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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 AX25 Appropriate AX.25 support is enabled.
38 BLACKFIN Blackfin architecture is enabled.
39 DRM Direct Rendering Management support is enabled.
40 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
41 EFI EFI Partitioning (GPT) is enabled
42 EIDE EIDE/ATAPI support is enabled.
43 FB The frame buffer device is enabled.
44 HW Appropriate hardware is enabled.
45 IA-64 IA-64 architecture is enabled.
46 IOSCHED More than one I/O scheduler is enabled.
47 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
48 ISAPNP ISA PnP code is enabled.
49 ISDN Appropriate ISDN support is enabled.
50 JOY Appropriate joystick support is enabled.
51 LIBATA Libata driver is enabled
52 LP Printer support is enabled.
53 LOOP Loopback device support is enabled.
54 M68k M68k architecture is enabled.
55 These options have more detailed description inside of
56 Documentation/m68k/kernel-options.txt.
57 MCA MCA bus support is enabled.
58 MDA MDA console support is enabled.
59 MOUSE Appropriate mouse support is enabled.
60 MSI Message Signaled Interrupts (PCI).
61 MTD MTD (Memory Technology Device) support is enabled.
62 NET Appropriate network support is enabled.
63 NUMA NUMA support is enabled.
64 GENERIC_TIME The generic timeofday code is enabled.
65 NFS Appropriate NFS support is enabled.
66 OSS OSS sound support is enabled.
67 PV_OPS A paravirtualized kernel is enabled.
68 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
69 PARISC The PA-RISC architecture is enabled.
70 PCI PCI bus support is enabled.
71 PCIE PCI Express support is enabled.
72 PCMCIA The PCMCIA subsystem is enabled.
73 PNP Plug & Play support is enabled.
74 PPC PowerPC architecture is enabled.
75 PPT Parallel port support is enabled.
76 PS2 Appropriate PS/2 support is enabled.
77 RAM RAM disk support is enabled.
78 S390 S390 architecture is enabled.
79 SCSI Appropriate SCSI support is enabled.
80 A lot of drivers has their options described inside of
81 Documentation/scsi/.
82 SELINUX SELinux support is enabled.
83 SERIAL Serial support is enabled.
84 SH SuperH architecture is enabled.
85 SMP The kernel is an SMP kernel.
86 SPARC Sparc architecture is enabled.
87 SWSUSP Software suspend is enabled.
88 TS Appropriate touchscreen support is enabled.
89 USB USB support is enabled.
90 USBHID USB Human Interface Device support is enabled.
91 V4L Video For Linux support is enabled.
92 VGA The VGA console has been enabled.
93 VT Virtual terminal support is enabled.
94 WDT Watchdog support is enabled.
95 XT IBM PC/XT MFM hard disk support is enabled.
96 X86-32 X86-32, aka i386 architecture is enabled.
97 X86-64 X86-64 architecture is enabled.
98 More X86-64 boot options can be found in
99 Documentation/x86_64/boot-options.txt .
101 In addition, the following text indicates that the option:
103 BUGS= Relates to possible processor bugs on the said processor.
104 KNL Is a kernel start-up parameter.
105 BOOT Is a boot loader parameter.
107 Parameters denoted with BOOT are actually interpreted by the boot
108 loader, and have no meaning to the kernel directly.
109 Do not modify the syntax of boot loader parameters without extreme
110 need or coordination with <Documentation/i386/boot.txt>.
112 There are also arch-specific kernel-parameters not documented here.
113 See for example <Documentation/x86_64/boot-options.txt>.
115 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
116 a trailing = on the name of any parameter states that that parameter will
117 be entered as an environment variable, whereas its absence indicates that
118 it will appear as a kernel argument readable via /proc/cmdline by programs
119 running once the system is up.
121 The number of kernel parameters is not limited, but the length of the
122 complete command line (parameters including spaces etc.) is limited to
123 a fixed number of characters. This limit depends on the architecture
124 and is between 256 and 4096 characters. It is defined in the file
125 ./include/asm/setup.h as COMMAND_LINE_SIZE.
128 acpi= [HW,ACPI,X86-64,i386]
129 Advanced Configuration and Power Interface
130 Format: { force | off | ht | strict | noirq }
131 force -- enable ACPI if default was off
132 off -- disable ACPI if default was on
133 noirq -- do not use ACPI for IRQ routing
134 ht -- run only enough ACPI to enable Hyper Threading
135 strict -- Be less tolerant of platforms that are not
136 strictly ACPI specification compliant.
138 See also Documentation/pm.txt, pci=noacpi
140 acpi_apic_instance= [ACPI, IOAPIC]
141 Format: <int>
142 2: use 2nd APIC table, if available
143 1,0: use 1st APIC table
144 default: 0
146 acpi_sleep= [HW,ACPI] Sleep options
147 Format: { s3_bios, s3_mode }
148 See Documentation/power/video.txt
150 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
151 Format: { level | edge | high | low }
153 acpi_irq_balance [HW,ACPI]
154 ACPI will balance active IRQs
155 default in APIC mode
157 acpi_irq_nobalance [HW,ACPI]
158 ACPI will not move active IRQs (default)
159 default in PIC mode
161 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
162 use by PCI
163 Format: <irq>,<irq>...
165 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
166 Format: <irq>,<irq>...
168 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
170 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
171 Format: To spoof as Windows 98: ="Microsoft Windows"
173 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
174 acpi_osi="string1" # add string1 -- only one string
175 acpi_osi="!string2" # remove built-in string2
176 acpi_osi= # disable all strings
178 acpi_serialize [HW,ACPI] force serialization of AML methods
180 acpi_skip_timer_override [HW,ACPI]
181 Recognize and ignore IRQ0/pin2 Interrupt Override.
182 For broken nForce2 BIOS resulting in XT-PIC timer.
183 acpi_use_timer_override [HW,ACPI}
184 Use timer override. For some broken Nvidia NF5 boards
185 that require a timer override, but don't have
186 HPET
188 acpi.debug_layer= [HW,ACPI]
189 Format: <int>
190 Each bit of the <int> indicates an ACPI debug layer,
191 1: enable, 0: disable. It is useful for boot time
192 debugging. After system has booted up, it can be set
193 via /sys/module/acpi/parameters/debug_layer.
194 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
195 Available bits (add the numbers together) to enable debug output
196 for specific parts of the ACPI subsystem:
197 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
198 0x10 namespace 0x20 parser 0x40 dispatcher
199 0x80 executer 0x100 resources 0x200 acpica debugger
200 0x400 os services 0x800 acpica disassembler.
201 The number can be in decimal or prefixed with 0x in hex.
202 Warning: Many of these options can produce a lot of
203 output and make your system unusable. Be very careful.
205 acpi.debug_level= [HW,ACPI]
206 Format: <int>
207 Each bit of the <int> indicates an ACPI debug level,
208 1: enable, 0: disable. It is useful for boot time
209 debugging. After system has booted up, it can be set
210 via /sys/module/acpi/parameters/debug_level.
211 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
212 Available bits (add the numbers together) to enable different
213 debug output levels of the ACPI subsystem:
214 0x01 error 0x02 warn 0x04 init 0x08 debug object
215 0x10 info 0x20 init names 0x40 parse 0x80 load
216 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
217 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
218 0x10000 resources 0x20000 user requests 0x40000 package.
219 The number can be in decimal or prefixed with 0x in hex.
220 Warning: Many of these options can produce a lot of
221 output and make your system unusable. Be very careful.
224 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
226 acpi_pm_good [X86-32,X86-64]
227 Override the pmtimer bug detection: force the kernel
228 to assume that this machine's pmtimer latches its value
229 and always returns good values.
