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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 dhash_entries= [KNL]
500 Set number of hash buckets for dentry cache.
502 digi= [HW,SERIAL]
503 IO parameters + enable/disable command.
505 digiepca= [HW,SERIAL]
506 See drivers/char/README.epca and
507 Documentation/digiepca.txt.
509 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
510 support available.
511 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
513 dmasound= [HW,OSS] Sound subsystem buffers
515 dscc4.setup= [NET]
517 dtc3181e= [HW,SCSI]
519 earlyprintk= [IA-32,X86-64,SH]
520 earlyprintk=vga
521 earlyprintk=serial[,ttySn[,baudrate]]
523 Append ",keep" to not disable it when the real console
524 takes over.
526 Only vga or serial at a time, not both.
528 Currently only ttyS0 and ttyS1 are supported.
530 Interaction with the standard serial driver is not
531 very good.
533 The VGA output is eventually overwritten by the real
534 console.
536 eata= [HW,SCSI]
538 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
539 Format: <int>
540 0: polling mode
541 non-0: interrupt mode (default)
543 eda= [HW,PS2]
545 edb= [HW,PS2]
547 edd= [EDD]
548 Format: {"of[f]" | "sk[ipmbr]"}
549 See comment in arch/i386/boot/edd.S
551 eicon= [HW,ISDN]
552 Format: <id>,<membase>,<irq>
554 eisa_irq_edge= [PARISC,HW]
555 See header of drivers/parisc/eisa.c.
557 elanfreq= [IA-32]
558 See comment before function elanfreq_setup() in
559 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
561 elevator= [IOSCHED]
562 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
563 See Documentation/block/as-iosched.txt and
564 Documentation/block/deadline-iosched.txt for details.
566 elfcorehdr= [IA-32, X86_64]
567 Specifies physical address of start of kernel core
568 image elf header. Generally kexec loader will
569 pass this option to capture kernel.
570 See Documentation/kdump/kdump.txt for details.
572 enforcing [SELINUX] Set initial enforcing status.
573 Format: {"0" | "1"}
574 See security/selinux/Kconfig help text.
575 0 -- permissive (log only, no denials).
576 1 -- enforcing (deny and log).
577 Default value is 0.
578 Value can be changed at runtime via /selinux/enforce.
580 es1371= [HW,OSS]
581 Format: <spdif>,[<nomix>,[<amplifier>]]
582 See also header of sound/oss/es1371.c.
584 ether= [HW,NET] Ethernet cards parameters
585 This option is obsoleted by the "netdev=" option, which
586 has equivalent usage. See its documentation for details.
588 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
589 Format: <io>[,<irq>]
591 failslab=
592 fail_page_alloc=
593 fail_make_request=[KNL]
594 General fault injection mechanism.
595 Format: <interval>,<probability>,<space>,<times>
596 See also /Documentation/fault-injection/.
598 fd_mcs= [HW,SCSI]
599 See header of drivers/scsi/fd_mcs.c.
601 fdomain= [HW,SCSI]
602 See header of drivers/scsi/fdomain.c.
604 floppy= [HW]
605 See Documentation/floppy.txt.
607 gamecon.map[2|3]=
608 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
609 support via parallel port (up to 5 devices per port)
610 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
611 See also Documentation/input/joystick-parport.txt
613 gamma= [HW,DRM]
615 gdth= [HW,SCSI]
616 See header of drivers/scsi/gdth.c.
618 gpt [EFI] Forces disk with valid GPT signature but
619 invalid Protective MBR to be treated as GPT.
621 gscd= [HW,CD]
622 Format: <io>
624 gvp11= [HW,SCSI]
626 hashdist= [KNL,NUMA] Large hashes allocated during boot
627 are distributed across NUMA nodes. Defaults on
628 for IA-64, off otherwise.
629 Format: 0 | 1 (for off | on)
631 hcl= [IA-64] SGI's Hardware Graph compatibility layer
633 hd= [EIDE] (E)IDE hard drive subsystem geometry
634 Format: <cyl>,<head>,<sect>
636 hd?= [HW] (E)IDE subsystem
637 hd?lun= See Documentation/ide.txt.
639 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
640 size of <nn>. This works even on boxes that have no
641 highmem otherwise. This also works to reduce highmem
642 size on bigger boxes.
644 highres= [KNL] Enable/disable high resolution timer mode.
645 Valid parameters: "on", "off"
646 Default: "on"
648 hisax= [HW,ISDN]
649 See Documentation/isdn/README.HiSax.
651 hugepages= [HW,IA-32,IA-64] Maximal number of HugeTLB pages.
653 i8042.direct [HW] Put keyboard port into non-translated mode
654 i8042.dumbkbd [HW] Pretend that controller can only read data from
655 keyboard and cannot control its state
656 (Don't attempt to blink the leds)
657 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
658 i8042.nokbd [HW] Don't check/create keyboard port
659 i8042.nomux [HW] Don't check presence of an active multiplexing
660 controller
661 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
662 controllers
663 i8042.panicblink=
664 [HW] Frequency with which keyboard LEDs should blink
665 when kernel panics (default is 0.5 sec)
666 i8042.reset [HW] Reset the controller during init and cleanup
667 i8042.unlock [HW] Unlock (ignore) the keylock
669 i810= [HW,DRM]
671 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
672 indicates that the driver is running on unsupported
673 hardware.
