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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 ALSA ALSA sound support is enabled.
34 APIC APIC support is enabled.
35 APM Advanced Power Management support is enabled.
36 AX25 Appropriate AX.25 support is enabled.
37 DRM Direct Rendering Management support is enabled.
38 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
39 EFI EFI Partitioning (GPT) is enabled
40 EIDE EIDE/ATAPI support is enabled.
41 FB The frame buffer device is enabled.
42 HW Appropriate hardware is enabled.
43 IA-32 IA-32 aka i386 architecture is enabled.
44 IA-64 IA-64 architecture is enabled.
45 IOSCHED More than one I/O scheduler is enabled.
46 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
47 ISAPNP ISA PnP code is enabled.
48 ISDN Appropriate ISDN support is enabled.
49 JOY Appropriate joystick support is enabled.
50 LIBATA Libata driver is enabled
51 LP Printer support is enabled.
52 LOOP Loopback device support is enabled.
53 M68k M68k architecture is enabled.
54 These options have more detailed description inside of
55 Documentation/m68k/kernel-options.txt.
56 MCA MCA bus support is enabled.
57 MDA MDA console support is enabled.
58 MOUSE Appropriate mouse support is enabled.
59 MSI Message Signaled Interrupts (PCI).
60 MTD MTD support is enabled.
61 NET Appropriate network support is enabled.
62 NUMA NUMA support is enabled.
63 GENERIC_TIME The generic timeofday code is enabled.
64 NFS Appropriate NFS support is enabled.
65 OSS OSS sound support is enabled.
66 PV_OPS A paravirtualized kernel
67 PARIDE The ParIDE subsystem is enabled.
68 PARISC The PA-RISC architecture is enabled.
69 PCI PCI bus support is enabled.
70 PCMCIA The PCMCIA subsystem is enabled.
71 PNP Plug & Play support is enabled.
72 PPC PowerPC architecture is enabled.
73 PPT Parallel port support is enabled.
74 PS2 Appropriate PS/2 support is enabled.
75 RAM RAM disk support is enabled.
76 S390 S390 architecture is enabled.
77 SCSI Appropriate SCSI support is enabled.
78 A lot of drivers has their options described inside of
79 Documentation/scsi/.
80 SELINUX SELinux support is enabled.
81 SERIAL Serial support is enabled.
82 SH SuperH architecture is enabled.
83 SMP The kernel is an SMP kernel.
84 SPARC Sparc architecture is enabled.
85 SWSUSP Software suspend is enabled.
86 TS Appropriate touchscreen support is enabled.
87 USB USB support is enabled.
88 USBHID USB Human Interface Device support is enabled.
89 V4L Video For Linux support is enabled.
90 VGA The VGA console has been enabled.
91 VT Virtual terminal support is enabled.
92 WDT Watchdog support is enabled.
93 XT IBM PC/XT MFM hard disk support is enabled.
94 X86-64 X86-64 architecture is enabled.
95 More X86-64 boot options can be found in
96 Documentation/x86_64/boot-options.txt .
98 In addition, the following text indicates that the option:
100 BUGS= Relates to possible processor bugs on the said processor.
101 KNL Is a kernel start-up parameter.
102 BOOT Is a boot loader parameter.
104 Parameters denoted with BOOT are actually interpreted by the boot
105 loader, and have no meaning to the kernel directly.
106 Do not modify the syntax of boot loader parameters without extreme
107 need or coordination with <Documentation/i386/boot.txt>.
109 There are also arch-specific kernel-parameters not documented here.
110 See for example <Documentation/x86_64/boot-options.txt>.
112 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
113 a trailing = on the name of any parameter states that that parameter will
114 be entered as an environment variable, whereas its absence indicates that
115 it will appear as a kernel argument readable via /proc/cmdline by programs
116 running once the system is up.
118 The number of kernel parameters is not limited, but the length of the
119 complete command line (parameters including spaces etc.) is limited to
120 a fixed number of characters. This limit depends on the architecture
121 and is between 256 and 4096 characters. It is defined in the file
122 ./include/asm/setup.h as COMMAND_LINE_SIZE.
125 53c7xx= [HW,SCSI] Amiga SCSI controllers
126 See header of drivers/scsi/53c7xx.c.
127 See also Documentation/scsi/ncr53c7xx.txt.
129 acpi= [HW,ACPI,X86-64,i386]
130 Advanced Configuration and Power Interface
131 Format: { force | off | ht | strict | noirq }
132 force -- enable ACPI if default was off
133 off -- disable ACPI if default was on
134 noirq -- do not use ACPI for IRQ routing
135 ht -- run only enough ACPI to enable Hyper Threading
136 strict -- Be less tolerant of platforms that are not
137 strictly ACPI specification compliant.
139 See also Documentation/pm.txt, pci=noacpi
141 acpi_apic_instance= [ACPI, IOAPIC]
142 Format: <int>
143 2: use 2nd APIC table, if available
144 1,0: use 1st APIC table
145 default: 0
147 acpi_sleep= [HW,ACPI] Sleep options
148 Format: { s3_bios, s3_mode }
149 See Documentation/power/video.txt
151 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
152 Format: { level | edge | high | low }
154 acpi_irq_balance [HW,ACPI]
155 ACPI will balance active IRQs
156 default in APIC mode
158 acpi_irq_nobalance [HW,ACPI]
159 ACPI will not move active IRQs (default)
160 default in PIC mode
162 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
163 use by PCI
164 Format: <irq>,<irq>...
166 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
167 Format: <irq>,<irq>...
169 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
170 Format: To spoof as Windows 98: ="Microsoft Windows"
172 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
173 acpi_osi="string1" # add string1 -- only one string
174 acpi_osi="!string2" # remove built-in string2
175 acpi_osi= # disable all strings
177 acpi_serialize [HW,ACPI] force serialization of AML methods
179 acpi_skip_timer_override [HW,ACPI]
180 Recognize and ignore IRQ0/pin2 Interrupt Override.
181 For broken nForce2 BIOS resulting in XT-PIC timer.
182 acpi_use_timer_override [HW,ACPI}
183 Use timer override. For some broken Nvidia NF5 boards
184 that require a timer override, but don't have
185 HPET
187 acpi.debug_layer= [HW,ACPI]
188 Format: <int>
189 Each bit of the <int> indicates an ACPI debug layer,
190 1: enable, 0: disable. It is useful for boot time
191 debugging. After system has booted up, it can be set
192 via /sys/module/acpi/parameters/debug_layer.
193 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
194 Available bits (add the numbers together) to enable debug output
195 for specific parts of the ACPI subsystem:
196 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
197 0x10 namespace 0x20 parser 0x40 dispatcher
198 0x80 executer 0x100 resources 0x200 acpica debugger
199 0x400 os services 0x800 acpica disassembler.
200 The number can be in decimal or prefixed with 0x in hex.
201 Warning: Many of these options can produce a lot of
202 output and make your system unusable. Be very careful.
204 acpi.debug_level= [HW,ACPI]
205 Format: <int>
206 Each bit of the <int> indicates an ACPI debug level,
207 1: enable, 0: disable. It is useful for boot time
208 debugging. After system has booted up, it can be set
209 via /sys/module/acpi/parameters/debug_level.
210 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
211 Available bits (add the numbers together) to enable different
212 debug output levels of the ACPI subsystem:
213 0x01 error 0x02 warn 0x04 init 0x08 debug object
214 0x10 info 0x20 init names 0x40 parse 0x80 load
215 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
216 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
217 0x10000 resources 0x20000 user requests 0x40000 package.
218 The number can be in decimal or prefixed with 0x in hex.
219 Warning: Many of these options can produce a lot of
220 output and make your system unusable. Be very careful.
223 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
225 acpi_pm_good [IA-32,X86-64]
226 Override the pmtimer bug detection: force the kernel
227 to assume that this machine's pmtimer latches its value
228 and always returns good values.
