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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 ALSA ALSA sound support is enabled.
34 APIC APIC support is enabled.
35 APM Advanced Power Management support is enabled.
36 AX25 Appropriate AX.25 support is enabled.
37 CD Appropriate CD 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-32 IA-32 aka i386 architecture 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 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
68 PARIDE The ParIDE 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 X86-64 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 53c7xx= [HW,SCSI] Amiga SCSI controllers
127 See header of drivers/scsi/53c7xx.c.
128 See also Documentation/scsi/ncr53c7xx.txt.
130 acpi= [HW,ACPI,X86-64,i386]
131 Advanced Configuration and Power Interface
132 Format: { force | off | ht | strict | noirq }
133 force -- enable ACPI if default was off
134 off -- disable ACPI if default was on
135 noirq -- do not use ACPI for IRQ routing
136 ht -- run only enough ACPI to enable Hyper Threading
137 strict -- Be less tolerant of platforms that are not
138 strictly ACPI specification compliant.
140 See also Documentation/pm.txt, pci=noacpi
142 acpi_apic_instance= [ACPI, IOAPIC]
143 Format: <int>
144 2: use 2nd APIC table, if available
145 1,0: use 1st APIC table
146 default: 0
148 acpi_sleep= [HW,ACPI] Sleep options
149 Format: { s3_bios, s3_mode }
150 See Documentation/power/video.txt
152 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
153 Format: { level | edge | high | low }
155 acpi_irq_balance [HW,ACPI]
156 ACPI will balance active IRQs
157 default in APIC mode
159 acpi_irq_nobalance [HW,ACPI]
160 ACPI will not move active IRQs (default)
161 default in PIC mode
163 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
164 use by PCI
165 Format: <irq>,<irq>...
167 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
168 Format: <irq>,<irq>...
170 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
171 Format: To spoof as Windows 98: ="Microsoft Windows"
173 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
174 acpi_osi="string1" # add string1 -- only one string
175 acpi_osi="!string2" # remove built-in string2
176 acpi_osi= # disable all strings
178 acpi_serialize [HW,ACPI] force serialization of AML methods
180 acpi_skip_timer_override [HW,ACPI]
181 Recognize and ignore IRQ0/pin2 Interrupt Override.
182 For broken nForce2 BIOS resulting in XT-PIC timer.
183 acpi_use_timer_override [HW,ACPI}
184 Use timer override. For some broken Nvidia NF5 boards
185 that require a timer override, but don't have
186 HPET
188 acpi.debug_layer= [HW,ACPI]
189 Format: <int>
190 Each bit of the <int> indicates an ACPI debug layer,
191 1: enable, 0: disable. It is useful for boot time
192 debugging. After system has booted up, it can be set
193 via /sys/module/acpi/parameters/debug_layer.
194 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
195 Available bits (add the numbers together) to enable debug output
196 for specific parts of the ACPI subsystem:
197 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
198 0x10 namespace 0x20 parser 0x40 dispatcher
199 0x80 executer 0x100 resources 0x200 acpica debugger
200 0x400 os services 0x800 acpica disassembler.
201 The number can be in decimal or prefixed with 0x in hex.
202 Warning: Many of these options can produce a lot of
203 output and make your system unusable. Be very careful.
205 acpi.debug_level= [HW,ACPI]
206 Format: <int>
207 Each bit of the <int> indicates an ACPI debug level,
208 1: enable, 0: disable. It is useful for boot time
209 debugging. After system has booted up, it can be set
210 via /sys/module/acpi/parameters/debug_level.
211 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
212 Available bits (add the numbers together) to enable different
213 debug output levels of the ACPI subsystem:
214 0x01 error 0x02 warn 0x04 init 0x08 debug object
215 0x10 info 0x20 init names 0x40 parse 0x80 load
216 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
217 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
218 0x10000 resources 0x20000 user requests 0x40000 package.
219 The number can be in decimal or prefixed with 0x in hex.
220 Warning: Many of these options can produce a lot of
221 output and make your system unusable. Be very careful.
224 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
226 acpi_pm_good [IA-32,X86-64]
227 Override the pmtimer bug detection: force the kernel
228 to assume that this machine's pmtimer latches its value
229 and always returns good values.
231 enable_timer_pin_1 [i386,x86-64]
232 Enable PIN 1 of APIC timer
233 Can be useful to work around chipset bugs
234 (in particular on some ATI chipsets).
235 The kernel tries to set a reasonable default.
237 disable_timer_pin_1 [i386,x86-64]
238 Disable PIN 1 of APIC timer
239 Can be useful to work around chipset bugs.
241 ad1816= [HW,OSS]
242 Format: <io>,<irq>,<dma>,<dma2>
243 See also Documentation/sound/oss/AD1816.
245 ad1848= [HW,OSS]
246 Format: <io>,<irq>,<dma>,<dma2>,<type>
248 adlib= [HW,OSS]
249 Format: <io>
251 advansys= [HW,SCSI]
252 See header of drivers/scsi/advansys.c.
254 advwdt= [HW,WDT] Advantech WDT
255 Format: <iostart>,<iostop>
257 aedsp16= [HW,OSS] Audio Excel DSP 16
258 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
259 See also header of sound/oss/aedsp16.c.
261 aha152x= [HW,SCSI]
262 See Documentation/scsi/aha152x.txt.
264 aha1542= [HW,SCSI]
265 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
267 aic7xxx= [HW,SCSI]
268 See Documentation/scsi/aic7xxx.txt.
270 aic79xx= [HW,SCSI]
271 See Documentation/scsi/aic79xx.txt.
273 amijoy.map= [HW,JOY] Amiga joystick support
274 Map of devices attached to JOY0DAT and JOY1DAT
275 Format: <a>,<b>
276 See also Documentation/kernel/input/joystick.txt
278 analog.map= [HW,JOY] Analog joystick and gamepad support
279 Specifies type or capabilities of an analog joystick
280 connected to one of 16 gameports
281 Format: <type1>,<type2>,..<type16>
283 apc= [HW,SPARC]
284 Power management functions (SPARCstation-4/5 + deriv.)
285 Format: noidle
286 Disable APC CPU standby support. SPARCstation-Fox does
287 not play well with APC CPU idle - disable it if you have
288 APC and your system crashes randomly.
290 apic= [APIC,i386] Change the output verbosity whilst booting
291 Format: { quiet (default) | verbose | debug }
292 Change the amount of debugging information output
293 when initialising the APIC and IO-APIC components.
