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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 DRM Direct Rendering Management support is enabled.
39 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
40 EFI EFI Partitioning (GPT) is enabled
41 EIDE EIDE/ATAPI support is enabled.
42 FB The frame buffer device is enabled.
43 HW Appropriate hardware 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 (Memory Technology Device) 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 is enabled.
67 PARIDE The ParIDE (parallel port IDE) 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 X86-32 X86-32, aka i386 architecture is enabled.
95 X86-64 X86-64 architecture is enabled.
96 More X86-64 boot options can be found in
97 Documentation/x86_64/boot-options.txt .
99 In addition, the following text indicates that the option:
101 BUGS= Relates to possible processor bugs on the said processor.
102 KNL Is a kernel start-up parameter.
103 BOOT Is a boot loader parameter.
105 Parameters denoted with BOOT are actually interpreted by the boot
106 loader, and have no meaning to the kernel directly.
107 Do not modify the syntax of boot loader parameters without extreme
108 need or coordination with <Documentation/i386/boot.txt>.
110 There are also arch-specific kernel-parameters not documented here.
111 See for example <Documentation/x86_64/boot-options.txt>.
113 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
114 a trailing = on the name of any parameter states that that parameter will
115 be entered as an environment variable, whereas its absence indicates that
116 it will appear as a kernel argument readable via /proc/cmdline by programs
117 running once the system is up.
119 The number of kernel parameters is not limited, but the length of the
120 complete command line (parameters including spaces etc.) is limited to
121 a fixed number of characters. This limit depends on the architecture
122 and is between 256 and 4096 characters. It is defined in the file
123 ./include/asm/setup.h as COMMAND_LINE_SIZE.
126 acpi= [HW,ACPI,X86-64,i386]
127 Advanced Configuration and Power Interface
128 Format: { force | off | ht | strict | noirq }
129 force -- enable ACPI if default was off
130 off -- disable ACPI if default was on
131 noirq -- do not use ACPI for IRQ routing
132 ht -- run only enough ACPI to enable Hyper Threading
133 strict -- Be less tolerant of platforms that are not
134 strictly ACPI specification compliant.
136 See also Documentation/pm.txt, pci=noacpi
138 acpi_apic_instance= [ACPI, IOAPIC]
139 Format: <int>
140 2: use 2nd APIC table, if available
141 1,0: use 1st APIC table
142 default: 0
144 acpi_sleep= [HW,ACPI] Sleep options
145 Format: { s3_bios, s3_mode }
146 See Documentation/power/video.txt
148 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
149 Format: { level | edge | high | low }
151 acpi_irq_balance [HW,ACPI]
152 ACPI will balance active IRQs
153 default in APIC mode
155 acpi_irq_nobalance [HW,ACPI]
156 ACPI will not move active IRQs (default)
157 default in PIC mode
159 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
160 use by PCI
161 Format: <irq>,<irq>...
163 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
164 Format: <irq>,<irq>...
166 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
167 Format: To spoof as Windows 98: ="Microsoft Windows"
169 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
170 acpi_osi="string1" # add string1 -- only one string
171 acpi_osi="!string2" # remove built-in string2
172 acpi_osi= # disable all strings
174 acpi_serialize [HW,ACPI] force serialization of AML methods
176 acpi_skip_timer_override [HW,ACPI]
177 Recognize and ignore IRQ0/pin2 Interrupt Override.
178 For broken nForce2 BIOS resulting in XT-PIC timer.
179 acpi_use_timer_override [HW,ACPI}
180 Use timer override. For some broken Nvidia NF5 boards
181 that require a timer override, but don't have
182 HPET
184 acpi.debug_layer= [HW,ACPI]
185 Format: <int>
186 Each bit of the <int> indicates an ACPI debug layer,
187 1: enable, 0: disable. It is useful for boot time
188 debugging. After system has booted up, it can be set
189 via /sys/module/acpi/parameters/debug_layer.
190 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
191 Available bits (add the numbers together) to enable debug output
192 for specific parts of the ACPI subsystem:
193 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
194 0x10 namespace 0x20 parser 0x40 dispatcher
195 0x80 executer 0x100 resources 0x200 acpica debugger
196 0x400 os services 0x800 acpica disassembler.
197 The number can be in decimal or prefixed with 0x in hex.
198 Warning: Many of these options can produce a lot of
199 output and make your system unusable. Be very careful.
201 acpi.debug_level= [HW,ACPI]
202 Format: <int>
203 Each bit of the <int> indicates an ACPI debug level,
204 1: enable, 0: disable. It is useful for boot time
205 debugging. After system has booted up, it can be set
206 via /sys/module/acpi/parameters/debug_level.
207 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
208 Available bits (add the numbers together) to enable different
209 debug output levels of the ACPI subsystem:
210 0x01 error 0x02 warn 0x04 init 0x08 debug object
211 0x10 info 0x20 init names 0x40 parse 0x80 load
212 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
213 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
214 0x10000 resources 0x20000 user requests 0x40000 package.
215 The number can be in decimal or prefixed with 0x in hex.
216 Warning: Many of these options can produce a lot of
217 output and make your system unusable. Be very careful.
220 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
222 acpi_pm_good [X86-32,X86-64]
223 Override the pmtimer bug detection: force the kernel
224 to assume that this machine's pmtimer latches its value
225 and always returns good values.
227 agp= [AGP]
228 { off | try_unsupported }
229 off: disable AGP support
230 try_unsupported: try to drive unsupported chipsets
231 (may crash computer or cause data corruption)
233 enable_timer_pin_1 [i386,x86-64]
234 Enable PIN 1 of APIC timer
235 Can be useful to work around chipset bugs
236 (in particular on some ATI chipsets).
237 The kernel tries to set a reasonable default.
239 disable_timer_pin_1 [i386,x86-64]
240 Disable PIN 1 of APIC timer
241 Can be useful to work around chipset bugs.
243 ad1848= [HW,OSS]
244 Format: <io>,<irq>,<dma>,<dma2>,<type>
246 advansys= [HW,SCSI]
247 See header of drivers/scsi/advansys.c.
249 advwdt= [HW,WDT] Advantech WDT
250 Format: <iostart>,<iostop>
252 aedsp16= [HW,OSS] Audio Excel DSP 16
253 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
254 See also header of sound/oss/aedsp16.c.
256 aha152x= [HW,SCSI]
257 See Documentation/scsi/aha152x.txt.
259 aha1542= [HW,SCSI]
260 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
262 aic7xxx= [HW,SCSI]
263 See Documentation/scsi/aic7xxx.txt.
265 aic79xx= [HW,SCSI]
266 See Documentation/scsi/aic79xx.txt.
268 amijoy.map= [HW,JOY] Amiga joystick support
269 Map of devices attached to JOY0DAT and JOY1DAT
270 Format: <a>,<b>
271 See also Documentation/kernel/input/joystick.txt
273 analog.map= [HW,JOY] Analog joystick and gamepad support
274 Specifies type or capabilities of an analog joystick
275 connected to one of 16 gameports
276 Format: <type1>,<type2>,..<type16>
278 apc= [HW,SPARC]
279 Power management functions (SPARCstation-4/5 + deriv.)
280 Format: noidle
281 Disable APC CPU standby support. SPARCstation-Fox does
282 not play well with APC CPU idle - disable it if you have
283 APC and your system crashes randomly.
285 apic= [APIC,i386] Advanced Programmable Interrupt Controller
286 Change the output verbosity whilst booting
287 Format: { quiet (default) | verbose | debug }
288 Change the amount of debugging information output
289 when initialising the APIC and IO-APIC components.
