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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AX25 Appropriate AX.25 support is enabled.
38 BLACKFIN Blackfin architecture is enabled.
39 DRM Direct Rendering Management support is enabled.
40 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
41 EFI EFI Partitioning (GPT) is enabled
42 EIDE EIDE/ATAPI support is enabled.
43 FB The frame buffer device is enabled.
44 HW Appropriate hardware is enabled.
45 IA-64 IA-64 architecture is enabled.
46 IOSCHED More than one I/O scheduler is enabled.
47 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
48 ISAPNP ISA PnP code is enabled.
49 ISDN Appropriate ISDN support is enabled.
50 JOY Appropriate joystick support is enabled.
51 LIBATA Libata driver is enabled
52 LP Printer support is enabled.
53 LOOP Loopback device support is enabled.
54 M68k M68k architecture is enabled.
55 These options have more detailed description inside of
56 Documentation/m68k/kernel-options.txt.
57 MCA MCA bus support is enabled.
58 MDA MDA console support is enabled.
59 MOUSE Appropriate mouse support is enabled.
60 MSI Message Signaled Interrupts (PCI).
61 MTD MTD (Memory Technology Device) support is enabled.
62 NET Appropriate network support is enabled.
63 NUMA NUMA support is enabled.
64 GENERIC_TIME The generic timeofday code is enabled.
65 NFS Appropriate NFS support is enabled.
66 OSS OSS sound support is enabled.
67 PV_OPS A paravirtualized kernel is enabled.
68 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
69 PARISC The PA-RISC architecture is enabled.
70 PCI PCI bus support is enabled.
71 PCMCIA The PCMCIA subsystem is enabled.
72 PNP Plug & Play support is enabled.
73 PPC PowerPC architecture is enabled.
74 PPT Parallel port support is enabled.
75 PS2 Appropriate PS/2 support is enabled.
76 RAM RAM disk support is enabled.
77 S390 S390 architecture is enabled.
78 SCSI Appropriate SCSI support is enabled.
79 A lot of drivers has their options described inside of
80 Documentation/scsi/.
81 SELINUX SELinux support is enabled.
82 SERIAL Serial support is enabled.
83 SH SuperH architecture is enabled.
84 SMP The kernel is an SMP kernel.
85 SPARC Sparc architecture is enabled.
86 SWSUSP Software suspend is enabled.
87 TS Appropriate touchscreen support is enabled.
88 USB USB support is enabled.
89 USBHID USB Human Interface Device support is enabled.
90 V4L Video For Linux support is enabled.
91 VGA The VGA console has been enabled.
92 VT Virtual terminal support is enabled.
93 WDT Watchdog support is enabled.
94 XT IBM PC/XT MFM hard disk support is enabled.
95 X86-32 X86-32, aka i386 architecture is enabled.
96 X86-64 X86-64 architecture is enabled.
97 More X86-64 boot options can be found in
98 Documentation/x86_64/boot-options.txt .
100 In addition, the following text indicates that the option:
102 BUGS= Relates to possible processor bugs on the said processor.
103 KNL Is a kernel start-up parameter.
104 BOOT Is a boot loader parameter.
106 Parameters denoted with BOOT are actually interpreted by the boot
107 loader, and have no meaning to the kernel directly.
108 Do not modify the syntax of boot loader parameters without extreme
109 need or coordination with <Documentation/i386/boot.txt>.
111 There are also arch-specific kernel-parameters not documented here.
112 See for example <Documentation/x86_64/boot-options.txt>.
114 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
115 a trailing = on the name of any parameter states that that parameter will
116 be entered as an environment variable, whereas its absence indicates that
117 it will appear as a kernel argument readable via /proc/cmdline by programs
118 running once the system is up.
120 The number of kernel parameters is not limited, but the length of the
121 complete command line (parameters including spaces etc.) is limited to
122 a fixed number of characters. This limit depends on the architecture
123 and is between 256 and 4096 characters. It is defined in the file
124 ./include/asm/setup.h as COMMAND_LINE_SIZE.
127 acpi= [HW,ACPI,X86-64,i386]
128 Advanced Configuration and Power Interface
129 Format: { force | off | ht | strict | noirq }
130 force -- enable ACPI if default was off
131 off -- disable ACPI if default was on
132 noirq -- do not use ACPI for IRQ routing
133 ht -- run only enough ACPI to enable Hyper Threading
134 strict -- Be less tolerant of platforms that are not
135 strictly ACPI specification compliant.
137 See also Documentation/pm.txt, pci=noacpi
139 acpi_apic_instance= [ACPI, IOAPIC]
140 Format: <int>
141 2: use 2nd APIC table, if available
142 1,0: use 1st APIC table
143 default: 0
145 acpi_sleep= [HW,ACPI] Sleep options
146 Format: { s3_bios, s3_mode }
147 See Documentation/power/video.txt
149 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
150 Format: { level | edge | high | low }
152 acpi_irq_balance [HW,ACPI]
153 ACPI will balance active IRQs
154 default in APIC mode
156 acpi_irq_nobalance [HW,ACPI]
157 ACPI will not move active IRQs (default)
158 default in PIC mode
160 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
161 use by PCI
162 Format: <irq>,<irq>...
164 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
165 Format: <irq>,<irq>...
167 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
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 [X86-32,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 agp= [AGP]
231 { off | try_unsupported }
232 off: disable AGP support
233 try_unsupported: try to drive unsupported chipsets
234 (may crash computer or cause data corruption)
236 enable_timer_pin_1 [i386,x86-64]
237 Enable PIN 1 of APIC timer
238 Can be useful to work around chipset bugs
239 (in particular on some ATI chipsets).
