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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 ALSA ALSA sound support is enabled.
34 APIC APIC support is enabled.
35 APM Advanced Power Management support is enabled.
36 AX25 Appropriate AX.25 support is enabled.
37 CD Appropriate CD support is enabled.
38 DRM Direct Rendering Management support is enabled.
39 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
40 EFI EFI Partitioning (GPT) is enabled
41 EIDE EIDE/ATAPI support is enabled.
42 FB The frame buffer device is enabled.
43 HW Appropriate hardware is enabled.
44 IA-32 IA-32 aka i386 architecture is enabled.
45 IA-64 IA-64 architecture is enabled.
46 IOSCHED More than one I/O scheduler is enabled.
47 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
48 ISAPNP ISA PnP code is enabled.
49 ISDN Appropriate ISDN support is enabled.
50 JOY Appropriate joystick support is enabled.
51 LIBATA Libata driver is enabled
52 LP Printer support is enabled.
53 LOOP Loopback device support is enabled.
54 M68k M68k architecture is enabled.
55 These options have more detailed description inside of
56 Documentation/m68k/kernel-options.txt.
57 MCA MCA bus support is enabled.
58 MDA MDA console support is enabled.
59 MOUSE Appropriate mouse support is enabled.
60 MSI Message Signaled Interrupts (PCI).
61 MTD MTD support is enabled.
62 NET Appropriate network support is enabled.
63 NUMA NUMA support is enabled.
64 GENERIC_TIME The generic timeofday code is enabled.
65 NFS Appropriate NFS support is enabled.
66 OSS OSS sound support is enabled.
67 PV_OPS A paravirtualized kernel
68 PARIDE The ParIDE subsystem is enabled.
69 PARISC The PA-RISC architecture is enabled.
70 PCI PCI bus support is enabled.
71 PCMCIA The PCMCIA subsystem is enabled.
72 PNP Plug & Play support is enabled.
73 PPC PowerPC architecture is enabled.
74 PPT Parallel port support is enabled.
75 PS2 Appropriate PS/2 support is enabled.
76 RAM RAM disk support is enabled.
77 S390 S390 architecture is enabled.
78 SCSI Appropriate SCSI support is enabled.
79 A lot of drivers has their options described inside of
80 Documentation/scsi/.
81 SELINUX SELinux support is enabled.
82 SERIAL Serial support is enabled.
83 SH SuperH architecture is enabled.
84 SMP The kernel is an SMP kernel.
85 SPARC Sparc architecture is enabled.
86 SWSUSP Software suspend is enabled.
87 TS Appropriate touchscreen support is enabled.
88 USB USB support is enabled.
89 USBHID USB Human Interface Device support is enabled.
90 V4L Video For Linux support is enabled.
91 VGA The VGA console has been enabled.
92 VT Virtual terminal support is enabled.
93 WDT Watchdog support is enabled.
94 XT IBM PC/XT MFM hard disk support is enabled.
95 X86-64 X86-64 architecture is enabled.
96 More X86-64 boot options can be found in
97 Documentation/x86_64/boot-options.txt .
99 In addition, the following text indicates that the option:
101 BUGS= Relates to possible processor bugs on the said processor.
102 KNL Is a kernel start-up parameter.
103 BOOT Is a boot loader parameter.
105 Parameters denoted with BOOT are actually interpreted by the boot
106 loader, and have no meaning to the kernel directly.
107 Do not modify the syntax of boot loader parameters without extreme
108 need or coordination with <Documentation/i386/boot.txt>.
110 There are also arch-specific kernel-parameters not documented here.
111 See for example <Documentation/x86_64/boot-options.txt>.
113 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
114 a trailing = on the name of any parameter states that that parameter will
115 be entered as an environment variable, whereas its absence indicates that
116 it will appear as a kernel argument readable via /proc/cmdline by programs
117 running once the system is up.
119 The number of kernel parameters is not limited, but the length of the
120 complete command line (parameters including spaces etc.) is limited to
121 a fixed number of characters. This limit depends on the architecture
122 and is between 256 and 4096 characters. It is defined in the file
123 ./include/asm/setup.h as COMMAND_LINE_SIZE.
126 53c7xx= [HW,SCSI] Amiga SCSI controllers
127 See header of drivers/scsi/53c7xx.c.
128 See also Documentation/scsi/ncr53c7xx.txt.
130 acpi= [HW,ACPI,X86-64,i386]
131 Advanced Configuration and Power Interface
132 Format: { force | off | ht | strict | noirq }
133 force -- enable ACPI if default was off
134 off -- disable ACPI if default was on
135 noirq -- do not use ACPI for IRQ routing
136 ht -- run only enough ACPI to enable Hyper Threading
137 strict -- Be less tolerant of platforms that are not
138 strictly ACPI specification compliant.
140 See also Documentation/pm.txt, pci=noacpi
142 acpi_apic_instance= [ACPI, IOAPIC]
143 Format: <int>
144 2: use 2nd APIC table, if available
145 1,0: use 1st APIC table
146 default: 0
148 acpi_sleep= [HW,ACPI] Sleep options
149 Format: { s3_bios, s3_mode }
150 See Documentation/power/video.txt
152 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
153 Format: { level | edge | high | low }
155 acpi_irq_balance [HW,ACPI]
156 ACPI will balance active IRQs
157 default in APIC mode
159 acpi_irq_nobalance [HW,ACPI]
160 ACPI will not move active IRQs (default)
161 default in PIC mode
163 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
164 use by PCI
165 Format: <irq>,<irq>...
167 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
168 Format: <irq>,<irq>...
170 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
171 Format: To spoof as Windows 98: ="Microsoft Windows"
173 acpi_osi= [HW,ACPI] empty param disables _OSI
175 acpi_serialize [HW,ACPI] force serialization of AML methods
177 acpi_skip_timer_override [HW,ACPI]
178 Recognize and ignore IRQ0/pin2 Interrupt Override.
179 For broken nForce2 BIOS resulting in XT-PIC timer.
180 acpi_use_timer_override [HW,ACPI}
181 Use timer override. For some broken Nvidia NF5 boards
182 that require a timer override, but don't have
183 HPET
185 acpi.debug_layer= [HW,ACPI]
186 Format: <int>
187 Each bit of the <int> indicates an ACPI debug layer,
188 1: enable, 0: disable. It is useful for boot time
189 debugging. After system has booted up, it can be set
190 via /sys/module/acpi/parameters/debug_layer.
191 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
192 Available bits (add the numbers together) to enable debug output
193 for specific parts of the ACPI subsystem:
194 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
195 0x10 namespace 0x20 parser 0x40 dispatcher
196 0x80 executer 0x100 resources 0x200 acpica debugger
197 0x400 os services 0x800 acpica disassembler.
198 The number can be in decimal or prefixed with 0x in hex.
199 Warning: Many of these options can produce a lot of
200 output and make your system unusable. Be very careful.
202 acpi.debug_level= [HW,ACPI]
203 Format: <int>
204 Each bit of the <int> indicates an ACPI debug level,
205 1: enable, 0: disable. It is useful for boot time
206 debugging. After system has booted up, it can be set
207 via /sys/module/acpi/parameters/debug_level.
208 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
209 Available bits (add the numbers together) to enable different
210 debug output levels of the ACPI subsystem:
211 0x01 error 0x02 warn 0x04 init 0x08 debug object
212 0x10 info 0x20 init names 0x40 parse 0x80 load
213 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
214 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
215 0x10000 resources 0x20000 user requests 0x40000 package.
216 The number can be in decimal or prefixed with 0x in hex.
217 Warning: Many of these options can produce a lot of
218 output and make your system unusable. Be very careful.