291 apm= [APM] Advanced Power Management
292 See header of arch/i386/kernel/apm.c.
294 applicom= [HW]
295 Format: <mem>,<irq>
297 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
298 Format: <io>,<irq>,<nodeID>
300 ataflop= [HW,M68k]
302 atarimouse= [HW,MOUSE] Atari Mouse
304 atascsi= [HW,SCSI] Atari SCSI
306 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
307 EzKey and similar keyboards
309 atkbd.reset= [HW] Reset keyboard during initialization
311 atkbd.set= [HW] Select keyboard code set
312 Format: <int> (2 = AT (default), 3 = PS/2)
314 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
315 keyboards
317 atkbd.softraw= [HW] Choose between synthetic and real raw mode
318 Format: <bool> (0 = real, 1 = synthetic (default))
320 atkbd.softrepeat= [HW]
321 Use software keyboard repeat
323 autotest [IA64]
325 baycom_epp= [HW,AX25]
326 Format: <io>,<mode>
328 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
329 Format: <io>,<mode>
330 See header of drivers/net/hamradio/baycom_par.c.
332 baycom_ser_fdx= [HW,AX25]
333 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
334 Format: <io>,<irq>,<mode>[,<baud>]
335 See header of drivers/net/hamradio/baycom_ser_fdx.c.
337 baycom_ser_hdx= [HW,AX25]
338 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
339 Format: <io>,<irq>,<mode>
340 See header of drivers/net/hamradio/baycom_ser_hdx.c.
342 blkmtd_device= [HW,MTD]
343 blkmtd_erasesz=
344 blkmtd_ro=
345 blkmtd_bs=
346 blkmtd_count=
348 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
349 bttv.radio= Most important insmod options are available as
350 kernel args too.
351 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
352 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
354 BusLogic= [HW,SCSI]
355 See drivers/scsi/BusLogic.c, comment before function
356 BusLogic_ParseDriverOptions().
358 c101= [NET] Moxa C101 synchronous serial card
360 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
361 Sometimes CPU hardware bugs make them report the cache
362 size incorrectly. The kernel will attempt work arounds
363 to fix known problems, but for some CPUs it is not
364 possible to determine what the correct size should be.
365 This option provides an override for these situations.
367 chandev= [HW,NET] Generic channel device initialisation
369 checkreqprot [SELINUX] Set initial checkreqprot flag value.
370 Format: { "0" | "1" }
371 See security/selinux/Kconfig help text.
372 0 -- check protection applied by kernel (includes
373 any implied execute protection).
374 1 -- check protection requested by application.
375 Default value is set via a kernel config option.
376 Value can be changed at runtime via
377 /selinux/checkreqprot.
379 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
380 [Deprecated]
381 Forces specified clocksource (if available) to be used
382 when calculating gettimeofday(). If specified
383 clocksource is not available, it defaults to PIT.
384 Format: { pit | tsc | cyclone | pmtmr }
386 clocksource= [GENERIC_TIME] Override the default clocksource
387 Format: <string>
388 Override the default clocksource and use the clocksource
389 with the name specified.
390 Some clocksource names to choose from, depending on
391 the platform:
392 [all] jiffies (this is the base, fallback clocksource)
393 [ACPI] acpi_pm
394 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
395 pxa_timer,timer3,32k_counter,timer0_1
396 [AVR32] avr32
397 [X86-32] pit,hpet,tsc,vmi-timer;
398 scx200_hrt on Geode; cyclone on IBM x440
399 [MIPS] MIPS
400 [PARISC] cr16
401 [S390] tod
402 [SH] SuperH
403 [SPARC64] tick
404 [X86-64] hpet,tsc
406 code_bytes [IA32] How many bytes of object code to print in an
407 oops report.
408 Range: 0 - 8192
409 Default: 64
411 disable_8254_timer
412 enable_8254_timer
413 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
414 over the 8254 in addition to over the IO-APIC. The
415 kernel tries to set a sensible default.
417 hpet= [X86-32,HPET] option to disable HPET and use PIT.
418 Format: disable
420 com20020= [HW,NET] ARCnet - COM20020 chipset
421 Format:
422 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
424 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
425 Format: <io>[,<irq>]
427 com90xx= [HW,NET]
428 ARCnet - COM90xx chipset (memory-mapped buffers)
429 Format: <io>[,<irq>[,<memstart>]]
431 condev= [HW,S390] console device
432 conmode=
434 console= [KNL] Output console device and options.
436 tty<n> Use the virtual console device <n>.
438 ttyS<n>[,options]
439 ttyUSB0[,options]
440 Use the specified serial port. The options are of
441 the form "bbbbpnf", where "bbbb" is the baud rate,
442 "p" is parity ("n", "o", or "e"), "n" is number of
443 bits, and "f" is flow control ("r" for RTS or
444 omit it). Default is "9600n8".
446 See Documentation/serial-console.txt for more
447 information. See
448 Documentation/networking/netconsole.txt for an
449 alternative.
451 uart[8250],io,<addr>[,options]
452 uart[8250],mmio,<addr>[,options]
453 Start an early, polled-mode console on the 8250/16550
454 UART at the specified I/O port or MMIO address,
455 switching to the matching ttyS device later. The
456 options are the same as for ttyS, above.
458 earlycon= [KNL] Output early console device and options.
459 uart[8250],io,<addr>[,options]
460 uart[8250],mmio,<addr>[,options]
461 Start an early, polled-mode console on the 8250/16550
462 UART at the specified I/O port or MMIO address.
463 The options are the same as for ttyS, above.
465 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
466 Format:
467 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
469 cpia_pp= [HW,PPT]
470 Format: { parport<nr> | auto | none }
472 crashkernel=nn[KMG]@ss[KMG]
473 [KNL] Reserve a chunk of physical memory to
474 hold a kernel to switch to with kexec on panic.
476 cs4232= [HW,OSS]
477 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
479 cs89x0_dma= [HW,NET]
480 Format: <dma>
482 cs89x0_media= [HW,NET]
483 Format: { rj45 | aui | bnc }
485 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
487 dasd= [HW,NET]
488 See header of drivers/s390/block/dasd_devmap.c.
490 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
491 (one device per port)
492 Format: <port#>,<type>
493 See also Documentation/input/joystick-parport.txt
495 debug [KNL] Enable kernel debugging (events log level).
497 debug_locks_verbose=
498 [KNL] verbose self-tests
499 Format=<0|1>
500 Print debugging info while doing the locking API
501 self-tests.
502 We default to 0 (no extra messages), setting it to
503 1 will print _a lot_ more information - normally
504 only useful to kernel developers.
506 decnet= [HW,NET]
507 Format: <area>[,<node>]
508 See also Documentation/networking/decnet.txt.
510 default_blu= [VT]
511 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
512 Change the default blue palette of the console.
513 This is a 16-member array composed of values
514 ranging from 0-255.
516 default_grn= [VT]
517 Format: <green0>,<green1>,<green2>,...,<green15>
518 Change the default green palette of the console.
519 This is a 16-member array composed of values
520 ranging from 0-255.