674 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
675 does not match list of supported models.
676 i8k.power_status
677 [HW] Report power status in /proc/i8k
678 (disabled by default)
679 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
680 capability is set.
682 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
683 See Documentation/mca.txt.
685 icn= [HW,ISDN]
686 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
688 ide= [HW] (E)IDE subsystem
689 Format: ide=nodma or ide=doubler or ide=reverse
690 See Documentation/ide.txt.
692 ide?= [HW] (E)IDE subsystem
693 Format: ide?=noprobe or chipset specific parameters.
694 See Documentation/ide.txt.
696 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
697 See Documentation/ide.txt.
699 idle= [X86]
700 Format: idle=poll or idle=mwait
701 Poll forces a polling idle loop that can slightly improves the performance
702 of waking up a idle CPU, but will use a lot of power and make the system
703 run hot. Not recommended.
704 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
705 to not use it because it doesn't save as much power as a normal idle
706 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
707 as idle=poll.
709 ignore_loglevel [KNL]
710 Ignore loglevel setting - this will print /all/
711 kernel messages to the console. Useful for debugging.
713 ihash_entries= [KNL]
714 Set number of hash buckets for inode cache.
716 in2000= [HW,SCSI]
717 See header of drivers/scsi/in2000.c.
719 init= [KNL]
720 Format: <full_path>
721 Run specified binary instead of /sbin/init as init
722 process.
724 initcall_debug [KNL] Trace initcalls as they are executed. Useful
725 for working out where the kernel is dying during
726 startup.
728 initrd= [BOOT] Specify the location of the initial ramdisk
730 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
731 Format: <irq>
733 combined_mode= [HW] control which driver uses IDE ports in combined
734 mode: legacy IDE driver, libata, or both
735 (in the libata case, libata.atapi_enabled=1 may be
736 useful as well). Note that using the ide or libata
737 options may affect your device naming (e.g. by
738 changing hdc to sdb).
739 Format: combined (default), ide, or libata
741 inttest= [IA64]
743 io7= [HW] IO7 for Marvel based alpha systems
744 See comment before marvel_specify_io7 in
745 arch/alpha/kernel/core_marvel.c.
747 ip= [IP_PNP]
748 See Documentation/nfsroot.txt.
750 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
751 See comment before ip2_setup() in drivers/char/ip2.c.
753 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
754 See header of drivers/scsi/ips.c.
756 ports= [IP_VS_FTP] IPVS ftp helper module
757 Default is 21.
758 Up to 8 (IP_VS_APP_MAX_PORTS) ports
759 may be specified.
760 Format: <port>,<port>....
762 irqfixup [HW]
763 When an interrupt is not handled search all handlers
764 for it. Intended to get systems with badly broken
765 firmware running.
767 irqpoll [HW]
768 When an interrupt is not handled search all handlers
769 for it. Also check all handlers each timer
770 interrupt. Intended to get systems with badly broken
771 firmware running.
773 isapnp= [ISAPNP]
774 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
776 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
777 Format:
778 <cpu number>,...,<cpu number>
779 or
780 <cpu number>-<cpu number> (must be a positive range in ascending order)
781 or a mixture
782 <cpu number>,...,<cpu number>-<cpu number>
783 This option can be used to specify one or more CPUs
784 to isolate from the general SMP balancing and scheduling
785 algorithms. The only way to move a process onto or off
786 an "isolated" CPU is via the CPU affinity syscalls.
787 <cpu number> begins at 0 and the maximum value is
788 "number of CPUs in system - 1".
790 This option is the preferred way to isolate CPUs. The
791 alternative -- manually setting the CPU mask of all
792 tasks in the system -- can cause problems and
793 suboptimal load balancer performance.
795 isp16= [HW,CD]
796 Format: <io>,<irq>,<dma>,<setup>
798 iucv= [HW,NET]
800 js= [HW,JOY] Analog joystick
801 See Documentation/input/joystick.txt.
803 keepinitrd [HW,ARM]
805 kstack=N [IA-32,X86-64] Print N words from the kernel stack
806 in oops dumps.
808 l2cr= [PPC]
810 lapic [IA-32,APIC] Enable the local APIC even if BIOS
811 disabled it.
813 lapic_timer_c2_ok [IA-32,x86-64,APIC] trust the local apic timer in
814 C2 power state.
816 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
817 Format: addr:<io>,irq:<irq>
819 llsc*= [IA64] See function print_params() in
820 arch/ia64/sn/kernel/llsc4.c.
822 load_ramdisk= [RAM] List of ramdisks to load from floppy
823 See Documentation/ramdisk.txt.
825 lockd.nlm_grace_period=P [NFS] Assign grace period.
826 Format: <integer>
828 lockd.nlm_tcpport=N [NFS] Assign TCP port.
829 Format: <integer>
831 lockd.nlm_timeout=T [NFS] Assign timeout value.
832 Format: <integer>
834 lockd.nlm_udpport=M [NFS] Assign UDP port.