221 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
223 acpi_generic_hotkey [HW,ACPI]
224 Allow consolidated generic hotkey driver to
225 override platform specific driver.
226 See also Documentation/acpi-hotkey.txt.
228 acpi_pm_good [IA-32,X86-64]
229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
233 enable_timer_pin_1 [i386,x86-64]
234 Enable PIN 1 of APIC timer
235 Can be useful to work around chipset bugs
236 (in particular on some ATI chipsets).
237 The kernel tries to set a reasonable default.
239 disable_timer_pin_1 [i386,x86-64]
240 Disable PIN 1 of APIC timer
241 Can be useful to work around chipset bugs.
243 ad1816= [HW,OSS]
244 Format: <io>,<irq>,<dma>,<dma2>
245 See also Documentation/sound/oss/AD1816.
247 ad1848= [HW,OSS]
248 Format: <io>,<irq>,<dma>,<dma2>,<type>
250 adlib= [HW,OSS]
251 Format: <io>
253 advansys= [HW,SCSI]
254 See header of drivers/scsi/advansys.c.
256 advwdt= [HW,WDT] Advantech WDT
257 Format: <iostart>,<iostop>
259 aedsp16= [HW,OSS] Audio Excel DSP 16
260 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
261 See also header of sound/oss/aedsp16.c.
263 aha152x= [HW,SCSI]
264 See Documentation/scsi/aha152x.txt.
266 aha1542= [HW,SCSI]
267 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
269 aic7xxx= [HW,SCSI]
270 See Documentation/scsi/aic7xxx.txt.
272 aic79xx= [HW,SCSI]
273 See Documentation/scsi/aic79xx.txt.
275 amijoy.map= [HW,JOY] Amiga joystick support
276 Map of devices attached to JOY0DAT and JOY1DAT
277 Format: <a>,<b>
278 See also Documentation/kernel/input/joystick.txt
280 analog.map= [HW,JOY] Analog joystick and gamepad support
281 Specifies type or capabilities of an analog joystick
282 connected to one of 16 gameports
283 Format: <type1>,<type2>,..<type16>
285 apc= [HW,SPARC]
286 Power management functions (SPARCstation-4/5 + deriv.)
287 Format: noidle
288 Disable APC CPU standby support. SPARCstation-Fox does
289 not play well with APC CPU idle - disable it if you have
290 APC and your system crashes randomly.
292 apic= [APIC,i386] Change the output verbosity whilst booting
293 Format: { quiet (default) | verbose | debug }
294 Change the amount of debugging information output
295 when initialising the APIC and IO-APIC components.
297 apm= [APM] Advanced Power Management
298 See header of arch/i386/kernel/apm.c.
300 applicom= [HW]
301 Format: <mem>,<irq>
303 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
304 Format: <io>,<irq>,<nodeID>
306 ataflop= [HW,M68k]
308 atarimouse= [HW,MOUSE] Atari Mouse
310 atascsi= [HW,SCSI] Atari SCSI
312 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
313 EzKey and similar keyboards
315 atkbd.reset= [HW] Reset keyboard during initialization
317 atkbd.set= [HW] Select keyboard code set
318 Format: <int> (2 = AT (default), 3 = PS/2)
320 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
321 keyboards
323 atkbd.softraw= [HW] Choose between synthetic and real raw mode
324 Format: <bool> (0 = real, 1 = synthetic (default))
326 atkbd.softrepeat= [HW]
327 Use software keyboard repeat
329 autotest [IA64]
331 aztcd= [HW,CD] Aztech CD268 CDROM driver
332 Format: <io>,0x79 (?)
334 baycom_epp= [HW,AX25]
335 Format: <io>,<mode>
337 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
338 Format: <io>,<mode>
339 See header of drivers/net/hamradio/baycom_par.c.
341 baycom_ser_fdx= [HW,AX25]
342 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
343 Format: <io>,<irq>,<mode>[,<baud>]
344 See header of drivers/net/hamradio/baycom_ser_fdx.c.
346 baycom_ser_hdx= [HW,AX25]
347 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
348 Format: <io>,<irq>,<mode>
349 See header of drivers/net/hamradio/baycom_ser_hdx.c.
351 blkmtd_device= [HW,MTD]
352 blkmtd_erasesz=
353 blkmtd_ro=
354 blkmtd_bs=
355 blkmtd_count=
357 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
358 bttv.radio= Most important insmod options are available as
359 kernel args too.
360 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
361 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
363 BusLogic= [HW,SCSI]
364 See drivers/scsi/BusLogic.c, comment before function
365 BusLogic_ParseDriverOptions().
367 c101= [NET] Moxa C101 synchronous serial card
369 cachesize= [BUGS=IA-32] Override level 2 CPU cache size detection.
370 Sometimes CPU hardware bugs make them report the cache
371 size incorrectly. The kernel will attempt work arounds
372 to fix known problems, but for some CPUs it is not
373 possible to determine what the correct size should be.
374 This option provides an override for these situations.
376 cdu31a= [HW,CD]
377 Format: <io>,<irq>[,PAS]
378 See header of drivers/cdrom/cdu31a.c.
380 chandev= [HW,NET] Generic channel device initialisation
382 checkreqprot [SELINUX] Set initial checkreqprot flag value.
383 Format: { "0" | "1" }
384 See security/selinux/Kconfig help text.
385 0 -- check protection applied by kernel (includes
386 any implied execute protection).
387 1 -- check protection requested by application.
388 Default value is set via a kernel config option.
389 Value can be changed at runtime via
390 /selinux/checkreqprot.
392 clock= [BUGS=IA-32, HW] gettimeofday clocksource override.
393 [Deprecated]
394 Forces specified clocksource (if available) to be used
395 when calculating gettimeofday(). If specified
396 clocksource is not available, it defaults to PIT.
397 Format: { pit | tsc | cyclone | pmtmr }
399 code_bytes [IA32] How many bytes of object code to print in an
400 oops report.
401 Range: 0 - 8192
402 Default: 64
404 disable_8254_timer
405 enable_8254_timer
406 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
407 over the 8254 in addition to over the IO-APIC. The
408 kernel tries to set a sensible default.
410 hpet= [IA-32,HPET] option to disable HPET and use PIT.
411 Format: disable
413 cm206= [HW,CD]
414 Format: { auto | [<io>,][<irq>] }
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,io,<addr>[,options]
448 uart,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 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
455 Format:
456 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
458 cpia_pp= [HW,PPT]
459 Format: { parport<nr> | auto | none }
461 crashkernel=nn[KMG]@ss[KMG]
462 [KNL] Reserve a chunk of physical memory to
463 hold a kernel to switch to with kexec on panic.
465 cs4232= [HW,OSS]
466 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
468 cs89x0_dma= [HW,NET]
469 Format: <dma>
471 cs89x0_media= [HW,NET]
472 Format: { rj45 | aui | bnc }
474 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
476 dasd= [HW,NET]
477 See header of drivers/s390/block/dasd_devmap.c.
479 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
480 (one device per port)
481 Format: <port#>,<type>
482 See also Documentation/input/joystick-parport.txt
484 debug [KNL] Enable kernel debugging (events log level).
486 debug_locks_verbose=
487 [KNL] verbose self-tests
488 Format=<0|1>
489 Print debugging info while doing the locking API
490 self-tests.
491 We default to 0 (no extra messages), setting it to
492 1 will print _a lot_ more information - normally
493 only useful to kernel developers.
495 decnet= [HW,NET]
496 Format: <area>[,<node>]
497 See also Documentation/networking/decnet.txt.
499 default_blu= [VT]
500 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
501 Change the default blue palette of the console.
502 This is a 16-member array composed of values
503 ranging from 0-255.
