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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AX25 Appropriate AX.25 support is enabled.
38 DRM Direct Rendering Management support is enabled.
39 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
40 EFI EFI Partitioning (GPT) is enabled
41 EIDE EIDE/ATAPI support is enabled.
42 FB The frame buffer device is enabled.
43 HW Appropriate hardware is enabled.
44 IA-64 IA-64 architecture is enabled.
45 IOSCHED More than one I/O scheduler is enabled.
46 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
47 ISAPNP ISA PnP code is enabled.
48 ISDN Appropriate ISDN support is enabled.
49 JOY Appropriate joystick support is enabled.
50 LIBATA Libata driver is enabled
51 LP Printer support is enabled.
52 LOOP Loopback device support is enabled.
53 M68k M68k architecture is enabled.
54 These options have more detailed description inside of
55 Documentation/m68k/kernel-options.txt.
56 MCA MCA bus support is enabled.
57 MDA MDA console support is enabled.
58 MOUSE Appropriate mouse support is enabled.
59 MSI Message Signaled Interrupts (PCI).
60 MTD MTD (Memory Technology Device) support is enabled.
61 NET Appropriate network support is enabled.
62 NUMA NUMA support is enabled.
63 GENERIC_TIME The generic timeofday code is enabled.
64 NFS Appropriate NFS support is enabled.
65 OSS OSS sound support is enabled.
66 PV_OPS A paravirtualized kernel is enabled.
67 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
68 PARISC The PA-RISC architecture is enabled.
69 PCI PCI bus support is enabled.
70 PCMCIA The PCMCIA subsystem is enabled.
71 PNP Plug & Play support is enabled.
72 PPC PowerPC architecture is enabled.
73 PPT Parallel port support is enabled.
74 PS2 Appropriate PS/2 support is enabled.
75 RAM RAM disk support is enabled.
76 S390 S390 architecture is enabled.
77 SCSI Appropriate SCSI support is enabled.
78 A lot of drivers has their options described inside of
79 Documentation/scsi/.
80 SELINUX SELinux support is enabled.
81 SERIAL Serial support is enabled.
82 SH SuperH architecture is enabled.
83 SMP The kernel is an SMP kernel.
84 SPARC Sparc architecture is enabled.
85 SWSUSP Software suspend is enabled.
86 TS Appropriate touchscreen support is enabled.
87 USB USB support is enabled.
88 USBHID USB Human Interface Device support is enabled.
89 V4L Video For Linux support is enabled.
90 VGA The VGA console has been enabled.
91 VT Virtual terminal support is enabled.
92 WDT Watchdog support is enabled.
93 XT IBM PC/XT MFM hard disk support is enabled.
94 X86-32 X86-32, aka i386 architecture is enabled.
95 X86-64 X86-64 architecture is enabled.
96 More X86-64 boot options can be found in
97 Documentation/x86_64/boot-options.txt .
99 In addition, the following text indicates that the option:
101 BUGS= Relates to possible processor bugs on the said processor.
102 KNL Is a kernel start-up parameter.
103 BOOT Is a boot loader parameter.
105 Parameters denoted with BOOT are actually interpreted by the boot
106 loader, and have no meaning to the kernel directly.
107 Do not modify the syntax of boot loader parameters without extreme
108 need or coordination with <Documentation/i386/boot.txt>.
110 There are also arch-specific kernel-parameters not documented here.
111 See for example <Documentation/x86_64/boot-options.txt>.
113 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
114 a trailing = on the name of any parameter states that that parameter will
115 be entered as an environment variable, whereas its absence indicates that
116 it will appear as a kernel argument readable via /proc/cmdline by programs
117 running once the system is up.
119 The number of kernel parameters is not limited, but the length of the
120 complete command line (parameters including spaces etc.) is limited to
121 a fixed number of characters. This limit depends on the architecture
122 and is between 256 and 4096 characters. It is defined in the file
123 ./include/asm/setup.h as COMMAND_LINE_SIZE.
126 acpi= [HW,ACPI,X86-64,i386]
127 Advanced Configuration and Power Interface
128 Format: { force | off | ht | strict | noirq }
129 force -- enable ACPI if default was off
130 off -- disable ACPI if default was on
131 noirq -- do not use ACPI for IRQ routing
132 ht -- run only enough ACPI to enable Hyper Threading
133 strict -- Be less tolerant of platforms that are not
134 strictly ACPI specification compliant.
136 See also Documentation/pm.txt, pci=noacpi
138 acpi_apic_instance= [ACPI, IOAPIC]
139 Format: <int>
140 2: use 2nd APIC table, if available
141 1,0: use 1st APIC table
142 default: 0
144 acpi_sleep= [HW,ACPI] Sleep options
145 Format: { s3_bios, s3_mode }
146 See Documentation/power/video.txt
148 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
149 Format: { level | edge | high | low }
151 acpi_irq_balance [HW,ACPI]
152 ACPI will balance active IRQs
153 default in APIC mode
155 acpi_irq_nobalance [HW,ACPI]
156 ACPI will not move active IRQs (default)
157 default in PIC mode
159 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
160 use by PCI
161 Format: <irq>,<irq>...
163 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
164 Format: <irq>,<irq>...
166 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
168 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
169 Format: To spoof as Windows 98: ="Microsoft Windows"
171 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
172 acpi_osi="string1" # add string1 -- only one string
173 acpi_osi="!string2" # remove built-in string2
174 acpi_osi= # disable all strings
176 acpi_serialize [HW,ACPI] force serialization of AML methods
178 acpi_skip_timer_override [HW,ACPI]
179 Recognize and ignore IRQ0/pin2 Interrupt Override.
180 For broken nForce2 BIOS resulting in XT-PIC timer.
181 acpi_use_timer_override [HW,ACPI}
182 Use timer override. For some broken Nvidia NF5 boards
183 that require a timer override, but don't have
184 HPET
186 acpi.debug_layer= [HW,ACPI]
187 Format: <int>
188 Each bit of the <int> indicates an ACPI debug layer,
189 1: enable, 0: disable. It is useful for boot time
190 debugging. After system has booted up, it can be set
191 via /sys/module/acpi/parameters/debug_layer.
192 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
193 Available bits (add the numbers together) to enable debug output
194 for specific parts of the ACPI subsystem:
195 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
196 0x10 namespace 0x20 parser 0x40 dispatcher
197 0x80 executer 0x100 resources 0x200 acpica debugger
198 0x400 os services 0x800 acpica disassembler.
199 The number can be in decimal or prefixed with 0x in hex.
200 Warning: Many of these options can produce a lot of
201 output and make your system unusable. Be very careful.
203 acpi.debug_level= [HW,ACPI]
204 Format: <int>
205 Each bit of the <int> indicates an ACPI debug level,
206 1: enable, 0: disable. It is useful for boot time
207 debugging. After system has booted up, it can be set
208 via /sys/module/acpi/parameters/debug_level.
209 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
210 Available bits (add the numbers together) to enable different
211 debug output levels of the ACPI subsystem:
212 0x01 error 0x02 warn 0x04 init 0x08 debug object
213 0x10 info 0x20 init names 0x40 parse 0x80 load
214 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
215 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
216 0x10000 resources 0x20000 user requests 0x40000 package.
217 The number can be in decimal or prefixed with 0x in hex.
218 Warning: Many of these options can produce a lot of
219 output and make your system unusable. Be very careful.
222 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
224 acpi_pm_good [X86-32,X86-64]
225 Override the pmtimer bug detection: force the kernel
226 to assume that this machine's pmtimer latches its value
227 and always returns good values.