835 Format: <integer>
837 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
838 Format: <irq>
840 loglevel= All Kernel Messages with a loglevel smaller than the
841 console loglevel will be printed to the console. It can
842 also be changed with klogd or other programs. The
843 loglevels are defined as follows:
845 0 (KERN_EMERG) system is unusable
846 1 (KERN_ALERT) action must be taken immediately
847 2 (KERN_CRIT) critical conditions
848 3 (KERN_ERR) error conditions
849 4 (KERN_WARNING) warning conditions
850 5 (KERN_NOTICE) normal but significant condition
851 6 (KERN_INFO) informational
852 7 (KERN_DEBUG) debug-level messages
854 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
855 Format: { n | nk | nM }
856 n must be a power of two. The default size
857 is set in the kernel config file.
859 lp=0 [LP] Specify parallel ports to use, e.g,
860 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
861 lp=reset first parallel port). 'lp=0' disables the
862 lp=auto printer driver. 'lp=reset' (which can be
863 specified in addition to the ports) causes
864 attached printers to be reset. Using
865 lp=port1,port2,... specifies the parallel ports
866 to associate lp devices with, starting with
867 lp0. A port specification may be 'none' to skip
868 that lp device, or a parport name such as
869 'parport0'. Specifying 'lp=auto' instead of a
870 port specification list means that device IDs
871 from each port should be examined, to see if
872 an IEEE 1284-compliant printer is attached; if
873 so, the driver will manage that printer.
874 See also header of drivers/char/lp.c.
876 lpj=n [KNL]
877 Sets loops_per_jiffy to given constant, thus avoiding
878 time-consuming boot-time autodetection (up to 250 ms per
879 CPU). 0 enables autodetection (default). To determine
880 the correct value for your kernel, boot with normal
881 autodetection and see what value is printed. Note that
882 on SMP systems the preset will be applied to all CPUs,
883 which is likely to cause problems if your CPUs need
884 significantly divergent settings. An incorrect value
885 will cause delays in the kernel to be wrong, leading to
886 unpredictable I/O errors and other breakage. Although
887 unlikely, in the extreme case this might damage your
888 hardware.
890 ltpc= [NET]
891 Format: <io>,<irq>,<dma>
893 mac5380= [HW,SCSI] Format:
894 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
896 mac53c9x= [HW,SCSI] Format:
897 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
899 machvec= [IA64] Force the use of a particular machine-vector
900 (machvec) in a generic kernel.
901 Example: machvec=hpzx1_swiotlb
903 max_loop= [LOOP] Maximum number of loopback devices that can
904 be mounted
905 Format: <1-256>
907 maxcpus= [SMP] Maximum number of processors that an SMP kernel
908 should make use of.
909 Using "nosmp" or "maxcpus=0" will disable SMP
910 entirely (the MPS table probe still happens, though).
911 A command-line option of "maxcpus=<NUM>", where <NUM>
912 is an integer greater than 0, limits the maximum number
913 of CPUs activated in SMP mode to <NUM>.
914 Using "maxcpus=1" on an SMP kernel is the trivial
915 case of an SMP kernel with only one CPU.
917 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
918 equal to this physical address is ignored.
920 max_luns= [SCSI] Maximum number of LUNs to probe.
921 Should be between 1 and 2^32-1.
923 max_report_luns=
924 [SCSI] Maximum number of LUNs received.
925 Should be between 1 and 16384.
927 mca-pentium [BUGS=IA-32]
929 mcatest= [IA-64]
931 mcd= [HW,CD]
932 Format: <port>,<irq>,<mitsumi_bug_93_wait>
934 mcdx= [HW,CD]
936 mce [IA-32] Machine Check Exception
938 md= [HW] RAID subsystems devices and level
939 See Documentation/md.txt.
941 mdacon= [MDA]
942 Format: <first>,<last>
943 Specifies range of consoles to be captured by the MDA.
945 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
946 Amount of memory to be used when the kernel is not able
947 to see the whole system memory or for test.
948 [IA-32] Use together with memmap= to avoid physical
949 address space collisions. Without memmap= PCI devices
950 could be placed at addresses belonging to unused RAM.
952 mem=nopentium [BUGS=IA-32] Disable usage of 4MB pages for kernel
953 memory.
955 memmap=exactmap [KNL,IA-32,X86_64] Enable setting of an exact
956 E820 memory map, as specified by the user.
957 Such memmap=exactmap lines can be constructed based on
958 BIOS output or other requirements. See the memmap=nn@ss
959 option description.
961 memmap=nn[KMG]@ss[KMG]
962 [KNL] Force usage of a specific region of memory
963 Region of memory to be used, from ss to ss+nn.
965 memmap=nn[KMG]#ss[KMG]
966 [KNL,ACPI] Mark specific memory as ACPI data.
967 Region of memory to be used, from ss to ss+nn.
969 memmap=nn[KMG]$ss[KMG]
970 [KNL,ACPI] Mark specific memory as reserved.