240 The kernel tries to set a reasonable default.
242 disable_timer_pin_1 [i386,x86-64]
243 Disable PIN 1 of APIC timer
244 Can be useful to work around chipset bugs.
246 ad1848= [HW,OSS]
247 Format: <io>,<irq>,<dma>,<dma2>,<type>
249 advansys= [HW,SCSI]
250 See header of drivers/scsi/advansys.c.
252 advwdt= [HW,WDT] Advantech WDT
253 Format: <iostart>,<iostop>
255 aedsp16= [HW,OSS] Audio Excel DSP 16
256 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
257 See also header of sound/oss/aedsp16.c.
259 aha152x= [HW,SCSI]
260 See Documentation/scsi/aha152x.txt.
262 aha1542= [HW,SCSI]
263 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
265 aic7xxx= [HW,SCSI]
266 See Documentation/scsi/aic7xxx.txt.
268 aic79xx= [HW,SCSI]
269 See Documentation/scsi/aic79xx.txt.
271 amijoy.map= [HW,JOY] Amiga joystick support
272 Map of devices attached to JOY0DAT and JOY1DAT
273 Format: <a>,<b>
274 See also Documentation/kernel/input/joystick.txt
276 analog.map= [HW,JOY] Analog joystick and gamepad support
277 Specifies type or capabilities of an analog joystick
278 connected to one of 16 gameports
279 Format: <type1>,<type2>,..<type16>
281 apc= [HW,SPARC]
282 Power management functions (SPARCstation-4/5 + deriv.)
283 Format: noidle
284 Disable APC CPU standby support. SPARCstation-Fox does
285 not play well with APC CPU idle - disable it if you have
286 APC and your system crashes randomly.
288 apic= [APIC,i386] Advanced Programmable Interrupt Controller
289 Change the output verbosity whilst booting
290 Format: { quiet (default) | verbose | debug }
291 Change the amount of debugging information output
292 when initialising the APIC and IO-APIC components.
294 apm= [APM] Advanced Power Management
295 See header of arch/i386/kernel/apm.c.
297 applicom= [HW]
298 Format: <mem>,<irq>
300 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
301 Format: <io>,<irq>,<nodeID>
303 ataflop= [HW,M68k]
305 atarimouse= [HW,MOUSE] Atari Mouse
307 atascsi= [HW,SCSI] Atari SCSI
309 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
310 EzKey and similar keyboards
312 atkbd.reset= [HW] Reset keyboard during initialization
314 atkbd.set= [HW] Select keyboard code set
315 Format: <int> (2 = AT (default), 3 = PS/2)
317 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
318 keyboards
320 atkbd.softraw= [HW] Choose between synthetic and real raw mode
321 Format: <bool> (0 = real, 1 = synthetic (default))
323 atkbd.softrepeat= [HW]
324 Use software keyboard repeat
326 autotest [IA64]
328 baycom_epp= [HW,AX25]
329 Format: <io>,<mode>
331 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
332 Format: <io>,<mode>
333 See header of drivers/net/hamradio/baycom_par.c.
335 baycom_ser_fdx= [HW,AX25]
336 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
337 Format: <io>,<irq>,<mode>[,<baud>]
338 See header of drivers/net/hamradio/baycom_ser_fdx.c.
340 baycom_ser_hdx= [HW,AX25]
341 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
342 Format: <io>,<irq>,<mode>
343 See header of drivers/net/hamradio/baycom_ser_hdx.c.
345 blkmtd_device= [HW,MTD]
346 blkmtd_erasesz=
347 blkmtd_ro=
348 blkmtd_bs=
349 blkmtd_count=
351 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
352 bttv.radio= Most important insmod options are available as
353 kernel args too.
354 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
355 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
357 BusLogic= [HW,SCSI]
358 See drivers/scsi/BusLogic.c, comment before function
359 BusLogic_ParseDriverOptions().
361 c101= [NET] Moxa C101 synchronous serial card
363 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
364 Sometimes CPU hardware bugs make them report the cache
365 size incorrectly. The kernel will attempt work arounds
366 to fix known problems, but for some CPUs it is not
367 possible to determine what the correct size should be.
368 This option provides an override for these situations.
370 chandev= [HW,NET] Generic channel device initialisation
372 checkreqprot [SELINUX] Set initial checkreqprot flag value.
373 Format: { "0" | "1" }
374 See security/selinux/Kconfig help text.
375 0 -- check protection applied by kernel (includes
376 any implied execute protection).
377 1 -- check protection requested by application.
378 Default value is set via a kernel config option.
379 Value can be changed at runtime via
380 /selinux/checkreqprot.
382 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
383 [Deprecated]
384 Forces specified clocksource (if available) to be used
385 when calculating gettimeofday(). If specified
386 clocksource is not available, it defaults to PIT.
387 Format: { pit | tsc | cyclone | pmtmr }
389 clocksource= [GENERIC_TIME] Override the default clocksource
390 Format: <string>
391 Override the default clocksource and use the clocksource
392 with the name specified.
393 Some clocksource names to choose from, depending on
394 the platform:
395 [all] jiffies (this is the base, fallback clocksource)
396 [ACPI] acpi_pm
397 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
398 pxa_timer,timer3,32k_counter,timer0_1
399 [AVR32] avr32
400 [X86-32] pit,hpet,tsc,vmi-timer;
401 scx200_hrt on Geode; cyclone on IBM x440
402 [MIPS] MIPS
403 [PARISC] cr16
404 [S390] tod
405 [SH] SuperH
406 [SPARC64] tick
407 [X86-64] hpet,tsc
409 code_bytes [IA32] How many bytes of object code to print in an
410 oops report.
