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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 ad1848= [HW,OSS]
242 Format: <io>,<irq>,<dma>,<dma2>,<type>
244 advansys= [HW,SCSI]
245 See header of drivers/scsi/advansys.c.
247 advwdt= [HW,WDT] Advantech WDT
248 Format: <iostart>,<iostop>
250 aedsp16= [HW,OSS] Audio Excel DSP 16
251 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
252 See also header of sound/oss/aedsp16.c.
254 aha152x= [HW,SCSI]
255 See Documentation/scsi/aha152x.txt.
257 aha1542= [HW,SCSI]
258 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
260 aic7xxx= [HW,SCSI]
261 See Documentation/scsi/aic7xxx.txt.
263 aic79xx= [HW,SCSI]
264 See Documentation/scsi/aic79xx.txt.
266 amijoy.map= [HW,JOY] Amiga joystick support
267 Map of devices attached to JOY0DAT and JOY1DAT
268 Format: <a>,<b>
269 See also Documentation/kernel/input/joystick.txt
271 analog.map= [HW,JOY] Analog joystick and gamepad support
272 Specifies type or capabilities of an analog joystick
273 connected to one of 16 gameports
274 Format: <type1>,<type2>,..<type16>
276 apc= [HW,SPARC]
277 Power management functions (SPARCstation-4/5 + deriv.)
278 Format: noidle
279 Disable APC CPU standby support. SPARCstation-Fox does
280 not play well with APC CPU idle - disable it if you have
281 APC and your system crashes randomly.
283 apic= [APIC,i386] Change the output verbosity whilst booting
284 Format: { quiet (default) | verbose | debug }
285 Change the amount of debugging information output
286 when initialising the APIC and IO-APIC components.
288 apm= [APM] Advanced Power Management
289 See header of arch/i386/kernel/apm.c.
291 applicom= [HW]
292 Format: <mem>,<irq>
294 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
295 Format: <io>,<irq>,<nodeID>
297 ataflop= [HW,M68k]
299 atarimouse= [HW,MOUSE] Atari Mouse
301 atascsi= [HW,SCSI] Atari SCSI
303 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
304 EzKey and similar keyboards
306 atkbd.reset= [HW] Reset keyboard during initialization
308 atkbd.set= [HW] Select keyboard code set
309 Format: <int> (2 = AT (default), 3 = PS/2)
311 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
312 keyboards
314 atkbd.softraw= [HW] Choose between synthetic and real raw mode
315 Format: <bool> (0 = real, 1 = synthetic (default))
317 atkbd.softrepeat= [HW]
318 Use software keyboard repeat
320 autotest [IA64]
322 aztcd= [HW,CD] Aztech CD268 CDROM driver
323 Format: <io>,0x79 (?)
325 baycom_epp= [HW,AX25]
326 Format: <io>,<mode>
328 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
329 Format: <io>,<mode>
330 See header of drivers/net/hamradio/baycom_par.c.
332 baycom_ser_fdx= [HW,AX25]
333 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
334 Format: <io>,<irq>,<mode>[,<baud>]
335 See header of drivers/net/hamradio/baycom_ser_fdx.c.
337 baycom_ser_hdx= [HW,AX25]
338 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
339 Format: <io>,<irq>,<mode>
340 See header of drivers/net/hamradio/baycom_ser_hdx.c.
342 blkmtd_device= [HW,MTD]
343 blkmtd_erasesz=
344 blkmtd_ro=
345 blkmtd_bs=
346 blkmtd_count=
348 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
349 bttv.radio= Most important insmod options are available as
350 kernel args too.
351 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
352 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
354 BusLogic= [HW,SCSI]
355 See drivers/scsi/BusLogic.c, comment before function
356 BusLogic_ParseDriverOptions().
358 c101= [NET] Moxa C101 synchronous serial card
360 cachesize= [BUGS=IA-32] Override level 2 CPU cache size detection.
361 Sometimes CPU hardware bugs make them report the cache
362 size incorrectly. The kernel will attempt work arounds
363 to fix known problems, but for some CPUs it is not
364 possible to determine what the correct size should be.