971 Region of memory to be used, from ss to ss+nn.
973 meye.*= [HW] Set MotionEye Camera parameters
974 See Documentation/video4linux/meye.txt.
976 mga= [HW,DRM]
978 migration_cost=
979 [KNL,SMP] debug: override scheduler migration costs
980 Format: <level-1-usecs>,<level-2-usecs>,...
981 This debugging option can be used to override the
982 default scheduler migration cost matrix. The numbers
983 are indexed by 'CPU domain distance'.
984 E.g. migration_cost=1000,2000,3000 on an SMT NUMA
985 box will set up an intra-core migration cost of
986 1 msec, an inter-core migration cost of 2 msecs,
987 and an inter-node migration cost of 3 msecs.
989 WARNING: using the wrong values here can break
990 scheduler performance, so it's only for scheduler
991 development purposes, not production environments.
993 migration_debug=
994 [KNL,SMP] migration cost auto-detect verbosity
995 Format=<0|1|2>
996 If a system's migration matrix reported at bootup
997 seems erroneous then this option can be used to
998 increase verbosity of the detection process.
999 We default to 0 (no extra messages), 1 will print
1000 some more information, and 2 will be really
1001 verbose (probably only useful if you also have a
1002 serial console attached to the system).
1004 migration_factor=
1005 [KNL,SMP] multiply/divide migration costs by a factor
1006 Format=<percent>
1007 This debug option can be used to proportionally
1008 increase or decrease the auto-detected migration
1009 costs for all entries of the migration matrix.
1010 E.g. migration_factor=150 will increase migration
1011 costs by 50%. (and thus the scheduler will be less
1012 eager migrating cache-hot tasks)
1013 migration_factor=80 will decrease migration costs
1014 by 20%. (thus the scheduler will be more eager to
1015 migrate tasks)
1017 WARNING: using the wrong values here can break
1018 scheduler performance, so it's only for scheduler
1019 development purposes, not production environments.
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] Disables the allcoation of alien caches in
1095 the slab allocator. Saves per-node memory, but will
1096 impact performance on real NUMA hardware.
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 nolapic [IA-32,APIC] Do not enable or use the local APIC.
1159 nolapic_timer [IA-32,APIC] Do not use the local APIC timer.
1161 noltlbs [PPC] Do not use large page/tlb entries for kernel
1162 lowmem mapping on PPC40x.
1164 nomca [IA-64] Disable machine check abort handling
1166 nomce [IA-32] Machine Check Exception
1168 noreplace-paravirt [IA-32,PV_OPS] Don't patch paravirt_ops
1170 noreplace-smp [IA-32,SMP] Don't replace SMP instructions
1171 with UP alternatives
1173 noresidual [PPC] Don't use residual data on PReP machines.
1175 noresume [SWSUSP] Disables resume and restores original swap
1176 space.
1178 no-scroll [VGA] Disables scrollback.
1179 This is required for the Braillex ib80-piezo Braille
1180 reader made by F.H. Papenmeier (Germany).
1182 nosbagart [IA-64]
1184 nosep [BUGS=IA-32] Disables x86 SYSENTER/SYSEXIT support.
1186 nosmp [SMP] Tells an SMP kernel to act as a UP kernel.
1188 nosync [HW,M68K] Disables sync negotiation for all devices.
1190 notsc [BUGS=IA-32] Disable Time Stamp Counter
1192 nousb [USB] Disable the USB subsystem
1194 nowb [ARM]
1196 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1198 opl3= [HW,OSS]
1199 Format: <io>
1201 opl3sa2= [HW,OSS] Format:
1202 <io>,<irq>,<dma>,<dma2>,<mss_io>,<mpu_io>,<ymode>,<loopback>[,<isapnp>,<multiple]
1204 oprofile.timer= [HW]
1205 Use timer interrupt instead of performance counters
1207 optcd= [HW,CD]
1208 Format: <io>
1210 osst= [HW,SCSI] SCSI Tape Driver
1211 Format: <buffer_size>,<write_threshold>
1212 See also Documentation/scsi/st.txt.
1214 panic= [KNL] Kernel behaviour on panic
1215 Format: <timeout>
1217 parkbd.port= [HW] Parallel port number the keyboard adapter is
1218 connected to, default is 0.
1219 Format: <parport#>
1220 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1221 0 for XT, 1 for AT (default is AT).
1222 Format: <mode>
1224 parport= [HW,PPT] Specify parallel ports. 0 disables.
1225 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1226 Use 'auto' to force the driver to use any
1227 IRQ/DMA settings detected (the default is to
1228 ignore detected IRQ/DMA settings because of
1229 possible conflicts). You can specify the base
1230 address, IRQ, and DMA settings; IRQ and DMA
1231 should be numbers, or 'auto' (for using detected
1232 settings on that particular port), or 'nofifo'
1233 (to avoid using a FIFO even if it is detected).
1234 Parallel ports are assigned in the order they
1235 are specified on the command line, starting
1236 with parport0.
1238 parport_init_mode= [HW,PPT]
1239 Configure VIA parallel port to operate in
1240 a specific mode. This is necessary on Pegasos
1241 computer where firmware has no options for setting
1242 up parallel port mode and sets it to spp.
