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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AX25 Appropriate AX.25 support is enabled.
38 DRM Direct Rendering Management support is enabled.
39 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
40 EFI EFI Partitioning (GPT) is enabled
41 EIDE EIDE/ATAPI support is enabled.
42 FB The frame buffer device is enabled.
43 HW Appropriate hardware is enabled.
44 IA-64 IA-64 architecture is enabled.
45 IOSCHED More than one I/O scheduler is enabled.
46 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
47 ISAPNP ISA PnP code is enabled.
48 ISDN Appropriate ISDN support is enabled.
49 JOY Appropriate joystick support is enabled.
50 LIBATA Libata driver is enabled
51 LP Printer support is enabled.
52 LOOP Loopback device support is enabled.
53 M68k M68k architecture is enabled.
54 These options have more detailed description inside of
55 Documentation/m68k/kernel-options.txt.
56 MCA MCA bus support is enabled.
57 MDA MDA console support is enabled.
58 MOUSE Appropriate mouse support is enabled.
59 MSI Message Signaled Interrupts (PCI).
60 MTD MTD (Memory Technology Device) support is enabled.
61 NET Appropriate network support is enabled.
62 NUMA NUMA support is enabled.
63 GENERIC_TIME The generic timeofday code is enabled.
64 NFS Appropriate NFS support is enabled.
65 OSS OSS sound support is enabled.
66 PV_OPS A paravirtualized kernel is enabled.
67 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
68 PARISC The PA-RISC architecture is enabled.
69 PCI PCI bus support is enabled.
70 PCMCIA The PCMCIA subsystem is enabled.
71 PNP Plug & Play support is enabled.
72 PPC PowerPC architecture is enabled.
73 PPT Parallel port support is enabled.
74 PS2 Appropriate PS/2 support is enabled.
75 RAM RAM disk support is enabled.
76 S390 S390 architecture is enabled.
77 SCSI Appropriate SCSI support is enabled.
78 A lot of drivers has their options described inside of
79 Documentation/scsi/.
80 SELINUX SELinux support is enabled.
81 SERIAL Serial support is enabled.
82 SH SuperH architecture is enabled.
83 SMP The kernel is an SMP kernel.
84 SPARC Sparc architecture is enabled.
85 SWSUSP Software suspend is enabled.
86 TS Appropriate touchscreen support is enabled.
87 USB USB support is enabled.
88 USBHID USB Human Interface Device support is enabled.
89 V4L Video For Linux support is enabled.
90 VGA The VGA console has been enabled.
91 VT Virtual terminal support is enabled.
92 WDT Watchdog support is enabled.
93 XT IBM PC/XT MFM hard disk support is enabled.
94 X86-32 X86-32, aka i386 architecture is enabled.
95 X86-64 X86-64 architecture is enabled.
96 More X86-64 boot options can be found in
97 Documentation/x86_64/boot-options.txt .
99 In addition, the following text indicates that the option:
101 BUGS= Relates to possible processor bugs on the said processor.
102 KNL Is a kernel start-up parameter.
103 BOOT Is a boot loader parameter.
105 Parameters denoted with BOOT are actually interpreted by the boot
106 loader, and have no meaning to the kernel directly.
107 Do not modify the syntax of boot loader parameters without extreme
108 need or coordination with <Documentation/i386/boot.txt>.
110 There are also arch-specific kernel-parameters not documented here.
111 See for example <Documentation/x86_64/boot-options.txt>.
113 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
114 a trailing = on the name of any parameter states that that parameter will
115 be entered as an environment variable, whereas its absence indicates that
116 it will appear as a kernel argument readable via /proc/cmdline by programs
117 running once the system is up.
119 The number of kernel parameters is not limited, but the length of the
120 complete command line (parameters including spaces etc.) is limited to
121 a fixed number of characters. This limit depends on the architecture
122 and is between 256 and 4096 characters. It is defined in the file
123 ./include/asm/setup.h as COMMAND_LINE_SIZE.
126 acpi= [HW,ACPI,X86-64,i386]
127 Advanced Configuration and Power Interface
128 Format: { force | off | ht | strict | noirq }
129 force -- enable ACPI if default was off
130 off -- disable ACPI if default was on
131 noirq -- do not use ACPI for IRQ routing
132 ht -- run only enough ACPI to enable Hyper Threading
133 strict -- Be less tolerant of platforms that are not
134 strictly ACPI specification compliant.
136 See also Documentation/pm.txt, pci=noacpi
138 acpi_apic_instance= [ACPI, IOAPIC]
139 Format: <int>
140 2: use 2nd APIC table, if available
141 1,0: use 1st APIC table
142 default: 0
144 acpi_sleep= [HW,ACPI] Sleep options
145 Format: { s3_bios, s3_mode }
146 See Documentation/power/video.txt
148 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
149 Format: { level | edge | high | low }
151 acpi_irq_balance [HW,ACPI]
152 ACPI will balance active IRQs
153 default in APIC mode
155 acpi_irq_nobalance [HW,ACPI]
156 ACPI will not move active IRQs (default)
157 default in PIC mode
159 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
160 use by PCI
161 Format: <irq>,<irq>...
163 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
164 Format: <irq>,<irq>...
166 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
168 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
169 Format: To spoof as Windows 98: ="Microsoft Windows"
171 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
172 acpi_osi="string1" # add string1 -- only one string
173 acpi_osi="!string2" # remove built-in string2
174 acpi_osi= # disable all strings
176 acpi_serialize [HW,ACPI] force serialization of AML methods
178 acpi_skip_timer_override [HW,ACPI]
179 Recognize and ignore IRQ0/pin2 Interrupt Override.
180 For broken nForce2 BIOS resulting in XT-PIC timer.
181 acpi_use_timer_override [HW,ACPI}
182 Use timer override. For some broken Nvidia NF5 boards
183 that require a timer override, but don't have
184 HPET
186 acpi.debug_layer= [HW,ACPI]
187 Format: <int>
188 Each bit of the <int> indicates an ACPI debug layer,
189 1: enable, 0: disable. It is useful for boot time
190 debugging. After system has booted up, it can be set
191 via /sys/module/acpi/parameters/debug_layer.
192 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
193 Available bits (add the numbers together) to enable debug output
194 for specific parts of the ACPI subsystem:
195 0x01 utilities 0x02 hardware 0x04 events 0x08 tables
196 0x10 namespace 0x20 parser 0x40 dispatcher
197 0x80 executer 0x100 resources 0x200 acpica debugger
198 0x400 os services 0x800 acpica disassembler.
199 The number can be in decimal or prefixed with 0x in hex.
200 Warning: Many of these options can produce a lot of
201 output and make your system unusable. Be very careful.
203 acpi.debug_level= [HW,ACPI]
204 Format: <int>
205 Each bit of the <int> indicates an ACPI debug level,
206 1: enable, 0: disable. It is useful for boot time
207 debugging. After system has booted up, it can be set
208 via /sys/module/acpi/parameters/debug_level.
209 CONFIG_ACPI_DEBUG must be enabled for this to produce any output.
210 Available bits (add the numbers together) to enable different
211 debug output levels of the ACPI subsystem:
212 0x01 error 0x02 warn 0x04 init 0x08 debug object
213 0x10 info 0x20 init names 0x40 parse 0x80 load
214 0x100 dispatch 0x200 execute 0x400 names 0x800 operation region
215 0x1000 bfield 0x2000 tables 0x4000 values 0x8000 objects
216 0x10000 resources 0x20000 user requests 0x40000 package.
217 The number can be in decimal or prefixed with 0x in hex.
218 Warning: Many of these options can produce a lot of
219 output and make your system unusable. Be very careful.
222 acpi_fake_ecdt [HW,ACPI] Workaround failure due to BIOS lacking ECDT
224 acpi_pm_good [X86-32,X86-64]
225 Override the pmtimer bug detection: force the kernel
226 to assume that this machine's pmtimer latches its value
227 and always returns good values.
