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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 DRM Direct Rendering Management support is enabled.
38 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
39 EFI EFI Partitioning (GPT) is enabled
40 EIDE EIDE/ATAPI support is enabled.
41 FB The frame buffer device is enabled.
42 HW Appropriate hardware is enabled.
43 IA-32 IA-32 aka i386 architecture 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 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
67 PARIDE The ParIDE 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 X86-64 X86-64 architecture is enabled.
95 More X86-64 boot options can be found in
96 Documentation/x86_64/boot-options.txt .
98 In addition, the following text indicates that the option:
100 BUGS= Relates to possible processor bugs on the said processor.
101 KNL Is a kernel start-up parameter.
102 BOOT Is a boot loader parameter.
104 Parameters denoted with BOOT are actually interpreted by the boot
105 loader, and have no meaning to the kernel directly.
106 Do not modify the syntax of boot loader parameters without extreme
107 need or coordination with <Documentation/i386/boot.txt>.
109 There are also arch-specific kernel-parameters not documented here.
110 See for example <Documentation/x86_64/boot-options.txt>.
112 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
113 a trailing = on the name of any parameter states that that parameter will
114 be entered as an environment variable, whereas its absence indicates that
115 it will appear as a kernel argument readable via /proc/cmdline by programs
116 running once the system is up.
118 The number of kernel parameters is not limited, but the length of the
119 complete command line (parameters including spaces etc.) is limited to
120 a fixed number of characters. This limit depends on the architecture
121 and is between 256 and 4096 characters. It is defined in the file
122 ./include/asm/setup.h as COMMAND_LINE_SIZE.
125 53c7xx= [HW,SCSI] Amiga SCSI controllers
126 See header of drivers/scsi/53c7xx.c.
127 See also Documentation/scsi/ncr53c7xx.txt.
129 acpi= [HW,ACPI,X86-64,i386]
130 Advanced Configuration and Power Interface
131 Format: { force | off | ht | strict | noirq }
132 force -- enable ACPI if default was off
133 off -- disable ACPI if default was on
134 noirq -- do not use ACPI for IRQ routing
135 ht -- run only enough ACPI to enable Hyper Threading
136 strict -- Be less tolerant of platforms that are not
137 strictly ACPI specification compliant.
139 See also Documentation/pm.txt, pci=noacpi
141 acpi_apic_instance= [ACPI, IOAPIC]
142 Format: <int>
143 2: use 2nd APIC table, if available
144 1,0: use 1st APIC table
145 default: 0
147 acpi_sleep= [HW,ACPI] Sleep options
148 Format: { s3_bios, s3_mode }
149 See Documentation/power/video.txt
151 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
152 Format: { level | edge | high | low }
154 acpi_irq_balance [HW,ACPI]
155 ACPI will balance active IRQs
156 default in APIC mode
158 acpi_irq_nobalance [HW,ACPI]
159 ACPI will not move active IRQs (default)
160 default in PIC mode
162 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
163 use by PCI
164 Format: <irq>,<irq>...
166 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
167 Format: <irq>,<irq>...
169 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
170 Format: To spoof as Windows 98: ="Microsoft Windows"
172 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
173 acpi_osi="string1" # add string1 -- only one string
174 acpi_osi="!string2" # remove built-in string2
175 acpi_osi= # disable all strings
177 acpi_serialize [HW,ACPI] force serialization of AML methods
179 acpi_skip_timer_override [HW,ACPI]
180 Recognize and ignore IRQ0/pin2 Interrupt Override.
181 For broken nForce2 BIOS resulting in XT-PIC timer.
182 acpi_use_timer_override [HW,ACPI}
183 Use timer override. For some broken Nvidia NF5 boards
184 that require a timer override, but don't have
185 HPET
187 acpi.debug_layer= [HW,ACPI]
188 Format: <int>
189 Each bit of the <int> indicates an ACPI debug layer,
190 1: enable, 0: disable. It is useful for boot time
191 debugging. After system has booted up, it can be set
192 via /sys/module/acpi/parameters/debug_layer.
193 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
194 Available bits (add the numbers together) to enable debug output
195 for specific parts of the ACPI subsystem:
196 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
197 0x10 namespace 0x20 parser 0x40 dispatcher
198 0x80 executer 0x100 resources 0x200 acpica debugger
199 0x400 os services 0x800 acpica disassembler.
200 The number can be in decimal or prefixed with 0x in hex.
201 Warning: Many of these options can produce a lot of
202 output and make your system unusable. Be very careful.
204 acpi.debug_level= [HW,ACPI]
205 Format: <int>
206 Each bit of the <int> indicates an ACPI debug level,
207 1: enable, 0: disable. It is useful for boot time
208 debugging. After system has booted up, it can be set
209 via /sys/module/acpi/parameters/debug_level.
210 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
211 Available bits (add the numbers together) to enable different
212 debug output levels of the ACPI subsystem:
213 0x01 error 0x02 warn 0x04 init 0x08 debug object
214 0x10 info 0x20 init names 0x40 parse 0x80 load
215 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
216 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
217 0x10000 resources 0x20000 user requests 0x40000 package.
218 The number can be in decimal or prefixed with 0x in hex.
219 Warning: Many of these options can produce a lot of
220 output and make your system unusable. Be very careful.
223 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
225 acpi_pm_good [IA-32,X86-64]
226 Override the pmtimer bug detection: force the kernel
227 to assume that this machine's pmtimer latches its value
228 and always returns good values.
230 enable_timer_pin_1 [i386,x86-64]
231 Enable PIN 1 of APIC timer
232 Can be useful to work around chipset bugs
233 (in particular on some ATI chipsets).
234 The kernel tries to set a reasonable default.
236 disable_timer_pin_1 [i386,x86-64]
237 Disable PIN 1 of APIC timer
238 Can be useful to work around chipset bugs.
240 ad1848= [HW,OSS]
241 Format: <io>,<irq>,<dma>,<dma2>,<type>
243 advansys= [HW,SCSI]
244 See header of drivers/scsi/advansys.c.
246 advwdt= [HW,WDT] Advantech WDT
247 Format: <iostart>,<iostop>
249 aedsp16= [HW,OSS] Audio Excel DSP 16
250 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
251 See also header of sound/oss/aedsp16.c.
253 aha152x= [HW,SCSI]
254 See Documentation/scsi/aha152x.txt.
256 aha1542= [HW,SCSI]
257 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
259 aic7xxx= [HW,SCSI]
260 See Documentation/scsi/aic7xxx.txt.
262 aic79xx= [HW,SCSI]
263 See Documentation/scsi/aic79xx.txt.
265 amijoy.map= [HW,JOY] Amiga joystick support
266 Map of devices attached to JOY0DAT and JOY1DAT
267 Format: <a>,<b>
268 See also Documentation/kernel/input/joystick.txt
270 analog.map= [HW,JOY] Analog joystick and gamepad support
271 Specifies type or capabilities of an analog joystick
272 connected to one of 16 gameports
273 Format: <type1>,<type2>,..<type16>
275 apc= [HW,SPARC]
276 Power management functions (SPARCstation-4/5 + deriv.)
277 Format: noidle
278 Disable APC CPU standby support. SPARCstation-Fox does
279 not play well with APC CPU idle - disable it if you have
280 APC and your system crashes randomly.
282 apic= [APIC,i386] Change the output verbosity whilst booting
283 Format: { quiet (default) | verbose | debug }
284 Change the amount of debugging information output
285 when initialising the APIC and IO-APIC components.