229 agp= [AGP]
230 { off | try_unsupported }
231 off: disable AGP support
232 try_unsupported: try to drive unsupported chipsets
233 (may crash computer or cause data corruption)
235 enable_timer_pin_1 [i386,x86-64]
236 Enable PIN 1 of APIC timer
237 Can be useful to work around chipset bugs
238 (in particular on some ATI chipsets).
239 The kernel tries to set a reasonable default.
241 disable_timer_pin_1 [i386,x86-64]
242 Disable PIN 1 of APIC timer
243 Can be useful to work around chipset bugs.
245 ad1848= [HW,OSS]
246 Format: <io>,<irq>,<dma>,<dma2>,<type>
248 advansys= [HW,SCSI]
249 See header of drivers/scsi/advansys.c.
251 advwdt= [HW,WDT] Advantech WDT
252 Format: <iostart>,<iostop>
254 aedsp16= [HW,OSS] Audio Excel DSP 16
255 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
256 See also header of sound/oss/aedsp16.c.
258 aha152x= [HW,SCSI]
259 See Documentation/scsi/aha152x.txt.
261 aha1542= [HW,SCSI]
262 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
264 aic7xxx= [HW,SCSI]
265 See Documentation/scsi/aic7xxx.txt.
267 aic79xx= [HW,SCSI]
268 See Documentation/scsi/aic79xx.txt.
270 amijoy.map= [HW,JOY] Amiga joystick support
271 Map of devices attached to JOY0DAT and JOY1DAT
272 Format: <a>,<b>
273 See also Documentation/kernel/input/joystick.txt
275 analog.map= [HW,JOY] Analog joystick and gamepad support
276 Specifies type or capabilities of an analog joystick
277 connected to one of 16 gameports
278 Format: <type1>,<type2>,..<type16>
280 apc= [HW,SPARC]
281 Power management functions (SPARCstation-4/5 + deriv.)
282 Format: noidle
283 Disable APC CPU standby support. SPARCstation-Fox does
284 not play well with APC CPU idle - disable it if you have
285 APC and your system crashes randomly.
287 apic= [APIC,i386] Advanced Programmable Interrupt Controller
288 Change the output verbosity whilst booting
289 Format: { quiet (default) | verbose | debug }
290 Change the amount of debugging information output
291 when initialising the APIC and IO-APIC components.
293 apm= [APM] Advanced Power Management
294 See header of arch/i386/kernel/apm.c.
296 applicom= [HW]
297 Format: <mem>,<irq>
299 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
300 Format: <io>,<irq>,<nodeID>
302 ataflop= [HW,M68k]
304 atarimouse= [HW,MOUSE] Atari Mouse
306 atascsi= [HW,SCSI] Atari SCSI
308 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
309 EzKey and similar keyboards
311 atkbd.reset= [HW] Reset keyboard during initialization
313 atkbd.set= [HW] Select keyboard code set
314 Format: <int> (2 = AT (default), 3 = PS/2)
316 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
317 keyboards
319 atkbd.softraw= [HW] Choose between synthetic and real raw mode
320 Format: <bool> (0 = real, 1 = synthetic (default))
322 atkbd.softrepeat= [HW]
323 Use software keyboard repeat
325 autotest [IA64]
327 baycom_epp= [HW,AX25]
328 Format: <io>,<mode>
330 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
331 Format: <io>,<mode>
332 See header of drivers/net/hamradio/baycom_par.c.
334 baycom_ser_fdx= [HW,AX25]
335 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
336 Format: <io>,<irq>,<mode>[,<baud>]
337 See header of drivers/net/hamradio/baycom_ser_fdx.c.
339 baycom_ser_hdx= [HW,AX25]
340 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
341 Format: <io>,<irq>,<mode>
342 See header of drivers/net/hamradio/baycom_ser_hdx.c.
344 blkmtd_device= [HW,MTD]
345 blkmtd_erasesz=
346 blkmtd_ro=
347 blkmtd_bs=
348 blkmtd_count=
350 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
351 bttv.radio= Most important insmod options are available as
352 kernel args too.
353 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
354 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
356 BusLogic= [HW,SCSI]
357 See drivers/scsi/BusLogic.c, comment before function
358 BusLogic_ParseDriverOptions().
360 c101= [NET] Moxa C101 synchronous serial card
362 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
363 Sometimes CPU hardware bugs make them report the cache
364 size incorrectly. The kernel will attempt work arounds
365 to fix known problems, but for some CPUs it is not
366 possible to determine what the correct size should be.
367 This option provides an override for these situations.
369 chandev= [HW,NET] Generic channel device initialisation
371 checkreqprot [SELINUX] Set initial checkreqprot flag value.
372 Format: { "0" | "1" }
373 See security/selinux/Kconfig help text.
374 0 -- check protection applied by kernel (includes
375 any implied execute protection).
376 1 -- check protection requested by application.
377 Default value is set via a kernel config option.
378 Value can be changed at runtime via
379 /selinux/checkreqprot.
381 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
382 [Deprecated]
383 Forces specified clocksource (if available) to be used
384 when calculating gettimeofday(). If specified
385 clocksource is not available, it defaults to PIT.
386 Format: { pit | tsc | cyclone | pmtmr }
388 clocksource= [GENERIC_TIME] Override the default clocksource
389 Format: <string>
390 Override the default clocksource and use the clocksource
391 with the name specified.
392 Some clocksource names to choose from, depending on
393 the platform:
394 [all] jiffies (this is the base, fallback clocksource)
395 [ACPI] acpi_pm
396 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
397 pxa_timer,timer3,32k_counter,timer0_1
398 [AVR32] avr32
399 [X86-32] pit,hpet,tsc,vmi-timer;
400 scx200_hrt on Geode; cyclone on IBM x440
401 [MIPS] MIPS
402 [PARISC] cr16
403 [S390] tod
404 [SH] SuperH
405 [SPARC64] tick
406 [X86-64] hpet,tsc
408 code_bytes [IA32] How many bytes of object code to print in an
409 oops report.
410 Range: 0 - 8192
411 Default: 64
413 disable_8254_timer
414 enable_8254_timer
415 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
416 over the 8254 in addition to over the IO-APIC. The
417 kernel tries to set a sensible default.
419 hpet= [X86-32,HPET] option to disable HPET and use PIT.
420 Format: disable
422 com20020= [HW,NET] ARCnet - COM20020 chipset
423 Format:
424 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
426 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
427 Format: <io>[,<irq>]
429 com90xx= [HW,NET]
430 ARCnet - COM90xx chipset (memory-mapped buffers)
431 Format: <io>[,<irq>[,<memstart>]]
433 condev= [HW,S390] console device
434 conmode=
436 console= [KNL] Output console device and options.
438 tty<n> Use the virtual console device <n>.
440 ttyS<n>[,options]
441 ttyUSB0[,options]
442 Use the specified serial port. The options are of
443 the form "bbbbpnf", where "bbbb" is the baud rate,
444 "p" is parity ("n", "o", or "e"), "n" is number of
445 bits, and "f" is flow control ("r" for RTS or
446 omit it). Default is "9600n8".
448 See Documentation/serial-console.txt for more
449 information. See
450 Documentation/networking/netconsole.txt for an
451 alternative.
453 uart[8250],io,<addr>[,options]
454 uart[8250],mmio,<addr>[,options]
455 Start an early, polled-mode console on the 8250/16550
456 UART at the specified I/O port or MMIO address,
457 switching to the matching ttyS device later. The
458 options are the same as for ttyS, above.
460 earlycon= [KNL] Output early console device and options.
461 uart[8250],io,<addr>[,options]
462 uart[8250],mmio,<addr>[,options]
463 Start an early, polled-mode console on the 8250/16550
464 UART at the specified I/O port or MMIO address.
465 The options are the same as for ttyS, above.
467 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
468 Format:
469 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
471 cpia_pp= [HW,PPT]
472 Format: { parport<nr> | auto | none }
474 crashkernel=nn[KMG]@ss[KMG]
475 [KNL] Reserve a chunk of physical memory to
476 hold a kernel to switch to with kexec on panic.