411 Range: 0 - 8192
412 Default: 64
414 disable_8254_timer
415 enable_8254_timer
416 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
417 over the 8254 in addition to over the IO-APIC. The
418 kernel tries to set a sensible default.
420 hpet= [X86-32,HPET] option to disable HPET and use PIT.
421 Format: disable
423 com20020= [HW,NET] ARCnet - COM20020 chipset
424 Format:
425 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
427 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
428 Format: <io>[,<irq>]
430 com90xx= [HW,NET]
431 ARCnet - COM90xx chipset (memory-mapped buffers)
432 Format: <io>[,<irq>[,<memstart>]]
434 condev= [HW,S390] console device
435 conmode=
437 console= [KNL] Output console device and options.
439 tty<n> Use the virtual console device <n>.
441 ttyS<n>[,options]
442 ttyUSB0[,options]
443 Use the specified serial port. The options are of
444 the form "bbbbpnf", where "bbbb" is the baud rate,
445 "p" is parity ("n", "o", or "e"), "n" is number of
446 bits, and "f" is flow control ("r" for RTS or
447 omit it). Default is "9600n8".
449 See Documentation/serial-console.txt for more
450 information. See
451 Documentation/networking/netconsole.txt for an
452 alternative.
454 uart[8250],io,<addr>[,options]
455 uart[8250],mmio,<addr>[,options]
456 Start an early, polled-mode console on the 8250/16550
457 UART at the specified I/O port or MMIO address,
458 switching to the matching ttyS device later. The
459 options are the same as for ttyS, above.
461 earlycon= [KNL] Output early console device and options.
462 uart[8250],io,<addr>[,options]
463 uart[8250],mmio,<addr>[,options]
464 Start an early, polled-mode console on the 8250/16550
465 UART at the specified I/O port or MMIO address.
466 The options are the same as for ttyS, above.
468 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
469 Format:
470 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
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,BLACKFIN]
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 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
868 when set.
869 Format: <int>
871 load_ramdisk= [RAM] List of ramdisks to load from floppy
872 See Documentation/ramdisk.txt.
874 lockd.nlm_grace_period=P [NFS] Assign grace period.
875 Format: <integer>
877 lockd.nlm_tcpport=N [NFS] Assign TCP port.
878 Format: <integer>
880 lockd.nlm_timeout=T [NFS] Assign timeout value.
881 Format: <integer>
883 lockd.nlm_udpport=M [NFS] Assign UDP port.
884 Format: <integer>
886 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
887 Format: <irq>
889 loglevel= All Kernel Messages with a loglevel smaller than the
890 console loglevel will be printed to the console. It can
891 also be changed with klogd or other programs. The
892 loglevels are defined as follows:
894 0 (KERN_EMERG) system is unusable
895 1 (KERN_ALERT) action must be taken immediately
896 2 (KERN_CRIT) critical conditions
897 3 (KERN_ERR) error conditions
898 4 (KERN_WARNING) warning conditions
899 5 (KERN_NOTICE) normal but significant condition
900 6 (KERN_INFO) informational
901 7 (KERN_DEBUG) debug-level messages
903 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
904 Format: { n | nk | nM }
905 n must be a power of two. The default size
906 is set in the kernel config file.
908 lp=0 [LP] Specify parallel ports to use, e.g,
909 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
910 lp=reset first parallel port). 'lp=0' disables the
911 lp=auto printer driver. 'lp=reset' (which can be
912 specified in addition to the ports) causes
913 attached printers to be reset. Using
914 lp=port1,port2,... specifies the parallel ports
915 to associate lp devices with, starting with
916 lp0. A port specification may be 'none' to skip
917 that lp device, or a parport name such as
918 'parport0'. Specifying 'lp=auto' instead of a
919 port specification list means that device IDs
920 from each port should be examined, to see if
921 an IEEE 1284-compliant printer is attached; if
922 so, the driver will manage that printer.
923 See also header of drivers/char/lp.c.
925 lpj=n [KNL]
926 Sets loops_per_jiffy to given constant, thus avoiding
927 time-consuming boot-time autodetection (up to 250 ms per
928 CPU). 0 enables autodetection (default). To determine
929 the correct value for your kernel, boot with normal
930 autodetection and see what value is printed. Note that
931 on SMP systems the preset will be applied to all CPUs,
932 which is likely to cause problems if your CPUs need
933 significantly divergent settings. An incorrect value
934 will cause delays in the kernel to be wrong, leading to
935 unpredictable I/O errors and other breakage. Although
936 unlikely, in the extreme case this might damage your
937 hardware.
939 ltpc= [NET]
940 Format: <io>,<irq>,<dma>
942 mac5380= [HW,SCSI] Format:
943 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
945 mac53c9x= [HW,SCSI] Format:
946 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
948 machvec= [IA64] Force the use of a particular machine-vector
949 (machvec) in a generic kernel.
950 Example: machvec=hpzx1_swiotlb
952 max_loop= [LOOP] Maximum number of loopback devices that can
953 be mounted
954 Format: <1-256>
956 maxcpus= [SMP] Maximum number of processors that an SMP kernel
957 should make use of. maxcpus=n : n >= 0 limits the
958 kernel to using 'n' processors. n=0 is a special case,
959 it is equivalent to "nosmp", which also disables
960 the IO APIC.
