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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 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 GCOV GCOV profiling is enabled.
52 HW Appropriate hardware is enabled.
53 IA-64 IA-64 architecture is enabled.
54 IMA Integrity measurement architecture is enabled.
55 IOSCHED More than one I/O scheduler is enabled.
56 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
57 ISAPNP ISA PnP code is enabled.
58 ISDN Appropriate ISDN support is enabled.
59 JOY Appropriate joystick support is enabled.
60 KVM Kernel Virtual Machine support is enabled.
61 LIBATA Libata driver is enabled
62 LP Printer support is enabled.
63 LOOP Loopback device support is enabled.
64 M68k M68k architecture is enabled.
65 These options have more detailed description inside of
66 Documentation/m68k/kernel-options.txt.
67 MCA MCA bus support is enabled.
68 MDA MDA console support is enabled.
69 MOUSE Appropriate mouse support is enabled.
70 MSI Message Signaled Interrupts (PCI).
71 MTD MTD (Memory Technology Device) support is enabled.
72 NET Appropriate network support is enabled.
73 NUMA NUMA support is enabled.
74 GENERIC_TIME The generic timeofday code is enabled.
75 NFS Appropriate NFS support is enabled.
76 OSS OSS sound support is enabled.
77 PV_OPS A paravirtualized kernel is enabled.
78 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
79 PARISC The PA-RISC architecture is enabled.
80 PCI PCI bus support is enabled.
81 PCIE PCI Express support is enabled.
82 PCMCIA The PCMCIA subsystem is enabled.
83 PNP Plug & Play support is enabled.
84 PPC PowerPC architecture is enabled.
85 PPT Parallel port support is enabled.
86 PS2 Appropriate PS/2 support is enabled.
87 RAM RAM disk support is enabled.
88 S390 S390 architecture is enabled.
89 SCSI Appropriate SCSI support is enabled.
90 A lot of drivers has their options described inside of
91 Documentation/scsi/.
92 SECURITY Different security models are enabled.
93 SELINUX SELinux support is enabled.
94 SERIAL Serial support is enabled.
95 SH SuperH architecture is enabled.
96 SMP The kernel is an SMP kernel.
97 SPARC Sparc architecture is enabled.
98 SWSUSP Software suspend (hibernation) is enabled.
99 SUSPEND System suspend states are enabled.
100 FTRACE Function tracing enabled.
101 TS Appropriate touchscreen support is enabled.
102 UMS USB Mass Storage support is enabled.
103 USB USB support is enabled.
104 USBHID USB Human Interface Device support is enabled.
105 V4L Video For Linux support is enabled.
106 VGA The VGA console has been enabled.
107 VT Virtual terminal support is enabled.
108 WDT Watchdog support is enabled.
109 XT IBM PC/XT MFM hard disk support is enabled.
110 X86-32 X86-32, aka i386 architecture is enabled.
111 X86-64 X86-64 architecture is enabled.
112 More X86-64 boot options can be found in
113 Documentation/x86/x86_64/boot-options.txt .
114 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
116 In addition, the following text indicates that the option:
118 BUGS= Relates to possible processor bugs on the said processor.
119 KNL Is a kernel start-up parameter.
120 BOOT Is a boot loader parameter.
122 Parameters denoted with BOOT are actually interpreted by the boot
123 loader, and have no meaning to the kernel directly.
124 Do not modify the syntax of boot loader parameters without extreme
125 need or coordination with <Documentation/x86/boot.txt>.
127 There are also arch-specific kernel-parameters not documented here.
128 See for example <Documentation/x86/x86_64/boot-options.txt>.
130 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
131 a trailing = on the name of any parameter states that that parameter will
132 be entered as an environment variable, whereas its absence indicates that
133 it will appear as a kernel argument readable via /proc/cmdline by programs
134 running once the system is up.
136 The number of kernel parameters is not limited, but the length of the
137 complete command line (parameters including spaces etc.) is limited to
138 a fixed number of characters. This limit depends on the architecture
139 and is between 256 and 4096 characters. It is defined in the file
140 ./include/asm/setup.h as COMMAND_LINE_SIZE.
143 acpi= [HW,ACPI,X86]
144 Advanced Configuration and Power Interface
145 Format: { force | off | ht | strict | noirq | rsdt }
146 force -- enable ACPI if default was off
147 off -- disable ACPI if default was on
148 noirq -- do not use ACPI for IRQ routing
149 ht -- run only enough ACPI to enable Hyper Threading
150 strict -- Be less tolerant of platforms that are not
151 strictly ACPI specification compliant.
152 rsdt -- prefer RSDT over (default) XSDT
154 See also Documentation/power/pm.txt, pci=noacpi
156 acpi_apic_instance= [ACPI, IOAPIC]
157 Format: <int>
158 2: use 2nd APIC table, if available
159 1,0: use 1st APIC table
160 default: 0
162 acpi_backlight= [HW,ACPI]
163 acpi_backlight=vendor
164 acpi_backlight=video
165 If set to vendor, prefer vendor specific driver
166 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
167 of the ACPI video.ko driver.
169 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
170 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
171 Format: <int>
172 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
173 debug output. Bits in debug_layer correspond to a
174 _COMPONENT in an ACPI source file, e.g.,
175 #define _COMPONENT ACPI_PCI_COMPONENT
176 Bits in debug_level correspond to a level in
177 ACPI_DEBUG_PRINT statements, e.g.,
178 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
179 The debug_level mask defaults to "info". See
180 Documentation/acpi/debug.txt for more information about
181 debug layers and levels.
183 Enable processor driver info messages:
184 acpi.debug_layer=0x20000000
185 Enable PCI/PCI interrupt routing info messages:
186 acpi.debug_layer=0x400000
187 Enable AML "Debug" output, i.e., stores to the Debug
188 object while interpreting AML:
189 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
190 Enable all messages related to ACPI hardware:
191 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
193 Some values produce so much output that the system is
194 unusable. The "log_buf_len" parameter may be useful
195 if you need to capture more output.
197 acpi_display_output= [HW,ACPI]
198 acpi_display_output=vendor
199 acpi_display_output=video
200 See above.
202 acpi_irq_balance [HW,ACPI]
203 ACPI will balance active IRQs
204 default in APIC mode
206 acpi_irq_nobalance [HW,ACPI]
207 ACPI will not move active IRQs (default)
208 default in PIC mode
210 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
211 Format: <irq>,<irq>...
213 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
214 use by PCI
215 Format: <irq>,<irq>...
217 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
219 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
220 Format: To spoof as Windows 98: ="Microsoft Windows"
222 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
223 acpi_osi="string1" # add string1 -- only one string
224 acpi_osi="!string2" # remove built-in string2
225 acpi_osi= # disable all strings
227 acpi_pm_good [X86]
228 Override the pmtimer bug detection: force the kernel
229 to assume that this machine's pmtimer latches its value
230 and always returns good values.
232 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
233 Format: { level | edge | high | low }
235 acpi_serialize [HW,ACPI] force serialization of AML methods
237 acpi_skip_timer_override [HW,ACPI]
238 Recognize and ignore IRQ0/pin2 Interrupt Override.
239 For broken nForce2 BIOS resulting in XT-PIC timer.
241 acpi_sleep= [HW,ACPI] Sleep options
242 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
243 old_ordering, s4_nonvs }
244 See Documentation/power/video.txt for information on
245 s3_bios and s3_mode.
246 s3_beep is for debugging; it makes the PC's speaker beep
247 as soon as the kernel's real-mode entry point is called.
248 s4_nohwsig prevents ACPI hardware signature from being
249 used during resume from hibernation.
250 old_ordering causes the ACPI 1.0 ordering of the _PTS
251 control method, with respect to putting devices into
252 low power states, to be enforced (the ACPI 2.0 ordering
253 of _PTS is used by default).
254 s4_nonvs prevents the kernel from saving/restoring the
255 ACPI NVS memory during hibernation.
257 acpi_use_timer_override [HW,ACPI]
258 Use timer override. For some broken Nvidia NF5 boards
259 that require a timer override, but don't have HPET
261 acpi_enforce_resources= [ACPI]
262 { strict | lax | no }
263 Check for resource conflicts between native drivers
264 and ACPI OperationRegions (SystemIO and SystemMemory
265 only). IO ports and memory declared in ACPI might be
266 used by the ACPI subsystem in arbitrary AML code and
267 can interfere with legacy drivers.
268 strict (default): access to resources claimed by ACPI
269 is denied; legacy drivers trying to access reserved
270 resources will fail to bind to device using them.
271 lax: access to resources claimed by ACPI is allowed;
272 legacy drivers trying to access reserved resources
273 will bind successfully but a warning message is logged.
274 no: ACPI OperationRegions are not marked as reserved,
275 no further checks are performed.
277 ad1848= [HW,OSS]
278 Format: <io>,<irq>,<dma>,<dma2>,<type>
280 add_efi_memmap [EFI; X86] Include EFI memory map in
281 kernel's map of available physical RAM.
283 advansys= [HW,SCSI]
284 See header of drivers/scsi/advansys.c.
286 advwdt= [HW,WDT] Advantech WDT
287 Format: <iostart>,<iostop>
289 aedsp16= [HW,OSS] Audio Excel DSP 16
290 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
291 See also header of sound/oss/aedsp16.c.
293 agp= [AGP]
294 { off | try_unsupported }
295 off: disable AGP support
296 try_unsupported: try to drive unsupported chipsets
297 (may crash computer or cause data corruption)
299 aha152x= [HW,SCSI]
300 See Documentation/scsi/aha152x.txt.
302 aha1542= [HW,SCSI]
303 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
305 aic7xxx= [HW,SCSI]
306 See Documentation/scsi/aic7xxx.txt.
308 aic79xx= [HW,SCSI]
309 See Documentation/scsi/aic79xx.txt.
311 amd_iommu= [HW,X86-84]
312 Pass parameters to the AMD IOMMU driver in the system.
313 Possible values are:
314 isolate - enable device isolation (each device, as far
315 as possible, will get its own protection
316 domain) [default]
317 share - put every device behind one IOMMU into the
318 same protection domain
319 fullflush - enable flushing of IO/TLB entries when
320 they are unmapped. Otherwise they are
321 flushed before they will be reused, which
322 is a lot of faster
324 amijoy.map= [HW,JOY] Amiga joystick support
325 Map of devices attached to JOY0DAT and JOY1DAT
326 Format: <a>,<b>
327 See also Documentation/kernel/input/joystick.txt
329 analog.map= [HW,JOY] Analog joystick and gamepad support
330 Specifies type or capabilities of an analog joystick
331 connected to one of 16 gameports
332 Format: <type1>,<type2>,..<type16>
334 apc= [HW,SPARC]
335 Power management functions (SPARCstation-4/5 + deriv.)
336 Format: noidle
337 Disable APC CPU standby support. SPARCstation-Fox does
338 not play well with APC CPU idle - disable it if you have
339 APC and your system crashes randomly.
341 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
342 Change the output verbosity whilst booting
343 Format: { quiet (default) | verbose | debug }
344 Change the amount of debugging information output
345 when initialising the APIC and IO-APIC components.
347 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
348 Limit apic dumping. The parameter defines the maximal
349 number of local apics being dumped. Also it is possible
350 to set it to "all" by meaning -- no limit here.