295 apm= [APM] Advanced Power Management
296 See header of arch/i386/kernel/apm.c.
298 applicom= [HW]
299 Format: <mem>,<irq>
301 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
302 Format: <io>,<irq>,<nodeID>
304 ataflop= [HW,M68k]
306 atarimouse= [HW,MOUSE] Atari Mouse
308 atascsi= [HW,SCSI] Atari SCSI
310 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
311 EzKey and similar keyboards
313 atkbd.reset= [HW] Reset keyboard during initialization
315 atkbd.set= [HW] Select keyboard code set
316 Format: <int> (2 = AT (default), 3 = PS/2)
318 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
319 keyboards
321 atkbd.softraw= [HW] Choose between synthetic and real raw mode
322 Format: <bool> (0 = real, 1 = synthetic (default))
324 atkbd.softrepeat= [HW]
325 Use software keyboard repeat
327 autotest [IA64]
329 aztcd= [HW,CD] Aztech CD268 CDROM driver
330 Format: <io>,0x79 (?)
332 baycom_epp= [HW,AX25]
333 Format: <io>,<mode>
335 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
336 Format: <io>,<mode>
337 See header of drivers/net/hamradio/baycom_par.c.
339 baycom_ser_fdx= [HW,AX25]
340 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
341 Format: <io>,<irq>,<mode>[,<baud>]
342 See header of drivers/net/hamradio/baycom_ser_fdx.c.
344 baycom_ser_hdx= [HW,AX25]
345 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
346 Format: <io>,<irq>,<mode>
347 See header of drivers/net/hamradio/baycom_ser_hdx.c.
349 blkmtd_device= [HW,MTD]
350 blkmtd_erasesz=
351 blkmtd_ro=
352 blkmtd_bs=
353 blkmtd_count=
355 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
356 bttv.radio= Most important insmod options are available as
357 kernel args too.
358 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
359 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
361 BusLogic= [HW,SCSI]
362 See drivers/scsi/BusLogic.c, comment before function
363 BusLogic_ParseDriverOptions().
365 c101= [NET] Moxa C101 synchronous serial card
367 cachesize= [BUGS=IA-32] Override level 2 CPU cache size detection.
368 Sometimes CPU hardware bugs make them report the cache
369 size incorrectly. The kernel will attempt work arounds
370 to fix known problems, but for some CPUs it is not
371 possible to determine what the correct size should be.
372 This option provides an override for these situations.
374 cdu31a= [HW,CD]
375 Format: <io>,<irq>[,PAS]
376 See header of drivers/cdrom/cdu31a.c.
378 chandev= [HW,NET] Generic channel device initialisation
380 checkreqprot [SELINUX] Set initial checkreqprot flag value.
381 Format: { "0" | "1" }
382 See security/selinux/Kconfig help text.
383 0 -- check protection applied by kernel (includes
384 any implied execute protection).
385 1 -- check protection requested by application.
386 Default value is set via a kernel config option.
387 Value can be changed at runtime via
388 /selinux/checkreqprot.
390 clock= [BUGS=IA-32, HW] gettimeofday clocksource override.
391 [Deprecated]
392 Forces specified clocksource (if available) to be used
393 when calculating gettimeofday(). If specified
394 clocksource is not available, it defaults to PIT.
395 Format: { pit | tsc | cyclone | pmtmr }
397 clocksource= [GENERIC_TIME] Override the default clocksource
398 Format: <string>
399 Override the default clocksource and use the clocksource
400 with the name specified.
401 Some clocksource names to choose from, depending on
402 the platform:
403 [all] jiffies (this is the base, fallback clocksource)
404 [ACPI] acpi_pm
405 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
406 pxa_timer,timer3,32k_counter,timer0_1
407 [AVR32] avr32
408 [IA-32] pit,hpet,tsc,vmi-timer;
409 scx200_hrt on Geode; cyclone on IBM x440
410 [MIPS] MIPS
411 [PARISC] cr16
412 [S390] tod
413 [SH] SuperH
414 [SPARC64] tick
415 [X86-64] hpet,tsc
417 code_bytes [IA32] How many bytes of object code to print in an
418 oops report.
419 Range: 0 - 8192
420 Default: 64
422 disable_8254_timer
423 enable_8254_timer
424 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
425 over the 8254 in addition to over the IO-APIC. The
426 kernel tries to set a sensible default.
428 hpet= [IA-32,HPET] option to disable HPET and use PIT.
429 Format: disable
431 cm206= [HW,CD]
432 Format: { auto | [<io>,][<irq>] }
434 com20020= [HW,NET] ARCnet - COM20020 chipset
435 Format:
436 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
438 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
439 Format: <io>[,<irq>]
441 com90xx= [HW,NET]
442 ARCnet - COM90xx chipset (memory-mapped buffers)
443 Format: <io>[,<irq>[,<memstart>]]
445 condev= [HW,S390] console device
446 conmode=
448 console= [KNL] Output console device and options.
450 tty<n> Use the virtual console device <n>.
452 ttyS<n>[,options]
453 ttyUSB0[,options]
454 Use the specified serial port. The options are of
455 the form "bbbbpnf", where "bbbb" is the baud rate,
456 "p" is parity ("n", "o", or "e"), "n" is number of
457 bits, and "f" is flow control ("r" for RTS or
458 omit it). Default is "9600n8".
460 See Documentation/serial-console.txt for more
461 information. See
462 Documentation/networking/netconsole.txt for an
463 alternative.
465 uart,io,<addr>[,options]
466 uart,mmio,<addr>[,options]
467 Start an early, polled-mode console on the 8250/16550
468 UART at the specified I/O port or MMIO address,
469 switching to the matching ttyS device later. The
470 options are the same as for ttyS, above.
472 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
473 Format:
474 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
476 cpia_pp= [HW,PPT]
477 Format: { parport<nr> | auto | none }
479 crashkernel=nn[KMG]@ss[KMG]
480 [KNL] Reserve a chunk of physical memory to
481 hold a kernel to switch to with kexec on panic.
483 cs4232= [HW,OSS]
484 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
486 cs89x0_dma= [HW,NET]
487 Format: <dma>
489 cs89x0_media= [HW,NET]
490 Format: { rj45 | aui | bnc }
492 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
494 dasd= [HW,NET]
495 See header of drivers/s390/block/dasd_devmap.c.
497 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
498 (one device per port)
499 Format: <port#>,<type>
500 See also Documentation/input/joystick-parport.txt
502 debug [KNL] Enable kernel debugging (events log level).
504 debug_locks_verbose=
505 [KNL] verbose self-tests
506 Format=<0|1>
507 Print debugging info while doing the locking API
508 self-tests.
509 We default to 0 (no extra messages), setting it to
510 1 will print _a lot_ more information - normally
511 only useful to kernel developers.
513 decnet= [HW,NET]
514 Format: <area>[,<node>]
515 See also Documentation/networking/decnet.txt.
517 default_blu= [VT]
518 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
519 Change the default blue palette of the console.
520 This is a 16-member array composed of values
521 ranging from 0-255.
523 default_grn= [VT]
524 Format: <green0>,<green1>,<green2>,...,<green15>
525 Change the default green palette of the console.
526 This is a 16-member array composed of values
527 ranging from 0-255.
529 default_red= [VT]
530 Format: <red0>,<red1>,<red2>,...,<red15>
531 Change the default red palette of the console.
532 This is a 16-member array composed of values
533 ranging from 0-255.
535 default_utf8= [VT]
536 Format=<0|1>
537 Set system-wide default UTF-8 mode for all tty's.
538 Default is 0 and by setting to 1, it enables UTF-8
539 mode for all newly opened or allocated terminals.
541 dhash_entries= [KNL]
542 Set number of hash buckets for dentry cache.
544 digi= [HW,SERIAL]
545 IO parameters + enable/disable command.
547 digiepca= [HW,SERIAL]
548 See drivers/char/README.epca and
549 Documentation/digiepca.txt.
551 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
552 support available.
553 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
555 dmasound= [HW,OSS] Sound subsystem buffers
557 dscc4.setup= [NET]
559 dtc3181e= [HW,SCSI]
561 earlyprintk= [IA-32,X86-64,SH]
562 earlyprintk=vga
563 earlyprintk=serial[,ttySn[,baudrate]]
565 Append ",keep" to not disable it when the real console
566 takes over.