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 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1088 caches in the slab allocator. Saves per-node memory,
1089 but will impact performance.
1091 noalign [KNL,ARM]
1093 noapic [SMP,APIC] Tells the kernel to not make use of any
1094 IOAPICs that may be present in the system.
1096 noasync [HW,M68K] Disables async and sync negotiation for
1097 all devices.
1099 nobats [PPC] Do not use BATs for mapping kernel lowmem
1100 on "Classic" PPC cores.
1102 nocache [ARM]
1104 nodelayacct [KNL] Disable per-task delay accounting
1106 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1108 noexec [IA-64]
1110 noexec [X86-32,X86-64]
1111 noexec=on: enable non-executable mappings (default)
1112 noexec=off: disable nn-executable mappings
1114 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1115 register save and restore. The kernel will only save
1116 legacy floating-point registers on task switch.
1118 nohlt [BUGS=ARM]
1120 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1121 instruction doesn't work correctly and not to
1122 use it.
1124 nohalt [IA-64] Tells the kernel not to use the power saving
1125 function PAL_HALT_LIGHT when idle. This increases
1126 power-consumption. On the positive side, it reduces
1127 interrupt wake-up latency, which may improve performance
1128 in certain environments such as networked servers or
1129 real-time systems.
1131 nohz= [KNL] Boottime enable/disable dynamic ticks
1132 Valid arguments: on, off
1133 Default: on
1135 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1137 noirqdebug [X86-32] Disables the code which attempts to detect and
1138 disable unhandled interrupt sources.
1140 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1141 broken timer IRQ sources.
1143 noisapnp [ISAPNP] Disables ISA PnP code.
1145 noinitrd [RAM] Tells the kernel not to load any configured
1146 initial RAM disk.
1148 nointroute [IA-64]
1150 nojitter [IA64] Disables jitter checking for ITC timers.
1152 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1154 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1156 noltlbs [PPC] Do not use large page/tlb entries for kernel
1157 lowmem mapping on PPC40x.
1159 nomca [IA-64] Disable machine check abort handling
1161 nomce [X86-32] Machine Check Exception
1163 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1165 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1166 with UP alternatives
1168 noresidual [PPC] Don't use residual data on PReP machines.
1170 noresume [SWSUSP] Disables resume and restores original swap
1171 space.
1173 no-scroll [VGA] Disables scrollback.
1174 This is required for the Braillex ib80-piezo Braille
1175 reader made by F.H. Papenmeier (Germany).
1177 nosbagart [IA-64]
1179 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1181 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1182 and disable the IO APIC. legacy for "maxcpus=0".
1184 nosoftlockup [KNL] Disable the soft-lockup detector.
1186 nosync [HW,M68K] Disables sync negotiation for all devices.
1188 notsc [BUGS=X86-32] Disable Time Stamp Counter
1190 nousb [USB] Disable the USB subsystem
1192 nowb [ARM]
1194 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1195 one of ['zone', 'node', 'default'] can be specified
1196 This can be set from sysctl after boot.
1197 See Documentation/sysctl/vm.txt for details.
1199 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1201 opl3= [HW,OSS]
1202 Format: <io>
1204 oprofile.timer= [HW]
1205 Use timer interrupt instead of performance counters
1207 osst= [HW,SCSI] SCSI Tape Driver
1208 Format: <buffer_size>,<write_threshold>
1209 See also Documentation/scsi/st.txt.
1211 panic= [KNL] Kernel behaviour on panic
1212 Format: <timeout>
1214 parkbd.port= [HW] Parallel port number the keyboard adapter is
1215 connected to, default is 0.
1216 Format: <parport#>
1217 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1218 0 for XT, 1 for AT (default is AT).
1219 Format: <mode>
1221 parport= [HW,PPT] Specify parallel ports. 0 disables.
1222 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1223 Use 'auto' to force the driver to use any
1224 IRQ/DMA settings detected (the default is to
1225 ignore detected IRQ/DMA settings because of
1226 possible conflicts). You can specify the base
1227 address, IRQ, and DMA settings; IRQ and DMA
1228 should be numbers, or 'auto' (for using detected
1229 settings on that particular port), or 'nofifo'
1230 (to avoid using a FIFO even if it is detected).
1231 Parallel ports are assigned in the order they
1232 are specified on the command line, starting
1233 with parport0.
1235 parport_init_mode= [HW,PPT]
1236 Configure VIA parallel port to operate in
1237 a specific mode. This is necessary on Pegasos
1238 computer where firmware has no options for setting
1239 up parallel port mode and sets it to spp.
1240 Currently this function knows 686a and 8231 chips.
1241 Format: [spp|ps2|epp|ecp|ecpepp]
1243 pas2= [HW,OSS] Format:
1244 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1246 pas16= [HW,SCSI]
1247 See header of drivers/scsi/pas16.c.
1249 pause_on_oops=
1250 Halt all CPUs after the first oops has been printed for
1251 the specified number of seconds. This is to be used if
1252 your oopses keep scrolling off the screen.
1254 pcbit= [HW,ISDN]
1256 pcd. [PARIDE]
1257 See header of drivers/block/paride/pcd.c.
1258 See also Documentation/paride.txt.
1260 pci=option[,option...] [PCI] various PCI subsystem options:
1261 off [X86-32] don't probe for the PCI bus
1262 bios [X86-32] force use of PCI BIOS, don't access
1263 the hardware directly. Use this if your machine
1264 has a non-standard PCI host bridge.