230 enable_timer_pin_1 [i386,x86-64]
231 Enable PIN 1 of APIC timer
232 Can be useful to work around chipset bugs
233 (in particular on some ATI chipsets).
234 The kernel tries to set a reasonable default.
236 disable_timer_pin_1 [i386,x86-64]
237 Disable PIN 1 of APIC timer
238 Can be useful to work around chipset bugs.
240 ad1848= [HW,OSS]
241 Format: <io>,<irq>,<dma>,<dma2>,<type>
243 advansys= [HW,SCSI]
244 See header of drivers/scsi/advansys.c.
246 advwdt= [HW,WDT] Advantech WDT
247 Format: <iostart>,<iostop>
249 aedsp16= [HW,OSS] Audio Excel DSP 16
250 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
251 See also header of sound/oss/aedsp16.c.
253 aha152x= [HW,SCSI]
254 See Documentation/scsi/aha152x.txt.
256 aha1542= [HW,SCSI]
257 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
259 aic7xxx= [HW,SCSI]
260 See Documentation/scsi/aic7xxx.txt.
262 aic79xx= [HW,SCSI]
263 See Documentation/scsi/aic79xx.txt.
265 amijoy.map= [HW,JOY] Amiga joystick support
266 Map of devices attached to JOY0DAT and JOY1DAT
267 Format: <a>,<b>
268 See also Documentation/kernel/input/joystick.txt
270 analog.map= [HW,JOY] Analog joystick and gamepad support
271 Specifies type or capabilities of an analog joystick
272 connected to one of 16 gameports
273 Format: <type1>,<type2>,..<type16>
275 apc= [HW,SPARC]
276 Power management functions (SPARCstation-4/5 + deriv.)
277 Format: noidle
278 Disable APC CPU standby support. SPARCstation-Fox does
279 not play well with APC CPU idle - disable it if you have
280 APC and your system crashes randomly.
282 apic= [APIC,i386] Change the output verbosity whilst booting
283 Format: { quiet (default) | verbose | debug }
284 Change the amount of debugging information output
285 when initialising the APIC and IO-APIC components.
287 apm= [APM] Advanced Power Management
288 See header of arch/i386/kernel/apm.c.
290 applicom= [HW]
291 Format: <mem>,<irq>
293 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
294 Format: <io>,<irq>,<nodeID>
296 ataflop= [HW,M68k]
298 atarimouse= [HW,MOUSE] Atari Mouse
300 atascsi= [HW,SCSI] Atari SCSI
302 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
303 EzKey and similar keyboards
305 atkbd.reset= [HW] Reset keyboard during initialization
307 atkbd.set= [HW] Select keyboard code set
308 Format: <int> (2 = AT (default), 3 = PS/2)
310 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
311 keyboards
313 atkbd.softraw= [HW] Choose between synthetic and real raw mode
314 Format: <bool> (0 = real, 1 = synthetic (default))
316 atkbd.softrepeat= [HW]
317 Use software keyboard repeat
319 autotest [IA64]
321 baycom_epp= [HW,AX25]
322 Format: <io>,<mode>
324 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
325 Format: <io>,<mode>
326 See header of drivers/net/hamradio/baycom_par.c.
328 baycom_ser_fdx= [HW,AX25]
329 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
330 Format: <io>,<irq>,<mode>[,<baud>]
331 See header of drivers/net/hamradio/baycom_ser_fdx.c.
333 baycom_ser_hdx= [HW,AX25]
334 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
335 Format: <io>,<irq>,<mode>
336 See header of drivers/net/hamradio/baycom_ser_hdx.c.
338 blkmtd_device= [HW,MTD]
339 blkmtd_erasesz=
340 blkmtd_ro=
341 blkmtd_bs=
342 blkmtd_count=
344 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
345 bttv.radio= Most important insmod options are available as
346 kernel args too.
347 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
348 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
350 BusLogic= [HW,SCSI]
351 See drivers/scsi/BusLogic.c, comment before function
352 BusLogic_ParseDriverOptions().
354 c101= [NET] Moxa C101 synchronous serial card
356 cachesize= [BUGS=IA-32] Override level 2 CPU cache size detection.
357 Sometimes CPU hardware bugs make them report the cache
358 size incorrectly. The kernel will attempt work arounds
359 to fix known problems, but for some CPUs it is not
360 possible to determine what the correct size should be.
361 This option provides an override for these situations.
363 chandev= [HW,NET] Generic channel device initialisation
365 checkreqprot [SELINUX] Set initial checkreqprot flag value.
366 Format: { "0" | "1" }
367 See security/selinux/Kconfig help text.
368 0 -- check protection applied by kernel (includes
369 any implied execute protection).
370 1 -- check protection requested by application.
371 Default value is set via a kernel config option.
372 Value can be changed at runtime via
373 /selinux/checkreqprot.
375 clock= [BUGS=IA-32, HW] gettimeofday clocksource override.
376 [Deprecated]
377 Forces specified clocksource (if available) to be used
378 when calculating gettimeofday(). If specified
379 clocksource is not available, it defaults to PIT.
380 Format: { pit | tsc | cyclone | pmtmr }
382 clocksource= [GENERIC_TIME] Override the default clocksource
383 Format: <string>
384 Override the default clocksource and use the clocksource
385 with the name specified.
386 Some clocksource names to choose from, depending on
387 the platform:
388 [all] jiffies (this is the base, fallback clocksource)
389 [ACPI] acpi_pm
390 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
391 pxa_timer,timer3,32k_counter,timer0_1
392 [AVR32] avr32
393 [IA-32] pit,hpet,tsc,vmi-timer;
394 scx200_hrt on Geode; cyclone on IBM x440
395 [MIPS] MIPS
396 [PARISC] cr16
397 [S390] tod
398 [SH] SuperH
399 [SPARC64] tick
400 [X86-64] hpet,tsc
402 code_bytes [IA32] How many bytes of object code to print in an
403 oops report.
404 Range: 0 - 8192
405 Default: 64
407 disable_8254_timer
408 enable_8254_timer
409 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
410 over the 8254 in addition to over the IO-APIC. The
411 kernel tries to set a sensible default.
413 hpet= [IA-32,HPET] option to disable HPET and use PIT.
414 Format: disable
416 com20020= [HW,NET] ARCnet - COM20020 chipset
417 Format:
418 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
420 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
421 Format: <io>[,<irq>]
423 com90xx= [HW,NET]
424 ARCnet - COM90xx chipset (memory-mapped buffers)
425 Format: <io>[,<irq>[,<memstart>]]
427 condev= [HW,S390] console device
428 conmode=
430 console= [KNL] Output console device and options.
432 tty<n> Use the virtual console device <n>.
434 ttyS<n>[,options]
435 ttyUSB0[,options]
436 Use the specified serial port. The options are of
437 the form "bbbbpnf", where "bbbb" is the baud rate,
438 "p" is parity ("n", "o", or "e"), "n" is number of
439 bits, and "f" is flow control ("r" for RTS or
440 omit it). Default is "9600n8".
442 See Documentation/serial-console.txt for more
443 information. See
444 Documentation/networking/netconsole.txt for an
445 alternative.
447 uart[8250],io,<addr>[,options]
448 uart[8250],mmio,<addr>[,options]
449 Start an early, polled-mode console on the 8250/16550
450 UART at the specified I/O port or MMIO address,
451 switching to the matching ttyS device later. The
452 options are the same as for ttyS, above.
454 earlycon= [KNL] Output early console device and options.
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 The options are the same as for ttyS, above.
461 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
462 Format:
463 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
465 cpia_pp= [HW,PPT]
466 Format: { parport<nr> | auto | none }
468 crashkernel=nn[KMG]@ss[KMG]
469 [KNL] Reserve a chunk of physical memory to
470 hold a kernel to switch to with kexec on panic.
