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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 security= [SECURITY] Choose a security module to enable at boot.
370 If this boot parameter is not specified, only the first
371 security module asking for security registration will be
372 loaded. An invalid security module name will be treated
373 as if no module has been chosen.
375 capability.disable=
376 [SECURITY] Disable capabilities. This would normally
377 be used only if an alternative security model is to be
378 configured. Potentially dangerous and should only be
379 used if you are entirely sure of the consequences.
381 ccw_timeout_log [S390]
382 See Documentation/s390/CommonIO for details.
384 cgroup_disable= [KNL] Disable a particular controller
385 Format: {name of the controller(s) to disable}
386 {Currently supported controllers - "memory"}
388 checkreqprot [SELINUX] Set initial checkreqprot flag value.
389 Format: { "0" | "1" }
390 See security/selinux/Kconfig help text.
391 0 -- check protection applied by kernel (includes
392 any implied execute protection).
393 1 -- check protection requested by application.
394 Default value is set via a kernel config option.
395 Value can be changed at runtime via
396 /selinux/checkreqprot.
398 cio_ignore= [S390]
399 See Documentation/s390/CommonIO for details.
401 cio_msg= [S390]
402 See Documentation/s390/CommonIO for details.
404 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
405 [Deprecated]
406 Forces specified clocksource (if available) to be used
407 when calculating gettimeofday(). If specified
408 clocksource is not available, it defaults to PIT.
409 Format: { pit | tsc | cyclone | pmtmr }
411 clocksource= [GENERIC_TIME] Override the default clocksource
412 Format: <string>
413 Override the default clocksource and use the clocksource
414 with the name specified.
415 Some clocksource names to choose from, depending on
416 the platform:
417 [all] jiffies (this is the base, fallback clocksource)
418 [ACPI] acpi_pm
419 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
420 pxa_timer,timer3,32k_counter,timer0_1
421 [AVR32] avr32
422 [X86-32] pit,hpet,tsc,vmi-timer;
423 scx200_hrt on Geode; cyclone on IBM x440
424 [MIPS] MIPS
425 [PARISC] cr16
426 [S390] tod
427 [SH] SuperH
428 [SPARC64] tick
429 [X86-64] hpet,tsc
431 clearcpuid=BITNUM [X86]
432 Disable CPUID feature X for the kernel. See
433 include/asm-x86/cpufeature.h for the valid bit numbers.
434 Note the Linux specific bits are not necessarily
435 stable over kernel options, but the vendor specific
436 ones should be.
437 Also note that user programs calling CPUID directly
438 or using the feature without checking anything
439 will still see it. This just prevents it from
440 being used by the kernel or shown in /proc/cpuinfo.
441 Also note the kernel might malfunction if you disable
442 some critical bits.
444 code_bytes [IA32/X86_64] How many bytes of object code to print
445 in an oops report.
446 Range: 0 - 8192
447 Default: 64
449 disable_8254_timer
450 enable_8254_timer
451 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
452 over the 8254 in addition to over the IO-APIC. The
453 kernel tries to set a sensible default.
455 hpet= [X86-32,HPET] option to control HPET usage
456 Format: { enable (default) | disable | force }
457 disable: disable HPET and use PIT instead
458 force: allow force enabled of undocumented chips (ICH4,
459 VIA, nVidia)
461 com20020= [HW,NET] ARCnet - COM20020 chipset
462 Format:
463 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
465 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
466 Format: <io>[,<irq>]
468 com90xx= [HW,NET]
469 ARCnet - COM90xx chipset (memory-mapped buffers)
470 Format: <io>[,<irq>[,<memstart>]]
472 condev= [HW,S390] console device
473 conmode=
475 console= [KNL] Output console device and options.
477 tty<n> Use the virtual console device <n>.
479 ttyS<n>[,options]
480 ttyUSB0[,options]
481 Use the specified serial port. The options are of
482 the form "bbbbpnf", where "bbbb" is the baud rate,
483 "p" is parity ("n", "o", or "e"), "n" is number of
484 bits, and "f" is flow control ("r" for RTS or
485 omit it). Default is "9600n8".
487 See Documentation/serial-console.txt for more
488 information. See
489 Documentation/networking/netconsole.txt for an
490 alternative.
492 uart[8250],io,<addr>[,options]
493 uart[8250],mmio,<addr>[,options]
494 Start an early, polled-mode console on the 8250/16550
495 UART at the specified I/O port or MMIO address,
496 switching to the matching ttyS device later. The
497 options are the same as for ttyS, above.
499 earlycon= [KNL] Output early console device and options.
500 uart[8250],io,<addr>[,options]
501 uart[8250],mmio,<addr>[,options]
502 Start an early, polled-mode console on the 8250/16550
503 UART at the specified I/O port or MMIO address.
504 The options are the same as for ttyS, above.
506 no_console_suspend
507 [HW] Never suspend the console
508 Disable suspending of consoles during suspend and
509 hibernate operations. Once disabled, debugging
510 messages can reach various consoles while the rest
511 of the system is being put to sleep (ie, while
512 debugging driver suspend/resume hooks). This may
513 not work reliably with all consoles, but is known
514 to work with serial and VGA consoles.
516 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
517 Format:
518 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
520 crashkernel=nn[KMG]@ss[KMG]
521 [KNL] Reserve a chunk of physical memory to
522 hold a kernel to switch to with kexec on panic.
524 crashkernel=range1:size1[,range2:size2,...][@offset]
525 [KNL] Same as above, but depends on the memory
526 in the running system. The syntax of range is
527 start-[end] where start and end are both
528 a memory unit (amount[KMG]). See also
529 Documentation/kdump/kdump.txt for a example.
531 cs4232= [HW,OSS]
532 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
534 cs89x0_dma= [HW,NET]
535 Format: <dma>
537 cs89x0_media= [HW,NET]
538 Format: { rj45 | aui | bnc }
540 dasd= [HW,NET]
541 See header of drivers/s390/block/dasd_devmap.c.
543 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
544 (one device per port)
545 Format: <port#>,<type>
546 See also Documentation/input/joystick-parport.txt
548 debug [KNL] Enable kernel debugging (events log level).
550 debug_locks_verbose=
551 [KNL] verbose self-tests
552 Format=<0|1>
553 Print debugging info while doing the locking API
554 self-tests.
555 We default to 0 (no extra messages), setting it to
556 1 will print _a lot_ more information - normally
557 only useful to kernel developers.
559 decnet.addr= [HW,NET]
560 Format: <area>[,<node>]
561 See also Documentation/networking/decnet.txt.
563 vt.default_blu= [VT]
564 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
565 Change the default blue palette of the console.
566 This is a 16-member array composed of values
567 ranging from 0-255.
569 vt.default_grn= [VT]
570 Format: <green0>,<green1>,<green2>,...,<green15>
571 Change the default green palette of the console.
572 This is a 16-member array composed of values
573 ranging from 0-255.
575 vt.default_red= [VT]
576 Format: <red0>,<red1>,<red2>,...,<red15>
577 Change the default red palette of the console.
578 This is a 16-member array composed of values
579 ranging from 0-255.