1265 nobios [X86-32] disallow use of PCI BIOS, only direct
1266 hardware access methods are allowed. Use this
1267 if you experience crashes upon bootup and you
1268 suspect they are caused by the BIOS.
1269 conf1 [X86-32] Force use of PCI Configuration
1270 Mechanism 1.
1271 conf2 [X86-32] Force use of PCI Configuration
1272 Mechanism 2.
1273 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1274 Configuration
1275 nomsi [MSI] If the PCI_MSI kernel config parameter is
1276 enabled, this kernel boot option can be used to
1277 disable the use of MSI interrupts system-wide.
1278 nosort [X86-32] Don't sort PCI devices according to
1279 order given by the PCI BIOS. This sorting is
1280 done to get a device order compatible with
1281 older kernels.
1282 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1283 routing table. These calls are known to be buggy
1284 on several machines and they hang the machine
1285 when used, but on other computers it's the only
1286 way to get the interrupt routing table. Try
1287 this option if the kernel is unable to allocate
1288 IRQs or discover secondary PCI buses on your
1289 motherboard.
1290 rom [X86-32] Assign address space to expansion ROMs.
1291 Use with caution as certain devices share
1292 address decoders between ROMs and other
1293 resources.
1294 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1295 assigned automatically to PCI devices. You can
1296 make the kernel exclude IRQs of your ISA cards
1297 this way.
1298 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1299 of the PIRQ table (normally generated
1300 by the BIOS) if it is outside the
1301 F0000h-100000h range.
1302 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1303 useful if the kernel is unable to find your
1304 secondary buses and you want to tell it
1305 explicitly which ones they are.
1306 assign-busses [X86-32] Always assign all PCI bus
1307 numbers ourselves, overriding
1308 whatever the firmware may have done.
1309 usepirqmask [X86-32] Honor the possible IRQ mask stored
1310 in the BIOS $PIR table. This is needed on
1311 some systems with broken BIOSes, notably
1312 some HP Pavilion N5400 and Omnibook XE3
1313 notebooks. This will have no effect if ACPI
1314 IRQ routing is enabled.
1315 noacpi [X86-32] Do not use ACPI for IRQ routing
1316 or for PCI scanning.
1317 routeirq Do IRQ routing for all PCI devices.
1318 This is normally done in pci_enable_device(),
1319 so this option is a temporary workaround
1320 for broken drivers that don't call it.
1321 firmware [ARM] Do not re-enumerate the bus but instead
1322 just use the configuration from the
1323 bootloader. This is currently used on
1324 IXP2000 systems where the bus has to be
1325 configured a certain way for adjunct CPUs.
1326 noearly [X86] Don't do any early type 1 scanning.
1327 This might help on some broken boards which
1328 machine check when some devices' config space
1329 is read. But various workarounds are disabled
1330 and some IOMMU drivers will not work.
1331 bfsort Sort PCI devices into breadth-first order.
1332 This sorting is done to get a device
1333 order compatible with older (<= 2.4) kernels.
1334 nobfsort Don't sort PCI devices into breadth-first order.
1335 cbiosize=nn[KMG] The fixed amount of bus space which is
1336 reserved for the CardBus bridge's IO window.
1337 The default value is 256 bytes.
1338 cbmemsize=nn[KMG] The fixed amount of bus space which is
1339 reserved for the CardBus bridge's memory
1340 window. The default value is 64 megabytes.
1342 pcmv= [HW,PCMCIA] BadgePAD 4
1344 pd. [PARIDE]
1345 See Documentation/paride.txt.
1347 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1348 boot time.
1349 Format: { 0 | 1 }
1350 See arch/parisc/kernel/pdc_chassis.c
1352 pf. [PARIDE]
1353 See Documentation/paride.txt.
1355 pg. [PARIDE]
1356 See Documentation/paride.txt.
1358 pirq= [SMP,APIC] Manual mp-table setup
1359 See Documentation/i386/IO-APIC.txt.
1361 plip= [PPT,NET] Parallel port network link
1362 Format: { parport<nr> | timid | 0 }
1363 See also Documentation/parport.txt.
1365 pnpacpi= [ACPI]
1366 { off }
1368 pnpbios= [ISAPNP]
1369 { on | off | curr | res | no-curr | no-res }
1371 pnp_reserve_irq=
1372 [ISAPNP] Exclude IRQs for the autoconfiguration
1374 pnp_reserve_dma=
1375 [ISAPNP] Exclude DMAs for the autoconfiguration
1377 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1378 Ranges are in pairs (I/O port base and size).
1380 pnp_reserve_mem=
1381 [ISAPNP] Exclude memory regions for the
1382 autoconfiguration.
1383 Ranges are in pairs (memory base and size).
1385 print-fatal-signals=
1386 [KNL] debug: print fatal signals
1387 print-fatal-signals=1: print segfault info to
1388 the kernel console.
1389 default: off.
1391 printk.time= Show timing data prefixed to each printk message line
1392 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1394 profile= [KNL] Enable kernel profiling via /proc/profile
1395 Format: [schedule,]<number>
1396 Param: "schedule" - profile schedule points.
1397 Param: <number> - step/bucket size as a power of 2 for
1398 statistical time based profiling.
1399 Param: "sleep" - profile D-state sleeping (millisecs)
1401 processor.max_cstate= [HW,ACPI]
1402 Limit processor to maximum C-state
1403 max_cstate=9 overrides any DMI blacklist limit.