231 agp= [AGP]
232 { off | try_unsupported }
233 off: disable AGP support
234 try_unsupported: try to drive unsupported chipsets
235 (may crash computer or cause data corruption)
237 enable_timer_pin_1 [i386,x86-64]
238 Enable PIN 1 of APIC timer
239 Can be useful to work around chipset bugs
240 (in particular on some ATI chipsets).
241 The kernel tries to set a reasonable default.
243 disable_timer_pin_1 [i386,x86-64]
244 Disable PIN 1 of APIC timer
245 Can be useful to work around chipset bugs.
247 ad1848= [HW,OSS]
248 Format: <io>,<irq>,<dma>,<dma2>,<type>
250 advansys= [HW,SCSI]
251 See header of drivers/scsi/advansys.c.
253 advwdt= [HW,WDT] Advantech WDT
254 Format: <iostart>,<iostop>
256 aedsp16= [HW,OSS] Audio Excel DSP 16
257 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
258 See also header of sound/oss/aedsp16.c.
260 aha152x= [HW,SCSI]
261 See Documentation/scsi/aha152x.txt.
263 aha1542= [HW,SCSI]
264 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
266 aic7xxx= [HW,SCSI]
267 See Documentation/scsi/aic7xxx.txt.
269 aic79xx= [HW,SCSI]
270 See Documentation/scsi/aic79xx.txt.
272 amijoy.map= [HW,JOY] Amiga joystick support
273 Map of devices attached to JOY0DAT and JOY1DAT
274 Format: <a>,<b>
275 See also Documentation/kernel/input/joystick.txt
277 analog.map= [HW,JOY] Analog joystick and gamepad support
278 Specifies type or capabilities of an analog joystick
279 connected to one of 16 gameports
280 Format: <type1>,<type2>,..<type16>
282 apc= [HW,SPARC]
283 Power management functions (SPARCstation-4/5 + deriv.)
284 Format: noidle
285 Disable APC CPU standby support. SPARCstation-Fox does
286 not play well with APC CPU idle - disable it if you have
287 APC and your system crashes randomly.
289 apic= [APIC,i386] Advanced Programmable Interrupt Controller
290 Change the output verbosity whilst booting
291 Format: { quiet (default) | verbose | debug }
292 Change the amount of debugging information output
293 when initialising the APIC and IO-APIC components.
295 apm= [APM] Advanced Power Management
296 See header of arch/i386/kernel/apm.c.
298 applicom= [HW]
299 Format: <mem>,<irq>
301 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
302 Format: <io>,<irq>,<nodeID>
304 ataflop= [HW,M68k]
306 atarimouse= [HW,MOUSE] Atari Mouse
308 atascsi= [HW,SCSI] Atari SCSI
310 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
311 EzKey and similar keyboards
313 atkbd.reset= [HW] Reset keyboard during initialization
315 atkbd.set= [HW] Select keyboard code set
316 Format: <int> (2 = AT (default), 3 = PS/2)
318 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
319 keyboards
321 atkbd.softraw= [HW] Choose between synthetic and real raw mode
322 Format: <bool> (0 = real, 1 = synthetic (default))
324 atkbd.softrepeat= [HW]
325 Use software keyboard repeat
327 autotest [IA64]
329 baycom_epp= [HW,AX25]
330 Format: <io>,<mode>
332 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
333 Format: <io>,<mode>
334 See header of drivers/net/hamradio/baycom_par.c.
336 baycom_ser_fdx= [HW,AX25]
337 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
338 Format: <io>,<irq>,<mode>[,<baud>]
339 See header of drivers/net/hamradio/baycom_ser_fdx.c.
341 baycom_ser_hdx= [HW,AX25]
342 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
343 Format: <io>,<irq>,<mode>
344 See header of drivers/net/hamradio/baycom_ser_hdx.c.
346 blkmtd_device= [HW,MTD]
347 blkmtd_erasesz=
348 blkmtd_ro=
349 blkmtd_bs=
350 blkmtd_count=
352 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
353 bttv.radio= Most important insmod options are available as
354 kernel args too.
355 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
356 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
358 BusLogic= [HW,SCSI]
359 See drivers/scsi/BusLogic.c, comment before function
360 BusLogic_ParseDriverOptions().
362 c101= [NET] Moxa C101 synchronous serial card
364 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
365 Sometimes CPU hardware bugs make them report the cache
366 size incorrectly. The kernel will attempt work arounds
367 to fix known problems, but for some CPUs it is not
368 possible to determine what the correct size should be.
369 This option provides an override for these situations.
371 chandev= [HW,NET] Generic channel device initialisation
373 checkreqprot [SELINUX] Set initial checkreqprot flag value.
374 Format: { "0" | "1" }
375 See security/selinux/Kconfig help text.
376 0 -- check protection applied by kernel (includes
377 any implied execute protection).
378 1 -- check protection requested by application.
379 Default value is set via a kernel config option.
380 Value can be changed at runtime via
381 /selinux/checkreqprot.
383 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
384 [Deprecated]
385 Forces specified clocksource (if available) to be used
386 when calculating gettimeofday(). If specified
387 clocksource is not available, it defaults to PIT.
388 Format: { pit | tsc | cyclone | pmtmr }
390 clocksource= [GENERIC_TIME] Override the default clocksource
391 Format: <string>
392 Override the default clocksource and use the clocksource
393 with the name specified.
394 Some clocksource names to choose from, depending on
395 the platform:
396 [all] jiffies (this is the base, fallback clocksource)
397 [ACPI] acpi_pm
398 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
399 pxa_timer,timer3,32k_counter,timer0_1
400 [AVR32] avr32
401 [X86-32] pit,hpet,tsc,vmi-timer;
402 scx200_hrt on Geode; cyclone on IBM x440
403 [MIPS] MIPS
404 [PARISC] cr16
405 [S390] tod
406 [SH] SuperH
407 [SPARC64] tick
408 [X86-64] hpet,tsc
410 code_bytes [IA32] How many bytes of object code to print in an
411 oops report.
412 Range: 0 - 8192
413 Default: 64
415 disable_8254_timer
416 enable_8254_timer
417 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
418 over the 8254 in addition to over the IO-APIC. The
419 kernel tries to set a sensible default.
421 hpet= [X86-32,HPET] option to disable HPET and use PIT.
422 Format: disable
424 com20020= [HW,NET] ARCnet - COM20020 chipset
425 Format:
426 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
428 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
429 Format: <io>[,<irq>]
431 com90xx= [HW,NET]
432 ARCnet - COM90xx chipset (memory-mapped buffers)
433 Format: <io>[,<irq>[,<memstart>]]
435 condev= [HW,S390] console device
436 conmode=
438 console= [KNL] Output console device and options.
440 tty<n> Use the virtual console device <n>.
442 ttyS<n>[,options]
443 ttyUSB0[,options]
444 Use the specified serial port. The options are of
445 the form "bbbbpnf", where "bbbb" is the baud rate,
446 "p" is parity ("n", "o", or "e"), "n" is number of
447 bits, and "f" is flow control ("r" for RTS or
448 omit it). Default is "9600n8".
450 See Documentation/serial-console.txt for more
451 information. See
452 Documentation/networking/netconsole.txt for an
453 alternative.
455 uart[8250],io,<addr>[,options]
456 uart[8250],mmio,<addr>[,options]
457 Start an early, polled-mode console on the 8250/16550
458 UART at the specified I/O port or MMIO address,
459 switching to the matching ttyS device later. The
460 options are the same as for ttyS, above.
462 earlycon= [KNL] Output early console device and options.
463 uart[8250],io,<addr>[,options]
464 uart[8250],mmio,<addr>[,options]
465 Start an early, polled-mode console on the 8250/16550
466 UART at the specified I/O port or MMIO address.
467 The options are the same as for ttyS, above.
469 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
470 Format:
471 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
473 crashkernel=nn[KMG]@ss[KMG]
474 [KNL] Reserve a chunk of physical memory to
475 hold a kernel to switch to with kexec on panic.