581 vt.default_utf8=
582 [VT]
583 Format=<0|1>
584 Set system-wide default UTF-8 mode for all tty's.
585 Default is 1, i.e. UTF-8 mode is enabled for all
586 newly opened terminals.
588 dhash_entries= [KNL]
589 Set number of hash buckets for dentry cache.
591 digi= [HW,SERIAL]
592 IO parameters + enable/disable command.
594 digiepca= [HW,SERIAL]
595 See drivers/char/README.epca and
596 Documentation/digiepca.txt.
598 disable_mtrr_trim [X86, Intel and AMD only]
599 By default the kernel will trim any uncacheable
600 memory out of your available memory pool based on
601 MTRR settings. This parameter disables that behavior,
602 possibly causing your machine to run very slowly.
604 dmasound= [HW,OSS] Sound subsystem buffers
606 dscc4.setup= [NET]
608 dtc3181e= [HW,SCSI]
610 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
611 earlyprintk=vga
612 earlyprintk=serial[,ttySn[,baudrate]]
614 Append ",keep" to not disable it when the real console
615 takes over.
617 Only vga or serial at a time, not both.
619 Currently only ttyS0 and ttyS1 are supported.
621 Interaction with the standard serial driver is not
622 very good.
624 The VGA output is eventually overwritten by the real
625 console.
627 eata= [HW,SCSI]
629 edd= [EDD]
630 Format: {"of[f]" | "sk[ipmbr]"}
631 See comment in arch/i386/boot/edd.S
633 eisa_irq_edge= [PARISC,HW]
634 See header of drivers/parisc/eisa.c.
636 elanfreq= [X86-32]
637 See comment before function elanfreq_setup() in
638 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
640 elevator= [IOSCHED]
641 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
642 See Documentation/block/as-iosched.txt and
643 Documentation/block/deadline-iosched.txt for details.
645 elfcorehdr= [X86-32, X86_64]
646 Specifies physical address of start of kernel core
647 image elf header. Generally kexec loader will
648 pass this option to capture kernel.
649 See Documentation/kdump/kdump.txt for details.
651 enforcing [SELINUX] Set initial enforcing status.
652 Format: {"0" | "1"}
653 See security/selinux/Kconfig help text.
654 0 -- permissive (log only, no denials).
655 1 -- enforcing (deny and log).
656 Default value is 0.
657 Value can be changed at runtime via /selinux/enforce.
659 es1371= [HW,OSS]
660 Format: <spdif>,[<nomix>,[<amplifier>]]
661 See also header of sound/oss/es1371.c.
663 ether= [HW,NET] Ethernet cards parameters
664 This option is obsoleted by the "netdev=" option, which
665 has equivalent usage. See its documentation for details.
667 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
668 Format: <io>[,<irq>]
670 failslab=
671 fail_page_alloc=
672 fail_make_request=[KNL]
673 General fault injection mechanism.
674 Format: <interval>,<probability>,<space>,<times>
675 See also /Documentation/fault-injection/.
677 fd_mcs= [HW,SCSI]
678 See header of drivers/scsi/fd_mcs.c.
680 fdomain= [HW,SCSI]
681 See header of drivers/scsi/fdomain.c.
683 floppy= [HW]
684 See Documentation/floppy.txt.
686 gamecon.map[2|3]=
687 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
688 support via parallel port (up to 5 devices per port)
689 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
690 See also Documentation/input/joystick-parport.txt
692 gamma= [HW,DRM]
694 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
695 Format: off | on
696 default: on
698 gdth= [HW,SCSI]
699 See header of drivers/scsi/gdth.c.
701 gpt [EFI] Forces disk with valid GPT signature but
702 invalid Protective MBR to be treated as GPT.
704 gvp11= [HW,SCSI]
706 hashdist= [KNL,NUMA] Large hashes allocated during boot
707 are distributed across NUMA nodes. Defaults on
708 for IA-64, off otherwise.
709 Format: 0 | 1 (for off | on)
711 hcl= [IA-64] SGI's Hardware Graph compatibility layer
713 hd= [EIDE] (E)IDE hard drive subsystem geometry
714 Format: <cyl>,<head>,<sect>
716 hd?= [HW] (E)IDE subsystem
717 hd?lun= See Documentation/ide/ide.txt.
719 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
720 size of <nn>. This works even on boxes that have no
721 highmem otherwise. This also works to reduce highmem
722 size on bigger boxes.
724 highres= [KNL] Enable/disable high resolution timer mode.
725 Valid parameters: "on", "off"
726 Default: "on"
728 hisax= [HW,ISDN]
729 See Documentation/isdn/README.HiSax.
731 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
732 hugepagesz= [HW,IA-64,PPC] The size of the HugeTLB pages.
734 i8042.direct [HW] Put keyboard port into non-translated mode
735 i8042.dumbkbd [HW] Pretend that controller can only read data from
736 keyboard and cannot control its state
737 (Don't attempt to blink the leds)
738 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
739 i8042.nokbd [HW] Don't check/create keyboard port
740 i8042.noloop [HW] Disable the AUX Loopback command while probing
741 for the AUX port
742 i8042.nomux [HW] Don't check presence of an active multiplexing
743 controller
744 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
745 controllers
746 i8042.panicblink=
747 [HW] Frequency with which keyboard LEDs should blink
748 when kernel panics (default is 0.5 sec)
749 i8042.reset [HW] Reset the controller during init and cleanup
750 i8042.unlock [HW] Unlock (ignore) the keylock
752 i810= [HW,DRM]
754 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
755 indicates that the driver is running on unsupported
756 hardware.
757 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
758 does not match list of supported models.
759 i8k.power_status
760 [HW] Report power status in /proc/i8k
761 (disabled by default)
762 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
763 capability is set.
765 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
766 See Documentation/mca.txt.
768 icn= [HW,ISDN]
769 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
771 ide= [HW] (E)IDE subsystem
772 Format: ide=nodma or ide=doubler
773 See Documentation/ide/ide.txt.
775 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
776 See Documentation/ide/ide.txt.
778 idle= [X86]
779 Format: idle=poll or idle=mwait
780 Poll forces a polling idle loop that can slightly improves the performance
781 of waking up a idle CPU, but will use a lot of power and make the system
782 run hot. Not recommended.
783 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
784 to not use it because it doesn't save as much power as a normal idle
785 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
786 as idle=poll.
788 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
789 Claim all unknown PCI IDE storage controllers.
791 ignore_loglevel [KNL]
792 Ignore loglevel setting - this will print /all/
793 kernel messages to the console. Useful for debugging.
795 ihash_entries= [KNL]
796 Set number of hash buckets for inode cache.
798 in2000= [HW,SCSI]
799 See header of drivers/scsi/in2000.c.
801 init= [KNL]
802 Format: <full_path>
803 Run specified binary instead of /sbin/init as init
804 process.
806 initcall_debug [KNL] Trace initcalls as they are executed. Useful
807 for working out where the kernel is dying during
808 startup.