1405 processor.nocst [HW,ACPI]
1406 Ignore the _CST method to determine C-states,
1407 instead using the legacy FADT method
1409 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1410 before loading.
1411 See Documentation/ramdisk.txt.
1413 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1414 probe for; one of (bare|imps|exps|lifebook|any).
1415 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1416 per second.
1417 psmouse.resetafter= [HW,MOUSE]
1418 Try to reset the device after so many bad packets
1419 (0 = never).
1420 psmouse.resolution=
1421 [HW,MOUSE] Set desired mouse resolution, in dpi.
1422 psmouse.smartscroll=
1423 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1424 0 = disabled, 1 = enabled (default).
1426 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1427 Format:
1428 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1430 pt. [PARIDE]
1431 See Documentation/paride.txt.
1433 quiet [KNL] Disable most log messages
1435 r128= [HW,DRM]
1437 raid= [HW,RAID]
1438 See Documentation/md.txt.
1440 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1441 See Documentation/ramdisk.txt.
1443 ramdisk_blocksize= [RAM]
1444 See Documentation/ramdisk.txt.
1446 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1447 New name for the ramdisk parameter.
1448 See Documentation/ramdisk.txt.
1450 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1451 RCU callbacks to process in one batch.
1453 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1454 RCU callbacks over which batch limiting is disabled.
1456 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1457 RCU callbacks below which batch limiting is re-enabled.
1459 rdinit= [KNL]
1460 Format: <full_path>
1461 Run specified binary instead of /init from the ramdisk,
1462 used for early userspace startup. See initrd.
1464 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1465 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1466 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1468 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1470 reservetop= [X86-32]
1471 Format: nn[KMG]
1472 Reserves a hole at the top of the kernel virtual
1473 address space.
1475 reset_devices [KNL] Force drivers to reset the underlying device
1476 during initialization.
1478 resume= [SWSUSP]
1479 Specify the partition device for software suspend
1481 resume_offset= [SWSUSP]
1482 Specify the offset from the beginning of the partition
1483 given by "resume=" at which the swap header is located,
1484 in <PAGE_SIZE> units (needed only for swap files).
1485 See Documentation/power/swsusp-and-swap-files.txt
1487 retain_initrd [RAM] Keep initrd memory after extraction
1489 rhash_entries= [KNL,NET]
1490 Set number of hash buckets for route cache
1492 riscom8= [HW,SERIAL]
1493 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1495 ro [KNL] Mount root device read-only on boot
1497 root= [KNL] Root filesystem
1499 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1500 mount the root filesystem
1502 rootflags= [KNL] Set root filesystem mount option string
1504 rootfstype= [KNL] Set root filesystem type
1506 rootwait [KNL] Wait (indefinitely) for root device to show up.
1507 Useful for devices that are detected asynchronously
1508 (e.g. USB and MMC devices).
1510 rw [KNL] Mount root device read-write on boot
1512 S [KNL] Run init in single mode
1514 sa1100ir [NET]
1515 See drivers/net/irda/sa1100_ir.c.
1517 sb= [HW,OSS]
1518 Format: <io>,<irq>,<dma>,<dma2>
1520 sbni= [NET] Granch SBNI12 leased line adapter
1522 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1523 Format: <io>[,<timeout>[,<isapnp>]]
1525 scsi_debug_*= [SCSI]
1526 See drivers/scsi/scsi_debug.c.
1528 scsi_default_dev_flags=
1529 [SCSI] SCSI default device flags
1530 Format: <integer>
1532 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1533 Format: <vendor>:<model>:<flags>
1534 (flags are integer value)
1536 scsi_logging= [SCSI]
1538 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1539 discovered. async scans them in kernel threads,
1540 allowing boot to proceed. none ignores them, expecting
1541 user space to do the scan.
1543 selinux [SELINUX] Disable or enable SELinux at boot time.
1544 Format: { "0" | "1" }
1545 See security/selinux/Kconfig help text.
1546 0 -- disable.
1547 1 -- enable.
1548 Default value is set via kernel config option.
1549 If enabled at boot time, /selinux/disable can be used
1550 later to disable prior to initial policy load.
1552 selinux_compat_net =
1553 [SELINUX] Set initial selinux_compat_net flag value.
1554 Format: { "0" | "1" }
1555 0 -- use new secmark-based packet controls
1556 1 -- use legacy packet controls
1557 Default value is 0 (preferred).
1558 Value can be changed at runtime via
1559 /selinux/compat_net.
1561 serialnumber [BUGS=X86-32]
1563 sg_def_reserved_size= [SCSI]
1565 shapers= [NET]
1566 Maximal number of shapers.
1568 sim710= [SCSI,HW]
1569 See header of drivers/scsi/sim710.c.
1571 simeth= [IA-64]
1572 simscsi=
1574 slram= [HW,MTD]
1576 slub_debug[=options[,slabs]] [MM, SLUB]
1577 Enabling slub_debug allows one to determine the
1578 culprit if slab objects become corrupted. Enabling
1579 slub_debug can create guard zones around objects and
1580 may poison objects when not in use. Also tracks the
1581 last alloc / free. For more information see
1582 Documentation/vm/slub.txt.
1584 slub_max_order= [MM, SLUB]
1585 Determines the maximum allowed order for slabs.
1586 A high setting may cause OOMs due to memory
1587 fragmentation. For more information see
1588 Documentation/vm/slub.txt.
1590 slub_min_objects= [MM, SLUB]
1591 The minimum number of objects per slab. SLUB will
1592 increase the slab order up to slub_max_order to
1593 generate a sufficiently large slab able to contain
1594 the number of objects indicated. The higher the number
1595 of objects the smaller the overhead of tracking slabs
1596 and the less frequently locks need to be acquired.