287 apm= [APM] Advanced Power Management
288 See header of arch/i386/kernel/apm.c.
290 applicom= [HW]
291 Format: <mem>,<irq>
293 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
294 Format: <io>,<irq>,<nodeID>
296 ataflop= [HW,M68k]
298 atarimouse= [HW,MOUSE] Atari Mouse
300 atascsi= [HW,SCSI] Atari SCSI
302 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
303 EzKey and similar keyboards
305 atkbd.reset= [HW] Reset keyboard during initialization
307 atkbd.set= [HW] Select keyboard code set
308 Format: <int> (2 = AT (default), 3 = PS/2)
310 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
311 keyboards
313 atkbd.softraw= [HW] Choose between synthetic and real raw mode
314 Format: <bool> (0 = real, 1 = synthetic (default))
316 atkbd.softrepeat= [HW]
317 Use software keyboard repeat
319 autotest [IA64]
321 baycom_epp= [HW,AX25]
322 Format: <io>,<mode>
324 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
325 Format: <io>,<mode>
326 See header of drivers/net/hamradio/baycom_par.c.
328 baycom_ser_fdx= [HW,AX25]
329 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
330 Format: <io>,<irq>,<mode>[,<baud>]
331 See header of drivers/net/hamradio/baycom_ser_fdx.c.
333 baycom_ser_hdx= [HW,AX25]
334 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
335 Format: <io>,<irq>,<mode>
336 See header of drivers/net/hamradio/baycom_ser_hdx.c.
338 blkmtd_device= [HW,MTD]
339 blkmtd_erasesz=
340 blkmtd_ro=
341 blkmtd_bs=
342 blkmtd_count=
344 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
345 bttv.radio= Most important insmod options are available as
346 kernel args too.
347 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
348 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
350 BusLogic= [HW,SCSI]
351 See drivers/scsi/BusLogic.c, comment before function
352 BusLogic_ParseDriverOptions().
354 c101= [NET] Moxa C101 synchronous serial card
356 cachesize= [BUGS=IA-32] Override level 2 CPU cache size detection.
357 Sometimes CPU hardware bugs make them report the cache
358 size incorrectly. The kernel will attempt work arounds
359 to fix known problems, but for some CPUs it is not
360 possible to determine what the correct size should be.
361 This option provides an override for these situations.
363 chandev= [HW,NET] Generic channel device initialisation
365 checkreqprot [SELINUX] Set initial checkreqprot flag value.
366 Format: { "0" | "1" }
367 See security/selinux/Kconfig help text.
368 0 -- check protection applied by kernel (includes
369 any implied execute protection).
370 1 -- check protection requested by application.
371 Default value is set via a kernel config option.
372 Value can be changed at runtime via
373 /selinux/checkreqprot.
375 clock= [BUGS=IA-32, HW] gettimeofday clocksource override.
376 [Deprecated]
377 Forces specified clocksource (if available) to be used
378 when calculating gettimeofday(). If specified
379 clocksource is not available, it defaults to PIT.
380 Format: { pit | tsc | cyclone | pmtmr }
382 clocksource= [GENERIC_TIME] Override the default clocksource
383 Format: <string>
384 Override the default clocksource and use the clocksource
385 with the name specified.
386 Some clocksource names to choose from, depending on
387 the platform:
388 [all] jiffies (this is the base, fallback clocksource)
389 [ACPI] acpi_pm
390 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
391 pxa_timer,timer3,32k_counter,timer0_1
392 [AVR32] avr32
393 [IA-32] pit,hpet,tsc,vmi-timer;
394 scx200_hrt on Geode; cyclone on IBM x440
395 [MIPS] MIPS
396 [PARISC] cr16
397 [S390] tod
398 [SH] SuperH
399 [SPARC64] tick
400 [X86-64] hpet,tsc
402 code_bytes [IA32] How many bytes of object code to print in an
403 oops report.
404 Range: 0 - 8192
405 Default: 64
407 disable_8254_timer
408 enable_8254_timer
409 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
410 over the 8254 in addition to over the IO-APIC. The
411 kernel tries to set a sensible default.
413 hpet= [IA-32,HPET] option to disable HPET and use PIT.
414 Format: disable
416 com20020= [HW,NET] ARCnet - COM20020 chipset
417 Format:
418 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
420 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
421 Format: <io>[,<irq>]
423 com90xx= [HW,NET]
424 ARCnet - COM90xx chipset (memory-mapped buffers)
425 Format: <io>[,<irq>[,<memstart>]]
427 condev= [HW,S390] console device
428 conmode=
430 console= [KNL] Output console device and options.
432 tty<n> Use the virtual console device <n>.
434 ttyS<n>[,options]
435 ttyUSB0[,options]
436 Use the specified serial port. The options are of
437 the form "bbbbpnf", where "bbbb" is the baud rate,
438 "p" is parity ("n", "o", or "e"), "n" is number of
439 bits, and "f" is flow control ("r" for RTS or
440 omit it). Default is "9600n8".
442 See Documentation/serial-console.txt for more
443 information. See
444 Documentation/networking/netconsole.txt for an
445 alternative.
447 uart[8250],io,<addr>[,options]
448 uart[8250],mmio,<addr>[,options]
449 Start an early, polled-mode console on the 8250/16550
450 UART at the specified I/O port or MMIO address,
451 switching to the matching ttyS device later. The
452 options are the same as for ttyS, above.
454 earlycon= [KNL] Output early console device and options.
455 uart[8250],io,<addr>[,options]
456 uart[8250],mmio,<addr>[,options]
457 Start an early, polled-mode console on the 8250/16550
458 UART at the specified I/O port or MMIO address.
459 The options are the same as for ttyS, above.
461 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
462 Format:
463 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
465 cpia_pp= [HW,PPT]
466 Format: { parport<nr> | auto | none }
468 crashkernel=nn[KMG]@ss[KMG]
469 [KNL] Reserve a chunk of physical memory to
470 hold a kernel to switch to with kexec on panic.
472 cs4232= [HW,OSS]
473 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
475 cs89x0_dma= [HW,NET]
476 Format: <dma>
478 cs89x0_media= [HW,NET]
479 Format: { rj45 | aui | bnc }
481 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
483 dasd= [HW,NET]
484 See header of drivers/s390/block/dasd_devmap.c.
486 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
487 (one device per port)
488 Format: <port#>,<type>
489 See also Documentation/input/joystick-parport.txt
491 debug [KNL] Enable kernel debugging (events log level).
493 debug_locks_verbose=
494 [KNL] verbose self-tests
495 Format=<0|1>
496 Print debugging info while doing the locking API
497 self-tests.
498 We default to 0 (no extra messages), setting it to
499 1 will print _a lot_ more information - normally
500 only useful to kernel developers.
502 decnet= [HW,NET]
503 Format: <area>[,<node>]
504 See also Documentation/networking/decnet.txt.
506 default_blu= [VT]
507 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
508 Change the default blue palette of the console.
509 This is a 16-member array composed of values
510 ranging from 0-255.
512 default_grn= [VT]
513 Format: <green0>,<green1>,<green2>,...,<green15>
514 Change the default green palette of the console.
515 This is a 16-member array composed of values
516 ranging from 0-255.
518 default_red= [VT]
519 Format: <red0>,<red1>,<red2>,...,<red15>
520 Change the default red palette of the console.
521 This is a 16-member array composed of values
522 ranging from 0-255.
524 default_utf8= [VT]
525 Format=<0|1>
526 Set system-wide default UTF-8 mode for all tty's.
527 Default is 0 and by setting to 1, it enables UTF-8
528 mode for all newly opened or allocated terminals.