472 cs4232= [HW,OSS]
473 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
475 cs89x0_dma= [HW,NET]
476 Format: <dma>
478 cs89x0_media= [HW,NET]
479 Format: { rj45 | aui | bnc }
481 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
483 dasd= [HW,NET]
484 See header of drivers/s390/block/dasd_devmap.c.
486 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
487 (one device per port)
488 Format: <port#>,<type>
489 See also Documentation/input/joystick-parport.txt
491 debug [KNL] Enable kernel debugging (events log level).
493 debug_locks_verbose=
494 [KNL] verbose self-tests
495 Format=<0|1>
496 Print debugging info while doing the locking API
497 self-tests.
498 We default to 0 (no extra messages), setting it to
499 1 will print _a lot_ more information - normally
500 only useful to kernel developers.
502 decnet= [HW,NET]
503 Format: <area>[,<node>]
504 See also Documentation/networking/decnet.txt.
506 default_blu= [VT]
507 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
508 Change the default blue palette of the console.
509 This is a 16-member array composed of values
510 ranging from 0-255.
512 default_grn= [VT]
513 Format: <green0>,<green1>,<green2>,...,<green15>
514 Change the default green palette of the console.
515 This is a 16-member array composed of values
516 ranging from 0-255.
518 default_red= [VT]
519 Format: <red0>,<red1>,<red2>,...,<red15>
520 Change the default red palette of the console.
521 This is a 16-member array composed of values
522 ranging from 0-255.
524 default_utf8= [VT]
525 Format=<0|1>
526 Set system-wide default UTF-8 mode for all tty's.
527 Default is 0 and by setting to 1, it enables UTF-8
528 mode for all newly opened or allocated terminals.
530 dhash_entries= [KNL]
531 Set number of hash buckets for dentry cache.
533 digi= [HW,SERIAL]
534 IO parameters + enable/disable command.
536 digiepca= [HW,SERIAL]
537 See drivers/char/README.epca and
538 Documentation/digiepca.txt.
540 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
541 support available.
542 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
544 dmasound= [HW,OSS] Sound subsystem buffers
546 dscc4.setup= [NET]
548 dtc3181e= [HW,SCSI]
550 earlyprintk= [IA-32,X86-64,SH]
551 earlyprintk=vga
552 earlyprintk=serial[,ttySn[,baudrate]]
554 Append ",keep" to not disable it when the real console
555 takes over.
557 Only vga or serial at a time, not both.
559 Currently only ttyS0 and ttyS1 are supported.
561 Interaction with the standard serial driver is not
562 very good.
564 The VGA output is eventually overwritten by the real
565 console.
567 eata= [HW,SCSI]
569 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
570 Format: <int>
571 0: polling mode
572 non-0: interrupt mode (default)
574 eda= [HW,PS2]
576 edb= [HW,PS2]
578 edd= [EDD]
579 Format: {"of[f]" | "sk[ipmbr]"}
580 See comment in arch/i386/boot/edd.S
582 eicon= [HW,ISDN]
583 Format: <id>,<membase>,<irq>
585 eisa_irq_edge= [PARISC,HW]
586 See header of drivers/parisc/eisa.c.
588 elanfreq= [IA-32]
589 See comment before function elanfreq_setup() in
590 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
592 elevator= [IOSCHED]
593 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
594 See Documentation/block/as-iosched.txt and
595 Documentation/block/deadline-iosched.txt for details.
597 elfcorehdr= [IA-32, X86_64]
598 Specifies physical address of start of kernel core
599 image elf header. Generally kexec loader will
600 pass this option to capture kernel.
601 See Documentation/kdump/kdump.txt for details.
603 enforcing [SELINUX] Set initial enforcing status.
604 Format: {"0" | "1"}
605 See security/selinux/Kconfig help text.
606 0 -- permissive (log only, no denials).
607 1 -- enforcing (deny and log).
608 Default value is 0.
609 Value can be changed at runtime via /selinux/enforce.
611 es1371= [HW,OSS]
612 Format: <spdif>,[<nomix>,[<amplifier>]]
613 See also header of sound/oss/es1371.c.
615 ether= [HW,NET] Ethernet cards parameters
616 This option is obsoleted by the "netdev=" option, which
617 has equivalent usage. See its documentation for details.
619 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
620 Format: <io>[,<irq>]
622 failslab=
623 fail_page_alloc=
624 fail_make_request=[KNL]
625 General fault injection mechanism.
626 Format: <interval>,<probability>,<space>,<times>
627 See also /Documentation/fault-injection/.
629 fd_mcs= [HW,SCSI]
630 See header of drivers/scsi/fd_mcs.c.
632 fdomain= [HW,SCSI]
633 See header of drivers/scsi/fdomain.c.
635 floppy= [HW]
636 See Documentation/floppy.txt.
638 gamecon.map[2|3]=
639 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
640 support via parallel port (up to 5 devices per port)
641 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
642 See also Documentation/input/joystick-parport.txt
644 gamma= [HW,DRM]
646 gdth= [HW,SCSI]
647 See header of drivers/scsi/gdth.c.
649 gpt [EFI] Forces disk with valid GPT signature but
650 invalid Protective MBR to be treated as GPT.
652 gvp11= [HW,SCSI]
654 hashdist= [KNL,NUMA] Large hashes allocated during boot
655 are distributed across NUMA nodes. Defaults on
656 for IA-64, off otherwise.
657 Format: 0 | 1 (for off | on)
659 hcl= [IA-64] SGI's Hardware Graph compatibility layer
661 hd= [EIDE] (E)IDE hard drive subsystem geometry
662 Format: <cyl>,<head>,<sect>
664 hd?= [HW] (E)IDE subsystem
665 hd?lun= See Documentation/ide.txt.
667 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
668 size of <nn>. This works even on boxes that have no
669 highmem otherwise. This also works to reduce highmem
670 size on bigger boxes.
672 highres= [KNL] Enable/disable high resolution timer mode.
673 Valid parameters: "on", "off"
674 Default: "on"
676 hisax= [HW,ISDN]
677 See Documentation/isdn/README.HiSax.
679 hugepages= [HW,IA-32,IA-64] Maximal number of HugeTLB pages.
681 i8042.direct [HW] Put keyboard port into non-translated mode
682 i8042.dumbkbd [HW] Pretend that controller can only read data from
683 keyboard and cannot control its state
684 (Don't attempt to blink the leds)
685 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
686 i8042.nokbd [HW] Don't check/create keyboard port
687 i8042.nomux [HW] Don't check presence of an active multiplexing
688 controller
689 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
690 controllers
691 i8042.panicblink=
692 [HW] Frequency with which keyboard LEDs should blink
693 when kernel panics (default is 0.5 sec)
694 i8042.reset [HW] Reset the controller during init and cleanup
695 i8042.unlock [HW] Unlock (ignore) the keylock
697 i810= [HW,DRM]
699 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
700 indicates that the driver is running on unsupported
701 hardware.
702 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
703 does not match list of supported models.
704 i8k.power_status
705 [HW] Report power status in /proc/i8k
706 (disabled by default)
707 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
708 capability is set.
710 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
711 See Documentation/mca.txt.
713 icn= [HW,ISDN]
714 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
716 ide= [HW] (E)IDE subsystem
717 Format: ide=nodma or ide=doubler or ide=reverse
718 See Documentation/ide.txt.
720 ide?= [HW] (E)IDE subsystem
721 Format: ide?=noprobe or chipset specific parameters.
722 See Documentation/ide.txt.
724 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
725 See Documentation/ide.txt.
727 idle= [X86]
728 Format: idle=poll or idle=mwait
729 Poll forces a polling idle loop that can slightly improves the performance
730 of waking up a idle CPU, but will use a lot of power and make the system
731 run hot. Not recommended.