478 cs4232= [HW,OSS]
479 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
481 cs89x0_dma= [HW,NET]
482 Format: <dma>
484 cs89x0_media= [HW,NET]
485 Format: { rj45 | aui | bnc }
487 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
489 dasd= [HW,NET]
490 See header of drivers/s390/block/dasd_devmap.c.
492 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
493 (one device per port)
494 Format: <port#>,<type>
495 See also Documentation/input/joystick-parport.txt
497 debug [KNL] Enable kernel debugging (events log level).
499 debug_locks_verbose=
500 [KNL] verbose self-tests
501 Format=<0|1>
502 Print debugging info while doing the locking API
503 self-tests.
504 We default to 0 (no extra messages), setting it to
505 1 will print _a lot_ more information - normally
506 only useful to kernel developers.
508 decnet= [HW,NET]
509 Format: <area>[,<node>]
510 See also Documentation/networking/decnet.txt.
512 default_blu= [VT]
513 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
514 Change the default blue palette of the console.
515 This is a 16-member array composed of values
516 ranging from 0-255.
518 default_grn= [VT]
519 Format: <green0>,<green1>,<green2>,...,<green15>
520 Change the default green palette of the console.
521 This is a 16-member array composed of values
522 ranging from 0-255.
524 default_red= [VT]
525 Format: <red0>,<red1>,<red2>,...,<red15>
526 Change the default red palette of the console.
527 This is a 16-member array composed of values
528 ranging from 0-255.
530 default_utf8= [VT]
531 Format=<0|1>
532 Set system-wide default UTF-8 mode for all tty's.
533 Default is 0 and by setting to 1, it enables UTF-8
534 mode for all newly opened or allocated terminals.
536 dhash_entries= [KNL]
537 Set number of hash buckets for dentry cache.
539 digi= [HW,SERIAL]
540 IO parameters + enable/disable command.
542 digiepca= [HW,SERIAL]
543 See drivers/char/README.epca and
544 Documentation/digiepca.txt.
546 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
547 support available.
548 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
550 dmasound= [HW,OSS] Sound subsystem buffers
552 dscc4.setup= [NET]
554 dtc3181e= [HW,SCSI]
556 earlyprintk= [X86-32,X86-64,SH]
557 earlyprintk=vga
558 earlyprintk=serial[,ttySn[,baudrate]]
560 Append ",keep" to not disable it when the real console
561 takes over.
563 Only vga or serial at a time, not both.
565 Currently only ttyS0 and ttyS1 are supported.
567 Interaction with the standard serial driver is not
568 very good.
570 The VGA output is eventually overwritten by the real
571 console.
573 eata= [HW,SCSI]
575 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
576 Format: <int>
577 0: polling mode
578 non-0: interrupt mode (default)
580 eda= [HW,PS2]
582 edb= [HW,PS2]
584 edd= [EDD]
585 Format: {"of[f]" | "sk[ipmbr]"}
586 See comment in arch/i386/boot/edd.S
588 eicon= [HW,ISDN]
589 Format: <id>,<membase>,<irq>
591 eisa_irq_edge= [PARISC,HW]
592 See header of drivers/parisc/eisa.c.
594 elanfreq= [X86-32]
595 See comment before function elanfreq_setup() in
596 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
598 elevator= [IOSCHED]
599 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
600 See Documentation/block/as-iosched.txt and
601 Documentation/block/deadline-iosched.txt for details.
603 elfcorehdr= [X86-32, X86_64]
604 Specifies physical address of start of kernel core
605 image elf header. Generally kexec loader will
606 pass this option to capture kernel.
607 See Documentation/kdump/kdump.txt for details.
609 enforcing [SELINUX] Set initial enforcing status.
610 Format: {"0" | "1"}
611 See security/selinux/Kconfig help text.
612 0 -- permissive (log only, no denials).
613 1 -- enforcing (deny and log).
614 Default value is 0.
615 Value can be changed at runtime via /selinux/enforce.
617 es1371= [HW,OSS]
618 Format: <spdif>,[<nomix>,[<amplifier>]]
619 See also header of sound/oss/es1371.c.
621 ether= [HW,NET] Ethernet cards parameters
622 This option is obsoleted by the "netdev=" option, which
623 has equivalent usage. See its documentation for details.
625 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
626 Format: <io>[,<irq>]
628 failslab=
629 fail_page_alloc=
630 fail_make_request=[KNL]
631 General fault injection mechanism.
632 Format: <interval>,<probability>,<space>,<times>
633 See also /Documentation/fault-injection/.
635 fd_mcs= [HW,SCSI]
636 See header of drivers/scsi/fd_mcs.c.
638 fdomain= [HW,SCSI]
639 See header of drivers/scsi/fdomain.c.
641 floppy= [HW]
642 See Documentation/floppy.txt.
644 gamecon.map[2|3]=
645 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
646 support via parallel port (up to 5 devices per port)
647 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
648 See also Documentation/input/joystick-parport.txt
650 gamma= [HW,DRM]
652 gdth= [HW,SCSI]
653 See header of drivers/scsi/gdth.c.
655 gpt [EFI] Forces disk with valid GPT signature but
656 invalid Protective MBR to be treated as GPT.
658 gvp11= [HW,SCSI]
660 hashdist= [KNL,NUMA] Large hashes allocated during boot
661 are distributed across NUMA nodes. Defaults on
662 for IA-64, off otherwise.
663 Format: 0 | 1 (for off | on)
665 hcl= [IA-64] SGI's Hardware Graph compatibility layer
667 hd= [EIDE] (E)IDE hard drive subsystem geometry
668 Format: <cyl>,<head>,<sect>
670 hd?= [HW] (E)IDE subsystem
671 hd?lun= See Documentation/ide.txt.
673 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
674 size of <nn>. This works even on boxes that have no
675 highmem otherwise. This also works to reduce highmem
676 size on bigger boxes.
678 highres= [KNL] Enable/disable high resolution timer mode.
679 Valid parameters: "on", "off"
680 Default: "on"
682 hisax= [HW,ISDN]
683 See Documentation/isdn/README.HiSax.
685 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
687 i8042.direct [HW] Put keyboard port into non-translated mode
688 i8042.dumbkbd [HW] Pretend that controller can only read data from
689 keyboard and cannot control its state
690 (Don't attempt to blink the leds)
691 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
692 i8042.nokbd [HW] Don't check/create keyboard port
693 i8042.nomux [HW] Don't check presence of an active multiplexing
694 controller
695 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
696 controllers
697 i8042.panicblink=
698 [HW] Frequency with which keyboard LEDs should blink
699 when kernel panics (default is 0.5 sec)
700 i8042.reset [HW] Reset the controller during init and cleanup
701 i8042.unlock [HW] Unlock (ignore) the keylock
703 i810= [HW,DRM]
705 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
706 indicates that the driver is running on unsupported
707 hardware.
708 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
709 does not match list of supported models.
710 i8k.power_status
711 [HW] Report power status in /proc/i8k
712 (disabled by default)
713 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
714 capability is set.
716 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
717 See Documentation/mca.txt.
719 icn= [HW,ISDN]
720 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
722 ide= [HW] (E)IDE subsystem
723 Format: ide=nodma or ide=doubler or ide=reverse
724 See Documentation/ide.txt.
726 ide?= [HW] (E)IDE subsystem
727 Format: ide?=noprobe or chipset specific parameters.
728 See Documentation/ide.txt.
730 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
731 See Documentation/ide.txt.
733 idle= [X86]
734 Format: idle=poll or idle=mwait
735 Poll forces a polling idle loop that can slightly improves the performance
736 of waking up a idle CPU, but will use a lot of power and make the system
737 run hot. Not recommended.