477 cs4232= [HW,OSS]
478 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
480 cs89x0_dma= [HW,NET]
481 Format: <dma>
483 cs89x0_media= [HW,NET]
484 Format: { rj45 | aui | bnc }
486 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
488 dasd= [HW,NET]
489 See header of drivers/s390/block/dasd_devmap.c.
491 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
492 (one device per port)
493 Format: <port#>,<type>
494 See also Documentation/input/joystick-parport.txt
496 debug [KNL] Enable kernel debugging (events log level).
498 debug_locks_verbose=
499 [KNL] verbose self-tests
500 Format=<0|1>
501 Print debugging info while doing the locking API
502 self-tests.
503 We default to 0 (no extra messages), setting it to
504 1 will print _a lot_ more information - normally
505 only useful to kernel developers.
507 decnet= [HW,NET]
508 Format: <area>[,<node>]
509 See also Documentation/networking/decnet.txt.
511 default_blu= [VT]
512 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
513 Change the default blue palette of the console.
514 This is a 16-member array composed of values
515 ranging from 0-255.
517 default_grn= [VT]
518 Format: <green0>,<green1>,<green2>,...,<green15>
519 Change the default green palette of the console.
520 This is a 16-member array composed of values
521 ranging from 0-255.
523 default_red= [VT]
524 Format: <red0>,<red1>,<red2>,...,<red15>
525 Change the default red palette of the console.
526 This is a 16-member array composed of values
527 ranging from 0-255.
529 default_utf8= [VT]
530 Format=<0|1>
531 Set system-wide default UTF-8 mode for all tty's.
532 Default is 0 and by setting to 1, it enables UTF-8
533 mode for all newly opened or allocated terminals.
535 dhash_entries= [KNL]
536 Set number of hash buckets for dentry cache.
538 digi= [HW,SERIAL]
539 IO parameters + enable/disable command.
541 digiepca= [HW,SERIAL]
542 See drivers/char/README.epca and
543 Documentation/digiepca.txt.
545 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
546 support available.
547 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
549 dmasound= [HW,OSS] Sound subsystem buffers
551 dscc4.setup= [NET]
553 dtc3181e= [HW,SCSI]
555 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
556 earlyprintk=vga
557 earlyprintk=serial[,ttySn[,baudrate]]
559 Append ",keep" to not disable it when the real console
560 takes over.
562 Only vga or serial at a time, not both.
564 Currently only ttyS0 and ttyS1 are supported.
566 Interaction with the standard serial driver is not
567 very good.
569 The VGA output is eventually overwritten by the real
570 console.
572 eata= [HW,SCSI]
574 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
575 Format: <int>
576 0: polling mode
577 non-0: interrupt mode (default)
579 eda= [HW,PS2]
581 edb= [HW,PS2]
583 edd= [EDD]
584 Format: {"of[f]" | "sk[ipmbr]"}
585 See comment in arch/i386/boot/edd.S
587 eicon= [HW,ISDN]
588 Format: <id>,<membase>,<irq>
590 eisa_irq_edge= [PARISC,HW]
591 See header of drivers/parisc/eisa.c.
593 elanfreq= [X86-32]
594 See comment before function elanfreq_setup() in
595 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
597 elevator= [IOSCHED]
598 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
599 See Documentation/block/as-iosched.txt and
600 Documentation/block/deadline-iosched.txt for details.
602 elfcorehdr= [X86-32, X86_64]
603 Specifies physical address of start of kernel core
604 image elf header. Generally kexec loader will
605 pass this option to capture kernel.
606 See Documentation/kdump/kdump.txt for details.
608 enforcing [SELINUX] Set initial enforcing status.
609 Format: {"0" | "1"}
610 See security/selinux/Kconfig help text.
611 0 -- permissive (log only, no denials).
612 1 -- enforcing (deny and log).
613 Default value is 0.
614 Value can be changed at runtime via /selinux/enforce.
616 es1371= [HW,OSS]
617 Format: <spdif>,[<nomix>,[<amplifier>]]
618 See also header of sound/oss/es1371.c.
620 ether= [HW,NET] Ethernet cards parameters
621 This option is obsoleted by the "netdev=" option, which
622 has equivalent usage. See its documentation for details.
624 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
625 Format: <io>[,<irq>]
627 failslab=
628 fail_page_alloc=
629 fail_make_request=[KNL]
630 General fault injection mechanism.
631 Format: <interval>,<probability>,<space>,<times>
632 See also /Documentation/fault-injection/.
634 fd_mcs= [HW,SCSI]
635 See header of drivers/scsi/fd_mcs.c.
637 fdomain= [HW,SCSI]
638 See header of drivers/scsi/fdomain.c.
640 floppy= [HW]
641 See Documentation/floppy.txt.
643 gamecon.map[2|3]=
644 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
645 support via parallel port (up to 5 devices per port)
646 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
647 See also Documentation/input/joystick-parport.txt
649 gamma= [HW,DRM]
651 gdth= [HW,SCSI]
652 See header of drivers/scsi/gdth.c.
654 gpt [EFI] Forces disk with valid GPT signature but
655 invalid Protective MBR to be treated as GPT.
657 gvp11= [HW,SCSI]
659 hashdist= [KNL,NUMA] Large hashes allocated during boot
660 are distributed across NUMA nodes. Defaults on
661 for IA-64, off otherwise.
662 Format: 0 | 1 (for off | on)
664 hcl= [IA-64] SGI's Hardware Graph compatibility layer
666 hd= [EIDE] (E)IDE hard drive subsystem geometry
667 Format: <cyl>,<head>,<sect>
669 hd?= [HW] (E)IDE subsystem
670 hd?lun= See Documentation/ide.txt.
672 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
673 size of <nn>. This works even on boxes that have no
674 highmem otherwise. This also works to reduce highmem
675 size on bigger boxes.
677 highres= [KNL] Enable/disable high resolution timer mode.
678 Valid parameters: "on", "off"
679 Default: "on"
681 hisax= [HW,ISDN]
682 See Documentation/isdn/README.HiSax.
684 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
686 i8042.direct [HW] Put keyboard port into non-translated mode
687 i8042.dumbkbd [HW] Pretend that controller can only read data from
688 keyboard and cannot control its state
689 (Don't attempt to blink the leds)
690 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
691 i8042.nokbd [HW] Don't check/create keyboard port
692 i8042.nomux [HW] Don't check presence of an active multiplexing
693 controller
694 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
695 controllers
696 i8042.panicblink=
697 [HW] Frequency with which keyboard LEDs should blink
698 when kernel panics (default is 0.5 sec)
699 i8042.reset [HW] Reset the controller during init and cleanup
700 i8042.unlock [HW] Unlock (ignore) the keylock
702 i810= [HW,DRM]
704 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
705 indicates that the driver is running on unsupported
706 hardware.
707 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
708 does not match list of supported models.
709 i8k.power_status
710 [HW] Report power status in /proc/i8k
711 (disabled by default)
712 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
713 capability is set.
715 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
716 See Documentation/mca.txt.
718 icn= [HW,ISDN]
719 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
721 ide= [HW] (E)IDE subsystem
722 Format: ide=nodma or ide=doubler or ide=reverse
723 See Documentation/ide.txt.
725 ide?= [HW] (E)IDE subsystem
726 Format: ide?=noprobe or chipset specific parameters.
727 See Documentation/ide.txt.
729 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
730 See Documentation/ide.txt.
732 idle= [X86]
733 Format: idle=poll or idle=mwait
734 Poll forces a polling idle loop that can slightly improves the performance
735 of waking up a idle CPU, but will use a lot of power and make the system
736 run hot. Not recommended.
737 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
738 to not use it because it doesn't save as much power as a normal idle
739 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
740 as idle=poll.