1243 Currently this function knows 686a and 8231 chips.
1244 Format: [spp|ps2|epp|ecp|ecpepp]
1246 pas2= [HW,OSS] Format:
1247 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1249 pas16= [HW,SCSI]
1250 See header of drivers/scsi/pas16.c.
1252 pause_on_oops=
1253 Halt all CPUs after the first oops has been printed for
1254 the specified number of seconds. This is to be used if
1255 your oopses keep scrolling off the screen.
1257 pcbit= [HW,ISDN]
1259 pcd. [PARIDE]
1260 See header of drivers/block/paride/pcd.c.
1261 See also Documentation/paride.txt.
1263 pci=option[,option...] [PCI] various PCI subsystem options:
1264 off [IA-32] don't probe for the PCI bus
1265 bios [IA-32] force use of PCI BIOS, don't access
1266 the hardware directly. Use this if your machine
1267 has a non-standard PCI host bridge.
1268 nobios [IA-32] disallow use of PCI BIOS, only direct
1269 hardware access methods are allowed. Use this
1270 if you experience crashes upon bootup and you
1271 suspect they are caused by the BIOS.
1272 conf1 [IA-32] Force use of PCI Configuration
1273 Mechanism 1.
1274 conf2 [IA-32] Force use of PCI Configuration
1275 Mechanism 2.
1276 nommconf [IA-32,X86_64] Disable use of MMCONFIG for PCI
1277 Configuration
1278 nomsi [MSI] If the PCI_MSI kernel config parameter is
1279 enabled, this kernel boot option can be used to
1280 disable the use of MSI interrupts system-wide.
1281 nosort [IA-32] Don't sort PCI devices according to
1282 order given by the PCI BIOS. This sorting is
1283 done to get a device order compatible with
1284 older kernels.
1285 biosirq [IA-32] Use PCI BIOS calls to get the interrupt
1286 routing table. These calls are known to be buggy
1287 on several machines and they hang the machine
1288 when used, but on other computers it's the only
1289 way to get the interrupt routing table. Try
1290 this option if the kernel is unable to allocate
1291 IRQs or discover secondary PCI buses on your
1292 motherboard.
1293 rom [IA-32] Assign address space to expansion ROMs.
1294 Use with caution as certain devices share
1295 address decoders between ROMs and other
1296 resources.
1297 irqmask=0xMMMM [IA-32] Set a bit mask of IRQs allowed to be
1298 assigned automatically to PCI devices. You can
1299 make the kernel exclude IRQs of your ISA cards
1300 this way.
1301 pirqaddr=0xAAAAA [IA-32] Specify the physical address
1302 of the PIRQ table (normally generated
1303 by the BIOS) if it is outside the
1304 F0000h-100000h range.
1305 lastbus=N [IA-32] Scan all buses thru bus #N. Can be
1306 useful if the kernel is unable to find your
1307 secondary buses and you want to tell it
1308 explicitly which ones they are.
1309 assign-busses [IA-32] Always assign all PCI bus
1310 numbers ourselves, overriding
1311 whatever the firmware may have done.
1312 usepirqmask [IA-32] Honor the possible IRQ mask stored
1313 in the BIOS $PIR table. This is needed on
1314 some systems with broken BIOSes, notably
1315 some HP Pavilion N5400 and Omnibook XE3
1316 notebooks. This will have no effect if ACPI
1317 IRQ routing is enabled.
1318 noacpi [IA-32] Do not use ACPI for IRQ routing
1319 or for PCI scanning.
1320 routeirq Do IRQ routing for all PCI devices.
1321 This is normally done in pci_enable_device(),
1322 so this option is a temporary workaround
1323 for broken drivers that don't call it.
1324 firmware [ARM] Do not re-enumerate the bus but instead
1325 just use the configuration from the
1326 bootloader. This is currently used on
1327 IXP2000 systems where the bus has to be
1328 configured a certain way for adjunct CPUs.
1329 noearly [X86] Don't do any early type 1 scanning.
1330 This might help on some broken boards which
1331 machine check when some devices' config space
1332 is read. But various workarounds are disabled
1333 and some IOMMU drivers will not work.
1334 bfsort Sort PCI devices into breadth-first order.
1335 This sorting is done to get a device
1336 order compatible with older (<= 2.4) kernels.
1337 nobfsort Don't sort PCI devices into breadth-first order.
1338 cbiosize=nn[KMG] The fixed amount of bus space which is
1339 reserved for the CardBus bridge's IO window.
1340 The default value is 256 bytes.
1341 cbmemsize=nn[KMG] The fixed amount of bus space which is
1342 reserved for the CardBus bridge's memory
1343 window. The default value is 64 megabytes.
1345 pcmv= [HW,PCMCIA] BadgePAD 4
1347 pd. [PARIDE]
1348 See Documentation/paride.txt.
1350 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1351 boot time.
1352 Format: { 0 | 1 }
1353 See arch/parisc/kernel/pdc_chassis.c
1355 pf. [PARIDE]
1356 See Documentation/paride.txt.
1358 pg. [PARIDE]
1359 See Documentation/paride.txt.
1361 pirq= [SMP,APIC] Manual mp-table setup
1362 See Documentation/i386/IO-APIC.txt.
1364 plip= [PPT,NET] Parallel port network link
1365 Format: { parport<nr> | timid | 0 }
1366 See also Documentation/parport.txt.
1368 pnpacpi= [ACPI]
1369 { off }
1371 pnpbios= [ISAPNP]
1372 { on | off | curr | res | no-curr | no-res }
1374 pnp_reserve_irq=
1375 [ISAPNP] Exclude IRQs for the autoconfiguration
1377 pnp_reserve_dma=
1378 [ISAPNP] Exclude DMAs for the autoconfiguration
1380 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1381 Ranges are in pairs (I/O port base and size).