738 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
739 to not use it because it doesn't save as much power as a normal idle
740 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
741 as idle=poll.
743 ignore_loglevel [KNL]
744 Ignore loglevel setting - this will print /all/
745 kernel messages to the console. Useful for debugging.
747 ihash_entries= [KNL]
748 Set number of hash buckets for inode cache.
750 in2000= [HW,SCSI]
751 See header of drivers/scsi/in2000.c.
753 init= [KNL]
754 Format: <full_path>
755 Run specified binary instead of /sbin/init as init
756 process.
758 initcall_debug [KNL] Trace initcalls as they are executed. Useful
759 for working out where the kernel is dying during
760 startup.
762 initrd= [BOOT] Specify the location of the initial ramdisk
764 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
765 Format: <irq>
767 inttest= [IA64]
769 io7= [HW] IO7 for Marvel based alpha systems
770 See comment before marvel_specify_io7 in
771 arch/alpha/kernel/core_marvel.c.
773 ip= [IP_PNP]
774 See Documentation/nfsroot.txt.
776 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
777 See comment before ip2_setup() in
778 drivers/char/ip2/ip2base.c.
780 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
781 See header of drivers/scsi/ips.c.
783 ports= [IP_VS_FTP] IPVS ftp helper module
784 Default is 21.
785 Up to 8 (IP_VS_APP_MAX_PORTS) ports
786 may be specified.
787 Format: <port>,<port>....
789 irqfixup [HW]
790 When an interrupt is not handled search all handlers
791 for it. Intended to get systems with badly broken
792 firmware running.
794 irqpoll [HW]
795 When an interrupt is not handled search all handlers
796 for it. Also check all handlers each timer
797 interrupt. Intended to get systems with badly broken
798 firmware running.
800 isapnp= [ISAPNP]
801 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
803 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
804 Format:
805 <cpu number>,...,<cpu number>
806 or
807 <cpu number>-<cpu number> (must be a positive range in ascending order)
808 or a mixture
809 <cpu number>,...,<cpu number>-<cpu number>
810 This option can be used to specify one or more CPUs
811 to isolate from the general SMP balancing and scheduling
812 algorithms. The only way to move a process onto or off
813 an "isolated" CPU is via the CPU affinity syscalls.
814 <cpu number> begins at 0 and the maximum value is
815 "number of CPUs in system - 1".
817 This option is the preferred way to isolate CPUs. The
818 alternative -- manually setting the CPU mask of all
819 tasks in the system -- can cause problems and
820 suboptimal load balancer performance.
822 iucv= [HW,NET]
824 js= [HW,JOY] Analog joystick
825 See Documentation/input/joystick.txt.
827 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
828 specifies the amount of memory usable by the kernel
829 for non-movable allocations. The requested amount is
830 spread evenly throughout all nodes in the system. The
831 remaining memory in each node is used for Movable
832 pages. In the event, a node is too small to have both
833 kernelcore and Movable pages, kernelcore pages will
834 take priority and other nodes will have a larger number
835 of kernelcore pages. The Movable zone is used for the
836 allocation of pages that may be reclaimed or moved
837 by the page migration subsystem. This means that
838 HugeTLB pages may not be allocated from this zone.
839 Note that allocations like PTEs-from-HighMem still
840 use the HighMem zone if it exists, and the Normal
841 zone if it does not.
843 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
844 is similar to kernelcore except it specifies the
845 amount of memory used for migratable allocations.
846 If both kernelcore and movablecore is specified,
847 then kernelcore will be at *least* the specified
848 value but may be more. If movablecore on its own
849 is specified, the administrator must be careful
850 that the amount of memory usable for all allocations
851 is not too small.
853 keepinitrd [HW,ARM]
855 kstack=N [X86-32,X86-64] Print N words from the kernel stack
856 in oops dumps.
858 l2cr= [PPC]
860 lapic [X86-32,APIC] Enable the local APIC even if BIOS
861 disabled it.
863 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
864 C2 power state.
866 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
867 Format: addr:<io>,irq:<irq>
869 load_ramdisk= [RAM] List of ramdisks to load from floppy
870 See Documentation/ramdisk.txt.
872 lockd.nlm_grace_period=P [NFS] Assign grace period.
873 Format: <integer>
875 lockd.nlm_tcpport=N [NFS] Assign TCP port.
876 Format: <integer>
878 lockd.nlm_timeout=T [NFS] Assign timeout value.
879 Format: <integer>
881 lockd.nlm_udpport=M [NFS] Assign UDP port.
882 Format: <integer>
884 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
885 Format: <irq>
887 loglevel= All Kernel Messages with a loglevel smaller than the
888 console loglevel will be printed to the console. It can
889 also be changed with klogd or other programs. The
890 loglevels are defined as follows:
892 0 (KERN_EMERG) system is unusable
893 1 (KERN_ALERT) action must be taken immediately
894 2 (KERN_CRIT) critical conditions
895 3 (KERN_ERR) error conditions
896 4 (KERN_WARNING) warning conditions
897 5 (KERN_NOTICE) normal but significant condition
898 6 (KERN_INFO) informational
899 7 (KERN_DEBUG) debug-level messages
901 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
902 Format: { n | nk | nM }
903 n must be a power of two. The default size
904 is set in the kernel config file.
906 lp=0 [LP] Specify parallel ports to use, e.g,
907 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
908 lp=reset first parallel port). 'lp=0' disables the
909 lp=auto printer driver. 'lp=reset' (which can be
910 specified in addition to the ports) causes
911 attached printers to be reset. Using
912 lp=port1,port2,... specifies the parallel ports
913 to associate lp devices with, starting with
914 lp0. A port specification may be 'none' to skip
915 that lp device, or a parport name such as
916 'parport0'. Specifying 'lp=auto' instead of a
917 port specification list means that device IDs
918 from each port should be examined, to see if
919 an IEEE 1284-compliant printer is attached; if
920 so, the driver will manage that printer.
921 See also header of drivers/char/lp.c.
923 lpj=n [KNL]
924 Sets loops_per_jiffy to given constant, thus avoiding
925 time-consuming boot-time autodetection (up to 250 ms per
926 CPU). 0 enables autodetection (default). To determine
927 the correct value for your kernel, boot with normal
928 autodetection and see what value is printed. Note that
929 on SMP systems the preset will be applied to all CPUs,
930 which is likely to cause problems if your CPUs need
931 significantly divergent settings. An incorrect value
932 will cause delays in the kernel to be wrong, leading to
933 unpredictable I/O errors and other breakage. Although
934 unlikely, in the extreme case this might damage your
935 hardware.
937 ltpc= [NET]
938 Format: <io>,<irq>,<dma>
940 mac5380= [HW,SCSI] Format:
941 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
943 mac53c9x= [HW,SCSI] Format:
944 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
946 machvec= [IA64] Force the use of a particular machine-vector
947 (machvec) in a generic kernel.
948 Example: machvec=hpzx1_swiotlb
950 max_loop= [LOOP] Maximum number of loopback devices that can
951 be mounted
952 Format: <1-256>
954 maxcpus= [SMP] Maximum number of processors that an SMP kernel
955 should make use of. maxcpus=n : n >= 0 limits the
956 kernel to using 'n' processors. n=0 is a special case,
957 it is equivalent to "nosmp", which also disables
958 the IO APIC.
960 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
961 equal to this physical address is ignored.
963 max_luns= [SCSI] Maximum number of LUNs to probe.
964 Should be between 1 and 2^32-1.
966 max_report_luns=
967 [SCSI] Maximum number of LUNs received.