742 ignore_loglevel [KNL]
743 Ignore loglevel setting - this will print /all/
744 kernel messages to the console. Useful for debugging.
746 ihash_entries= [KNL]
747 Set number of hash buckets for inode cache.
749 in2000= [HW,SCSI]
750 See header of drivers/scsi/in2000.c.
752 init= [KNL]
753 Format: <full_path>
754 Run specified binary instead of /sbin/init as init
755 process.
757 initcall_debug [KNL] Trace initcalls as they are executed. Useful
758 for working out where the kernel is dying during
759 startup.
761 initrd= [BOOT] Specify the location of the initial ramdisk
763 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
764 Format: <irq>
766 inttest= [IA64]
768 io7= [HW] IO7 for Marvel based alpha systems
769 See comment before marvel_specify_io7 in
770 arch/alpha/kernel/core_marvel.c.
772 ip= [IP_PNP]
773 See Documentation/nfsroot.txt.
775 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
776 See comment before ip2_setup() in
777 drivers/char/ip2/ip2base.c.
779 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
780 See header of drivers/scsi/ips.c.
782 ports= [IP_VS_FTP] IPVS ftp helper module
783 Default is 21.
784 Up to 8 (IP_VS_APP_MAX_PORTS) ports
785 may be specified.
786 Format: <port>,<port>....
788 irqfixup [HW]
789 When an interrupt is not handled search all handlers
790 for it. Intended to get systems with badly broken
791 firmware running.
793 irqpoll [HW]
794 When an interrupt is not handled search all handlers
795 for it. Also check all handlers each timer
796 interrupt. Intended to get systems with badly broken
797 firmware running.
799 isapnp= [ISAPNP]
800 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
802 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
803 Format:
804 <cpu number>,...,<cpu number>
805 or
806 <cpu number>-<cpu number> (must be a positive range in ascending order)
807 or a mixture
808 <cpu number>,...,<cpu number>-<cpu number>
809 This option can be used to specify one or more CPUs
810 to isolate from the general SMP balancing and scheduling
811 algorithms. The only way to move a process onto or off
812 an "isolated" CPU is via the CPU affinity syscalls.
813 <cpu number> begins at 0 and the maximum value is
814 "number of CPUs in system - 1".
816 This option is the preferred way to isolate CPUs. The
817 alternative -- manually setting the CPU mask of all
818 tasks in the system -- can cause problems and
819 suboptimal load balancer performance.
821 iucv= [HW,NET]
823 js= [HW,JOY] Analog joystick
824 See Documentation/input/joystick.txt.
826 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
827 specifies the amount of memory usable by the kernel
828 for non-movable allocations. The requested amount is
829 spread evenly throughout all nodes in the system. The
830 remaining memory in each node is used for Movable
831 pages. In the event, a node is too small to have both
832 kernelcore and Movable pages, kernelcore pages will
833 take priority and other nodes will have a larger number
834 of kernelcore pages. The Movable zone is used for the
835 allocation of pages that may be reclaimed or moved
836 by the page migration subsystem. This means that
837 HugeTLB pages may not be allocated from this zone.
838 Note that allocations like PTEs-from-HighMem still
839 use the HighMem zone if it exists, and the Normal
840 zone if it does not.
842 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
843 is similar to kernelcore except it specifies the
844 amount of memory used for migratable allocations.
845 If both kernelcore and movablecore is specified,
846 then kernelcore will be at *least* the specified
847 value but may be more. If movablecore on its own
848 is specified, the administrator must be careful
849 that the amount of memory usable for all allocations
850 is not too small.
852 keepinitrd [HW,ARM]
854 kstack=N [X86-32,X86-64] Print N words from the kernel stack
855 in oops dumps.
857 l2cr= [PPC]
859 lapic [X86-32,APIC] Enable the local APIC even if BIOS
860 disabled it.
862 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
863 C2 power state.
865 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
866 Format: addr:<io>,irq:<irq>
868 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
869 when set.
870 Format: <int>
872 load_ramdisk= [RAM] List of ramdisks to load from floppy
873 See Documentation/ramdisk.txt.
875 lockd.nlm_grace_period=P [NFS] Assign grace period.
876 Format: <integer>
878 lockd.nlm_tcpport=N [NFS] Assign TCP port.
879 Format: <integer>
881 lockd.nlm_timeout=T [NFS] Assign timeout value.
882 Format: <integer>
884 lockd.nlm_udpport=M [NFS] Assign UDP port.
885 Format: <integer>
887 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
888 Format: <irq>
890 loglevel= All Kernel Messages with a loglevel smaller than the
891 console loglevel will be printed to the console. It can
892 also be changed with klogd or other programs. The
893 loglevels are defined as follows:
895 0 (KERN_EMERG) system is unusable
896 1 (KERN_ALERT) action must be taken immediately
897 2 (KERN_CRIT) critical conditions
898 3 (KERN_ERR) error conditions
899 4 (KERN_WARNING) warning conditions
900 5 (KERN_NOTICE) normal but significant condition
901 6 (KERN_INFO) informational
902 7 (KERN_DEBUG) debug-level messages
904 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
905 Format: { n | nk | nM }
906 n must be a power of two. The default size
907 is set in the kernel config file.
909 lp=0 [LP] Specify parallel ports to use, e.g,
910 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
911 lp=reset first parallel port). 'lp=0' disables the
912 lp=auto printer driver. 'lp=reset' (which can be
913 specified in addition to the ports) causes
914 attached printers to be reset. Using
915 lp=port1,port2,... specifies the parallel ports
916 to associate lp devices with, starting with
917 lp0. A port specification may be 'none' to skip
918 that lp device, or a parport name such as
919 'parport0'. Specifying 'lp=auto' instead of a
920 port specification list means that device IDs
921 from each port should be examined, to see if
922 an IEEE 1284-compliant printer is attached; if
923 so, the driver will manage that printer.
924 See also header of drivers/char/lp.c.
926 lpj=n [KNL]
927 Sets loops_per_jiffy to given constant, thus avoiding
928 time-consuming boot-time autodetection (up to 250 ms per
929 CPU). 0 enables autodetection (default). To determine
930 the correct value for your kernel, boot with normal
931 autodetection and see what value is printed. Note that
932 on SMP systems the preset will be applied to all CPUs,
933 which is likely to cause problems if your CPUs need
934 significantly divergent settings. An incorrect value
935 will cause delays in the kernel to be wrong, leading to
936 unpredictable I/O errors and other breakage. Although
937 unlikely, in the extreme case this might damage your
938 hardware.
940 ltpc= [NET]
941 Format: <io>,<irq>,<dma>
943 mac5380= [HW,SCSI] Format:
944 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
946 mac53c9x= [HW,SCSI] Format:
947 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
949 machvec= [IA64] Force the use of a particular machine-vector
950 (machvec) in a generic kernel.
951 Example: machvec=hpzx1_swiotlb
953 max_loop= [LOOP] Maximum number of loopback devices that can
954 be mounted
955 Format: <1-256>
957 maxcpus= [SMP] Maximum number of processors that an SMP kernel
958 should make use of. maxcpus=n : n >= 0 limits the
959 kernel to using 'n' processors. n=0 is a special case,
960 it is equivalent to "nosmp", which also disables
961 the IO APIC.
963 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
964 equal to this physical address is ignored.
966 max_luns= [SCSI] Maximum number of LUNs to probe.
967 Should be between 1 and 2^32-1.
969 max_report_luns=
970 [SCSI] Maximum number of LUNs received.
971 Should be between 1 and 16384.
973 mca-pentium [BUGS=X86-32]
975 mcatest= [IA-64]
977 mce [X86-32] Machine Check Exception
979 md= [HW] RAID subsystems devices and level
980 See Documentation/md.txt.
982 mdacon= [MDA]
983 Format: <first>,<last>
984 Specifies range of consoles to be captured by the MDA.
986 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
987 Amount of memory to be used when the kernel is not able
988 to see the whole system memory or for test.