1383 pnp_reserve_mem=
1384 [ISAPNP] Exclude memory regions for the
1385 autoconfiguration.
1386 Ranges are in pairs (memory base and size).
1388 profile= [KNL] Enable kernel profiling via /proc/profile
1389 Format: [schedule,]<number>
1390 Param: "schedule" - profile schedule points.
1391 Param: <number> - step/bucket size as a power of 2 for
1392 statistical time based profiling.
1393 Param: "sleep" - profile D-state sleeping (millisecs)
1395 processor.max_cstate= [HW,ACPI]
1396 Limit processor to maximum C-state
1397 max_cstate=9 overrides any DMI blacklist limit.
1399 processor.nocst [HW,ACPI]
1400 Ignore the _CST method to determine C-states,
1401 instead using the legacy FADT method
1403 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1404 before loading.
1405 See Documentation/ramdisk.txt.
1407 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1408 probe for; one of (bare|imps|exps|lifebook|any).
1409 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1410 per second.
1411 psmouse.resetafter= [HW,MOUSE]
1412 Try to reset the device after so many bad packets
1413 (0 = never).
1414 psmouse.resolution=
1415 [HW,MOUSE] Set desired mouse resolution, in dpi.
1416 psmouse.smartscroll=
1417 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1418 0 = disabled, 1 = enabled (default).
1420 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1421 Format:
1422 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1424 pt. [PARIDE]
1425 See Documentation/paride.txt.
1427 quiet [KNL] Disable most log messages
1429 r128= [HW,DRM]
1431 raid= [HW,RAID]
1432 See Documentation/md.txt.
1434 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1435 See Documentation/ramdisk.txt.
1437 ramdisk_blocksize= [RAM]
1438 See Documentation/ramdisk.txt.
1440 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1441 New name for the ramdisk parameter.
1442 See Documentation/ramdisk.txt.
1444 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1445 RCU callbacks to process in one batch.
1447 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1448 RCU callbacks over which batch limiting is disabled.
1450 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1451 RCU callbacks below which batch limiting is re-enabled.
1453 rdinit= [KNL]
1454 Format: <full_path>
1455 Run specified binary instead of /init from the ramdisk,
1456 used for early userspace startup. See initrd.
1458 reboot= [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1459 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1460 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1462 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1464 reservetop= [IA-32]
1465 Format: nn[KMG]
1466 Reserves a hole at the top of the kernel virtual
1467 address space.
1469 reset_devices [KNL] Force drivers to reset the underlying device
1470 during initialization.
1472 resume= [SWSUSP]
1473 Specify the partition device for software suspend
1475 resume_offset= [SWSUSP]
1476 Specify the offset from the beginning of the partition
1477 given by "resume=" at which the swap header is located,
1478 in <PAGE_SIZE> units (needed only for swap files).
1479 See Documentation/power/swsusp-and-swap-files.txt
1481 retain_initrd [RAM] Keep initrd memory after extraction
1483 rhash_entries= [KNL,NET]
1484 Set number of hash buckets for route cache
1486 riscom8= [HW,SERIAL]
1487 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1489 ro [KNL] Mount root device read-only on boot
1491 root= [KNL] Root filesystem
1493 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1494 mount the root filesystem
1496 rootflags= [KNL] Set root filesystem mount option string
1498 rootfstype= [KNL] Set root filesystem type
1500 rw [KNL] Mount root device read-write on boot
1502 S [KNL] Run init in single mode
1504 sa1100ir [NET]
1505 See drivers/net/irda/sa1100_ir.c.
1507 sb= [HW,OSS]
1508 Format: <io>,<irq>,<dma>,<dma2>
1510 sbni= [NET] Granch SBNI12 leased line adapter
1512 sbpcd= [HW,CD] Soundblaster CD adapter
1513 Format: <io>,<type>
1514 See a comment before function sbpcd_setup() in
1515 drivers/cdrom/sbpcd.c.
1517 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1518 Format: <io>[,<timeout>[,<isapnp>]]
1520 scsi_debug_*= [SCSI]
1521 See drivers/scsi/scsi_debug.c.
1523 scsi_default_dev_flags=
1524 [SCSI] SCSI default device flags
1525 Format: <integer>
1527 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1528 Format: <vendor>:<model>:<flags>
1529 (flags are integer value)
1531 scsi_logging= [SCSI]
1533 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1534 discovered. async scans them in kernel threads,
1535 allowing boot to proceed. none ignores them, expecting
1536 user space to do the scan.
1538 selinux [SELINUX] Disable or enable SELinux at boot time.
1539 Format: { "0" | "1" }
1540 See security/selinux/Kconfig help text.
1541 0 -- disable.
1542 1 -- enable.