505 default_grn= [VT]
506 Format: <green0>,<green1>,<green2>,...,<green15>
507 Change the default green palette of the console.
508 This is a 16-member array composed of values
509 ranging from 0-255.
511 default_red= [VT]
512 Format: <red0>,<red1>,<red2>,...,<red15>
513 Change the default red palette of the console.
514 This is a 16-member array composed of values
515 ranging from 0-255.
517 default_utf8= [VT]
518 Format=<0|1>
519 Set system-wide default UTF-8 mode for all tty's.
520 Default is 0 and by setting to 1, it enables UTF-8
521 mode for all newly opened or allocated terminals.
523 dhash_entries= [KNL]
524 Set number of hash buckets for dentry cache.
526 digi= [HW,SERIAL]
527 IO parameters + enable/disable command.
529 digiepca= [HW,SERIAL]
530 See drivers/char/README.epca and
531 Documentation/digiepca.txt.
533 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
534 support available.
535 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
537 dmasound= [HW,OSS] Sound subsystem buffers
539 dscc4.setup= [NET]
541 dtc3181e= [HW,SCSI]
543 earlyprintk= [IA-32,X86-64,SH]
544 earlyprintk=vga
545 earlyprintk=serial[,ttySn[,baudrate]]
547 Append ",keep" to not disable it when the real console
548 takes over.
550 Only vga or serial at a time, not both.
552 Currently only ttyS0 and ttyS1 are supported.
554 Interaction with the standard serial driver is not
555 very good.
557 The VGA output is eventually overwritten by the real
558 console.
560 eata= [HW,SCSI]
562 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
563 Format: <int>
564 0: polling mode
565 non-0: interrupt mode (default)
567 eda= [HW,PS2]
569 edb= [HW,PS2]
571 edd= [EDD]
572 Format: {"of[f]" | "sk[ipmbr]"}
573 See comment in arch/i386/boot/edd.S
575 eicon= [HW,ISDN]
576 Format: <id>,<membase>,<irq>
578 eisa_irq_edge= [PARISC,HW]
579 See header of drivers/parisc/eisa.c.
581 elanfreq= [IA-32]
582 See comment before function elanfreq_setup() in
583 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
585 elevator= [IOSCHED]
586 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
587 See Documentation/block/as-iosched.txt and
588 Documentation/block/deadline-iosched.txt for details.
590 elfcorehdr= [IA-32, X86_64]
591 Specifies physical address of start of kernel core
592 image elf header. Generally kexec loader will
593 pass this option to capture kernel.
594 See Documentation/kdump/kdump.txt for details.
596 enforcing [SELINUX] Set initial enforcing status.
597 Format: {"0" | "1"}
598 See security/selinux/Kconfig help text.
599 0 -- permissive (log only, no denials).
600 1 -- enforcing (deny and log).
601 Default value is 0.
602 Value can be changed at runtime via /selinux/enforce.
604 es1371= [HW,OSS]
605 Format: <spdif>,[<nomix>,[<amplifier>]]
606 See also header of sound/oss/es1371.c.
608 ether= [HW,NET] Ethernet cards parameters
609 This option is obsoleted by the "netdev=" option, which
610 has equivalent usage. See its documentation for details.
612 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
613 Format: <io>[,<irq>]
615 failslab=
616 fail_page_alloc=
617 fail_make_request=[KNL]
618 General fault injection mechanism.
619 Format: <interval>,<probability>,<space>,<times>
620 See also /Documentation/fault-injection/.
622 fd_mcs= [HW,SCSI]
623 See header of drivers/scsi/fd_mcs.c.
625 fdomain= [HW,SCSI]
626 See header of drivers/scsi/fdomain.c.
628 floppy= [HW]
629 See Documentation/floppy.txt.
631 gamecon.map[2|3]=
632 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
633 support via parallel port (up to 5 devices per port)
634 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
635 See also Documentation/input/joystick-parport.txt
637 gamma= [HW,DRM]
639 gdth= [HW,SCSI]
640 See header of drivers/scsi/gdth.c.
642 gpt [EFI] Forces disk with valid GPT signature but
643 invalid Protective MBR to be treated as GPT.
645 gscd= [HW,CD]
646 Format: <io>
648 gvp11= [HW,SCSI]
650 hashdist= [KNL,NUMA] Large hashes allocated during boot
651 are distributed across NUMA nodes. Defaults on
652 for IA-64, off otherwise.
653 Format: 0 | 1 (for off | on)
655 hcl= [IA-64] SGI's Hardware Graph compatibility layer
657 hd= [EIDE] (E)IDE hard drive subsystem geometry
658 Format: <cyl>,<head>,<sect>
660 hd?= [HW] (E)IDE subsystem
661 hd?lun= See Documentation/ide.txt.
663 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
664 size of <nn>. This works even on boxes that have no
665 highmem otherwise. This also works to reduce highmem
666 size on bigger boxes.
668 highres= [KNL] Enable/disable high resolution timer mode.
669 Valid parameters: "on", "off"
670 Default: "on"
672 hisax= [HW,ISDN]
673 See Documentation/isdn/README.HiSax.
675 hugepages= [HW,IA-32,IA-64] Maximal number of HugeTLB pages.
677 i8042.direct [HW] Put keyboard port into non-translated mode
678 i8042.dumbkbd [HW] Pretend that controller can only read data from
679 keyboard and cannot control its state
680 (Don't attempt to blink the leds)
681 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
682 i8042.nokbd [HW] Don't check/create keyboard port
683 i8042.nomux [HW] Don't check presence of an active multiplexing
684 controller
685 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
686 controllers
687 i8042.panicblink=
688 [HW] Frequency with which keyboard LEDs should blink
689 when kernel panics (default is 0.5 sec)
690 i8042.reset [HW] Reset the controller during init and cleanup
691 i8042.unlock [HW] Unlock (ignore) the keylock
693 i810= [HW,DRM]
695 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
696 indicates that the driver is running on unsupported
697 hardware.
698 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
699 does not match list of supported models.
700 i8k.power_status
701 [HW] Report power status in /proc/i8k
702 (disabled by default)
703 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
704 capability is set.
706 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
707 See Documentation/mca.txt.
709 icn= [HW,ISDN]
710 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
712 ide= [HW] (E)IDE subsystem
713 Format: ide=nodma or ide=doubler or ide=reverse
714 See Documentation/ide.txt.
716 ide?= [HW] (E)IDE subsystem
717 Format: ide?=noprobe or chipset specific parameters.
718 See Documentation/ide.txt.
720 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
721 See Documentation/ide.txt.
723 idle= [X86]
724 Format: idle=poll or idle=mwait
725 Poll forces a polling idle loop that can slightly improves the performance
726 of waking up a idle CPU, but will use a lot of power and make the system
727 run hot. Not recommended.
728 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
729 to not use it because it doesn't save as much power as a normal idle
730 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
731 as idle=poll.
733 ignore_loglevel [KNL]
734 Ignore loglevel setting - this will print /all/
735 kernel messages to the console. Useful for debugging.
737 ihash_entries= [KNL]
738 Set number of hash buckets for inode cache.
740 in2000= [HW,SCSI]
741 See header of drivers/scsi/in2000.c.
743 init= [KNL]
744 Format: <full_path>
745 Run specified binary instead of /sbin/init as init
746 process.
748 initcall_debug [KNL] Trace initcalls as they are executed. Useful
749 for working out where the kernel is dying during
750 startup.
752 initrd= [BOOT] Specify the location of the initial ramdisk
754 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
755 Format: <irq>
757 inttest= [IA64]
759 io7= [HW] IO7 for Marvel based alpha systems
760 See comment before marvel_specify_io7 in
761 arch/alpha/kernel/core_marvel.c.