810 initrd= [BOOT] Specify the location of the initial ramdisk
812 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
813 Format: <irq>
815 inttest= [IA64]
817 iommu= [x86]
818 off
819 force
820 noforce
821 biomerge
822 panic
823 nopanic
824 merge
825 nomerge
826 forcesac
827 soft
830 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
831 off
832 Disable intel iommu driver.
833 igfx_off [Default Off]
834 By default, gfx is mapped as normal device. If a gfx
835 device has a dedicated DMAR unit, the DMAR unit is
836 bypassed by not enabling DMAR with this option. In
837 this case, gfx device will use physical address for
838 DMA.
839 forcedac [x86_64]
840 With this option iommu will not optimize to look
841 for io virtual address below 32 bit forcing dual
842 address cycle on pci bus for cards supporting greater
843 than 32 bit addressing. The default is to look
844 for translation below 32 bit and if not available
845 then look in the higher range.
846 strict [Default Off]
847 With this option on every unmap_single operation will
848 result in a hardware IOTLB flush operation as opposed
849 to batching them for performance.
851 io_delay= [X86-32,X86-64] I/O delay method
852 0x80
853 Standard port 0x80 based delay
854 0xed
855 Alternate port 0xed based delay (needed on some systems)
856 udelay
857 Simple two microseconds delay
858 none
859 No delay
861 io7= [HW] IO7 for Marvel based alpha systems
862 See comment before marvel_specify_io7 in
863 arch/alpha/kernel/core_marvel.c.
865 ip= [IP_PNP]
866 See Documentation/filesystems/nfsroot.txt.
868 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
869 See comment before ip2_setup() in
870 drivers/char/ip2/ip2base.c.
872 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
873 See header of drivers/scsi/ips.c.
875 ports= [IP_VS_FTP] IPVS ftp helper module
876 Default is 21.
877 Up to 8 (IP_VS_APP_MAX_PORTS) ports
878 may be specified.
879 Format: <port>,<port>....
881 irqfixup [HW]
882 When an interrupt is not handled search all handlers
883 for it. Intended to get systems with badly broken
884 firmware running.
886 irqpoll [HW]
887 When an interrupt is not handled search all handlers
888 for it. Also check all handlers each timer
889 interrupt. Intended to get systems with badly broken
890 firmware running.
892 isapnp= [ISAPNP]
893 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
895 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
896 Format:
897 <cpu number>,...,<cpu number>
898 or
899 <cpu number>-<cpu number> (must be a positive range in ascending order)
900 or a mixture
901 <cpu number>,...,<cpu number>-<cpu number>
902 This option can be used to specify one or more CPUs
903 to isolate from the general SMP balancing and scheduling
904 algorithms. The only way to move a process onto or off
905 an "isolated" CPU is via the CPU affinity syscalls.
906 <cpu number> begins at 0 and the maximum value is
907 "number of CPUs in system - 1".
909 This option is the preferred way to isolate CPUs. The
910 alternative -- manually setting the CPU mask of all
911 tasks in the system -- can cause problems and
912 suboptimal load balancer performance.
914 iucv= [HW,NET]
916 js= [HW,JOY] Analog joystick
917 See Documentation/input/joystick.txt.
919 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
920 specifies the amount of memory usable by the kernel
921 for non-movable allocations. The requested amount is
922 spread evenly throughout all nodes in the system. The
923 remaining memory in each node is used for Movable
924 pages. In the event, a node is too small to have both
925 kernelcore and Movable pages, kernelcore pages will
926 take priority and other nodes will have a larger number
927 of kernelcore pages. The Movable zone is used for the
928 allocation of pages that may be reclaimed or moved
929 by the page migration subsystem. This means that
930 HugeTLB pages may not be allocated from this zone.
931 Note that allocations like PTEs-from-HighMem still
932 use the HighMem zone if it exists, and the Normal
933 zone if it does not.
935 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
936 is similar to kernelcore except it specifies the
937 amount of memory used for migratable allocations.
938 If both kernelcore and movablecore is specified,
939 then kernelcore will be at *least* the specified
940 value but may be more. If movablecore on its own
941 is specified, the administrator must be careful
942 that the amount of memory usable for all allocations
943 is not too small.
945 keepinitrd [HW,ARM]
947 kstack=N [X86-32,X86-64] Print N words from the kernel stack
948 in oops dumps.
950 kgdboc= [HW] kgdb over consoles.
951 Requires a tty driver that supports console polling.
952 (only serial suported for now)
953 Format: <serial_device>[,baud]
955 l2cr= [PPC]
957 l3cr= [PPC]
959 lapic [X86-32,APIC] Enable the local APIC even if BIOS
960 disabled it.
962 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
963 C2 power state.
965 libata.dma= [LIBATA] DMA control
966 libata.dma=0 Disable all PATA and SATA DMA
967 libata.dma=1 PATA and SATA Disk DMA only
968 libata.dma=2 ATAPI (CDROM) DMA only
969 libata.dma=4 Compact Flash DMA only
970 Combinations also work, so libata.dma=3 enables DMA
971 for disks and CDROMs, but not CFs.
973 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
974 when set.
975 Format: <int>
977 libata.force= [LIBATA] Force configurations. The format is comma
978 separated list of "[ID:]VAL" where ID is
979 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
980 matching port, link or device. Basically, it matches
981 the ATA ID string printed on console by libata. If
982 the whole ID part is omitted, the last PORT and DEVICE
983 values are used. If ID hasn't been specified yet, the
984 configuration applies to all ports, links and devices.
986 If only DEVICE is omitted, the parameter applies to
987 the port and all links and devices behind it. DEVICE
988 number of 0 either selects the first device or the
989 first fan-out link behind PMP device. It does not
990 select the host link. DEVICE number of 15 selects the
991 host link and device attached to it.
993 The VAL specifies the configuration to force. As long
994 as there's no ambiguity shortcut notation is allowed.
995 For example, both 1.5 and 1.5G would work for 1.5Gbps.
996 The following configurations can be forced.
998 * Cable type: 40c, 80c, short40c, unk, ign or sata.
999 Any ID with matching PORT is used.
1001 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1003 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1004 udma[/][16,25,33,44,66,100,133] notation is also
1005 allowed.
1007 * [no]ncq: Turn on or off NCQ.
1009 If there are multiple matching configurations changing
1010 the same attribute, the last one is used.
1012 load_ramdisk= [RAM] List of ramdisks to load from floppy
1013 See Documentation/ramdisk.txt.
1015 lockd.nlm_grace_period=P [NFS] Assign grace period.
1016 Format: <integer>
1018 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1019 Format: <integer>
1021 lockd.nlm_timeout=T [NFS] Assign timeout value.
1022 Format: <integer>
1024 lockd.nlm_udpport=M [NFS] Assign UDP port.
1025 Format: <integer>
1027 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1028 Format: <irq>
1030 loglevel= All Kernel Messages with a loglevel smaller than the
1031 console loglevel will be printed to the console. It can
1032 also be changed with klogd or other programs. The
1033 loglevels are defined as follows:
1035 0 (KERN_EMERG) system is unusable
1036 1 (KERN_ALERT) action must be taken immediately
1037 2 (KERN_CRIT) critical conditions
1038 3 (KERN_ERR) error conditions
1039 4 (KERN_WARNING) warning conditions
1040 5 (KERN_NOTICE) normal but significant condition
1041 6 (KERN_INFO) informational
1042 7 (KERN_DEBUG) debug-level messages
1044 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1045 Format: { n | nk | nM }
1046 n must be a power of two. The default size
1047 is set in the kernel config file.