568 Only vga or serial at a time, not both.
570 Currently only ttyS0 and ttyS1 are supported.
572 Interaction with the standard serial driver is not
573 very good.
575 The VGA output is eventually overwritten by the real
576 console.
578 eata= [HW,SCSI]
580 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
581 Format: <int>
582 0: polling mode
583 non-0: interrupt mode (default)
585 eda= [HW,PS2]
587 edb= [HW,PS2]
589 edd= [EDD]
590 Format: {"of[f]" | "sk[ipmbr]"}
591 See comment in arch/i386/boot/edd.S
593 eicon= [HW,ISDN]
594 Format: <id>,<membase>,<irq>
596 eisa_irq_edge= [PARISC,HW]
597 See header of drivers/parisc/eisa.c.
599 elanfreq= [IA-32]
600 See comment before function elanfreq_setup() in
601 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
603 elevator= [IOSCHED]
604 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
605 See Documentation/block/as-iosched.txt and
606 Documentation/block/deadline-iosched.txt for details.
608 elfcorehdr= [IA-32, X86_64]
609 Specifies physical address of start of kernel core
610 image elf header. Generally kexec loader will
611 pass this option to capture kernel.
612 See Documentation/kdump/kdump.txt for details.
614 enforcing [SELINUX] Set initial enforcing status.
615 Format: {"0" | "1"}
616 See security/selinux/Kconfig help text.
617 0 -- permissive (log only, no denials).
618 1 -- enforcing (deny and log).
619 Default value is 0.
620 Value can be changed at runtime via /selinux/enforce.
622 es1371= [HW,OSS]
623 Format: <spdif>,[<nomix>,[<amplifier>]]
624 See also header of sound/oss/es1371.c.
626 ether= [HW,NET] Ethernet cards parameters
627 This option is obsoleted by the "netdev=" option, which
628 has equivalent usage. See its documentation for details.
630 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
631 Format: <io>[,<irq>]
633 failslab=
634 fail_page_alloc=
635 fail_make_request=[KNL]
636 General fault injection mechanism.
637 Format: <interval>,<probability>,<space>,<times>
638 See also /Documentation/fault-injection/.
640 fd_mcs= [HW,SCSI]
641 See header of drivers/scsi/fd_mcs.c.
643 fdomain= [HW,SCSI]
644 See header of drivers/scsi/fdomain.c.
646 floppy= [HW]
647 See Documentation/floppy.txt.
649 gamecon.map[2|3]=
650 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
651 support via parallel port (up to 5 devices per port)
652 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
653 See also Documentation/input/joystick-parport.txt
655 gamma= [HW,DRM]
657 gdth= [HW,SCSI]
658 See header of drivers/scsi/gdth.c.
660 gpt [EFI] Forces disk with valid GPT signature but
661 invalid Protective MBR to be treated as GPT.
663 gscd= [HW,CD]
664 Format: <io>
666 gvp11= [HW,SCSI]
668 hashdist= [KNL,NUMA] Large hashes allocated during boot
669 are distributed across NUMA nodes. Defaults on
670 for IA-64, off otherwise.
671 Format: 0 | 1 (for off | on)
673 hcl= [IA-64] SGI's Hardware Graph compatibility layer
675 hd= [EIDE] (E)IDE hard drive subsystem geometry
676 Format: <cyl>,<head>,<sect>
678 hd?= [HW] (E)IDE subsystem
679 hd?lun= See Documentation/ide.txt.
681 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
682 size of <nn>. This works even on boxes that have no
683 highmem otherwise. This also works to reduce highmem
684 size on bigger boxes.
686 highres= [KNL] Enable/disable high resolution timer mode.
687 Valid parameters: "on", "off"
688 Default: "on"
690 hisax= [HW,ISDN]
691 See Documentation/isdn/README.HiSax.
693 hugepages= [HW,IA-32,IA-64] Maximal number of HugeTLB pages.
695 i8042.direct [HW] Put keyboard port into non-translated mode
696 i8042.dumbkbd [HW] Pretend that controller can only read data from
697 keyboard and cannot control its state
698 (Don't attempt to blink the leds)
699 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
700 i8042.nokbd [HW] Don't check/create keyboard port
701 i8042.nomux [HW] Don't check presence of an active multiplexing
702 controller
703 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
704 controllers
705 i8042.panicblink=
706 [HW] Frequency with which keyboard LEDs should blink
707 when kernel panics (default is 0.5 sec)
708 i8042.reset [HW] Reset the controller during init and cleanup
709 i8042.unlock [HW] Unlock (ignore) the keylock
711 i810= [HW,DRM]
713 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
714 indicates that the driver is running on unsupported
715 hardware.
716 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
717 does not match list of supported models.
718 i8k.power_status
719 [HW] Report power status in /proc/i8k
720 (disabled by default)
721 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
722 capability is set.
724 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
725 See Documentation/mca.txt.
727 icn= [HW,ISDN]
728 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
730 ide= [HW] (E)IDE subsystem
731 Format: ide=nodma or ide=doubler or ide=reverse
732 See Documentation/ide.txt.
734 ide?= [HW] (E)IDE subsystem
735 Format: ide?=noprobe or chipset specific parameters.
736 See Documentation/ide.txt.
738 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
739 See Documentation/ide.txt.
741 idle= [X86]
742 Format: idle=poll or idle=mwait
743 Poll forces a polling idle loop that can slightly improves the performance
744 of waking up a idle CPU, but will use a lot of power and make the system
745 run hot. Not recommended.
746 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
747 to not use it because it doesn't save as much power as a normal idle
748 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
749 as idle=poll.
751 ignore_loglevel [KNL]
752 Ignore loglevel setting - this will print /all/
753 kernel messages to the console. Useful for debugging.
755 ihash_entries= [KNL]
756 Set number of hash buckets for inode cache.
758 in2000= [HW,SCSI]
759 See header of drivers/scsi/in2000.c.
761 init= [KNL]
762 Format: <full_path>
763 Run specified binary instead of /sbin/init as init
764 process.
766 initcall_debug [KNL] Trace initcalls as they are executed. Useful
767 for working out where the kernel is dying during
768 startup.
770 initrd= [BOOT] Specify the location of the initial ramdisk
772 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
773 Format: <irq>
775 inttest= [IA64]
777 io7= [HW] IO7 for Marvel based alpha systems
778 See comment before marvel_specify_io7 in
779 arch/alpha/kernel/core_marvel.c.
781 ip= [IP_PNP]
782 See Documentation/nfsroot.txt.
784 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
785 See comment before ip2_setup() in drivers/char/ip2.c.
787 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
788 See header of drivers/scsi/ips.c.
790 ports= [IP_VS_FTP] IPVS ftp helper module
791 Default is 21.
792 Up to 8 (IP_VS_APP_MAX_PORTS) ports
793 may be specified.
794 Format: <port>,<port>....
796 irqfixup [HW]
797 When an interrupt is not handled search all handlers
798 for it. Intended to get systems with badly broken
799 firmware running.
801 irqpoll [HW]
802 When an interrupt is not handled search all handlers
803 for it. Also check all handlers each timer
804 interrupt. Intended to get systems with badly broken
805 firmware running.