763 ip= [IP_PNP]
764 See Documentation/nfsroot.txt.
766 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
767 See comment before ip2_setup() in drivers/char/ip2.c.
769 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
770 See header of drivers/scsi/ips.c.
772 ports= [IP_VS_FTP] IPVS ftp helper module
773 Default is 21.
774 Up to 8 (IP_VS_APP_MAX_PORTS) ports
775 may be specified.
776 Format: <port>,<port>....
778 irqfixup [HW]
779 When an interrupt is not handled search all handlers
780 for it. Intended to get systems with badly broken
781 firmware running.
783 irqpoll [HW]
784 When an interrupt is not handled search all handlers
785 for it. Also check all handlers each timer
786 interrupt. Intended to get systems with badly broken
787 firmware running.
789 isapnp= [ISAPNP]
790 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
792 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
793 Format:
794 <cpu number>,...,<cpu number>
795 or
796 <cpu number>-<cpu number> (must be a positive range in ascending order)
797 or a mixture
798 <cpu number>,...,<cpu number>-<cpu number>
799 This option can be used to specify one or more CPUs
800 to isolate from the general SMP balancing and scheduling
801 algorithms. The only way to move a process onto or off
802 an "isolated" CPU is via the CPU affinity syscalls.
803 <cpu number> begins at 0 and the maximum value is
804 "number of CPUs in system - 1".
806 This option is the preferred way to isolate CPUs. The
807 alternative -- manually setting the CPU mask of all
808 tasks in the system -- can cause problems and
809 suboptimal load balancer performance.
811 isp16= [HW,CD]
812 Format: <io>,<irq>,<dma>,<setup>
814 iucv= [HW,NET]
816 js= [HW,JOY] Analog joystick
817 See Documentation/input/joystick.txt.
819 keepinitrd [HW,ARM]
821 kstack=N [IA-32,X86-64] Print N words from the kernel stack
822 in oops dumps.
824 l2cr= [PPC]
826 lapic [IA-32,APIC] Enable the local APIC even if BIOS
827 disabled it.
829 lapic_timer_c2_ok [IA-32,x86-64,APIC] trust the local apic timer in
830 C2 power state.
832 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
833 Format: addr:<io>,irq:<irq>
835 legacy_serial.force [HW,IA-32,X86-64]
836 Probe for COM ports at legacy addresses even
837 if PNPBIOS or ACPI should describe them. This
838 is for working around firmware defects.
840 llsc*= [IA64] See function print_params() in
841 arch/ia64/sn/kernel/llsc4.c.
843 load_ramdisk= [RAM] List of ramdisks to load from floppy
844 See Documentation/ramdisk.txt.
846 lockd.nlm_grace_period=P [NFS] Assign grace period.
847 Format: <integer>
849 lockd.nlm_tcpport=N [NFS] Assign TCP port.
850 Format: <integer>
852 lockd.nlm_timeout=T [NFS] Assign timeout value.
853 Format: <integer>
855 lockd.nlm_udpport=M [NFS] Assign UDP port.
856 Format: <integer>
858 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
859 Format: <irq>
861 loglevel= All Kernel Messages with a loglevel smaller than the
862 console loglevel will be printed to the console. It can
863 also be changed with klogd or other programs. The
864 loglevels are defined as follows:
866 0 (KERN_EMERG) system is unusable
867 1 (KERN_ALERT) action must be taken immediately
868 2 (KERN_CRIT) critical conditions
869 3 (KERN_ERR) error conditions
870 4 (KERN_WARNING) warning conditions
871 5 (KERN_NOTICE) normal but significant condition
872 6 (KERN_INFO) informational
873 7 (KERN_DEBUG) debug-level messages
875 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
876 Format: { n | nk | nM }
877 n must be a power of two. The default size
878 is set in the kernel config file.
880 lp=0 [LP] Specify parallel ports to use, e.g,
881 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
882 lp=reset first parallel port). 'lp=0' disables the
883 lp=auto printer driver. 'lp=reset' (which can be
884 specified in addition to the ports) causes
885 attached printers to be reset. Using
886 lp=port1,port2,... specifies the parallel ports
887 to associate lp devices with, starting with
888 lp0. A port specification may be 'none' to skip
889 that lp device, or a parport name such as
890 'parport0'. Specifying 'lp=auto' instead of a
891 port specification list means that device IDs
892 from each port should be examined, to see if
893 an IEEE 1284-compliant printer is attached; if
894 so, the driver will manage that printer.
895 See also header of drivers/char/lp.c.
897 lpj=n [KNL]
898 Sets loops_per_jiffy to given constant, thus avoiding
899 time-consuming boot-time autodetection (up to 250 ms per
900 CPU). 0 enables autodetection (default). To determine
901 the correct value for your kernel, boot with normal
902 autodetection and see what value is printed. Note that
903 on SMP systems the preset will be applied to all CPUs,
904 which is likely to cause problems if your CPUs need
905 significantly divergent settings. An incorrect value
906 will cause delays in the kernel to be wrong, leading to
907 unpredictable I/O errors and other breakage. Although
908 unlikely, in the extreme case this might damage your
909 hardware.
911 ltpc= [NET]
912 Format: <io>,<irq>,<dma>
914 mac5380= [HW,SCSI] Format:
915 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
917 mac53c9x= [HW,SCSI] Format:
918 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
920 machvec= [IA64] Force the use of a particular machine-vector
921 (machvec) in a generic kernel.
922 Example: machvec=hpzx1_swiotlb
924 max_loop= [LOOP] Maximum number of loopback devices that can
925 be mounted
926 Format: <1-256>
928 maxcpus= [SMP] Maximum number of processors that an SMP kernel
929 should make use of.
930 Using "nosmp" or "maxcpus=0" will disable SMP
931 entirely (the MPS table probe still happens, though).
932 A command-line option of "maxcpus=<NUM>", where <NUM>
933 is an integer greater than 0, limits the maximum number
934 of CPUs activated in SMP mode to <NUM>.
935 Using "maxcpus=1" on an SMP kernel is the trivial
936 case of an SMP kernel with only one CPU.
938 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
939 equal to this physical address is ignored.
941 max_luns= [SCSI] Maximum number of LUNs to probe.
942 Should be between 1 and 2^32-1.
944 max_report_luns=
945 [SCSI] Maximum number of LUNs received.
946 Should be between 1 and 16384.
948 mca-pentium [BUGS=IA-32]
950 mcatest= [IA-64]
952 mcd= [HW,CD]
953 Format: <port>,<irq>,<mitsumi_bug_93_wait>
955 mcdx= [HW,CD]
957 mce [IA-32] Machine Check Exception
959 md= [HW] RAID subsystems devices and level
960 See Documentation/md.txt.
962 mdacon= [MDA]
963 Format: <first>,<last>
964 Specifies range of consoles to be captured by the MDA.
966 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
967 Amount of memory to be used when the kernel is not able
968 to see the whole system memory or for test.
969 [IA-32] Use together with memmap= to avoid physical
970 address space collisions. Without memmap= PCI devices
971 could be placed at addresses belonging to unused RAM.
973 mem=nopentium [BUGS=IA-32] Disable usage of 4MB pages for kernel
974 memory.
976 memmap=exactmap [KNL,IA-32,X86_64] Enable setting of an exact
977 E820 memory map, as specified by the user.
978 Such memmap=exactmap lines can be constructed based on
979 BIOS output or other requirements. See the memmap=nn@ss
980 option description.