1543 Default value is set via kernel config option.
1544 If enabled at boot time, /selinux/disable can be used
1545 later to disable prior to initial policy load.
1547 selinux_compat_net =
1548 [SELINUX] Set initial selinux_compat_net flag value.
1549 Format: { "0" | "1" }
1550 0 -- use new secmark-based packet controls
1551 1 -- use legacy packet controls
1552 Default value is 0 (preferred).
1553 Value can be changed at runtime via
1554 /selinux/compat_net.
1556 serialnumber [BUGS=IA-32]
1558 sg_def_reserved_size= [SCSI]
1560 shapers= [NET]
1561 Maximal number of shapers.
1563 sim710= [SCSI,HW]
1564 See header of drivers/scsi/sim710.c.
1566 simeth= [IA-64]
1567 simscsi=
1569 sjcd= [HW,CD]
1570 Format: <io>,<irq>,<dma>
1571 See header of drivers/cdrom/sjcd.c.
1573 slram= [HW,MTD]
1575 smart2= [HW]
1576 Format: <io1>[,<io2>[,...,<io8>]]
1578 smp-alt-once [IA-32,SMP] On a hotplug CPU system, only
1579 attempt to substitute SMP alternatives once at boot.
1581 snd-ad1816a= [HW,ALSA]
1583 snd-ad1848= [HW,ALSA]
1585 snd-ali5451= [HW,ALSA]
1587 snd-als100= [HW,ALSA]
1589 snd-als4000= [HW,ALSA]
1591 snd-azt2320= [HW,ALSA]
1593 snd-cmi8330= [HW,ALSA]
1595 snd-cmipci= [HW,ALSA]
1597 snd-cs4231= [HW,ALSA]
1599 snd-cs4232= [HW,ALSA]
1601 snd-cs4236= [HW,ALSA]
1603 snd-cs4281= [HW,ALSA]
1605 snd-cs46xx= [HW,ALSA]
1607 snd-dt019x= [HW,ALSA]
1609 snd-dummy= [HW,ALSA]
1611 snd-emu10k1= [HW,ALSA]
1613 snd-ens1370= [HW,ALSA]
1615 snd-ens1371= [HW,ALSA]
1617 snd-es968= [HW,ALSA]
1619 snd-es1688= [HW,ALSA]
1621 snd-es18xx= [HW,ALSA]
1623 snd-es1938= [HW,ALSA]
1625 snd-es1968= [HW,ALSA]
1627 snd-fm801= [HW,ALSA]
1629 snd-gusclassic= [HW,ALSA]
1631 snd-gusextreme= [HW,ALSA]
1633 snd-gusmax= [HW,ALSA]
1635 snd-hdsp= [HW,ALSA]
1637 snd-ice1712= [HW,ALSA]
1639 snd-intel8x0= [HW,ALSA]
1641 snd-interwave= [HW,ALSA]
1643 snd-interwave-stb=
1644 [HW,ALSA]
1646 snd-korg1212= [HW,ALSA]
1648 snd-maestro3= [HW,ALSA]
1650 snd-mpu401= [HW,ALSA]
1652 snd-mtpav= [HW,ALSA]
1654 snd-nm256= [HW,ALSA]
1656 snd-opl3sa2= [HW,ALSA]
1658 snd-opti92x-ad1848=
1659 [HW,ALSA]
1661 snd-opti92x-cs4231=
1662 [HW,ALSA]
1664 snd-opti93x= [HW,ALSA]
1666 snd-pmac= [HW,ALSA]
1668 snd-rme32= [HW,ALSA]
1670 snd-rme96= [HW,ALSA]
1672 snd-rme9652= [HW,ALSA]
1674 snd-sb8= [HW,ALSA]
1676 snd-sb16= [HW,ALSA]
1678 snd-sbawe= [HW,ALSA]
1680 snd-serial= [HW,ALSA]
1682 snd-sgalaxy= [HW,ALSA]
1684 snd-sonicvibes= [HW,ALSA]
1686 snd-sun-amd7930=
1687 [HW,ALSA]
1689 snd-sun-cs4231= [HW,ALSA]
1691 snd-trident= [HW,ALSA]
1693 snd-usb-audio= [HW,ALSA,USB]
1695 snd-via82xx= [HW,ALSA]
1697 snd-virmidi= [HW,ALSA]
1699 snd-wavefront= [HW,ALSA]
1701 snd-ymfpci= [HW,ALSA]
1703 sonycd535= [HW,CD]
1704 Format: <io>[,<irq>]
1706 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1707 See Documentation/sonypi.txt
1709 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1710 See Documentation/specialix.txt.
1712 spia_io_base= [HW,MTD]
1713 spia_fio_base=
1714 spia_pedr=
1715 spia_peddr=
1717 sscape= [HW,OSS]
1718 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1720 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1721 See Documentation/scsi/st.txt.
1723 st0x= [HW,SCSI]
1724 See header of drivers/scsi/seagate.c.
1726 sti= [PARISC,HW]
1727 Format: <num>
1728 Set the STI (builtin display/keyboard on the HP-PARISC
1729 machines) console (graphic card) which should be used
1730 as the initial boot-console.