1049 logo.nologo [FB] Disables display of the built-in Linux logo.
1050 This may be used to provide more screen space for
1051 kernel log messages and is useful when debugging
1052 kernel boot problems.
1054 lp=0 [LP] Specify parallel ports to use, e.g,
1055 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1056 lp=reset first parallel port). 'lp=0' disables the
1057 lp=auto printer driver. 'lp=reset' (which can be
1058 specified in addition to the ports) causes
1059 attached printers to be reset. Using
1060 lp=port1,port2,... specifies the parallel ports
1061 to associate lp devices with, starting with
1062 lp0. A port specification may be 'none' to skip
1063 that lp device, or a parport name such as
1064 'parport0'. Specifying 'lp=auto' instead of a
1065 port specification list means that device IDs
1066 from each port should be examined, to see if
1067 an IEEE 1284-compliant printer is attached; if
1068 so, the driver will manage that printer.
1069 See also header of drivers/char/lp.c.
1071 lpj=n [KNL]
1072 Sets loops_per_jiffy to given constant, thus avoiding
1073 time-consuming boot-time autodetection (up to 250 ms per
1074 CPU). 0 enables autodetection (default). To determine
1075 the correct value for your kernel, boot with normal
1076 autodetection and see what value is printed. Note that
1077 on SMP systems the preset will be applied to all CPUs,
1078 which is likely to cause problems if your CPUs need
1079 significantly divergent settings. An incorrect value
1080 will cause delays in the kernel to be wrong, leading to
1081 unpredictable I/O errors and other breakage. Although
1082 unlikely, in the extreme case this might damage your
1083 hardware.
1085 ltpc= [NET]
1086 Format: <io>,<irq>,<dma>
1088 mac5380= [HW,SCSI] Format:
1089 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1091 mac53c9x= [HW,SCSI] Format:
1092 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1094 machvec= [IA64] Force the use of a particular machine-vector
1095 (machvec) in a generic kernel.
1096 Example: machvec=hpzx1_swiotlb
1098 max_loop= [LOOP] Maximum number of loopback devices that can
1099 be mounted
1100 Format: <1-256>
1102 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1103 should make use of. maxcpus=n : n >= 0 limits the
1104 kernel to using 'n' processors. n=0 is a special case,
1105 it is equivalent to "nosmp", which also disables
1106 the IO APIC.
1108 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
1109 equal to this physical address is ignored.
1111 max_luns= [SCSI] Maximum number of LUNs to probe.
1112 Should be between 1 and 2^32-1.
1114 max_report_luns=
1115 [SCSI] Maximum number of LUNs received.
1116 Should be between 1 and 16384.
1118 mcatest= [IA-64]
1120 mce [X86-32] Machine Check Exception
1122 mce=option [X86-64] See Documentation/x86_64/boot-options.txt
1124 md= [HW] RAID subsystems devices and level
1125 See Documentation/md.txt.
1127 mdacon= [MDA]
1128 Format: <first>,<last>
1129 Specifies range of consoles to be captured by the MDA.
1131 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1132 Amount of memory to be used when the kernel is not able
1133 to see the whole system memory or for test.
1134 [X86-32] Use together with memmap= to avoid physical
1135 address space collisions. Without memmap= PCI devices
1136 could be placed at addresses belonging to unused RAM.
1138 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1139 memory.
1141 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1142 E820 memory map, as specified by the user.
1143 Such memmap=exactmap lines can be constructed based on
1144 BIOS output or other requirements. See the memmap=nn@ss
1145 option description.
1147 memmap=nn[KMG]@ss[KMG]
1148 [KNL] Force usage of a specific region of memory
1149 Region of memory to be used, from ss to ss+nn.
1151 memmap=nn[KMG]#ss[KMG]
1152 [KNL,ACPI] Mark specific memory as ACPI data.
1153 Region of memory to be used, from ss to ss+nn.
1155 memmap=nn[KMG]$ss[KMG]
1156 [KNL,ACPI] Mark specific memory as reserved.
1157 Region of memory to be used, from ss to ss+nn.
1158 Example: Exclude memory from 0x18690000-0x1869ffff
1159 memmap=64K$0x18690000
1160 or
1161 memmap=0x10000$0x18690000
1163 memtest= [KNL,X86_64] Enable memtest
1164 Format: <integer>
1165 range: 0,4 : pattern number
1166 default : 0 <disable>
1168 meye.*= [HW] Set MotionEye Camera parameters
1169 See Documentation/video4linux/meye.txt.
1171 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1172 Multi-Function General Purpose Timers on AMD Geode
1173 platforms.
1175 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1176 the BIOS has incorrectly applied a workaround. TinyBIOS
1177 version 0.98 is known to be affected, 0.99 fixes the
1178 problem by letting the user disable the workaround.
1180 mga= [HW,DRM]
1182 mousedev.tap_time=
1183 [MOUSE] Maximum time between finger touching and
1184 leaving touchpad surface for touch to be considered
1185 a tap and be reported as a left button click (for
1186 touchpads working in absolute mode only).
1187 Format: <msecs>
1188 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1189 reporting absolute coordinates, such as tablets
1190 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1191 reporting absolute coordinates, such as tablets
1193 mpu401= [HW,OSS]
1194 Format: <io>,<irq>
1196 MTD_Partition= [MTD]
1197 Format: <name>,<region-number>,<size>,<offset>
1199 MTD_Region= [MTD] Format:
1200 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1202 mtdparts= [MTD]
1203 See drivers/mtd/cmdlinepart.c.
1205 mtouchusb.raw_coordinates=
1206 [HW] Make the MicroTouch USB driver use raw coordinates
1207 ('y', default) or cooked coordinates ('n')
1209 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1211 NCR_D700= [HW,SCSI]
1212 See header of drivers/scsi/NCR_D700.c.
1214 ncr5380= [HW,SCSI]
1216 ncr53c400= [HW,SCSI]
1218 ncr53c400a= [HW,SCSI]
1220 ncr53c406a= [HW,SCSI]
1222 ncr53c8xx= [HW,SCSI]
1224 netdev= [NET] Network devices parameters
1225 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1226 Note that mem_start is often overloaded to mean
1227 something different and driver-specific.
1228 This usage is only documented in each driver source
1229 file if at all.
1231 nfsaddrs= [NFS]
1232 See Documentation/filesystems/nfsroot.txt.
1234 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1235 See Documentation/filesystems/nfsroot.txt.
1237 nfs.callback_tcpport=
1238 [NFS] set the TCP port on which the NFSv4 callback
1239 channel should listen.
1241 nfs.idmap_cache_timeout=
1242 [NFS] set the maximum lifetime for idmapper cache
1243 entries.
1245 nfs.enable_ino64=
1246 [NFS] enable 64-bit inode numbers.
1247 If zero, the NFS client will fake up a 32-bit inode
1248 number for the readdir() and stat() syscalls instead
1249 of returning the full 64-bit number.
1250 The default is to return 64-bit inode numbers.
1252 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1253 when a NMI is triggered.