982 memmap=nn[KMG]@ss[KMG]
983 [KNL] Force usage of a specific region of memory
984 Region of memory to be used, from ss to ss+nn.
986 memmap=nn[KMG]#ss[KMG]
987 [KNL,ACPI] Mark specific memory as ACPI data.
988 Region of memory to be used, from ss to ss+nn.
990 memmap=nn[KMG]$ss[KMG]
991 [KNL,ACPI] Mark specific memory as reserved.
992 Region of memory to be used, from ss to ss+nn.
994 meye.*= [HW] Set MotionEye Camera parameters
995 See Documentation/video4linux/meye.txt.
997 mga= [HW,DRM]
999 migration_cost=
1000 [KNL,SMP] debug: override scheduler migration costs
1001 Format: <level-1-usecs>,<level-2-usecs>,...
1002 This debugging option can be used to override the
1003 default scheduler migration cost matrix. The numbers
1004 are indexed by 'CPU domain distance'.
1005 E.g. migration_cost=1000,2000,3000 on an SMT NUMA
1006 box will set up an intra-core migration cost of
1007 1 msec, an inter-core migration cost of 2 msecs,
1008 and an inter-node migration cost of 3 msecs.
1010 WARNING: using the wrong values here can break
1011 scheduler performance, so it's only for scheduler
1012 development purposes, not production environments.
1014 migration_debug=
1015 [KNL,SMP] migration cost auto-detect verbosity
1016 Format=<0|1|2>
1017 If a system's migration matrix reported at bootup
1018 seems erroneous then this option can be used to
1019 increase verbosity of the detection process.
1020 We default to 0 (no extra messages), 1 will print
1021 some more information, and 2 will be really
1022 verbose (probably only useful if you also have a
1023 serial console attached to the system).
1025 migration_factor=
1026 [KNL,SMP] multiply/divide migration costs by a factor
1027 Format=<percent>
1028 This debug option can be used to proportionally
1029 increase or decrease the auto-detected migration
1030 costs for all entries of the migration matrix.
1031 E.g. migration_factor=150 will increase migration
1032 costs by 50%. (and thus the scheduler will be less
1033 eager migrating cache-hot tasks)
1034 migration_factor=80 will decrease migration costs
1035 by 20%. (thus the scheduler will be more eager to
1036 migrate tasks)
1038 WARNING: using the wrong values here can break
1039 scheduler performance, so it's only for scheduler
1040 development purposes, not production environments.
1042 mousedev.tap_time=
1043 [MOUSE] Maximum time between finger touching and
1044 leaving touchpad surface for touch to be considered
1045 a tap and be reported as a left button click (for
1046 touchpads working in absolute mode only).
1047 Format: <msecs>
1048 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1049 reporting absolute coordinates, such as tablets
1050 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1051 reporting absolute coordinates, such as tablets
1053 mpu401= [HW,OSS]
1054 Format: <io>,<irq>
1056 MTD_Partition= [MTD]
1057 Format: <name>,<region-number>,<size>,<offset>
1059 MTD_Region= [MTD] Format:
1060 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1062 mtdparts= [MTD]
1063 See drivers/mtd/cmdline.c.
1065 mtouchusb.raw_coordinates=
1066 [HW] Make the MicroTouch USB driver use raw coordinates
1067 ('y', default) or cooked coordinates ('n')
1069 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1071 NCR_D700= [HW,SCSI]
1072 See header of drivers/scsi/NCR_D700.c.
1074 ncr5380= [HW,SCSI]
1076 ncr53c400= [HW,SCSI]
1078 ncr53c400a= [HW,SCSI]
1080 ncr53c406a= [HW,SCSI]
1082 ncr53c8xx= [HW,SCSI]
1084 netdev= [NET] Network devices parameters
1085 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1086 Note that mem_start is often overloaded to mean
1087 something different and driver-specific.
1088 This usage is only documented in each driver source
1089 file if at all.
1091 nfsaddrs= [NFS]
1092 See Documentation/nfsroot.txt.
1094 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1095 See Documentation/nfsroot.txt.
1097 nfs.callback_tcpport=
1098 [NFS] set the TCP port on which the NFSv4 callback
1099 channel should listen.
1101 nfs.idmap_cache_timeout=
1102 [NFS] set the maximum lifetime for idmapper cache
1103 entries.
1105 nmi_watchdog= [KNL,BUGS=IA-32] Debugging features for SMP kernels
1107 no387 [BUGS=IA-32] Tells the kernel to use the 387 maths
1108 emulation library even if a 387 maths coprocessor
1109 is present.
1111 noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1112 when set.
1113 Format: <int>
1115 noaliencache [MM, NUMA] Disables the allcoation of alien caches in
1116 the slab allocator. Saves per-node memory, but will
1117 impact performance on real NUMA hardware.
1119 noalign [KNL,ARM]
1121 noapic [SMP,APIC] Tells the kernel to not make use of any
1122 IOAPICs that may be present in the system.
1124 noasync [HW,M68K] Disables async and sync negotiation for
1125 all devices.
1127 nobats [PPC] Do not use BATs for mapping kernel lowmem
1128 on "Classic" PPC cores.
1130 nocache [ARM]
1132 nodelayacct [KNL] Disable per-task delay accounting
1134 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1136 noexec [IA-64]
1138 noexec [IA-32,X86-64]
1139 noexec=on: enable non-executable mappings (default)
1140 noexec=off: disable nn-executable mappings
1142 nofxsr [BUGS=IA-32] Disables x86 floating point extended
1143 register save and restore. The kernel will only save
1144 legacy floating-point registers on task switch.
1146 nohlt [BUGS=ARM]
1148 no-hlt [BUGS=IA-32] Tells the kernel that the hlt
1149 instruction doesn't work correctly and not to
1150 use it.
1152 nohalt [IA-64] Tells the kernel not to use the power saving
1153 function PAL_HALT_LIGHT when idle. This increases
1154 power-consumption. On the positive side, it reduces
1155 interrupt wake-up latency, which may improve performance
1156 in certain environments such as networked servers or
1157 real-time systems.
1159 nohz= [KNL] Boottime enable/disable dynamic ticks
1160 Valid arguments: on, off
1161 Default: on
1163 noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing
1165 noirqdebug [IA-32] Disables the code which attempts to detect and
1166 disable unhandled interrupt sources.
1168 no_timer_check [IA-32,X86_64,APIC] Disables the code which tests for
1169 broken timer IRQ sources.
1171 noisapnp [ISAPNP] Disables ISA PnP code.
1173 noinitrd [RAM] Tells the kernel not to load any configured
1174 initial RAM disk.
1176 nointroute [IA-64]
1178 nolapic [IA-32,APIC] Do not enable or use the local APIC.
1180 nolapic_timer [IA-32,APIC] Do not use the local APIC timer.
1182 noltlbs [PPC] Do not use large page/tlb entries for kernel
1183 lowmem mapping on PPC40x.
1185 nomca [IA-64] Disable machine check abort handling
1187 nomce [IA-32] Machine Check Exception
1189 noreplace-paravirt [IA-32,PV_OPS] Don't patch paravirt_ops
1191 noreplace-smp [IA-32,SMP] Don't replace SMP instructions
1192 with UP alternatives
1194 noresidual [PPC] Don't use residual data on PReP machines.
1196 noresume [SWSUSP] Disables resume and restores original swap
1197 space.
1199 no-scroll [VGA] Disables scrollback.
1200 This is required for the Braillex ib80-piezo Braille
1201 reader made by F.H. Papenmeier (Germany).
1203 nosbagart [IA-64]
1205 nosep [BUGS=IA-32] Disables x86 SYSENTER/SYSEXIT support.
1207 nosmp [SMP] Tells an SMP kernel to act as a UP kernel.
