= [KNL] Set root filesystem type
1684 rootwait [KNL] Wait (indefinitely) for root device to show up.
1685 Useful for devices that are detected asynchronously
1686 (e.g. USB and MMC devices).
1688 root_plug.vendor_id=
1689 [ROOTPLUG] Override the default vendor ID
1691 root_plug.product_id=
1692 [ROOTPLUG] Override the default product ID
1694 root_plug.debug=
1695 [ROOTPLUG] Enable debugging output
1697 rw [KNL] Mount root device read-write on boot
1699 S [KNL] Run init in single mode
1701 sa1100ir [NET]
1702 See drivers/net/irda/sa1100_ir.c.
1704 sbni= [NET] Granch SBNI12 leased line adapter
1706 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1707 Format: <io>[,<timeout>[,<isapnp>]]
1709 scsi_debug_*= [SCSI]
1710 See drivers/scsi/scsi_debug.c.
1712 scsi_default_dev_flags=
1713 [SCSI] SCSI default device flags
1714 Format: <integer>
1716 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1717 Format: <vendor>:<model>:<flags>
1718 (flags are integer value)
1720 scsi_logging_level= [SCSI] a bit mask of logging levels
1721 See drivers/scsi/scsi_logging.h for bits. Also
1722 settable via sysctl at dev.scsi.logging_level
1723 (/proc/sys/dev/scsi/logging_level).
1724 There is also a nice 'scsi_logging_level' script in the
1725 S390-tools package, available for download at
1726 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1728 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1729 discovered. async scans them in kernel threads,
1730 allowing boot to proceed. none ignores them, expecting
1731 user space to do the scan.
1733 selinux [SELINUX] Disable or enable SELinux at boot time.
1734 Format: { "0" | "1" }
1735 See security/selinux/Kconfig help text.
1736 0 -- disable.
1737 1 -- enable.
1738 Default value is set via kernel config option.
1739 If enabled at boot time, /selinux/disable can be used
1740 later to disable prior to initial policy load.
1742 selinux_compat_net =
1743 [SELINUX] Set initial selinux_compat_net flag value.
1744 Format: { "0" | "1" }
1745 0 -- use new secmark-based packet controls
1746 1 -- use legacy packet controls
1747 Default value is 0 (preferred).
1748 Value can be changed at runtime via
1749 /selinux/compat_net.
1751 serialnumber [BUGS=X86-32]
1753 shapers= [NET]
1754 Maximal number of shapers.
1756 sim710= [SCSI,HW]
1757 See header of drivers/scsi/sim710.c.
1759 simeth= [IA-64]
1760 simscsi=
1762 slram= [HW,MTD]
1764 slub_debug[=options[,slabs]] [MM, SLUB]
1765 Enabling slub_debug allows one to determine the
1766 culprit if slab objects become corrupted. Enabling
1767 slub_debug can create guard zones around objects and
1768 may poison objects when not in use. Also tracks the
1769 last alloc / free. For more information see
1770 Documentation/vm/slub.txt.
1772 slub_max_order= [MM, SLUB]
1773 Determines the maximum allowed order for slabs.
1774 A high setting may cause OOMs due to memory
1775 fragmentation. For more information see
1776 Documentation/vm/slub.txt.
1778 slub_min_objects= [MM, SLUB]
1779 The minimum number of objects per slab. SLUB will
1780 increase the slab order up to slub_max_order to
1781 generate a sufficiently large slab able to contain
1782 the number of objects indicated. The higher the number
1783 of objects the smaller the overhead of tracking slabs
1784 and the less frequently locks need to be acquired.
1785 For more information see Documentation/vm/slub.txt.
1787 slub_min_order= [MM, SLUB]
1788 Determines the mininum page order for slabs. Must be
1789 lower than slub_max_order.
1790 For more information see Documentation/vm/slub.txt.
1792 slub_nomerge [MM, SLUB]
1793 Disable merging of slabs with similar size. May be
1794 necessary if there is some reason to distinguish
1795 allocs to different slabs. Debug options disable
1796 merging on their own.
1797 For more information see Documentation/vm/slub.txt.
1799 smart2= [HW]
1800 Format: <io1>[,<io2>[,...,<io8>]]
1802 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1803 attempt to substitute SMP alternatives once at boot.