807 isapnp= [ISAPNP]
808 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
810 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
811 Format:
812 <cpu number>,...,<cpu number>
813 or
814 <cpu number>-<cpu number> (must be a positive range in ascending order)
815 or a mixture
816 <cpu number>,...,<cpu number>-<cpu number>
817 This option can be used to specify one or more CPUs
818 to isolate from the general SMP balancing and scheduling
819 algorithms. The only way to move a process onto or off
820 an "isolated" CPU is via the CPU affinity syscalls.
821 <cpu number> begins at 0 and the maximum value is
822 "number of CPUs in system - 1".
824 This option is the preferred way to isolate CPUs. The
825 alternative -- manually setting the CPU mask of all
826 tasks in the system -- can cause problems and
827 suboptimal load balancer performance.
829 isp16= [HW,CD]
830 Format: <io>,<irq>,<dma>,<setup>
832 iucv= [HW,NET]
834 js= [HW,JOY] Analog joystick
835 See Documentation/input/joystick.txt.
837 keepinitrd [HW,ARM]
839 kstack=N [IA-32,X86-64] Print N words from the kernel stack
840 in oops dumps.
842 l2cr= [PPC]
844 lapic [IA-32,APIC] Enable the local APIC even if BIOS
845 disabled it.
847 lapic_timer_c2_ok [IA-32,x86-64,APIC] trust the local apic timer in
848 C2 power state.
850 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
851 Format: addr:<io>,irq:<irq>
853 legacy_serial.force [HW,IA-32,X86-64]
854 Probe for COM ports at legacy addresses even
855 if PNPBIOS or ACPI should describe them. This
856 is for working around firmware defects.
858 llsc*= [IA64] See function print_params() in
859 arch/ia64/sn/kernel/llsc4.c.
861 load_ramdisk= [RAM] List of ramdisks to load from floppy
862 See Documentation/ramdisk.txt.
864 lockd.nlm_grace_period=P [NFS] Assign grace period.
865 Format: <integer>
867 lockd.nlm_tcpport=N [NFS] Assign TCP port.
868 Format: <integer>
870 lockd.nlm_timeout=T [NFS] Assign timeout value.
871 Format: <integer>
873 lockd.nlm_udpport=M [NFS] Assign UDP port.
874 Format: <integer>
876 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
877 Format: <irq>
879 loglevel= All Kernel Messages with a loglevel smaller than the
880 console loglevel will be printed to the console. It can
881 also be changed with klogd or other programs. The
882 loglevels are defined as follows:
884 0 (KERN_EMERG) system is unusable
885 1 (KERN_ALERT) action must be taken immediately
886 2 (KERN_CRIT) critical conditions
887 3 (KERN_ERR) error conditions
888 4 (KERN_WARNING) warning conditions
889 5 (KERN_NOTICE) normal but significant condition
890 6 (KERN_INFO) informational
891 7 (KERN_DEBUG) debug-level messages
893 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
894 Format: { n | nk | nM }
895 n must be a power of two. The default size
896 is set in the kernel config file.
898 lp=0 [LP] Specify parallel ports to use, e.g,
899 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
900 lp=reset first parallel port). 'lp=0' disables the
901 lp=auto printer driver. 'lp=reset' (which can be
902 specified in addition to the ports) causes
903 attached printers to be reset. Using
904 lp=port1,port2,... specifies the parallel ports
905 to associate lp devices with, starting with
906 lp0. A port specification may be 'none' to skip
907 that lp device, or a parport name such as
908 'parport0'. Specifying 'lp=auto' instead of a
909 port specification list means that device IDs
910 from each port should be examined, to see if
911 an IEEE 1284-compliant printer is attached; if
912 so, the driver will manage that printer.
913 See also header of drivers/char/lp.c.
915 lpj=n [KNL]
916 Sets loops_per_jiffy to given constant, thus avoiding
917 time-consuming boot-time autodetection (up to 250 ms per
918 CPU). 0 enables autodetection (default). To determine
919 the correct value for your kernel, boot with normal
920 autodetection and see what value is printed. Note that
921 on SMP systems the preset will be applied to all CPUs,
922 which is likely to cause problems if your CPUs need
923 significantly divergent settings. An incorrect value
924 will cause delays in the kernel to be wrong, leading to
925 unpredictable I/O errors and other breakage. Although
926 unlikely, in the extreme case this might damage your
927 hardware.
929 ltpc= [NET]
930 Format: <io>,<irq>,<dma>
932 mac5380= [HW,SCSI] Format:
933 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
935 mac53c9x= [HW,SCSI] Format:
936 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
938 machvec= [IA64] Force the use of a particular machine-vector
939 (machvec) in a generic kernel.
940 Example: machvec=hpzx1_swiotlb
942 max_loop= [LOOP] Maximum number of loopback devices that can
943 be mounted
944 Format: <1-256>
946 maxcpus= [SMP] Maximum number of processors that an SMP kernel
947 should make use of.
948 Using "nosmp" or "maxcpus=0" will disable SMP
949 entirely (the MPS table probe still happens, though).
950 A command-line option of "maxcpus=<NUM>", where <NUM>
951 is an integer greater than 0, limits the maximum number
952 of CPUs activated in SMP mode to <NUM>.
953 Using "maxcpus=1" on an SMP kernel is the trivial
954 case of an SMP kernel with only one CPU.
956 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
957 equal to this physical address is ignored.
959 max_luns= [SCSI] Maximum number of LUNs to probe.
960 Should be between 1 and 2^32-1.
962 max_report_luns=
963 [SCSI] Maximum number of LUNs received.
964 Should be between 1 and 16384.
966 mca-pentium [BUGS=IA-32]
968 mcatest= [IA-64]
970 mcd= [HW,CD]
971 Format: <port>,<irq>,<mitsumi_bug_93_wait>
973 mcdx= [HW,CD]
975 mce [IA-32] Machine Check Exception
977 md= [HW] RAID subsystems devices and level
978 See Documentation/md.txt.
980 mdacon= [MDA]
981 Format: <first>,<last>
982 Specifies range of consoles to be captured by the MDA.
984 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
985 Amount of memory to be used when the kernel is not able
986 to see the whole system memory or for test.
987 [IA-32] Use together with memmap= to avoid physical
988 address space collisions. Without memmap= PCI devices
989 could be placed at addresses belonging to unused RAM.
991 mem=nopentium [BUGS=IA-32] Disable usage of 4MB pages for kernel
992 memory.
994 memmap=exactmap [KNL,IA-32,X86_64] Enable setting of an exact
995 E820 memory map, as specified by the user.
996 Such memmap=exactmap lines can be constructed based on
997 BIOS output or other requirements. See the memmap=nn@ss
998 option description.
1000 memmap=nn[KMG]@ss[KMG]
1001 [KNL] Force usage of a specific region of memory
1002 Region of memory to be used, from ss to ss+nn.
1004 memmap=nn[KMG]#ss[KMG]
1005 [KNL,ACPI] Mark specific memory as ACPI data.
1006 Region of memory to be used, from ss to ss+nn.
1008 memmap=nn[KMG]$ss[KMG]
1009 [KNL,ACPI] Mark specific memory as reserved.
1010 Region of memory to be used, from ss to ss+nn.
1012 meye.*= [HW] Set MotionEye Camera parameters
1013 See Documentation/video4linux/meye.txt.
1015 mga= [HW,DRM]
1017 mousedev.tap_time=
1018 [MOUSE] Maximum time between finger touching and
1019 leaving touchpad surface for touch to be considered
1020 a tap and be reported as a left button click (for
1021 touchpads working in absolute mode only).