1209 nosync [HW,M68K] Disables sync negotiation for all devices.
1211 notsc [BUGS=IA-32] Disable Time Stamp Counter
1213 nousb [USB] Disable the USB subsystem
1215 nowb [ARM]
1217 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1219 opl3= [HW,OSS]
1220 Format: <io>
1222 opl3sa2= [HW,OSS] Format:
1223 <io>,<irq>,<dma>,<dma2>,<mss_io>,<mpu_io>,<ymode>,<loopback>[,<isapnp>,<multiple]
1225 oprofile.timer= [HW]
1226 Use timer interrupt instead of performance counters
1228 optcd= [HW,CD]
1229 Format: <io>
1231 osst= [HW,SCSI] SCSI Tape Driver
1232 Format: <buffer_size>,<write_threshold>
1233 See also Documentation/scsi/st.txt.
1235 panic= [KNL] Kernel behaviour on panic
1236 Format: <timeout>
1238 parkbd.port= [HW] Parallel port number the keyboard adapter is
1239 connected to, default is 0.
1240 Format: <parport#>
1241 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1242 0 for XT, 1 for AT (default is AT).
1243 Format: <mode>
1245 parport= [HW,PPT] Specify parallel ports. 0 disables.
1246 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1247 Use 'auto' to force the driver to use any
1248 IRQ/DMA settings detected (the default is to
1249 ignore detected IRQ/DMA settings because of
1250 possible conflicts). You can specify the base
1251 address, IRQ, and DMA settings; IRQ and DMA
1252 should be numbers, or 'auto' (for using detected
1253 settings on that particular port), or 'nofifo'
1254 (to avoid using a FIFO even if it is detected).
1255 Parallel ports are assigned in the order they
1256 are specified on the command line, starting
1257 with parport0.
1259 parport_init_mode= [HW,PPT]
1260 Configure VIA parallel port to operate in
1261 a specific mode. This is necessary on Pegasos
1262 computer where firmware has no options for setting
1263 up parallel port mode and sets it to spp.
1264 Currently this function knows 686a and 8231 chips.
1265 Format: [spp|ps2|epp|ecp|ecpepp]
1267 pas2= [HW,OSS] Format:
1268 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1270 pas16= [HW,SCSI]
1271 See header of drivers/scsi/pas16.c.
1273 pause_on_oops=
1274 Halt all CPUs after the first oops has been printed for
1275 the specified number of seconds. This is to be used if
1276 your oopses keep scrolling off the screen.
1278 pcbit= [HW,ISDN]
1280 pcd. [PARIDE]
1281 See header of drivers/block/paride/pcd.c.
1282 See also Documentation/paride.txt.
1284 pci=option[,option...] [PCI] various PCI subsystem options:
1285 off [IA-32] don't probe for the PCI bus
1286 bios [IA-32] force use of PCI BIOS, don't access
1287 the hardware directly. Use this if your machine
1288 has a non-standard PCI host bridge.
1289 nobios [IA-32] disallow use of PCI BIOS, only direct
1290 hardware access methods are allowed. Use this
1291 if you experience crashes upon bootup and you
1292 suspect they are caused by the BIOS.
1293 conf1 [IA-32] Force use of PCI Configuration
1294 Mechanism 1.
1295 conf2 [IA-32] Force use of PCI Configuration
1296 Mechanism 2.
1297 nommconf [IA-32,X86_64] Disable use of MMCONFIG for PCI
1298 Configuration
1299 nomsi [MSI] If the PCI_MSI kernel config parameter is
1300 enabled, this kernel boot option can be used to
1301 disable the use of MSI interrupts system-wide.
1302 nosort [IA-32] Don't sort PCI devices according to
1303 order given by the PCI BIOS. This sorting is
1304 done to get a device order compatible with
1305 older kernels.
1306 biosirq [IA-32] Use PCI BIOS calls to get the interrupt
1307 routing table. These calls are known to be buggy
1308 on several machines and they hang the machine
1309 when used, but on other computers it's the only
1310 way to get the interrupt routing table. Try
1311 this option if the kernel is unable to allocate
1312 IRQs or discover secondary PCI buses on your
1313 motherboard.
1314 rom [IA-32] Assign address space to expansion ROMs.
1315 Use with caution as certain devices share
1316 address decoders between ROMs and other
1317 resources.
1318 irqmask=0xMMMM [IA-32] Set a bit mask of IRQs allowed to be
1319 assigned automatically to PCI devices. You can
1320 make the kernel exclude IRQs of your ISA cards
1321 this way.
1322 pirqaddr=0xAAAAA [IA-32] Specify the physical address
1323 of the PIRQ table (normally generated
1324 by the BIOS) if it is outside the
1325 F0000h-100000h range.
1326 lastbus=N [IA-32] Scan all buses thru bus #N. Can be
1327 useful if the kernel is unable to find your
1328 secondary buses and you want to tell it
1329 explicitly which ones they are.
1330 assign-busses [IA-32] Always assign all PCI bus
1331 numbers ourselves, overriding
1332 whatever the firmware may have done.
1333 usepirqmask [IA-32] Honor the possible IRQ mask stored
1334 in the BIOS $PIR table. This is needed on
1335 some systems with broken BIOSes, notably
1336 some HP Pavilion N5400 and Omnibook XE3
1337 notebooks. This will have no effect if ACPI
1338 IRQ routing is enabled.
1339 noacpi [IA-32] Do not use ACPI for IRQ routing
1340 or for PCI scanning.
1341 routeirq Do IRQ routing for all PCI devices.
1342 This is normally done in pci_enable_device(),
1343 so this option is a temporary workaround
1344 for broken drivers that don't call it.
1345 firmware [ARM] Do not re-enumerate the bus but instead
1346 just use the configuration from the
1347 bootloader. This is currently used on
1348 IXP2000 systems where the bus has to be
1349 configured a certain way for adjunct CPUs.
1350 noearly [X86] Don't do any early type 1 scanning.
1351 This might help on some broken boards which
1352 machine check when some devices' config space
1353 is read. But various workarounds are disabled
1354 and some IOMMU drivers will not work.
1355 bfsort Sort PCI devices into breadth-first order.
1356 This sorting is done to get a device
1357 order compatible with older (<= 2.4) kernels.
1358 nobfsort Don't sort PCI devices into breadth-first order.
1359 cbiosize=nn[KMG] The fixed amount of bus space which is
1360 reserved for the CardBus bridge's IO window.
1361 The default value is 256 bytes.
1362 cbmemsize=nn[KMG] The fixed amount of bus space which is
1363 reserved for the CardBus bridge's memory
1364 window. The default value is 64 megabytes.
1366 pcmv= [HW,PCMCIA] BadgePAD 4
1368 pd. [PARIDE]
1369 See Documentation/paride.txt.
1371 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1372 boot time.
1373 Format: { 0 | 1 }
1374 See arch/parisc/kernel/pdc_chassis.c
1376 pf. [PARIDE]
1377 See Documentation/paride.txt.
1379 pg. [PARIDE]
1380 See Documentation/paride.txt.
1382 pirq= [SMP,APIC] Manual mp-table setup
1383 See Documentation/i386/IO-APIC.txt.
1385 plip= [PPT,NET] Parallel port network link
1386 Format: { parport<nr> | timid | 0 }
1387 See also Documentation/parport.txt.
1389 pnpacpi= [ACPI]
1390 { off }
1392 pnpbios= [ISAPNP]
1393 { on | off | curr | res | no-curr | no-res }
1395 pnp_reserve_irq=
1396 [ISAPNP] Exclude IRQs for the autoconfiguration
1398 pnp_reserve_dma=
1399 [ISAPNP] Exclude DMAs for the autoconfiguration
1401 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1402 Ranges are in pairs (I/O port base and size).