1254 Format: [state][,regs][,debounce][,die]
1256 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1258 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1259 emulation library even if a 387 maths coprocessor
1260 is present.
1262 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1263 caches in the slab allocator. Saves per-node memory,
1264 but will impact performance.
1266 noalign [KNL,ARM]
1268 noapic [SMP,APIC] Tells the kernel to not make use of any
1269 IOAPICs that may be present in the system.
1271 nobats [PPC] Do not use BATs for mapping kernel lowmem
1272 on "Classic" PPC cores.
1274 nocache [ARM]
1276 nodelayacct [KNL] Disable per-task delay accounting
1278 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1280 noefi [X86-32,X86-64] Disable EFI runtime services support.
1282 noexec [IA-64]
1284 noexec [X86-32,X86-64]
1285 On X86-32 available only on PAE configured kernels.
1286 noexec=on: enable non-executable mappings (default)
1287 noexec=off: disable non-executable mappings
1289 noexec32 [X86-64]
1290 This affects only 32-bit executables.
1291 noexec32=on: enable non-executable mappings (default)
1292 read doesn't imply executable mappings
1293 noexec32=off: disable non-executable mappings
1294 read implies executable mappings
1296 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1297 register save and restore. The kernel will only save
1298 legacy floating-point registers on task switch.
1300 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1302 nohlt [BUGS=ARM]
1304 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1305 instruction doesn't work correctly and not to
1306 use it.
1308 nohalt [IA-64] Tells the kernel not to use the power saving
1309 function PAL_HALT_LIGHT when idle. This increases
1310 power-consumption. On the positive side, it reduces
1311 interrupt wake-up latency, which may improve performance
1312 in certain environments such as networked servers or
1313 real-time systems.
1315 nohz= [KNL] Boottime enable/disable dynamic ticks
1316 Valid arguments: on, off
1317 Default: on
1319 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1321 noirqdebug [X86-32] Disables the code which attempts to detect and
1322 disable unhandled interrupt sources.
1324 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1325 broken timer IRQ sources.
1327 noisapnp [ISAPNP] Disables ISA PnP code.
1329 noinitrd [RAM] Tells the kernel not to load any configured
1330 initial RAM disk.
1332 nointroute [IA-64]
1334 nojitter [IA64] Disables jitter checking for ITC timers.
1336 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1338 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1340 noltlbs [PPC] Do not use large page/tlb entries for kernel
1341 lowmem mapping on PPC40x.
1343 nomca [IA-64] Disable machine check abort handling
1345 nomce [X86-32] Machine Check Exception
1347 nomfgpt [X86-32] Disable Multi-Function General Purpose
1348 Timer usage (for AMD Geode machines).
1350 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1352 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1353 with UP alternatives
1355 noresidual [PPC] Don't use residual data on PReP machines.
1357 noresume [SWSUSP] Disables resume and restores original swap
1358 space.
1360 no-scroll [VGA] Disables scrollback.
1361 This is required for the Braillex ib80-piezo Braille
1362 reader made by F.H. Papenmeier (Germany).
1364 nosbagart [IA-64]
1366 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1368 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1369 and disable the IO APIC. legacy for "maxcpus=0".
1371 nosoftlockup [KNL] Disable the soft-lockup detector.
1373 nosync [HW,M68K] Disables sync negotiation for all devices.
1375 notsc [BUGS=X86-32] Disable Time Stamp Counter
1377 nousb [USB] Disable the USB subsystem
1379 nowb [ARM]
1381 nptcg= [IA64] Override max number of concurrent global TLB
1382 purges which is reported from either PAL_VM_SUMMARY or
1383 SAL PALO.
1385 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1386 one of ['zone', 'node', 'default'] can be specified
1387 This can be set from sysctl after boot.
1388 See Documentation/sysctl/vm.txt for details.
1390 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1392 opl3= [HW,OSS]
1393 Format: <io>
1395 oprofile.timer= [HW]
1396 Use timer interrupt instead of performance counters
1398 osst= [HW,SCSI] SCSI Tape Driver
1399 Format: <buffer_size>,<write_threshold>
1400 See also Documentation/scsi/st.txt.
1402 panic= [KNL] Kernel behaviour on panic
1403 Format: <timeout>
1405 parkbd.port= [HW] Parallel port number the keyboard adapter is
1406 connected to, default is 0.
1407 Format: <parport#>
1408 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1409 0 for XT, 1 for AT (default is AT).
1410 Format: <mode>
1412 parport= [HW,PPT] Specify parallel ports. 0 disables.
1413 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1414 Use 'auto' to force the driver to use any
1415 IRQ/DMA settings detected (the default is to
1416 ignore detected IRQ/DMA settings because of
1417 possible conflicts). You can specify the base
1418 address, IRQ, and DMA settings; IRQ and DMA
1419 should be numbers, or 'auto' (for using detected
1420 settings on that particular port), or 'nofifo'
1421 (to avoid using a FIFO even if it is detected).
1422 Parallel ports are assigned in the order they
1423 are specified on the command line, starting
1424 with parport0.
1426 parport_init_mode= [HW,PPT]
1427 Configure VIA parallel port to operate in
1428 a specific mode. This is necessary on Pegasos
1429 computer where firmware has no options for setting
1430 up parallel port mode and sets it to spp.
1431 Currently this function knows 686a and 8231 chips.
1432 Format: [spp|ps2|epp|ecp|ecpepp]
1434 pas2= [HW,OSS] Format:
1435 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1437 pas16= [HW,SCSI]
1438 See header of drivers/scsi/pas16.c.
1440 pause_on_oops=
1441 Halt all CPUs after the first oops has been printed for
1442 the specified number of seconds. This is to be used if
1443 your oopses keep scrolling off the screen.
1445 pcbit= [HW,ISDN]
1447 pcd. [PARIDE]
1448 See header of drivers/block/paride/pcd.c.
1449 See also Documentation/paride.txt.
1451 pci=option[,option...] [PCI] various PCI subsystem options:
1452 off [X86-32] don't probe for the PCI bus
1453 bios [X86-32] force use of PCI BIOS, don't access
1454 the hardware directly. Use this if your machine
1455 has a non-standard PCI host bridge.
1456 nobios [X86-32] disallow use of PCI BIOS, only direct
1457 hardware access methods are allowed. Use this
1458 if you experience crashes upon bootup and you
1459 suspect they are caused by the BIOS.
1460 conf1 [X86-32] Force use of PCI Configuration
1461 Mechanism 1.
1462 conf2 [X86-32] Force use of PCI Configuration
1463 Mechanism 2.
1464 noaer [PCIE] If the PCIEAER kernel config parameter is
1465 enabled, this kernel boot option can be used to
1466 disable the use of PCIE advanced error reporting.
1467 nodomains [PCI] Disable support for multiple PCI
1468 root domains (aka PCI segments, in ACPI-speak).
1469 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1470 Configuration
1471 nomsi [MSI] If the PCI_MSI kernel config parameter is
1472 enabled, this kernel boot option can be used to
1473 disable the use of MSI interrupts system-wide.
1474 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1475 routing table. These calls are known to be buggy
1476 on several machines and they hang the machine
1477 when used, but on other computers it's the only
1478 way to get the interrupt routing table. Try
1479 this option if the kernel is unable to allocate
1480 IRQs or discover secondary PCI buses on your
1481 motherboard.