732 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
733 to not use it because it doesn't save as much power as a normal idle
734 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
735 as idle=poll.
737 ignore_loglevel [KNL]
738 Ignore loglevel setting - this will print /all/
739 kernel messages to the console. Useful for debugging.
741 ihash_entries= [KNL]
742 Set number of hash buckets for inode cache.
744 in2000= [HW,SCSI]
745 See header of drivers/scsi/in2000.c.
747 init= [KNL]
748 Format: <full_path>
749 Run specified binary instead of /sbin/init as init
750 process.
752 initcall_debug [KNL] Trace initcalls as they are executed. Useful
753 for working out where the kernel is dying during
754 startup.
756 initrd= [BOOT] Specify the location of the initial ramdisk
758 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
759 Format: <irq>
761 inttest= [IA64]
763 io7= [HW] IO7 for Marvel based alpha systems
764 See comment before marvel_specify_io7 in
765 arch/alpha/kernel/core_marvel.c.
767 ip= [IP_PNP]
768 See Documentation/nfsroot.txt.
770 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
771 See comment before ip2_setup() in drivers/char/ip2.c.
773 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
774 See header of drivers/scsi/ips.c.
776 ports= [IP_VS_FTP] IPVS ftp helper module
777 Default is 21.
778 Up to 8 (IP_VS_APP_MAX_PORTS) ports
779 may be specified.
780 Format: <port>,<port>....
782 irqfixup [HW]
783 When an interrupt is not handled search all handlers
784 for it. Intended to get systems with badly broken
785 firmware running.
787 irqpoll [HW]
788 When an interrupt is not handled search all handlers
789 for it. Also check all handlers each timer
790 interrupt. Intended to get systems with badly broken
791 firmware running.
793 isapnp= [ISAPNP]
794 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
796 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
797 Format:
798 <cpu number>,...,<cpu number>
799 or
800 <cpu number>-<cpu number> (must be a positive range in ascending order)
801 or a mixture
802 <cpu number>,...,<cpu number>-<cpu number>
803 This option can be used to specify one or more CPUs
804 to isolate from the general SMP balancing and scheduling
805 algorithms. The only way to move a process onto or off
806 an "isolated" CPU is via the CPU affinity syscalls.
807 <cpu number> begins at 0 and the maximum value is
808 "number of CPUs in system - 1".
810 This option is the preferred way to isolate CPUs. The
811 alternative -- manually setting the CPU mask of all
812 tasks in the system -- can cause problems and
813 suboptimal load balancer performance.
815 iucv= [HW,NET]
817 js= [HW,JOY] Analog joystick
818 See Documentation/input/joystick.txt.
820 kernelcore=nn[KMG] [KNL,IA-32,IA-64,PPC,X86-64] This parameter
821 specifies the amount of memory usable by the kernel
822 for non-movable allocations. The requested amount is
823 spread evenly throughout all nodes in the system. The
824 remaining memory in each node is used for Movable
825 pages. In the event, a node is too small to have both
826 kernelcore and Movable pages, kernelcore pages will
827 take priority and other nodes will have a larger number
828 of kernelcore pages. The Movable zone is used for the
829 allocation of pages that may be reclaimed or moved
830 by the page migration subsystem. This means that
831 HugeTLB pages may not be allocated from this zone.
832 Note that allocations like PTEs-from-HighMem still
833 use the HighMem zone if it exists, and the Normal
834 zone if it does not.
836 keepinitrd [HW,ARM]
838 kstack=N [IA-32,X86-64] Print N words from the kernel stack
839 in oops dumps.
841 l2cr= [PPC]
843 lapic [IA-32,APIC] Enable the local APIC even if BIOS
844 disabled it.
846 lapic_timer_c2_ok [IA-32,x86-64,APIC] trust the local apic timer in
847 C2 power state.
849 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
850 Format: addr:<io>,irq:<irq>
852 legacy_serial.force [HW,IA-32,X86-64]
853 Probe for COM ports at legacy addresses even
854 if PNPBIOS or ACPI should describe them. This
855 is for working around firmware defects.
857 llsc*= [IA64] See function print_params() in
858 arch/ia64/sn/kernel/llsc4.c.
860 load_ramdisk= [RAM] List of ramdisks to load from floppy
861 See Documentation/ramdisk.txt.
863 lockd.nlm_grace_period=P [NFS] Assign grace period.
864 Format: <integer>
866 lockd.nlm_tcpport=N [NFS] Assign TCP port.
867 Format: <integer>
869 lockd.nlm_timeout=T [NFS] Assign timeout value.
870 Format: <integer>
872 lockd.nlm_udpport=M [NFS] Assign UDP port.
873 Format: <integer>
875 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
876 Format: <irq>
878 loglevel= All Kernel Messages with a loglevel smaller than the
879 console loglevel will be printed to the console. It can
880 also be changed with klogd or other programs. The
881 loglevels are defined as follows:
883 0 (KERN_EMERG) system is unusable
884 1 (KERN_ALERT) action must be taken immediately
885 2 (KERN_CRIT) critical conditions
886 3 (KERN_ERR) error conditions
887 4 (KERN_WARNING) warning conditions
888 5 (KERN_NOTICE) normal but significant condition
889 6 (KERN_INFO) informational
890 7 (KERN_DEBUG) debug-level messages
892 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
893 Format: { n | nk | nM }
894 n must be a power of two. The default size
895 is set in the kernel config file.
897 lp=0 [LP] Specify parallel ports to use, e.g,
898 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
899 lp=reset first parallel port). 'lp=0' disables the
900 lp=auto printer driver. 'lp=reset' (which can be
901 specified in addition to the ports) causes
902 attached printers to be reset. Using
903 lp=port1,port2,... specifies the parallel ports
904 to associate lp devices with, starting with
905 lp0. A port specification may be 'none' to skip
906 that lp device, or a parport name such as
907 'parport0'. Specifying 'lp=auto' instead of a
908 port specification list means that device IDs
909 from each port should be examined, to see if
910 an IEEE 1284-compliant printer is attached; if
911 so, the driver will manage that printer.
912 See also header of drivers/char/lp.c.
914 lpj=n [KNL]
915 Sets loops_per_jiffy to given constant, thus avoiding
916 time-consuming boot-time autodetection (up to 250 ms per
917 CPU). 0 enables autodetection (default). To determine
918 the correct value for your kernel, boot with normal
919 autodetection and see what value is printed. Note that
920 on SMP systems the preset will be applied to all CPUs,
921 which is likely to cause problems if your CPUs need
922 significantly divergent settings. An incorrect value
923 will cause delays in the kernel to be wrong, leading to
924 unpredictable I/O errors and other breakage. Although
925 unlikely, in the extreme case this might damage your
926 hardware.
928 ltpc= [NET]
929 Format: <io>,<irq>,<dma>
931 mac5380= [HW,SCSI] Format:
932 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
934 mac53c9x= [HW,SCSI] Format:
935 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
937 machvec= [IA64] Force the use of a particular machine-vector
938 (machvec) in a generic kernel.
939 Example: machvec=hpzx1_swiotlb
941 max_loop= [LOOP] Maximum number of loopback devices that can
942 be mounted
943 Format: <1-256>
945 maxcpus= [SMP] Maximum number of processors that an SMP kernel
946 should make use of.
947 Using "nosmp" or "maxcpus=0" will disable SMP
948 entirely (the MPS table probe still happens, though).
949 A command-line option of "maxcpus=<NUM>", where <NUM>
950 is an integer greater than 0, limits the maximum number
951 of CPUs activated in SMP mode to <NUM>.
952 Using "maxcpus=1" on an SMP kernel is the trivial
953 case of an SMP kernel with only one CPU.
955 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
956 equal to this physical address is ignored.
958 max_luns= [SCSI] Maximum number of LUNs to probe.