351 Format: { 1 (default) | 2 | ... | all }.
352 The parameter valid if only apic=debug or
353 apic=verbose is specified.
354 Example: apic=debug show_lapic=all
356 apm= [APM] Advanced Power Management
357 See header of arch/x86/kernel/apm_32.c.
359 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
360 Format: <io>,<irq>,<nodeID>
362 ataflop= [HW,M68k]
364 atarimouse= [HW,MOUSE] Atari Mouse
366 atascsi= [HW,SCSI] Atari SCSI
368 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
369 EzKey and similar keyboards
371 atkbd.reset= [HW] Reset keyboard during initialization
373 atkbd.set= [HW] Select keyboard code set
374 Format: <int> (2 = AT (default), 3 = PS/2)
376 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
377 keyboards
379 atkbd.softraw= [HW] Choose between synthetic and real raw mode
380 Format: <bool> (0 = real, 1 = synthetic (default))
382 atkbd.softrepeat= [HW]
383 Use software keyboard repeat
385 autotest [IA64]
387 baycom_epp= [HW,AX25]
388 Format: <io>,<mode>
390 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
391 Format: <io>,<mode>
392 See header of drivers/net/hamradio/baycom_par.c.
394 baycom_ser_fdx= [HW,AX25]
395 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
396 Format: <io>,<irq>,<mode>[,<baud>]
397 See header of drivers/net/hamradio/baycom_ser_fdx.c.
399 baycom_ser_hdx= [HW,AX25]
400 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
401 Format: <io>,<irq>,<mode>
402 See header of drivers/net/hamradio/baycom_ser_hdx.c.
404 boot_delay= Milliseconds to delay each printk during boot.
405 Values larger than 10 seconds (10000) are changed to
406 no delay (0).
407 Format: integer
409 bootmem_debug [KNL] Enable bootmem allocator debug messages.
411 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
412 bttv.radio= Most important insmod options are available as
413 kernel args too.
414 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
415 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
417 BusLogic= [HW,SCSI]
418 See drivers/scsi/BusLogic.c, comment before function
419 BusLogic_ParseDriverOptions().
421 c101= [NET] Moxa C101 synchronous serial card
423 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
424 Sometimes CPU hardware bugs make them report the cache
425 size incorrectly. The kernel will attempt work arounds
426 to fix known problems, but for some CPUs it is not
427 possible to determine what the correct size should be.
428 This option provides an override for these situations.
430 capability.disable=
431 [SECURITY] Disable capabilities. This would normally
432 be used only if an alternative security model is to be
433 configured. Potentially dangerous and should only be
434 used if you are entirely sure of the consequences.
436 ccw_timeout_log [S390]
437 See Documentation/s390/CommonIO for details.
439 cgroup_disable= [KNL] Disable a particular controller
440 Format: {name of the controller(s) to disable}
441 {Currently supported controllers - "memory"}
443 checkreqprot [SELINUX] Set initial checkreqprot flag value.
444 Format: { "0" | "1" }
445 See security/selinux/Kconfig help text.
446 0 -- check protection applied by kernel (includes
447 any implied execute protection).
448 1 -- check protection requested by application.
449 Default value is set via a kernel config option.
450 Value can be changed at runtime via
451 /selinux/checkreqprot.
453 cio_ignore= [S390]
454 See Documentation/s390/CommonIO for details.
456 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
457 [Deprecated]
458 Forces specified clocksource (if available) to be used
459 when calculating gettimeofday(). If specified
460 clocksource is not available, it defaults to PIT.
461 Format: { pit | tsc | cyclone | pmtmr }
463 clocksource= [GENERIC_TIME] Override the default clocksource
464 Format: <string>
465 Override the default clocksource and use the clocksource
466 with the name specified.
467 Some clocksource names to choose from, depending on
468 the platform:
469 [all] jiffies (this is the base, fallback clocksource)
470 [ACPI] acpi_pm
471 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
472 pxa_timer,timer3,32k_counter,timer0_1
473 [AVR32] avr32
474 [X86-32] pit,hpet,tsc,vmi-timer;
475 scx200_hrt on Geode; cyclone on IBM x440
476 [MIPS] MIPS
477 [PARISC] cr16
478 [S390] tod
479 [SH] SuperH
480 [SPARC64] tick
481 [X86-64] hpet,tsc
483 clearcpuid=BITNUM [X86]
484 Disable CPUID feature X for the kernel. See
485 arch/x86/include/asm/cpufeature.h for the valid bit
486 numbers. Note the Linux specific bits are not necessarily
487 stable over kernel options, but the vendor specific
488 ones should be.
489 Also note that user programs calling CPUID directly
490 or using the feature without checking anything
491 will still see it. This just prevents it from
492 being used by the kernel or shown in /proc/cpuinfo.
493 Also note the kernel might malfunction if you disable
494 some critical bits.
496 cmo_free_hint= [PPC] Format: { yes | no }
497 Specify whether pages are marked as being inactive
498 when they are freed. This is used in CMO environments
499 to determine OS memory pressure for page stealing by
500 a hypervisor.
501 Default: yes
503 code_bytes [X86] How many bytes of object code to print
504 in an oops report.
505 Range: 0 - 8192
506 Default: 64
508 com20020= [HW,NET] ARCnet - COM20020 chipset
509 Format:
510 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
512 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
513 Format: <io>[,<irq>]
515 com90xx= [HW,NET]
516 ARCnet - COM90xx chipset (memory-mapped buffers)
517 Format: <io>[,<irq>[,<memstart>]]
519 condev= [HW,S390] console device
520 conmode=
522 console= [KNL] Output console device and options.
524 tty<n> Use the virtual console device <n>.
526 ttyS<n>[,options]
527 ttyUSB0[,options]
528 Use the specified serial port. The options are of
529 the form "bbbbpnf", where "bbbb" is the baud rate,
530 "p" is parity ("n", "o", or "e"), "n" is number of
531 bits, and "f" is flow control ("r" for RTS or
532 omit it). Default is "9600n8".
534 See Documentation/serial-console.txt for more
535 information. See
536 Documentation/networking/netconsole.txt for an
537 alternative.
539 uart[8250],io,<addr>[,options]
540 uart[8250],mmio,<addr>[,options]
541 Start an early, polled-mode console on the 8250/16550
542 UART at the specified I/O port or MMIO address,
543 switching to the matching ttyS device later. The
544 options are the same as for ttyS, above.
546 If the device connected to the port is not a TTY but a braille
547 device, prepend "brl," before the device type, for instance
548 console=brl,ttyS0
549 For now, only VisioBraille is supported.
551 consoleblank= [KNL] The console blank (screen saver) timeout in
552 seconds. Defaults to 10*60 = 10mins. A value of 0
553 disables the blank timer.
555 coredump_filter=
556 [KNL] Change the default value for
557 /proc/<pid>/coredump_filter.
558 See also Documentation/filesystems/proc.txt.
560 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
561 Format:
562 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
564 crashkernel=nn[KMG]@ss[KMG]
565 [KNL] Reserve a chunk of physical memory to
566 hold a kernel to switch to with kexec on panic.
568 crashkernel=range1:size1[,range2:size2,...][@offset]
569 [KNL] Same as above, but depends on the memory
570 in the running system. The syntax of range is
571 start-[end] where start and end are both
572 a memory unit (amount[KMG]). See also
573 Documentation/kdump/kdump.txt for a example.
575 cs89x0_dma= [HW,NET]
576 Format: <dma>
578 cs89x0_media= [HW,NET]
579 Format: { rj45 | aui | bnc }
581 dasd= [HW,NET]
582 See header of drivers/s390/block/dasd_devmap.c.
584 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
585 (one device per port)
586 Format: <port#>,<type>
587 See also Documentation/input/joystick-parport.txt
589 debug [KNL] Enable kernel debugging (events log level).
591 debug_locks_verbose=
592 [KNL] verbose self-tests
593 Format=<0|1>
594 Print debugging info while doing the locking API
595 self-tests.
596 We default to 0 (no extra messages), setting it to
597 1 will print _a lot_ more information - normally
598 only useful to kernel developers.
600 debug_objects [KNL] Enable object debugging
602 no_debug_objects
603 [KNL] Disable object debugging
605 debugpat [X86] Enable PAT debugging
607 decnet.addr= [HW,NET]
608 Format: <area>[,<node>]
609 See also Documentation/networking/decnet.txt.
611 default_hugepagesz=
612 [same as hugepagesz=] The size of the default
613 HugeTLB page size. This is the size represented by
614 the legacy /proc/ hugepages APIs, used for SHM, and
615 default size when mounting hugetlbfs filesystems.
616 Defaults to the default architecture's huge page size
617 if not specified.
619 dhash_entries= [KNL]
620 Set number of hash buckets for dentry cache.
622 digi= [HW,SERIAL]
623 IO parameters + enable/disable command.
625 digiepca= [HW,SERIAL]
626 See drivers/char/README.epca and
627 Documentation/serial/digiepca.txt.
629 disable_mtrr_cleanup [X86]
630 The kernel tries to adjust MTRR layout from continuous
631 to discrete, to make X server driver able to add WB
632 entry later. This parameter disables that.
634 disable_mtrr_trim [X86, Intel and AMD only]
635 By default the kernel will trim any uncacheable
636 memory out of your available memory pool based on
637 MTRR settings. This parameter disables that behavior,
638 possibly causing your machine to run very slowly.
640 disable_timer_pin_1 [X86]
641 Disable PIN 1 of APIC timer
642 Can be useful to work around chipset bugs.
644 dmasound= [HW,OSS] Sound subsystem buffers
646 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
647 this option disables the debugging code at boot.
649 dma_debug_entries=<number>
650 This option allows to tune the number of preallocated
651 entries for DMA-API debugging code. One entry is
652 required per DMA-API allocation. Use this if the
653 DMA-API debugging code disables itself because the
654 architectural default is too low.
656 dma_debug_driver=<driver_name>
657 With this option the DMA-API debugging driver
658 filter feature can be enabled at boot time. Just
659 pass the driver to filter for as the parameter.
660 The filter can be disabled or changed to another
661 driver later using sysfs.
663 dscc4.setup= [NET]
665 dtc3181e= [HW,SCSI]
667 dynamic_printk Enables pr_debug()/dev_dbg() calls if
668 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
669 These can also be switched on/off via
670 <debugfs>/dynamic_printk/modules
672 earlycon= [KNL] Output early console device and options.
673 uart[8250],io,<addr>[,options]
674 uart[8250],mmio,<addr>[,options]
675 Start an early, polled-mode console on the 8250/16550
676 UART at the specified I/O port or MMIO address.
677 The options are the same as for ttyS, above.
679 earlyprintk= [X86,SH,BLACKFIN]
680 earlyprintk=vga
681 earlyprintk=serial[,ttySn[,baudrate]]
682 earlyprintk=ttySn[,baudrate]
683 earlyprintk=dbgp[debugController#]
685 Append ",keep" to not disable it when the real console
686 takes over.
688 Only vga or serial or usb debug port at a time.
690 Currently only ttyS0 and ttyS1 are supported.
692 Interaction with the standard serial driver is not
693 very good.
695 The VGA output is eventually overwritten by the real
696 console.