365 This option provides an override for these situations.
367 cdu31a= [HW,CD]
368 Format: <io>,<irq>[,PAS]
369 See header of drivers/cdrom/cdu31a.c.
371 chandev= [HW,NET] Generic channel device initialisation
373 checkreqprot [SELINUX] Set initial checkreqprot flag value.
374 Format: { "0" | "1" }
375 See security/selinux/Kconfig help text.
376 0 -- check protection applied by kernel (includes
377 any implied execute protection).
378 1 -- check protection requested by application.
379 Default value is set via a kernel config option.
380 Value can be changed at runtime via
381 /selinux/checkreqprot.
383 clock= [BUGS=IA-32, HW] gettimeofday clocksource override.
384 [Deprecated]
385 Forces specified clocksource (if available) to be used
386 when calculating gettimeofday(). If specified
387 clocksource is not available, it defaults to PIT.
388 Format: { pit | tsc | cyclone | pmtmr }
390 clocksource= [GENERIC_TIME] Override the default clocksource
391 Format: <string>
392 Override the default clocksource and use the clocksource
393 with the name specified.
394 Some clocksource names to choose from, depending on
395 the platform:
396 [all] jiffies (this is the base, fallback clocksource)
397 [ACPI] acpi_pm
398 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
399 pxa_timer,timer3,32k_counter,timer0_1
400 [AVR32] avr32
401 [IA-32] pit,hpet,tsc,vmi-timer;
402 scx200_hrt on Geode; cyclone on IBM x440
403 [MIPS] MIPS
404 [PARISC] cr16
405 [S390] tod
406 [SH] SuperH
407 [SPARC64] tick
408 [X86-64] hpet,tsc
410 code_bytes [IA32] How many bytes of object code to print in an
411 oops report.
412 Range: 0 - 8192
413 Default: 64
415 disable_8254_timer
416 enable_8254_timer
417 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
418 over the 8254 in addition to over the IO-APIC. The
419 kernel tries to set a sensible default.
421 hpet= [IA-32,HPET] option to disable HPET and use PIT.
422 Format: disable
424 cm206= [HW,CD]
425 Format: { auto | [<io>,][<irq>] }
427 com20020= [HW,NET] ARCnet - COM20020 chipset
428 Format:
429 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
431 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
432 Format: <io>[,<irq>]
434 com90xx= [HW,NET]
435 ARCnet - COM90xx chipset (memory-mapped buffers)
436 Format: <io>[,<irq>[,<memstart>]]
438 condev= [HW,S390] console device
439 conmode=
441 console= [KNL] Output console device and options.
443 tty<n> Use the virtual console device <n>.
445 ttyS<n>[,options]
446 ttyUSB0[,options]
447 Use the specified serial port. The options are of
448 the form "bbbbpnf", where "bbbb" is the baud rate,
449 "p" is parity ("n", "o", or "e"), "n" is number of
450 bits, and "f" is flow control ("r" for RTS or
451 omit it). Default is "9600n8".
453 See Documentation/serial-console.txt for more
454 information. See
455 Documentation/networking/netconsole.txt for an
456 alternative.
458 uart[8250],io,<addr>[,options]
459 uart[8250],mmio,<addr>[,options]
460 Start an early, polled-mode console on the 8250/16550
461 UART at the specified I/O port or MMIO address,
462 switching to the matching ttyS device later. The
463 options are the same as for ttyS, above.
465 earlycon= [KNL] Output early console device and options.
466 uart[8250],io,<addr>[,options]
467 uart[8250],mmio,<addr>[,options]
468 Start an early, polled-mode console on the 8250/16550
469 UART at the specified I/O port or MMIO address.
470 The 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 nosoftlockup [KNL] Disable the soft-lockup detector.
1186 nosync [HW,M68K] Disables sync negotiation for all devices.