1404 pnp_reserve_mem=
1405 [ISAPNP] Exclude memory regions for the
1406 autoconfiguration.
1407 Ranges are in pairs (memory base and size).
1409 profile= [KNL] Enable kernel profiling via /proc/profile
1410 Format: [schedule,]<number>
1411 Param: "schedule" - profile schedule points.
1412 Param: <number> - step/bucket size as a power of 2 for
1413 statistical time based profiling.
1414 Param: "sleep" - profile D-state sleeping (millisecs)
1416 processor.max_cstate= [HW,ACPI]
1417 Limit processor to maximum C-state
1418 max_cstate=9 overrides any DMI blacklist limit.
1420 processor.nocst [HW,ACPI]
1421 Ignore the _CST method to determine C-states,
1422 instead using the legacy FADT method
1424 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1425 before loading.
1426 See Documentation/ramdisk.txt.
1428 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1429 probe for; one of (bare|imps|exps|lifebook|any).
1430 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1431 per second.
1432 psmouse.resetafter= [HW,MOUSE]
1433 Try to reset the device after so many bad packets
1434 (0 = never).
1435 psmouse.resolution=
1436 [HW,MOUSE] Set desired mouse resolution, in dpi.
1437 psmouse.smartscroll=
1438 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1439 0 = disabled, 1 = enabled (default).
1441 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1442 Format:
1443 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1445 pt. [PARIDE]
1446 See Documentation/paride.txt.
1448 quiet [KNL] Disable most log messages
1450 r128= [HW,DRM]
1452 raid= [HW,RAID]
1453 See Documentation/md.txt.
1455 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1456 See Documentation/ramdisk.txt.
1458 ramdisk_blocksize= [RAM]
1459 See Documentation/ramdisk.txt.
1461 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1462 New name for the ramdisk parameter.
1463 See Documentation/ramdisk.txt.
1465 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1466 RCU callbacks to process in one batch.
1468 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1469 RCU callbacks over which batch limiting is disabled.
1471 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1472 RCU callbacks below which batch limiting is re-enabled.
1474 rdinit= [KNL]
1475 Format: <full_path>
1476 Run specified binary instead of /init from the ramdisk,
1477 used for early userspace startup. See initrd.
1479 reboot= [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1480 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1481 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1483 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1485 reservetop= [IA-32]
1486 Format: nn[KMG]
1487 Reserves a hole at the top of the kernel virtual
1488 address space.
1490 reset_devices [KNL] Force drivers to reset the underlying device
1491 during initialization.
1493 resume= [SWSUSP]
1494 Specify the partition device for software suspend
1496 resume_offset= [SWSUSP]
1497 Specify the offset from the beginning of the partition
1498 given by "resume=" at which the swap header is located,
1499 in <PAGE_SIZE> units (needed only for swap files).
1500 See Documentation/power/swsusp-and-swap-files.txt
1502 retain_initrd [RAM] Keep initrd memory after extraction
1504 rhash_entries= [KNL,NET]
1505 Set number of hash buckets for route cache
1507 riscom8= [HW,SERIAL]
1508 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1510 ro [KNL] Mount root device read-only on boot
1512 root= [KNL] Root filesystem
1514 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1515 mount the root filesystem
1517 rootflags= [KNL] Set root filesystem mount option string
1519 rootfstype= [KNL] Set root filesystem type
1521 rw [KNL] Mount root device read-write on boot
1523 S [KNL] Run init in single mode
1525 sa1100ir [NET]
1526 See drivers/net/irda/sa1100_ir.c.
1528 sb= [HW,OSS]
1529 Format: <io>,<irq>,<dma>,<dma2>
1531 sbni= [NET] Granch SBNI12 leased line adapter
1533 sbpcd= [HW,CD] Soundblaster CD adapter
1534 Format: <io>,<type>
1535 See a comment before function sbpcd_setup() in
1536 drivers/cdrom/sbpcd.c.
1538 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1539 Format: <io>[,<timeout>[,<isapnp>]]
1541 scsi_debug_*= [SCSI]
1542 See drivers/scsi/scsi_debug.c.
1544 scsi_default_dev_flags=
1545 [SCSI] SCSI default device flags
1546 Format: <integer>
1548 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1549 Format: <vendor>:<model>:<flags>
1550 (flags are integer value)
1552 scsi_logging= [SCSI]
1554 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1555 discovered. async scans them in kernel threads,
1556 allowing boot to proceed. none ignores them, expecting
1557 user space to do the scan.
1559 selinux [SELINUX] Disable or enable SELinux at boot time.
1560 Format: { "0" | "1" }
1561 See security/selinux/Kconfig help text.
1562 0 -- disable.
1563 1 -- enable.
1564 Default value is set via kernel config option.
1565 If enabled at boot time, /selinux/disable can be used
1566 later to disable prior to initial policy load.
1568 selinux_compat_net =
1569 [SELINUX] Set initial selinux_compat_net flag value.
1570 Format: { "0" | "1" }
1571 0 -- use new secmark-based packet controls
1572 1 -- use legacy packet controls
1573 Default value is 0 (preferred).
1574 Value can be changed at runtime via
1575 /selinux/compat_net.
1577 serialnumber [BUGS=IA-32]
1579 sg_def_reserved_size= [SCSI]
1581 shapers= [NET]
1582 Maximal number of shapers.
1584 sim710= [SCSI,HW]
1585 See header of drivers/scsi/sim710.c.
1587 simeth= [IA-64]
1588 simscsi=
1590 sjcd= [HW,CD]
1591 Format: <io>,<irq>,<dma>
1592 See header of drivers/cdrom/sjcd.c.
1594 slram= [HW,MTD]
1596 smart2= [HW]
1597 Format: <io1>[,<io2>[,...,<io8>]]
1599 smp-alt-once [IA-32,SMP] On a hotplug CPU system, only
1600 attempt to substitute SMP alternatives once at boot.