530 dhash_entries= [KNL]
531 Set number of hash buckets for dentry cache.
533 digi= [HW,SERIAL]
534 IO parameters + enable/disable command.
536 digiepca= [HW,SERIAL]
537 See drivers/char/README.epca and
538 Documentation/digiepca.txt.
540 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
541 support available.
542 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
544 dmasound= [HW,OSS] Sound subsystem buffers
546 dscc4.setup= [NET]
548 dtc3181e= [HW,SCSI]
550 earlyprintk= [IA-32,X86-64,SH]
551 earlyprintk=vga
552 earlyprintk=serial[,ttySn[,baudrate]]
554 Append ",keep" to not disable it when the real console
555 takes over.
557 Only vga or serial at a time, not both.
559 Currently only ttyS0 and ttyS1 are supported.
561 Interaction with the standard serial driver is not
562 very good.
564 The VGA output is eventually overwritten by the real
565 console.
567 eata= [HW,SCSI]
569 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
570 Format: <int>
571 0: polling mode
572 non-0: interrupt mode (default)
574 eda= [HW,PS2]
576 edb= [HW,PS2]
578 edd= [EDD]
579 Format: {"of[f]" | "sk[ipmbr]"}
580 See comment in arch/i386/boot/edd.S
582 eicon= [HW,ISDN]
583 Format: <id>,<membase>,<irq>
585 eisa_irq_edge= [PARISC,HW]
586 See header of drivers/parisc/eisa.c.
588 elanfreq= [IA-32]
589 See comment before function elanfreq_setup() in
590 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
592 elevator= [IOSCHED]
593 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
594 See Documentation/block/as-iosched.txt and
595 Documentation/block/deadline-iosched.txt for details.
597 elfcorehdr= [IA-32, X86_64]
598 Specifies physical address of start of kernel core
599 image elf header. Generally kexec loader will
600 pass this option to capture kernel.
601 See Documentation/kdump/kdump.txt for details.
603 enforcing [SELINUX] Set initial enforcing status.
604 Format: {"0" | "1"}
605 See security/selinux/Kconfig help text.
606 0 -- permissive (log only, no denials).
607 1 -- enforcing (deny and log).
608 Default value is 0.
609 Value can be changed at runtime via /selinux/enforce.
611 es1371= [HW,OSS]
612 Format: <spdif>,[<nomix>,[<amplifier>]]
613 See also header of sound/oss/es1371.c.
615 ether= [HW,NET] Ethernet cards parameters
616 This option is obsoleted by the "netdev=" option, which
617 has equivalent usage. See its documentation for details.
619 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
620 Format: <io>[,<irq>]
622 failslab=
623 fail_page_alloc=
624 fail_make_request=[KNL]
625 General fault injection mechanism.
626 Format: <interval>,<probability>,<space>,<times>
627 See also /Documentation/fault-injection/.
629 fd_mcs= [HW,SCSI]
630 See header of drivers/scsi/fd_mcs.c.
632 fdomain= [HW,SCSI]
633 See header of drivers/scsi/fdomain.c.
635 floppy= [HW]
636 See Documentation/floppy.txt.
638 gamecon.map[2|3]=
639 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
640 support via parallel port (up to 5 devices per port)
641 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
642 See also Documentation/input/joystick-parport.txt
644 gamma= [HW,DRM]
646 gdth= [HW,SCSI]
647 See header of drivers/scsi/gdth.c.
649 gpt [EFI] Forces disk with valid GPT signature but
650 invalid Protective MBR to be treated as GPT.
652 gvp11= [HW,SCSI]
654 hashdist= [KNL,NUMA] Large hashes allocated during boot
655 are distributed across NUMA nodes. Defaults on
656 for IA-64, off otherwise.
657 Format: 0 | 1 (for off | on)
659 hcl= [IA-64] SGI's Hardware Graph compatibility layer
661 hd= [EIDE] (E)IDE hard drive subsystem geometry
662 Format: <cyl>,<head>,<sect>
664 hd?= [HW] (E)IDE subsystem
665 hd?lun= See Documentation/ide.txt.
667 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
668 size of <nn>. This works even on boxes that have no
669 highmem otherwise. This also works to reduce highmem
670 size on bigger boxes.
672 highres= [KNL] Enable/disable high resolution timer mode.
673 Valid parameters: "on", "off"
674 Default: "on"
676 hisax= [HW,ISDN]
677 See Documentation/isdn/README.HiSax.
679 hugepages= [HW,IA-32,IA-64] Maximal number of HugeTLB pages.
681 i8042.direct [HW] Put keyboard port into non-translated mode
682 i8042.dumbkbd [HW] Pretend that controller can only read data from
683 keyboard and cannot control its state
684 (Don't attempt to blink the leds)
685 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
686 i8042.nokbd [HW] Don't check/create keyboard port
687 i8042.nomux [HW] Don't check presence of an active multiplexing
688 controller
689 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
690 controllers
691 i8042.panicblink=
692 [HW] Frequency with which keyboard LEDs should blink
693 when kernel panics (default is 0.5 sec)
694 i8042.reset [HW] Reset the controller during init and cleanup
695 i8042.unlock [HW] Unlock (ignore) the keylock
697 i810= [HW,DRM]
699 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
700 indicates that the driver is running on unsupported
701 hardware.
702 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
703 does not match list of supported models.
704 i8k.power_status
705 [HW] Report power status in /proc/i8k
706 (disabled by default)
707 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
708 capability is set.
710 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
711 See Documentation/mca.txt.
713 icn= [HW,ISDN]
714 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
716 ide= [HW] (E)IDE subsystem
717 Format: ide=nodma or ide=doubler or ide=reverse
718 See Documentation/ide.txt.
720 ide?= [HW] (E)IDE subsystem
721 Format: ide?=noprobe or chipset specific parameters.
722 See Documentation/ide.txt.
724 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
725 See Documentation/ide.txt.
727 idle= [X86]
728 Format: idle=poll or idle=mwait
729 Poll forces a polling idle loop that can slightly improves the performance
730 of waking up a idle CPU, but will use a lot of power and make the system
731 run hot. Not recommended.
732 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
733 to not use it because it doesn't save as much power as a normal idle
734 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
735 as idle=poll.
737 ignore_loglevel [KNL]
738 Ignore loglevel setting - this will print /all/
739 kernel messages to the console. Useful for debugging.
741 ihash_entries= [KNL]
742 Set number of hash buckets for inode cache.
744 in2000= [HW,SCSI]
745 See header of drivers/scsi/in2000.c.
747 init= [KNL]
748 Format: <full_path>
749 Run specified binary instead of /sbin/init as init
750 process.
752 initcall_debug [KNL] Trace initcalls as they are executed. Useful
753 for working out where the kernel is dying during
754 startup.
756 initrd= [BOOT] Specify the location of the initial ramdisk
758 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
759 Format: <irq>
761 inttest= [IA64]
763 io7= [HW] IO7 for Marvel based alpha systems
764 See comment before marvel_specify_io7 in
765 arch/alpha/kernel/core_marvel.c.
767 ip= [IP_PNP]
768 See Documentation/nfsroot.txt.
770 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
771 See comment before ip2_setup() in drivers/char/ip2.c.
773 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
774 See header of drivers/scsi/ips.c.
776 ports= [IP_VS_FTP] IPVS ftp helper module
777 Default is 21.
778 Up to 8 (IP_VS_APP_MAX_PORTS) ports
779 may be specified.
780 Format: <port>,<port>....
782 irqfixup [HW]
783 When an interrupt is not handled search all handlers
784 for it. Intended to get systems with badly broken
785 firmware running.