1805 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1806 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1807 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1808 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1809 smsc-ircc2.ircc_irq= [HW] IRQ line
1810 smsc-ircc2.ircc_dma= [HW] DMA channel
1811 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1812 0: Toshiba Satellite 1800 (GP data pin select)
1813 1: Fast pin select (default)
1814 2: ATC IRMode
1816 snd-ad1816a= [HW,ALSA]
1818 snd-ad1848= [HW,ALSA]
1820 snd-ali5451= [HW,ALSA]
1822 snd-als100= [HW,ALSA]
1824 snd-als4000= [HW,ALSA]
1826 snd-azt2320= [HW,ALSA]
1828 snd-cmi8330= [HW,ALSA]
1830 snd-cmipci= [HW,ALSA]
1832 snd-cs4231= [HW,ALSA]
1834 snd-cs4232= [HW,ALSA]
1836 snd-cs4236= [HW,ALSA]
1838 snd-cs4281= [HW,ALSA]
1840 snd-cs46xx= [HW,ALSA]
1842 snd-dt019x= [HW,ALSA]
1844 snd-dummy= [HW,ALSA]
1846 snd-emu10k1= [HW,ALSA]
1848 snd-ens1370= [HW,ALSA]
1850 snd-ens1371= [HW,ALSA]
1852 snd-es968= [HW,ALSA]
1854 snd-es1688= [HW,ALSA]
1856 snd-es18xx= [HW,ALSA]
1858 snd-es1938= [HW,ALSA]
1860 snd-es1968= [HW,ALSA]
1862 snd-fm801= [HW,ALSA]
1864 snd-gusclassic= [HW,ALSA]
1866 snd-gusextreme= [HW,ALSA]
1868 snd-gusmax= [HW,ALSA]
1870 snd-hdsp= [HW,ALSA]
1872 snd-ice1712= [HW,ALSA]
1874 snd-intel8x0= [HW,ALSA]
1876 snd-interwave= [HW,ALSA]
1878 snd-interwave-stb=
1879 [HW,ALSA]
1881 snd-korg1212= [HW,ALSA]
1883 snd-maestro3= [HW,ALSA]
1885 snd-mpu401= [HW,ALSA]
1887 snd-mtpav= [HW,ALSA]
1889 snd-nm256= [HW,ALSA]
1891 snd-opl3sa2= [HW,ALSA]
1893 snd-opti92x-ad1848=
1894 [HW,ALSA]
1896 snd-opti92x-cs4231=
1897 [HW,ALSA]
1899 snd-opti93x= [HW,ALSA]
1901 snd-pmac= [HW,ALSA]
1903 snd-rme32= [HW,ALSA]
1905 snd-rme96= [HW,ALSA]
1907 snd-rme9652= [HW,ALSA]
1909 snd-sb8= [HW,ALSA]
1911 snd-sb16= [HW,ALSA]
1913 snd-sbawe= [HW,ALSA]
1915 snd-serial= [HW,ALSA]
1917 snd-sgalaxy= [HW,ALSA]
1919 snd-sonicvibes= [HW,ALSA]
1921 snd-sun-amd7930=
1922 [HW,ALSA]
1924 snd-sun-cs4231= [HW,ALSA]
1926 snd-trident= [HW,ALSA]
1928 snd-usb-audio= [HW,ALSA,USB]
1930 snd-via82xx= [HW,ALSA]
1932 snd-virmidi= [HW,ALSA]
1934 snd-wavefront= [HW,ALSA]
1936 snd-ymfpci= [HW,ALSA]
1938 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1939 See Documentation/sonypi.txt
1941 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1942 See Documentation/specialix.txt.
1944 spia_io_base= [HW,MTD]
1945 spia_fio_base=
1946 spia_pedr=
1947 spia_peddr=
1949 sscape= [HW,OSS]
1950 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1952 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1953 See Documentation/scsi/st.txt.
1955 sti= [PARISC,HW]
1956 Format: <num>
1957 Set the STI (builtin display/keyboard on the HP-PARISC
1958 machines) console (graphic card) which should be used
1959 as the initial boot-console.
1960 See also comment in drivers/video/console/sticore.c.
1962 sti_font= [HW]
1963 See comment in drivers/video/console/sticore.c.
1965 stifb= [HW]
1966 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1968 sunrpc.pool_mode=
1969 [NFS]
1970 Control how the NFS server code allocates CPUs to
1971 service thread pools. Depending on how many NICs
1972 you have and where their interrupts are bound, this
1973 option will affect which CPUs will do NFS serving.
1974 Note: this parameter cannot be changed while the
1975 NFS server is running.
1977 auto the server chooses an appropriate mode
1978 automatically using heuristics
1979 global a single global pool contains all CPUs
1980 percpu one pool for each CPU
1981 pernode one pool for each NUMA node (equivalent
1982 to global on non-NUMA machines)
1984 swiotlb= [IA-64] Number of I/O TLB slabs
1986 switches= [HW,M68k]
1988 sym53c416= [HW,SCSI]
1989 See header of drivers/scsi/sym53c416.c.
1991 sysrq_always_enabled
1992 [KNL]
1993 Ignore sysrq setting - this boot parameter will
1994 neutralize any effect of /proc/sys/kernel/sysrq.