1022 Format: <msecs>
1023 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1024 reporting absolute coordinates, such as tablets
1025 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1026 reporting absolute coordinates, such as tablets
1028 mpu401= [HW,OSS]
1029 Format: <io>,<irq>
1031 MTD_Partition= [MTD]
1032 Format: <name>,<region-number>,<size>,<offset>
1034 MTD_Region= [MTD] Format:
1035 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1037 mtdparts= [MTD]
1038 See drivers/mtd/cmdline.c.
1040 mtouchusb.raw_coordinates=
1041 [HW] Make the MicroTouch USB driver use raw coordinates
1042 ('y', default) or cooked coordinates ('n')
1044 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1046 NCR_D700= [HW,SCSI]
1047 See header of drivers/scsi/NCR_D700.c.
1049 ncr5380= [HW,SCSI]
1051 ncr53c400= [HW,SCSI]
1053 ncr53c400a= [HW,SCSI]
1055 ncr53c406a= [HW,SCSI]
1057 ncr53c8xx= [HW,SCSI]
1059 netdev= [NET] Network devices parameters
1060 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1061 Note that mem_start is often overloaded to mean
1062 something different and driver-specific.
1063 This usage is only documented in each driver source
1064 file if at all.
1066 nfsaddrs= [NFS]
1067 See Documentation/nfsroot.txt.
1069 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1070 See Documentation/nfsroot.txt.
1072 nfs.callback_tcpport=
1073 [NFS] set the TCP port on which the NFSv4 callback
1074 channel should listen.
1076 nfs.idmap_cache_timeout=
1077 [NFS] set the maximum lifetime for idmapper cache
1078 entries.
1080 nmi_watchdog= [KNL,BUGS=IA-32] Debugging features for SMP kernels
1082 no387 [BUGS=IA-32] Tells the kernel to use the 387 maths
1083 emulation library even if a 387 maths coprocessor
1084 is present.
1086 noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1087 when set.
1088 Format: <int>
1090 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1091 caches in the slab allocator. Saves per-node memory,
1092 but will impact performance.
1094 noalign [KNL,ARM]
1096 noapic [SMP,APIC] Tells the kernel to not make use of any
1097 IOAPICs that may be present in the system.
1099 noasync [HW,M68K] Disables async and sync negotiation for
1100 all devices.
1102 nobats [PPC] Do not use BATs for mapping kernel lowmem
1103 on "Classic" PPC cores.
1105 nocache [ARM]
1107 nodelayacct [KNL] Disable per-task delay accounting
1109 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1111 noexec [IA-64]
1113 noexec [IA-32,X86-64]
1114 noexec=on: enable non-executable mappings (default)
1115 noexec=off: disable nn-executable mappings
1117 nofxsr [BUGS=IA-32] Disables x86 floating point extended
1118 register save and restore. The kernel will only save
1119 legacy floating-point registers on task switch.
1121 nohlt [BUGS=ARM]
1123 no-hlt [BUGS=IA-32] Tells the kernel that the hlt
1124 instruction doesn't work correctly and not to
1125 use it.
1127 nohalt [IA-64] Tells the kernel not to use the power saving
1128 function PAL_HALT_LIGHT when idle. This increases
1129 power-consumption. On the positive side, it reduces
1130 interrupt wake-up latency, which may improve performance
1131 in certain environments such as networked servers or
1132 real-time systems.
1134 nohz= [KNL] Boottime enable/disable dynamic ticks
1135 Valid arguments: on, off
1136 Default: on
1138 noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing
1140 noirqdebug [IA-32] Disables the code which attempts to detect and
1141 disable unhandled interrupt sources.
1143 no_timer_check [IA-32,X86_64,APIC] Disables the code which tests for
1144 broken timer IRQ sources.
1146 noisapnp [ISAPNP] Disables ISA PnP code.
1148 noinitrd [RAM] Tells the kernel not to load any configured
1149 initial RAM disk.
1151 nointroute [IA-64]
1153 nolapic [IA-32,APIC] Do not enable or use the local APIC.
1155 nolapic_timer [IA-32,APIC] Do not use the local APIC timer.
1157 noltlbs [PPC] Do not use large page/tlb entries for kernel
1158 lowmem mapping on PPC40x.
1160 nomca [IA-64] Disable machine check abort handling
1162 nomce [IA-32] Machine Check Exception
1164 noreplace-paravirt [IA-32,PV_OPS] Don't patch paravirt_ops
1166 noreplace-smp [IA-32,SMP] Don't replace SMP instructions
1167 with UP alternatives
1169 noresidual [PPC] Don't use residual data on PReP machines.
1171 noresume [SWSUSP] Disables resume and restores original swap
1172 space.
1174 no-scroll [VGA] Disables scrollback.
1175 This is required for the Braillex ib80-piezo Braille
1176 reader made by F.H. Papenmeier (Germany).
1178 nosbagart [IA-64]
1180 nosep [BUGS=IA-32] Disables x86 SYSENTER/SYSEXIT support.
1182 nosmp [SMP] Tells an SMP kernel to act as a UP kernel.
1184 nosync [HW,M68K] Disables sync negotiation for all devices.
1186 notsc [BUGS=IA-32] Disable Time Stamp Counter
1188 nousb [USB] Disable the USB subsystem
1190 nowb [ARM]
1192 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1194 opl3= [HW,OSS]
1195 Format: <io>
1197 opl3sa2= [HW,OSS] Format:
1198 <io>,<irq>,<dma>,<dma2>,<mss_io>,<mpu_io>,<ymode>,<loopback>[,<isapnp>,<multiple]
1200 oprofile.timer= [HW]
1201 Use timer interrupt instead of performance counters
1203 optcd= [HW,CD]
1204 Format: <io>
1206 osst= [HW,SCSI] SCSI Tape Driver
1207 Format: <buffer_size>,<write_threshold>
1208 See also Documentation/scsi/st.txt.
1210 panic= [KNL] Kernel behaviour on panic
1211 Format: <timeout>
1213 parkbd.port= [HW] Parallel port number the keyboard adapter is
1214 connected to, default is 0.
1215 Format: <parport#>
1216 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1217 0 for XT, 1 for AT (default is AT).
1218 Format: <mode>
1220 parport= [HW,PPT] Specify parallel ports. 0 disables.
1221 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1222 Use 'auto' to force the driver to use any
1223 IRQ/DMA settings detected (the default is to
1224 ignore detected IRQ/DMA settings because of
1225 possible conflicts). You can specify the base
1226 address, IRQ, and DMA settings; IRQ and DMA
1227 should be numbers, or 'auto' (for using detected
1228 settings on that particular port), or 'nofifo'
1229 (to avoid using a FIFO even if it is detected).
1230 Parallel ports are assigned in the order they
1231 are specified on the command line, starting
1232 with parport0.
1234 parport_init_mode= [HW,PPT]
1235 Configure VIA parallel port to operate in
1236 a specific mode. This is necessary on Pegasos
1237 computer where firmware has no options for setting
1238 up parallel port mode and sets it to spp.