522 default_red= [VT]
523 Format: <red0>,<red1>,<red2>,...,<red15>
524 Change the default red palette of the console.
525 This is a 16-member array composed of values
526 ranging from 0-255.
528 default_utf8= [VT]
529 Format=<0|1>
530 Set system-wide default UTF-8 mode for all tty's.
531 Default is 0 and by setting to 1, it enables UTF-8
532 mode for all newly opened or allocated terminals.
534 dhash_entries= [KNL]
535 Set number of hash buckets for dentry cache.
537 digi= [HW,SERIAL]
538 IO parameters + enable/disable command.
540 digiepca= [HW,SERIAL]
541 See drivers/char/README.epca and
542 Documentation/digiepca.txt.
544 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
545 support available.
546 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
548 dmasound= [HW,OSS] Sound subsystem buffers
550 dscc4.setup= [NET]
552 dtc3181e= [HW,SCSI]
554 earlyprintk= [X86-32,X86-64,SH]
555 earlyprintk=vga
556 earlyprintk=serial[,ttySn[,baudrate]]
558 Append ",keep" to not disable it when the real console
559 takes over.
561 Only vga or serial at a time, not both.
563 Currently only ttyS0 and ttyS1 are supported.
565 Interaction with the standard serial driver is not
566 very good.
568 The VGA output is eventually overwritten by the real
569 console.
571 eata= [HW,SCSI]
573 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
574 Format: <int>
575 0: polling mode
576 non-0: interrupt mode (default)
578 eda= [HW,PS2]
580 edb= [HW,PS2]
582 edd= [EDD]
583 Format: {"of[f]" | "sk[ipmbr]"}
584 See comment in arch/i386/boot/edd.S
586 eicon= [HW,ISDN]
587 Format: <id>,<membase>,<irq>
589 eisa_irq_edge= [PARISC,HW]
590 See header of drivers/parisc/eisa.c.
592 elanfreq= [X86-32]
593 See comment before function elanfreq_setup() in
594 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
596 elevator= [IOSCHED]
597 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
598 See Documentation/block/as-iosched.txt and
599 Documentation/block/deadline-iosched.txt for details.
601 elfcorehdr= [X86-32, X86_64]
602 Specifies physical address of start of kernel core
603 image elf header. Generally kexec loader will
604 pass this option to capture kernel.
605 See Documentation/kdump/kdump.txt for details.
607 enforcing [SELINUX] Set initial enforcing status.
608 Format: {"0" | "1"}
609 See security/selinux/Kconfig help text.
610 0 -- permissive (log only, no denials).
611 1 -- enforcing (deny and log).
612 Default value is 0.
613 Value can be changed at runtime via /selinux/enforce.
615 es1371= [HW,OSS]
616 Format: <spdif>,[<nomix>,[<amplifier>]]
617 See also header of sound/oss/es1371.c.
619 ether= [HW,NET] Ethernet cards parameters
620 This option is obsoleted by the "netdev=" option, which
621 has equivalent usage. See its documentation for details.
623 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
624 Format: <io>[,<irq>]
626 failslab=
627 fail_page_alloc=
628 fail_make_request=[KNL]
629 General fault injection mechanism.
630 Format: <interval>,<probability>,<space>,<times>
631 See also /Documentation/fault-injection/.
633 fd_mcs= [HW,SCSI]
634 See header of drivers/scsi/fd_mcs.c.
636 fdomain= [HW,SCSI]
637 See header of drivers/scsi/fdomain.c.
639 floppy= [HW]
640 See Documentation/floppy.txt.
642 gamecon.map[2|3]=
643 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
644 support via parallel port (up to 5 devices per port)
645 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
646 See also Documentation/input/joystick-parport.txt
648 gamma= [HW,DRM]
650 gdth= [HW,SCSI]
651 See header of drivers/scsi/gdth.c.
653 gpt [EFI] Forces disk with valid GPT signature but
654 invalid Protective MBR to be treated as GPT.
656 gvp11= [HW,SCSI]
658 hashdist= [KNL,NUMA] Large hashes allocated during boot
659 are distributed across NUMA nodes. Defaults on
660 for IA-64, off otherwise.
661 Format: 0 | 1 (for off | on)
663 hcl= [IA-64] SGI's Hardware Graph compatibility layer
665 hd= [EIDE] (E)IDE hard drive subsystem geometry
666 Format: <cyl>,<head>,<sect>
668 hd?= [HW] (E)IDE subsystem
669 hd?lun= See Documentation/ide.txt.
671 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
672 size of <nn>. This works even on boxes that have no
673 highmem otherwise. This also works to reduce highmem
674 size on bigger boxes.
676 highres= [KNL] Enable/disable high resolution timer mode.
677 Valid parameters: "on", "off"
678 Default: "on"
680 hisax= [HW,ISDN]
681 See Documentation/isdn/README.HiSax.
683 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
685 i8042.direct [HW] Put keyboard port into non-translated mode
686 i8042.dumbkbd [HW] Pretend that controller can only read data from
687 keyboard and cannot control its state
688 (Don't attempt to blink the leds)
689 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
690 i8042.nokbd [HW] Don't check/create keyboard port
691 i8042.nomux [HW] Don't check presence of an active multiplexing
692 controller
693 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
694 controllers
695 i8042.panicblink=
696 [HW] Frequency with which keyboard LEDs should blink
697 when kernel panics (default is 0.5 sec)
698 i8042.reset [HW] Reset the controller during init and cleanup
699 i8042.unlock [HW] Unlock (ignore) the keylock
701 i810= [HW,DRM]
703 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
704 indicates that the driver is running on unsupported
705 hardware.
706 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
707 does not match list of supported models.
708 i8k.power_status
709 [HW] Report power status in /proc/i8k
710 (disabled by default)
711 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
712 capability is set.
714 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
715 See Documentation/mca.txt.
717 icn= [HW,ISDN]
718 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
720 ide= [HW] (E)IDE subsystem
721 Format: ide=nodma or ide=doubler or ide=reverse
722 See Documentation/ide.txt.
724 ide?= [HW] (E)IDE subsystem
725 Format: ide?=noprobe or chipset specific parameters.
726 See Documentation/ide.txt.
728 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
729 See Documentation/ide.txt.
731 idle= [X86]
732 Format: idle=poll or idle=mwait
733 Poll forces a polling idle loop that can slightly improves the performance
734 of waking up a idle CPU, but will use a lot of power and make the system
735 run hot. Not recommended.
736 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
737 to not use it because it doesn't save as much power as a normal idle
738 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
739 as idle=poll.
741 ignore_loglevel [KNL]
742 Ignore loglevel setting - this will print /all/
743 kernel messages to the console. Useful for debugging.
745 ihash_entries= [KNL]
746 Set number of hash buckets for inode cache.
748 in2000= [HW,SCSI]
749 See header of drivers/scsi/in2000.c.
751 init= [KNL]
752 Format: <full_path>
753 Run specified binary instead of /sbin/init as init
754 process.
756 initcall_debug [KNL] Trace initcalls as they are executed. Useful
757 for working out where the kernel is dying during
758 startup.
760 initrd= [BOOT] Specify the location of the initial ramdisk
762 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
763 Format: <irq>
765 inttest= [IA64]
767 io7= [HW] IO7 for Marvel based alpha systems
768 See comment before marvel_specify_io7 in
769 arch/alpha/kernel/core_marvel.c.