959 Should be between 1 and 2^32-1.
961 max_report_luns=
962 [SCSI] Maximum number of LUNs received.
963 Should be between 1 and 16384.
965 mca-pentium [BUGS=IA-32]
967 mcatest= [IA-64]
969 mce [IA-32] Machine Check Exception
971 md= [HW] RAID subsystems devices and level
972 See Documentation/md.txt.
974 mdacon= [MDA]
975 Format: <first>,<last>
976 Specifies range of consoles to be captured by the MDA.
978 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
979 Amount of memory to be used when the kernel is not able
980 to see the whole system memory or for test.
981 [IA-32] Use together with memmap= to avoid physical
982 address space collisions. Without memmap= PCI devices
983 could be placed at addresses belonging to unused RAM.
985 mem=nopentium [BUGS=IA-32] Disable usage of 4MB pages for kernel
986 memory.
988 memmap=exactmap [KNL,IA-32,X86_64] Enable setting of an exact
989 E820 memory map, as specified by the user.
990 Such memmap=exactmap lines can be constructed based on
991 BIOS output or other requirements. See the memmap=nn@ss
992 option description.
994 memmap=nn[KMG]@ss[KMG]
995 [KNL] Force usage of a specific region of memory
996 Region of memory to be used, from ss to ss+nn.
998 memmap=nn[KMG]#ss[KMG]
999 [KNL,ACPI] Mark specific memory as ACPI data.
1000 Region of memory to be used, from ss to ss+nn.
1002 memmap=nn[KMG]$ss[KMG]
1003 [KNL,ACPI] Mark specific memory as reserved.
1004 Region of memory to be used, from ss to ss+nn.
1006 meye.*= [HW] Set MotionEye Camera parameters
1007 See Documentation/video4linux/meye.txt.
1009 mga= [HW,DRM]
1011 mousedev.tap_time=
1012 [MOUSE] Maximum time between finger touching and
1013 leaving touchpad surface for touch to be considered
1014 a tap and be reported as a left button click (for
1015 touchpads working in absolute mode only).
1016 Format: <msecs>
1017 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1018 reporting absolute coordinates, such as tablets
1019 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1020 reporting absolute coordinates, such as tablets
1022 mpu401= [HW,OSS]
1023 Format: <io>,<irq>
1025 MTD_Partition= [MTD]
1026 Format: <name>,<region-number>,<size>,<offset>
1028 MTD_Region= [MTD] Format:
1029 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1031 mtdparts= [MTD]
1032 See drivers/mtd/cmdline.c.
1034 mtouchusb.raw_coordinates=
1035 [HW] Make the MicroTouch USB driver use raw coordinates
1036 ('y', default) or cooked coordinates ('n')
1038 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1040 NCR_D700= [HW,SCSI]
1041 See header of drivers/scsi/NCR_D700.c.
1043 ncr5380= [HW,SCSI]
1045 ncr53c400= [HW,SCSI]
1047 ncr53c400a= [HW,SCSI]
1049 ncr53c406a= [HW,SCSI]
1051 ncr53c8xx= [HW,SCSI]
1053 netdev= [NET] Network devices parameters
1054 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1055 Note that mem_start is often overloaded to mean
1056 something different and driver-specific.
1057 This usage is only documented in each driver source
1058 file if at all.
1060 nfsaddrs= [NFS]
1061 See Documentation/nfsroot.txt.
1063 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1064 See Documentation/nfsroot.txt.
1066 nfs.callback_tcpport=
1067 [NFS] set the TCP port on which the NFSv4 callback
1068 channel should listen.
1070 nfs.idmap_cache_timeout=
1071 [NFS] set the maximum lifetime for idmapper cache
1072 entries.
1074 nmi_watchdog= [KNL,BUGS=IA-32] Debugging features for SMP kernels
1076 no387 [BUGS=IA-32] Tells the kernel to use the 387 maths
1077 emulation library even if a 387 maths coprocessor
1078 is present.
1080 noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1081 when set.
1082 Format: <int>
1084 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1085 caches in the slab allocator. Saves per-node memory,
1086 but will impact performance.
1088 noalign [KNL,ARM]
1090 noapic [SMP,APIC] Tells the kernel to not make use of any
1091 IOAPICs that may be present in the system.
1093 noasync [HW,M68K] Disables async and sync negotiation for
1094 all devices.
1096 nobats [PPC] Do not use BATs for mapping kernel lowmem
1097 on "Classic" PPC cores.
1099 nocache [ARM]
1101 nodelayacct [KNL] Disable per-task delay accounting
1103 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1105 noexec [IA-64]
1107 noexec [IA-32,X86-64]
1108 noexec=on: enable non-executable mappings (default)
1109 noexec=off: disable nn-executable mappings
1111 nofxsr [BUGS=IA-32] Disables x86 floating point extended
1112 register save and restore. The kernel will only save
1113 legacy floating-point registers on task switch.
1115 nohlt [BUGS=ARM]
1117 no-hlt [BUGS=IA-32] Tells the kernel that the hlt
1118 instruction doesn't work correctly and not to
1119 use it.
1121 nohalt [IA-64] Tells the kernel not to use the power saving
1122 function PAL_HALT_LIGHT when idle. This increases
1123 power-consumption. On the positive side, it reduces
1124 interrupt wake-up latency, which may improve performance
1125 in certain environments such as networked servers or
1126 real-time systems.
1128 nohz= [KNL] Boottime enable/disable dynamic ticks
1129 Valid arguments: on, off
1130 Default: on
1132 noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing
1134 noirqdebug [IA-32] Disables the code which attempts to detect and
1135 disable unhandled interrupt sources.
1137 no_timer_check [IA-32,X86_64,APIC] Disables the code which tests for
1138 broken timer IRQ sources.
1140 noisapnp [ISAPNP] Disables ISA PnP code.
1142 noinitrd [RAM] Tells the kernel not to load any configured
1143 initial RAM disk.
1145 nointroute [IA-64]
1147 nolapic [IA-32,APIC] Do not enable or use the local APIC.
1149 nolapic_timer [IA-32,APIC] Do not use the local APIC timer.
1151 noltlbs [PPC] Do not use large page/tlb entries for kernel
1152 lowmem mapping on PPC40x.
1154 nomca [IA-64] Disable machine check abort handling
1156 nomce [IA-32] Machine Check Exception
1158 noreplace-paravirt [IA-32,PV_OPS] Don't patch paravirt_ops
1160 noreplace-smp [IA-32,SMP] Don't replace SMP instructions
1161 with UP alternatives
1163 noresidual [PPC] Don't use residual data on PReP machines.
1165 noresume [SWSUSP] Disables resume and restores original swap
1166 space.
1168 no-scroll [VGA] Disables scrollback.
1169 This is required for the Braillex ib80-piezo Braille
1170 reader made by F.H. Papenmeier (Germany).
1172 nosbagart [IA-64]
1174 nosep [BUGS=IA-32] Disables x86 SYSENTER/SYSEXIT support.
1176 nosmp [SMP] Tells an SMP kernel to act as a UP kernel.
1178 nosoftlockup [KNL] Disable the soft-lockup detector.
1180 nosync [HW,M68K] Disables sync negotiation for all devices.
1182 notsc [BUGS=IA-32] Disable Time Stamp Counter
1184 nousb [USB] Disable the USB subsystem
1186 nowb [ARM]
1188 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1189 one of ['zone', 'node', 'default'] can be specified
1190 This can be set from sysctl after boot.
1191 See Documentation/sysctl/vm.txt for details.
1193 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1195 opl3= [HW,OSS]
1196 Format: <io>
1198 oprofile.timer= [HW]
1199 Use timer interrupt instead of performance counters
1201 osst= [HW,SCSI] SCSI Tape Driver
1202 Format: <buffer_size>,<write_threshold>
1203 See also Documentation/scsi/st.txt.
1205 panic= [KNL] Kernel behaviour on panic
1206 Format: <timeout>
1208 parkbd.port= [HW] Parallel port number the keyboard adapter is
1209 connected to, default is 0.