787 irqpoll [HW]
788 When an interrupt is not handled search all handlers
789 for it. Also check all handlers each timer
790 interrupt. Intended to get systems with badly broken
791 firmware running.
793 isapnp= [ISAPNP]
794 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
796 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
797 Format:
798 <cpu number>,...,<cpu number>
799 or
800 <cpu number>-<cpu number> (must be a positive range in ascending order)
801 or a mixture
802 <cpu number>,...,<cpu number>-<cpu number>
803 This option can be used to specify one or more CPUs
804 to isolate from the general SMP balancing and scheduling
805 algorithms. The only way to move a process onto or off
806 an "isolated" CPU is via the CPU affinity syscalls.
807 <cpu number> begins at 0 and the maximum value is
808 "number of CPUs in system - 1".
810 This option is the preferred way to isolate CPUs. The
811 alternative -- manually setting the CPU mask of all
812 tasks in the system -- can cause problems and
813 suboptimal load balancer performance.
815 iucv= [HW,NET]
817 js= [HW,JOY] Analog joystick
818 See Documentation/input/joystick.txt.
820 kernelcore=nn[KMG] [KNL,IA-32,IA-64,PPC,X86-64] This parameter
821 specifies the amount of memory usable by the kernel
822 for non-movable allocations. The requested amount is
823 spread evenly throughout all nodes in the system. The
824 remaining memory in each node is used for Movable
825 pages. In the event, a node is too small to have both
826 kernelcore and Movable pages, kernelcore pages will
827 take priority and other nodes will have a larger number
828 of kernelcore pages. The Movable zone is used for the
829 allocation of pages that may be reclaimed or moved
830 by the page migration subsystem. This means that
831 HugeTLB pages may not be allocated from this zone.
832 Note that allocations like PTEs-from-HighMem still
833 use the HighMem zone if it exists, and the Normal
834 zone if it does not.
836 movablecore=nn[KMG] [KNL,IA-32,IA-64,PPC,X86-64] This parameter
837 is similar to kernelcore except it specifies the
838 amount of memory used for migratable allocations.
839 If both kernelcore and movablecore is specified,
840 then kernelcore will be at *least* the specified
841 value but may be more. If movablecore on its own
842 is specified, the administrator must be careful
843 that the amount of memory usable for all allocations
844 is not too small.
846 keepinitrd [HW,ARM]
848 kstack=N [IA-32,X86-64] Print N words from the kernel stack
849 in oops dumps.
851 l2cr= [PPC]
853 lapic [IA-32,APIC] Enable the local APIC even if BIOS
854 disabled it.
856 lapic_timer_c2_ok [IA-32,x86-64,APIC] trust the local apic timer in
857 C2 power state.
859 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
860 Format: addr:<io>,irq:<irq>
862 legacy_serial.force [HW,IA-32,X86-64]
863 Probe for COM ports at legacy addresses even
864 if PNPBIOS or ACPI should describe them. This
865 is for working around firmware defects.
867 llsc*= [IA64] See function print_params() in
868 arch/ia64/sn/kernel/llsc4.c.
870 load_ramdisk= [RAM] List of ramdisks to load from floppy
871 See Documentation/ramdisk.txt.
873 lockd.nlm_grace_period=P [NFS] Assign grace period.
874 Format: <integer>
876 lockd.nlm_tcpport=N [NFS] Assign TCP port.
877 Format: <integer>
879 lockd.nlm_timeout=T [NFS] Assign timeout value.
880 Format: <integer>
882 lockd.nlm_udpport=M [NFS] Assign UDP port.
883 Format: <integer>
885 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
886 Format: <irq>
888 loglevel= All Kernel Messages with a loglevel smaller than the
889 console loglevel will be printed to the console. It can
890 also be changed with klogd or other programs. The
891 loglevels are defined as follows:
893 0 (KERN_EMERG) system is unusable
894 1 (KERN_ALERT) action must be taken immediately
895 2 (KERN_CRIT) critical conditions
896 3 (KERN_ERR) error conditions
897 4 (KERN_WARNING) warning conditions
898 5 (KERN_NOTICE) normal but significant condition
899 6 (KERN_INFO) informational
900 7 (KERN_DEBUG) debug-level messages
902 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
903 Format: { n | nk | nM }
904 n must be a power of two. The default size
905 is set in the kernel config file.
907 lp=0 [LP] Specify parallel ports to use, e.g,
908 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
909 lp=reset first parallel port). 'lp=0' disables the
910 lp=auto printer driver. 'lp=reset' (which can be
911 specified in addition to the ports) causes
912 attached printers to be reset. Using
913 lp=port1,port2,... specifies the parallel ports
914 to associate lp devices with, starting with
915 lp0. A port specification may be 'none' to skip
916 that lp device, or a parport name such as
917 'parport0'. Specifying 'lp=auto' instead of a
918 port specification list means that device IDs
919 from each port should be examined, to see if
920 an IEEE 1284-compliant printer is attached; if
921 so, the driver will manage that printer.
922 See also header of drivers/char/lp.c.
924 lpj=n [KNL]
925 Sets loops_per_jiffy to given constant, thus avoiding
926 time-consuming boot-time autodetection (up to 250 ms per
927 CPU). 0 enables autodetection (default). To determine
928 the correct value for your kernel, boot with normal
929 autodetection and see what value is printed. Note that
930 on SMP systems the preset will be applied to all CPUs,
931 which is likely to cause problems if your CPUs need
932 significantly divergent settings. An incorrect value
933 will cause delays in the kernel to be wrong, leading to
934 unpredictable I/O errors and other breakage. Although
935 unlikely, in the extreme case this might damage your
936 hardware.
938 ltpc= [NET]
939 Format: <io>,<irq>,<dma>
941 mac5380= [HW,SCSI] Format:
942 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
944 mac53c9x= [HW,SCSI] Format:
945 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
947 machvec= [IA64] Force the use of a particular machine-vector
948 (machvec) in a generic kernel.
949 Example: machvec=hpzx1_swiotlb
951 max_loop= [LOOP] Maximum number of loopback devices that can
952 be mounted
953 Format: <1-256>
955 maxcpus= [SMP] Maximum number of processors that an SMP kernel
956 should make use of.
957 Using "nosmp" or "maxcpus=0" will disable SMP
958 entirely (the MPS table probe still happens, though).
959 A command-line option of "maxcpus=<NUM>", where <NUM>
960 is an integer greater than 0, limits the maximum number
961 of CPUs activated in SMP mode to <NUM>.
962 Using "maxcpus=1" on an SMP kernel is the trivial
963 case of an SMP kernel with only one CPU.
965 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
966 equal to this physical address is ignored.
968 max_luns= [SCSI] Maximum number of LUNs to probe.
969 Should be between 1 and 2^32-1.
971 max_report_luns=
972 [SCSI] Maximum number of LUNs received.
973 Should be between 1 and 16384.
975 mca-pentium [BUGS=IA-32]
977 mcatest= [IA-64]
979 mce [IA-32] Machine Check Exception
981 md= [HW] RAID subsystems devices and level
982 See Documentation/md.txt.
984 mdacon= [MDA]
985 Format: <first>,<last>
986 Specifies range of consoles to be captured by the MDA.
988 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
989 Amount of memory to be used when the kernel is not able
990 to see the whole system memory or for test.
991 [IA-32] Use together with memmap= to avoid physical
992 address space collisions. Without memmap= PCI devices
993 could be placed at addresses belonging to unused RAM.
995 mem=nopentium [BUGS=IA-32] Disable usage of 4MB pages for kernel
996 memory.