968 Should be between 1 and 16384.
970 mca-pentium [BUGS=X86-32]
972 mcatest= [IA-64]
974 mce [X86-32] Machine Check Exception
976 md= [HW] RAID subsystems devices and level
977 See Documentation/md.txt.
979 mdacon= [MDA]
980 Format: <first>,<last>
981 Specifies range of consoles to be captured by the MDA.
983 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
984 Amount of memory to be used when the kernel is not able
985 to see the whole system memory or for test.
986 [X86-32] Use together with memmap= to avoid physical
987 address space collisions. Without memmap= PCI devices
988 could be placed at addresses belonging to unused RAM.
990 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
991 memory.
993 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
994 E820 memory map, as specified by the user.
995 Such memmap=exactmap lines can be constructed based on
996 BIOS output or other requirements. See the memmap=nn@ss
997 option description.
999 memmap=nn[KMG]@ss[KMG]
1000 [KNL] Force usage of a specific region of memory
1001 Region of memory to be used, from ss to ss+nn.
1003 memmap=nn[KMG]#ss[KMG]
1004 [KNL,ACPI] Mark specific memory as ACPI data.
1005 Region of memory to be used, from ss to ss+nn.
1007 memmap=nn[KMG]$ss[KMG]
1008 [KNL,ACPI] Mark specific memory as reserved.
1009 Region of memory to be used, from ss to ss+nn.
1011 meye.*= [HW] Set MotionEye Camera parameters
1012 See Documentation/video4linux/meye.txt.
1014 mga= [HW,DRM]
1016 mousedev.tap_time=
1017 [MOUSE] Maximum time between finger touching and
1018 leaving touchpad surface for touch to be considered
1019 a tap and be reported as a left button click (for
1020 touchpads working in absolute mode only).
1021 Format: <msecs>
1022 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1023 reporting absolute coordinates, such as tablets
1024 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1025 reporting absolute coordinates, such as tablets
1027 mpu401= [HW,OSS]
1028 Format: <io>,<irq>
1030 MTD_Partition= [MTD]
1031 Format: <name>,<region-number>,<size>,<offset>
1033 MTD_Region= [MTD] Format:
1034 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1036 mtdparts= [MTD]
1037 See drivers/mtd/cmdlinepart.c.
1039 mtouchusb.raw_coordinates=
1040 [HW] Make the MicroTouch USB driver use raw coordinates
1041 ('y', default) or cooked coordinates ('n')
1043 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1045 NCR_D700= [HW,SCSI]
1046 See header of drivers/scsi/NCR_D700.c.
1048 ncr5380= [HW,SCSI]
1050 ncr53c400= [HW,SCSI]
1052 ncr53c400a= [HW,SCSI]
1054 ncr53c406a= [HW,SCSI]
1056 ncr53c8xx= [HW,SCSI]
1058 netdev= [NET] Network devices parameters
1059 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1060 Note that mem_start is often overloaded to mean
1061 something different and driver-specific.
1062 This usage is only documented in each driver source
1063 file if at all.
1065 nfsaddrs= [NFS]
1066 See Documentation/nfsroot.txt.
1068 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1069 See Documentation/nfsroot.txt.
1071 nfs.callback_tcpport=
1072 [NFS] set the TCP port on which the NFSv4 callback
1073 channel should listen.
1075 nfs.idmap_cache_timeout=
1076 [NFS] set the maximum lifetime for idmapper cache
1077 entries.
1079 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1081 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1082 emulation library even if a 387 maths coprocessor
1083 is present.
1085 noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1086 when set.
1087 Format: <int>
1089 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1090 caches in the slab allocator. Saves per-node memory,
1091 but will impact performance.
1093 noalign [KNL,ARM]
1095 noapic [SMP,APIC] Tells the kernel to not make use of any
1096 IOAPICs that may be present in the system.
1098 noasync [HW,M68K] Disables async and sync negotiation for
1099 all devices.
1101 nobats [PPC] Do not use BATs for mapping kernel lowmem
1102 on "Classic" PPC cores.
1104 nocache [ARM]
1106 nodelayacct [KNL] Disable per-task delay accounting
1108 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1110 noexec [IA-64]
1112 noexec [X86-32,X86-64]
1113 noexec=on: enable non-executable mappings (default)
1114 noexec=off: disable nn-executable mappings
1116 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1117 register save and restore. The kernel will only save
1118 legacy floating-point registers on task switch.
1120 nohlt [BUGS=ARM]
1122 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1123 instruction doesn't work correctly and not to
1124 use it.
1126 nohalt [IA-64] Tells the kernel not to use the power saving
1127 function PAL_HALT_LIGHT when idle. This increases
1128 power-consumption. On the positive side, it reduces
1129 interrupt wake-up latency, which may improve performance
1130 in certain environments such as networked servers or
1131 real-time systems.
1133 nohz= [KNL] Boottime enable/disable dynamic ticks
1134 Valid arguments: on, off
1135 Default: on
1137 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1139 noirqdebug [X86-32] Disables the code which attempts to detect and
1140 disable unhandled interrupt sources.
1142 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1143 broken timer IRQ sources.
1145 noisapnp [ISAPNP] Disables ISA PnP code.
1147 noinitrd [RAM] Tells the kernel not to load any configured
1148 initial RAM disk.
1150 nointroute [IA-64]
1152 nojitter [IA64] Disables jitter checking for ITC timers.
1154 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1156 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1158 noltlbs [PPC] Do not use large page/tlb entries for kernel
1159 lowmem mapping on PPC40x.
1161 nomca [IA-64] Disable machine check abort handling
1163 nomce [X86-32] Machine Check Exception
1165 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1167 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1168 with UP alternatives
1170 noresidual [PPC] Don't use residual data on PReP machines.
1172 noresume [SWSUSP] Disables resume and restores original swap
1173 space.
1175 no-scroll [VGA] Disables scrollback.
1176 This is required for the Braillex ib80-piezo Braille
1177 reader made by F.H. Papenmeier (Germany).
1179 nosbagart [IA-64]
1181 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1183 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1184 and disable the IO APIC. legacy for "maxcpus=0".
1186 nosoftlockup [KNL] Disable the soft-lockup detector.
1188 nosync [HW,M68K] Disables sync negotiation for all devices.
1190 notsc [BUGS=X86-32] Disable Time Stamp Counter
1192 nousb [USB] Disable the USB subsystem
1194 nowb [ARM]
1196 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1197 one of ['zone', 'node', 'default'] can be specified
1198 This can be set from sysctl after boot.
1199 See Documentation/sysctl/vm.txt for details.
1201 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1203 opl3= [HW,OSS]
1204 Format: <io>
1206 oprofile.timer= [HW]
1207 Use timer interrupt instead of performance counters
1209 osst= [HW,SCSI] SCSI Tape Driver
1210 Format: <buffer_size>,<write_threshold>
1211 See also Documentation/scsi/st.txt.
1213 panic= [KNL] Kernel behaviour on panic
1214 Format: <timeout>
1216 parkbd.port= [HW] Parallel port number the keyboard adapter is
1217 connected to, default is 0.
1218 Format: <parport#>
1219 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1220 0 for XT, 1 for AT (default is AT).
1221 Format: <mode>
1223 parport= [HW,PPT] Specify parallel ports. 0 disables.
1224 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1225 Use 'auto' to force the driver to use any
1226 IRQ/DMA settings detected (the default is to
1227 ignore detected IRQ/DMA settings because of
1228 possible conflicts). You can specify the base
1229 address, IRQ, and DMA settings; IRQ and DMA
1230 should be numbers, or 'auto' (for using detected
1231 settings on that particular port), or 'nofifo'
1232 (to avoid using a FIFO even if it is detected).