229 agp= [AGP]
230 { off | try_unsupported }
231 off: disable AGP support
232 try_unsupported: try to drive unsupported chipsets
233 (may crash computer or cause data corruption)
235 enable_timer_pin_1 [i386,x86-64]
236 Enable PIN 1 of APIC timer
237 Can be useful to work around chipset bugs
238 (in particular on some ATI chipsets).
239 The kernel tries to set a reasonable default.
241 disable_timer_pin_1 [i386,x86-64]
242 Disable PIN 1 of APIC timer
243 Can be useful to work around chipset bugs.
245 ad1848= [HW,OSS]
246 Format: <io>,<irq>,<dma>,<dma2>,<type>
248 advansys= [HW,SCSI]
249 See header of drivers/scsi/advansys.c.
251 advwdt= [HW,WDT] Advantech WDT
252 Format: <iostart>,<iostop>
254 aedsp16= [HW,OSS] Audio Excel DSP 16
255 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
256 See also header of sound/oss/aedsp16.c.
258 aha152x= [HW,SCSI]
259 See Documentation/scsi/aha152x.txt.
261 aha1542= [HW,SCSI]
262 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
264 aic7xxx= [HW,SCSI]
265 See Documentation/scsi/aic7xxx.txt.
267 aic79xx= [HW,SCSI]
268 See Documentation/scsi/aic79xx.txt.
270 amijoy.map= [HW,JOY] Amiga joystick support
271 Map of devices attached to JOY0DAT and JOY1DAT
272 Format: <a>,<b>
273 See also Documentation/kernel/input/joystick.txt
275 analog.map= [HW,JOY] Analog joystick and gamepad support
276 Specifies type or capabilities of an analog joystick
277 connected to one of 16 gameports
278 Format: <type1>,<type2>,..<type16>
280 apc= [HW,SPARC]
281 Power management functions (SPARCstation-4/5 + deriv.)
282 Format: noidle
283 Disable APC CPU standby support. SPARCstation-Fox does
284 not play well with APC CPU idle - disable it if you have
285 APC and your system crashes randomly.
287 apic= [APIC,i386] Advanced Programmable Interrupt Controller
288 Change the output verbosity whilst booting
289 Format: { quiet (default) | verbose | debug }
290 Change the amount of debugging information output
291 when initialising the APIC and IO-APIC components.
293 apm= [APM] Advanced Power Management
294 See header of arch/i386/kernel/apm.c.
296 applicom= [HW]
297 Format: <mem>,<irq>
299 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
300 Format: <io>,<irq>,<nodeID>
302 ataflop= [HW,M68k]
304 atarimouse= [HW,MOUSE] Atari Mouse
306 atascsi= [HW,SCSI] Atari SCSI
308 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
309 EzKey and similar keyboards
311 atkbd.reset= [HW] Reset keyboard during initialization
313 atkbd.set= [HW] Select keyboard code set
314 Format: <int> (2 = AT (default), 3 = PS/2)
316 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
317 keyboards
319 atkbd.softraw= [HW] Choose between synthetic and real raw mode
320 Format: <bool> (0 = real, 1 = synthetic (default))
322 atkbd.softrepeat= [HW]
323 Use software keyboard repeat
325 autotest [IA64]
327 baycom_epp= [HW,AX25]
328 Format: <io>,<mode>
330 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
331 Format: <io>,<mode>
332 See header of drivers/net/hamradio/baycom_par.c.
334 baycom_ser_fdx= [HW,AX25]
335 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
336 Format: <io>,<irq>,<mode>[,<baud>]
337 See header of drivers/net/hamradio/baycom_ser_fdx.c.
339 baycom_ser_hdx= [HW,AX25]
340 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
341 Format: <io>,<irq>,<mode>
342 See header of drivers/net/hamradio/baycom_ser_hdx.c.
344 blkmtd_device= [HW,MTD]
345 blkmtd_erasesz=
346 blkmtd_ro=
347 blkmtd_bs=
348 blkmtd_count=
350 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
351 bttv.radio= Most important insmod options are available as
352 kernel args too.
353 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
354 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
356 BusLogic= [HW,SCSI]
357 See drivers/scsi/BusLogic.c, comment before function
358 BusLogic_ParseDriverOptions().
360 c101= [NET] Moxa C101 synchronous serial card
362 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
363 Sometimes CPU hardware bugs make them report the cache
364 size incorrectly. The kernel will attempt work arounds
365 to fix known problems, but for some CPUs it is not
366 possible to determine what the correct size should be.
367 This option provides an override for these situations.
369 chandev= [HW,NET] Generic channel device initialisation
371 checkreqprot [SELINUX] Set initial checkreqprot flag value.
372 Format: { "0" | "1" }
373 See security/selinux/Kconfig help text.
374 0 -- check protection applied by kernel (includes
375 any implied execute protection).
376 1 -- check protection requested by application.
377 Default value is set via a kernel config option.
378 Value can be changed at runtime via
379 /selinux/checkreqprot.
381 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
382 [Deprecated]
383 Forces specified clocksource (if available) to be used
384 when calculating gettimeofday(). If specified
385 clocksource is not available, it defaults to PIT.
386 Format: { pit | tsc | cyclone | pmtmr }
388 clocksource= [GENERIC_TIME] Override the default clocksource
389 Format: <string>
390 Override the default clocksource and use the clocksource
391 with the name specified.
392 Some clocksource names to choose from, depending on
393 the platform:
394 [all] jiffies (this is the base, fallback clocksource)
395 [ACPI] acpi_pm
396 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
397 pxa_timer,timer3,32k_counter,timer0_1
398 [AVR32] avr32
399 [X86-32] pit,hpet,tsc,vmi-timer;
400 scx200_hrt on Geode; cyclone on IBM x440
401 [MIPS] MIPS
402 [PARISC] cr16
403 [S390] tod
404 [SH] SuperH
405 [SPARC64] tick
406 [X86-64] hpet,tsc
408 code_bytes [IA32] How many bytes of object code to print in an
409 oops report.
410 Range: 0 - 8192
411 Default: 64
413 disable_8254_timer
414 enable_8254_timer
415 [IA32/X86_64] Disable/Enable interrupt 0 timer routing
416 over the 8254 in addition to over the IO-APIC. The
417 kernel tries to set a sensible default.
419 hpet= [X86-32,HPET] option to disable HPET and use PIT.
420 Format: disable
422 com20020= [HW,NET] ARCnet - COM20020 chipset
423 Format:
424 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
426 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
427 Format: <io>[,<irq>]
429 com90xx= [HW,NET]
430 ARCnet - COM90xx chipset (memory-mapped buffers)
431 Format: <io>[,<irq>[,<memstart>]]
433 condev= [HW,S390] console device
434 conmode=
436 console= [KNL] Output console device and options.
438 tty<n> Use the virtual console device <n>.
440 ttyS<n>[,options]
441 ttyUSB0[,options]
442 Use the specified serial port. The options are of
443 the form "bbbbpnf", where "bbbb" is the baud rate,
444 "p" is parity ("n", "o", or "e"), "n" is number of
445 bits, and "f" is flow control ("r" for RTS or
446 omit it). Default is "9600n8".
448 See Documentation/serial-console.txt for more
449 information. See
450 Documentation/networking/netconsole.txt for an
451 alternative.
453 uart[8250],io,<addr>[,options]
454 uart[8250],mmio,<addr>[,options]
455 Start an early, polled-mode console on the 8250/16550
456 UART at the specified I/O port or MMIO address,
457 switching to the matching ttyS device later. The
458 options are the same as for ttyS, above.
460 earlycon= [KNL] Output early console device and options.
461 uart[8250],io,<addr>[,options]
462 uart[8250],mmio,<addr>[,options]
463 Start an early, polled-mode console on the 8250/16550
464 UART at the specified I/O port or MMIO address.
465 The options are the same as for ttyS, above.
467 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
468 Format:
469 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
471 cpia_pp= [HW,PPT]
472 Format: { parport<nr> | auto | none }
474 crashkernel=nn[KMG]@ss[KMG]
475 [KNL] Reserve a chunk of physical memory to
476 hold a kernel to switch to with kexec on panic.