698 eata= [HW,SCSI]
700 edd= [EDD]
701 Format: {"off" | "on" | "skip[mbr]"}
703 eisa_irq_edge= [PARISC,HW]
704 See header of drivers/parisc/eisa.c.
706 elanfreq= [X86-32]
707 See comment before function elanfreq_setup() in
708 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
710 elevator= [IOSCHED]
711 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
712 See Documentation/block/as-iosched.txt and
713 Documentation/block/deadline-iosched.txt for details.
715 elfcorehdr= [IA64,PPC,SH,X86]
716 Specifies physical address of start of kernel core
717 image elf header. Generally kexec loader will
718 pass this option to capture kernel.
719 See Documentation/kdump/kdump.txt for details.
721 enable_mtrr_cleanup [X86]
722 The kernel tries to adjust MTRR layout from continuous
723 to discrete, to make X server driver able to add WB
724 entry later. This parameter enables that.
726 enable_timer_pin_1 [X86]
727 Enable PIN 1 of APIC timer
728 Can be useful to work around chipset bugs
729 (in particular on some ATI chipsets).
730 The kernel tries to set a reasonable default.
732 enforcing [SELINUX] Set initial enforcing status.
733 Format: {"0" | "1"}
734 See security/selinux/Kconfig help text.
735 0 -- permissive (log only, no denials).
736 1 -- enforcing (deny and log).
737 Default value is 0.
738 Value can be changed at runtime via /selinux/enforce.
740 ether= [HW,NET] Ethernet cards parameters
741 This option is obsoleted by the "netdev=" option, which
742 has equivalent usage. See its documentation for details.
744 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
745 Format: <io>[,<irq>]
747 failslab=
748 fail_page_alloc=
749 fail_make_request=[KNL]
750 General fault injection mechanism.
751 Format: <interval>,<probability>,<space>,<times>
752 See also /Documentation/fault-injection/.
754 fd_mcs= [HW,SCSI]
755 See header of drivers/scsi/fd_mcs.c.
757 fdomain= [HW,SCSI]
758 See header of drivers/scsi/fdomain.c.
760 floppy= [HW]
761 See Documentation/blockdev/floppy.txt.
763 force_pal_cache_flush
764 [IA-64] Avoid check_sal_cache_flush which may hang on
765 buggy SAL_CACHE_FLUSH implementations. Using this
766 parameter will force ia64_sal_cache_flush to call
767 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
769 ftrace=[tracer]
770 [FTRACE] will set and start the specified tracer
771 as early as possible in order to facilitate early
772 boot debugging.
774 ftrace_dump_on_oops
775 [FTRACE] will dump the trace buffers on oops.
777 ftrace_filter=[function-list]
778 [FTRACE] Limit the functions traced by the function
779 tracer at boot up. function-list is a comma separated
780 list of functions. This list can be changed at run
781 time by the set_ftrace_filter file in the debugfs
782 tracing directory.
784 ftrace_notrace=[function-list]
785 [FTRACE] Do not trace the functions specified in
786 function-list. This list can be changed at run time
787 by the set_ftrace_notrace file in the debugfs
788 tracing directory.
790 ftrace_graph_filter=[function-list]
791 [FTRACE] Limit the top level callers functions traced
792 by the function graph tracer at boot up.
793 function-list is a comma separated list of functions
794 that can be changed at run time by the
795 set_graph_function file in the debugfs tracing directory.
797 gamecon.map[2|3]=
798 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
799 support via parallel port (up to 5 devices per port)
800 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
801 See also Documentation/input/joystick-parport.txt
803 gamma= [HW,DRM]
805 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
806 Format: off | on
807 default: on
809 gcov_persist= [GCOV] When non-zero (default), profiling data for
810 kernel modules is saved and remains accessible via
811 debugfs, even when the module is unloaded/reloaded.
812 When zero, profiling data is discarded and associated
813 debugfs files are removed at module unload time.
815 gdth= [HW,SCSI]
816 See header of drivers/scsi/gdth.c.
818 gpt [EFI] Forces disk with valid GPT signature but
819 invalid Protective MBR to be treated as GPT.
821 gvp11= [HW,SCSI]
823 hashdist= [KNL,NUMA] Large hashes allocated during boot
824 are distributed across NUMA nodes. Defaults on
825 for 64bit NUMA, off otherwise.
826 Format: 0 | 1 (for off | on)
828 hcl= [IA-64] SGI's Hardware Graph compatibility layer
830 hd= [EIDE] (E)IDE hard drive subsystem geometry
831 Format: <cyl>,<head>,<sect>
833 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
834 size of <nn>. This works even on boxes that have no
835 highmem otherwise. This also works to reduce highmem
836 size on bigger boxes.
838 highres= [KNL] Enable/disable high resolution timer mode.
839 Valid parameters: "on", "off"
840 Default: "on"
842 hisax= [HW,ISDN]
843 See Documentation/isdn/README.HiSax.
845 hlt [BUGS=ARM,SH]
847 hpet= [X86-32,HPET] option to control HPET usage
848 Format: { enable (default) | disable | force |
849 verbose }
850 disable: disable HPET and use PIT instead
851 force: allow force enabled of undocumented chips (ICH4,
852 VIA, nVidia)
853 verbose: show contents of HPET registers during setup
855 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
856 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
857 On x86-64 and powerpc, this option can be specified
858 multiple times interleaved with hugepages= to reserve
859 huge pages of different sizes. Valid pages sizes on
860 x86-64 are 2M (when the CPU supports "pse") and 1G
861 (when the CPU supports the "pdpe1gb" cpuinfo flag)
862 Note that 1GB pages can only be allocated at boot time
863 using hugepages= and not freed afterwards.
865 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
866 terminal devices. Valid values: 0..8
867 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
868 If specified, z/VM IUCV HVC accepts connections
869 from listed z/VM user IDs only.
871 i2c_bus= [HW] Override the default board specific I2C bus speed
872 or register an additional I2C bus that is not
873 registered from board initialization code.
874 Format:
875 <bus_id>,<clkrate>
877 i8042.debug [HW] Toggle i8042 debug mode
878 i8042.direct [HW] Put keyboard port into non-translated mode
879 i8042.dumbkbd [HW] Pretend that controller can only read data from
880 keyboard and cannot control its state
881 (Don't attempt to blink the leds)
882 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
883 i8042.nokbd [HW] Don't check/create keyboard port
884 i8042.noloop [HW] Disable the AUX Loopback command while probing
885 for the AUX port
886 i8042.nomux [HW] Don't check presence of an active multiplexing
887 controller
888 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
889 controllers
890 i8042.panicblink=
891 [HW] Frequency with which keyboard LEDs should blink
892 when kernel panics (default is 0.5 sec)
893 i8042.reset [HW] Reset the controller during init and cleanup
894 i8042.unlock [HW] Unlock (ignore) the keylock
896 i810= [HW,DRM]
898 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
899 indicates that the driver is running on unsupported
900 hardware.
901 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
902 does not match list of supported models.
903 i8k.power_status
904 [HW] Report power status in /proc/i8k
905 (disabled by default)
906 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
907 capability is set.
909 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
910 See Documentation/mca.txt.
912 icn= [HW,ISDN]
913 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
915 ide-core.nodma= [HW] (E)IDE subsystem
916 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
917 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
918 .cdrom .chs .ignore_cable are additional options
919 See Documentation/ide/ide.txt.
921 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
922 Claim all unknown PCI IDE storage controllers.
924 idle= [X86]
925 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
926 Poll forces a polling idle loop that can slightly
927 improve the performance of waking up a idle CPU, but
928 will use a lot of power and make the system run hot.
929 Not recommended.
930 idle=mwait: On systems which support MONITOR/MWAIT but
931 the kernel chose to not use it because it doesn't save
932 as much power as a normal idle loop, use the
933 MONITOR/MWAIT idle loop anyways. Performance should be
934 the same as idle=poll.
935 idle=halt: Halt is forced to be used for CPU idle.
936 In such case C2/C3 won't be used again.
937 idle=nomwait: Disable mwait for CPU C-states
939 ignore_loglevel [KNL]
940 Ignore loglevel setting - this will print /all/
941 kernel messages to the console. Useful for debugging.
943 ihash_entries= [KNL]
944 Set number of hash buckets for inode cache.
946 ima_audit= [IMA]
947 Format: { "0" | "1" }
948 0 -- integrity auditing messages. (Default)
949 1 -- enable informational integrity auditing messages.
951 ima_hash= [IMA]
952 Format: { "sha1" | "md5" }
953 default: "sha1"
955 ima_tcb [IMA]
956 Load a policy which meets the needs of the Trusted
957 Computing Base. This means IMA will measure all
958 programs exec'd, files mmap'd for exec, and all files
959 opened for read by uid=0.
961 in2000= [HW,SCSI]
962 See header of drivers/scsi/in2000.c.
964 init= [KNL]
965 Format: <full_path>
966 Run specified binary instead of /sbin/init as init
967 process.
969 initcall_debug [KNL] Trace initcalls as they are executed. Useful
970 for working out where the kernel is dying during
971 startup.
973 initrd= [BOOT] Specify the location of the initial ramdisk
975 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
976 Format: <irq>
978 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
979 on
980 Enable intel iommu driver.
981 off
982 Disable intel iommu driver.
983 igfx_off [Default Off]
984 By default, gfx is mapped as normal device. If a gfx
985 device has a dedicated DMAR unit, the DMAR unit is
986 bypassed by not enabling DMAR with this option. In
987 this case, gfx device will use physical address for
988 DMA.
989 forcedac [x86_64]
990 With this option iommu will not optimize to look
991 for io virtual address below 32 bit forcing dual
992 address cycle on pci bus for cards supporting greater
993 than 32 bit addressing. The default is to look
994 for translation below 32 bit and if not available
995 then look in the higher range.
996 strict [Default Off]
997 With this option on every unmap_single operation will
998 result in a hardware IOTLB flush operation as opposed
999 to batching them for performance.
1001 inttest= [IA64]
1003 iomem= Disable strict checking of access to MMIO memory
1004 strict regions from userspace.
1005 relaxed
1007 iommu= [x86]
1008 off
1009 force
1010 noforce
1011 biomerge
1012 panic
1013 nopanic
1014 merge
1015 nomerge
1016 forcesac
1017 soft
1018 pt [x86, IA64]
1020 io7= [HW] IO7 for Marvel based alpha systems
1021 See comment before marvel_specify_io7 in
1022 arch/alpha/kernel/core_marvel.c.
1024 io_delay= [X86] I/O delay method
1025 0x80
1026 Standard port 0x80 based delay
1027 0xed
1028 Alternate port 0xed based delay (needed on some systems)
1029 udelay
1030 Simple two microseconds delay
1031 none
1032 No delay
1034 ip= [IP_PNP]
1035 See Documentation/filesystems/nfsroot.txt.
1037 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1038 See comment before ip2_setup() in
1039 drivers/char/ip2/ip2base.c.
1041 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1042 See header of drivers/scsi/ips.c.
1044 irqfixup [HW]
1045 When an interrupt is not handled search all handlers
1046 for it. Intended to get systems with badly broken
1047 firmware running.
1049 irqpoll [HW]
1050 When an interrupt is not handled search all handlers
1051 for it. Also check all handlers each timer
1052 interrupt. Intended to get systems with badly broken
1053 firmware running.