771 ip= [IP_PNP]
772 See Documentation/nfsroot.txt.
774 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
775 See comment before ip2_setup() in
776 drivers/char/ip2/ip2base.c.
778 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
779 See header of drivers/scsi/ips.c.
781 ports= [IP_VS_FTP] IPVS ftp helper module
782 Default is 21.
783 Up to 8 (IP_VS_APP_MAX_PORTS) ports
784 may be specified.
785 Format: <port>,<port>....
787 irqfixup [HW]
788 When an interrupt is not handled search all handlers
789 for it. Intended to get systems with badly broken
790 firmware running.
792 irqpoll [HW]
793 When an interrupt is not handled search all handlers
794 for it. Also check all handlers each timer
795 interrupt. Intended to get systems with badly broken
796 firmware running.
798 isapnp= [ISAPNP]
799 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
801 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
802 Format:
803 <cpu number>,...,<cpu number>
804 or
805 <cpu number>-<cpu number> (must be a positive range in ascending order)
806 or a mixture
807 <cpu number>,...,<cpu number>-<cpu number>
808 This option can be used to specify one or more CPUs
809 to isolate from the general SMP balancing and scheduling
810 algorithms. The only way to move a process onto or off
811 an "isolated" CPU is via the CPU affinity syscalls.
812 <cpu number> begins at 0 and the maximum value is
813 "number of CPUs in system - 1".
815 This option is the preferred way to isolate CPUs. The
816 alternative -- manually setting the CPU mask of all
817 tasks in the system -- can cause problems and
818 suboptimal load balancer performance.
820 iucv= [HW,NET]
822 js= [HW,JOY] Analog joystick
823 See Documentation/input/joystick.txt.
825 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
826 specifies the amount of memory usable by the kernel
827 for non-movable allocations. The requested amount is
828 spread evenly throughout all nodes in the system. The
829 remaining memory in each node is used for Movable
830 pages. In the event, a node is too small to have both
831 kernelcore and Movable pages, kernelcore pages will
832 take priority and other nodes will have a larger number
833 of kernelcore pages. The Movable zone is used for the
834 allocation of pages that may be reclaimed or moved
835 by the page migration subsystem. This means that
836 HugeTLB pages may not be allocated from this zone.
837 Note that allocations like PTEs-from-HighMem still
838 use the HighMem zone if it exists, and the Normal
839 zone if it does not.
841 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
842 is similar to kernelcore except it specifies the
843 amount of memory used for migratable allocations.
844 If both kernelcore and movablecore is specified,
845 then kernelcore will be at *least* the specified
846 value but may be more. If movablecore on its own
847 is specified, the administrator must be careful
848 that the amount of memory usable for all allocations
849 is not too small.
851 keepinitrd [HW,ARM]
853 kstack=N [X86-32,X86-64] Print N words from the kernel stack
854 in oops dumps.
856 l2cr= [PPC]
858 lapic [X86-32,APIC] Enable the local APIC even if BIOS
859 disabled it.
861 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
862 C2 power state.
864 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
865 Format: addr:<io>,irq:<irq>
867 load_ramdisk= [RAM] List of ramdisks to load from floppy
868 See Documentation/ramdisk.txt.
870 lockd.nlm_grace_period=P [NFS] Assign grace period.
871 Format: <integer>
873 lockd.nlm_tcpport=N [NFS] Assign TCP port.
874 Format: <integer>
876 lockd.nlm_timeout=T [NFS] Assign timeout value.
877 Format: <integer>
879 lockd.nlm_udpport=M [NFS] Assign UDP port.
880 Format: <integer>
882 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
883 Format: <irq>
885 loglevel= All Kernel Messages with a loglevel smaller than the
886 console loglevel will be printed to the console. It can
887 also be changed with klogd or other programs. The
888 loglevels are defined as follows:
890 0 (KERN_EMERG) system is unusable
891 1 (KERN_ALERT) action must be taken immediately
892 2 (KERN_CRIT) critical conditions
893 3 (KERN_ERR) error conditions
894 4 (KERN_WARNING) warning conditions
895 5 (KERN_NOTICE) normal but significant condition
896 6 (KERN_INFO) informational
897 7 (KERN_DEBUG) debug-level messages
899 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
900 Format: { n | nk | nM }
901 n must be a power of two. The default size
902 is set in the kernel config file.
904 lp=0 [LP] Specify parallel ports to use, e.g,
905 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
906 lp=reset first parallel port). 'lp=0' disables the
907 lp=auto printer driver. 'lp=reset' (which can be
908 specified in addition to the ports) causes
909 attached printers to be reset. Using
910 lp=port1,port2,... specifies the parallel ports
911 to associate lp devices with, starting with
912 lp0. A port specification may be 'none' to skip
913 that lp device, or a parport name such as
914 'parport0'. Specifying 'lp=auto' instead of a
915 port specification list means that device IDs
916 from each port should be examined, to see if
917 an IEEE 1284-compliant printer is attached; if
918 so, the driver will manage that printer.
919 See also header of drivers/char/lp.c.
921 lpj=n [KNL]
922 Sets loops_per_jiffy to given constant, thus avoiding
923 time-consuming boot-time autodetection (up to 250 ms per
924 CPU). 0 enables autodetection (default). To determine
925 the correct value for your kernel, boot with normal
926 autodetection and see what value is printed. Note that
927 on SMP systems the preset will be applied to all CPUs,
928 which is likely to cause problems if your CPUs need
929 significantly divergent settings. An incorrect value
930 will cause delays in the kernel to be wrong, leading to
931 unpredictable I/O errors and other breakage. Although
932 unlikely, in the extreme case this might damage your
933 hardware.
935 ltpc= [NET]
936 Format: <io>,<irq>,<dma>
938 mac5380= [HW,SCSI] Format:
939 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
941 mac53c9x= [HW,SCSI] Format:
942 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
944 machvec= [IA64] Force the use of a particular machine-vector
945 (machvec) in a generic kernel.
946 Example: machvec=hpzx1_swiotlb
948 max_loop= [LOOP] Maximum number of loopback devices that can
949 be mounted
950 Format: <1-256>
952 maxcpus= [SMP] Maximum number of processors that an SMP kernel
953 should make use of.
954 Using "nosmp" or "maxcpus=0" will disable SMP
955 entirely (the MPS table probe still happens, though).
956 A command-line option of "maxcpus=<NUM>", where <NUM>
957 is an integer greater than 0, limits the maximum number
958 of CPUs activated in SMP mode to <NUM>.
959 Using "maxcpus=1" on an SMP kernel is the trivial
960 case of an SMP kernel with only one CPU.
962 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
963 equal to this physical address is ignored.
965 max_luns= [SCSI] Maximum number of LUNs to probe.
966 Should be between 1 and 2^32-1.
968 max_report_luns=
969 [SCSI] Maximum number of LUNs received.
970 Should be between 1 and 16384.
972 mca-pentium [BUGS=X86-32]
974 mcatest= [IA-64]
976 mce [X86-32] Machine Check Exception
978 md= [HW] RAID subsystems devices and level
979 See Documentation/md.txt.
981 mdacon= [MDA]
982 Format: <first>,<last>
983 Specifies range of consoles to be captured by the MDA.
985 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
986 Amount of memory to be used when the kernel is not able
987 to see the whole system memory or for test.
988 [X86-32] Use together with memmap= to avoid physical
989 address space collisions. Without memmap= PCI devices
990 could be placed at addresses belonging to unused RAM.