1482 rom [X86-32] Assign address space to expansion ROMs.
1483 Use with caution as certain devices share
1484 address decoders between ROMs and other
1485 resources.
1486 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1487 assigned automatically to PCI devices. You can
1488 make the kernel exclude IRQs of your ISA cards
1489 this way.
1490 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1491 of the PIRQ table (normally generated
1492 by the BIOS) if it is outside the
1493 F0000h-100000h range.
1494 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1495 useful if the kernel is unable to find your
1496 secondary buses and you want to tell it
1497 explicitly which ones they are.
1498 assign-busses [X86-32] Always assign all PCI bus
1499 numbers ourselves, overriding
1500 whatever the firmware may have done.
1501 usepirqmask [X86-32] Honor the possible IRQ mask stored
1502 in the BIOS $PIR table. This is needed on
1503 some systems with broken BIOSes, notably
1504 some HP Pavilion N5400 and Omnibook XE3
1505 notebooks. This will have no effect if ACPI
1506 IRQ routing is enabled.
1507 noacpi [X86-32] Do not use ACPI for IRQ routing
1508 or for PCI scanning.
1509 use_crs [X86-32] Use _CRS for PCI resource
1510 allocation.
1511 routeirq Do IRQ routing for all PCI devices.
1512 This is normally done in pci_enable_device(),
1513 so this option is a temporary workaround
1514 for broken drivers that don't call it.
1515 firmware [ARM] Do not re-enumerate the bus but instead
1516 just use the configuration from the
1517 bootloader. This is currently used on
1518 IXP2000 systems where the bus has to be
1519 configured a certain way for adjunct CPUs.
1520 noearly [X86] Don't do any early type 1 scanning.
1521 This might help on some broken boards which
1522 machine check when some devices' config space
1523 is read. But various workarounds are disabled
1524 and some IOMMU drivers will not work.
1525 bfsort Sort PCI devices into breadth-first order.
1526 This sorting is done to get a device
1527 order compatible with older (<= 2.4) kernels.
1528 nobfsort Don't sort PCI devices into breadth-first order.
1529 cbiosize=nn[KMG] The fixed amount of bus space which is
1530 reserved for the CardBus bridge's IO window.
1531 The default value is 256 bytes.
1532 cbmemsize=nn[KMG] The fixed amount of bus space which is
1533 reserved for the CardBus bridge's memory
1534 window. The default value is 64 megabytes.
1536 pcmv= [HW,PCMCIA] BadgePAD 4
1538 pd. [PARIDE]
1539 See Documentation/paride.txt.
1541 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1542 boot time.
1543 Format: { 0 | 1 }
1544 See arch/parisc/kernel/pdc_chassis.c
1546 pf. [PARIDE]
1547 See Documentation/paride.txt.
1549 pg. [PARIDE]
1550 See Documentation/paride.txt.
1552 pirq= [SMP,APIC] Manual mp-table setup
1553 See Documentation/i386/IO-APIC.txt.
1555 plip= [PPT,NET] Parallel port network link
1556 Format: { parport<nr> | timid | 0 }
1557 See also Documentation/parport.txt.
1559 pnpacpi= [ACPI]
1560 { off }
1562 pnpbios= [ISAPNP]
1563 { on | off | curr | res | no-curr | no-res }
1565 pnp_reserve_irq=
1566 [ISAPNP] Exclude IRQs for the autoconfiguration
1568 pnp_reserve_dma=
1569 [ISAPNP] Exclude DMAs for the autoconfiguration
1571 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1572 Ranges are in pairs (I/O port base and size).
1574 pnp_reserve_mem=
1575 [ISAPNP] Exclude memory regions for the
1576 autoconfiguration.
1577 Ranges are in pairs (memory base and size).
1579 print-fatal-signals=
1580 [KNL] debug: print fatal signals
1581 print-fatal-signals=1: print segfault info to
1582 the kernel console.
1583 default: off.
1585 printk.time= Show timing data prefixed to each printk message line
1586 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1588 profile= [KNL] Enable kernel profiling via /proc/profile
1589 Format: [schedule,]<number>
1590 Param: "schedule" - profile schedule points.
1591 Param: <number> - step/bucket size as a power of 2 for
1592 statistical time based profiling.
1593 Param: "sleep" - profile D-state sleeping (millisecs).
1594 Requires CONFIG_SCHEDSTATS
1595 Param: "kvm" - profile VM exits.
1597 processor.max_cstate= [HW,ACPI]
1598 Limit processor to maximum C-state
1599 max_cstate=9 overrides any DMI blacklist limit.
1601 processor.nocst [HW,ACPI]
1602 Ignore the _CST method to determine C-states,
1603 instead using the legacy FADT method
1605 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1606 before loading.
1607 See Documentation/ramdisk.txt.
1609 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1610 probe for; one of (bare|imps|exps|lifebook|any).
1611 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1612 per second.
1613 psmouse.resetafter= [HW,MOUSE]
1614 Try to reset the device after so many bad packets
1615 (0 = never).
1616 psmouse.resolution=
1617 [HW,MOUSE] Set desired mouse resolution, in dpi.
1618 psmouse.smartscroll=
1619 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1620 0 = disabled, 1 = enabled (default).
1622 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1623 Format:
1624 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1626 pt. [PARIDE]
1627 See Documentation/paride.txt.
1629 pty.legacy_count=
1630 [KNL] Number of legacy pty's. Overwrites compiled-in
1631 default number.
1633 quiet [KNL] Disable most log messages
1635 r128= [HW,DRM]
1637 raid= [HW,RAID]
1638 See Documentation/md.txt.
1640 ramdisk_blocksize= [RAM]
1641 See Documentation/ramdisk.txt.
1643 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1644 See Documentation/ramdisk.txt.
1646 rcupdate.blimit= [KNL,BOOT]
1647 Set maximum number of finished RCU callbacks to process
1648 in one batch.
1650 rcupdate.qhimark= [KNL,BOOT]
1651 Set threshold of queued
1652 RCU callbacks over which batch limiting is disabled.
1654 rcupdate.qlowmark= [KNL,BOOT]
1655 Set threshold of queued RCU callbacks below which
1656 batch limiting is re-enabled.
1658 rdinit= [KNL]
1659 Format: <full_path>
1660 Run specified binary instead of /init from the ramdisk,
1661 used for early userspace startup. See initrd.
1663 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1664 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1665 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1667 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1669 reservetop= [X86-32]
1670 Format: nn[KMG]
1671 Reserves a hole at the top of the kernel virtual
1672 address space.
1674 reset_devices [KNL] Force drivers to reset the underlying device
1675 during initialization.
1677 resume= [SWSUSP]
1678 Specify the partition device for software suspend
1680 resume_offset= [SWSUSP]
1681 Specify the offset from the beginning of the partition
1682 given by "resume=" at which the swap header is located,
1683 in <PAGE_SIZE> units (needed only for swap files).