989 [X86-32] Use together with memmap= to avoid physical
990 address space collisions. Without memmap= PCI devices
991 could be placed at addresses belonging to unused RAM.
993 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
994 memory.
996 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
997 E820 memory map, as specified by the user.
998 Such memmap=exactmap lines can be constructed based on
999 BIOS output or other requirements. See the memmap=nn@ss
1000 option description.
1002 memmap=nn[KMG]@ss[KMG]
1003 [KNL] Force usage of a specific region of memory
1004 Region of memory to be used, from ss to ss+nn.
1006 memmap=nn[KMG]#ss[KMG]
1007 [KNL,ACPI] Mark specific memory as ACPI data.
1008 Region of memory to be used, from ss to ss+nn.
1010 memmap=nn[KMG]$ss[KMG]
1011 [KNL,ACPI] Mark specific memory as reserved.
1012 Region of memory to be used, from ss to ss+nn.
1014 meye.*= [HW] Set MotionEye Camera parameters
1015 See Documentation/video4linux/meye.txt.
1017 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1018 Multi-Function General Purpose Timers on AMD Geode
1019 platforms.
1021 mga= [HW,DRM]
1023 mousedev.tap_time=
1024 [MOUSE] Maximum time between finger touching and
1025 leaving touchpad surface for touch to be considered
1026 a tap and be reported as a left button click (for
1027 touchpads working in absolute mode only).
1028 Format: <msecs>
1029 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1030 reporting absolute coordinates, such as tablets
1031 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1032 reporting absolute coordinates, such as tablets
1034 mpu401= [HW,OSS]
1035 Format: <io>,<irq>
1037 MTD_Partition= [MTD]
1038 Format: <name>,<region-number>,<size>,<offset>
1040 MTD_Region= [MTD] Format:
1041 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1043 mtdparts= [MTD]
1044 See drivers/mtd/cmdlinepart.c.
1046 mtouchusb.raw_coordinates=
1047 [HW] Make the MicroTouch USB driver use raw coordinates
1048 ('y', default) or cooked coordinates ('n')
1050 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1052 NCR_D700= [HW,SCSI]
1053 See header of drivers/scsi/NCR_D700.c.
1055 ncr5380= [HW,SCSI]
1057 ncr53c400= [HW,SCSI]
1059 ncr53c400a= [HW,SCSI]
1061 ncr53c406a= [HW,SCSI]
1063 ncr53c8xx= [HW,SCSI]
1065 netdev= [NET] Network devices parameters
1066 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1067 Note that mem_start is often overloaded to mean
1068 something different and driver-specific.
1069 This usage is only documented in each driver source
1070 file if at all.
1072 nfsaddrs= [NFS]
1073 See Documentation/nfsroot.txt.
1075 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1076 See Documentation/nfsroot.txt.
1078 nfs.callback_tcpport=
1079 [NFS] set the TCP port on which the NFSv4 callback
1080 channel should listen.
1082 nfs.idmap_cache_timeout=
1083 [NFS] set the maximum lifetime for idmapper cache
1084 entries.
1086 nfs.enable_ino64=
1087 [NFS] enable 64-bit inode numbers.
1088 If zero, the NFS client will fake up a 32-bit inode
1089 number for the readdir() and stat() syscalls instead
1090 of returning the full 64-bit number.
1091 The default is to return 64-bit inode numbers.
1093 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1095 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1096 emulation library even if a 387 maths coprocessor
1097 is present.
1099 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1100 caches in the slab allocator. Saves per-node memory,
1101 but will impact performance.
1103 noalign [KNL,ARM]
1105 noapic [SMP,APIC] Tells the kernel to not make use of any
1106 IOAPICs that may be present in the system.
1108 noasync [HW,M68K] Disables async and sync negotiation for
1109 all devices.
1111 nobats [PPC] Do not use BATs for mapping kernel lowmem
1112 on "Classic" PPC cores.
1114 nocache [ARM]
1116 nodelayacct [KNL] Disable per-task delay accounting
1118 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1120 noexec [IA-64]
1122 noexec [X86-32,X86-64]
1123 noexec=on: enable non-executable mappings (default)
1124 noexec=off: disable nn-executable mappings
1126 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1127 register save and restore. The kernel will only save
1128 legacy floating-point registers on task switch.
1130 nohlt [BUGS=ARM]
1132 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1133 instruction doesn't work correctly and not to
1134 use it.
1136 nohalt [IA-64] Tells the kernel not to use the power saving
1137 function PAL_HALT_LIGHT when idle. This increases
1138 power-consumption. On the positive side, it reduces
1139 interrupt wake-up latency, which may improve performance
1140 in certain environments such as networked servers or
1141 real-time systems.
1143 nohz= [KNL] Boottime enable/disable dynamic ticks
1144 Valid arguments: on, off
1145 Default: on
1147 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1149 noirqdebug [X86-32] Disables the code which attempts to detect and
1150 disable unhandled interrupt sources.
1152 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1153 broken timer IRQ sources.
1155 noisapnp [ISAPNP] Disables ISA PnP code.
1157 noinitrd [RAM] Tells the kernel not to load any configured
1158 initial RAM disk.
1160 nointroute [IA-64]
1162 nojitter [IA64] Disables jitter checking for ITC timers.
1164 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1166 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1168 noltlbs [PPC] Do not use large page/tlb entries for kernel
1169 lowmem mapping on PPC40x.
1171 nomca [IA-64] Disable machine check abort handling
1173 nomce [X86-32] Machine Check Exception
1175 nomfgpt [X86-32] Disable Multi-Function General Purpose
1176 Timer usage (for AMD Geode machines).
1178 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1180 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1181 with UP alternatives
1183 noresidual [PPC] Don't use residual data on PReP machines.
1185 noresume [SWSUSP] Disables resume and restores original swap
1186 space.
1188 no-scroll [VGA] Disables scrollback.
1189 This is required for the Braillex ib80-piezo Braille
1190 reader made by F.H. Papenmeier (Germany).
1192 nosbagart [IA-64]
1194 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1196 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1197 and disable the IO APIC. legacy for "maxcpus=0".
1199 nosoftlockup [KNL] Disable the soft-lockup detector.
1201 nosync [HW,M68K] Disables sync negotiation for all devices.
1203 notsc [BUGS=X86-32] Disable Time Stamp Counter
1205 nousb [USB] Disable the USB subsystem
1207 nowb [ARM]
1209 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1210 one of ['zone', 'node', 'default'] can be specified
1211 This can be set from sysctl after boot.
1212 See Documentation/sysctl/vm.txt for details.
1214 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1216 opl3= [HW,OSS]
1217 Format: <io>
1219 oprofile.timer= [HW]
1220 Use timer interrupt instead of performance counters
1222 osst= [HW,SCSI] SCSI Tape Driver
1223 Format: <buffer_size>,<write_threshold>
1224 See also Documentation/scsi/st.txt.
1226 panic= [KNL] Kernel behaviour on panic
1227 Format: <timeout>
1229 parkbd.port= [HW] Parallel port number the keyboard adapter is
1230 connected to, default is 0.
1231 Format: <parport#>
1232 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1233 0 for XT, 1 for AT (default is AT).
1234 Format: <mode>
1236 parport= [HW,PPT] Specify parallel ports. 0 disables.
1237 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1238 Use 'auto' to force the driver to use any
1239 IRQ/DMA settings detected (the default is to
1240 ignore detected IRQ/DMA settings because of
1241 possible conflicts). You can specify the base
1242 address, IRQ, and DMA settings; IRQ and DMA
1243 should be numbers, or 'auto' (for using detected
1244 settings on that particular port), or 'nofifo'
1245 (to avoid using a FIFO even if it is detected).