1210 Format: <parport#>
1211 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1212 0 for XT, 1 for AT (default is AT).
1213 Format: <mode>
1215 parport= [HW,PPT] Specify parallel ports. 0 disables.
1216 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1217 Use 'auto' to force the driver to use any
1218 IRQ/DMA settings detected (the default is to
1219 ignore detected IRQ/DMA settings because of
1220 possible conflicts). You can specify the base
1221 address, IRQ, and DMA settings; IRQ and DMA
1222 should be numbers, or 'auto' (for using detected
1223 settings on that particular port), or 'nofifo'
1224 (to avoid using a FIFO even if it is detected).
1225 Parallel ports are assigned in the order they
1226 are specified on the command line, starting
1227 with parport0.
1229 parport_init_mode= [HW,PPT]
1230 Configure VIA parallel port to operate in
1231 a specific mode. This is necessary on Pegasos
1232 computer where firmware has no options for setting
1233 up parallel port mode and sets it to spp.
1234 Currently this function knows 686a and 8231 chips.
1235 Format: [spp|ps2|epp|ecp|ecpepp]
1237 pas2= [HW,OSS] Format:
1238 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1240 pas16= [HW,SCSI]
1241 See header of drivers/scsi/pas16.c.
1243 pause_on_oops=
1244 Halt all CPUs after the first oops has been printed for
1245 the specified number of seconds. This is to be used if
1246 your oopses keep scrolling off the screen.
1248 pcbit= [HW,ISDN]
1250 pcd. [PARIDE]
1251 See header of drivers/block/paride/pcd.c.
1252 See also Documentation/paride.txt.
1254 pci=option[,option...] [PCI] various PCI subsystem options:
1255 off [IA-32] don't probe for the PCI bus
1256 bios [IA-32] force use of PCI BIOS, don't access
1257 the hardware directly. Use this if your machine
1258 has a non-standard PCI host bridge.
1259 nobios [IA-32] disallow use of PCI BIOS, only direct
1260 hardware access methods are allowed. Use this
1261 if you experience crashes upon bootup and you
1262 suspect they are caused by the BIOS.
1263 conf1 [IA-32] Force use of PCI Configuration
1264 Mechanism 1.
1265 conf2 [IA-32] Force use of PCI Configuration
1266 Mechanism 2.
1267 nommconf [IA-32,X86_64] Disable use of MMCONFIG for PCI
1268 Configuration
1269 nomsi [MSI] If the PCI_MSI kernel config parameter is
1270 enabled, this kernel boot option can be used to
1271 disable the use of MSI interrupts system-wide.
1272 nosort [IA-32] Don't sort PCI devices according to
1273 order given by the PCI BIOS. This sorting is
1274 done to get a device order compatible with
1275 older kernels.
1276 biosirq [IA-32] Use PCI BIOS calls to get the interrupt
1277 routing table. These calls are known to be buggy
1278 on several machines and they hang the machine
1279 when used, but on other computers it's the only
1280 way to get the interrupt routing table. Try
1281 this option if the kernel is unable to allocate
1282 IRQs or discover secondary PCI buses on your
1283 motherboard.
1284 rom [IA-32] Assign address space to expansion ROMs.
1285 Use with caution as certain devices share
1286 address decoders between ROMs and other
1287 resources.
1288 irqmask=0xMMMM [IA-32] Set a bit mask of IRQs allowed to be
1289 assigned automatically to PCI devices. You can
1290 make the kernel exclude IRQs of your ISA cards
1291 this way.
1292 pirqaddr=0xAAAAA [IA-32] Specify the physical address
1293 of the PIRQ table (normally generated
1294 by the BIOS) if it is outside the
1295 F0000h-100000h range.
1296 lastbus=N [IA-32] Scan all buses thru bus #N. Can be
1297 useful if the kernel is unable to find your
1298 secondary buses and you want to tell it
1299 explicitly which ones they are.
1300 assign-busses [IA-32] Always assign all PCI bus
1301 numbers ourselves, overriding
1302 whatever the firmware may have done.
1303 usepirqmask [IA-32] Honor the possible IRQ mask stored
1304 in the BIOS $PIR table. This is needed on
1305 some systems with broken BIOSes, notably
1306 some HP Pavilion N5400 and Omnibook XE3
1307 notebooks. This will have no effect if ACPI
1308 IRQ routing is enabled.
1309 noacpi [IA-32] Do not use ACPI for IRQ routing
1310 or for PCI scanning.
1311 routeirq Do IRQ routing for all PCI devices.
1312 This is normally done in pci_enable_device(),
1313 so this option is a temporary workaround
1314 for broken drivers that don't call it.
1315 firmware [ARM] Do not re-enumerate the bus but instead
1316 just use the configuration from the
1317 bootloader. This is currently used on
1318 IXP2000 systems where the bus has to be
1319 configured a certain way for adjunct CPUs.
1320 noearly [X86] Don't do any early type 1 scanning.
1321 This might help on some broken boards which
1322 machine check when some devices' config space
1323 is read. But various workarounds are disabled
1324 and some IOMMU drivers will not work.
1325 bfsort Sort PCI devices into breadth-first order.
1326 This sorting is done to get a device
1327 order compatible with older (<= 2.4) kernels.
1328 nobfsort Don't sort PCI devices into breadth-first order.
1329 cbiosize=nn[KMG] The fixed amount of bus space which is
1330 reserved for the CardBus bridge's IO window.
1331 The default value is 256 bytes.
1332 cbmemsize=nn[KMG] The fixed amount of bus space which is
1333 reserved for the CardBus bridge's memory
1334 window. The default value is 64 megabytes.
1336 pcmv= [HW,PCMCIA] BadgePAD 4
1338 pd. [PARIDE]
1339 See Documentation/paride.txt.
1341 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1342 boot time.
1343 Format: { 0 | 1 }
1344 See arch/parisc/kernel/pdc_chassis.c
1346 pf. [PARIDE]
1347 See Documentation/paride.txt.
1349 pg. [PARIDE]
1350 See Documentation/paride.txt.
1352 pirq= [SMP,APIC] Manual mp-table setup
1353 See Documentation/i386/IO-APIC.txt.
1355 plip= [PPT,NET] Parallel port network link
1356 Format: { parport<nr> | timid | 0 }
1357 See also Documentation/parport.txt.
1359 pnpacpi= [ACPI]
1360 { off }
1362 pnpbios= [ISAPNP]
1363 { on | off | curr | res | no-curr | no-res }
1365 pnp_reserve_irq=
1366 [ISAPNP] Exclude IRQs for the autoconfiguration
1368 pnp_reserve_dma=
1369 [ISAPNP] Exclude DMAs for the autoconfiguration
1371 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1372 Ranges are in pairs (I/O port base and size).
1374 pnp_reserve_mem=
1375 [ISAPNP] Exclude memory regions for the
1376 autoconfiguration.
1377 Ranges are in pairs (memory base and size).
1379 print-fatal-signals=
1380 [KNL] debug: print fatal signals
1381 print-fatal-signals=1: print segfault info to
1382 the kernel console.
1383 default: off.
1385 printk.time= Show timing data prefixed to each printk message line
1386 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1388 profile= [KNL] Enable kernel profiling via /proc/profile
1389 Format: [schedule,]<number>
1390 Param: "schedule" - profile schedule points.
1391 Param: <number> - step/bucket size as a power of 2 for
1392 statistical time based profiling.
1393 Param: "sleep" - profile D-state sleeping (millisecs)
1395 processor.max_cstate= [HW,ACPI]
1396 Limit processor to maximum C-state
1397 max_cstate=9 overrides any DMI blacklist limit.