1239 Currently this function knows 686a and 8231 chips.
1240 Format: [spp|ps2|epp|ecp|ecpepp]
1242 pas2= [HW,OSS] Format:
1243 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1245 pas16= [HW,SCSI]
1246 See header of drivers/scsi/pas16.c.
1248 pause_on_oops=
1249 Halt all CPUs after the first oops has been printed for
1250 the specified number of seconds. This is to be used if
1251 your oopses keep scrolling off the screen.
1253 pcbit= [HW,ISDN]
1255 pcd. [PARIDE]
1256 See header of drivers/block/paride/pcd.c.
1257 See also Documentation/paride.txt.
1259 pci=option[,option...] [PCI] various PCI subsystem options:
1260 off [IA-32] don't probe for the PCI bus
1261 bios [IA-32] force use of PCI BIOS, don't access
1262 the hardware directly. Use this if your machine
1263 has a non-standard PCI host bridge.
1264 nobios [IA-32] disallow use of PCI BIOS, only direct
1265 hardware access methods are allowed. Use this
1266 if you experience crashes upon bootup and you
1267 suspect they are caused by the BIOS.
1268 conf1 [IA-32] Force use of PCI Configuration
1269 Mechanism 1.
1270 conf2 [IA-32] Force use of PCI Configuration
1271 Mechanism 2.
1272 nommconf [IA-32,X86_64] Disable use of MMCONFIG for PCI
1273 Configuration
1274 nomsi [MSI] If the PCI_MSI kernel config parameter is
1275 enabled, this kernel boot option can be used to
1276 disable the use of MSI interrupts system-wide.
1277 nosort [IA-32] Don't sort PCI devices according to
1278 order given by the PCI BIOS. This sorting is
1279 done to get a device order compatible with
1280 older kernels.
1281 biosirq [IA-32] Use PCI BIOS calls to get the interrupt
1282 routing table. These calls are known to be buggy
1283 on several machines and they hang the machine
1284 when used, but on other computers it's the only
1285 way to get the interrupt routing table. Try
1286 this option if the kernel is unable to allocate
1287 IRQs or discover secondary PCI buses on your
1288 motherboard.
1289 rom [IA-32] Assign address space to expansion ROMs.
1290 Use with caution as certain devices share
1291 address decoders between ROMs and other
1292 resources.
1293 irqmask=0xMMMM [IA-32] Set a bit mask of IRQs allowed to be
1294 assigned automatically to PCI devices. You can
1295 make the kernel exclude IRQs of your ISA cards
1296 this way.
1297 pirqaddr=0xAAAAA [IA-32] Specify the physical address
1298 of the PIRQ table (normally generated
1299 by the BIOS) if it is outside the
1300 F0000h-100000h range.
1301 lastbus=N [IA-32] Scan all buses thru bus #N. Can be
1302 useful if the kernel is unable to find your
1303 secondary buses and you want to tell it
1304 explicitly which ones they are.
1305 assign-busses [IA-32] Always assign all PCI bus
1306 numbers ourselves, overriding
1307 whatever the firmware may have done.
1308 usepirqmask [IA-32] Honor the possible IRQ mask stored
1309 in the BIOS $PIR table. This is needed on
1310 some systems with broken BIOSes, notably
1311 some HP Pavilion N5400 and Omnibook XE3
1312 notebooks. This will have no effect if ACPI
1313 IRQ routing is enabled.
1314 noacpi [IA-32] Do not use ACPI for IRQ routing
1315 or for PCI scanning.
1316 routeirq Do IRQ routing for all PCI devices.
1317 This is normally done in pci_enable_device(),
1318 so this option is a temporary workaround
1319 for broken drivers that don't call it.
1320 firmware [ARM] Do not re-enumerate the bus but instead
1321 just use the configuration from the
1322 bootloader. This is currently used on
1323 IXP2000 systems where the bus has to be
1324 configured a certain way for adjunct CPUs.
1325 noearly [X86] Don't do any early type 1 scanning.
1326 This might help on some broken boards which
1327 machine check when some devices' config space
1328 is read. But various workarounds are disabled
1329 and some IOMMU drivers will not work.
1330 bfsort Sort PCI devices into breadth-first order.
1331 This sorting is done to get a device
1332 order compatible with older (<= 2.4) kernels.
1333 nobfsort Don't sort PCI devices into breadth-first order.
1334 cbiosize=nn[KMG] The fixed amount of bus space which is
1335 reserved for the CardBus bridge's IO window.
1336 The default value is 256 bytes.
1337 cbmemsize=nn[KMG] The fixed amount of bus space which is
1338 reserved for the CardBus bridge's memory
1339 window. The default value is 64 megabytes.
1341 pcmv= [HW,PCMCIA] BadgePAD 4
1343 pd. [PARIDE]
1344 See Documentation/paride.txt.
1346 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1347 boot time.
1348 Format: { 0 | 1 }
1349 See arch/parisc/kernel/pdc_chassis.c
1351 pf. [PARIDE]
1352 See Documentation/paride.txt.
1354 pg. [PARIDE]
1355 See Documentation/paride.txt.
1357 pirq= [SMP,APIC] Manual mp-table setup
1358 See Documentation/i386/IO-APIC.txt.
1360 plip= [PPT,NET] Parallel port network link
1361 Format: { parport<nr> | timid | 0 }
1362 See also Documentation/parport.txt.
1364 pnpacpi= [ACPI]
1365 { off }
1367 pnpbios= [ISAPNP]
1368 { on | off | curr | res | no-curr | no-res }
1370 pnp_reserve_irq=
1371 [ISAPNP] Exclude IRQs for the autoconfiguration
1373 pnp_reserve_dma=
1374 [ISAPNP] Exclude DMAs for the autoconfiguration
1376 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1377 Ranges are in pairs (I/O port base and size).
1379 pnp_reserve_mem=
1380 [ISAPNP] Exclude memory regions for the
1381 autoconfiguration.
1382 Ranges are in pairs (memory base and size).
1384 profile= [KNL] Enable kernel profiling via /proc/profile
1385 Format: [schedule,]<number>
1386 Param: "schedule" - profile schedule points.
1387 Param: <number> - step/bucket size as a power of 2 for
1388 statistical time based profiling.
1389 Param: "sleep" - profile D-state sleeping (millisecs)
1391 processor.max_cstate= [HW,ACPI]
1392 Limit processor to maximum C-state
1393 max_cstate=9 overrides any DMI blacklist limit.
1395 processor.nocst [HW,ACPI]
1396 Ignore the _CST method to determine C-states,
1397 instead using the legacy FADT method
1399 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1400 before loading.
1401 See Documentation/ramdisk.txt.
1403 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1404 probe for; one of (bare|imps|exps|lifebook|any).
1405 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1406 per second.
1407 psmouse.resetafter= [HW,MOUSE]
1408 Try to reset the device after so many bad packets
1409 (0 = never).
1410 psmouse.resolution=
1411 [HW,MOUSE] Set desired mouse resolution, in dpi.
1412 psmouse.smartscroll=
1413 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1414 0 = disabled, 1 = enabled (default).
1416 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1417 Format:
1418 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1420 pt. [PARIDE]
1421 See Documentation/paride.txt.
1423 quiet [KNL] Disable most log messages
1425 r128= [HW,DRM]
1427 raid= [HW,RAID]
1428 See Documentation/md.txt.
1430 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1431 See Documentation/ramdisk.txt.