1246 Parallel ports are assigned in the order they
1247 are specified on the command line, starting
1248 with parport0.
1250 parport_init_mode= [HW,PPT]
1251 Configure VIA parallel port to operate in
1252 a specific mode. This is necessary on Pegasos
1253 computer where firmware has no options for setting
1254 up parallel port mode and sets it to spp.
1255 Currently this function knows 686a and 8231 chips.
1256 Format: [spp|ps2|epp|ecp|ecpepp]
1258 pas2= [HW,OSS] Format:
1259 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1261 pas16= [HW,SCSI]
1262 See header of drivers/scsi/pas16.c.
1264 pause_on_oops=
1265 Halt all CPUs after the first oops has been printed for
1266 the specified number of seconds. This is to be used if
1267 your oopses keep scrolling off the screen.
1269 pcbit= [HW,ISDN]
1271 pcd. [PARIDE]
1272 See header of drivers/block/paride/pcd.c.
1273 See also Documentation/paride.txt.
1275 pci=option[,option...] [PCI] various PCI subsystem options:
1276 off [X86-32] don't probe for the PCI bus
1277 bios [X86-32] force use of PCI BIOS, don't access
1278 the hardware directly. Use this if your machine
1279 has a non-standard PCI host bridge.
1280 nobios [X86-32] disallow use of PCI BIOS, only direct
1281 hardware access methods are allowed. Use this
1282 if you experience crashes upon bootup and you
1283 suspect they are caused by the BIOS.
1284 conf1 [X86-32] Force use of PCI Configuration
1285 Mechanism 1.
1286 conf2 [X86-32] Force use of PCI Configuration
1287 Mechanism 2.
1288 noaer [PCIE] If the PCIEAER kernel config parameter is
1289 enabled, this kernel boot option can be used to
1290 disable the use of PCIE advanced error reporting.
1291 nodomains [PCI] Disable support for multiple PCI
1292 root domains (aka PCI segments, in ACPI-speak).
1293 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1294 Configuration
1295 nomsi [MSI] If the PCI_MSI kernel config parameter is
1296 enabled, this kernel boot option can be used to
1297 disable the use of MSI interrupts system-wide.
1298 nosort [X86-32] Don't sort PCI devices according to
1299 order given by the PCI BIOS. This sorting is
1300 done to get a device order compatible with
1301 older kernels.
1302 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1303 routing table. These calls are known to be buggy
1304 on several machines and they hang the machine
1305 when used, but on other computers it's the only
1306 way to get the interrupt routing table. Try
1307 this option if the kernel is unable to allocate
1308 IRQs or discover secondary PCI buses on your
1309 motherboard.
1310 rom [X86-32] Assign address space to expansion ROMs.
1311 Use with caution as certain devices share
1312 address decoders between ROMs and other
1313 resources.
1314 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1315 assigned automatically to PCI devices. You can
1316 make the kernel exclude IRQs of your ISA cards
1317 this way.
1318 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1319 of the PIRQ table (normally generated
1320 by the BIOS) if it is outside the
1321 F0000h-100000h range.
1322 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1323 useful if the kernel is unable to find your
1324 secondary buses and you want to tell it
1325 explicitly which ones they are.
1326 assign-busses [X86-32] Always assign all PCI bus
1327 numbers ourselves, overriding
1328 whatever the firmware may have done.
1329 usepirqmask [X86-32] Honor the possible IRQ mask stored
1330 in the BIOS $PIR table. This is needed on
1331 some systems with broken BIOSes, notably
1332 some HP Pavilion N5400 and Omnibook XE3
1333 notebooks. This will have no effect if ACPI
1334 IRQ routing is enabled.
1335 noacpi [X86-32] Do not use ACPI for IRQ routing
1336 or for PCI scanning.
1337 use_crs [X86-32] Use _CRS for PCI resource
1338 allocation.
1339 routeirq Do IRQ routing for all PCI devices.
1340 This is normally done in pci_enable_device(),
1341 so this option is a temporary workaround
1342 for broken drivers that don't call it.
1343 firmware [ARM] Do not re-enumerate the bus but instead
1344 just use the configuration from the
1345 bootloader. This is currently used on
1346 IXP2000 systems where the bus has to be
1347 configured a certain way for adjunct CPUs.
1348 noearly [X86] Don't do any early type 1 scanning.
1349 This might help on some broken boards which
1350 machine check when some devices' config space
1351 is read. But various workarounds are disabled
1352 and some IOMMU drivers will not work.
1353 bfsort Sort PCI devices into breadth-first order.
1354 This sorting is done to get a device
1355 order compatible with older (<= 2.4) kernels.
1356 nobfsort Don't sort PCI devices into breadth-first order.
1357 cbiosize=nn[KMG] The fixed amount of bus space which is
1358 reserved for the CardBus bridge's IO window.
1359 The default value is 256 bytes.
1360 cbmemsize=nn[KMG] The fixed amount of bus space which is
1361 reserved for the CardBus bridge's memory
1362 window. The default value is 64 megabytes.
1364 pcmv= [HW,PCMCIA] BadgePAD 4
1366 pd. [PARIDE]
1367 See Documentation/paride.txt.
1369 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1370 boot time.
1371 Format: { 0 | 1 }
1372 See arch/parisc/kernel/pdc_chassis.c
1374 pf. [PARIDE]
1375 See Documentation/paride.txt.
1377 pg. [PARIDE]
1378 See Documentation/paride.txt.
1380 pirq= [SMP,APIC] Manual mp-table setup
1381 See Documentation/i386/IO-APIC.txt.
1383 plip= [PPT,NET] Parallel port network link
1384 Format: { parport<nr> | timid | 0 }
1385 See also Documentation/parport.txt.
1387 pnpacpi= [ACPI]
1388 { off }
1390 pnpbios= [ISAPNP]
1391 { on | off | curr | res | no-curr | no-res }
1393 pnp_reserve_irq=
1394 [ISAPNP] Exclude IRQs for the autoconfiguration
1396 pnp_reserve_dma=
1397 [ISAPNP] Exclude DMAs for the autoconfiguration
1399 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1400 Ranges are in pairs (I/O port base and size).
1402 pnp_reserve_mem=
1403 [ISAPNP] Exclude memory regions for the
1404 autoconfiguration.
1405 Ranges are in pairs (memory base and size).
1407 print-fatal-signals=
1408 [KNL] debug: print fatal signals
1409 print-fatal-signals=1: print segfault info to
1410 the kernel console.
1411 default: off.
1413 printk.time= Show timing data prefixed to each printk message line
1414 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1416 profile= [KNL] Enable kernel profiling via /proc/profile
1417 Format: [schedule,]<number>
1418 Param: "schedule" - profile schedule points.
1419 Param: <number> - step/bucket size as a power of 2 for
1420 statistical time based profiling.
1421 Param: "sleep" - profile D-state sleeping (millisecs)
1423 processor.max_cstate= [HW,ACPI]
1424 Limit processor to maximum C-state
1425 max_cstate=9 overrides any DMI blacklist limit.
1427 processor.nocst [HW,ACPI]
1428 Ignore the _CST method to determine C-states,
1429 instead using the legacy FADT method
1431 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1432 before loading.
1433 See Documentation/ramdisk.txt.
1435 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1436 probe for; one of (bare|imps|exps|lifebook|any).
1437 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1438 per second.
1439 psmouse.resetafter= [HW,MOUSE]
1440 Try to reset the device after so many bad packets
1441 (0 = never).
1442 psmouse.resolution=
1443 [HW,MOUSE] Set desired mouse resolution, in dpi.
1444 psmouse.smartscroll=
1445 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1446 0 = disabled, 1 = enabled (default).
1448 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1449 Format:
1450 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1452 pt. [PARIDE]
1453 See Documentation/paride.txt.
1455 pty.legacy_count=
1456 [KNL] Number of legacy pty's. Overwrites compiled-in
1457 default number.