478 cs4232= [HW,OSS]
479 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
481 cs89x0_dma= [HW,NET]
482 Format: <dma>
484 cs89x0_media= [HW,NET]
485 Format: { rj45 | aui | bnc }
487 cyclades= [HW,SERIAL] Cyclades multi-serial port adapter.
489 dasd= [HW,NET]
490 See header of drivers/s390/block/dasd_devmap.c.
492 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
493 (one device per port)
494 Format: <port#>,<type>
495 See also Documentation/input/joystick-parport.txt
497 debug [KNL] Enable kernel debugging (events log level).
499 debug_locks_verbose=
500 [KNL] verbose self-tests
501 Format=<0|1>
502 Print debugging info while doing the locking API
503 self-tests.
504 We default to 0 (no extra messages), setting it to
505 1 will print _a lot_ more information - normally
506 only useful to kernel developers.
508 decnet= [HW,NET]
509 Format: <area>[,<node>]
510 See also Documentation/networking/decnet.txt.
512 default_blu= [VT]
513 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
514 Change the default blue palette of the console.
515 This is a 16-member array composed of values
516 ranging from 0-255.
518 default_grn= [VT]
519 Format: <green0>,<green1>,<green2>,...,<green15>
520 Change the default green palette of the console.
521 This is a 16-member array composed of values
522 ranging from 0-255.
524 default_red= [VT]
525 Format: <red0>,<red1>,<red2>,...,<red15>
526 Change the default red palette of the console.
527 This is a 16-member array composed of values
528 ranging from 0-255.
530 default_utf8= [VT]
531 Format=<0|1>
532 Set system-wide default UTF-8 mode for all tty's.
533 Default is 0 and by setting to 1, it enables UTF-8
534 mode for all newly opened or allocated terminals.
536 dhash_entries= [KNL]
537 Set number of hash buckets for dentry cache.
539 digi= [HW,SERIAL]
540 IO parameters + enable/disable command.
542 digiepca= [HW,SERIAL]
543 See drivers/char/README.epca and
544 Documentation/digiepca.txt.
546 dmascc= [HW,AX25,SERIAL] AX.25 Z80SCC driver with DMA
547 support available.
548 Format: <io_dev0>[,<io_dev1>[,..<io_dev32>]]
550 dmasound= [HW,OSS] Sound subsystem buffers
552 dscc4.setup= [NET]
554 dtc3181e= [HW,SCSI]
556 earlyprintk= [X86-32,X86-64,SH]
557 earlyprintk=vga
558 earlyprintk=serial[,ttySn[,baudrate]]
560 Append ",keep" to not disable it when the real console
561 takes over.
563 Only vga or serial at a time, not both.
565 Currently only ttyS0 and ttyS1 are supported.
567 Interaction with the standard serial driver is not
568 very good.
570 The VGA output is eventually overwritten by the real
571 console.
573 eata= [HW,SCSI]
575 ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
576 Format: <int>
577 0: polling mode
578 non-0: interrupt mode (default)
580 eda= [HW,PS2]
582 edb= [HW,PS2]
584 edd= [EDD]
585 Format: {"of[f]" | "sk[ipmbr]"}
586 See comment in arch/i386/boot/edd.S
588 eicon= [HW,ISDN]
589 Format: <id>,<membase>,<irq>
591 eisa_irq_edge= [PARISC,HW]
592 See header of drivers/parisc/eisa.c.
594 elanfreq= [X86-32]
595 See comment before function elanfreq_setup() in
596 arch/i386/kernel/cpu/cpufreq/elanfreq.c.
598 elevator= [IOSCHED]
599 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
600 See Documentation/block/as-iosched.txt and
601 Documentation/block/deadline-iosched.txt for details.
603 elfcorehdr= [X86-32, X86_64]
604 Specifies physical address of start of kernel core
605 image elf header. Generally kexec loader will
606 pass this option to capture kernel.
607 See Documentation/kdump/kdump.txt for details.
609 enforcing [SELINUX] Set initial enforcing status.
610 Format: {"0" | "1"}
611 See security/selinux/Kconfig help text.
612 0 -- permissive (log only, no denials).
613 1 -- enforcing (deny and log).
614 Default value is 0.
615 Value can be changed at runtime via /selinux/enforce.
617 es1371= [HW,OSS]
618 Format: <spdif>,[<nomix>,[<amplifier>]]
619 See also header of sound/oss/es1371.c.
621 ether= [HW,NET] Ethernet cards parameters
622 This option is obsoleted by the "netdev=" option, which
623 has equivalent usage. See its documentation for details.
625 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
626 Format: <io>[,<irq>]
628 failslab=
629 fail_page_alloc=
630 fail_make_request=[KNL]
631 General fault injection mechanism.
632 Format: <interval>,<probability>,<space>,<times>
633 See also /Documentation/fault-injection/.
635 fd_mcs= [HW,SCSI]
636 See header of drivers/scsi/fd_mcs.c.
638 fdomain= [HW,SCSI]
639 See header of drivers/scsi/fdomain.c.
641 floppy= [HW]
642 See Documentation/floppy.txt.
644 gamecon.map[2|3]=
645 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
646 support via parallel port (up to 5 devices per port)
647 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
648 See also Documentation/input/joystick-parport.txt
650 gamma= [HW,DRM]
652 gdth= [HW,SCSI]
653 See header of drivers/scsi/gdth.c.
655 gpt [EFI] Forces disk with valid GPT signature but
656 invalid Protective MBR to be treated as GPT.
658 gvp11= [HW,SCSI]
660 hashdist= [KNL,NUMA] Large hashes allocated during boot
661 are distributed across NUMA nodes. Defaults on
662 for IA-64, off otherwise.
663 Format: 0 | 1 (for off | on)
665 hcl= [IA-64] SGI's Hardware Graph compatibility layer
667 hd= [EIDE] (E)IDE hard drive subsystem geometry
668 Format: <cyl>,<head>,<sect>
670 hd?= [HW] (E)IDE subsystem
671 hd?lun= See Documentation/ide.txt.
673 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
674 size of <nn>. This works even on boxes that have no
675 highmem otherwise. This also works to reduce highmem
676 size on bigger boxes.
678 highres= [KNL] Enable/disable high resolution timer mode.
679 Valid parameters: "on", "off"
680 Default: "on"
682 hisax= [HW,ISDN]
683 See Documentation/isdn/README.HiSax.
685 hugepages= [HW,X86-32,IA-64] Maximal number of HugeTLB pages.
687 i8042.direct [HW] Put keyboard port into non-translated mode
688 i8042.dumbkbd [HW] Pretend that controller can only read data from
689 keyboard and cannot control its state
690 (Don't attempt to blink the leds)
691 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
692 i8042.nokbd [HW] Don't check/create keyboard port
693 i8042.nomux [HW] Don't check presence of an active multiplexing
694 controller
695 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
696 controllers
697 i8042.panicblink=
698 [HW] Frequency with which keyboard LEDs should blink
699 when kernel panics (default is 0.5 sec)
700 i8042.reset [HW] Reset the controller during init and cleanup
701 i8042.unlock [HW] Unlock (ignore) the keylock
703 i810= [HW,DRM]
705 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
706 indicates that the driver is running on unsupported
707 hardware.
708 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
709 does not match list of supported models.
710 i8k.power_status
711 [HW] Report power status in /proc/i8k
712 (disabled by default)
713 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
714 capability is set.
716 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
717 See Documentation/mca.txt.
719 icn= [HW,ISDN]
720 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
722 ide= [HW] (E)IDE subsystem
723 Format: ide=nodma or ide=doubler or ide=reverse
724 See Documentation/ide.txt.
726 ide?= [HW] (E)IDE subsystem
727 Format: ide?=noprobe or chipset specific parameters.
728 See Documentation/ide.txt.
730 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
731 See Documentation/ide.txt.
733 idle= [X86]
734 Format: idle=poll or idle=mwait
735 Poll forces a polling idle loop that can slightly improves the performance
736 of waking up a idle CPU, but will use a lot of power and make the system
737 run hot. Not recommended.