1433 ramdisk_blocksize= [RAM]
1434 See Documentation/ramdisk.txt.
1436 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1437 New name for the ramdisk parameter.
1438 See Documentation/ramdisk.txt.
1440 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1441 RCU callbacks to process in one batch.
1443 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1444 RCU callbacks over which batch limiting is disabled.
1446 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1447 RCU callbacks below which batch limiting is re-enabled.
1449 rdinit= [KNL]
1450 Format: <full_path>
1451 Run specified binary instead of /init from the ramdisk,
1452 used for early userspace startup. See initrd.
1454 reboot= [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1455 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1456 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1458 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1460 reservetop= [IA-32]
1461 Format: nn[KMG]
1462 Reserves a hole at the top of the kernel virtual
1463 address space.
1465 reset_devices [KNL] Force drivers to reset the underlying device
1466 during initialization.
1468 resume= [SWSUSP]
1469 Specify the partition device for software suspend
1471 resume_offset= [SWSUSP]
1472 Specify the offset from the beginning of the partition
1473 given by "resume=" at which the swap header is located,
1474 in <PAGE_SIZE> units (needed only for swap files).
1475 See Documentation/power/swsusp-and-swap-files.txt
1477 retain_initrd [RAM] Keep initrd memory after extraction
1479 rhash_entries= [KNL,NET]
1480 Set number of hash buckets for route cache
1482 riscom8= [HW,SERIAL]
1483 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1485 ro [KNL] Mount root device read-only on boot
1487 root= [KNL] Root filesystem
1489 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1490 mount the root filesystem
1492 rootflags= [KNL] Set root filesystem mount option string
1494 rootfstype= [KNL] Set root filesystem type
1496 rw [KNL] Mount root device read-write on boot
1498 S [KNL] Run init in single mode
1500 sa1100ir [NET]
1501 See drivers/net/irda/sa1100_ir.c.
1503 sb= [HW,OSS]
1504 Format: <io>,<irq>,<dma>,<dma2>
1506 sbni= [NET] Granch SBNI12 leased line adapter
1508 sbpcd= [HW,CD] Soundblaster CD adapter
1509 Format: <io>,<type>
1510 See a comment before function sbpcd_setup() in
1511 drivers/cdrom/sbpcd.c.
1513 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1514 Format: <io>[,<timeout>[,<isapnp>]]
1516 scsi_debug_*= [SCSI]
1517 See drivers/scsi/scsi_debug.c.
1519 scsi_default_dev_flags=
1520 [SCSI] SCSI default device flags
1521 Format: <integer>
1523 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1524 Format: <vendor>:<model>:<flags>
1525 (flags are integer value)
1527 scsi_logging= [SCSI]
1529 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1530 discovered. async scans them in kernel threads,
1531 allowing boot to proceed. none ignores them, expecting
1532 user space to do the scan.
1534 selinux [SELINUX] Disable or enable SELinux at boot time.
1535 Format: { "0" | "1" }
1536 See security/selinux/Kconfig help text.
1537 0 -- disable.
1538 1 -- enable.
1539 Default value is set via kernel config option.
1540 If enabled at boot time, /selinux/disable can be used
1541 later to disable prior to initial policy load.
1543 selinux_compat_net =
1544 [SELINUX] Set initial selinux_compat_net flag value.
1545 Format: { "0" | "1" }
1546 0 -- use new secmark-based packet controls
1547 1 -- use legacy packet controls
1548 Default value is 0 (preferred).
1549 Value can be changed at runtime via
1550 /selinux/compat_net.
1552 serialnumber [BUGS=IA-32]
1554 sg_def_reserved_size= [SCSI]
1556 shapers= [NET]
1557 Maximal number of shapers.
1559 sim710= [SCSI,HW]
1560 See header of drivers/scsi/sim710.c.
1562 simeth= [IA-64]
1563 simscsi=
1565 sjcd= [HW,CD]
1566 Format: <io>,<irq>,<dma>
1567 See header of drivers/cdrom/sjcd.c.
1569 slram= [HW,MTD]
1571 slub_debug [MM, SLUB]
1572 Enabling slub_debug allows one to determine the culprit
1573 if slab objects become corrupted. Enabling slub_debug
1574 creates guard zones around objects and poisons objects
1575 when not in use. Also tracks the last alloc / free.
1576 For more information see Documentation/vm/slub.txt.
1578 slub_max_order= [MM, SLUB]
1579 Determines the maximum allowed order for slabs. Setting
1580 this too high may cause fragmentation.
1581 For more information see Documentation/vm/slub.txt.
1583 slub_min_objects= [MM, SLUB]
1584 The minimum objects per slab. SLUB will increase the
1585 slab order up to slub_max_order to generate a
1586 sufficiently big slab to satisfy the number of objects.
1587 The higher the number of objects the smaller the overhead
1588 of tracking slabs.
1589 For more information see Documentation/vm/slub.txt.
1591 slub_min_order= [MM, SLUB]
1592 Determines the mininum page order for slabs. Must be
1593 lower than slub_max_order
1594 For more information see Documentation/vm/slub.txt.
1596 slub_nomerge [MM, SLUB]
1597 Disable merging of slabs of similar size. May be
1598 necessary if there is some reason to distinguish
1599 allocs to different slabs.
1600 For more information see Documentation/vm/slub.txt.
1602 smart2= [HW]
1603 Format: <io1>[,<io2>[,...,<io8>]]
1605 smp-alt-once [IA-32,SMP] On a hotplug CPU system, only
1606 attempt to substitute SMP alternatives once at boot.
1608 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1609 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1610 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1611 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1612 smsc-ircc2.ircc_irq= [HW] IRQ line
1613 smsc-ircc2.ircc_dma= [HW] DMA channel
1614 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1615 0: Toshiba Satellite 1800 (GP data pin select)
1616 1: Fast pin select (default)
1617 2: ATC IRMode
1619 snd-ad1816a= [HW,ALSA]
1621 snd-ad1848= [HW,ALSA]
1623 snd-ali5451= [HW,ALSA]
1625 snd-als100= [HW,ALSA]
1627 snd-als4000= [HW,ALSA]
1629 snd-azt2320= [HW,ALSA]
1631 snd-cmi8330= [HW,ALSA]
1633 snd-cmipci= [HW,ALSA]
1635 snd-cs4231= [HW,ALSA]
1637 snd-cs4232= [HW,ALSA]
1639 snd-cs4236= [HW,ALSA]
1641 snd-cs4281= [HW,ALSA]
1643 snd-cs46xx= [HW,ALSA]
1645 snd-dt019x= [HW,ALSA]
1647 snd-dummy= [HW,ALSA]
1649 snd-emu10k1= [HW,ALSA]
1651 snd-ens1370= [HW,ALSA]
1653 snd-ens1371= [HW,ALSA]
1655 snd-es968= [HW,ALSA]
1657 snd-es1688= [HW,ALSA]
1659 snd-es18xx= [HW,ALSA]
1661 snd-es1938= [HW,ALSA]
1663 snd-es1968= [HW,ALSA]
1665 snd-fm801= [HW,ALSA]
1667 snd-gusclassic= [HW,ALSA]
1669 snd-gusextreme= [HW,ALSA]
1671 snd-gusmax= [HW,ALSA]
1673 snd-hdsp= [HW,ALSA]
1675 snd-ice1712= [HW,ALSA]
1677 snd-intel8x0= [HW,ALSA]
1679 snd-interwave= [HW,ALSA]
1681 snd-interwave-stb=
1682 [HW,ALSA]
1684 snd-korg1212= [HW,ALSA]
1686 snd-maestro3= [HW,ALSA]
1688 snd-mpu401= [HW,ALSA]
1690 snd-mtpav= [HW,ALSA]
1692 snd-nm256= [HW,ALSA]
1694 snd-opl3sa2= [HW,ALSA]
1696 snd-opti92x-ad1848=
1697 [HW,ALSA]
1699 snd-opti92x-cs4231=
1700 [HW,ALSA]
1702 snd-opti93x= [HW,ALSA]
1704 snd-pmac= [HW,ALSA]
1706 snd-rme32= [HW,ALSA]
1708 snd-rme96= [HW,ALSA]
1710 snd-rme9652= [HW,ALSA]
1712 snd-sb8= [HW,ALSA]
1714 snd-sb16= [HW,ALSA]
1716 snd-sbawe= [HW,ALSA]
1718 snd-serial= [HW,ALSA]
1720 snd-sgalaxy= [HW,ALSA]
1722 snd-sonicvibes= [HW,ALSA]
1724 snd-sun-amd7930=
1725 [HW,ALSA]
1727 snd-sun-cs4231= [HW,ALSA]
1729 snd-trident= [HW,ALSA]
1731 snd-usb-audio= [HW,ALSA,USB]
1733 snd-via82xx= [HW,ALSA]
1735 snd-virmidi= [HW,ALSA]
1737 snd-wavefront= [HW,ALSA]
1739 snd-ymfpci= [HW,ALSA]
1741 sonycd535= [HW,CD]
1742 Format: <io>[,<irq>]
1744 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1745 See Documentation/sonypi.txt
1747 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1748 See Documentation/specialix.txt.