1055 isapnp= [ISAPNP]
1056 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1058 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1059 Format:
1060 <cpu number>,...,<cpu number>
1061 or
1062 <cpu number>-<cpu number>
1063 (must be a positive range in ascending order)
1064 or a mixture
1065 <cpu number>,...,<cpu number>-<cpu number>
1067 This option can be used to specify one or more CPUs
1068 to isolate from the general SMP balancing and scheduling
1069 algorithms. You can move a process onto or off an
1070 "isolated" CPU via the CPU affinity syscalls or cpuset.
1071 <cpu number> begins at 0 and the maximum value is
1072 "number of CPUs in system - 1".
1074 This option is the preferred way to isolate CPUs. The
1075 alternative -- manually setting the CPU mask of all
1076 tasks in the system -- can cause problems and
1077 suboptimal load balancer performance.
1079 iucv= [HW,NET]
1081 js= [HW,JOY] Analog joystick
1082 See Documentation/input/joystick.txt.
1084 keepinitrd [HW,ARM]
1086 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1087 specifies the amount of memory usable by the kernel
1088 for non-movable allocations. The requested amount is
1089 spread evenly throughout all nodes in the system. The
1090 remaining memory in each node is used for Movable
1091 pages. In the event, a node is too small to have both
1092 kernelcore and Movable pages, kernelcore pages will
1093 take priority and other nodes will have a larger number
1094 of kernelcore pages. The Movable zone is used for the
1095 allocation of pages that may be reclaimed or moved
1096 by the page migration subsystem. This means that
1097 HugeTLB pages may not be allocated from this zone.
1098 Note that allocations like PTEs-from-HighMem still
1099 use the HighMem zone if it exists, and the Normal
1100 zone if it does not.
1102 kgdboc= [HW] kgdb over consoles.
1103 Requires a tty driver that supports console polling.
1104 (only serial supported for now)
1105 Format: <serial_device>[,baud]
1107 kmac= [MIPS] korina ethernet MAC address.
1108 Configure the RouterBoard 532 series on-chip
1109 Ethernet adapter MAC address.
1111 kmemleak= [KNL] Boot-time kmemleak enable/disable
1112 Valid arguments: on, off
1113 Default: on
1115 kstack=N [X86] Print N words from the kernel stack
1116 in oops dumps.
1118 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1119 Default is 0 (don't ignore, but inject #GP)
1121 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1122 Default is 1 (enabled)
1124 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1125 Default is 0 (off)
1127 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1128 for all guests.
1129 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1131 kvm-intel.bypass_guest_pf=
1132 [KVM,Intel] Disables bypassing of guest page faults
1133 on Intel chips. Default is 1 (enabled)
1135 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1136 (virtualized MMU) support on capable Intel chips.
1137 Default is 1 (enabled)
1139 kvm-intel.emulate_invalid_guest_state=
1140 [KVM,Intel] Enable emulation of invalid guest states
1141 Default is 0 (disabled)
1143 kvm-intel.flexpriority=
1144 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1145 Default is 1 (enabled)
1147 kvm-intel.unrestricted_guest=
1148 [KVM,Intel] Disable unrestricted guest feature
1149 (virtualized real and unpaged mode) on capable
1150 Intel chips. Default is 1 (enabled)
1152 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1153 feature (tagged TLBs) on capable Intel chips.
1154 Default is 1 (enabled)
1156 l2cr= [PPC]
1158 l3cr= [PPC]
1160 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1161 disabled it.
1163 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1164 in C2 power state.
1166 libata.dma= [LIBATA] DMA control
1167 libata.dma=0 Disable all PATA and SATA DMA
1168 libata.dma=1 PATA and SATA Disk DMA only
1169 libata.dma=2 ATAPI (CDROM) DMA only
1170 libata.dma=4 Compact Flash DMA only
1171 Combinations also work, so libata.dma=3 enables DMA
1172 for disks and CDROMs, but not CFs.
1174 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1175 libata.ignore_hpa=0 keep BIOS limits (default)
1176 libata.ignore_hpa=1 ignore limits, using full disk
1178 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1179 when set.
1180 Format: <int>
1182 libata.force= [LIBATA] Force configurations. The format is comma
1183 separated list of "[ID:]VAL" where ID is
1184 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1185 matching port, link or device. Basically, it matches
1186 the ATA ID string printed on console by libata. If
1187 the whole ID part is omitted, the last PORT and DEVICE
1188 values are used. If ID hasn't been specified yet, the
1189 configuration applies to all ports, links and devices.
1191 If only DEVICE is omitted, the parameter applies to
1192 the port and all links and devices behind it. DEVICE
1193 number of 0 either selects the first device or the
1194 first fan-out link behind PMP device. It does not
1195 select the host link. DEVICE number of 15 selects the
1196 host link and device attached to it.
1198 The VAL specifies the configuration to force. As long
1199 as there's no ambiguity shortcut notation is allowed.
1200 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1201 The following configurations can be forced.
1203 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1204 Any ID with matching PORT is used.
1206 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1208 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1209 udma[/][16,25,33,44,66,100,133] notation is also
1210 allowed.
1212 * [no]ncq: Turn on or off NCQ.
1214 * nohrst, nosrst, norst: suppress hard, soft
1215 and both resets.
1217 If there are multiple matching configurations changing
1218 the same attribute, the last one is used.
1220 lmb=debug [KNL] Enable lmb debug messages.
1222 load_ramdisk= [RAM] List of ramdisks to load from floppy
1223 See Documentation/blockdev/ramdisk.txt.
1225 lockd.nlm_grace_period=P [NFS] Assign grace period.
1226 Format: <integer>
1228 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1229 Format: <integer>
1231 lockd.nlm_timeout=T [NFS] Assign timeout value.
1232 Format: <integer>
1234 lockd.nlm_udpport=M [NFS] Assign UDP port.
1235 Format: <integer>
1237 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1238 Format: <irq>
1240 loglevel= All Kernel Messages with a loglevel smaller than the
1241 console loglevel will be printed to the console. It can
1242 also be changed with klogd or other programs. The
1243 loglevels are defined as follows:
1245 0 (KERN_EMERG) system is unusable
1246 1 (KERN_ALERT) action must be taken immediately
1247 2 (KERN_CRIT) critical conditions
1248 3 (KERN_ERR) error conditions
1249 4 (KERN_WARNING) warning conditions
1250 5 (KERN_NOTICE) normal but significant condition
1251 6 (KERN_INFO) informational
1252 7 (KERN_DEBUG) debug-level messages
1254 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1255 Format: { n | nk | nM }
1256 n must be a power of two. The default size
1257 is set in the kernel config file.
1259 logo.nologo [FB] Disables display of the built-in Linux logo.
1260 This may be used to provide more screen space for
1261 kernel log messages and is useful when debugging
1262 kernel boot problems.
1264 lp=0 [LP] Specify parallel ports to use, e.g,
1265 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1266 lp=reset first parallel port). 'lp=0' disables the
1267 lp=auto printer driver. 'lp=reset' (which can be
1268 specified in addition to the ports) causes
1269 attached printers to be reset. Using
1270 lp=port1,port2,... specifies the parallel ports
1271 to associate lp devices with, starting with
1272 lp0. A port specification may be 'none' to skip
1273 that lp device, or a parport name such as
1274 'parport0'. Specifying 'lp=auto' instead of a
1275 port specification list means that device IDs
1276 from each port should be examined, to see if
1277 an IEEE 1284-compliant printer is attached; if
1278 so, the driver will manage that printer.
1279 See also header of drivers/char/lp.c.
1281 lpj=n [KNL]
1282 Sets loops_per_jiffy to given constant, thus avoiding
1283 time-consuming boot-time autodetection (up to 250 ms per
1284 CPU). 0 enables autodetection (default). To determine
1285 the correct value for your kernel, boot with normal
1286 autodetection and see what value is printed. Note that
1287 on SMP systems the preset will be applied to all CPUs,
1288 which is likely to cause problems if your CPUs need
1289 significantly divergent settings. An incorrect value
1290 will cause delays in the kernel to be wrong, leading to
1291 unpredictable I/O errors and other breakage. Although
1292 unlikely, in the extreme case this might damage your
1293 hardware.
1295 ltpc= [NET]
1296 Format: <io>,<irq>,<dma>
1298 mac5380= [HW,SCSI] Format:
1299 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1301 machvec= [IA64] Force the use of a particular machine-vector
1302 (machvec) in a generic kernel.
1303 Example: machvec=hpzx1_swiotlb
1305 machtype= [Loongson] Share the same kernel image file between different
1306 yeeloong laptop.
1307 Example: machtype=lemote-yeeloong-2f-7inch
1309 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1310 than or equal to this physical address is ignored.
1312 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1313 should make use of. maxcpus=n : n >= 0 limits the
1314 kernel to using 'n' processors. n=0 is a special case,
1315 it is equivalent to "nosmp", which also disables
1316 the IO APIC.
1318 max_loop= [LOOP] Maximum number of loopback devices that can
1319 be mounted
1320 Format: <1-256>
1322 max_luns= [SCSI] Maximum number of LUNs to probe.
1323 Should be between 1 and 2^32-1.
1325 max_report_luns=
1326 [SCSI] Maximum number of LUNs received.
1327 Should be between 1 and 16384.
1329 mcatest= [IA-64]
1331 mce [X86-32] Machine Check Exception
1333 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1335 md= [HW] RAID subsystems devices and level
1336 See Documentation/md.txt.
1338 mdacon= [MDA]
1339 Format: <first>,<last>
1340 Specifies range of consoles to be captured by the MDA.
1342 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1343 Amount of memory to be used when the kernel is not able
1344 to see the whole system memory or for test.
1345 [X86-32] Use together with memmap= to avoid physical
1346 address space collisions. Without memmap= PCI devices
1347 could be placed at addresses belonging to unused RAM.
1349 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1350 memory.
1352 memchunk=nn[KMG]
1353 [KNL,SH] Allow user to override the default size for
1354 per-device physically contiguous DMA buffers.
1356 memmap=exactmap [KNL,X86] Enable setting of an exact
1357 E820 memory map, as specified by the user.
1358 Such memmap=exactmap lines can be constructed based on
1359 BIOS output or other requirements. See the memmap=nn@ss
1360 option description.
1362 memmap=nn[KMG]@ss[KMG]
1363 [KNL] Force usage of a specific region of memory
1364 Region of memory to be used, from ss to ss+nn.
1366 memmap=nn[KMG]#ss[KMG]
1367 [KNL,ACPI] Mark specific memory as ACPI data.
1368 Region of memory to be used, from ss to ss+nn.
1370 memmap=nn[KMG]$ss[KMG]
1371 [KNL,ACPI] Mark specific memory as reserved.
1372 Region of memory to be used, from ss to ss+nn.
1373 Example: Exclude memory from 0x18690000-0x1869ffff
1374 memmap=64K$0x18690000
1375 or
1376 memmap=0x10000$0x18690000
1378 memory_corruption_check=0/1 [X86]
1379 Some BIOSes seem to corrupt the first 64k of
1380 memory when doing things like suspend/resume.
1381 Setting this option will scan the memory
1382 looking for corruption. Enabling this will
1383 both detect corruption and prevent the kernel
1384 from using the memory being corrupted.
1385 However, its intended as a diagnostic tool; if
1386 repeatable BIOS-originated corruption always
1387 affects the same memory, you can use memmap=
1388 to prevent the kernel from using that memory.