738 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
739 to not use it because it doesn't save as much power as a normal idle
740 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
741 as idle=poll.
743 ignore_loglevel [KNL]
744 Ignore loglevel setting - this will print /all/
745 kernel messages to the console. Useful for debugging.
747 ihash_entries= [KNL]
748 Set number of hash buckets for inode cache.
750 in2000= [HW,SCSI]
751 See header of drivers/scsi/in2000.c.
753 init= [KNL]
754 Format: <full_path>
755 Run specified binary instead of /sbin/init as init
756 process.
758 initcall_debug [KNL] Trace initcalls as they are executed. Useful
759 for working out where the kernel is dying during
760 startup.
762 initrd= [BOOT] Specify the location of the initial ramdisk
764 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
765 Format: <irq>
767 inttest= [IA64]
769 io7= [HW] IO7 for Marvel based alpha systems
770 See comment before marvel_specify_io7 in
771 arch/alpha/kernel/core_marvel.c.
773 ip= [IP_PNP]
774 See Documentation/nfsroot.txt.
776 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
777 See comment before ip2_setup() in
778 drivers/char/ip2/ip2base.c.
780 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
781 See header of drivers/scsi/ips.c.
783 ports= [IP_VS_FTP] IPVS ftp helper module
784 Default is 21.
785 Up to 8 (IP_VS_APP_MAX_PORTS) ports
786 may be specified.
787 Format: <port>,<port>....
789 irqfixup [HW]
790 When an interrupt is not handled search all handlers
791 for it. Intended to get systems with badly broken
792 firmware running.
794 irqpoll [HW]
795 When an interrupt is not handled search all handlers
796 for it. Also check all handlers each timer
797 interrupt. Intended to get systems with badly broken
798 firmware running.
800 isapnp= [ISAPNP]
801 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
803 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
804 Format:
805 <cpu number>,...,<cpu number>
806 or
807 <cpu number>-<cpu number> (must be a positive range in ascending order)
808 or a mixture
809 <cpu number>,...,<cpu number>-<cpu number>
810 This option can be used to specify one or more CPUs
811 to isolate from the general SMP balancing and scheduling
812 algorithms. The only way to move a process onto or off
813 an "isolated" CPU is via the CPU affinity syscalls.
814 <cpu number> begins at 0 and the maximum value is
815 "number of CPUs in system - 1".
817 This option is the preferred way to isolate CPUs. The
818 alternative -- manually setting the CPU mask of all
819 tasks in the system -- can cause problems and
820 suboptimal load balancer performance.
822 iucv= [HW,NET]
824 js= [HW,JOY] Analog joystick
825 See Documentation/input/joystick.txt.
827 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
828 specifies the amount of memory usable by the kernel
829 for non-movable allocations. The requested amount is
830 spread evenly throughout all nodes in the system. The
831 remaining memory in each node is used for Movable
832 pages. In the event, a node is too small to have both
833 kernelcore and Movable pages, kernelcore pages will
834 take priority and other nodes will have a larger number
835 of kernelcore pages. The Movable zone is used for the
836 allocation of pages that may be reclaimed or moved
837 by the page migration subsystem. This means that
838 HugeTLB pages may not be allocated from this zone.
839 Note that allocations like PTEs-from-HighMem still
840 use the HighMem zone if it exists, and the Normal
841 zone if it does not.
843 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
844 is similar to kernelcore except it specifies the
845 amount of memory used for migratable allocations.
846 If both kernelcore and movablecore is specified,
847 then kernelcore will be at *least* the specified
848 value but may be more. If movablecore on its own
849 is specified, the administrator must be careful
850 that the amount of memory usable for all allocations
851 is not too small.
853 keepinitrd [HW,ARM]
855 kstack=N [X86-32,X86-64] Print N words from the kernel stack
856 in oops dumps.
858 l2cr= [PPC]
860 lapic [X86-32,APIC] Enable the local APIC even if BIOS
861 disabled it.
863 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
864 C2 power state.
866 lasi= [HW,SCSI] PARISC LASI driver for the 53c700 chip
867 Format: addr:<io>,irq:<irq>
869 load_ramdisk= [RAM] List of ramdisks to load from floppy
870 See Documentation/ramdisk.txt.
872 lockd.nlm_grace_period=P [NFS] Assign grace period.
873 Format: <integer>
875 lockd.nlm_tcpport=N [NFS] Assign TCP port.
876 Format: <integer>
878 lockd.nlm_timeout=T [NFS] Assign timeout value.
879 Format: <integer>
881 lockd.nlm_udpport=M [NFS] Assign UDP port.
882 Format: <integer>
884 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
885 Format: <irq>
887 loglevel= All Kernel Messages with a loglevel smaller than the
888 console loglevel will be printed to the console. It can
889 also be changed with klogd or other programs. The
890 loglevels are defined as follows:
892 0 (KERN_EMERG) system is unusable
893 1 (KERN_ALERT) action must be taken immediately
894 2 (KERN_CRIT) critical conditions
895 3 (KERN_ERR) error conditions
896 4 (KERN_WARNING) warning conditions
897 5 (KERN_NOTICE) normal but significant condition
898 6 (KERN_INFO) informational
899 7 (KERN_DEBUG) debug-level messages
901 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
902 Format: { n | nk | nM }
903 n must be a power of two. The default size
904 is set in the kernel config file.
906 lp=0 [LP] Specify parallel ports to use, e.g,
907 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
908 lp=reset first parallel port). 'lp=0' disables the
909 lp=auto printer driver. 'lp=reset' (which can be
910 specified in addition to the ports) causes
911 attached printers to be reset. Using
912 lp=port1,port2,... specifies the parallel ports
913 to associate lp devices with, starting with
914 lp0. A port specification may be 'none' to skip
915 that lp device, or a parport name such as
916 'parport0'. Specifying 'lp=auto' instead of a
917 port specification list means that device IDs
918 from each port should be examined, to see if
919 an IEEE 1284-compliant printer is attached; if
920 so, the driver will manage that printer.
921 See also header of drivers/char/lp.c.
923 lpj=n [KNL]
924 Sets loops_per_jiffy to given constant, thus avoiding
925 time-consuming boot-time autodetection (up to 250 ms per
926 CPU). 0 enables autodetection (default). To determine
927 the correct value for your kernel, boot with normal
928 autodetection and see what value is printed. Note that
929 on SMP systems the preset will be applied to all CPUs,
930 which is likely to cause problems if your CPUs need
931 significantly divergent settings. An incorrect value
932 will cause delays in the kernel to be wrong, leading to
933 unpredictable I/O errors and other breakage. Although
934 unlikely, in the extreme case this might damage your
935 hardware.
937 ltpc= [NET]
938 Format: <io>,<irq>,<dma>
940 mac5380= [HW,SCSI] Format:
941 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
943 mac53c9x= [HW,SCSI] Format:
944 <num_esps>,<disconnect>,<nosync>,<can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
946 machvec= [IA64] Force the use of a particular machine-vector
947 (machvec) in a generic kernel.
948 Example: machvec=hpzx1_swiotlb
950 max_loop= [LOOP] Maximum number of loopback devices that can
951 be mounted
952 Format: <1-256>
954 maxcpus= [SMP] Maximum number of processors that an SMP kernel
955 should make use of.
956 Using "nosmp" or "maxcpus=0" will disable SMP
957 entirely (the MPS table probe still happens, though).
958 A command-line option of "maxcpus=<NUM>", where <NUM>
959 is an integer greater than 0, limits the maximum number
960 of CPUs activated in SMP mode to <NUM>.
961 Using "maxcpus=1" on an SMP kernel is the trivial
962 case of an SMP kernel with only one CPU.