1995 Useful for debugging.
1997 t128= [HW,SCSI]
1998 See header of drivers/scsi/t128.c.
2000 tdfx= [HW,DRM]
2002 thash_entries= [KNL,NET]
2003 Set number of hash buckets for TCP connection
2005 thermal.act= [HW,ACPI]
2006 -1: disable all active trip points in all thermal zones
2007 <degrees C>: override all lowest active trip points
2009 thermal.crt= [HW,ACPI]
2010 -1: disable all critical trip points in all thermal zones
2011 <degrees C>: lower all critical trip points
2013 thermal.nocrt= [HW,ACPI]
2014 Set to disable actions on ACPI thermal zone
2015 critical and hot trip points.
2017 thermal.off= [HW,ACPI]
2018 1: disable ACPI thermal control
2020 thermal.psv= [HW,ACPI]
2021 -1: disable all passive trip points
2022 <degrees C>: override all passive trip points to this value
2024 thermal.tzp= [HW,ACPI]
2025 Specify global default ACPI thermal zone polling rate
2026 <deci-seconds>: poll all this frequency
2027 0: no polling (default)
2029 tipar.timeout= [HW,PPT]
2030 Set communications timeout in tenths of a second
2031 (default 15).
2033 tipar.delay= [HW,PPT]
2034 Set inter-bit delay in microseconds (default 10).
2036 tmscsim= [HW,SCSI]
2037 See comment before function dc390_setup() in
2038 drivers/scsi/tmscsim.c.
2040 tp720= [HW,PS2]
2042 trix= [HW,OSS] MediaTrix AudioTrix Pro
2043 Format:
2044 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2046 turbografx.map[2|3]= [HW,JOY]
2047 TurboGraFX parallel port interface
2048 Format:
2049 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2050 See also Documentation/input/joystick-parport.txt
2052 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2053 See header of drivers/scsi/u14-34f.c.
2055 uart401= [HW,OSS]
2056 Format: <io>,<irq>
2058 uart6850= [HW,OSS]
2059 Format: <io>,<irq>
2061 uhci-hcd.ignore_oc=
2062 [USB] Ignore overcurrent events (default N).
2063 Some badly-designed motherboards generate lots of
2064 bogus events, for ports that aren't wired to
2065 anything. Set this parameter to avoid log spamming.
2066 Note that genuine overcurrent events won't be
2067 reported either.
2069 usbcore.autosuspend=
2070 [USB] The autosuspend time delay (in seconds) used
2071 for newly-detected USB devices (default 2). This
2072 is the time required before an idle device will be
2073 autosuspended. Devices for which the delay is set
2074 to a negative value won't be autosuspended at all.
2076 usbhid.mousepoll=
2077 [USBHID] The interval which mice are to be polled at.
2079 vdso= [X86-32,SH,x86-64]
2080 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2081 vdso=1: enable VDSO (default)
2082 vdso=0: disable VDSO mapping
2084 vdso32= [X86-32,X86-64]
2085 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2086 vdso32=1: enable 32-bit VDSO (default)
2087 vdso32=0: disable 32-bit VDSO mapping
2089 vector= [IA-64,SMP]
2090 vector=percpu: enable percpu vector domain
2092 video= [FB] Frame buffer configuration
2093 See Documentation/fb/modedb.txt.
2095 vga= [BOOT,X86-32] Select a particular video mode
2096 See Documentation/i386/boot.txt and
2097 Documentation/svga.txt.
2098 Use vga=ask for menu.
2099 This is actually a boot loader parameter; the value is
2100 passed to the kernel using a special protocol.
2102 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2103 size of <nn>. This can be used to increase the
2104 minimum size (128MB on x86). It can also be used to
2105 decrease the size and leave more room for directly
2106 mapped kernel RAM.
2108 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2109 Format: <command>
2111 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2112 Format: <command>
2114 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2115 Format: <command>
2117 waveartist= [HW,OSS]
2118 Format: <io>,<irq>,<dma>,<dma2>
2120 wd33c93= [HW,SCSI]
2121 See header of drivers/scsi/wd33c93.c.
2123 wd7000= [HW,SCSI]
2124 See header of drivers/scsi/wd7000.c.
2126 wdt= [WDT] Watchdog
2127 See Documentation/watchdog/wdt.txt.
2129 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2130 xd_geo= See header of drivers/block/xd.c.
2132 xirc2ps_cs= [NET,PCMCIA]
2133 Format:
2134 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2136 norandmaps Don't use address space randomization
2137 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2139 ______________________________________________________________________
2141 TODO:
2143 Add documentation for ALSA options.
2144 Add more DRM drivers.