1459 quiet [KNL] Disable most log messages
1461 r128= [HW,DRM]
1463 raid= [HW,RAID]
1464 See Documentation/md.txt.
1466 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1467 See Documentation/ramdisk.txt.
1469 ramdisk_blocksize= [RAM]
1470 See Documentation/ramdisk.txt.
1472 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1473 New name for the ramdisk parameter.
1474 See Documentation/ramdisk.txt.
1476 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1477 RCU callbacks to process in one batch.
1479 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1480 RCU callbacks over which batch limiting is disabled.
1482 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1483 RCU callbacks below which batch limiting is re-enabled.
1485 rdinit= [KNL]
1486 Format: <full_path>
1487 Run specified binary instead of /init from the ramdisk,
1488 used for early userspace startup. See initrd.
1490 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1491 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1492 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1494 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1496 reservetop= [X86-32]
1497 Format: nn[KMG]
1498 Reserves a hole at the top of the kernel virtual
1499 address space.
1501 reset_devices [KNL] Force drivers to reset the underlying device
1502 during initialization.
1504 resume= [SWSUSP]
1505 Specify the partition device for software suspend
1507 resume_offset= [SWSUSP]
1508 Specify the offset from the beginning of the partition
1509 given by "resume=" at which the swap header is located,
1510 in <PAGE_SIZE> units (needed only for swap files).
1511 See Documentation/power/swsusp-and-swap-files.txt
1513 retain_initrd [RAM] Keep initrd memory after extraction
1515 rhash_entries= [KNL,NET]
1516 Set number of hash buckets for route cache
1518 riscom8= [HW,SERIAL]
1519 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1521 ro [KNL] Mount root device read-only on boot
1523 root= [KNL] Root filesystem
1525 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1526 mount the root filesystem
1528 rootflags= [KNL] Set root filesystem mount option string
1530 rootfstype= [KNL] Set root filesystem type
1532 rootwait [KNL] Wait (indefinitely) for root device to show up.
1533 Useful for devices that are detected asynchronously
1534 (e.g. USB and MMC devices).
1536 rw [KNL] Mount root device read-write on boot
1538 S [KNL] Run init in single mode
1540 sa1100ir [NET]
1541 See drivers/net/irda/sa1100_ir.c.
1543 sb= [HW,OSS]
1544 Format: <io>,<irq>,<dma>,<dma2>
1546 sbni= [NET] Granch SBNI12 leased line adapter
1548 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1549 Format: <io>[,<timeout>[,<isapnp>]]
1551 scsi_debug_*= [SCSI]
1552 See drivers/scsi/scsi_debug.c.
1554 scsi_default_dev_flags=
1555 [SCSI] SCSI default device flags
1556 Format: <integer>
1558 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1559 Format: <vendor>:<model>:<flags>
1560 (flags are integer value)
1562 scsi_logging= [SCSI]
1564 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1565 discovered. async scans them in kernel threads,
1566 allowing boot to proceed. none ignores them, expecting
1567 user space to do the scan.
1569 selinux [SELINUX] Disable or enable SELinux at boot time.
1570 Format: { "0" | "1" }
1571 See security/selinux/Kconfig help text.
1572 0 -- disable.
1573 1 -- enable.
1574 Default value is set via kernel config option.
1575 If enabled at boot time, /selinux/disable can be used
1576 later to disable prior to initial policy load.
1578 selinux_compat_net =
1579 [SELINUX] Set initial selinux_compat_net flag value.
1580 Format: { "0" | "1" }
1581 0 -- use new secmark-based packet controls
1582 1 -- use legacy packet controls
1583 Default value is 0 (preferred).
1584 Value can be changed at runtime via
1585 /selinux/compat_net.
1587 serialnumber [BUGS=X86-32]
1589 sg_def_reserved_size= [SCSI]
1591 shapers= [NET]
1592 Maximal number of shapers.
1594 sim710= [SCSI,HW]
1595 See header of drivers/scsi/sim710.c.
1597 simeth= [IA-64]
1598 simscsi=
1600 slram= [HW,MTD]
1602 slub_debug[=options[,slabs]] [MM, SLUB]
1603 Enabling slub_debug allows one to determine the
1604 culprit if slab objects become corrupted. Enabling
1605 slub_debug can create guard zones around objects and
1606 may poison objects when not in use. Also tracks the
1607 last alloc / free. For more information see
1608 Documentation/vm/slub.txt.
1610 slub_max_order= [MM, SLUB]
1611 Determines the maximum allowed order for slabs.
1612 A high setting may cause OOMs due to memory
1613 fragmentation. For more information see
1614 Documentation/vm/slub.txt.
1616 slub_min_objects= [MM, SLUB]
1617 The minimum number of objects per slab. SLUB will
1618 increase the slab order up to slub_max_order to
1619 generate a sufficiently large slab able to contain
1620 the number of objects indicated. The higher the number
1621 of objects the smaller the overhead of tracking slabs
1622 and the less frequently locks need to be acquired.
1623 For more information see Documentation/vm/slub.txt.
1625 slub_min_order= [MM, SLUB]
1626 Determines the mininum page order for slabs. Must be
1627 lower than slub_max_order.
1628 For more information see Documentation/vm/slub.txt.
1630 slub_nomerge [MM, SLUB]
1631 Disable merging of slabs with similar size. May be
1632 necessary if there is some reason to distinguish
1633 allocs to different slabs. Debug options disable
1634 merging on their own.
1635 For more information see Documentation/vm/slub.txt.
1637 smart2= [HW]
1638 Format: <io1>[,<io2>[,...,<io8>]]
1640 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1641 attempt to substitute SMP alternatives once at boot.
1643 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1644 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1645 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1646 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1647 smsc-ircc2.ircc_irq= [HW] IRQ line
1648 smsc-ircc2.ircc_dma= [HW] DMA channel
1649 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1650 0: Toshiba Satellite 1800 (GP data pin select)
1651 1: Fast pin select (default)
1652 2: ATC IRMode
1654 snd-ad1816a= [HW,ALSA]
1656 snd-ad1848= [HW,ALSA]
1658 snd-ali5451= [HW,ALSA]
1660 snd-als100= [HW,ALSA]
1662 snd-als4000= [HW,ALSA]
1664 snd-azt2320= [HW,ALSA]
1666 snd-cmi8330= [HW,ALSA]
1668 snd-cmipci= [HW,ALSA]
1670 snd-cs4231= [HW,ALSA]
1672 snd-cs4232= [HW,ALSA]
1674 snd-cs4236= [HW,ALSA]
1676 snd-cs4281= [HW,ALSA]
1678 snd-cs46xx= [HW,ALSA]
1680 snd-dt019x= [HW,ALSA]
1682 snd-dummy= [HW,ALSA]
1684 snd-emu10k1= [HW,ALSA]
1686 snd-ens1370= [HW,ALSA]
1688 snd-ens1371= [HW,ALSA]
1690 snd-es968= [HW,ALSA]
1692 snd-es1688= [HW,ALSA]
1694 snd-es18xx= [HW,ALSA]
1696 snd-es1938= [HW,ALSA]
1698 snd-es1968= [HW,ALSA]
1700 snd-fm801= [HW,ALSA]
1702 snd-gusclassic= [HW,ALSA]
1704 snd-gusextreme= [HW,ALSA]
1706 snd-gusmax= [HW,ALSA]
1708 snd-hdsp= [HW,ALSA]
1710 snd-ice1712= [HW,ALSA]
1712 snd-intel8x0= [HW,ALSA]
1714 snd-interwave= [HW,ALSA]
1716 snd-interwave-stb=
1717 [HW,ALSA]
1719 snd-korg1212= [HW,ALSA]
1721 snd-maestro3= [HW,ALSA]
1723 snd-mpu401= [HW,ALSA]
1725 snd-mtpav= [HW,ALSA]
1727 snd-nm256= [HW,ALSA]
1729 snd-opl3sa2= [HW,ALSA]
1731 snd-opti92x-ad1848=
1732 [HW,ALSA]
1734 snd-opti92x-cs4231=
1735 [HW,ALSA]
1737 snd-opti93x= [HW,ALSA]
1739 snd-pmac= [HW,ALSA]
1741 snd-rme32= [HW,ALSA]
1743 snd-rme96= [HW,ALSA]
1745 snd-rme9652= [HW,ALSA]
1747 snd-sb8= [HW,ALSA]
1749 snd-sb16= [HW,ALSA]
1751 snd-sbawe= [HW,ALSA]
1753 snd-serial= [HW,ALSA]
1755 snd-sgalaxy= [HW,ALSA]
1757 snd-sonicvibes= [HW,ALSA]
1759 snd-sun-amd7930=
1760 [HW,ALSA]
1762 snd-sun-cs4231= [HW,ALSA]
1764 snd-trident= [HW,ALSA]
1766 snd-usb-audio= [HW,ALSA,USB]
1768 snd-via82xx= [HW,ALSA]
1770 snd-virmidi= [HW,ALSA]
1772 snd-wavefront= [HW,ALSA]
1774 snd-ymfpci= [HW,ALSA]
1776 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1777 See Documentation/sonypi.txt
1779 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1780 See Documentation/specialix.txt.