998 memmap=exactmap [KNL,IA-32,X86_64] Enable setting of an exact
999 E820 memory map, as specified by the user.
1000 Such memmap=exactmap lines can be constructed based on
1001 BIOS output or other requirements. See the memmap=nn@ss
1002 option description.
1004 memmap=nn[KMG]@ss[KMG]
1005 [KNL] Force usage of a specific region of memory
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 ACPI data.
1010 Region of memory to be used, from ss to ss+nn.
1012 memmap=nn[KMG]$ss[KMG]
1013 [KNL,ACPI] Mark specific memory as reserved.
1014 Region of memory to be used, from ss to ss+nn.
1016 meye.*= [HW] Set MotionEye Camera parameters
1017 See Documentation/video4linux/meye.txt.
1019 mga= [HW,DRM]
1021 mousedev.tap_time=
1022 [MOUSE] Maximum time between finger touching and
1023 leaving touchpad surface for touch to be considered
1024 a tap and be reported as a left button click (for
1025 touchpads working in absolute mode only).
1026 Format: <msecs>
1027 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1028 reporting absolute coordinates, such as tablets
1029 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1030 reporting absolute coordinates, such as tablets
1032 mpu401= [HW,OSS]
1033 Format: <io>,<irq>
1035 MTD_Partition= [MTD]
1036 Format: <name>,<region-number>,<size>,<offset>
1038 MTD_Region= [MTD] Format:
1039 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1041 mtdparts= [MTD]
1042 See drivers/mtd/cmdline.c.
1044 mtouchusb.raw_coordinates=
1045 [HW] Make the MicroTouch USB driver use raw coordinates
1046 ('y', default) or cooked coordinates ('n')
1048 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1050 NCR_D700= [HW,SCSI]
1051 See header of drivers/scsi/NCR_D700.c.
1053 ncr5380= [HW,SCSI]
1055 ncr53c400= [HW,SCSI]
1057 ncr53c400a= [HW,SCSI]
1059 ncr53c406a= [HW,SCSI]
1061 ncr53c8xx= [HW,SCSI]
1063 netdev= [NET] Network devices parameters
1064 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1065 Note that mem_start is often overloaded to mean
1066 something different and driver-specific.
1067 This usage is only documented in each driver source
1068 file if at all.
1070 nfsaddrs= [NFS]
1071 See Documentation/nfsroot.txt.
1073 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1074 See Documentation/nfsroot.txt.
1076 nfs.callback_tcpport=
1077 [NFS] set the TCP port on which the NFSv4 callback
1078 channel should listen.
1080 nfs.idmap_cache_timeout=
1081 [NFS] set the maximum lifetime for idmapper cache
1082 entries.
1084 nmi_watchdog= [KNL,BUGS=IA-32] Debugging features for SMP kernels
1086 no387 [BUGS=IA-32] Tells the kernel to use the 387 maths
1087 emulation library even if a 387 maths coprocessor
1088 is present.
1090 noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1091 when set.
1092 Format: <int>
1094 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1095 caches in the slab allocator. Saves per-node memory,
1096 but will impact performance.
1098 noalign [KNL,ARM]
1100 noapic [SMP,APIC] Tells the kernel to not make use of any
1101 IOAPICs that may be present in the system.
1103 noasync [HW,M68K] Disables async and sync negotiation for
1104 all devices.
1106 nobats [PPC] Do not use BATs for mapping kernel lowmem
1107 on "Classic" PPC cores.
1109 nocache [ARM]
1111 nodelayacct [KNL] Disable per-task delay accounting
1113 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1115 noexec [IA-64]
1117 noexec [IA-32,X86-64]
1118 noexec=on: enable non-executable mappings (default)
1119 noexec=off: disable nn-executable mappings
1121 nofxsr [BUGS=IA-32] Disables x86 floating point extended
1122 register save and restore. The kernel will only save
1123 legacy floating-point registers on task switch.
1125 nohlt [BUGS=ARM]
1127 no-hlt [BUGS=IA-32] Tells the kernel that the hlt
1128 instruction doesn't work correctly and not to
1129 use it.
1131 nohalt [IA-64] Tells the kernel not to use the power saving
1132 function PAL_HALT_LIGHT when idle. This increases
1133 power-consumption. On the positive side, it reduces
1134 interrupt wake-up latency, which may improve performance
1135 in certain environments such as networked servers or
1136 real-time systems.
1138 nohz= [KNL] Boottime enable/disable dynamic ticks
1139 Valid arguments: on, off
1140 Default: on
1142 noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing
1144 noirqdebug [IA-32] Disables the code which attempts to detect and
1145 disable unhandled interrupt sources.
1147 no_timer_check [IA-32,X86_64,APIC] Disables the code which tests for
1148 broken timer IRQ sources.
1150 noisapnp [ISAPNP] Disables ISA PnP code.
1152 noinitrd [RAM] Tells the kernel not to load any configured
1153 initial RAM disk.
1155 nointroute [IA-64]
1157 nojitter [IA64] Disables jitter checking for ITC timers.
1159 nolapic [IA-32,APIC] Do not enable or use the local APIC.
1161 nolapic_timer [IA-32,APIC] Do not use the local APIC timer.
1163 noltlbs [PPC] Do not use large page/tlb entries for kernel
1164 lowmem mapping on PPC40x.
1166 nomca [IA-64] Disable machine check abort handling
1168 nomce [IA-32] Machine Check Exception
1170 noreplace-paravirt [IA-32,PV_OPS] Don't patch paravirt_ops
1172 noreplace-smp [IA-32,SMP] Don't replace SMP instructions
1173 with UP alternatives
1175 noresidual [PPC] Don't use residual data on PReP machines.
1177 noresume [SWSUSP] Disables resume and restores original swap
1178 space.
1180 no-scroll [VGA] Disables scrollback.
1181 This is required for the Braillex ib80-piezo Braille
1182 reader made by F.H. Papenmeier (Germany).
1184 nosbagart [IA-64]
1186 nosep [BUGS=IA-32] Disables x86 SYSENTER/SYSEXIT support.
1188 nosmp [SMP] Tells an SMP kernel to act as a UP kernel.
1190 nosoftlockup [KNL] Disable the soft-lockup detector.
1192 nosync [HW,M68K] Disables sync negotiation for all devices.
1194 notsc [BUGS=IA-32] Disable Time Stamp Counter
1196 nousb [USB] Disable the USB subsystem
1198 nowb [ARM]
1200 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1201 one of ['zone', 'node', 'default'] can be specified
1202 This can be set from sysctl after boot.
1203 See Documentation/sysctl/vm.txt for details.
1205 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1207 opl3= [HW,OSS]
1208 Format: <io>
1210 oprofile.timer= [HW]
1211 Use timer interrupt instead of performance counters
1213 osst= [HW,SCSI] SCSI Tape Driver
1214 Format: <buffer_size>,<write_threshold>
1215 See also Documentation/scsi/st.txt.
1217 panic= [KNL] Kernel behaviour on panic
1218 Format: <timeout>
1220 parkbd.port= [HW] Parallel port number the keyboard adapter is
1221 connected to, default is 0.
1222 Format: <parport#>
1223 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1224 0 for XT, 1 for AT (default is AT).
1225 Format: <mode>
1227 parport= [HW,PPT] Specify parallel ports. 0 disables.
1228 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1229 Use 'auto' to force the driver to use any
1230 IRQ/DMA settings detected (the default is to
1231 ignore detected IRQ/DMA settings because of
1232 possible conflicts). You can specify the base
1233 address, IRQ, and DMA settings; IRQ and DMA
1234 should be numbers, or 'auto' (for using detected
1235 settings on that particular port), or 'nofifo'
1236 (to avoid using a FIFO even if it is detected).