1233 Parallel ports are assigned in the order they
1234 are specified on the command line, starting
1235 with parport0.
1237 parport_init_mode= [HW,PPT]
1238 Configure VIA parallel port to operate in
1239 a specific mode. This is necessary on Pegasos
1240 computer where firmware has no options for setting
1241 up parallel port mode and sets it to spp.
1242 Currently this function knows 686a and 8231 chips.
1243 Format: [spp|ps2|epp|ecp|ecpepp]
1245 pas2= [HW,OSS] Format:
1246 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1248 pas16= [HW,SCSI]
1249 See header of drivers/scsi/pas16.c.
1251 pause_on_oops=
1252 Halt all CPUs after the first oops has been printed for
1253 the specified number of seconds. This is to be used if
1254 your oopses keep scrolling off the screen.
1256 pcbit= [HW,ISDN]
1258 pcd. [PARIDE]
1259 See header of drivers/block/paride/pcd.c.
1260 See also Documentation/paride.txt.
1262 pci=option[,option...] [PCI] various PCI subsystem options:
1263 off [X86-32] don't probe for the PCI bus
1264 bios [X86-32] force use of PCI BIOS, don't access
1265 the hardware directly. Use this if your machine
1266 has a non-standard PCI host bridge.
1267 nobios [X86-32] disallow use of PCI BIOS, only direct
1268 hardware access methods are allowed. Use this
1269 if you experience crashes upon bootup and you
1270 suspect they are caused by the BIOS.
1271 conf1 [X86-32] Force use of PCI Configuration
1272 Mechanism 1.
1273 conf2 [X86-32] Force use of PCI Configuration
1274 Mechanism 2.
1275 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1276 Configuration
1277 nomsi [MSI] If the PCI_MSI kernel config parameter is
1278 enabled, this kernel boot option can be used to
1279 disable the use of MSI interrupts system-wide.
1280 nosort [X86-32] Don't sort PCI devices according to
1281 order given by the PCI BIOS. This sorting is
1282 done to get a device order compatible with
1283 older kernels.
1284 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1285 routing table. These calls are known to be buggy
1286 on several machines and they hang the machine
1287 when used, but on other computers it's the only
1288 way to get the interrupt routing table. Try
1289 this option if the kernel is unable to allocate
1290 IRQs or discover secondary PCI buses on your
1291 motherboard.
1292 rom [X86-32] Assign address space to expansion ROMs.
1293 Use with caution as certain devices share
1294 address decoders between ROMs and other
1295 resources.
1296 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1297 assigned automatically to PCI devices. You can
1298 make the kernel exclude IRQs of your ISA cards
1299 this way.
1300 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1301 of the PIRQ table (normally generated
1302 by the BIOS) if it is outside the
1303 F0000h-100000h range.
1304 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1305 useful if the kernel is unable to find your
1306 secondary buses and you want to tell it
1307 explicitly which ones they are.
1308 assign-busses [X86-32] Always assign all PCI bus
1309 numbers ourselves, overriding
1310 whatever the firmware may have done.
1311 usepirqmask [X86-32] Honor the possible IRQ mask stored
1312 in the BIOS $PIR table. This is needed on
1313 some systems with broken BIOSes, notably
1314 some HP Pavilion N5400 and Omnibook XE3
1315 notebooks. This will have no effect if ACPI
1316 IRQ routing is enabled.
1317 noacpi [X86-32] Do not use ACPI for IRQ routing
1318 or for PCI scanning.
1319 routeirq Do IRQ routing for all PCI devices.
1320 This is normally done in pci_enable_device(),
1321 so this option is a temporary workaround
1322 for broken drivers that don't call it.
1323 firmware [ARM] Do not re-enumerate the bus but instead
1324 just use the configuration from the
1325 bootloader. This is currently used on
1326 IXP2000 systems where the bus has to be
1327 configured a certain way for adjunct CPUs.
1328 noearly [X86] Don't do any early type 1 scanning.
1329 This might help on some broken boards which
1330 machine check when some devices' config space
1331 is read. But various workarounds are disabled
1332 and some IOMMU drivers will not work.
1333 bfsort Sort PCI devices into breadth-first order.
1334 This sorting is done to get a device
1335 order compatible with older (<= 2.4) kernels.
1336 nobfsort Don't sort PCI devices into breadth-first order.
1337 cbiosize=nn[KMG] The fixed amount of bus space which is
1338 reserved for the CardBus bridge's IO window.
1339 The default value is 256 bytes.
1340 cbmemsize=nn[KMG] The fixed amount of bus space which is
1341 reserved for the CardBus bridge's memory
1342 window. The default value is 64 megabytes.
1344 pcmv= [HW,PCMCIA] BadgePAD 4
1346 pd. [PARIDE]
1347 See Documentation/paride.txt.
1349 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1350 boot time.
1351 Format: { 0 | 1 }
1352 See arch/parisc/kernel/pdc_chassis.c
1354 pf. [PARIDE]
1355 See Documentation/paride.txt.
1357 pg. [PARIDE]
1358 See Documentation/paride.txt.
1360 pirq= [SMP,APIC] Manual mp-table setup
1361 See Documentation/i386/IO-APIC.txt.
1363 plip= [PPT,NET] Parallel port network link
1364 Format: { parport<nr> | timid | 0 }
1365 See also Documentation/parport.txt.
1367 pnpacpi= [ACPI]
1368 { off }
1370 pnpbios= [ISAPNP]
1371 { on | off | curr | res | no-curr | no-res }
1373 pnp_reserve_irq=
1374 [ISAPNP] Exclude IRQs for the autoconfiguration
1376 pnp_reserve_dma=
1377 [ISAPNP] Exclude DMAs for the autoconfiguration
1379 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1380 Ranges are in pairs (I/O port base and size).
1382 pnp_reserve_mem=
1383 [ISAPNP] Exclude memory regions for the
1384 autoconfiguration.
1385 Ranges are in pairs (memory base and size).
1387 print-fatal-signals=
1388 [KNL] debug: print fatal signals
1389 print-fatal-signals=1: print segfault info to
1390 the kernel console.
1391 default: off.
1393 printk.time= Show timing data prefixed to each printk message line
1394 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1396 profile= [KNL] Enable kernel profiling via /proc/profile
1397 Format: [schedule,]<number>
1398 Param: "schedule" - profile schedule points.
1399 Param: <number> - step/bucket size as a power of 2 for
1400 statistical time based profiling.
1401 Param: "sleep" - profile D-state sleeping (millisecs)
1403 processor.max_cstate= [HW,ACPI]
1404 Limit processor to maximum C-state
1405 max_cstate=9 overrides any DMI blacklist limit.
1407 processor.nocst [HW,ACPI]
1408 Ignore the _CST method to determine C-states,
1409 instead using the legacy FADT method
1411 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1412 before loading.
1413 See Documentation/ramdisk.txt.
1415 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1416 probe for; one of (bare|imps|exps|lifebook|any).
1417 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1418 per second.
1419 psmouse.resetafter= [HW,MOUSE]
1420 Try to reset the device after so many bad packets
1421 (0 = never).
1422 psmouse.resolution=
1423 [HW,MOUSE] Set desired mouse resolution, in dpi.
1424 psmouse.smartscroll=
1425 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1426 0 = disabled, 1 = enabled (default).
1428 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1429 Format:
1430 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1432 pt. [PARIDE]
1433 See Documentation/paride.txt.
1435 quiet [KNL] Disable most log messages
1437 r128= [HW,DRM]
1439 raid= [HW,RAID]
1440 See Documentation/md.txt.
1442 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1443 See Documentation/ramdisk.txt.
1445 ramdisk_blocksize= [RAM]
1446 See Documentation/ramdisk.txt.
1448 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1449 New name for the ramdisk parameter.