1731 See also comment in drivers/video/console/sticore.c.
1733 sti_font= [HW]
1734 See comment in drivers/video/console/sticore.c.
1736 stifb= [HW]
1737 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1739 sunrpc.pool_mode=
1740 [NFS]
1741 Control how the NFS server code allocates CPUs to
1742 service thread pools. Depending on how many NICs
1743 you have and where their interrupts are bound, this
1744 option will affect which CPUs will do NFS serving.
1745 Note: this parameter cannot be changed while the
1746 NFS server is running.
1748 auto the server chooses an appropriate mode
1749 automatically using heuristics
1750 global a single global pool contains all CPUs
1751 percpu one pool for each CPU
1752 pernode one pool for each NUMA node (equivalent
1753 to global on non-NUMA machines)
1755 swiotlb= [IA-64] Number of I/O TLB slabs
1757 switches= [HW,M68k]
1759 sym53c416= [HW,SCSI]
1760 See header of drivers/scsi/sym53c416.c.
1762 sysrq_always_enabled
1763 [KNL]
1764 Ignore sysrq setting - this boot parameter will
1765 neutralize any effect of /proc/sys/kernel/sysrq.
1766 Useful for debugging.
1768 t128= [HW,SCSI]
1769 See header of drivers/scsi/t128.c.
1771 tdfx= [HW,DRM]
1773 thash_entries= [KNL,NET]
1774 Set number of hash buckets for TCP connection
1776 time Show timing data prefixed to each printk message line
1778 clocksource= [GENERIC_TIME] Override the default clocksource
1779 Override the default clocksource and use the clocksource
1780 with the name specified.
1782 tipar.timeout= [HW,PPT]
1783 Set communications timeout in tenths of a second
1784 (default 15).
1786 tipar.delay= [HW,PPT]
1787 Set inter-bit delay in microseconds (default 10).
1789 tmc8xx= [HW,SCSI]
1790 See header of drivers/scsi/seagate.c.
1792 tmscsim= [HW,SCSI]
1793 See comment before function dc390_setup() in
1794 drivers/scsi/tmscsim.c.
1796 tp720= [HW,PS2]
1798 trix= [HW,OSS] MediaTrix AudioTrix Pro
1799 Format:
1800 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1802 tsdev.xres= [TS] Horizontal screen resolution.
1803 tsdev.yres= [TS] Vertical screen resolution.
1805 turbografx.map[2|3]= [HW,JOY]
1806 TurboGraFX parallel port interface
1807 Format:
1808 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1809 See also Documentation/input/joystick-parport.txt
1811 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1812 See header of drivers/scsi/u14-34f.c.
1814 uart401= [HW,OSS]
1815 Format: <io>,<irq>
1817 uart6850= [HW,OSS]
1818 Format: <io>,<irq>
1820 uhci-hcd.ignore_oc=
1821 [USB] Ignore overcurrent events (default N).
1822 Some badly-designed motherboards generate lots of
1823 bogus events, for ports that aren't wired to
1824 anything. Set this parameter to avoid log spamming.
1825 Note that genuine overcurrent events won't be
1826 reported either.
1828 usbcore.autosuspend=
1829 [USB] The autosuspend time delay (in seconds) used
1830 for newly-detected USB devices (default 2). This
1831 is the time required before an idle device will be
1832 autosuspended. Devices for which the delay is set
1833 to a negative value won't be autosuspended at all.
1835 usbhid.mousepoll=
1836 [USBHID] The interval which mice are to be polled at.
1838 vdso= [IA-32,SH]
1839 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1840 vdso=1: enable VDSO (default)
1841 vdso=0: disable VDSO mapping
1843 video= [FB] Frame buffer configuration
1844 See Documentation/fb/modedb.txt.
1846 vga= [BOOT,IA-32] Select a particular video mode
1847 See Documentation/i386/boot.txt and
1848 Documentation/svga.txt.
1849 Use vga=ask for menu.
1850 This is actually a boot loader parameter; the value is
1851 passed to the kernel using a special protocol.
1853 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1854 size of <nn>. This can be used to increase the
1855 minimum size (128MB on x86). It can also be used to
1856 decrease the size and leave more room for directly
1857 mapped kernel RAM.
1859 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1860 Format: <command>
1862 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1863 Format: <command>
1865 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1866 Format: <command>
1868 waveartist= [HW,OSS]
1869 Format: <io>,<irq>,<dma>,<dma2>
1871 wd33c93= [HW,SCSI]
1872 See header of drivers/scsi/wd33c93.c.
1874 wd7000= [HW,SCSI]
1875 See header of drivers/scsi/wd7000.c.
1877 wdt= [WDT] Watchdog
1878 See Documentation/watchdog/watchdog.txt.
1880 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1881 xd_geo= See header of drivers/block/xd.c.
1883 xirc2ps_cs= [NET,PCMCIA]
1884 Format:
1885 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1887 norandmaps Don't use address space randomization
1888 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1890 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1891 This is useful to get more information why
1892 you got a "dwarf2 unwinder stuck"
1894 ______________________________________________________________________
1896 TODO:
1898 Add documentation for ALSA options.
1899 Add more DRM drivers.