1188 notsc [BUGS=IA-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 optcd= [HW,CD]
1208 Format: <io>
1210 osst= [HW,SCSI] SCSI Tape Driver
1211 Format: <buffer_size>,<write_threshold>
1212 See also Documentation/scsi/st.txt.
1214 panic= [KNL] Kernel behaviour on panic
1215 Format: <timeout>
1217 parkbd.port= [HW] Parallel port number the keyboard adapter is
1218 connected to, default is 0.
1219 Format: <parport#>
1220 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1221 0 for XT, 1 for AT (default is AT).
1222 Format: <mode>
1224 parport= [HW,PPT] Specify parallel ports. 0 disables.
1225 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1226 Use 'auto' to force the driver to use any
1227 IRQ/DMA settings detected (the default is to
1228 ignore detected IRQ/DMA settings because of
1229 possible conflicts). You can specify the base
1230 address, IRQ, and DMA settings; IRQ and DMA
1231 should be numbers, or 'auto' (for using detected
1232 settings on that particular port), or 'nofifo'
1233 (to avoid using a FIFO even if it is detected).
1234 Parallel ports are assigned in the order they
1235 are specified on the command line, starting
1236 with parport0.
1238 parport_init_mode= [HW,PPT]
1239 Configure VIA parallel port to operate in
1240 a specific mode. This is necessary on Pegasos
1241 computer where firmware has no options for setting
1242 up parallel port mode and sets it to spp.
1243 Currently this function knows 686a and 8231 chips.
1244 Format: [spp|ps2|epp|ecp|ecpepp]
1246 pas2= [HW,OSS] Format:
1247 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1249 pas16= [HW,SCSI]
1250 See header of drivers/scsi/pas16.c.
1252 pause_on_oops=
1253 Halt all CPUs after the first oops has been printed for
1254 the specified number of seconds. This is to be used if
1255 your oopses keep scrolling off the screen.
1257 pcbit= [HW,ISDN]
1259 pcd. [PARIDE]
1260 See header of drivers/block/paride/pcd.c.
1261 See also Documentation/paride.txt.
1263 pci=option[,option...] [PCI] various PCI subsystem options:
1264 off [IA-32] don't probe for the PCI bus
1265 bios [IA-32] force use of PCI BIOS, don't access
1266 the hardware directly. Use this if your machine
1267 has a non-standard PCI host bridge.
1268 nobios [IA-32] disallow use of PCI BIOS, only direct
1269 hardware access methods are allowed. Use this
1270 if you experience crashes upon bootup and you
1271 suspect they are caused by the BIOS.
1272 conf1 [IA-32] Force use of PCI Configuration
1273 Mechanism 1.
1274 conf2 [IA-32] Force use of PCI Configuration
1275 Mechanism 2.
1276 nommconf [IA-32,X86_64] Disable use of MMCONFIG for PCI
1277 Configuration
1278 nomsi [MSI] If the PCI_MSI kernel config parameter is
1279 enabled, this kernel boot option can be used to
1280 disable the use of MSI interrupts system-wide.
1281 nosort [IA-32] Don't sort PCI devices according to
1282 order given by the PCI BIOS. This sorting is
1283 done to get a device order compatible with
1284 older kernels.
1285 biosirq [IA-32] Use PCI BIOS calls to get the interrupt
1286 routing table. These calls are known to be buggy
1287 on several machines and they hang the machine
1288 when used, but on other computers it's the only
1289 way to get the interrupt routing table. Try
1290 this option if the kernel is unable to allocate
1291 IRQs or discover secondary PCI buses on your
1292 motherboard.
1293 rom [IA-32] Assign address space to expansion ROMs.
1294 Use with caution as certain devices share
1295 address decoders between ROMs and other
1296 resources.
1297 irqmask=0xMMMM [IA-32] Set a bit mask of IRQs allowed to be
1298 assigned automatically to PCI devices. You can
1299 make the kernel exclude IRQs of your ISA cards
1300 this way.
1301 pirqaddr=0xAAAAA [IA-32] Specify the physical address
1302 of the PIRQ table (normally generated
1303 by the BIOS) if it is outside the
1304 F0000h-100000h range.
1305 lastbus=N [IA-32] Scan all buses thru bus #N. Can be
1306 useful if the kernel is unable to find your
1307 secondary buses and you want to tell it
1308 explicitly which ones they are.