1450 See Documentation/ramdisk.txt.
1452 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1453 RCU callbacks to process in one batch.
1455 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1456 RCU callbacks over which batch limiting is disabled.
1458 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1459 RCU callbacks below which batch limiting is re-enabled.
1461 rdinit= [KNL]
1462 Format: <full_path>
1463 Run specified binary instead of /init from the ramdisk,
1464 used for early userspace startup. See initrd.
1466 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1467 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1468 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1470 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1472 reservetop= [X86-32]
1473 Format: nn[KMG]
1474 Reserves a hole at the top of the kernel virtual
1475 address space.
1477 reset_devices [KNL] Force drivers to reset the underlying device
1478 during initialization.
1480 resume= [SWSUSP]
1481 Specify the partition device for software suspend
1483 resume_offset= [SWSUSP]
1484 Specify the offset from the beginning of the partition
1485 given by "resume=" at which the swap header is located,
1486 in <PAGE_SIZE> units (needed only for swap files).
1487 See Documentation/power/swsusp-and-swap-files.txt
1489 retain_initrd [RAM] Keep initrd memory after extraction
1491 rhash_entries= [KNL,NET]
1492 Set number of hash buckets for route cache
1494 riscom8= [HW,SERIAL]
1495 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1497 ro [KNL] Mount root device read-only on boot
1499 root= [KNL] Root filesystem
1501 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1502 mount the root filesystem
1504 rootflags= [KNL] Set root filesystem mount option string
1506 rootfstype= [KNL] Set root filesystem type
1508 rootwait [KNL] Wait (indefinitely) for root device to show up.
1509 Useful for devices that are detected asynchronously
1510 (e.g. USB and MMC devices).
1512 rw [KNL] Mount root device read-write on boot
1514 S [KNL] Run init in single mode
1516 sa1100ir [NET]
1517 See drivers/net/irda/sa1100_ir.c.
1519 sb= [HW,OSS]
1520 Format: <io>,<irq>,<dma>,<dma2>
1522 sbni= [NET] Granch SBNI12 leased line adapter
1524 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1525 Format: <io>[,<timeout>[,<isapnp>]]
1527 scsi_debug_*= [SCSI]
1528 See drivers/scsi/scsi_debug.c.
1530 scsi_default_dev_flags=
1531 [SCSI] SCSI default device flags
1532 Format: <integer>
1534 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1535 Format: <vendor>:<model>:<flags>
1536 (flags are integer value)
1538 scsi_logging= [SCSI]
1540 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1541 discovered. async scans them in kernel threads,
1542 allowing boot to proceed. none ignores them, expecting
1543 user space to do the scan.
1545 selinux [SELINUX] Disable or enable SELinux at boot time.
1546 Format: { "0" | "1" }
1547 See security/selinux/Kconfig help text.
1548 0 -- disable.
1549 1 -- enable.
1550 Default value is set via kernel config option.
1551 If enabled at boot time, /selinux/disable can be used
1552 later to disable prior to initial policy load.
1554 selinux_compat_net =
1555 [SELINUX] Set initial selinux_compat_net flag value.
1556 Format: { "0" | "1" }
1557 0 -- use new secmark-based packet controls
1558 1 -- use legacy packet controls
1559 Default value is 0 (preferred).
1560 Value can be changed at runtime via
1561 /selinux/compat_net.
1563 serialnumber [BUGS=X86-32]
1565 sg_def_reserved_size= [SCSI]
1567 shapers= [NET]
1568 Maximal number of shapers.
1570 sim710= [SCSI,HW]
1571 See header of drivers/scsi/sim710.c.
1573 simeth= [IA-64]
1574 simscsi=
1576 slram= [HW,MTD]
1578 slub_debug[=options[,slabs]] [MM, SLUB]
1579 Enabling slub_debug allows one to determine the
1580 culprit if slab objects become corrupted. Enabling
1581 slub_debug can create guard zones around objects and
1582 may poison objects when not in use. Also tracks the
1583 last alloc / free. For more information see
1584 Documentation/vm/slub.txt.
1586 slub_max_order= [MM, SLUB]
1587 Determines the maximum allowed order for slabs.
1588 A high setting may cause OOMs due to memory
1589 fragmentation. For more information see
1590 Documentation/vm/slub.txt.
1592 slub_min_objects= [MM, SLUB]
1593 The minimum number of objects per slab. SLUB will
1594 increase the slab order up to slub_max_order to
1595 generate a sufficiently large slab able to contain
1596 the number of objects indicated. The higher the number
1597 of objects the smaller the overhead of tracking slabs
1598 and the less frequently locks need to be acquired.
1599 For more information see Documentation/vm/slub.txt.
1601 slub_min_order= [MM, SLUB]
1602 Determines the mininum page order for slabs. Must be
1603 lower than slub_max_order.
1604 For more information see Documentation/vm/slub.txt.
1606 slub_nomerge [MM, SLUB]
1607 Disable merging of slabs with similar size. May be
1608 necessary if there is some reason to distinguish
1609 allocs to different slabs. Debug options disable
1610 merging on their own.
1611 For more information see Documentation/vm/slub.txt.
1613 smart2= [HW]
1614 Format: <io1>[,<io2>[,...,<io8>]]
1616 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1617 attempt to substitute SMP alternatives once at boot.
1619 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1620 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1621 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1622 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1623 smsc-ircc2.ircc_irq= [HW] IRQ line
1624 smsc-ircc2.ircc_dma= [HW] DMA channel
1625 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1626 0: Toshiba Satellite 1800 (GP data pin select)
1627 1: Fast pin select (default)
1628 2: ATC IRMode
1630 snd-ad1816a= [HW,ALSA]
1632 snd-ad1848= [HW,ALSA]
1634 snd-ali5451= [HW,ALSA]
1636 snd-als100= [HW,ALSA]
1638 snd-als4000= [HW,ALSA]
1640 snd-azt2320= [HW,ALSA]
1642 snd-cmi8330= [HW,ALSA]
1644 snd-cmipci= [HW,ALSA]
1646 snd-cs4231= [HW,ALSA]
1648 snd-cs4232= [HW,ALSA]
1650 snd-cs4236= [HW,ALSA]
1652 snd-cs4281= [HW,ALSA]
1654 snd-cs46xx= [HW,ALSA]
1656 snd-dt019x= [HW,ALSA]
1658 snd-dummy= [HW,ALSA]
1660 snd-emu10k1= [HW,ALSA]
1662 snd-ens1370= [HW,ALSA]
1664 snd-ens1371= [HW,ALSA]
1666 snd-es968= [HW,ALSA]
1668 snd-es1688= [HW,ALSA]
1670 snd-es18xx= [HW,ALSA]
1672 snd-es1938= [HW,ALSA]
1674 snd-es1968= [HW,ALSA]
1676 snd-fm801= [HW,ALSA]
1678 snd-gusclassic= [HW,ALSA]
1680 snd-gusextreme= [HW,ALSA]
1682 snd-gusmax= [HW,ALSA]
1684 snd-hdsp= [HW,ALSA]
1686 snd-ice1712= [HW,ALSA]
1688 snd-intel8x0= [HW,ALSA]
1690 snd-interwave= [HW,ALSA]
1692 snd-interwave-stb=
1693 [HW,ALSA]
1695 snd-korg1212= [HW,ALSA]
1697 snd-maestro3= [HW,ALSA]
1699 snd-mpu401= [HW,ALSA]
1701 snd-mtpav= [HW,ALSA]
1703 snd-nm256= [HW,ALSA]
1705 snd-opl3sa2= [HW,ALSA]
1707 snd-opti92x-ad1848=
1708 [HW,ALSA]
1710 snd-opti92x-cs4231=
1711 [HW,ALSA]
1713 snd-opti93x= [HW,ALSA]
1715 snd-pmac= [HW,ALSA]
1717 snd-rme32= [HW,ALSA]
1719 snd-rme96= [HW,ALSA]
1721 snd-rme9652= [HW,ALSA]
1723 snd-sb8= [HW,ALSA]
1725 snd-sb16= [HW,ALSA]
1727 snd-sbawe= [HW,ALSA]
1729 snd-serial= [HW,ALSA]
1731 snd-sgalaxy= [HW,ALSA]
1733 snd-sonicvibes= [HW,ALSA]
1735 snd-sun-amd7930=
1736 [HW,ALSA]
1738 snd-sun-cs4231= [HW,ALSA]
1740 snd-trident= [HW,ALSA]
1742 snd-usb-audio= [HW,ALSA,USB]
1744 snd-via82xx= [HW,ALSA]
1746 snd-virmidi= [HW,ALSA]
1748 snd-wavefront= [HW,ALSA]
1750 snd-ymfpci= [HW,ALSA]
1752 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1753 See Documentation/sonypi.txt
1755 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1756 See Documentation/specialix.txt.