1597 For more information see Documentation/vm/slub.txt.
1599 slub_min_order= [MM, SLUB]
1600 Determines the mininum page order for slabs. Must be
1601 lower than slub_max_order.
1602 For more information see Documentation/vm/slub.txt.
1604 slub_nomerge [MM, SLUB]
1605 Disable merging of slabs with similar size. May be
1606 necessary if there is some reason to distinguish
1607 allocs to different slabs. Debug options disable
1608 merging on their own.
1609 For more information see Documentation/vm/slub.txt.
1611 smart2= [HW]
1612 Format: <io1>[,<io2>[,...,<io8>]]
1614 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1615 attempt to substitute SMP alternatives once at boot.
1617 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1618 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1619 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1620 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1621 smsc-ircc2.ircc_irq= [HW] IRQ line
1622 smsc-ircc2.ircc_dma= [HW] DMA channel
1623 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1624 0: Toshiba Satellite 1800 (GP data pin select)
1625 1: Fast pin select (default)
1626 2: ATC IRMode
1628 snd-ad1816a= [HW,ALSA]
1630 snd-ad1848= [HW,ALSA]
1632 snd-ali5451= [HW,ALSA]
1634 snd-als100= [HW,ALSA]
1636 snd-als4000= [HW,ALSA]
1638 snd-azt2320= [HW,ALSA]
1640 snd-cmi8330= [HW,ALSA]
1642 snd-cmipci= [HW,ALSA]
1644 snd-cs4231= [HW,ALSA]
1646 snd-cs4232= [HW,ALSA]
1648 snd-cs4236= [HW,ALSA]
1650 snd-cs4281= [HW,ALSA]
1652 snd-cs46xx= [HW,ALSA]
1654 snd-dt019x= [HW,ALSA]
1656 snd-dummy= [HW,ALSA]
1658 snd-emu10k1= [HW,ALSA]
1660 snd-ens1370= [HW,ALSA]
1662 snd-ens1371= [HW,ALSA]
1664 snd-es968= [HW,ALSA]
1666 snd-es1688= [HW,ALSA]
1668 snd-es18xx= [HW,ALSA]
1670 snd-es1938= [HW,ALSA]
1672 snd-es1968= [HW,ALSA]
1674 snd-fm801= [HW,ALSA]
1676 snd-gusclassic= [HW,ALSA]
1678 snd-gusextreme= [HW,ALSA]
1680 snd-gusmax= [HW,ALSA]
1682 snd-hdsp= [HW,ALSA]
1684 snd-ice1712= [HW,ALSA]
1686 snd-intel8x0= [HW,ALSA]
1688 snd-interwave= [HW,ALSA]
1690 snd-interwave-stb=
1691 [HW,ALSA]
1693 snd-korg1212= [HW,ALSA]
1695 snd-maestro3= [HW,ALSA]
1697 snd-mpu401= [HW,ALSA]
1699 snd-mtpav= [HW,ALSA]
1701 snd-nm256= [HW,ALSA]
1703 snd-opl3sa2= [HW,ALSA]
1705 snd-opti92x-ad1848=
1706 [HW,ALSA]
1708 snd-opti92x-cs4231=
1709 [HW,ALSA]
1711 snd-opti93x= [HW,ALSA]
1713 snd-pmac= [HW,ALSA]
1715 snd-rme32= [HW,ALSA]
1717 snd-rme96= [HW,ALSA]
1719 snd-rme9652= [HW,ALSA]
1721 snd-sb8= [HW,ALSA]
1723 snd-sb16= [HW,ALSA]
1725 snd-sbawe= [HW,ALSA]
1727 snd-serial= [HW,ALSA]
1729 snd-sgalaxy= [HW,ALSA]
1731 snd-sonicvibes= [HW,ALSA]
1733 snd-sun-amd7930=
1734 [HW,ALSA]
1736 snd-sun-cs4231= [HW,ALSA]
1738 snd-trident= [HW,ALSA]
1740 snd-usb-audio= [HW,ALSA,USB]
1742 snd-via82xx= [HW,ALSA]
1744 snd-virmidi= [HW,ALSA]
1746 snd-wavefront= [HW,ALSA]
1748 snd-ymfpci= [HW,ALSA]
1750 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1751 See Documentation/sonypi.txt
1753 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1754 See Documentation/specialix.txt.
1756 spia_io_base= [HW,MTD]
1757 spia_fio_base=
1758 spia_pedr=
1759 spia_peddr=
1761 sscape= [HW,OSS]
1762 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1764 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1765 See Documentation/scsi/st.txt.
1767 st0x= [HW,SCSI]
1768 See header of drivers/scsi/seagate.c.
1770 sti= [PARISC,HW]
1771 Format: <num>
1772 Set the STI (builtin display/keyboard on the HP-PARISC
1773 machines) console (graphic card) which should be used
1774 as the initial boot-console.
1775 See also comment in drivers/video/console/sticore.c.
1777 sti_font= [HW]
1778 See comment in drivers/video/console/sticore.c.
1780 stifb= [HW]
1781 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1783 sunrpc.pool_mode=
1784 [NFS]
1785 Control how the NFS server code allocates CPUs to
1786 service thread pools. Depending on how many NICs
1787 you have and where their interrupts are bound, this
1788 option will affect which CPUs will do NFS serving.