1390 memory_corruption_check_size=size [X86]
1391 By default it checks for corruption in the low
1392 64k, making this memory unavailable for normal
1393 use. Use this parameter to scan for
1394 corruption in more or less memory.
1396 memory_corruption_check_period=seconds [X86]
1397 By default it checks for corruption every 60
1398 seconds. Use this parameter to check at some
1399 other rate. 0 disables periodic checking.
1401 memtest= [KNL,X86] Enable memtest
1402 Format: <integer>
1403 default : 0 <disable>
1404 Specifies the number of memtest passes to be
1405 performed. Each pass selects another test
1406 pattern from a given set of patterns. Memtest
1407 fills the memory with this pattern, validates
1408 memory contents and reserves bad memory
1409 regions that are detected.
1411 meye.*= [HW] Set MotionEye Camera parameters
1412 See Documentation/video4linux/meye.txt.
1414 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1415 Multi-Function General Purpose Timers on AMD Geode
1416 platforms.
1418 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1419 the BIOS has incorrectly applied a workaround. TinyBIOS
1420 version 0.98 is known to be affected, 0.99 fixes the
1421 problem by letting the user disable the workaround.
1423 mga= [HW,DRM]
1425 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1426 physical address is ignored.
1428 mini2440= [ARM,HW,KNL]
1429 Format:[0..2][b][c][t]
1430 Default: "0tb"
1431 MINI2440 configuration specification:
1432 0 - The attached screen is the 3.5" TFT
1433 1 - The attached screen is the 7" TFT
1434 2 - The VGA Shield is attached (1024x768)
1435 Leaving out the screen size parameter will not load
1436 the TFT driver, and the framebuffer will be left
1437 unconfigured.
1438 b - Enable backlight. The TFT backlight pin will be
1439 linked to the kernel VESA blanking code and a GPIO
1440 LED. This parameter is not necessary when using the
1441 VGA shield.
1442 c - Enable the s3c camera interface.
1443 t - Reserved for enabling touchscreen support. The
1444 touchscreen support is not enabled in the mainstream
1445 kernel as of 2.6.30, a preliminary port can be found
1446 in the "bleeding edge" mini2440 support kernel at
1447 http://repo.or.cz/w/linux-2.6/mini2440.git
1449 mminit_loglevel=
1450 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1451 parameter allows control of the logging verbosity for
1452 the additional memory initialisation checks. A value
1453 of 0 disables mminit logging and a level of 4 will
1454 log everything. Information is printed at KERN_DEBUG
1455 so loglevel=8 may also need to be specified.
1457 mousedev.tap_time=
1458 [MOUSE] Maximum time between finger touching and
1459 leaving touchpad surface for touch to be considered
1460 a tap and be reported as a left button click (for
1461 touchpads working in absolute mode only).
1462 Format: <msecs>
1463 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1464 reporting absolute coordinates, such as tablets
1465 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1466 reporting absolute coordinates, such as tablets
1468 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1469 is similar to kernelcore except it specifies the
1470 amount of memory used for migratable allocations.
1471 If both kernelcore and movablecore is specified,
1472 then kernelcore will be at *least* the specified
1473 value but may be more. If movablecore on its own
1474 is specified, the administrator must be careful
1475 that the amount of memory usable for all allocations
1476 is not too small.
1478 mpu401= [HW,OSS]
1479 Format: <io>,<irq>
1481 MTD_Partition= [MTD]
1482 Format: <name>,<region-number>,<size>,<offset>
1484 MTD_Region= [MTD] Format:
1485 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1487 mtdparts= [MTD]
1488 See drivers/mtd/cmdlinepart.c.
1490 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1492 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1494 boundary - index of last SLC block on Flex-OneNAND.
1495 The remaining blocks are configured as MLC blocks.
1496 lock - Configure if Flex-OneNAND boundary should be locked.
1497 Once locked, the boundary cannot be changed.
1498 1 indicates lock status, 0 indicates unlock status.
1500 mtdset= [ARM]
1501 ARM/S3C2412 JIVE boot control
1503 See arch/arm/mach-s3c2412/mach-jive.c
1505 mtouchusb.raw_coordinates=
1506 [HW] Make the MicroTouch USB driver use raw coordinates
1507 ('y', default) or cooked coordinates ('n')
1509 mtrr_chunk_size=nn[KMG] [X86]
1510 used for mtrr cleanup. It is largest continuous chunk
1511 that could hold holes aka. UC entries.
1513 mtrr_gran_size=nn[KMG] [X86]
1514 Used for mtrr cleanup. It is granularity of mtrr block.
1515 Default is 1.
1516 Large value could prevent small alignment from
1517 using up MTRRs.
1519 mtrr_spare_reg_nr=n [X86]
1520 Format: <integer>
1521 Range: 0,7 : spare reg number
1522 Default : 1
1523 Used for mtrr cleanup. It is spare mtrr entries number.
1524 Set to 2 or more if your graphical card needs more.
1526 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1528 NCR_D700= [HW,SCSI]
1529 See header of drivers/scsi/NCR_D700.c.
1531 ncr5380= [HW,SCSI]
1533 ncr53c400= [HW,SCSI]
1535 ncr53c400a= [HW,SCSI]
1537 ncr53c406a= [HW,SCSI]
1539 ncr53c8xx= [HW,SCSI]
1541 netdev= [NET] Network devices parameters
1542 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1543 Note that mem_start is often overloaded to mean
1544 something different and driver-specific.
1545 This usage is only documented in each driver source
1546 file if at all.
1548 nf_conntrack.acct=
1549 [NETFILTER] Enable connection tracking flow accounting
1550 0 to disable accounting
1551 1 to enable accounting
1552 Default value depends on CONFIG_NF_CT_ACCT that is
1553 going to be removed in 2.6.29.
1555 nfsaddrs= [NFS]
1556 See Documentation/filesystems/nfsroot.txt.
1558 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1559 See Documentation/filesystems/nfsroot.txt.
1561 nfs.callback_tcpport=
1562 [NFS] set the TCP port on which the NFSv4 callback
1563 channel should listen.
1565 nfs.cache_getent=
1566 [NFS] sets the pathname to the program which is used
1567 to update the NFS client cache entries.
1569 nfs.cache_getent_timeout=
1570 [NFS] sets the timeout after which an attempt to
1571 update a cache entry is deemed to have failed.
1573 nfs.idmap_cache_timeout=
1574 [NFS] set the maximum lifetime for idmapper cache
1575 entries.
1577 nfs.enable_ino64=
1578 [NFS] enable 64-bit inode numbers.
1579 If zero, the NFS client will fake up a 32-bit inode
1580 number for the readdir() and stat() syscalls instead
1581 of returning the full 64-bit number.
1582 The default is to return 64-bit inode numbers.
1584 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1585 when a NMI is triggered.
1586 Format: [state][,regs][,debounce][,die]
1588 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1589 Format: [panic,][num]
1590 Valid num: 0,1,2
1591 0 - turn nmi_watchdog off
1592 1 - use the IO-APIC timer for the NMI watchdog
1593 2 - use the local APIC for the NMI watchdog using
1594 a performance counter. Note: This will use one
1595 performance counter and the local APIC's performance
1596 vector.
1597 When panic is specified, panic when an NMI watchdog
1598 timeout occurs.
1599 This is useful when you use a panic=... timeout and
1600 need the box quickly up again.
1601 Instead of 1 and 2 it is possible to use the following
1602 symbolic names: lapic and ioapic
1603 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1605 netpoll.carrier_timeout=
1606 [NET] Specifies amount of time (in seconds) that
1607 netpoll should wait for a carrier. By default netpoll
1608 waits 4 seconds.
1610 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1611 emulation library even if a 387 maths coprocessor
1612 is present.
1614 no_console_suspend
1615 [HW] Never suspend the console
1616 Disable suspending of consoles during suspend and
1617 hibernate operations. Once disabled, debugging
1618 messages can reach various consoles while the rest
1619 of the system is being put to sleep (ie, while
1620 debugging driver suspend/resume hooks). This may
1621 not work reliably with all consoles, but is known
1622 to work with serial and VGA consoles.
1624 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1625 caches in the slab allocator. Saves per-node memory,
1626 but will impact performance.
1628 noalign [KNL,ARM]
1630 noapic [SMP,APIC] Tells the kernel to not make use of any
1631 IOAPICs that may be present in the system.
1633 nobats [PPC] Do not use BATs for mapping kernel lowmem
1634 on "Classic" PPC cores.
1636 nocache [ARM]
1638 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1640 nodelayacct [KNL] Disable per-task delay accounting
1642 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1644 nodsp [SH] Disable hardware DSP at boot time.
1646 noefi [X86] Disable EFI runtime services support.
1648 noexec [IA-64]
1650 noexec [X86]
1651 On X86-32 available only on PAE configured kernels.
1652 noexec=on: enable non-executable mappings (default)
1653 noexec=off: disable non-executable mappings
1655 noexec32 [X86-64]
1656 This affects only 32-bit executables.
1657 noexec32=on: enable non-executable mappings (default)
1658 read doesn't imply executable mappings
1659 noexec32=off: disable non-executable mappings
1660 read implies executable mappings
1662 nofpu [SH] Disable hardware FPU at boot time.
1664 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1665 register save and restore. The kernel will only save
1666 legacy floating-point registers on task switch.
1668 noxsave [BUGS=X86] Disables x86 extended register state save
1669 and restore using xsave. The kernel will fallback to
1670 enabling legacy floating-point and sse state.
1672 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1673 wfi(ARM) instruction doesn't work correctly and not to
1674 use it. This is also useful when using JTAG debugger.
1676 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1677 instruction doesn't work correctly and not to
1678 use it.
1680 no_file_caps Tells the kernel not to honor file capabilities. The
1681 only way then for a file to be executed with privilege
1682 is to be setuid root or executed by root.
1684 nohalt [IA-64] Tells the kernel not to use the power saving
1685 function PAL_HALT_LIGHT when idle. This increases
1686 power-consumption. On the positive side, it reduces
1687 interrupt wake-up latency, which may improve performance
1688 in certain environments such as networked servers or
1689 real-time systems.
1691 nohz= [KNL] Boottime enable/disable dynamic ticks
1692 Valid arguments: on, off
1693 Default: on
1695 noiotrap [SH] Disables trapped I/O port accesses.
1697 noirqdebug [X86-32] Disables the code which attempts to detect and
1698 disable unhandled interrupt sources.
1700 no_timer_check [X86,APIC] Disables the code which tests for
1701 broken timer IRQ sources.
1703 noisapnp [ISAPNP] Disables ISA PnP code.
1705 noinitrd [RAM] Tells the kernel not to load any configured
1706 initial RAM disk.
1708 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1709 remapping.
1711 nointroute [IA-64]
1713 nojitter [IA64] Disables jitter checking for ITC timers.
1715 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1717 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1719 noltlbs [PPC] Do not use large page/tlb entries for kernel
1720 lowmem mapping on PPC40x.
1722 nomca [IA-64] Disable machine check abort handling
1724 nomce [X86-32] Machine Check Exception
1726 nomfgpt [X86-32] Disable Multi-Function General Purpose
1727 Timer usage (for AMD Geode machines).
1729 norandmaps Don't use address space randomization. Equivalent to
1730 echo 0 > /proc/sys/kernel/randomize_va_space
1732 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1734 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1735 with UP alternatives
1737 noresidual [PPC] Don't use residual data on PReP machines.