964 max_addr=[KMG] [KNL,BOOT,ia64] All physical memory greater than or
965 equal to this physical address is ignored.
967 max_luns= [SCSI] Maximum number of LUNs to probe.
968 Should be between 1 and 2^32-1.
970 max_report_luns=
971 [SCSI] Maximum number of LUNs received.
972 Should be between 1 and 16384.
974 mca-pentium [BUGS=X86-32]
976 mcatest= [IA-64]
978 mce [X86-32] Machine Check Exception
980 md= [HW] RAID subsystems devices and level
981 See Documentation/md.txt.
983 mdacon= [MDA]
984 Format: <first>,<last>
985 Specifies range of consoles to be captured by the MDA.
987 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
988 Amount of memory to be used when the kernel is not able
989 to see the whole system memory or for test.
990 [X86-32] Use together with memmap= to avoid physical
991 address space collisions. Without memmap= PCI devices
992 could be placed at addresses belonging to unused RAM.
994 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
995 memory.
997 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
998 E820 memory map, as specified by the user.
999 Such memmap=exactmap lines can be constructed based on
1000 BIOS output or other requirements. See the memmap=nn@ss
1001 option description.
1003 memmap=nn[KMG]@ss[KMG]
1004 [KNL] Force usage of a specific region of memory
1005 Region of memory to be used, from ss to ss+nn.
1007 memmap=nn[KMG]#ss[KMG]
1008 [KNL,ACPI] Mark specific memory as ACPI data.
1009 Region of memory to be used, from ss to ss+nn.
1011 memmap=nn[KMG]$ss[KMG]
1012 [KNL,ACPI] Mark specific memory as reserved.
1013 Region of memory to be used, from ss to ss+nn.
1015 meye.*= [HW] Set MotionEye Camera parameters
1016 See Documentation/video4linux/meye.txt.
1018 mga= [HW,DRM]
1020 mousedev.tap_time=
1021 [MOUSE] Maximum time between finger touching and
1022 leaving touchpad surface for touch to be considered
1023 a tap and be reported as a left button click (for
1024 touchpads working in absolute mode only).
1025 Format: <msecs>
1026 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1027 reporting absolute coordinates, such as tablets
1028 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1029 reporting absolute coordinates, such as tablets
1031 mpu401= [HW,OSS]
1032 Format: <io>,<irq>
1034 MTD_Partition= [MTD]
1035 Format: <name>,<region-number>,<size>,<offset>
1037 MTD_Region= [MTD] Format:
1038 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1040 mtdparts= [MTD]
1041 See drivers/mtd/cmdlinepart.c.
1043 mtouchusb.raw_coordinates=
1044 [HW] Make the MicroTouch USB driver use raw coordinates
1045 ('y', default) or cooked coordinates ('n')
1047 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1049 NCR_D700= [HW,SCSI]
1050 See header of drivers/scsi/NCR_D700.c.
1052 ncr5380= [HW,SCSI]
1054 ncr53c400= [HW,SCSI]
1056 ncr53c400a= [HW,SCSI]
1058 ncr53c406a= [HW,SCSI]
1060 ncr53c8xx= [HW,SCSI]
1062 netdev= [NET] Network devices parameters
1063 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1064 Note that mem_start is often overloaded to mean
1065 something different and driver-specific.
1066 This usage is only documented in each driver source
1067 file if at all.
1069 nfsaddrs= [NFS]
1070 See Documentation/nfsroot.txt.
1072 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1073 See Documentation/nfsroot.txt.
1075 nfs.callback_tcpport=
1076 [NFS] set the TCP port on which the NFSv4 callback
1077 channel should listen.
1079 nfs.idmap_cache_timeout=
1080 [NFS] set the maximum lifetime for idmapper cache
1081 entries.
1083 nmi_watchdog= [KNL,BUGS=X86-32] Debugging features for SMP kernels
1085 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1086 emulation library even if a 387 maths coprocessor
1087 is present.
1089 noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1090 when set.
1091 Format: <int>
1093 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1094 caches in the slab allocator. Saves per-node memory,
1095 but will impact performance.
1097 noalign [KNL,ARM]
1099 noapic [SMP,APIC] Tells the kernel to not make use of any
1100 IOAPICs that may be present in the system.
1102 noasync [HW,M68K] Disables async and sync negotiation for
1103 all devices.
1105 nobats [PPC] Do not use BATs for mapping kernel lowmem
1106 on "Classic" PPC cores.
1108 nocache [ARM]
1110 nodelayacct [KNL] Disable per-task delay accounting
1112 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1114 noexec [IA-64]
1116 noexec [X86-32,X86-64]
1117 noexec=on: enable non-executable mappings (default)
1118 noexec=off: disable nn-executable mappings
1120 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1121 register save and restore. The kernel will only save
1122 legacy floating-point registers on task switch.
1124 nohlt [BUGS=ARM]
1126 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1127 instruction doesn't work correctly and not to
1128 use it.
1130 nohalt [IA-64] Tells the kernel not to use the power saving
1131 function PAL_HALT_LIGHT when idle. This increases
1132 power-consumption. On the positive side, it reduces
1133 interrupt wake-up latency, which may improve performance
1134 in certain environments such as networked servers or
1135 real-time systems.
1137 nohz= [KNL] Boottime enable/disable dynamic ticks
1138 Valid arguments: on, off
1139 Default: on
1141 noirqbalance [X86-32,SMP,KNL] Disable kernel irq balancing
1143 noirqdebug [X86-32] Disables the code which attempts to detect and
1144 disable unhandled interrupt sources.
1146 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1147 broken timer IRQ sources.
1149 noisapnp [ISAPNP] Disables ISA PnP code.
1151 noinitrd [RAM] Tells the kernel not to load any configured
1152 initial RAM disk.
1154 nointroute [IA-64]
1156 nojitter [IA64] Disables jitter checking for ITC timers.
1158 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1160 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1162 noltlbs [PPC] Do not use large page/tlb entries for kernel
1163 lowmem mapping on PPC40x.
1165 nomca [IA-64] Disable machine check abort handling
1167 nomce [X86-32] Machine Check Exception
1169 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1171 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1172 with UP alternatives
1174 noresidual [PPC] Don't use residual data on PReP machines.
1176 noresume [SWSUSP] Disables resume and restores original swap
1177 space.
1179 no-scroll [VGA] Disables scrollback.
1180 This is required for the Braillex ib80-piezo Braille
1181 reader made by F.H. Papenmeier (Germany).
1183 nosbagart [IA-64]
1185 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1187 nosmp [SMP] Tells an SMP kernel to act as a UP kernel.
1189 nosoftlockup [KNL] Disable the soft-lockup detector.
1191 nosync [HW,M68K] Disables sync negotiation for all devices.
1193 notsc [BUGS=X86-32] Disable Time Stamp Counter
1195 nousb [USB] Disable the USB subsystem
1197 nowb [ARM]
1199 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1200 one of ['zone', 'node', 'default'] can be specified
1201 This can be set from sysctl after boot.
1202 See Documentation/sysctl/vm.txt for details.
1204 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1206 opl3= [HW,OSS]
1207 Format: <io>
1209 oprofile.timer= [HW]
1210 Use timer interrupt instead of performance counters
1212 osst= [HW,SCSI] SCSI Tape Driver
1213 Format: <buffer_size>,<write_threshold>
1214 See also Documentation/scsi/st.txt.
1216 panic= [KNL] Kernel behaviour on panic
1217 Format: <timeout>
1219 parkbd.port= [HW] Parallel port number the keyboard adapter is
1220 connected to, default is 0.
1221 Format: <parport#>
1222 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1223 0 for XT, 1 for AT (default is AT).
1224 Format: <mode>
1226 parport= [HW,PPT] Specify parallel ports. 0 disables.