992 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
993 memory.
995 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
996 E820 memory map, as specified by the user.
997 Such memmap=exactmap lines can be constructed based on
998 BIOS output or other requirements. See the memmap=nn@ss
999 option description.
1001 memmap=nn[KMG]@ss[KMG]
1002 [KNL] Force usage of a specific region of memory
1003 Region of memory to be used, from ss to ss+nn.
1005 memmap=nn[KMG]#ss[KMG]
1006 [KNL,ACPI] Mark specific memory as ACPI data.
1007 Region of memory to be used, from ss to ss+nn.
1009 memmap=nn[KMG]$ss[KMG]
1010 [KNL,ACPI] Mark specific memory as reserved.
1011 Region of memory to be used, from ss to ss+nn.
1013 meye.*= [HW] Set MotionEye Camera parameters
1014 See Documentation/video4linux/meye.txt.
1016 mga= [HW,DRM]
1018 mousedev.tap_time=
1019 [MOUSE] Maximum time between finger touching and
1020 leaving touchpad surface for touch to be considered
1021 a tap and be reported as a left button click (for
1022 touchpads working in absolute mode only).
1023 Format: <msecs>
1024 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1025 reporting absolute coordinates, such as tablets
1026 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1027 reporting absolute coordinates, such as tablets
1029 mpu401= [HW,OSS]
1030 Format: <io>,<irq>
1032 MTD_Partition= [MTD]
1033 Format: <name>,<region-number>,<size>,<offset>
1035 MTD_Region= [MTD] Format:
1036 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1038 mtdparts= [MTD]
1039 See drivers/mtd/cmdlinepart.c.
1041 mtouchusb.raw_coordinates=
1042 [HW] Make the MicroTouch USB driver use raw coordinates
1043 ('y', default) or cooked coordinates ('n')
1045 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1047 NCR_D700= [HW,SCSI]
1048 See header of drivers/scsi/NCR_D700.c.
1050 ncr5380= [HW,SCSI]
1052 ncr53c400= [HW,SCSI]
1054 ncr53c400a= [HW,SCSI]
1056 ncr53c406a= [HW,SCSI]
1058 ncr53c8xx= [HW,SCSI]
1060 netdev= [NET] Network devices parameters
1061 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1062 Note that mem_start is often overloaded to mean
1063 something different and driver-specific.
1064 This usage is only documented in each driver source
1065 file if at all.
1067 nfsaddrs= [NFS]
1068 See Documentation/nfsroot.txt.
1070 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1071 See Documentation/nfsroot.txt.
1073 nfs.callback_tcpport=
1074 [NFS] set the TCP port on which the NFSv4 callback
1075 channel should listen.
1077 nfs.idmap_cache_timeout=
1078 [NFS] set the maximum lifetime for idmapper cache
1079 entries.
1081 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1083 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1084 emulation library even if a 387 maths coprocessor
1085 is present.
1087 noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1088 when set.
1089 Format: <int>
1091 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1092 caches in the slab allocator. Saves per-node memory,
1093 but will impact performance.
1095 noalign [KNL,ARM]
1097 noapic [SMP,APIC] Tells the kernel to not make use of any
1098 IOAPICs that may be present in the system.
1100 noasync [HW,M68K] Disables async and sync negotiation for
1101 all devices.
1103 nobats [PPC] Do not use BATs for mapping kernel lowmem
1104 on "Classic" PPC cores.
1106 nocache [ARM]
1108 nodelayacct [KNL] Disable per-task delay accounting
1110 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1112 noexec [IA-64]
1114 noexec [X86-32,X86-64]
1115 noexec=on: enable non-executable mappings (default)
1116 noexec=off: disable nn-executable mappings
1118 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1119 register save and restore. The kernel will only save
1120 legacy floating-point registers on task switch.
1122 nohlt [BUGS=ARM]
1124 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1125 instruction doesn't work correctly and not to
1126 use it.
1128 nohalt [IA-64] Tells the kernel not to use the power saving
1129 function PAL_HALT_LIGHT when idle. This increases
1130 power-consumption. On the positive side, it reduces
1131 interrupt wake-up latency, which may improve performance
1132 in certain environments such as networked servers or
1133 real-time systems.
1135 nohz= [KNL] Boottime enable/disable dynamic ticks
1136 Valid arguments: on, off
1137 Default: on
1139 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1141 noirqdebug [X86-32] Disables the code which attempts to detect and
1142 disable unhandled interrupt sources.
1144 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1145 broken timer IRQ sources.
1147 noisapnp [ISAPNP] Disables ISA PnP code.
1149 noinitrd [RAM] Tells the kernel not to load any configured
1150 initial RAM disk.
1152 nointroute [IA-64]
1154 nojitter [IA64] Disables jitter checking for ITC timers.
1156 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1158 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1160 noltlbs [PPC] Do not use large page/tlb entries for kernel
1161 lowmem mapping on PPC40x.
1163 nomca [IA-64] Disable machine check abort handling
1165 nomce [X86-32] Machine Check Exception
1167 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1169 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1170 with UP alternatives
1172 noresidual [PPC] Don't use residual data on PReP machines.
1174 noresume [SWSUSP] Disables resume and restores original swap
1175 space.
1177 no-scroll [VGA] Disables scrollback.
1178 This is required for the Braillex ib80-piezo Braille
1179 reader made by F.H. Papenmeier (Germany).
1181 nosbagart [IA-64]
1183 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1185 nosmp [SMP] Tells an SMP kernel to act as a UP kernel.
1187 nosoftlockup [KNL] Disable the soft-lockup detector.
1189 nosync [HW,M68K] Disables sync negotiation for all devices.
1191 notsc [BUGS=X86-32] Disable Time Stamp Counter
1193 nousb [USB] Disable the USB subsystem
1195 nowb [ARM]
1197 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1198 one of ['zone', 'node', 'default'] can be specified
1199 This can be set from sysctl after boot.
1200 See Documentation/sysctl/vm.txt for details.
1202 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1204 opl3= [HW,OSS]
1205 Format: <io>
1207 oprofile.timer= [HW]
1208 Use timer interrupt instead of performance counters
1210 osst= [HW,SCSI] SCSI Tape Driver
1211 Format: <buffer_size>,<write_threshold>
1212 See also Documentation/scsi/st.txt.
1214 panic= [KNL] Kernel behaviour on panic
1215 Format: <timeout>
1217 parkbd.port= [HW] Parallel port number the keyboard adapter is
1218 connected to, default is 0.
1219 Format: <parport#>
1220 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1221 0 for XT, 1 for AT (default is AT).
1222 Format: <mode>
1224 parport= [HW,PPT] Specify parallel ports. 0 disables.
1225 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1226 Use 'auto' to force the driver to use any
1227 IRQ/DMA settings detected (the default is to
1228 ignore detected IRQ/DMA settings because of
1229 possible conflicts). You can specify the base
1230 address, IRQ, and DMA settings; IRQ and DMA
1231 should be numbers, or 'auto' (for using detected
1232 settings on that particular port), or 'nofifo'
1233 (to avoid using a FIFO even if it is detected).
1234 Parallel ports are assigned in the order they
1235 are specified on the command line, starting
1236 with parport0.