1309 assign-busses [IA-32] Always assign all PCI bus
1310 numbers ourselves, overriding
1311 whatever the firmware may have done.
1312 usepirqmask [IA-32] Honor the possible IRQ mask stored
1313 in the BIOS $PIR table. This is needed on
1314 some systems with broken BIOSes, notably
1315 some HP Pavilion N5400 and Omnibook XE3
1316 notebooks. This will have no effect if ACPI
1317 IRQ routing is enabled.
1318 noacpi [IA-32] Do not use ACPI for IRQ routing
1319 or for PCI scanning.
1320 routeirq Do IRQ routing for all PCI devices.
1321 This is normally done in pci_enable_device(),
1322 so this option is a temporary workaround
1323 for broken drivers that don't call it.
1324 firmware [ARM] Do not re-enumerate the bus but instead
1325 just use the configuration from the
1326 bootloader. This is currently used on
1327 IXP2000 systems where the bus has to be
1328 configured a certain way for adjunct CPUs.
1329 noearly [X86] Don't do any early type 1 scanning.
1330 This might help on some broken boards which
1331 machine check when some devices' config space
1332 is read. But various workarounds are disabled
1333 and some IOMMU drivers will not work.
1334 bfsort Sort PCI devices into breadth-first order.
1335 This sorting is done to get a device
1336 order compatible with older (<= 2.4) kernels.
1337 nobfsort Don't sort PCI devices into breadth-first order.
1338 cbiosize=nn[KMG] The fixed amount of bus space which is
1339 reserved for the CardBus bridge's IO window.
1340 The default value is 256 bytes.
1341 cbmemsize=nn[KMG] The fixed amount of bus space which is
1342 reserved for the CardBus bridge's memory
1343 window. The default value is 64 megabytes.
1345 pcmv= [HW,PCMCIA] BadgePAD 4
1347 pd. [PARIDE]
1348 See Documentation/paride.txt.
1350 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1351 boot time.
1352 Format: { 0 | 1 }
1353 See arch/parisc/kernel/pdc_chassis.c
1355 pf. [PARIDE]
1356 See Documentation/paride.txt.
1358 pg. [PARIDE]
1359 See Documentation/paride.txt.
1361 pirq= [SMP,APIC] Manual mp-table setup
1362 See Documentation/i386/IO-APIC.txt.
1364 plip= [PPT,NET] Parallel port network link
1365 Format: { parport<nr> | timid | 0 }
1366 See also Documentation/parport.txt.
1368 pnpacpi= [ACPI]
1369 { off }
1371 pnpbios= [ISAPNP]
1372 { on | off | curr | res | no-curr | no-res }
1374 pnp_reserve_irq=
1375 [ISAPNP] Exclude IRQs for the autoconfiguration
1377 pnp_reserve_dma=
1378 [ISAPNP] Exclude DMAs for the autoconfiguration
1380 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1381 Ranges are in pairs (I/O port base and size).
1383 pnp_reserve_mem=
1384 [ISAPNP] Exclude memory regions for the
1385 autoconfiguration.
1386 Ranges are in pairs (memory base and size).
1388 print-fatal-signals=
1389 [KNL] debug: print fatal signals
1390 print-fatal-signals=1: print segfault info to
1391 the kernel console.
1392 default: off.
1394 printk.time= Show timing data prefixed to each printk message line
1395 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1397 profile= [KNL] Enable kernel profiling via /proc/profile
1398 Format: [schedule,]<number>
1399 Param: "schedule" - profile schedule points.
1400 Param: <number> - step/bucket size as a power of 2 for
1401 statistical time based profiling.
1402 Param: "sleep" - profile D-state sleeping (millisecs)
1404 processor.max_cstate= [HW,ACPI]
1405 Limit processor to maximum C-state
1406 max_cstate=9 overrides any DMI blacklist limit.
1408 processor.nocst [HW,ACPI]
1409 Ignore the _CST method to determine C-states,
1410 instead using the legacy FADT method
1412 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1413 before loading.