1684 See Documentation/power/swsusp-and-swap-files.txt
1686 retain_initrd [RAM] Keep initrd memory after extraction
1688 rhash_entries= [KNL,NET]
1689 Set number of hash buckets for route cache
1691 riscom8= [HW,SERIAL]
1692 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1694 ro [KNL] Mount root device read-only on boot
1696 root= [KNL] Root filesystem
1698 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1699 mount the root filesystem
1701 rootflags= [KNL] Set root filesystem mount option string
1703 rootfstype= [KNL] Set root filesystem type
1705 rootwait [KNL] Wait (indefinitely) for root device to show up.
1706 Useful for devices that are detected asynchronously
1707 (e.g. USB and MMC devices).
1709 root_plug.vendor_id=
1710 [ROOTPLUG] Override the default vendor ID
1712 root_plug.product_id=
1713 [ROOTPLUG] Override the default product ID
1715 root_plug.debug=
1716 [ROOTPLUG] Enable debugging output
1718 rw [KNL] Mount root device read-write on boot
1720 S [KNL] Run init in single mode
1722 sa1100ir [NET]
1723 See drivers/net/irda/sa1100_ir.c.
1725 sbni= [NET] Granch SBNI12 leased line adapter
1727 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1728 Format: <io>[,<timeout>[,<isapnp>]]
1730 scsi_debug_*= [SCSI]
1731 See drivers/scsi/scsi_debug.c.
1733 scsi_default_dev_flags=
1734 [SCSI] SCSI default device flags
1735 Format: <integer>
1737 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1738 Format: <vendor>:<model>:<flags>
1739 (flags are integer value)
1741 scsi_logging_level= [SCSI] a bit mask of logging levels
1742 See drivers/scsi/scsi_logging.h for bits. Also
1743 settable via sysctl at dev.scsi.logging_level
1744 (/proc/sys/dev/scsi/logging_level).
1745 There is also a nice 'scsi_logging_level' script in the
1746 S390-tools package, available for download at
1747 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1749 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1750 discovered. async scans them in kernel threads,
1751 allowing boot to proceed. none ignores them, expecting
1752 user space to do the scan.
1754 selinux [SELINUX] Disable or enable SELinux at boot time.
1755 Format: { "0" | "1" }
1756 See security/selinux/Kconfig help text.
1757 0 -- disable.
1758 1 -- enable.
1759 Default value is set via kernel config option.
1760 If enabled at boot time, /selinux/disable can be used
1761 later to disable prior to initial policy load.
1763 selinux_compat_net =
1764 [SELINUX] Set initial selinux_compat_net flag value.
1765 Format: { "0" | "1" }
1766 0 -- use new secmark-based packet controls
1767 1 -- use legacy packet controls
1768 Default value is 0 (preferred).
1769 Value can be changed at runtime via
1770 /selinux/compat_net.
1772 serialnumber [BUGS=X86-32]
1774 shapers= [NET]
1775 Maximal number of shapers.
1777 sim710= [SCSI,HW]
1778 See header of drivers/scsi/sim710.c.
1780 simeth= [IA-64]
1781 simscsi=
1783 slram= [HW,MTD]
1785 slub_debug[=options[,slabs]] [MM, SLUB]
1786 Enabling slub_debug allows one to determine the
1787 culprit if slab objects become corrupted. Enabling
1788 slub_debug can create guard zones around objects and
1789 may poison objects when not in use. Also tracks the
1790 last alloc / free. For more information see
1791 Documentation/vm/slub.txt.
1793 slub_max_order= [MM, SLUB]
1794 Determines the maximum allowed order for slabs.
1795 A high setting may cause OOMs due to memory
1796 fragmentation. For more information see
1797 Documentation/vm/slub.txt.
1799 slub_min_objects= [MM, SLUB]
1800 The minimum number of objects per slab. SLUB will
1801 increase the slab order up to slub_max_order to
1802 generate a sufficiently large slab able to contain
1803 the number of objects indicated. The higher the number
1804 of objects the smaller the overhead of tracking slabs
1805 and the less frequently locks need to be acquired.
1806 For more information see Documentation/vm/slub.txt.
1808 slub_min_order= [MM, SLUB]
1809 Determines the mininum page order for slabs. Must be
1810 lower than slub_max_order.
1811 For more information see Documentation/vm/slub.txt.
1813 slub_nomerge [MM, SLUB]
1814 Disable merging of slabs with similar size. May be
1815 necessary if there is some reason to distinguish
1816 allocs to different slabs. Debug options disable
1817 merging on their own.
1818 For more information see Documentation/vm/slub.txt.
1820 smart2= [HW]
1821 Format: <io1>[,<io2>[,...,<io8>]]
1823 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1824 attempt to substitute SMP alternatives once at boot.
1826 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1827 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1828 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1829 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1830 smsc-ircc2.ircc_irq= [HW] IRQ line
1831 smsc-ircc2.ircc_dma= [HW] DMA channel
1832 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1833 0: Toshiba Satellite 1800 (GP data pin select)
1834 1: Fast pin select (default)
1835 2: ATC IRMode
1837 snd-ad1816a= [HW,ALSA]
1839 snd-ad1848= [HW,ALSA]
1841 snd-ali5451= [HW,ALSA]
1843 snd-als100= [HW,ALSA]
1845 snd-als4000= [HW,ALSA]
1847 snd-azt2320= [HW,ALSA]
1849 snd-cmi8330= [HW,ALSA]
1851 snd-cmipci= [HW,ALSA]
1853 snd-cs4231= [HW,ALSA]
1855 snd-cs4232= [HW,ALSA]
1857 snd-cs4236= [HW,ALSA]
1859 snd-cs4281= [HW,ALSA]
1861 snd-cs46xx= [HW,ALSA]
1863 snd-dt019x= [HW,ALSA]
1865 snd-dummy= [HW,ALSA]
1867 snd-emu10k1= [HW,ALSA]
1869 snd-ens1370= [HW,ALSA]
1871 snd-ens1371= [HW,ALSA]
1873 snd-es968= [HW,ALSA]
1875 snd-es1688= [HW,ALSA]
1877 snd-es18xx= [HW,ALSA]
1879 snd-es1938= [HW,ALSA]
1881 snd-es1968= [HW,ALSA]
1883 snd-fm801= [HW,ALSA]
1885 snd-gusclassic= [HW,ALSA]
1887 snd-gusextreme= [HW,ALSA]
1889 snd-gusmax= [HW,ALSA]
1891 snd-hdsp= [HW,ALSA]
1893 snd-ice1712= [HW,ALSA]
1895 snd-intel8x0= [HW,ALSA]
1897 snd-interwave= [HW,ALSA]
1899 snd-interwave-stb=
1900 [HW,ALSA]
1902 snd-korg1212= [HW,ALSA]
1904 snd-maestro3= [HW,ALSA]
1906 snd-mpu401= [HW,ALSA]
1908 snd-mtpav= [HW,ALSA]
1910 snd-nm256= [HW,ALSA]
1912 snd-opl3sa2= [HW,ALSA]
1914 snd-opti92x-ad1848=
1915 [HW,ALSA]
1917 snd-opti92x-cs4231=
1918 [HW,ALSA]
1920 snd-opti93x= [HW,ALSA]
1922 snd-pmac= [HW,ALSA]
1924 snd-rme32= [HW,ALSA]
1926 snd-rme96= [HW,ALSA]
1928 snd-rme9652= [HW,ALSA]
1930 snd-sb8= [HW,ALSA]
1932 snd-sb16= [HW,ALSA]
1934 snd-sbawe= [HW,ALSA]
1936 snd-serial= [HW,ALSA]
1938 snd-sgalaxy= [HW,ALSA]
1940 snd-sonicvibes= [HW,ALSA]
1942 snd-sun-amd7930=
1943 [HW,ALSA]
1945 snd-sun-cs4231= [HW,ALSA]
1947 snd-trident= [HW,ALSA]
1949 snd-usb-audio= [HW,ALSA,USB]
1951 snd-via82xx= [HW,ALSA]
1953 snd-virmidi= [HW,ALSA]
1955 snd-wavefront= [HW,ALSA]
1957 snd-ymfpci= [HW,ALSA]
1959 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1960 See Documentation/sonypi.txt
1962 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1963 See Documentation/specialix.txt.