1238 parport_init_mode= [HW,PPT]
1239 Configure VIA parallel port to operate in
1240 a specific mode. This is necessary on Pegasos
1241 computer where firmware has no options for setting
1242 up parallel port mode and sets it to spp.
1243 Currently this function knows 686a and 8231 chips.
1244 Format: [spp|ps2|epp|ecp|ecpepp]
1246 pas2= [HW,OSS] Format:
1247 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1249 pas16= [HW,SCSI]
1250 See header of drivers/scsi/pas16.c.
1252 pause_on_oops=
1253 Halt all CPUs after the first oops has been printed for
1254 the specified number of seconds. This is to be used if
1255 your oopses keep scrolling off the screen.
1257 pcbit= [HW,ISDN]
1259 pcd. [PARIDE]
1260 See header of drivers/block/paride/pcd.c.
1261 See also Documentation/paride.txt.
1263 pci=option[,option...] [PCI] various PCI subsystem options:
1264 off [X86-32] don't probe for the PCI bus
1265 bios [X86-32] force use of PCI BIOS, don't access
1266 the hardware directly. Use this if your machine
1267 has a non-standard PCI host bridge.
1268 nobios [X86-32] disallow use of PCI BIOS, only direct
1269 hardware access methods are allowed. Use this
1270 if you experience crashes upon bootup and you
1271 suspect they are caused by the BIOS.
1272 conf1 [X86-32] Force use of PCI Configuration
1273 Mechanism 1.
1274 conf2 [X86-32] Force use of PCI Configuration
1275 Mechanism 2.
1276 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1277 Configuration
1278 nomsi [MSI] If the PCI_MSI kernel config parameter is
1279 enabled, this kernel boot option can be used to
1280 disable the use of MSI interrupts system-wide.
1281 nosort [X86-32] Don't sort PCI devices according to
1282 order given by the PCI BIOS. This sorting is
1283 done to get a device order compatible with
1284 older kernels.
1285 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1286 routing table. These calls are known to be buggy
1287 on several machines and they hang the machine
1288 when used, but on other computers it's the only
1289 way to get the interrupt routing table. Try
1290 this option if the kernel is unable to allocate
1291 IRQs or discover secondary PCI buses on your
1292 motherboard.
1293 rom [X86-32] Assign address space to expansion ROMs.
1294 Use with caution as certain devices share
1295 address decoders between ROMs and other
1296 resources.
1297 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1298 assigned automatically to PCI devices. You can
1299 make the kernel exclude IRQs of your ISA cards
1300 this way.
1301 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1302 of the PIRQ table (normally generated
1303 by the BIOS) if it is outside the
1304 F0000h-100000h range.
1305 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1306 useful if the kernel is unable to find your
1307 secondary buses and you want to tell it
1308 explicitly which ones they are.
1309 assign-busses [X86-32] Always assign all PCI bus
1310 numbers ourselves, overriding
1311 whatever the firmware may have done.
1312 usepirqmask [X86-32] Honor the possible IRQ mask stored
1313 in the BIOS $PIR table. This is needed on
1314 some systems with broken BIOSes, notably
1315 some HP Pavilion N5400 and Omnibook XE3
1316 notebooks. This will have no effect if ACPI
1317 IRQ routing is enabled.
1318 noacpi [X86-32] Do not use ACPI for IRQ routing
1319 or for PCI scanning.
1320 routeirq Do IRQ routing for all PCI devices.
1321 This is normally done in pci_enable_device(),
1322 so this option is a temporary workaround
1323 for broken drivers that don't call it.
1324 firmware [ARM] Do not re-enumerate the bus but instead
1325 just use the configuration from the
1326 bootloader. This is currently used on
1327 IXP2000 systems where the bus has to be
1328 configured a certain way for adjunct CPUs.
1329 noearly [X86] Don't do any early type 1 scanning.
1330 This might help on some broken boards which
1331 machine check when some devices' config space
1332 is read. But various workarounds are disabled
1333 and some IOMMU drivers will not work.
1334 bfsort Sort PCI devices into breadth-first order.
1335 This sorting is done to get a device
1336 order compatible with older (<= 2.4) kernels.
1337 nobfsort Don't sort PCI devices into breadth-first order.
1338 cbiosize=nn[KMG] The fixed amount of bus space which is
1339 reserved for the CardBus bridge's IO window.
1340 The default value is 256 bytes.
1341 cbmemsize=nn[KMG] The fixed amount of bus space which is
1342 reserved for the CardBus bridge's memory
1343 window. The default value is 64 megabytes.
1345 pcmv= [HW,PCMCIA] BadgePAD 4
1347 pd. [PARIDE]
1348 See Documentation/paride.txt.
1350 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1351 boot time.
1352 Format: { 0 | 1 }
1353 See arch/parisc/kernel/pdc_chassis.c
1355 pf. [PARIDE]
1356 See Documentation/paride.txt.
1358 pg. [PARIDE]
1359 See Documentation/paride.txt.
1361 pirq= [SMP,APIC] Manual mp-table setup
1362 See Documentation/i386/IO-APIC.txt.
1364 plip= [PPT,NET] Parallel port network link
1365 Format: { parport<nr> | timid | 0 }
1366 See also Documentation/parport.txt.
1368 pnpacpi= [ACPI]
1369 { off }
1371 pnpbios= [ISAPNP]
1372 { on | off | curr | res | no-curr | no-res }
1374 pnp_reserve_irq=
1375 [ISAPNP] Exclude IRQs for the autoconfiguration
1377 pnp_reserve_dma=
1378 [ISAPNP] Exclude DMAs for the autoconfiguration
1380 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1381 Ranges are in pairs (I/O port base and size).
1383 pnp_reserve_mem=
1384 [ISAPNP] Exclude memory regions for the
1385 autoconfiguration.
1386 Ranges are in pairs (memory base and size).
1388 print-fatal-signals=
1389 [KNL] debug: print fatal signals
1390 print-fatal-signals=1: print segfault info to
1391 the kernel console.
1392 default: off.
1394 printk.time= Show timing data prefixed to each printk message line
1395 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1397 profile= [KNL] Enable kernel profiling via /proc/profile
1398 Format: [schedule,]<number>
1399 Param: "schedule" - profile schedule points.
1400 Param: <number> - step/bucket size as a power of 2 for
1401 statistical time based profiling.
1402 Param: "sleep" - profile D-state sleeping (millisecs)
1404 processor.max_cstate= [HW,ACPI]
1405 Limit processor to maximum C-state
1406 max_cstate=9 overrides any DMI blacklist limit.
1408 processor.nocst [HW,ACPI]
1409 Ignore the _CST method to determine C-states,
1410 instead using the legacy FADT method
1412 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1413 before loading.
1414 See Documentation/ramdisk.txt.
1416 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1417 probe for; one of (bare|imps|exps|lifebook|any).
1418 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1419 per second.
1420 psmouse.resetafter= [HW,MOUSE]
1421 Try to reset the device after so many bad packets
1422 (0 = never).
1423 psmouse.resolution=
1424 [HW,MOUSE] Set desired mouse resolution, in dpi.
1425 psmouse.smartscroll=
1426 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1427 0 = disabled, 1 = enabled (default).
1429 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1430 Format:
1431 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1433 pt. [PARIDE]
1434 See Documentation/paride.txt.
1436 quiet [KNL] Disable most log messages
1438 r128= [HW,DRM]
1440 raid= [HW,RAID]
1441 See Documentation/md.txt.
1443 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1444 See Documentation/ramdisk.txt.