1414 See Documentation/ramdisk.txt.
1416 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1417 probe for; one of (bare|imps|exps|lifebook|any).
1418 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1419 per second.
1420 psmouse.resetafter= [HW,MOUSE]
1421 Try to reset the device after so many bad packets
1422 (0 = never).
1423 psmouse.resolution=
1424 [HW,MOUSE] Set desired mouse resolution, in dpi.
1425 psmouse.smartscroll=
1426 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1427 0 = disabled, 1 = enabled (default).
1429 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1430 Format:
1431 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1433 pt. [PARIDE]
1434 See Documentation/paride.txt.
1436 quiet [KNL] Disable most log messages
1438 r128= [HW,DRM]
1440 raid= [HW,RAID]
1441 See Documentation/md.txt.
1443 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1444 See Documentation/ramdisk.txt.
1446 ramdisk_blocksize= [RAM]
1447 See Documentation/ramdisk.txt.
1449 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1450 New name for the ramdisk parameter.
1451 See Documentation/ramdisk.txt.
1453 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1454 RCU callbacks to process in one batch.
1456 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1457 RCU callbacks over which batch limiting is disabled.
1459 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1460 RCU callbacks below which batch limiting is re-enabled.
1462 rdinit= [KNL]
1463 Format: <full_path>
1464 Run specified binary instead of /init from the ramdisk,
1465 used for early userspace startup. See initrd.
1467 reboot= [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1468 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1469 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1471 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1473 reservetop= [IA-32]
1474 Format: nn[KMG]
1475 Reserves a hole at the top of the kernel virtual
1476 address space.
1478 reset_devices [KNL] Force drivers to reset the underlying device
1479 during initialization.
1481 resume= [SWSUSP]
1482 Specify the partition device for software suspend
1484 resume_offset= [SWSUSP]
1485 Specify the offset from the beginning of the partition
1486 given by "resume=" at which the swap header is located,
1487 in <PAGE_SIZE> units (needed only for swap files).
1488 See Documentation/power/swsusp-and-swap-files.txt
1490 retain_initrd [RAM] Keep initrd memory after extraction
1492 rhash_entries= [KNL,NET]
1493 Set number of hash buckets for route cache
1495 riscom8= [HW,SERIAL]
1496 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1498 ro [KNL] Mount root device read-only on boot
1500 root= [KNL] Root filesystem
1502 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1503 mount the root filesystem
1505 rootflags= [KNL] Set root filesystem mount option string
1507 rootfstype= [KNL] Set root filesystem type
1509 rootwait [KNL] Wait (indefinitely) for root device to show up.
1510 Useful for devices that are detected asynchronously
1511 (e.g. USB and MMC devices).
1513 rw [KNL] Mount root device read-write on boot
1515 S [KNL] Run init in single mode
1517 sa1100ir [NET]
1518 See drivers/net/irda/sa1100_ir.c.
1520 sb= [HW,OSS]
1521 Format: <io>,<irq>,<dma>,<dma2>
1523 sbni= [NET] Granch SBNI12 leased line adapter
1525 sbpcd= [HW,CD] Soundblaster CD adapter
1526 Format: <io>,<type>
1527 See a comment before function sbpcd_setup() in
1528 drivers/cdrom/sbpcd.c.
1530 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1531 Format: <io>[,<timeout>[,<isapnp>]]
1533 scsi_debug_*= [SCSI]
1534 See drivers/scsi/scsi_debug.c.
1536 scsi_default_dev_flags=
1537 [SCSI] SCSI default device flags
1538 Format: <integer>
1540 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1541 Format: <vendor>:<model>:<flags>
1542 (flags are integer value)
1544 scsi_logging= [SCSI]
1546 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1547 discovered. async scans them in kernel threads,
1548 allowing boot to proceed. none ignores them, expecting
1549 user space to do the scan.
1551 selinux [SELINUX] Disable or enable SELinux at boot time.
1552 Format: { "0" | "1" }
1553 See security/selinux/Kconfig help text.
1554 0 -- disable.