1227 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1228 Use 'auto' to force the driver to use any
1229 IRQ/DMA settings detected (the default is to
1230 ignore detected IRQ/DMA settings because of
1231 possible conflicts). You can specify the base
1232 address, IRQ, and DMA settings; IRQ and DMA
1233 should be numbers, or 'auto' (for using detected
1234 settings on that particular port), or 'nofifo'
1235 (to avoid using a FIFO even if it is detected).
1236 Parallel ports are assigned in the order they
1237 are specified on the command line, starting
1238 with parport0.
1240 parport_init_mode= [HW,PPT]
1241 Configure VIA parallel port to operate in
1242 a specific mode. This is necessary on Pegasos
1243 computer where firmware has no options for setting
1244 up parallel port mode and sets it to spp.
1245 Currently this function knows 686a and 8231 chips.
1246 Format: [spp|ps2|epp|ecp|ecpepp]
1248 pas2= [HW,OSS] Format:
1249 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1251 pas16= [HW,SCSI]
1252 See header of drivers/scsi/pas16.c.
1254 pause_on_oops=
1255 Halt all CPUs after the first oops has been printed for
1256 the specified number of seconds. This is to be used if
1257 your oopses keep scrolling off the screen.
1259 pcbit= [HW,ISDN]
1261 pcd. [PARIDE]
1262 See header of drivers/block/paride/pcd.c.
1263 See also Documentation/paride.txt.
1265 pci=option[,option...] [PCI] various PCI subsystem options:
1266 off [X86-32] don't probe for the PCI bus
1267 bios [X86-32] force use of PCI BIOS, don't access
1268 the hardware directly. Use this if your machine
1269 has a non-standard PCI host bridge.
1270 nobios [X86-32] disallow use of PCI BIOS, only direct
1271 hardware access methods are allowed. Use this
1272 if you experience crashes upon bootup and you
1273 suspect they are caused by the BIOS.
1274 conf1 [X86-32] Force use of PCI Configuration
1275 Mechanism 1.
1276 conf2 [X86-32] Force use of PCI Configuration
1277 Mechanism 2.
1278 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1279 Configuration
1280 nomsi [MSI] If the PCI_MSI kernel config parameter is
1281 enabled, this kernel boot option can be used to
1282 disable the use of MSI interrupts system-wide.
1283 nosort [X86-32] Don't sort PCI devices according to
1284 order given by the PCI BIOS. This sorting is
1285 done to get a device order compatible with
1286 older kernels.
1287 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1288 routing table. These calls are known to be buggy
1289 on several machines and they hang the machine
1290 when used, but on other computers it's the only
1291 way to get the interrupt routing table. Try
1292 this option if the kernel is unable to allocate
1293 IRQs or discover secondary PCI buses on your
1294 motherboard.
1295 rom [X86-32] Assign address space to expansion ROMs.
1296 Use with caution as certain devices share
1297 address decoders between ROMs and other
1298 resources.
1299 irqmask=0xMMMM [X86-32] Set a bit mask of IRQs allowed to be
1300 assigned automatically to PCI devices. You can
1301 make the kernel exclude IRQs of your ISA cards
1302 this way.
1303 pirqaddr=0xAAAAA [X86-32] Specify the physical address
1304 of the PIRQ table (normally generated
1305 by the BIOS) if it is outside the
1306 F0000h-100000h range.
1307 lastbus=N [X86-32] Scan all buses thru bus #N. Can be
1308 useful if the kernel is unable to find your
1309 secondary buses and you want to tell it
1310 explicitly which ones they are.
1311 assign-busses [X86-32] Always assign all PCI bus
1312 numbers ourselves, overriding
1313 whatever the firmware may have done.
1314 usepirqmask [X86-32] Honor the possible IRQ mask stored
1315 in the BIOS $PIR table. This is needed on
1316 some systems with broken BIOSes, notably
1317 some HP Pavilion N5400 and Omnibook XE3
1318 notebooks. This will have no effect if ACPI
1319 IRQ routing is enabled.
1320 noacpi [X86-32] Do not use ACPI for IRQ routing
1321 or for PCI scanning.
1322 routeirq Do IRQ routing for all PCI devices.
1323 This is normally done in pci_enable_device(),
1324 so this option is a temporary workaround
1325 for broken drivers that don't call it.
1326 firmware [ARM] Do not re-enumerate the bus but instead
1327 just use the configuration from the
1328 bootloader. This is currently used on
1329 IXP2000 systems where the bus has to be
1330 configured a certain way for adjunct CPUs.
1331 noearly [X86] Don't do any early type 1 scanning.
1332 This might help on some broken boards which
1333 machine check when some devices' config space
1334 is read. But various workarounds are disabled
1335 and some IOMMU drivers will not work.
1336 bfsort Sort PCI devices into breadth-first order.
1337 This sorting is done to get a device
1338 order compatible with older (<= 2.4) kernels.
1339 nobfsort Don't sort PCI devices into breadth-first order.
1340 cbiosize=nn[KMG] The fixed amount of bus space which is
1341 reserved for the CardBus bridge's IO window.
1342 The default value is 256 bytes.
1343 cbmemsize=nn[KMG] The fixed amount of bus space which is
1344 reserved for the CardBus bridge's memory
1345 window. The default value is 64 megabytes.
1347 pcmv= [HW,PCMCIA] BadgePAD 4
1349 pd. [PARIDE]
1350 See Documentation/paride.txt.
1352 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1353 boot time.
1354 Format: { 0 | 1 }
1355 See arch/parisc/kernel/pdc_chassis.c
1357 pf. [PARIDE]
1358 See Documentation/paride.txt.
1360 pg. [PARIDE]
1361 See Documentation/paride.txt.
1363 pirq= [SMP,APIC] Manual mp-table setup
1364 See Documentation/i386/IO-APIC.txt.
1366 plip= [PPT,NET] Parallel port network link
1367 Format: { parport<nr> | timid | 0 }
1368 See also Documentation/parport.txt.
1370 pnpacpi= [ACPI]
1371 { off }
1373 pnpbios= [ISAPNP]
1374 { on | off | curr | res | no-curr | no-res }
1376 pnp_reserve_irq=
1377 [ISAPNP] Exclude IRQs for the autoconfiguration
1379 pnp_reserve_dma=
1380 [ISAPNP] Exclude DMAs for the autoconfiguration
1382 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1383 Ranges are in pairs (I/O port base and size).
1385 pnp_reserve_mem=
1386 [ISAPNP] Exclude memory regions for the
1387 autoconfiguration.
1388 Ranges are in pairs (memory base and size).
1390 print-fatal-signals=
1391 [KNL] debug: print fatal signals
1392 print-fatal-signals=1: print segfault info to
1393 the kernel console.
1394 default: off.
1396 printk.time= Show timing data prefixed to each printk message line
1397 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1399 profile= [KNL] Enable kernel profiling via /proc/profile
1400 Format: [schedule,]<number>
1401 Param: "schedule" - profile schedule points.
1402 Param: <number> - step/bucket size as a power of 2 for
1403 statistical time based profiling.
1404 Param: "sleep" - profile D-state sleeping (millisecs)
1406 processor.max_cstate= [HW,ACPI]
1407 Limit processor to maximum C-state
1408 max_cstate=9 overrides any DMI blacklist limit.
1410 processor.nocst [HW,ACPI]
1411 Ignore the _CST method to determine C-states,
1412 instead using the legacy FADT method
1414 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1415 before loading.
1416 See Documentation/ramdisk.txt.
1418 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1419 probe for; one of (bare|imps|exps|lifebook|any).
1420 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1421 per second.
1422 psmouse.resetafter= [HW,MOUSE]
1423 Try to reset the device after so many bad packets
1424 (0 = never).
1425 psmouse.resolution=
1426 [HW,MOUSE] Set desired mouse resolution, in dpi.
1427 psmouse.smartscroll=
1428 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1429 0 = disabled, 1 = enabled (default).