1237 Parallel ports are assigned in the order they
1238 are specified on the command line, starting
1239 with parport0.
1241 parport_init_mode= [HW,PPT]
1242 Configure VIA parallel port to operate in
1243 a specific mode. This is necessary on Pegasos
1244 computer where firmware has no options for setting
1245 up parallel port mode and sets it to spp.
1246 Currently this function knows 686a and 8231 chips.
1247 Format: [spp|ps2|epp|ecp|ecpepp]
1249 pas2= [HW,OSS] Format:
1250 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1252 pas16= [HW,SCSI]
1253 See header of drivers/scsi/pas16.c.
1255 pause_on_oops=
1256 Halt all CPUs after the first oops has been printed for
1257 the specified number of seconds. This is to be used if
1258 your oopses keep scrolling off the screen.
1260 pcbit= [HW,ISDN]
1262 pcd. [PARIDE]
1263 See header of drivers/block/paride/pcd.c.
1264 See also Documentation/paride.txt.
1266 pci=option[,option...] [PCI] various PCI subsystem options:
1267 off [IA-32] don't probe for the PCI bus
1268 bios [IA-32] force use of PCI BIOS, don't access
1269 the hardware directly. Use this if your machine
1270 has a non-standard PCI host bridge.
1271 nobios [IA-32] disallow use of PCI BIOS, only direct
1272 hardware access methods are allowed. Use this
1273 if you experience crashes upon bootup and you
1274 suspect they are caused by the BIOS.
1275 conf1 [IA-32] Force use of PCI Configuration
1276 Mechanism 1.
1277 conf2 [IA-32] Force use of PCI Configuration
1278 Mechanism 2.
1279 nommconf [IA-32,X86_64] Disable use of MMCONFIG for PCI
1280 Configuration
1281 nomsi [MSI] If the PCI_MSI kernel config parameter is
1282 enabled, this kernel boot option can be used to
1283 disable the use of MSI interrupts system-wide.
1284 nosort [IA-32] Don't sort PCI devices according to
1285 order given by the PCI BIOS. This sorting is
1286 done to get a device order compatible with
1287 older kernels.
1288 biosirq [IA-32] Use PCI BIOS calls to get the interrupt
1289 routing table. These calls are known to be buggy
1290 on several machines and they hang the machine
1291 when used, but on other computers it's the only
1292 way to get the interrupt routing table. Try
1293 this option if the kernel is unable to allocate
1294 IRQs or discover secondary PCI buses on your
1295 motherboard.
1296 rom [IA-32] Assign address space to expansion ROMs.
1297 Use with caution as certain devices share
1298 address decoders between ROMs and other
1299 resources.
1300 irqmask=0xMMMM [IA-32] Set a bit mask of IRQs allowed to be
1301 assigned automatically to PCI devices. You can
1302 make the kernel exclude IRQs of your ISA cards
1303 this way.
1304 pirqaddr=0xAAAAA [IA-32] Specify the physical address
1305 of the PIRQ table (normally generated
1306 by the BIOS) if it is outside the
1307 F0000h-100000h range.
1308 lastbus=N [IA-32] Scan all buses thru bus #N. Can be
1309 useful if the kernel is unable to find your
1310 secondary buses and you want to tell it
1311 explicitly which ones they are.
1312 assign-busses [IA-32] Always assign all PCI bus
1313 numbers ourselves, overriding
1314 whatever the firmware may have done.
1315 usepirqmask [IA-32] Honor the possible IRQ mask stored
1316 in the BIOS $PIR table. This is needed on
1317 some systems with broken BIOSes, notably
1318 some HP Pavilion N5400 and Omnibook XE3
1319 notebooks. This will have no effect if ACPI
1320 IRQ routing is enabled.
1321 noacpi [IA-32] Do not use ACPI for IRQ routing
1322 or for PCI scanning.
1323 routeirq Do IRQ routing for all PCI devices.
1324 This is normally done in pci_enable_device(),
1325 so this option is a temporary workaround
1326 for broken drivers that don't call it.
1327 firmware [ARM] Do not re-enumerate the bus but instead
1328 just use the configuration from the
1329 bootloader. This is currently used on
1330 IXP2000 systems where the bus has to be
1331 configured a certain way for adjunct CPUs.
1332 noearly [X86] Don't do any early type 1 scanning.
1333 This might help on some broken boards which
1334 machine check when some devices' config space
1335 is read. But various workarounds are disabled
1336 and some IOMMU drivers will not work.
1337 bfsort Sort PCI devices into breadth-first order.
1338 This sorting is done to get a device
1339 order compatible with older (<= 2.4) kernels.
1340 nobfsort Don't sort PCI devices into breadth-first order.
1341 cbiosize=nn[KMG] The fixed amount of bus space which is
1342 reserved for the CardBus bridge's IO window.
1343 The default value is 256 bytes.
1344 cbmemsize=nn[KMG] The fixed amount of bus space which is
1345 reserved for the CardBus bridge's memory
1346 window. The default value is 64 megabytes.
1348 pcmv= [HW,PCMCIA] BadgePAD 4
1350 pd. [PARIDE]
1351 See Documentation/paride.txt.
1353 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1354 boot time.
1355 Format: { 0 | 1 }
1356 See arch/parisc/kernel/pdc_chassis.c
1358 pf. [PARIDE]
1359 See Documentation/paride.txt.
1361 pg. [PARIDE]
1362 See Documentation/paride.txt.
1364 pirq= [SMP,APIC] Manual mp-table setup
1365 See Documentation/i386/IO-APIC.txt.
1367 plip= [PPT,NET] Parallel port network link
1368 Format: { parport<nr> | timid | 0 }
1369 See also Documentation/parport.txt.
1371 pnpacpi= [ACPI]
1372 { off }
1374 pnpbios= [ISAPNP]
1375 { on | off | curr | res | no-curr | no-res }
1377 pnp_reserve_irq=
1378 [ISAPNP] Exclude IRQs for the autoconfiguration
1380 pnp_reserve_dma=
1381 [ISAPNP] Exclude DMAs for the autoconfiguration
1383 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1384 Ranges are in pairs (I/O port base and size).
1386 pnp_reserve_mem=
1387 [ISAPNP] Exclude memory regions for the
1388 autoconfiguration.
1389 Ranges are in pairs (memory base and size).
1391 print-fatal-signals=
1392 [KNL] debug: print fatal signals
1393 print-fatal-signals=1: print segfault info to
1394 the kernel console.
1395 default: off.
1397 printk.time= Show timing data prefixed to each printk message line
1398 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1400 profile= [KNL] Enable kernel profiling via /proc/profile
1401 Format: [schedule,]<number>
1402 Param: "schedule" - profile schedule points.
1403 Param: <number> - step/bucket size as a power of 2 for
1404 statistical time based profiling.
1405 Param: "sleep" - profile D-state sleeping (millisecs)
1407 processor.max_cstate= [HW,ACPI]
1408 Limit processor to maximum C-state
1409 max_cstate=9 overrides any DMI blacklist limit.
1411 processor.nocst [HW,ACPI]
1412 Ignore the _CST method to determine C-states,
1413 instead using the legacy FADT method
1415 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1416 before loading.
1417 See Documentation/ramdisk.txt.
1419 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1420 probe for; one of (bare|imps|exps|lifebook|any).
1421 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1422 per second.
1423 psmouse.resetafter= [HW,MOUSE]
1424 Try to reset the device after so many bad packets
1425 (0 = never).
1426 psmouse.resolution=
1427 [HW,MOUSE] Set desired mouse resolution, in dpi.