1782 spia_io_base= [HW,MTD]
1783 spia_fio_base=
1784 spia_pedr=
1785 spia_peddr=
1787 sscape= [HW,OSS]
1788 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1790 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1791 See Documentation/scsi/st.txt.
1793 st0x= [HW,SCSI]
1794 See header of drivers/scsi/seagate.c.
1796 sti= [PARISC,HW]
1797 Format: <num>
1798 Set the STI (builtin display/keyboard on the HP-PARISC
1799 machines) console (graphic card) which should be used
1800 as the initial boot-console.
1801 See also comment in drivers/video/console/sticore.c.
1803 sti_font= [HW]
1804 See comment in drivers/video/console/sticore.c.
1806 stifb= [HW]
1807 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1809 sunrpc.pool_mode=
1810 [NFS]
1811 Control how the NFS server code allocates CPUs to
1812 service thread pools. Depending on how many NICs
1813 you have and where their interrupts are bound, this
1814 option will affect which CPUs will do NFS serving.
1815 Note: this parameter cannot be changed while the
1816 NFS server is running.
1818 auto the server chooses an appropriate mode
1819 automatically using heuristics
1820 global a single global pool contains all CPUs
1821 percpu one pool for each CPU
1822 pernode one pool for each NUMA node (equivalent
1823 to global on non-NUMA machines)
1825 swiotlb= [IA-64] Number of I/O TLB slabs
1827 switches= [HW,M68k]
1829 sym53c416= [HW,SCSI]
1830 See header of drivers/scsi/sym53c416.c.
1832 sysrq_always_enabled
1833 [KNL]
1834 Ignore sysrq setting - this boot parameter will
1835 neutralize any effect of /proc/sys/kernel/sysrq.
1836 Useful for debugging.
1838 t128= [HW,SCSI]
1839 See header of drivers/scsi/t128.c.
1841 tdfx= [HW,DRM]
1843 thash_entries= [KNL,NET]
1844 Set number of hash buckets for TCP connection
1846 thermal.act= [HW,ACPI]
1847 -1: disable all active trip points in all thermal zones
1848 <degrees C>: override all lowest active trip points
1850 thermal.crt= [HW,ACPI]
1851 -1: disable all critical trip points in all thermal zones
1852 <degrees C>: lower all critical trip points
1854 thermal.nocrt= [HW,ACPI]
1855 Set to disable actions on ACPI thermal zone
1856 critical and hot trip points.
1858 thermal.off= [HW,ACPI]
1859 1: disable ACPI thermal control
1861 thermal.psv= [HW,ACPI]
1862 -1: disable all passive trip points
1863 <degrees C>: override all passive trip points to this value
1865 thermal.tzp= [HW,ACPI]
1866 Specify global default ACPI thermal zone polling rate
1867 <deci-seconds>: poll all this frequency
1868 0: no polling (default)
1870 time Show timing data prefixed to each printk message line
1871 [deprecated, see 'printk.time']
1873 tipar.timeout= [HW,PPT]
1874 Set communications timeout in tenths of a second
1875 (default 15).
1877 tipar.delay= [HW,PPT]
1878 Set inter-bit delay in microseconds (default 10).
1880 tmc8xx= [HW,SCSI]
1881 See header of drivers/scsi/seagate.c.
1883 tmscsim= [HW,SCSI]
1884 See comment before function dc390_setup() in
1885 drivers/scsi/tmscsim.c.
1887 tp720= [HW,PS2]
1889 trix= [HW,OSS] MediaTrix AudioTrix Pro
1890 Format:
1891 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1893 turbografx.map[2|3]= [HW,JOY]
1894 TurboGraFX parallel port interface
1895 Format:
1896 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1897 See also Documentation/input/joystick-parport.txt
1899 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1900 See header of drivers/scsi/u14-34f.c.
1902 uart401= [HW,OSS]
1903 Format: <io>,<irq>
1905 uart6850= [HW,OSS]
1906 Format: <io>,<irq>
1908 uhci-hcd.ignore_oc=
1909 [USB] Ignore overcurrent events (default N).
1910 Some badly-designed motherboards generate lots of
1911 bogus events, for ports that aren't wired to
1912 anything. Set this parameter to avoid log spamming.
1913 Note that genuine overcurrent events won't be
1914 reported either.
1916 usbcore.autosuspend=
1917 [USB] The autosuspend time delay (in seconds) used
1918 for newly-detected USB devices (default 2). This
1919 is the time required before an idle device will be
1920 autosuspended. Devices for which the delay is set
1921 to a negative value won't be autosuspended at all.
1923 usbhid.mousepoll=
1924 [USBHID] The interval which mice are to be polled at.
1926 vdso= [X86-32,SH,x86-64]
1927 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1928 vdso=1: enable VDSO (default)
1929 vdso=0: disable VDSO mapping
1931 vector= [IA-64,SMP]
1932 vector=percpu: enable percpu vector domain
1934 video= [FB] Frame buffer configuration
1935 See Documentation/fb/modedb.txt.
1937 vga= [BOOT,X86-32] Select a particular video mode
1938 See Documentation/i386/boot.txt and
1939 Documentation/svga.txt.
1940 Use vga=ask for menu.
1941 This is actually a boot loader parameter; the value is
1942 passed to the kernel using a special protocol.
1944 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1945 size of <nn>. This can be used to increase the
1946 minimum size (128MB on x86). It can also be used to
1947 decrease the size and leave more room for directly
1948 mapped kernel RAM.
1950 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1951 Format: <command>
1953 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1954 Format: <command>
1956 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1957 Format: <command>
1959 waveartist= [HW,OSS]
1960 Format: <io>,<irq>,<dma>,<dma2>
1962 wd33c93= [HW,SCSI]
1963 See header of drivers/scsi/wd33c93.c.
1965 wd7000= [HW,SCSI]
1966 See header of drivers/scsi/wd7000.c.
1968 wdt= [WDT] Watchdog
1969 See Documentation/watchdog/wdt.txt.
1971 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1972 xd_geo= See header of drivers/block/xd.c.
1974 xirc2ps_cs= [NET,PCMCIA]
1975 Format:
1976 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1978 norandmaps Don't use address space randomization
1979 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1981 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1982 This is useful to get more information why
1983 you got a "dwarf2 unwinder stuck"
1985 ______________________________________________________________________
1987 TODO:
1989 Add documentation for ALSA options.
1990 Add more DRM drivers.