1758 spia_io_base= [HW,MTD]
1759 spia_fio_base=
1760 spia_pedr=
1761 spia_peddr=
1763 sscape= [HW,OSS]
1764 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1766 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1767 See Documentation/scsi/st.txt.
1769 st0x= [HW,SCSI]
1770 See header of drivers/scsi/seagate.c.
1772 sti= [PARISC,HW]
1773 Format: <num>
1774 Set the STI (builtin display/keyboard on the HP-PARISC
1775 machines) console (graphic card) which should be used
1776 as the initial boot-console.
1777 See also comment in drivers/video/console/sticore.c.
1779 sti_font= [HW]
1780 See comment in drivers/video/console/sticore.c.
1782 stifb= [HW]
1783 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1785 sunrpc.pool_mode=
1786 [NFS]
1787 Control how the NFS server code allocates CPUs to
1788 service thread pools. Depending on how many NICs
1789 you have and where their interrupts are bound, this
1790 option will affect which CPUs will do NFS serving.
1791 Note: this parameter cannot be changed while the
1792 NFS server is running.
1794 auto the server chooses an appropriate mode
1795 automatically using heuristics
1796 global a single global pool contains all CPUs
1797 percpu one pool for each CPU
1798 pernode one pool for each NUMA node (equivalent
1799 to global on non-NUMA machines)
1801 swiotlb= [IA-64] Number of I/O TLB slabs
1803 switches= [HW,M68k]
1805 sym53c416= [HW,SCSI]
1806 See header of drivers/scsi/sym53c416.c.
1808 sysrq_always_enabled
1809 [KNL]
1810 Ignore sysrq setting - this boot parameter will
1811 neutralize any effect of /proc/sys/kernel/sysrq.
1812 Useful for debugging.
1814 t128= [HW,SCSI]
1815 See header of drivers/scsi/t128.c.
1817 tdfx= [HW,DRM]
1819 thash_entries= [KNL,NET]
1820 Set number of hash buckets for TCP connection
1822 thermal.act= [HW,ACPI]
1823 -1: disable all active trip points in all thermal zones
1824 <degrees C>: override all lowest active trip points
1826 thermal.crt= [HW,ACPI]
1827 -1: disable all critical trip points in all thermal zones
1828 <degrees C>: lower all critical trip points
1830 thermal.nocrt= [HW,ACPI]
1831 Set to disable actions on ACPI thermal zone
1832 critical and hot trip points.
1834 thermal.off= [HW,ACPI]
1835 1: disable ACPI thermal control
1837 thermal.psv= [HW,ACPI]
1838 -1: disable all passive trip points
1839 <degrees C>: override all passive trip points to this value
1841 thermal.tzp= [HW,ACPI]
1842 Specify global default ACPI thermal zone polling rate
1843 <deci-seconds>: poll all this frequency
1844 0: no polling (default)
1846 time Show timing data prefixed to each printk message line
1847 [deprecated, see 'printk.time']
1849 tipar.timeout= [HW,PPT]
1850 Set communications timeout in tenths of a second
1851 (default 15).
1853 tipar.delay= [HW,PPT]
1854 Set inter-bit delay in microseconds (default 10).
1856 tmc8xx= [HW,SCSI]
1857 See header of drivers/scsi/seagate.c.
1859 tmscsim= [HW,SCSI]
1860 See comment before function dc390_setup() in
1861 drivers/scsi/tmscsim.c.
1863 tp720= [HW,PS2]
1865 trix= [HW,OSS] MediaTrix AudioTrix Pro
1866 Format:
1867 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1869 tsdev.xres= [TS] Horizontal screen resolution.
1870 tsdev.yres= [TS] Vertical screen resolution.
1872 turbografx.map[2|3]= [HW,JOY]
1873 TurboGraFX parallel port interface
1874 Format:
1875 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1876 See also Documentation/input/joystick-parport.txt
1878 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1879 See header of drivers/scsi/u14-34f.c.
1881 uart401= [HW,OSS]
1882 Format: <io>,<irq>
1884 uart6850= [HW,OSS]
1885 Format: <io>,<irq>
1887 uhci-hcd.ignore_oc=
1888 [USB] Ignore overcurrent events (default N).
1889 Some badly-designed motherboards generate lots of
1890 bogus events, for ports that aren't wired to
1891 anything. Set this parameter to avoid log spamming.
1892 Note that genuine overcurrent events won't be
1893 reported either.
1895 usbcore.autosuspend=
1896 [USB] The autosuspend time delay (in seconds) used
1897 for newly-detected USB devices (default 2). This
1898 is the time required before an idle device will be
1899 autosuspended. Devices for which the delay is set
1900 to a negative value won't be autosuspended at all.
1902 usbhid.mousepoll=
1903 [USBHID] The interval which mice are to be polled at.
1905 vdso= [X86-32,SH,x86-64]
1906 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1907 vdso=1: enable VDSO (default)
1908 vdso=0: disable VDSO mapping
1910 vector= [IA-64,SMP]
1911 vector=percpu: enable percpu vector domain
1913 video= [FB] Frame buffer configuration
1914 See Documentation/fb/modedb.txt.
1916 vga= [BOOT,X86-32] Select a particular video mode
1917 See Documentation/i386/boot.txt and
1918 Documentation/svga.txt.
1919 Use vga=ask for menu.
1920 This is actually a boot loader parameter; the value is
1921 passed to the kernel using a special protocol.
1923 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1924 size of <nn>. This can be used to increase the
1925 minimum size (128MB on x86). It can also be used to
1926 decrease the size and leave more room for directly
1927 mapped kernel RAM.
1929 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1930 Format: <command>
1932 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1933 Format: <command>
1935 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1936 Format: <command>
1938 waveartist= [HW,OSS]
1939 Format: <io>,<irq>,<dma>,<dma2>
1941 wd33c93= [HW,SCSI]
1942 See header of drivers/scsi/wd33c93.c.
1944 wd7000= [HW,SCSI]
1945 See header of drivers/scsi/wd7000.c.
1947 wdt= [WDT] Watchdog
1948 See Documentation/watchdog/wdt.txt.
1950 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1951 xd_geo= See header of drivers/block/xd.c.
1953 xirc2ps_cs= [NET,PCMCIA]
1954 Format:
1955 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1957 norandmaps Don't use address space randomization
1958 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1960 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1961 This is useful to get more information why
1962 you got a "dwarf2 unwinder stuck"
1964 ______________________________________________________________________
1966 TODO:
1968 Add documentation for ALSA options.
1969 Add more DRM drivers.