1739 noresume [SWSUSP] Disables resume and restores original swap
1740 space.
1742 no-scroll [VGA] Disables scrollback.
1743 This is required for the Braillex ib80-piezo Braille
1744 reader made by F.H. Papenmeier (Germany).
1746 nosbagart [IA-64]
1748 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1750 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1751 and disable the IO APIC. legacy for "maxcpus=0".
1753 nosoftlockup [KNL] Disable the soft-lockup detector.
1755 noswapaccount [KNL] Disable accounting of swap in memory resource
1756 controller. (See Documentation/cgroups/memory.txt)
1758 nosync [HW,M68K] Disables sync negotiation for all devices.
1760 notsc [BUGS=X86-32] Disable Time Stamp Counter
1762 nousb [USB] Disable the USB subsystem
1764 nowb [ARM]
1766 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1768 nptcg= [IA64] Override max number of concurrent global TLB
1769 purges which is reported from either PAL_VM_SUMMARY or
1770 SAL PALO.
1772 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1774 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1775 one of ['zone', 'node', 'default'] can be specified
1776 This can be set from sysctl after boot.
1777 See Documentation/sysctl/vm.txt for details.
1779 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1780 See Documentation/debugging-via-ohci1394.txt for more
1781 info.
1783 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1784 Rather than timing out after 20 ms if an EC
1785 command is not properly ACKed, override the length
1786 of the timeout. We have interrupts disabled while
1787 waiting for the ACK, so if this is set too high
1788 interrupts *may* be lost!
1790 omap_mux= [OMAP] Override bootloader pin multiplexing.
1791 Format: <mux_mode0.mode_name=value>...
1792 For example, to override I2C bus2:
1793 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1795 opl3= [HW,OSS]
1796 Format: <io>
1798 oprofile.timer= [HW]
1799 Use timer interrupt instead of performance counters
1801 oprofile.cpu_type= Force an oprofile cpu type
1802 This might be useful if you have an older oprofile
1803 userland or if you want common events.
1804 Format: { arch_perfmon }
1805 arch_perfmon: [X86] Force use of architectural
1806 perfmon on Intel CPUs instead of the
1807 CPU specific event set.
1809 osst= [HW,SCSI] SCSI Tape Driver
1810 Format: <buffer_size>,<write_threshold>
1811 See also Documentation/scsi/st.txt.
1813 panic= [KNL] Kernel behaviour on panic
1814 Format: <timeout>
1816 parkbd.port= [HW] Parallel port number the keyboard adapter is
1817 connected to, default is 0.
1818 Format: <parport#>
1819 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1820 0 for XT, 1 for AT (default is AT).
1821 Format: <mode>
1823 parport= [HW,PPT] Specify parallel ports. 0 disables.
1824 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1825 Use 'auto' to force the driver to use any
1826 IRQ/DMA settings detected (the default is to
1827 ignore detected IRQ/DMA settings because of
1828 possible conflicts). You can specify the base
1829 address, IRQ, and DMA settings; IRQ and DMA
1830 should be numbers, or 'auto' (for using detected
1831 settings on that particular port), or 'nofifo'
1832 (to avoid using a FIFO even if it is detected).
1833 Parallel ports are assigned in the order they
1834 are specified on the command line, starting
1835 with parport0.
1837 parport_init_mode= [HW,PPT]
1838 Configure VIA parallel port to operate in
1839 a specific mode. This is necessary on Pegasos
1840 computer where firmware has no options for setting
1841 up parallel port mode and sets it to spp.
1842 Currently this function knows 686a and 8231 chips.
1843 Format: [spp|ps2|epp|ecp|ecpepp]
1845 pas2= [HW,OSS] Format:
1846 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1848 pas16= [HW,SCSI]
1849 See header of drivers/scsi/pas16.c.
1851 pause_on_oops=
1852 Halt all CPUs after the first oops has been printed for
1853 the specified number of seconds. This is to be used if
1854 your oopses keep scrolling off the screen.
1856 pcbit= [HW,ISDN]
1858 pcd. [PARIDE]
1859 See header of drivers/block/paride/pcd.c.
1860 See also Documentation/blockdev/paride.txt.
1862 pci=option[,option...] [PCI] various PCI subsystem options:
1863 earlydump [X86] dump PCI config space before the kernel
1864 changes anything
1865 off [X86] don't probe for the PCI bus
1866 bios [X86-32] force use of PCI BIOS, don't access
1867 the hardware directly. Use this if your machine
1868 has a non-standard PCI host bridge.
1869 nobios [X86-32] disallow use of PCI BIOS, only direct
1870 hardware access methods are allowed. Use this
1871 if you experience crashes upon bootup and you
1872 suspect they are caused by the BIOS.
1873 conf1 [X86] Force use of PCI Configuration
1874 Mechanism 1.
1875 conf2 [X86] Force use of PCI Configuration
1876 Mechanism 2.
1877 noaer [PCIE] If the PCIEAER kernel config parameter is
1878 enabled, this kernel boot option can be used to
1879 disable the use of PCIE advanced error reporting.
1880 nodomains [PCI] Disable support for multiple PCI
1881 root domains (aka PCI segments, in ACPI-speak).
1882 nommconf [X86] Disable use of MMCONFIG for PCI
1883 Configuration
1884 check_enable_amd_mmconf [X86] check for and enable
1885 properly configured MMIO access to PCI
1886 config space on AMD family 10h CPU
1887 nomsi [MSI] If the PCI_MSI kernel config parameter is
1888 enabled, this kernel boot option can be used to
1889 disable the use of MSI interrupts system-wide.
1890 noioapicquirk [APIC] Disable all boot interrupt quirks.
1891 Safety option to keep boot IRQs enabled. This
1892 should never be necessary.
1893 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1894 primary IO-APIC for bridges that cannot disable
1895 boot IRQs. This fixes a source of spurious IRQs
1896 when the system masks IRQs.
1897 noioapicreroute [APIC] Disable workaround that uses the
1898 boot IRQ equivalent of an IRQ that connects to
1899 a chipset where boot IRQs cannot be disabled.
1900 The opposite of ioapicreroute.
1901 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1902 routing table. These calls are known to be buggy
1903 on several machines and they hang the machine
1904 when used, but on other computers it's the only
1905 way to get the interrupt routing table. Try
1906 this option if the kernel is unable to allocate
1907 IRQs or discover secondary PCI buses on your
1908 motherboard.
1909 rom [X86] Assign address space to expansion ROMs.
1910 Use with caution as certain devices share
1911 address decoders between ROMs and other
1912 resources.
1913 norom [X86] Do not assign address space to
1914 expansion ROMs that do not already have
1915 BIOS assigned address ranges.
1916 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1917 assigned automatically to PCI devices. You can
1918 make the kernel exclude IRQs of your ISA cards
1919 this way.
1920 pirqaddr=0xAAAAA [X86] Specify the physical address
1921 of the PIRQ table (normally generated
1922 by the BIOS) if it is outside the
1923 F0000h-100000h range.
1924 lastbus=N [X86] Scan all buses thru bus #N. Can be
1925 useful if the kernel is unable to find your
1926 secondary buses and you want to tell it
1927 explicitly which ones they are.
1928 assign-busses [X86] Always assign all PCI bus
1929 numbers ourselves, overriding
1930 whatever the firmware may have done.
1931 usepirqmask [X86] Honor the possible IRQ mask stored
1932 in the BIOS $PIR table. This is needed on
1933 some systems with broken BIOSes, notably
1934 some HP Pavilion N5400 and Omnibook XE3
1935 notebooks. This will have no effect if ACPI
1936 IRQ routing is enabled.
1937 noacpi [X86] Do not use ACPI for IRQ routing
1938 or for PCI scanning.
1939 use_crs [X86] Use _CRS for PCI resource
1940 allocation.
1941 routeirq Do IRQ routing for all PCI devices.
1942 This is normally done in pci_enable_device(),
1943 so this option is a temporary workaround
1944 for broken drivers that don't call it.
1945 skip_isa_align [X86] do not align io start addr, so can
1946 handle more pci cards
1947 firmware [ARM] Do not re-enumerate the bus but instead
1948 just use the configuration from the
1949 bootloader. This is currently used on
1950 IXP2000 systems where the bus has to be
1951 configured a certain way for adjunct CPUs.
1952 noearly [X86] Don't do any early type 1 scanning.
1953 This might help on some broken boards which
1954 machine check when some devices' config space
1955 is read. But various workarounds are disabled
1956 and some IOMMU drivers will not work.
1957 bfsort Sort PCI devices into breadth-first order.
1958 This sorting is done to get a device
1959 order compatible with older (<= 2.4) kernels.
1960 nobfsort Don't sort PCI devices into breadth-first order.
1961 cbiosize=nn[KMG] The fixed amount of bus space which is
1962 reserved for the CardBus bridge's IO window.
1963 The default value is 256 bytes.
1964 cbmemsize=nn[KMG] The fixed amount of bus space which is
1965 reserved for the CardBus bridge's memory
1966 window. The default value is 64 megabytes.
1967 resource_alignment=
1968 Format:
1969 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1970 Specifies alignment and device to reassign
1971 aligned memory resources.
1972 If <order of align> is not specified,
1973 PAGE_SIZE is used as alignment.
1974 PCI-PCI bridge can be specified, if resource
1975 windows need to be expanded.
1976 ecrc= Enable/disable PCIe ECRC (transaction layer
1977 end-to-end CRC checking).
1978 bios: Use BIOS/firmware settings. This is the
1979 the default.
1980 off: Turn ECRC off
1981 on: Turn ECRC on.
1983 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1984 Management.
1985 off Disable ASPM.
1986 force Enable ASPM even on devices that claim not to support it.
1987 WARNING: Forcing ASPM on may cause system lockups.
1989 pcmv= [HW,PCMCIA] BadgePAD 4
1991 pd. [PARIDE]
1992 See Documentation/blockdev/paride.txt.
1994 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1995 boot time.
1996 Format: { 0 | 1 }
1997 See arch/parisc/kernel/pdc_chassis.c
1999 percpu_alloc= Select which percpu first chunk allocator to use.
2000 Currently supported values are "embed" and "page".
2001 Archs may support subset or none of the selections.
2002 See comments in mm/percpu.c for details on each
2003 allocator. This parameter is primarily for debugging
2004 and performance comparison.
2006 pf. [PARIDE]
2007 See Documentation/blockdev/paride.txt.
2009 pg. [PARIDE]
2010 See Documentation/blockdev/paride.txt.
2012 pirq= [SMP,APIC] Manual mp-table setup
2013 See Documentation/x86/i386/IO-APIC.txt.
2015 plip= [PPT,NET] Parallel port network link
2016 Format: { parport<nr> | timid | 0 }
2017 See also Documentation/parport.txt.
2019 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2020 Override pmtimer IOPort with a hex value.