1965 spia_io_base= [HW,MTD]
1966 spia_fio_base=
1967 spia_pedr=
1968 spia_peddr=
1970 sscape= [HW,OSS]
1971 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1973 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1974 See Documentation/scsi/st.txt.
1976 sti= [PARISC,HW]
1977 Format: <num>
1978 Set the STI (builtin display/keyboard on the HP-PARISC
1979 machines) console (graphic card) which should be used
1980 as the initial boot-console.
1981 See also comment in drivers/video/console/sticore.c.
1983 sti_font= [HW]
1984 See comment in drivers/video/console/sticore.c.
1986 stifb= [HW]
1987 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1989 sunrpc.pool_mode=
1990 [NFS]
1991 Control how the NFS server code allocates CPUs to
1992 service thread pools. Depending on how many NICs
1993 you have and where their interrupts are bound, this
1994 option will affect which CPUs will do NFS serving.
1995 Note: this parameter cannot be changed while the
1996 NFS server is running.
1998 auto the server chooses an appropriate mode
1999 automatically using heuristics
2000 global a single global pool contains all CPUs
2001 percpu one pool for each CPU
2002 pernode one pool for each NUMA node (equivalent
2003 to global on non-NUMA machines)
2005 swiotlb= [IA-64] Number of I/O TLB slabs
2007 switches= [HW,M68k]
2009 sym53c416= [HW,SCSI]
2010 See header of drivers/scsi/sym53c416.c.
2012 sysrq_always_enabled
2013 [KNL]
2014 Ignore sysrq setting - this boot parameter will
2015 neutralize any effect of /proc/sys/kernel/sysrq.
2016 Useful for debugging.
2018 t128= [HW,SCSI]
2019 See header of drivers/scsi/t128.c.
2021 tdfx= [HW,DRM]
2023 thash_entries= [KNL,NET]
2024 Set number of hash buckets for TCP connection
2026 thermal.act= [HW,ACPI]
2027 -1: disable all active trip points in all thermal zones
2028 <degrees C>: override all lowest active trip points
2030 thermal.crt= [HW,ACPI]
2031 -1: disable all critical trip points in all thermal zones
2032 <degrees C>: lower all critical trip points
2034 thermal.nocrt= [HW,ACPI]
2035 Set to disable actions on ACPI thermal zone
2036 critical and hot trip points.
2038 thermal.off= [HW,ACPI]
2039 1: disable ACPI thermal control
2041 thermal.psv= [HW,ACPI]
2042 -1: disable all passive trip points
2043 <degrees C>: override all passive trip points to this value
2045 thermal.tzp= [HW,ACPI]
2046 Specify global default ACPI thermal zone polling rate
2047 <deci-seconds>: poll all this frequency
2048 0: no polling (default)
2050 tipar.timeout= [HW,PPT]
2051 Set communications timeout in tenths of a second
2052 (default 15).
2054 tipar.delay= [HW,PPT]
2055 Set inter-bit delay in microseconds (default 10).
2057 tmscsim= [HW,SCSI]
2058 See comment before function dc390_setup() in
2059 drivers/scsi/tmscsim.c.
2061 tp720= [HW,PS2]
2063 trix= [HW,OSS] MediaTrix AudioTrix Pro
2064 Format:
2065 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2067 turbografx.map[2|3]= [HW,JOY]
2068 TurboGraFX parallel port interface
2069 Format:
2070 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2071 See also Documentation/input/joystick-parport.txt
2073 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2074 See header of drivers/scsi/u14-34f.c.
2076 uart401= [HW,OSS]
2077 Format: <io>,<irq>
2079 uart6850= [HW,OSS]
2080 Format: <io>,<irq>
2082 uhci-hcd.ignore_oc=
2083 [USB] Ignore overcurrent events (default N).
2084 Some badly-designed motherboards generate lots of
2085 bogus events, for ports that aren't wired to
2086 anything. Set this parameter to avoid log spamming.
2087 Note that genuine overcurrent events won't be
2088 reported either.
2090 usbcore.autosuspend=
2091 [USB] The autosuspend time delay (in seconds) used
2092 for newly-detected USB devices (default 2). This
2093 is the time required before an idle device will be
2094 autosuspended. Devices for which the delay is set
2095 to a negative value won't be autosuspended at all.
2097 usbhid.mousepoll=
2098 [USBHID] The interval which mice are to be polled at.
2100 vdso= [X86-32,SH,x86-64]
2101 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2102 vdso=1: enable VDSO (default)
2103 vdso=0: disable VDSO mapping
2105 vdso32= [X86-32,X86-64]
2106 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2107 vdso32=1: enable 32-bit VDSO (default)
2108 vdso32=0: disable 32-bit VDSO mapping
2110 vector= [IA-64,SMP]
2111 vector=percpu: enable percpu vector domain
2113 video= [FB] Frame buffer configuration
2114 See Documentation/fb/modedb.txt.
2116 vga= [BOOT,X86-32] Select a particular video mode
2117 See Documentation/i386/boot.txt and
2118 Documentation/svga.txt.
2119 Use vga=ask for menu.
2120 This is actually a boot loader parameter; the value is
2121 passed to the kernel using a special protocol.
2123 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2124 size of <nn>. This can be used to increase the
2125 minimum size (128MB on x86). It can also be used to
2126 decrease the size and leave more room for directly
2127 mapped kernel RAM.
2129 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2130 Format: <command>
2132 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2133 Format: <command>
2135 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2136 Format: <command>
2138 waveartist= [HW,OSS]
2139 Format: <io>,<irq>,<dma>,<dma2>
2141 wd33c93= [HW,SCSI]
2142 See header of drivers/scsi/wd33c93.c.
2144 wd7000= [HW,SCSI]
2145 See header of drivers/scsi/wd7000.c.
2147 wdt= [WDT] Watchdog
2148 See Documentation/watchdog/wdt.txt.
2150 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2151 xd_geo= See header of drivers/block/xd.c.
2153 xirc2ps_cs= [NET,PCMCIA]
2154 Format:
2155 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2157 norandmaps Don't use address space randomization
2158 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2160 ______________________________________________________________________
2162 TODO:
2164 Add documentation for ALSA options.
2165 Add more DRM drivers.