1602 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1603 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1604 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1605 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1606 smsc-ircc2.ircc_irq= [HW] IRQ line
1607 smsc-ircc2.ircc_dma= [HW] DMA channel
1608 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1609 0: Toshiba Satellite 1800 (GP data pin select)
1610 1: Fast pin select (default)
1611 2: ATC IRMode
1613 snd-ad1816a= [HW,ALSA]
1615 snd-ad1848= [HW,ALSA]
1617 snd-ali5451= [HW,ALSA]
1619 snd-als100= [HW,ALSA]
1621 snd-als4000= [HW,ALSA]
1623 snd-azt2320= [HW,ALSA]
1625 snd-cmi8330= [HW,ALSA]
1627 snd-cmipci= [HW,ALSA]
1629 snd-cs4231= [HW,ALSA]
1631 snd-cs4232= [HW,ALSA]
1633 snd-cs4236= [HW,ALSA]
1635 snd-cs4281= [HW,ALSA]
1637 snd-cs46xx= [HW,ALSA]
1639 snd-dt019x= [HW,ALSA]
1641 snd-dummy= [HW,ALSA]
1643 snd-emu10k1= [HW,ALSA]
1645 snd-ens1370= [HW,ALSA]
1647 snd-ens1371= [HW,ALSA]
1649 snd-es968= [HW,ALSA]
1651 snd-es1688= [HW,ALSA]
1653 snd-es18xx= [HW,ALSA]
1655 snd-es1938= [HW,ALSA]
1657 snd-es1968= [HW,ALSA]
1659 snd-fm801= [HW,ALSA]
1661 snd-gusclassic= [HW,ALSA]
1663 snd-gusextreme= [HW,ALSA]
1665 snd-gusmax= [HW,ALSA]
1667 snd-hdsp= [HW,ALSA]
1669 snd-ice1712= [HW,ALSA]
1671 snd-intel8x0= [HW,ALSA]
1673 snd-interwave= [HW,ALSA]
1675 snd-interwave-stb=
1676 [HW,ALSA]
1678 snd-korg1212= [HW,ALSA]
1680 snd-maestro3= [HW,ALSA]
1682 snd-mpu401= [HW,ALSA]
1684 snd-mtpav= [HW,ALSA]
1686 snd-nm256= [HW,ALSA]
1688 snd-opl3sa2= [HW,ALSA]
1690 snd-opti92x-ad1848=
1691 [HW,ALSA]
1693 snd-opti92x-cs4231=
1694 [HW,ALSA]
1696 snd-opti93x= [HW,ALSA]
1698 snd-pmac= [HW,ALSA]
1700 snd-rme32= [HW,ALSA]
1702 snd-rme96= [HW,ALSA]
1704 snd-rme9652= [HW,ALSA]
1706 snd-sb8= [HW,ALSA]
1708 snd-sb16= [HW,ALSA]
1710 snd-sbawe= [HW,ALSA]
1712 snd-serial= [HW,ALSA]
1714 snd-sgalaxy= [HW,ALSA]
1716 snd-sonicvibes= [HW,ALSA]
1718 snd-sun-amd7930=
1719 [HW,ALSA]
1721 snd-sun-cs4231= [HW,ALSA]
1723 snd-trident= [HW,ALSA]
1725 snd-usb-audio= [HW,ALSA,USB]
1727 snd-via82xx= [HW,ALSA]
1729 snd-virmidi= [HW,ALSA]
1731 snd-wavefront= [HW,ALSA]
1733 snd-ymfpci= [HW,ALSA]
1735 sonycd535= [HW,CD]
1736 Format: <io>[,<irq>]
1738 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1739 See Documentation/sonypi.txt
1741 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1742 See Documentation/specialix.txt.
1744 spia_io_base= [HW,MTD]
1745 spia_fio_base=
1746 spia_pedr=
1747 spia_peddr=
1749 sscape= [HW,OSS]
1750 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1752 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1753 See Documentation/scsi/st.txt.
1755 st0x= [HW,SCSI]
1756 See header of drivers/scsi/seagate.c.
1758 sti= [PARISC,HW]
1759 Format: <num>
1760 Set the STI (builtin display/keyboard on the HP-PARISC
1761 machines) console (graphic card) which should be used
1762 as the initial boot-console.
1763 See also comment in drivers/video/console/sticore.c.
1765 sti_font= [HW]
1766 See comment in drivers/video/console/sticore.c.
1768 stifb= [HW]
1769 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1771 sunrpc.pool_mode=
1772 [NFS]
1773 Control how the NFS server code allocates CPUs to
1774 service thread pools. Depending on how many NICs
1775 you have and where their interrupts are bound, this
1776 option will affect which CPUs will do NFS serving.
1777 Note: this parameter cannot be changed while the
1778 NFS server is running.
1780 auto the server chooses an appropriate mode
1781 automatically using heuristics
1782 global a single global pool contains all CPUs
1783 percpu one pool for each CPU
1784 pernode one pool for each NUMA node (equivalent
1785 to global on non-NUMA machines)
1787 swiotlb= [IA-64] Number of I/O TLB slabs
1789 switches= [HW,M68k]
1791 sym53c416= [HW,SCSI]
1792 See header of drivers/scsi/sym53c416.c.
1794 sysrq_always_enabled
1795 [KNL]
1796 Ignore sysrq setting - this boot parameter will
1797 neutralize any effect of /proc/sys/kernel/sysrq.
1798 Useful for debugging.
1800 t128= [HW,SCSI]
1801 See header of drivers/scsi/t128.c.
1803 tdfx= [HW,DRM]
1805 thash_entries= [KNL,NET]
1806 Set number of hash buckets for TCP connection
1808 time Show timing data prefixed to each printk message line
1810 clocksource= [GENERIC_TIME] Override the default clocksource
1811 Override the default clocksource and use the clocksource
1812 with the name specified.
1814 tipar.timeout= [HW,PPT]
1815 Set communications timeout in tenths of a second
1816 (default 15).
1818 tipar.delay= [HW,PPT]
1819 Set inter-bit delay in microseconds (default 10).
1821 tmc8xx= [HW,SCSI]
1822 See header of drivers/scsi/seagate.c.
1824 tmscsim= [HW,SCSI]
1825 See comment before function dc390_setup() in
1826 drivers/scsi/tmscsim.c.
1828 tp720= [HW,PS2]
1830 trix= [HW,OSS] MediaTrix AudioTrix Pro
1831 Format:
1832 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1834 tsdev.xres= [TS] Horizontal screen resolution.
1835 tsdev.yres= [TS] Vertical screen resolution.
1837 turbografx.map[2|3]= [HW,JOY]
1838 TurboGraFX parallel port interface
1839 Format:
1840 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1841 See also Documentation/input/joystick-parport.txt
1843 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1844 See header of drivers/scsi/u14-34f.c.
1846 uart401= [HW,OSS]
1847 Format: <io>,<irq>
1849 uart6850= [HW,OSS]
1850 Format: <io>,<irq>
1852 uhci-hcd.ignore_oc=
1853 [USB] Ignore overcurrent events (default N).
1854 Some badly-designed motherboards generate lots of
1855 bogus events, for ports that aren't wired to
1856 anything. Set this parameter to avoid log spamming.
1857 Note that genuine overcurrent events won't be
1858 reported either.
1860 usbcore.autosuspend=
1861 [USB] The autosuspend time delay (in seconds) used
1862 for newly-detected USB devices (default 2). This
1863 is the time required before an idle device will be
1864 autosuspended. Devices for which the delay is set
1865 to a negative value won't be autosuspended at all.
1867 usbhid.mousepoll=
1868 [USBHID] The interval which mice are to be polled at.
1870 vdso= [IA-32,SH]
1871 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1872 vdso=1: enable VDSO (default)
1873 vdso=0: disable VDSO mapping
1875 video= [FB] Frame buffer configuration
1876 See Documentation/fb/modedb.txt.
1878 vga= [BOOT,IA-32] Select a particular video mode
1879 See Documentation/i386/boot.txt and
1880 Documentation/svga.txt.
1881 Use vga=ask for menu.
1882 This is actually a boot loader parameter; the value is
1883 passed to the kernel using a special protocol.
1885 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1886 size of <nn>. This can be used to increase the
1887 minimum size (128MB on x86). It can also be used to
1888 decrease the size and leave more room for directly
1889 mapped kernel RAM.
1891 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1892 Format: <command>
1894 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1895 Format: <command>
1897 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1898 Format: <command>
1900 waveartist= [HW,OSS]
1901 Format: <io>,<irq>,<dma>,<dma2>
1903 wd33c93= [HW,SCSI]
1904 See header of drivers/scsi/wd33c93.c.
1906 wd7000= [HW,SCSI]
1907 See header of drivers/scsi/wd7000.c.
1909 wdt= [WDT] Watchdog
1910 See Documentation/watchdog/watchdog.txt.
1912 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1913 xd_geo= See header of drivers/block/xd.c.
1915 xirc2ps_cs= [NET,PCMCIA]
1916 Format:
1917 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1919 norandmaps Don't use address space randomization
1920 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1922 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1923 This is useful to get more information why
1924 you got a "dwarf2 unwinder stuck"
1926 ______________________________________________________________________
1928 TODO:
1930 Add documentation for ALSA options.
1931 Add more DRM drivers.