1555 1 -- enable.
1556 Default value is set via kernel config option.
1557 If enabled at boot time, /selinux/disable can be used
1558 later to disable prior to initial policy load.
1560 selinux_compat_net =
1561 [SELINUX] Set initial selinux_compat_net flag value.
1562 Format: { "0" | "1" }
1563 0 -- use new secmark-based packet controls
1564 1 -- use legacy packet controls
1565 Default value is 0 (preferred).
1566 Value can be changed at runtime via
1567 /selinux/compat_net.
1569 serialnumber [BUGS=IA-32]
1571 sg_def_reserved_size= [SCSI]
1573 shapers= [NET]
1574 Maximal number of shapers.
1576 sim710= [SCSI,HW]
1577 See header of drivers/scsi/sim710.c.
1579 simeth= [IA-64]
1580 simscsi=
1582 sjcd= [HW,CD]
1583 Format: <io>,<irq>,<dma>
1584 See header of drivers/cdrom/sjcd.c.
1586 slram= [HW,MTD]
1588 slub_debug[=options[,slabs]] [MM, SLUB]
1589 Enabling slub_debug allows one to determine the
1590 culprit if slab objects become corrupted. Enabling
1591 slub_debug can create guard zones around objects and
1592 may poison objects when not in use. Also tracks the
1593 last alloc / free. For more information see
1594 Documentation/vm/slub.txt.
1596 slub_max_order= [MM, SLUB]
1597 Determines the maximum allowed order for slabs.
1598 A high setting may cause OOMs due to memory
1599 fragmentation. For more information see
1600 Documentation/vm/slub.txt.
1602 slub_min_objects= [MM, SLUB]
1603 The minimum number of objects per slab. SLUB will
1604 increase the slab order up to slub_max_order to
1605 generate a sufficiently large slab able to contain
1606 the number of objects indicated. The higher the number
1607 of objects the smaller the overhead of tracking slabs
1608 and the less frequently locks need to be acquired.
1609 For more information see Documentation/vm/slub.txt.
1611 slub_min_order= [MM, SLUB]
1612 Determines the mininum page order for slabs. Must be
1613 lower than slub_max_order.
1614 For more information see Documentation/vm/slub.txt.
1616 slub_nomerge [MM, SLUB]
1617 Disable merging of slabs with similar size. May be
1618 necessary if there is some reason to distinguish
1619 allocs to different slabs. Debug options disable
1620 merging on their own.
1621 For more information see Documentation/vm/slub.txt.
1623 smart2= [HW]
1624 Format: <io1>[,<io2>[,...,<io8>]]
1626 smp-alt-once [IA-32,SMP] On a hotplug CPU system, only
1627 attempt to substitute SMP alternatives once at boot.
1629 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1630 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1631 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1632 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1633 smsc-ircc2.ircc_irq= [HW] IRQ line
1634 smsc-ircc2.ircc_dma= [HW] DMA channel
1635 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1636 0: Toshiba Satellite 1800 (GP data pin select)
1637 1: Fast pin select (default)
1638 2: ATC IRMode
1640 snd-ad1816a= [HW,ALSA]
1642 snd-ad1848= [HW,ALSA]
1644 snd-ali5451= [HW,ALSA]
1646 snd-als100= [HW,ALSA]
1648 snd-als4000= [HW,ALSA]
1650 snd-azt2320= [HW,ALSA]
1652 snd-cmi8330= [HW,ALSA]
1654 snd-cmipci= [HW,ALSA]
1656 snd-cs4231= [HW,ALSA]
1658 snd-cs4232= [HW,ALSA]
1660 snd-cs4236= [HW,ALSA]