1446 ramdisk_blocksize= [RAM]
1447 See Documentation/ramdisk.txt.
1449 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1450 New name for the ramdisk parameter.
1451 See Documentation/ramdisk.txt.
1453 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1454 RCU callbacks to process in one batch.
1456 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1457 RCU callbacks over which batch limiting is disabled.
1459 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1460 RCU callbacks below which batch limiting is re-enabled.
1462 rdinit= [KNL]
1463 Format: <full_path>
1464 Run specified binary instead of /init from the ramdisk,
1465 used for early userspace startup. See initrd.
1467 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1468 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1469 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1471 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1473 reservetop= [X86-32]
1474 Format: nn[KMG]
1475 Reserves a hole at the top of the kernel virtual
1476 address space.
1478 reset_devices [KNL] Force drivers to reset the underlying device
1479 during initialization.
1481 resume= [SWSUSP]
1482 Specify the partition device for software suspend
1484 resume_offset= [SWSUSP]
1485 Specify the offset from the beginning of the partition
1486 given by "resume=" at which the swap header is located,
1487 in <PAGE_SIZE> units (needed only for swap files).
1488 See Documentation/power/swsusp-and-swap-files.txt
1490 retain_initrd [RAM] Keep initrd memory after extraction
1492 rhash_entries= [KNL,NET]
1493 Set number of hash buckets for route cache
1495 riscom8= [HW,SERIAL]
1496 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1498 ro [KNL] Mount root device read-only on boot
1500 root= [KNL] Root filesystem
1502 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1503 mount the root filesystem
1505 rootflags= [KNL] Set root filesystem mount option string
1507 rootfstype= [KNL] Set root filesystem type
1509 rootwait [KNL] Wait (indefinitely) for root device to show up.
1510 Useful for devices that are detected asynchronously
1511 (e.g. USB and MMC devices).
1513 rw [KNL] Mount root device read-write on boot
1515 S [KNL] Run init in single mode
1517 sa1100ir [NET]
1518 See drivers/net/irda/sa1100_ir.c.
1520 sb= [HW,OSS]
1521 Format: <io>,<irq>,<dma>,<dma2>
1523 sbni= [NET] Granch SBNI12 leased line adapter
1525 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1526 Format: <io>[,<timeout>[,<isapnp>]]
1528 scsi_debug_*= [SCSI]
1529 See drivers/scsi/scsi_debug.c.
1531 scsi_default_dev_flags=
1532 [SCSI] SCSI default device flags
1533 Format: <integer>
1535 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1536 Format: <vendor>:<model>:<flags>
1537 (flags are integer value)
1539 scsi_logging= [SCSI]
1541 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1542 discovered. async scans them in kernel threads,
1543 allowing boot to proceed. none ignores them, expecting
1544 user space to do the scan.
1546 selinux [SELINUX] Disable or enable SELinux at boot time.
1547 Format: { "0" | "1" }
1548 See security/selinux/Kconfig help text.
1549 0 -- disable.
1550 1 -- enable.
1551 Default value is set via kernel config option.
1552 If enabled at boot time, /selinux/disable can be used
1553 later to disable prior to initial policy load.
1555 selinux_compat_net =
1556 [SELINUX] Set initial selinux_compat_net flag value.
1557 Format: { "0" | "1" }
1558 0 -- use new secmark-based packet controls
1559 1 -- use legacy packet controls
1560 Default value is 0 (preferred).
1561 Value can be changed at runtime via
1562 /selinux/compat_net.
1564 serialnumber [BUGS=X86-32]
1566 sg_def_reserved_size= [SCSI]
1568 shapers= [NET]
1569 Maximal number of shapers.
1571 sim710= [SCSI,HW]
1572 See header of drivers/scsi/sim710.c.
1574 simeth= [IA-64]
1575 simscsi=
1577 slram= [HW,MTD]
1579 slub_debug[=options[,slabs]] [MM, SLUB]
1580 Enabling slub_debug allows one to determine the
1581 culprit if slab objects become corrupted. Enabling
1582 slub_debug can create guard zones around objects and
1583 may poison objects when not in use. Also tracks the
1584 last alloc / free. For more information see
1585 Documentation/vm/slub.txt.
1587 slub_max_order= [MM, SLUB]
1588 Determines the maximum allowed order for slabs.
1589 A high setting may cause OOMs due to memory
1590 fragmentation. For more information see
1591 Documentation/vm/slub.txt.
1593 slub_min_objects= [MM, SLUB]
1594 The minimum number of objects per slab. SLUB will
1595 increase the slab order up to slub_max_order to
1596 generate a sufficiently large slab able to contain
1597 the number of objects indicated. The higher the number
1598 of objects the smaller the overhead of tracking slabs
1599 and the less frequently locks need to be acquired.
1600 For more information see Documentation/vm/slub.txt.
1602 slub_min_order= [MM, SLUB]
1603 Determines the mininum page order for slabs. Must be
1604 lower than slub_max_order.
1605 For more information see Documentation/vm/slub.txt.
1607 slub_nomerge [MM, SLUB]
1608 Disable merging of slabs with similar size. May be
1609 necessary if there is some reason to distinguish
1610 allocs to different slabs. Debug options disable
1611 merging on their own.
1612 For more information see Documentation/vm/slub.txt.
1614 smart2= [HW]
1615 Format: <io1>[,<io2>[,...,<io8>]]
1617 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1618 attempt to substitute SMP alternatives once at boot.
1620 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1621 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1622 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1623 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1624 smsc-ircc2.ircc_irq= [HW] IRQ line
1625 smsc-ircc2.ircc_dma= [HW] DMA channel
1626 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1627 0: Toshiba Satellite 1800 (GP data pin select)
1628 1: Fast pin select (default)
1629 2: ATC IRMode
1631 snd-ad1816a= [HW,ALSA]
1633 snd-ad1848= [HW,ALSA]
1635 snd-ali5451= [HW,ALSA]
1637 snd-als100= [HW,ALSA]
1639 snd-als4000= [HW,ALSA]
1641 snd-azt2320= [HW,ALSA]
1643 snd-cmi8330= [HW,ALSA]
1645 snd-cmipci= [HW,ALSA]
1647 snd-cs4231= [HW,ALSA]
1649 snd-cs4232= [HW,ALSA]
1651 snd-cs4236= [HW,ALSA]
1653 snd-cs4281= [HW,ALSA]
1655 snd-cs46xx= [HW,ALSA]
1657 snd-dt019x= [HW,ALSA]
1659 snd-dummy= [HW,ALSA]
1661 snd-emu10k1= [HW,ALSA]
1663 snd-ens1370= [HW,ALSA]
1665 snd-ens1371= [HW,ALSA]
1667 snd-es968= [HW,ALSA]
1669 snd-es1688= [HW,ALSA]
1671 snd-es18xx= [HW,ALSA]
1673 snd-es1938= [HW,ALSA]
1675 snd-es1968= [HW,ALSA]
1677 snd-fm801= [HW,ALSA]
1679 snd-gusclassic= [HW,ALSA]
1681 snd-gusextreme= [HW,ALSA]
1683 snd-gusmax= [HW,ALSA]
1685 snd-hdsp= [HW,ALSA]
1687 snd-ice1712= [HW,ALSA]
1689 snd-intel8x0= [HW,ALSA]
1691 snd-interwave= [HW,ALSA]
1693 snd-interwave-stb=
1694 [HW,ALSA]
1696 snd-korg1212= [HW,ALSA]
1698 snd-maestro3= [HW,ALSA]
1700 snd-mpu401= [HW,ALSA]
1702 snd-mtpav= [HW,ALSA]
1704 snd-nm256= [HW,ALSA]
1706 snd-opl3sa2= [HW,ALSA]
1708 snd-opti92x-ad1848=
1709 [HW,ALSA]
1711 snd-opti92x-cs4231=
1712 [HW,ALSA]
1714 snd-opti93x= [HW,ALSA]
1716 snd-pmac= [HW,ALSA]
1718 snd-rme32= [HW,ALSA]
1720 snd-rme96= [HW,ALSA]
1722 snd-rme9652= [HW,ALSA]
1724 snd-sb8= [HW,ALSA]
1726 snd-sb16= [HW,ALSA]
1728 snd-sbawe= [HW,ALSA]
1730 snd-serial= [HW,ALSA]
1732 snd-sgalaxy= [HW,ALSA]
1734 snd-sonicvibes= [HW,ALSA]
1736 snd-sun-amd7930=
1737 [HW,ALSA]
1739 snd-sun-cs4231= [HW,ALSA]
1741 snd-trident= [HW,ALSA]
1743 snd-usb-audio= [HW,ALSA,USB]
1745 snd-via82xx= [HW,ALSA]
1747 snd-virmidi= [HW,ALSA]
1749 snd-wavefront= [HW,ALSA]
1751 snd-ymfpci= [HW,ALSA]
1753 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1754 See Documentation/sonypi.txt
1756 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1757 See Documentation/specialix.txt.