1431 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1432 Format:
1433 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1435 pt. [PARIDE]
1436 See Documentation/paride.txt.
1438 quiet [KNL] Disable most log messages
1440 r128= [HW,DRM]
1442 raid= [HW,RAID]
1443 See Documentation/md.txt.
1445 ramdisk= [RAM] Sizes of RAM disks in kilobytes [deprecated]
1446 See Documentation/ramdisk.txt.
1448 ramdisk_blocksize= [RAM]
1449 See Documentation/ramdisk.txt.
1451 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1452 New name for the ramdisk parameter.
1453 See Documentation/ramdisk.txt.
1455 rcu.blimit= [KNL,BOOT] Set maximum number of finished
1456 RCU callbacks to process in one batch.
1458 rcu.qhimark= [KNL,BOOT] Set threshold of queued
1459 RCU callbacks over which batch limiting is disabled.
1461 rcu.qlowmark= [KNL,BOOT] Set threshold of queued
1462 RCU callbacks below which batch limiting is re-enabled.
1464 rdinit= [KNL]
1465 Format: <full_path>
1466 Run specified binary instead of /init from the ramdisk,
1467 used for early userspace startup. See initrd.
1469 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1470 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1471 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1473 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1475 reservetop= [X86-32]
1476 Format: nn[KMG]
1477 Reserves a hole at the top of the kernel virtual
1478 address space.
1480 reset_devices [KNL] Force drivers to reset the underlying device
1481 during initialization.
1483 resume= [SWSUSP]
1484 Specify the partition device for software suspend
1486 resume_offset= [SWSUSP]
1487 Specify the offset from the beginning of the partition
1488 given by "resume=" at which the swap header is located,
1489 in <PAGE_SIZE> units (needed only for swap files).
1490 See Documentation/power/swsusp-and-swap-files.txt
1492 retain_initrd [RAM] Keep initrd memory after extraction
1494 rhash_entries= [KNL,NET]
1495 Set number of hash buckets for route cache
1497 riscom8= [HW,SERIAL]
1498 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1500 ro [KNL] Mount root device read-only on boot
1502 root= [KNL] Root filesystem
1504 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1505 mount the root filesystem
1507 rootflags= [KNL] Set root filesystem mount option string
1509 rootfstype= [KNL] Set root filesystem type
1511 rootwait [KNL] Wait (indefinitely) for root device to show up.
1512 Useful for devices that are detected asynchronously
1513 (e.g. USB and MMC devices).
1515 rw [KNL] Mount root device read-write on boot
1517 S [KNL] Run init in single mode
1519 sa1100ir [NET]
1520 See drivers/net/irda/sa1100_ir.c.
1522 sb= [HW,OSS]
1523 Format: <io>,<irq>,<dma>,<dma2>
1525 sbni= [NET] Granch SBNI12 leased line adapter
1527 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1528 Format: <io>[,<timeout>[,<isapnp>]]
1530 scsi_debug_*= [SCSI]
1531 See drivers/scsi/scsi_debug.c.
1533 scsi_default_dev_flags=
1534 [SCSI] SCSI default device flags
1535 Format: <integer>
1537 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1538 Format: <vendor>:<model>:<flags>
1539 (flags are integer value)
1541 scsi_logging= [SCSI]
1543 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1544 discovered. async scans them in kernel threads,
1545 allowing boot to proceed. none ignores them, expecting
1546 user space to do the scan.
1548 selinux [SELINUX] Disable or enable SELinux at boot time.
1549 Format: { "0" | "1" }
1550 See security/selinux/Kconfig help text.
1551 0 -- disable.
1552 1 -- enable.
1553 Default value is set via kernel config option.
1554 If enabled at boot time, /selinux/disable can be used
1555 later to disable prior to initial policy load.
1557 selinux_compat_net =
1558 [SELINUX] Set initial selinux_compat_net flag value.
1559 Format: { "0" | "1" }
1560 0 -- use new secmark-based packet controls
1561 1 -- use legacy packet controls
1562 Default value is 0 (preferred).
1563 Value can be changed at runtime via
1564 /selinux/compat_net.
1566 serialnumber [BUGS=X86-32]
1568 sg_def_reserved_size= [SCSI]
1570 shapers= [NET]
1571 Maximal number of shapers.
1573 sim710= [SCSI,HW]
1574 See header of drivers/scsi/sim710.c.
1576 simeth= [IA-64]
1577 simscsi=
1579 slram= [HW,MTD]
1581 slub_debug[=options[,slabs]] [MM, SLUB]
1582 Enabling slub_debug allows one to determine the
1583 culprit if slab objects become corrupted. Enabling
1584 slub_debug can create guard zones around objects and
1585 may poison objects when not in use. Also tracks the
1586 last alloc / free. For more information see
1587 Documentation/vm/slub.txt.
1589 slub_max_order= [MM, SLUB]
1590 Determines the maximum allowed order for slabs.
1591 A high setting may cause OOMs due to memory
1592 fragmentation. For more information see
1593 Documentation/vm/slub.txt.
1595 slub_min_objects= [MM, SLUB]
1596 The minimum number of objects per slab. SLUB will
1597 increase the slab order up to slub_max_order to
1598 generate a sufficiently large slab able to contain
1599 the number of objects indicated. The higher the number
1600 of objects the smaller the overhead of tracking slabs
1601 and the less frequently locks need to be acquired.
1602 For more information see Documentation/vm/slub.txt.
1604 slub_min_order= [MM, SLUB]
1605 Determines the mininum page order for slabs. Must be
1606 lower than slub_max_order.
1607 For more information see Documentation/vm/slub.txt.
1609 slub_nomerge [MM, SLUB]
1610 Disable merging of slabs with similar size. May be
1611 necessary if there is some reason to distinguish
1612 allocs to different slabs. Debug options disable
1613 merging on their own.
1614 For more information see Documentation/vm/slub.txt.
1616 smart2= [HW]
1617 Format: <io1>[,<io2>[,...,<io8>]]
1619 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
1620 attempt to substitute SMP alternatives once at boot.
1622 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
1623 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
1624 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
1625 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
1626 smsc-ircc2.ircc_irq= [HW] IRQ line
1627 smsc-ircc2.ircc_dma= [HW] DMA channel
1628 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
1629 0: Toshiba Satellite 1800 (GP data pin select)
1630 1: Fast pin select (default)
1631 2: ATC IRMode
1633 snd-ad1816a= [HW,ALSA]
1635 snd-ad1848= [HW,ALSA]
1637 snd-ali5451= [HW,ALSA]
1639 snd-als100= [HW,ALSA]
1641 snd-als4000= [HW,ALSA]
1643 snd-azt2320= [HW,ALSA]
1645 snd-cmi8330= [HW,ALSA]
1647 snd-cmipci= [HW,ALSA]
1649 snd-cs4231= [HW,ALSA]
1651 snd-cs4232= [HW,ALSA]
1653 snd-cs4236= [HW,ALSA]
1655 snd-cs4281= [HW,ALSA]
1657 snd-cs46xx= [HW,ALSA]
1659 snd-dt019x= [HW,ALSA]
1661 snd-dummy= [HW,ALSA]
1663 snd-emu10k1= [HW,ALSA]
1665 snd-ens1370= [HW,ALSA]
1667 snd-ens1371= [HW,ALSA]
1669 snd-es968= [HW,ALSA]
1671 snd-es1688= [HW,ALSA]
1673 snd-es18xx= [HW,ALSA]
1675 snd-es1938= [HW,ALSA]
1677 snd-es1968= [HW,ALSA]
1679 snd-fm801= [HW,ALSA]
1681 snd-gusclassic= [HW,ALSA]
1683 snd-gusextreme= [HW,ALSA]
1685 snd-gusmax= [HW,ALSA]
1687 snd-hdsp= [HW,ALSA]
1689 snd-ice1712= [HW,ALSA]
1691 snd-intel8x0= [HW,ALSA]
1693 snd-interwave= [HW,ALSA]
1695 snd-interwave-stb=
1696 [HW,ALSA]
1698 snd-korg1212= [HW,ALSA]
1700 snd-maestro3= [HW,ALSA]
1702 snd-mpu401= [HW,ALSA]
1704 snd-mtpav= [HW,ALSA]
1706 snd-nm256= [HW,ALSA]
1708 snd-opl3sa2= [HW,ALSA]
1710 snd-opti92x-ad1848=
1711 [HW,ALSA]
1713 snd-opti92x-cs4231=
1714 [HW,ALSA]
1716 snd-opti93x= [HW,ALSA]
1718 snd-pmac= [HW,ALSA]
1720 snd-rme32= [HW,ALSA]
1722 snd-rme96= [HW,ALSA]
1724 snd-rme9652= [HW,ALSA]
1726 snd-sb8= [HW,ALSA]
1728 snd-sb16= [HW,ALSA]
1730 snd-sbawe= [HW,ALSA]
1732 snd-serial= [HW,ALSA]
1734 snd-sgalaxy= [HW,ALSA]
1736 snd-sonicvibes= [HW,ALSA]
1738 snd-sun-amd7930=
1739 [HW,ALSA]
1741 snd-sun-cs4231= [HW,ALSA]
1743 snd-trident= [HW,ALSA]
1745 snd-usb-audio= [HW,ALSA,USB]
1747 snd-via82xx= [HW,ALSA]
1749 snd-virmidi= [HW,ALSA]
1751 snd-wavefront= [HW,ALSA]
1753 snd-ymfpci= [HW,ALSA]