1399 processor.nocst [HW,ACPI]
1400 Ignore the _CST method to determine C-states,
1401 instead using the legacy FADT method
1403 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1404 before loading.
1405 See Documentation/ramdisk.txt.
1407 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1408 probe for; one of (bare|imps|exps|lifebook|any).
1409 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1410 per second.
1411 psmouse.resetafter= [HW,MOUSE]
1412 Try to reset the device after so many bad packets
1413 (0 = never).
1414 psmouse.resolution=
1415 [HW,MOUSE] Set desired mouse resolution, in dpi.
1416 psmouse.smartscroll=
1417 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1418 0 = disabled, 1 = enabled (default).
1420 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1421 Format:
1422 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1424 pt. [PARIDE]
1425 See Documentation/paride.txt.
1427 quiet [KNL] Disable most log messages
1429 r128= [HW,DRM]
1431 raid= [HW,RAID]
1432 See Documentation/md.txt.
1434 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1435 See Documentation/ramdisk.txt.
1437 ramdisk_blocksize= [RAM]
1438 See Documentation/ramdisk.txt.
1440 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1441 New name for the ramdisk parameter.
1442 See Documentation/ramdisk.txt.
1444 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1445 RCU callbacks to process in one batch.
1447 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1448 RCU callbacks over which batch limiting is disabled.
1450 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1451 RCU callbacks below which batch limiting is re-enabled.
1453 rdinit= [KNL]
1454 Format: <full_path>
1455 Run specified binary instead of /init from the ramdisk,
1456 used for early userspace startup. See initrd.
1458 reboot= [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1459 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1460 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1462 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1464 reservetop= [IA-32]
1465 Format: nn[KMG]
1466 Reserves a hole at the top of the kernel virtual
1467 address space.
1469 reset_devices [KNL] Force drivers to reset the underlying device
1470 during initialization.
1472 resume= [SWSUSP]
1473 Specify the partition device for software suspend
1475 resume_offset= [SWSUSP]
1476 Specify the offset from the beginning of the partition
1477 given by "resume=" at which the swap header is located,
1478 in <PAGE_SIZE> units (needed only for swap files).
1479 See Documentation/power/swsusp-and-swap-files.txt
1481 retain_initrd [RAM] Keep initrd memory after extraction
1483 rhash_entries= [KNL,NET]
1484 Set number of hash buckets for route cache
1486 riscom8= [HW,SERIAL]
1487 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1489 ro [KNL] Mount root device read-only on boot
1491 root= [KNL] Root filesystem
1493 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1494 mount the root filesystem
1496 rootflags= [KNL] Set root filesystem mount option string
1498 rootfstype= [KNL] Set root filesystem type
1500 rootwait [KNL] Wait (indefinitely) for root device to show up.
1501 Useful for devices that are detected asynchronously
1502 (e.g. USB and MMC devices).
1504 rw [KNL] Mount root device read-write on boot
1506 S [KNL] Run init in single mode
1508 sa1100ir [NET]
1509 See drivers/net/irda/sa1100_ir.c.
1511 sb= [HW,OSS]
1512 Format: <io>,<irq>,<dma>,<dma2>
1514 sbni= [NET] Granch SBNI12 leased line adapter
1516 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1517 Format: <io>[,<timeout>[,<isapnp>]]
1519 scsi_debug_*= [SCSI]
1520 See drivers/scsi/scsi_debug.c.
1522 scsi_default_dev_flags=
1523 [SCSI] SCSI default device flags
1524 Format: <integer>
1526 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1527 Format: <vendor>:<model>:<flags>
1528 (flags are integer value)
1530 scsi_logging= [SCSI]
1532 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1533 discovered. async scans them in kernel threads,
1534 allowing boot to proceed. none ignores them, expecting
1535 user space to do the scan.
1537 selinux [SELINUX] Disable or enable SELinux at boot time.
1538 Format: { "0" | "1" }
1539 See security/selinux/Kconfig help text.
1540 0 -- disable.
1541 1 -- enable.
1542 Default value is set via kernel config option.
1543 If enabled at boot time, /selinux/disable can be used
1544 later to disable prior to initial policy load.
1546 selinux_compat_net =
1547 [SELINUX] Set initial selinux_compat_net flag value.
1548 Format: { "0" | "1" }
1549 0 -- use new secmark-based packet controls
1550 1 -- use legacy packet controls
1551 Default value is 0 (preferred).
1552 Value can be changed at runtime via
1553 /selinux/compat_net.
1555 serialnumber [BUGS=IA-32]
1557 sg_def_reserved_size= [SCSI]
1559 shapers= [NET]
1560 Maximal number of shapers.
1562 sim710= [SCSI,HW]
1563 See header of drivers/scsi/sim710.c.
1565 simeth= [IA-64]
1566 simscsi=
1568 slram= [HW,MTD]
1570 slub_debug[=options[,slabs]] [MM, SLUB]
1571 Enabling slub_debug allows one to determine the
1572 culprit if slab objects become corrupted. Enabling
1573 slub_debug can create guard zones around objects and
1574 may poison objects when not in use. Also tracks the
1575 last alloc / free. For more information see
1576 Documentation/vm/slub.txt.
1578 slub_max_order= [MM, SLUB]
1579 Determines the maximum allowed order for slabs.
1580 A high setting may cause OOMs due to memory
1581 fragmentation. For more information see
1582 Documentation/vm/slub.txt.
1584 slub_min_objects= [MM, SLUB]
1585 The minimum number of objects per slab. SLUB will
1586 increase the slab order up to slub_max_order to
1587 generate a sufficiently large slab able to contain
1588 the number of objects indicated. The higher the number
1589 of objects the smaller the overhead of tracking slabs
1590 and the less frequently locks need to be acquired.
1591 For more information see Documentation/vm/slub.txt.
1593 slub_min_order= [MM, SLUB]
1594 Determines the mininum page order for slabs. Must be
1595 lower than slub_max_order.
1596 For more information see Documentation/vm/slub.txt.
1598 slub_nomerge [MM, SLUB]
1599 Disable merging of slabs with similar size. May be
1600 necessary if there is some reason to distinguish
1601 allocs to different slabs. Debug options disable
1602 merging on their own.
1603 For more information see Documentation/vm/slub.txt.
1605 smart2= [HW]
1606 Format: <io1>[,<io2>[,...,<io8>]]
1608 smp-alt-once [IA-32,SMP] On a hotplug CPU system, only
1609 attempt to substitute SMP alternatives once at boot.