1750 spia_io_base= [HW,MTD]
1751 spia_fio_base=
1752 spia_pedr=
1753 spia_peddr=
1755 sscape= [HW,OSS]
1756 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1758 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1759 See Documentation/scsi/st.txt.
1761 st0x= [HW,SCSI]
1762 See header of drivers/scsi/seagate.c.
1764 sti= [PARISC,HW]
1765 Format: <num>
1766 Set the STI (builtin display/keyboard on the HP-PARISC
1767 machines) console (graphic card) which should be used
1768 as the initial boot-console.
1769 See also comment in drivers/video/console/sticore.c.
1771 sti_font= [HW]
1772 See comment in drivers/video/console/sticore.c.
1774 stifb= [HW]
1775 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1777 sunrpc.pool_mode=
1778 [NFS]
1779 Control how the NFS server code allocates CPUs to
1780 service thread pools. Depending on how many NICs
1781 you have and where their interrupts are bound, this
1782 option will affect which CPUs will do NFS serving.
1783 Note: this parameter cannot be changed while the
1784 NFS server is running.
1786 auto the server chooses an appropriate mode
1787 automatically using heuristics
1788 global a single global pool contains all CPUs
1789 percpu one pool for each CPU
1790 pernode one pool for each NUMA node (equivalent
1791 to global on non-NUMA machines)
1793 swiotlb= [IA-64] Number of I/O TLB slabs
1795 switches= [HW,M68k]
1797 sym53c416= [HW,SCSI]
1798 See header of drivers/scsi/sym53c416.c.
1800 sysrq_always_enabled
1801 [KNL]
1802 Ignore sysrq setting - this boot parameter will
1803 neutralize any effect of /proc/sys/kernel/sysrq.
1804 Useful for debugging.
1806 t128= [HW,SCSI]
1807 See header of drivers/scsi/t128.c.
1809 tdfx= [HW,DRM]
1811 thash_entries= [KNL,NET]
1812 Set number of hash buckets for TCP connection
1814 time Show timing data prefixed to each printk message line
1816 tipar.timeout= [HW,PPT]
1817 Set communications timeout in tenths of a second
1818 (default 15).
1820 tipar.delay= [HW,PPT]
1821 Set inter-bit delay in microseconds (default 10).
1823 tmc8xx= [HW,SCSI]
1824 See header of drivers/scsi/seagate.c.
1826 tmscsim= [HW,SCSI]
1827 See comment before function dc390_setup() in
1828 drivers/scsi/tmscsim.c.
1830 tp720= [HW,PS2]
1832 trix= [HW,OSS] MediaTrix AudioTrix Pro
1833 Format:
1834 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1836 tsdev.xres= [TS] Horizontal screen resolution.
1837 tsdev.yres= [TS] Vertical screen resolution.
1839 turbografx.map[2|3]= [HW,JOY]
1840 TurboGraFX parallel port interface
1841 Format:
1842 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1843 See also Documentation/input/joystick-parport.txt
1845 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1846 See header of drivers/scsi/u14-34f.c.
1848 uart401= [HW,OSS]
1849 Format: <io>,<irq>
1851 uart6850= [HW,OSS]
1852 Format: <io>,<irq>
1854 uhci-hcd.ignore_oc=
1855 [USB] Ignore overcurrent events (default N).
1856 Some badly-designed motherboards generate lots of
1857 bogus events, for ports that aren't wired to
1858 anything. Set this parameter to avoid log spamming.
1859 Note that genuine overcurrent events won't be
1860 reported either.
1862 usbcore.autosuspend=
1863 [USB] The autosuspend time delay (in seconds) used
1864 for newly-detected USB devices (default 2). This
1865 is the time required before an idle device will be
1866 autosuspended. Devices for which the delay is set
1867 to a negative value won't be autosuspended at all.
1869 usbhid.mousepoll=
1870 [USBHID] The interval which mice are to be polled at.
1872 vdso= [IA-32,SH]
1873 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1874 vdso=1: enable VDSO (default)
1875 vdso=0: disable VDSO mapping
1877 video= [FB] Frame buffer configuration
1878 See Documentation/fb/modedb.txt.
1880 vga= [BOOT,IA-32] Select a particular video mode
1881 See Documentation/i386/boot.txt and
1882 Documentation/svga.txt.
1883 Use vga=ask for menu.
1884 This is actually a boot loader parameter; the value is
1885 passed to the kernel using a special protocol.
1887 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1888 size of <nn>. This can be used to increase the
1889 minimum size (128MB on x86). It can also be used to
1890 decrease the size and leave more room for directly
1891 mapped kernel RAM.
1893 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1894 Format: <command>
1896 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1897 Format: <command>
1899 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1900 Format: <command>
1902 waveartist= [HW,OSS]
1903 Format: <io>,<irq>,<dma>,<dma2>
1905 wd33c93= [HW,SCSI]
1906 See header of drivers/scsi/wd33c93.c.
1908 wd7000= [HW,SCSI]
1909 See header of drivers/scsi/wd7000.c.
1911 wdt= [WDT] Watchdog
1912 See Documentation/watchdog/watchdog.txt.
1914 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1915 xd_geo= See header of drivers/block/xd.c.
1917 xirc2ps_cs= [NET,PCMCIA]
1918 Format:
1919 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1921 norandmaps Don't use address space randomization
1922 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1924 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1925 This is useful to get more information why
1926 you got a "dwarf2 unwinder stuck"
1928 ______________________________________________________________________
1930 TODO:
1932 Add documentation for ALSA options.
1933 Add more DRM drivers.