1789 Note: this parameter cannot be changed while the
1790 NFS server is running.
1792 auto the server chooses an appropriate mode
1793 automatically using heuristics
1794 global a single global pool contains all CPUs
1795 percpu one pool for each CPU
1796 pernode one pool for each NUMA node (equivalent
1797 to global on non-NUMA machines)
1799 swiotlb= [IA-64] Number of I/O TLB slabs
1801 switches= [HW,M68k]
1803 sym53c416= [HW,SCSI]
1804 See header of drivers/scsi/sym53c416.c.
1806 sysrq_always_enabled
1807 [KNL]
1808 Ignore sysrq setting - this boot parameter will
1809 neutralize any effect of /proc/sys/kernel/sysrq.
1810 Useful for debugging.
1812 t128= [HW,SCSI]
1813 See header of drivers/scsi/t128.c.
1815 tdfx= [HW,DRM]
1817 thash_entries= [KNL,NET]
1818 Set number of hash buckets for TCP connection
1820 thermal.act= [HW,ACPI]
1821 -1: disable all active trip points in all thermal zones
1822 <degrees C>: override all lowest active trip points
1824 thermal.crt= [HW,ACPI]
1825 -1: disable all critical trip points in all thermal zones
1826 <degrees C>: lower all critical trip points
1828 thermal.nocrt= [HW,ACPI]
1829 Set to disable actions on ACPI thermal zone
1830 critical and hot trip points.
1832 thermal.off= [HW,ACPI]
1833 1: disable ACPI thermal control
1835 thermal.psv= [HW,ACPI]
1836 -1: disable all passive trip points
1837 <degrees C>: override all passive trip points to this value
1839 thermal.tzp= [HW,ACPI]
1840 Specify global default ACPI thermal zone polling rate
1841 <deci-seconds>: poll all this frequency
1842 0: no polling (default)
1844 time Show timing data prefixed to each printk message line
1845 [deprecated, see 'printk.time']
1847 tipar.timeout= [HW,PPT]
1848 Set communications timeout in tenths of a second
1849 (default 15).
1851 tipar.delay= [HW,PPT]
1852 Set inter-bit delay in microseconds (default 10).
1854 tmc8xx= [HW,SCSI]
1855 See header of drivers/scsi/seagate.c.
1857 tmscsim= [HW,SCSI]
1858 See comment before function dc390_setup() in
1859 drivers/scsi/tmscsim.c.
1861 tp720= [HW,PS2]
1863 trix= [HW,OSS] MediaTrix AudioTrix Pro
1864 Format:
1865 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1867 tsdev.xres= [TS] Horizontal screen resolution.
1868 tsdev.yres= [TS] Vertical screen resolution.
1870 turbografx.map[2|3]= [HW,JOY]
1871 TurboGraFX parallel port interface
1872 Format:
1873 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1874 See also Documentation/input/joystick-parport.txt
1876 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1877 See header of drivers/scsi/u14-34f.c.
1879 uart401= [HW,OSS]
1880 Format: <io>,<irq>
1882 uart6850= [HW,OSS]
1883 Format: <io>,<irq>
1885 uhci-hcd.ignore_oc=
1886 [USB] Ignore overcurrent events (default N).
1887 Some badly-designed motherboards generate lots of
1888 bogus events, for ports that aren't wired to
1889 anything. Set this parameter to avoid log spamming.
1890 Note that genuine overcurrent events won't be
1891 reported either.
1893 usbcore.autosuspend=
1894 [USB] The autosuspend time delay (in seconds) used
1895 for newly-detected USB devices (default 2). This
1896 is the time required before an idle device will be
1897 autosuspended. Devices for which the delay is set
1898 to a negative value won't be autosuspended at all.
1900 usbhid.mousepoll=
1901 [USBHID] The interval which mice are to be polled at.
1903 vdso= [X86-32,SH,x86-64]
1904 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1905 vdso=1: enable VDSO (default)
1906 vdso=0: disable VDSO mapping
1908 vector= [IA-64,SMP]
1909 vector=percpu: enable percpu vector domain
1911 video= [FB] Frame buffer configuration
1912 See Documentation/fb/modedb.txt.
1914 vga= [BOOT,X86-32] Select a particular video mode
1915 See Documentation/i386/boot.txt and
1916 Documentation/svga.txt.
1917 Use vga=ask for menu.
1918 This is actually a boot loader parameter; the value is
1919 passed to the kernel using a special protocol.
1921 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1922 size of <nn>. This can be used to increase the
1923 minimum size (128MB on x86). It can also be used to
1924 decrease the size and leave more room for directly
1925 mapped kernel RAM.
1927 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1928 Format: <command>
1930 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1931 Format: <command>
1933 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1934 Format: <command>
1936 waveartist= [HW,OSS]
1937 Format: <io>,<irq>,<dma>,<dma2>
1939 wd33c93= [HW,SCSI]
1940 See header of drivers/scsi/wd33c93.c.
1942 wd7000= [HW,SCSI]
1943 See header of drivers/scsi/wd7000.c.
1945 wdt= [WDT] Watchdog
1946 See Documentation/watchdog/wdt.txt.
1948 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1949 xd_geo= See header of drivers/block/xd.c.
1951 xirc2ps_cs= [NET,PCMCIA]
1952 Format:
1953 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1955 norandmaps Don't use address space randomization
1956 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1958 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1959 This is useful to get more information why
1960 you got a "dwarf2 unwinder stuck"
1962 ______________________________________________________________________
1964 TODO:
1966 Add documentation for ALSA options.
1967 Add more DRM drivers.