1611 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1612 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1613 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1614 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1615 smsc-ircc2.ircc_irq= [HW] IRQ line
1616 smsc-ircc2.ircc_dma= [HW] DMA channel
1617 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1618 0: Toshiba Satellite 1800 (GP data pin select)
1619 1: Fast pin select (default)
1620 2: ATC IRMode
1622 snd-ad1816a= [HW,ALSA]
1624 snd-ad1848= [HW,ALSA]
1626 snd-ali5451= [HW,ALSA]
1628 snd-als100= [HW,ALSA]
1630 snd-als4000= [HW,ALSA]
1632 snd-azt2320= [HW,ALSA]
1634 snd-cmi8330= [HW,ALSA]
1636 snd-cmipci= [HW,ALSA]
1638 snd-cs4231= [HW,ALSA]
1640 snd-cs4232= [HW,ALSA]
1642 snd-cs4236= [HW,ALSA]
1644 snd-cs4281= [HW,ALSA]
1646 snd-cs46xx= [HW,ALSA]
1648 snd-dt019x= [HW,ALSA]
1650 snd-dummy= [HW,ALSA]
1652 snd-emu10k1= [HW,ALSA]
1654 snd-ens1370= [HW,ALSA]
1656 snd-ens1371= [HW,ALSA]
1658 snd-es968= [HW,ALSA]
1660 snd-es1688= [HW,ALSA]
1662 snd-es18xx= [HW,ALSA]
1664 snd-es1938= [HW,ALSA]
1666 snd-es1968= [HW,ALSA]
1668 snd-fm801= [HW,ALSA]
1670 snd-gusclassic= [HW,ALSA]
1672 snd-gusextreme= [HW,ALSA]
1674 snd-gusmax= [HW,ALSA]
1676 snd-hdsp= [HW,ALSA]
1678 snd-ice1712= [HW,ALSA]
1680 snd-intel8x0= [HW,ALSA]
1682 snd-interwave= [HW,ALSA]
1684 snd-interwave-stb=
1685 [HW,ALSA]
1687 snd-korg1212= [HW,ALSA]
1689 snd-maestro3= [HW,ALSA]
1691 snd-mpu401= [HW,ALSA]
1693 snd-mtpav= [HW,ALSA]
1695 snd-nm256= [HW,ALSA]
1697 snd-opl3sa2= [HW,ALSA]
1699 snd-opti92x-ad1848=
1700 [HW,ALSA]
1702 snd-opti92x-cs4231=
1703 [HW,ALSA]
1705 snd-opti93x= [HW,ALSA]
1707 snd-pmac= [HW,ALSA]
1709 snd-rme32= [HW,ALSA]
1711 snd-rme96= [HW,ALSA]
1713 snd-rme9652= [HW,ALSA]
1715 snd-sb8= [HW,ALSA]
1717 snd-sb16= [HW,ALSA]
1719 snd-sbawe= [HW,ALSA]
1721 snd-serial= [HW,ALSA]
1723 snd-sgalaxy= [HW,ALSA]
1725 snd-sonicvibes= [HW,ALSA]
1727 snd-sun-amd7930=
1728 [HW,ALSA]
1730 snd-sun-cs4231= [HW,ALSA]
1732 snd-trident= [HW,ALSA]
1734 snd-usb-audio= [HW,ALSA,USB]
1736 snd-via82xx= [HW,ALSA]
1738 snd-virmidi= [HW,ALSA]
1740 snd-wavefront= [HW,ALSA]
1742 snd-ymfpci= [HW,ALSA]
1744 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1745 See Documentation/sonypi.txt
1747 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1748 See Documentation/specialix.txt.
1750 spia_io_base= [HW,MTD]
1751 spia_fio_base=
1752 spia_pedr=
1753 spia_peddr=
1755 sscape= [HW,OSS]
1756 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1758 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1759 See Documentation/scsi/st.txt.
1761 st0x= [HW,SCSI]
1762 See header of drivers/scsi/seagate.c.
1764 sti= [PARISC,HW]
1765 Format: <num>
1766 Set the STI (builtin display/keyboard on the HP-PARISC
1767 machines) console (graphic card) which should be used
1768 as the initial boot-console.
1769 See also comment in drivers/video/console/sticore.c.
1771 sti_font= [HW]
1772 See comment in drivers/video/console/sticore.c.
1774 stifb= [HW]
1775 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1777 sunrpc.pool_mode=
1778 [NFS]
1779 Control how the NFS server code allocates CPUs to
1780 service thread pools. Depending on how many NICs
1781 you have and where their interrupts are bound, this
1782 option will affect which CPUs will do NFS serving.
1783 Note: this parameter cannot be changed while the
1784 NFS server is running.
1786 auto the server chooses an appropriate mode
1787 automatically using heuristics
1788 global a single global pool contains all CPUs
1789 percpu one pool for each CPU
1790 pernode one pool for each NUMA node (equivalent
1791 to global on non-NUMA machines)
1793 swiotlb= [IA-64] Number of I/O TLB slabs
1795 switches= [HW,M68k]
1797 sym53c416= [HW,SCSI]
1798 See header of drivers/scsi/sym53c416.c.
1800 sysrq_always_enabled
1801 [KNL]
1802 Ignore sysrq setting - this boot parameter will
1803 neutralize any effect of /proc/sys/kernel/sysrq.
1804 Useful for debugging.
1806 t128= [HW,SCSI]
1807 See header of drivers/scsi/t128.c.
1809 tdfx= [HW,DRM]
1811 thash_entries= [KNL,NET]
1812 Set number of hash buckets for TCP connection
1814 time Show timing data prefixed to each printk message line
1815 [deprecated, see 'printk.time']
1817 tipar.timeout= [HW,PPT]
1818 Set communications timeout in tenths of a second
1819 (default 15).
1821 tipar.delay= [HW,PPT]
1822 Set inter-bit delay in microseconds (default 10).
1824 tmc8xx= [HW,SCSI]
1825 See header of drivers/scsi/seagate.c.
1827 tmscsim= [HW,SCSI]
1828 See comment before function dc390_setup() in
1829 drivers/scsi/tmscsim.c.
1831 tp720= [HW,PS2]
1833 trix= [HW,OSS] MediaTrix AudioTrix Pro
1834 Format:
1835 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1837 tsdev.xres= [TS] Horizontal screen resolution.
1838 tsdev.yres= [TS] Vertical screen resolution.
1840 turbografx.map[2|3]= [HW,JOY]
1841 TurboGraFX parallel port interface
1842 Format:
1843 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1844 See also Documentation/input/joystick-parport.txt
1846 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1847 See header of drivers/scsi/u14-34f.c.
1849 uart401= [HW,OSS]
1850 Format: <io>,<irq>
1852 uart6850= [HW,OSS]
1853 Format: <io>,<irq>
1855 uhci-hcd.ignore_oc=
1856 [USB] Ignore overcurrent events (default N).
1857 Some badly-designed motherboards generate lots of
1858 bogus events, for ports that aren't wired to
1859 anything. Set this parameter to avoid log spamming.
1860 Note that genuine overcurrent events won't be
1861 reported either.
1863 usbcore.autosuspend=
1864 [USB] The autosuspend time delay (in seconds) used
1865 for newly-detected USB devices (default 2). This
1866 is the time required before an idle device will be
1867 autosuspended. Devices for which the delay is set
1868 to a negative value won't be autosuspended at all.
1870 usbhid.mousepoll=
1871 [USBHID] The interval which mice are to be polled at.
1873 vdso= [IA-32,SH]
1874 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1875 vdso=1: enable VDSO (default)
1876 vdso=0: disable VDSO mapping
1878 video= [FB] Frame buffer configuration
1879 See Documentation/fb/modedb.txt.
1881 vga= [BOOT,IA-32] Select a particular video mode
1882 See Documentation/i386/boot.txt and
1883 Documentation/svga.txt.
1884 Use vga=ask for menu.
1885 This is actually a boot loader parameter; the value is
1886 passed to the kernel using a special protocol.
1888 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1889 size of <nn>. This can be used to increase the
1890 minimum size (128MB on x86). It can also be used to
1891 decrease the size and leave more room for directly
1892 mapped kernel RAM.
1894 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1895 Format: <command>
1897 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1898 Format: <command>
1900 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1901 Format: <command>
1903 waveartist= [HW,OSS]
1904 Format: <io>,<irq>,<dma>,<dma2>
1906 wd33c93= [HW,SCSI]
1907 See header of drivers/scsi/wd33c93.c.
1909 wd7000= [HW,SCSI]
1910 See header of drivers/scsi/wd7000.c.
1912 wdt= [WDT] Watchdog
1913 See Documentation/watchdog/watchdog.txt.
1915 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1916 xd_geo= See header of drivers/block/xd.c.
1918 xirc2ps_cs= [NET,PCMCIA]
1919 Format:
1920 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1922 norandmaps Don't use address space randomization
1923 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1925 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1926 This is useful to get more information why
1927 you got a "dwarf2 unwinder stuck"
1929 ______________________________________________________________________
1931 TODO:
1933 Add documentation for ALSA options.
1934 Add more DRM drivers.