1428 psmouse.smartscroll=
1429 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1430 0 = disabled, 1 = enabled (default).
1432 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1433 Format:
1434 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1436 pt. [PARIDE]
1437 See Documentation/paride.txt.
1439 quiet [KNL] Disable most log messages
1441 r128= [HW,DRM]
1443 raid= [HW,RAID]
1444 See Documentation/md.txt.
1446 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1447 See Documentation/ramdisk.txt.
1449 ramdisk_blocksize= [RAM]
1450 See Documentation/ramdisk.txt.
1452 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1453 New name for the ramdisk parameter.
1454 See Documentation/ramdisk.txt.
1456 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1457 RCU callbacks to process in one batch.
1459 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1460 RCU callbacks over which batch limiting is disabled.
1462 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1463 RCU callbacks below which batch limiting is re-enabled.
1465 rdinit= [KNL]
1466 Format: <full_path>
1467 Run specified binary instead of /init from the ramdisk,
1468 used for early userspace startup. See initrd.
1470 reboot= [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1471 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1472 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1474 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1476 reservetop= [IA-32]
1477 Format: nn[KMG]
1478 Reserves a hole at the top of the kernel virtual
1479 address space.
1481 reset_devices [KNL] Force drivers to reset the underlying device
1482 during initialization.
1484 resume= [SWSUSP]
1485 Specify the partition device for software suspend
1487 resume_offset= [SWSUSP]
1488 Specify the offset from the beginning of the partition
1489 given by "resume=" at which the swap header is located,
1490 in <PAGE_SIZE> units (needed only for swap files).
1491 See Documentation/power/swsusp-and-swap-files.txt
1493 retain_initrd [RAM] Keep initrd memory after extraction
1495 rhash_entries= [KNL,NET]
1496 Set number of hash buckets for route cache
1498 riscom8= [HW,SERIAL]
1499 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1501 ro [KNL] Mount root device read-only on boot
1503 root= [KNL] Root filesystem
1505 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1506 mount the root filesystem
1508 rootflags= [KNL] Set root filesystem mount option string
1510 rootfstype= [KNL] Set root filesystem type
1512 rootwait [KNL] Wait (indefinitely) for root device to show up.
1513 Useful for devices that are detected asynchronously
1514 (e.g. USB and MMC devices).
1516 rw [KNL] Mount root device read-write on boot
1518 S [KNL] Run init in single mode
1520 sa1100ir [NET]
1521 See drivers/net/irda/sa1100_ir.c.
1523 sb= [HW,OSS]
1524 Format: <io>,<irq>,<dma>,<dma2>
1526 sbni= [NET] Granch SBNI12 leased line adapter
1528 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1529 Format: <io>[,<timeout>[,<isapnp>]]
1531 scsi_debug_*= [SCSI]
1532 See drivers/scsi/scsi_debug.c.
1534 scsi_default_dev_flags=
1535 [SCSI] SCSI default device flags
1536 Format: <integer>
1538 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1539 Format: <vendor>:<model>:<flags>
1540 (flags are integer value)
1542 scsi_logging= [SCSI]
1544 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1545 discovered. async scans them in kernel threads,
1546 allowing boot to proceed. none ignores them, expecting
1547 user space to do the scan.
1549 selinux [SELINUX] Disable or enable SELinux at boot time.
1550 Format: { "0" | "1" }
1551 See security/selinux/Kconfig help text.
1552 0 -- disable.
1553 1 -- enable.
1554 Default value is set via kernel config option.
1555 If enabled at boot time, /selinux/disable can be used
1556 later to disable prior to initial policy load.
1558 selinux_compat_net =
1559 [SELINUX] Set initial selinux_compat_net flag value.
1560 Format: { "0" | "1" }
1561 0 -- use new secmark-based packet controls
1562 1 -- use legacy packet controls
1563 Default value is 0 (preferred).
1564 Value can be changed at runtime via
1565 /selinux/compat_net.
1567 serialnumber [BUGS=IA-32]
1569 sg_def_reserved_size= [SCSI]
1571 shapers= [NET]
1572 Maximal number of shapers.
1574 sim710= [SCSI,HW]
1575 See header of drivers/scsi/sim710.c.
1577 simeth= [IA-64]
1578 simscsi=
1580 slram= [HW,MTD]
1582 slub_debug[=options[,slabs]] [MM, SLUB]
1583 Enabling slub_debug allows one to determine the
1584 culprit if slab objects become corrupted. Enabling
1585 slub_debug can create guard zones around objects and
1586 may poison objects when not in use. Also tracks the
1587 last alloc / free. For more information see
1588 Documentation/vm/slub.txt.
1590 slub_max_order= [MM, SLUB]
1591 Determines the maximum allowed order for slabs.
1592 A high setting may cause OOMs due to memory
1593 fragmentation. For more information see
1594 Documentation/vm/slub.txt.
1596 slub_min_objects= [MM, SLUB]
1597 The minimum number of objects per slab. SLUB will
1598 increase the slab order up to slub_max_order to
1599 generate a sufficiently large slab able to contain
1600 the number of objects indicated. The higher the number
1601 of objects the smaller the overhead of tracking slabs
1602 and the less frequently locks need to be acquired.
1603 For more information see Documentation/vm/slub.txt.
1605 slub_min_order= [MM, SLUB]
1606 Determines the mininum page order for slabs. Must be
1607 lower than slub_max_order.
1608 For more information see Documentation/vm/slub.txt.
1610 slub_nomerge [MM, SLUB]
1611 Disable merging of slabs with similar size. May be
1612 necessary if there is some reason to distinguish
1613 allocs to different slabs. Debug options disable
1614 merging on their own.
1615 For more information see Documentation/vm/slub.txt.
1617 smart2= [HW]
1618 Format: <io1>[,<io2>[,...,<io8>]]
1620 smp-alt-once [IA-32,SMP] On a hotplug CPU system, only
1621 attempt to substitute SMP alternatives once at boot.