1662 snd-cs4281= [HW,ALSA]
1664 snd-cs46xx= [HW,ALSA]
1666 snd-dt019x= [HW,ALSA]
1668 snd-dummy= [HW,ALSA]
1670 snd-emu10k1= [HW,ALSA]
1672 snd-ens1370= [HW,ALSA]
1674 snd-ens1371= [HW,ALSA]
1676 snd-es968= [HW,ALSA]
1678 snd-es1688= [HW,ALSA]
1680 snd-es18xx= [HW,ALSA]
1682 snd-es1938= [HW,ALSA]
1684 snd-es1968= [HW,ALSA]
1686 snd-fm801= [HW,ALSA]
1688 snd-gusclassic= [HW,ALSA]
1690 snd-gusextreme= [HW,ALSA]
1692 snd-gusmax= [HW,ALSA]
1694 snd-hdsp= [HW,ALSA]
1696 snd-ice1712= [HW,ALSA]
1698 snd-intel8x0= [HW,ALSA]
1700 snd-interwave= [HW,ALSA]
1702 snd-interwave-stb=
1703 [HW,ALSA]
1705 snd-korg1212= [HW,ALSA]
1707 snd-maestro3= [HW,ALSA]
1709 snd-mpu401= [HW,ALSA]
1711 snd-mtpav= [HW,ALSA]
1713 snd-nm256= [HW,ALSA]
1715 snd-opl3sa2= [HW,ALSA]
1717 snd-opti92x-ad1848=
1718 [HW,ALSA]
1720 snd-opti92x-cs4231=
1721 [HW,ALSA]
1723 snd-opti93x= [HW,ALSA]
1725 snd-pmac= [HW,ALSA]
1727 snd-rme32= [HW,ALSA]
1729 snd-rme96= [HW,ALSA]
1731 snd-rme9652= [HW,ALSA]
1733 snd-sb8= [HW,ALSA]
1735 snd-sb16= [HW,ALSA]
1737 snd-sbawe= [HW,ALSA]
1739 snd-serial= [HW,ALSA]
1741 snd-sgalaxy= [HW,ALSA]
1743 snd-sonicvibes= [HW,ALSA]
1745 snd-sun-amd7930=
1746 [HW,ALSA]
1748 snd-sun-cs4231= [HW,ALSA]
1750 snd-trident= [HW,ALSA]
1752 snd-usb-audio= [HW,ALSA,USB]
1754 snd-via82xx= [HW,ALSA]
1756 snd-virmidi= [HW,ALSA]
1758 snd-wavefront= [HW,ALSA]
1760 snd-ymfpci= [HW,ALSA]
1762 sonycd535= [HW,CD]
1763 Format: <io>[,<irq>]
1765 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1766 See Documentation/sonypi.txt
1768 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1769 See Documentation/specialix.txt.
1771 spia_io_base= [HW,MTD]
1772 spia_fio_base=
1773 spia_pedr=
1774 spia_peddr=
1776 sscape= [HW,OSS]
1777 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1779 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1780 See Documentation/scsi/st.txt.
1782 st0x= [HW,SCSI]
1783 See header of drivers/scsi/seagate.c.
1785 sti= [PARISC,HW]
1786 Format: <num>
1787 Set the STI (builtin display/keyboard on the HP-PARISC
1788 machines) console (graphic card) which should be used
1789 as the initial boot-console.
1790 See also comment in drivers/video/console/sticore.c.
1792 sti_font= [HW]
1793 See comment in drivers/video/console/sticore.c.
1795 stifb= [HW]
1796 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1798 sunrpc.pool_mode=
1799 [NFS]
1800 Control how the NFS server code allocates CPUs to
1801 service thread pools. Depending on how many NICs
1802 you have and where their interrupts are bound, this
1803 option will affect which CPUs will do NFS serving.
1804 Note: this parameter cannot be changed while the
1805 NFS server is running.
1807 auto the server chooses an appropriate mode
1808 automatically using heuristics
1809 global a single global pool contains all CPUs
1810 percpu one pool for each CPU
1811 pernode one pool for each NUMA node (equivalent
1812 to global on non-NUMA machines)
1814 swiotlb= [IA-64] Number of I/O TLB slabs
1816 switches= [HW,M68k]
1818 sym53c416= [HW,SCSI]
1819 See header of drivers/scsi/sym53c416.c.
1821 sysrq_always_enabled
1822 [KNL]
1823 Ignore sysrq setting - this boot parameter will
1824 neutralize any effect of /proc/sys/kernel/sysrq.