1759 spia_io_base= [HW,MTD]
1760 spia_fio_base=
1761 spia_pedr=
1762 spia_peddr=
1764 sscape= [HW,OSS]
1765 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1767 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1768 See Documentation/scsi/st.txt.
1770 st0x= [HW,SCSI]
1771 See header of drivers/scsi/seagate.c.
1773 sti= [PARISC,HW]
1774 Format: <num>
1775 Set the STI (builtin display/keyboard on the HP-PARISC
1776 machines) console (graphic card) which should be used
1777 as the initial boot-console.
1778 See also comment in drivers/video/console/sticore.c.
1780 sti_font= [HW]
1781 See comment in drivers/video/console/sticore.c.
1783 stifb= [HW]
1784 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1786 sunrpc.pool_mode=
1787 [NFS]
1788 Control how the NFS server code allocates CPUs to
1789 service thread pools. Depending on how many NICs
1790 you have and where their interrupts are bound, this
1791 option will affect which CPUs will do NFS serving.
1792 Note: this parameter cannot be changed while the
1793 NFS server is running.
1795 auto the server chooses an appropriate mode
1796 automatically using heuristics
1797 global a single global pool contains all CPUs
1798 percpu one pool for each CPU
1799 pernode one pool for each NUMA node (equivalent
1800 to global on non-NUMA machines)
1802 swiotlb= [IA-64] Number of I/O TLB slabs
1804 switches= [HW,M68k]
1806 sym53c416= [HW,SCSI]
1807 See header of drivers/scsi/sym53c416.c.
1809 sysrq_always_enabled
1810 [KNL]
1811 Ignore sysrq setting - this boot parameter will
1812 neutralize any effect of /proc/sys/kernel/sysrq.
1813 Useful for debugging.
1815 t128= [HW,SCSI]
1816 See header of drivers/scsi/t128.c.
1818 tdfx= [HW,DRM]
1820 thash_entries= [KNL,NET]
1821 Set number of hash buckets for TCP connection
1823 time Show timing data prefixed to each printk message line
1824 [deprecated, see 'printk.time']
1826 tipar.timeout= [HW,PPT]
1827 Set communications timeout in tenths of a second
1828 (default 15).
1830 tipar.delay= [HW,PPT]
1831 Set inter-bit delay in microseconds (default 10).
1833 tmc8xx= [HW,SCSI]
1834 See header of drivers/scsi/seagate.c.
1836 tmscsim= [HW,SCSI]
1837 See comment before function dc390_setup() in
1838 drivers/scsi/tmscsim.c.
1840 tp720= [HW,PS2]
1842 trix= [HW,OSS] MediaTrix AudioTrix Pro
1843 Format:
1844 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1846 tsdev.xres= [TS] Horizontal screen resolution.
1847 tsdev.yres= [TS] Vertical screen resolution.
1849 turbografx.map[2|3]= [HW,JOY]
1850 TurboGraFX parallel port interface
1851 Format:
1852 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1853 See also Documentation/input/joystick-parport.txt
1855 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1856 See header of drivers/scsi/u14-34f.c.
1858 uart401= [HW,OSS]
1859 Format: <io>,<irq>
1861 uart6850= [HW,OSS]
1862 Format: <io>,<irq>
1864 uhci-hcd.ignore_oc=
1865 [USB] Ignore overcurrent events (default N).
1866 Some badly-designed motherboards generate lots of
1867 bogus events, for ports that aren't wired to
1868 anything. Set this parameter to avoid log spamming.
1869 Note that genuine overcurrent events won't be
1870 reported either.
1872 usbcore.autosuspend=
1873 [USB] The autosuspend time delay (in seconds) used
1874 for newly-detected USB devices (default 2). This
1875 is the time required before an idle device will be
1876 autosuspended. Devices for which the delay is set
1877 to a negative value won't be autosuspended at all.
1879 usbhid.mousepoll=
1880 [USBHID] The interval which mice are to be polled at.
1882 vdso= [X86-32,SH,x86-64]
1883 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1884 vdso=1: enable VDSO (default)
1885 vdso=0: disable VDSO mapping
1887 vector= [IA-64,SMP]
1888 vector=percpu: enable percpu vector domain
1890 video= [FB] Frame buffer configuration
1891 See Documentation/fb/modedb.txt.
1893 vga= [BOOT,X86-32] Select a particular video mode
1894 See Documentation/i386/boot.txt and
1895 Documentation/svga.txt.
1896 Use vga=ask for menu.
1897 This is actually a boot loader parameter; the value is
1898 passed to the kernel using a special protocol.
1900 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1901 size of <nn>. This can be used to increase the
1902 minimum size (128MB on x86). It can also be used to
1903 decrease the size and leave more room for directly
1904 mapped kernel RAM.
1906 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1907 Format: <command>
1909 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1910 Format: <command>
1912 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1913 Format: <command>
1915 waveartist= [HW,OSS]
1916 Format: <io>,<irq>,<dma>,<dma2>
1918 wd33c93= [HW,SCSI]
1919 See header of drivers/scsi/wd33c93.c.
1921 wd7000= [HW,SCSI]
1922 See header of drivers/scsi/wd7000.c.
1924 wdt= [WDT] Watchdog
1925 See Documentation/watchdog/watchdog.txt.
1927 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1928 xd_geo= See header of drivers/block/xd.c.
1930 xirc2ps_cs= [NET,PCMCIA]
1931 Format:
1932 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1934 norandmaps Don't use address space randomization
1935 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1937 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1938 This is useful to get more information why
1939 you got a "dwarf2 unwinder stuck"
1941 ______________________________________________________________________
1943 TODO:
1945 Add documentation for ALSA options.
1946 Add more DRM drivers.