1623 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1624 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1625 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1626 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1627 smsc-ircc2.ircc_irq= [HW] IRQ line
1628 smsc-ircc2.ircc_dma= [HW] DMA channel
1629 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1630 0: Toshiba Satellite 1800 (GP data pin select)
1631 1: Fast pin select (default)
1632 2: ATC IRMode
1634 snd-ad1816a= [HW,ALSA]
1636 snd-ad1848= [HW,ALSA]
1638 snd-ali5451= [HW,ALSA]
1640 snd-als100= [HW,ALSA]
1642 snd-als4000= [HW,ALSA]
1644 snd-azt2320= [HW,ALSA]
1646 snd-cmi8330= [HW,ALSA]
1648 snd-cmipci= [HW,ALSA]
1650 snd-cs4231= [HW,ALSA]
1652 snd-cs4232= [HW,ALSA]
1654 snd-cs4236= [HW,ALSA]
1656 snd-cs4281= [HW,ALSA]
1658 snd-cs46xx= [HW,ALSA]
1660 snd-dt019x= [HW,ALSA]
1662 snd-dummy= [HW,ALSA]
1664 snd-emu10k1= [HW,ALSA]
1666 snd-ens1370= [HW,ALSA]
1668 snd-ens1371= [HW,ALSA]
1670 snd-es968= [HW,ALSA]
1672 snd-es1688= [HW,ALSA]
1674 snd-es18xx= [HW,ALSA]
1676 snd-es1938= [HW,ALSA]
1678 snd-es1968= [HW,ALSA]
1680 snd-fm801= [HW,ALSA]
1682 snd-gusclassic= [HW,ALSA]
1684 snd-gusextreme= [HW,ALSA]
1686 snd-gusmax= [HW,ALSA]
1688 snd-hdsp= [HW,ALSA]
1690 snd-ice1712= [HW,ALSA]
1692 snd-intel8x0= [HW,ALSA]
1694 snd-interwave= [HW,ALSA]
1696 snd-interwave-stb=
1697 [HW,ALSA]
1699 snd-korg1212= [HW,ALSA]
1701 snd-maestro3= [HW,ALSA]
1703 snd-mpu401= [HW,ALSA]
1705 snd-mtpav= [HW,ALSA]
1707 snd-nm256= [HW,ALSA]
1709 snd-opl3sa2= [HW,ALSA]
1711 snd-opti92x-ad1848=
1712 [HW,ALSA]
1714 snd-opti92x-cs4231=
1715 [HW,ALSA]
1717 snd-opti93x= [HW,ALSA]
1719 snd-pmac= [HW,ALSA]
1721 snd-rme32= [HW,ALSA]
1723 snd-rme96= [HW,ALSA]
1725 snd-rme9652= [HW,ALSA]
1727 snd-sb8= [HW,ALSA]
1729 snd-sb16= [HW,ALSA]
1731 snd-sbawe= [HW,ALSA]
1733 snd-serial= [HW,ALSA]
1735 snd-sgalaxy= [HW,ALSA]
1737 snd-sonicvibes= [HW,ALSA]
1739 snd-sun-amd7930=
1740 [HW,ALSA]
1742 snd-sun-cs4231= [HW,ALSA]
1744 snd-trident= [HW,ALSA]
1746 snd-usb-audio= [HW,ALSA,USB]
1748 snd-via82xx= [HW,ALSA]
1750 snd-virmidi= [HW,ALSA]
1752 snd-wavefront= [HW,ALSA]
1754 snd-ymfpci= [HW,ALSA]
1756 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1757 See Documentation/sonypi.txt
1759 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1760 See Documentation/specialix.txt.
1762 spia_io_base= [HW,MTD]
1763 spia_fio_base=
1764 spia_pedr=
1765 spia_peddr=
1767 sscape= [HW,OSS]
1768 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1770 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1771 See Documentation/scsi/st.txt.
1773 st0x= [HW,SCSI]
1774 See header of drivers/scsi/seagate.c.
1776 sti= [PARISC,HW]
1777 Format: <num>
1778 Set the STI (builtin display/keyboard on the HP-PARISC
1779 machines) console (graphic card) which should be used
1780 as the initial boot-console.
1781 See also comment in drivers/video/console/sticore.c.
1783 sti_font= [HW]
1784 See comment in drivers/video/console/sticore.c.
1786 stifb= [HW]
1787 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1789 sunrpc.pool_mode=
1790 [NFS]
1791 Control how the NFS server code allocates CPUs to
1792 service thread pools. Depending on how many NICs
1793 you have and where their interrupts are bound, this
1794 option will affect which CPUs will do NFS serving.
1795 Note: this parameter cannot be changed while the
1796 NFS server is running.
1798 auto the server chooses an appropriate mode
1799 automatically using heuristics
1800 global a single global pool contains all CPUs
1801 percpu one pool for each CPU
1802 pernode one pool for each NUMA node (equivalent
1803 to global on non-NUMA machines)
1805 swiotlb= [IA-64] Number of I/O TLB slabs
1807 switches= [HW,M68k]
1809 sym53c416= [HW,SCSI]
1810 See header of drivers/scsi/sym53c416.c.
1812 sysrq_always_enabled
1813 [KNL]
1814 Ignore sysrq setting - this boot parameter will
1815 neutralize any effect of /proc/sys/kernel/sysrq.
1816 Useful for debugging.
1818 t128= [HW,SCSI]
1819 See header of drivers/scsi/t128.c.
1821 tdfx= [HW,DRM]
1823 thash_entries= [KNL,NET]
1824 Set number of hash buckets for TCP connection
1826 time Show timing data prefixed to each printk message line
1827 [deprecated, see 'printk.time']
1829 tipar.timeout= [HW,PPT]
1830 Set communications timeout in tenths of a second
1831 (default 15).
1833 tipar.delay= [HW,PPT]
1834 Set inter-bit delay in microseconds (default 10).
1836 tmc8xx= [HW,SCSI]
1837 See header of drivers/scsi/seagate.c.
1839 tmscsim= [HW,SCSI]
1840 See comment before function dc390_setup() in
1841 drivers/scsi/tmscsim.c.
1843 tp720= [HW,PS2]
1845 trix= [HW,OSS] MediaTrix AudioTrix Pro
1846 Format:
1847 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1849 tsdev.xres= [TS] Horizontal screen resolution.
1850 tsdev.yres= [TS] Vertical screen resolution.
1852 turbografx.map[2|3]= [HW,JOY]
1853 TurboGraFX parallel port interface
1854 Format:
1855 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1856 See also Documentation/input/joystick-parport.txt
1858 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1859 See header of drivers/scsi/u14-34f.c.
1861 uart401= [HW,OSS]
1862 Format: <io>,<irq>
1864 uart6850= [HW,OSS]
1865 Format: <io>,<irq>
1867 uhci-hcd.ignore_oc=
1868 [USB] Ignore overcurrent events (default N).
1869 Some badly-designed motherboards generate lots of
1870 bogus events, for ports that aren't wired to
1871 anything. Set this parameter to avoid log spamming.
1872 Note that genuine overcurrent events won't be
1873 reported either.
1875 usbcore.autosuspend=
1876 [USB] The autosuspend time delay (in seconds) used
1877 for newly-detected USB devices (default 2). This
1878 is the time required before an idle device will be
1879 autosuspended. Devices for which the delay is set
1880 to a negative value won't be autosuspended at all.
1882 usbhid.mousepoll=
1883 [USBHID] The interval which mice are to be polled at.
1885 vdso= [IA-32,SH,x86-64]
1886 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1887 vdso=1: enable VDSO (default)
1888 vdso=0: disable VDSO mapping
1890 vector= [IA-64,SMP]
1891 vector=percpu: enable percpu vector domain
1893 video= [FB] Frame buffer configuration
1894 See Documentation/fb/modedb.txt.
1896 vga= [BOOT,IA-32] Select a particular video mode
1897 See Documentation/i386/boot.txt and
1898 Documentation/svga.txt.
1899 Use vga=ask for menu.
1900 This is actually a boot loader parameter; the value is
1901 passed to the kernel using a special protocol.
1903 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1904 size of <nn>. This can be used to increase the
1905 minimum size (128MB on x86). It can also be used to
1906 decrease the size and leave more room for directly
1907 mapped kernel RAM.
1909 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1910 Format: <command>
1912 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1913 Format: <command>
1915 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1916 Format: <command>
1918 waveartist= [HW,OSS]
1919 Format: <io>,<irq>,<dma>,<dma2>
1921 wd33c93= [HW,SCSI]
1922 See header of drivers/scsi/wd33c93.c.
1924 wd7000= [HW,SCSI]
1925 See header of drivers/scsi/wd7000.c.
1927 wdt= [WDT] Watchdog
1928 See Documentation/watchdog/watchdog.txt.
1930 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1931 xd_geo= See header of drivers/block/xd.c.
1933 xirc2ps_cs= [NET,PCMCIA]
1934 Format:
1935 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1937 norandmaps Don't use address space randomization
1938 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1940 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1941 This is useful to get more information why
1942 you got a "dwarf2 unwinder stuck"
1944 ______________________________________________________________________
1946 TODO:
1948 Add documentation for ALSA options.
1949 Add more DRM drivers.