1755 sonypi.*= [HW] Sony Programmable I/O Control Device driver
1756 See Documentation/sonypi.txt
1758 specialix= [HW,SERIAL] Specialix multi-serial port adapter
1759 See Documentation/specialix.txt.
1761 spia_io_base= [HW,MTD]
1762 spia_fio_base=
1763 spia_pedr=
1764 spia_peddr=
1766 sscape= [HW,OSS]
1767 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
1769 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
1770 See Documentation/scsi/st.txt.
1772 st0x= [HW,SCSI]
1773 See header of drivers/scsi/seagate.c.
1775 sti= [PARISC,HW]
1776 Format: <num>
1777 Set the STI (builtin display/keyboard on the HP-PARISC
1778 machines) console (graphic card) which should be used
1779 as the initial boot-console.
1780 See also comment in drivers/video/console/sticore.c.
1782 sti_font= [HW]
1783 See comment in drivers/video/console/sticore.c.
1785 stifb= [HW]
1786 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
1788 sunrpc.pool_mode=
1789 [NFS]
1790 Control how the NFS server code allocates CPUs to
1791 service thread pools. Depending on how many NICs
1792 you have and where their interrupts are bound, this
1793 option will affect which CPUs will do NFS serving.
1794 Note: this parameter cannot be changed while the
1795 NFS server is running.
1797 auto the server chooses an appropriate mode
1798 automatically using heuristics
1799 global a single global pool contains all CPUs
1800 percpu one pool for each CPU
1801 pernode one pool for each NUMA node (equivalent
1802 to global on non-NUMA machines)
1804 swiotlb= [IA-64] Number of I/O TLB slabs
1806 switches= [HW,M68k]
1808 sym53c416= [HW,SCSI]
1809 See header of drivers/scsi/sym53c416.c.
1811 sysrq_always_enabled
1812 [KNL]
1813 Ignore sysrq setting - this boot parameter will
1814 neutralize any effect of /proc/sys/kernel/sysrq.
1815 Useful for debugging.
1817 t128= [HW,SCSI]
1818 See header of drivers/scsi/t128.c.
1820 tdfx= [HW,DRM]
1822 thash_entries= [KNL,NET]
1823 Set number of hash buckets for TCP connection
1825 thermal.act= [HW,ACPI]
1826 -1: disable all active trip points in all thermal zones
1827 <degrees C>: override all lowest active trip points
1829 thermal.nocrt= [HW,ACPI]
1830 Set to disable actions on ACPI thermal zone
1831 critical and hot trip points.
1833 thermal.off= [HW,ACPI]
1834 1: disable ACPI thermal control
1836 thermal.psv= [HW,ACPI]
1837 -1: disable all passive trip points
1838 <degrees C>: override all passive trip points to this value
1840 thermal.tzp= [HW,ACPI]
1841 Specify global default ACPI thermal zone polling rate
1842 <deci-seconds>: poll all this frequency
1843 0: no polling (default)
1845 time Show timing data prefixed to each printk message line
1846 [deprecated, see 'printk.time']
1848 tipar.timeout= [HW,PPT]
1849 Set communications timeout in tenths of a second
1850 (default 15).
1852 tipar.delay= [HW,PPT]
1853 Set inter-bit delay in microseconds (default 10).
1855 tmc8xx= [HW,SCSI]
1856 See header of drivers/scsi/seagate.c.
1858 tmscsim= [HW,SCSI]
1859 See comment before function dc390_setup() in
1860 drivers/scsi/tmscsim.c.
1862 tp720= [HW,PS2]
1864 trix= [HW,OSS] MediaTrix AudioTrix Pro
1865 Format:
1866 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
1868 tsdev.xres= [TS] Horizontal screen resolution.
1869 tsdev.yres= [TS] Vertical screen resolution.
1871 turbografx.map[2|3]= [HW,JOY]
1872 TurboGraFX parallel port interface
1873 Format:
1874 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
1875 See also Documentation/input/joystick-parport.txt
1877 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
1878 See header of drivers/scsi/u14-34f.c.
1880 uart401= [HW,OSS]
1881 Format: <io>,<irq>
1883 uart6850= [HW,OSS]
1884 Format: <io>,<irq>
1886 uhci-hcd.ignore_oc=
1887 [USB] Ignore overcurrent events (default N).
1888 Some badly-designed motherboards generate lots of
1889 bogus events, for ports that aren't wired to
1890 anything. Set this parameter to avoid log spamming.
1891 Note that genuine overcurrent events won't be
1892 reported either.
1894 usbcore.autosuspend=
1895 [USB] The autosuspend time delay (in seconds) used
1896 for newly-detected USB devices (default 2). This
1897 is the time required before an idle device will be
1898 autosuspended. Devices for which the delay is set
1899 to a negative value won't be autosuspended at all.
1901 usbhid.mousepoll=
1902 [USBHID] The interval which mice are to be polled at.
1904 vdso= [X86-32,SH,x86-64]
1905 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
1906 vdso=1: enable VDSO (default)
1907 vdso=0: disable VDSO mapping
1909 vector= [IA-64,SMP]
1910 vector=percpu: enable percpu vector domain
1912 video= [FB] Frame buffer configuration
1913 See Documentation/fb/modedb.txt.
1915 vga= [BOOT,X86-32] Select a particular video mode
1916 See Documentation/i386/boot.txt and
1917 Documentation/svga.txt.
1918 Use vga=ask for menu.
1919 This is actually a boot loader parameter; the value is
1920 passed to the kernel using a special protocol.
1922 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
1923 size of <nn>. This can be used to increase the
1924 minimum size (128MB on x86). It can also be used to
1925 decrease the size and leave more room for directly
1926 mapped kernel RAM.
1928 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1929 Format: <command>
1931 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1932 Format: <command>
1934 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1935 Format: <command>
1937 waveartist= [HW,OSS]
1938 Format: <io>,<irq>,<dma>,<dma2>
1940 wd33c93= [HW,SCSI]
1941 See header of drivers/scsi/wd33c93.c.
1943 wd7000= [HW,SCSI]
1944 See header of drivers/scsi/wd7000.c.
1946 wdt= [WDT] Watchdog
1947 See Documentation/watchdog/wdt.txt.
1949 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
1950 xd_geo= See header of drivers/block/xd.c.
1952 xirc2ps_cs= [NET,PCMCIA]
1953 Format:
1954 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
1956 norandmaps Don't use address space randomization
1957 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
1959 unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
1960 This is useful to get more information why
1961 you got a "dwarf2 unwinder stuck"
1963 ______________________________________________________________________
1965 TODO:
1967 Add documentation for ALSA options.
1968 Add more DRM drivers.