2021 e.g. pmtmr=0x508
2023 pnp.debug [PNP]
2024 Enable PNP debug messages. This depends on the
2025 CONFIG_PNP_DEBUG_MESSAGES option.
2027 pnpacpi= [ACPI]
2028 { off }
2030 pnpbios= [ISAPNP]
2031 { on | off | curr | res | no-curr | no-res }
2033 pnp_reserve_irq=
2034 [ISAPNP] Exclude IRQs for the autoconfiguration
2036 pnp_reserve_dma=
2037 [ISAPNP] Exclude DMAs for the autoconfiguration
2039 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2040 Ranges are in pairs (I/O port base and size).
2042 pnp_reserve_mem=
2043 [ISAPNP] Exclude memory regions for the
2044 autoconfiguration.
2045 Ranges are in pairs (memory base and size).
2047 ports= [IP_VS_FTP] IPVS ftp helper module
2048 Default is 21.
2049 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2050 may be specified.
2051 Format: <port>,<port>....
2053 print-fatal-signals=
2054 [KNL] debug: print fatal signals
2056 If enabled, warn about various signal handling
2057 related application anomalies: too many signals,
2058 too many POSIX.1 timers, fatal signals causing a
2059 coredump - etc.
2061 If you hit the warning due to signal overflow,
2062 you might want to try "ulimit -i unlimited".
2064 default: off.
2066 printk.time= Show timing data prefixed to each printk message line
2067 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2069 processor.max_cstate= [HW,ACPI]
2070 Limit processor to maximum C-state
2071 max_cstate=9 overrides any DMI blacklist limit.
2073 processor.nocst [HW,ACPI]
2074 Ignore the _CST method to determine C-states,
2075 instead using the legacy FADT method
2077 profile= [KNL] Enable kernel profiling via /proc/profile
2078 Format: [schedule,]<number>
2079 Param: "schedule" - profile schedule points.
2080 Param: <number> - step/bucket size as a power of 2 for
2081 statistical time based profiling.
2082 Param: "sleep" - profile D-state sleeping (millisecs).
2083 Requires CONFIG_SCHEDSTATS
2084 Param: "kvm" - profile VM exits.
2086 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2087 before loading.
2088 See Documentation/blockdev/ramdisk.txt.
2090 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2091 probe for; one of (bare|imps|exps|lifebook|any).
2092 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2093 per second.
2094 psmouse.resetafter= [HW,MOUSE]
2095 Try to reset the device after so many bad packets
2096 (0 = never).
2097 psmouse.resolution=
2098 [HW,MOUSE] Set desired mouse resolution, in dpi.
2099 psmouse.smartscroll=
2100 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2101 0 = disabled, 1 = enabled (default).
2103 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2104 Format:
2105 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2107 pt. [PARIDE]
2108 See Documentation/blockdev/paride.txt.
2110 pty.legacy_count=
2111 [KNL] Number of legacy pty's. Overwrites compiled-in
2112 default number.
2114 quiet [KNL] Disable most log messages
2116 r128= [HW,DRM]
2118 raid= [HW,RAID]
2119 See Documentation/md.txt.
2121 ramdisk_blocksize= [RAM]
2122 See Documentation/blockdev/ramdisk.txt.
2124 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2125 See Documentation/blockdev/ramdisk.txt.
2127 rcupdate.blimit= [KNL,BOOT]
2128 Set maximum number of finished RCU callbacks to process
2129 in one batch.
2131 rcupdate.qhimark= [KNL,BOOT]
2132 Set threshold of queued
2133 RCU callbacks over which batch limiting is disabled.
2135 rcupdate.qlowmark= [KNL,BOOT]
2136 Set threshold of queued RCU callbacks below which
2137 batch limiting is re-enabled.
2139 rdinit= [KNL]
2140 Format: <full_path>
2141 Run specified binary instead of /init from the ramdisk,
2142 used for early userspace startup. See initrd.
2144 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2145 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2146 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2148 relax_domain_level=
2149 [KNL, SMP] Set scheduler's default relax_domain_level.
2150 See Documentation/cgroups/cpusets.txt.
2152 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2154 reservetop= [X86-32]
2155 Format: nn[KMG]
2156 Reserves a hole at the top of the kernel virtual
2157 address space.
2159 reset_devices [KNL] Force drivers to reset the underlying device
2160 during initialization.
2162 resume= [SWSUSP]
2163 Specify the partition device for software suspend
2165 resume_offset= [SWSUSP]
2166 Specify the offset from the beginning of the partition
2167 given by "resume=" at which the swap header is located,
2168 in <PAGE_SIZE> units (needed only for swap files).
2169 See Documentation/power/swsusp-and-swap-files.txt
2171 retain_initrd [RAM] Keep initrd memory after extraction
2173 rhash_entries= [KNL,NET]
2174 Set number of hash buckets for route cache
2176 riscom8= [HW,SERIAL]
2177 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2179 ro [KNL] Mount root device read-only on boot
2181 root= [KNL] Root filesystem
2183 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2184 mount the root filesystem
2186 rootflags= [KNL] Set root filesystem mount option string
2188 rootfstype= [KNL] Set root filesystem type
2190 rootwait [KNL] Wait (indefinitely) for root device to show up.
2191 Useful for devices that are detected asynchronously
2192 (e.g. USB and MMC devices).
2194 rw [KNL] Mount root device read-write on boot
2196 S [KNL] Run init in single mode
2198 sa1100ir [NET]
2199 See drivers/net/irda/sa1100_ir.c.
2201 sbni= [NET] Granch SBNI12 leased line adapter
2203 sched_debug [KNL] Enables verbose scheduler debug messages.
2205 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2206 Format: <io>[,<timeout>[,<isapnp>]]
2208 scsi_debug_*= [SCSI]
2209 See drivers/scsi/scsi_debug.c.
2211 scsi_default_dev_flags=
2212 [SCSI] SCSI default device flags
2213 Format: <integer>
2215 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2216 Format: <vendor>:<model>:<flags>
2217 (flags are integer value)
2219 scsi_logging_level= [SCSI] a bit mask of logging levels
2220 See drivers/scsi/scsi_logging.h for bits. Also
2221 settable via sysctl at dev.scsi.logging_level
2222 (/proc/sys/dev/scsi/logging_level).
2223 There is also a nice 'scsi_logging_level' script in the
2224 S390-tools package, available for download at
2225 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2227 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2228 discovered. async scans them in kernel threads,
2229 allowing boot to proceed. none ignores them, expecting
2230 user space to do the scan.
2232 security= [SECURITY] Choose a security module to enable at boot.
2233 If this boot parameter is not specified, only the first
2234 security module asking for security registration will be
2235 loaded. An invalid security module name will be treated
2236 as if no module has been chosen.
2238 selinux= [SELINUX] Disable or enable SELinux at boot time.
2239 Format: { "0" | "1" }
2240 See security/selinux/Kconfig help text.
2241 0 -- disable.
2242 1 -- enable.
2243 Default value is set via kernel config option.
2244 If enabled at boot time, /selinux/disable can be used
2245 later to disable prior to initial policy load.
2247 serialnumber [BUGS=X86-32]
2249 shapers= [NET]
2250 Maximal number of shapers.
2252 show_msr= [x86] show boot-time MSR settings
2253 Format: { <integer> }
2254 Show boot-time (BIOS-initialized) MSR settings.
2255 The parameter means the number of CPUs to show,
2256 for example 1 means boot CPU only.
2258 sim710= [SCSI,HW]
2259 See header of drivers/scsi/sim710.c.
2261 simeth= [IA-64]
2262 simscsi=
2264 slram= [HW,MTD]
2266 slub_debug[=options[,slabs]] [MM, SLUB]
2267 Enabling slub_debug allows one to determine the
2268 culprit if slab objects become corrupted. Enabling
2269 slub_debug can create guard zones around objects and
2270 may poison objects when not in use. Also tracks the
2271 last alloc / free. For more information see
2272 Documentation/vm/slub.txt.
2274 slub_max_order= [MM, SLUB]
2275 Determines the maximum allowed order for slabs.
2276 A high setting may cause OOMs due to memory
2277 fragmentation. For more information see
2278 Documentation/vm/slub.txt.
2280 slub_min_objects= [MM, SLUB]
2281 The minimum number of objects per slab. SLUB will
2282 increase the slab order up to slub_max_order to
2283 generate a sufficiently large slab able to contain
2284 the number of objects indicated. The higher the number
2285 of objects the smaller the overhead of tracking slabs
2286 and the less frequently locks need to be acquired.
2287 For more information see Documentation/vm/slub.txt.
2289 slub_min_order= [MM, SLUB]
2290 Determines the mininum page order for slabs. Must be
2291 lower than slub_max_order.
2292 For more information see Documentation/vm/slub.txt.
2294 slub_nomerge [MM, SLUB]
2295 Disable merging of slabs with similar size. May be
2296 necessary if there is some reason to distinguish
2297 allocs to different slabs. Debug options disable
2298 merging on their own.
2299 For more information see Documentation/vm/slub.txt.
2301 smart2= [HW]
2302 Format: <io1>[,<io2>[,...,<io8>]]
2304 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2305 attempt to substitute SMP alternatives once at boot.
2307 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2308 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2309 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2310 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2311 smsc-ircc2.ircc_irq= [HW] IRQ line
2312 smsc-ircc2.ircc_dma= [HW] DMA channel
2313 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2314 0: Toshiba Satellite 1800 (GP data pin select)
2315 1: Fast pin select (default)
2316 2: ATC IRMode
2318 snd-ad1816a= [HW,ALSA]
2320 snd-ad1848= [HW,ALSA]
2322 snd-ali5451= [HW,ALSA]
2324 snd-als100= [HW,ALSA]
2326 snd-als4000= [HW,ALSA]
2328 snd-azt2320= [HW,ALSA]
2330 snd-cmi8330= [HW,ALSA]
2332 snd-cmipci= [HW,ALSA]
2334 snd-cs4231= [HW,ALSA]
2336 snd-cs4232= [HW,ALSA]
2338 snd-cs4236= [HW,ALSA]
2340 snd-cs4281= [HW,ALSA]
2342 snd-cs46xx= [HW,ALSA]
2344 snd-dt019x= [HW,ALSA]
2346 snd-dummy= [HW,ALSA]
2348 snd-emu10k1= [HW,ALSA]
2350 snd-ens1370= [HW,ALSA]
2352 snd-ens1371= [HW,ALSA]
2354 snd-es968= [HW,ALSA]
2356 snd-es1688= [HW,ALSA]
2358 snd-es18xx= [HW,ALSA]
2360 snd-es1938= [HW,ALSA]
2362 snd-es1968= [HW,ALSA]
2364 snd-fm801= [HW,ALSA]
2366 snd-gusclassic= [HW,ALSA]
2368 snd-gusextreme= [HW,ALSA]
2370 snd-gusmax= [HW,ALSA]
2372 snd-hdsp= [HW,ALSA]
2374 snd-ice1712= [HW,ALSA]
2376 snd-intel8x0= [HW,ALSA]
2378 snd-interwave= [HW,ALSA]
2380 snd-interwave-stb=
2381 [HW,ALSA]
2383 snd-korg1212= [HW,ALSA]
2385 snd-maestro3= [HW,ALSA]
2387 snd-mpu401= [HW,ALSA]
2389 snd-mtpav= [HW,ALSA]
2391 snd-nm256= [HW,ALSA]
2393 snd-opl3sa2= [HW,ALSA]
2395 snd-opti92x-ad1848=
2396 [HW,ALSA]
2398 snd-opti92x-cs4231=
2399 [HW,ALSA]
2401 snd-opti93x= [HW,ALSA]
2403 snd-pmac= [HW,ALSA]
2405 snd-rme32= [HW,ALSA]
2407 snd-rme96= [HW,ALSA]
2409 snd-rme9652= [HW,ALSA]
2411 snd-sb8= [HW,ALSA]
2413 snd-sb16= [HW,ALSA]
2415 snd-sbawe= [HW,ALSA]
2417 snd-serial= [HW,ALSA]
2419 snd-sgalaxy= [HW,ALSA]
2421 snd-sonicvibes= [HW,ALSA]
2423 snd-sun-amd7930=
2424 [HW,ALSA]
2426 snd-sun-cs4231= [HW,ALSA]
2428 snd-trident= [HW,ALSA]
2430 snd-usb-audio= [HW,ALSA,USB]
2432 snd-via82xx= [HW,ALSA]
2434 snd-virmidi= [HW,ALSA]
2436 snd-wavefront= [HW,ALSA]
2438 snd-ymfpci= [HW,ALSA]
2440 softlockup_panic=
2441 [KNL] Should the soft-lockup detector generate panics.