1825 Useful for debugging.
1827 t128= [HW,SCSI]
1828 See header of drivers/scsi/t128.c.
1830 tdfx= [HW,DRM]
1832 thash_entries= [KNL,NET]
1833 Set number of hash buckets for TCP connection
1835 time Show timing data prefixed to each printk message line
1836 [deprecated, see 'printk.time']
1838 tipar.timeout= [HW,PPT]
1839 Set communications timeout in tenths of a second
1840 (default 15).
1842 tipar.delay= [HW,PPT]
1843 Set inter-bit delay in microseconds (default 10).
1845 tmc8xx= [HW,SCSI]
1846 See header of drivers/scsi/seagate.c.
1848 tmscsim= [HW,SCSI]
1849 See comment before function dc390_setup() in
1850 drivers/scsi/tmscsim.c.
1852 tp720= [HW,PS2]
1854 trix= [HW,OSS] MediaTrix AudioTrix Pro
1855 Format:
1856 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1858 tsdev.xres= [TS] Horizontal screen resolution.
1859 tsdev.yres= [TS] Vertical screen resolution.
1861 turbografx.map[2|3]= [HW,JOY]
1862 TurboGraFX parallel port interface
1863 Format:
1864 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1865 See also Documentation/input/joystick-parport.txt
1867 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1868 See header of drivers/scsi/u14-34f.c.
1870 uart401= [HW,OSS]
1871 Format: <io>,<irq>
1873 uart6850= [HW,OSS]
1874 Format: <io>,<irq>
1876 uhci-hcd.ignore_oc=
1877 [USB] Ignore overcurrent events (default N).
1878 Some badly-designed motherboards generate lots of
1879 bogus events, for ports that aren't wired to
1880 anything. Set this parameter to avoid log spamming.
1881 Note that genuine overcurrent events won't be
1882 reported either.
1884 usbcore.autosuspend=
1885 [USB] The autosuspend time delay (in seconds) used
1886 for newly-detected USB devices (default 2). This
1887 is the time required before an idle device will be
1888 autosuspended. Devices for which the delay is set
1889 to a negative value won't be autosuspended at all.
1891 usbhid.mousepoll=
1892 [USBHID] The interval which mice are to be polled at.
1894 vdso= [IA-32,SH]
1895 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1896 vdso=1: enable VDSO (default)
1897 vdso=0: disable VDSO mapping
1899 video= [FB] Frame buffer configuration
1900 See Documentation/fb/modedb.txt.
1902 vga= [BOOT,IA-32] Select a particular video mode
1903 See Documentation/i386/boot.txt and
1904 Documentation/svga.txt.
1905 Use vga=ask for menu.
1906 This is actually a boot loader parameter; the value is
1907 passed to the kernel using a special protocol.
1909 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1910 size of <nn>. This can be used to increase the
1911 minimum size (128MB on x86). It can also be used to
1912 decrease the size and leave more room for directly
1913 mapped kernel RAM.
1915 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1916 Format: <command>
1918 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1919 Format: <command>
1921 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1922 Format: <command>
1924 waveartist= [HW,OSS]
1925 Format: <io>,<irq>,<dma>,<dma2>
1927 wd33c93= [HW,SCSI]
1928 See header of drivers/scsi/wd33c93.c.
1930 wd7000= [HW,SCSI]
1931 See header of drivers/scsi/wd7000.c.
1933 wdt= [WDT] Watchdog
1934 See Documentation/watchdog/watchdog.txt.
1936 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1937 xd_geo= See header of drivers/block/xd.c.
1939 xirc2ps_cs= [NET,PCMCIA]
1940 Format:
1941 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1943 norandmaps Don't use address space randomization
1944 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1946 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1947 This is useful to get more information why
1948 you got a "dwarf2 unwinder stuck"
1950 ______________________________________________________________________
1952 TODO:
1954 Add documentation for ALSA options.
1955 Add more DRM drivers.