2443 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2444 See Documentation/sonypi.txt
2446 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2447 See Documentation/serial/specialix.txt.
2449 spia_io_base= [HW,MTD]
2450 spia_fio_base=
2451 spia_pedr=
2452 spia_peddr=
2454 sscape= [HW,OSS]
2455 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2457 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2458 See Documentation/scsi/st.txt.
2460 stacktrace [FTRACE]
2461 Enabled the stack tracer on boot up.
2463 sti= [PARISC,HW]
2464 Format: <num>
2465 Set the STI (builtin display/keyboard on the HP-PARISC
2466 machines) console (graphic card) which should be used
2467 as the initial boot-console.
2468 See also comment in drivers/video/console/sticore.c.
2470 sti_font= [HW]
2471 See comment in drivers/video/console/sticore.c.
2473 stifb= [HW]
2474 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2476 sunrpc.min_resvport=
2477 sunrpc.max_resvport=
2478 [NFS,SUNRPC]
2479 SunRPC servers often require that client requests
2480 originate from a privileged port (i.e. a port in the
2481 range 0 < portnr < 1024).
2482 An administrator who wishes to reserve some of these
2483 ports for other uses may adjust the range that the
2484 kernel's sunrpc client considers to be privileged
2485 using these two parameters to set the minimum and
2486 maximum port values.
2488 sunrpc.pool_mode=
2489 [NFS]
2490 Control how the NFS server code allocates CPUs to
2491 service thread pools. Depending on how many NICs
2492 you have and where their interrupts are bound, this
2493 option will affect which CPUs will do NFS serving.
2494 Note: this parameter cannot be changed while the
2495 NFS server is running.
2497 auto the server chooses an appropriate mode
2498 automatically using heuristics
2499 global a single global pool contains all CPUs
2500 percpu one pool for each CPU
2501 pernode one pool for each NUMA node (equivalent
2502 to global on non-NUMA machines)
2504 sunrpc.tcp_slot_table_entries=
2505 sunrpc.udp_slot_table_entries=
2506 [NFS,SUNRPC]
2507 Sets the upper limit on the number of simultaneous
2508 RPC calls that can be sent from the client to a
2509 server. Increasing these values may allow you to
2510 improve throughput, but will also increase the
2511 amount of memory reserved for use by the client.
2513 swiotlb= [IA-64] Number of I/O TLB slabs
2515 switches= [HW,M68k]
2517 sym53c416= [HW,SCSI]
2518 See header of drivers/scsi/sym53c416.c.
2520 sysrq_always_enabled
2521 [KNL]
2522 Ignore sysrq setting - this boot parameter will
2523 neutralize any effect of /proc/sys/kernel/sysrq.
2524 Useful for debugging.
2526 t128= [HW,SCSI]
2527 See header of drivers/scsi/t128.c.
2529 tdfx= [HW,DRM]
2531 test_suspend= [SUSPEND]
2532 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2533 standby suspend) as the system sleep state to briefly
2534 enter during system startup. The system is woken from
2535 this state using a wakeup-capable RTC alarm.
2537 thash_entries= [KNL,NET]
2538 Set number of hash buckets for TCP connection
2540 thermal.act= [HW,ACPI]
2541 -1: disable all active trip points in all thermal zones
2542 <degrees C>: override all lowest active trip points
2544 thermal.crt= [HW,ACPI]
2545 -1: disable all critical trip points in all thermal zones
2546 <degrees C>: override all critical trip points
2548 thermal.nocrt= [HW,ACPI]
2549 Set to disable actions on ACPI thermal zone
2550 critical and hot trip points.
2552 thermal.off= [HW,ACPI]
2553 1: disable ACPI thermal control
2555 thermal.psv= [HW,ACPI]
2556 -1: disable all passive trip points
2557 <degrees C>: override all passive trip points to this
2558 value
2560 thermal.tzp= [HW,ACPI]
2561 Specify global default ACPI thermal zone polling rate
2562 <deci-seconds>: poll all this frequency
2563 0: no polling (default)
2565 tmscsim= [HW,SCSI]
2566 See comment before function dc390_setup() in
2567 drivers/scsi/tmscsim.c.
2569 topology= [S390]
2570 Format: {off | on}
2571 Specify if the kernel should make use of the cpu
2572 topology informations if the hardware supports these.
2573 The scheduler will make use of these informations and
2574 e.g. base its process migration decisions on it.
2575 Default is off.
2577 tp720= [HW,PS2]
2579 trace_buf_size=nn[KMG]
2580 [FTRACE] will set tracing buffer size.
2582 trace_event=[event-list]
2583 [FTRACE] Set and start specified trace events in order
2584 to facilitate early boot debugging.
2585 See also Documentation/trace/events.txt
2587 trix= [HW,OSS] MediaTrix AudioTrix Pro
2588 Format:
2589 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2591 tsc= Disable clocksource-must-verify flag for TSC.
2592 Format: <string>
2593 [x86] reliable: mark tsc clocksource as reliable, this
2594 disables clocksource verification at runtime.
2595 Used to enable high-resolution timer mode on older
2596 hardware, and in virtualized environment.
2598 turbografx.map[2|3]= [HW,JOY]
2599 TurboGraFX parallel port interface
2600 Format:
2601 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2602 See also Documentation/input/joystick-parport.txt
2604 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2605 See header of drivers/scsi/u14-34f.c.
2607 uart401= [HW,OSS]
2608 Format: <io>,<irq>
2610 uart6850= [HW,OSS]
2611 Format: <io>,<irq>
2613 uhash_entries= [KNL,NET]
2614 Set number of hash buckets for UDP/UDP-Lite connections
2616 uhci-hcd.ignore_oc=
2617 [USB] Ignore overcurrent events (default N).
2618 Some badly-designed motherboards generate lots of
2619 bogus events, for ports that aren't wired to
2620 anything. Set this parameter to avoid log spamming.
2621 Note that genuine overcurrent events won't be
2622 reported either.
2624 unknown_nmi_panic
2625 [X86]
2626 Set unknown_nmi_panic=1 early on boot.
2628 usbcore.autosuspend=
2629 [USB] The autosuspend time delay (in seconds) used
2630 for newly-detected USB devices (default 2). This
2631 is the time required before an idle device will be
2632 autosuspended. Devices for which the delay is set
2633 to a negative value won't be autosuspended at all.
2635 usbcore.usbfs_snoop=
2636 [USB] Set to log all usbfs traffic (default 0 = off).
2638 usbcore.blinkenlights=
2639 [USB] Set to cycle leds on hubs (default 0 = off).
2641 usbcore.old_scheme_first=
2642 [USB] Start with the old device initialization
2643 scheme (default 0 = off).
2645 usbcore.use_both_schemes=
2646 [USB] Try the other device initialization scheme
2647 if the first one fails (default 1 = enabled).
2649 usbcore.initial_descriptor_timeout=
2650 [USB] Specifies timeout for the initial 64-byte
2651 USB_REQ_GET_DESCRIPTOR request in milliseconds
2652 (default 5000 = 5.0 seconds).
2654 usbhid.mousepoll=
2655 [USBHID] The interval which mice are to be polled at.
2657 usb-storage.delay_use=
2658 [UMS] The delay in seconds before a new device is
2659 scanned for Logical Units (default 5).
2661 usb-storage.quirks=
2662 [UMS] A list of quirks entries to supplement or
2663 override the built-in unusual_devs list. List
2664 entries are separated by commas. Each entry has
2665 the form VID:PID:Flags where VID and PID are Vendor
2666 and Product ID values (4-digit hex numbers) and
2667 Flags is a set of characters, each corresponding
2668 to a common usb-storage quirk flag as follows:
2669 a = SANE_SENSE (collect more than 18 bytes
2670 of sense data);
2671 b = BAD_SENSE (don't collect more than 18
2672 bytes of sense data);
2673 c = FIX_CAPACITY (decrease the reported
2674 device capacity by one sector);
2675 h = CAPACITY_HEURISTICS (decrease the
2676 reported device capacity by one
2677 sector if the number is odd);
2678 i = IGNORE_DEVICE (don't bind to this
2679 device);
2680 l = NOT_LOCKABLE (don't try to lock and
2681 unlock ejectable media);
2682 m = MAX_SECTORS_64 (don't transfer more
2683 than 64 sectors = 32 KB at a time);
2684 o = CAPACITY_OK (accept the capacity
2685 reported by the device);
2686 r = IGNORE_RESIDUE (the device reports
2687 bogus residue values);
2688 s = SINGLE_LUN (the device has only one
2689 Logical Unit);
2690 w = NO_WP_DETECT (don't test whether the
2691 medium is write-protected).
2692 Example: quirks=0419:aaf5:rl,0421:0433:rc
2694 vdso= [X86,SH]
2695 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2696 vdso=1: enable VDSO (default)
2697 vdso=0: disable VDSO mapping
2699 vdso32= [X86]
2700 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2701 vdso32=1: enable 32-bit VDSO (default)
2702 vdso32=0: disable 32-bit VDSO mapping
2704 vector= [IA-64,SMP]
2705 vector=percpu: enable percpu vector domain
2707 video= [FB] Frame buffer configuration
2708 See Documentation/fb/modedb.txt.
2710 vga= [BOOT,X86-32] Select a particular video mode
2711 See Documentation/x86/boot.txt and
2712 Documentation/svga.txt.
2713 Use vga=ask for menu.
2714 This is actually a boot loader parameter; the value is
2715 passed to the kernel using a special protocol.
2717 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2718 size of <nn>. This can be used to increase the
2719 minimum size (128MB on x86). It can also be used to
2720 decrease the size and leave more room for directly
2721 mapped kernel RAM.
2723 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2724 Format: <command>
2726 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2727 Format: <command>
2729 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2730 Format: <command>
2732 vt.cur_default= [VT] Default cursor shape.
2733 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2734 the parameters of the <Esc>[?A;B;Cc escape sequence;
2735 see VGA-softcursor.txt. Default: 2 = underline.
2737 vt.default_blu= [VT]
2738 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2739 Change the default blue palette of the console.
2740 This is a 16-member array composed of values
2741 ranging from 0-255.
2743 vt.default_grn= [VT]
2744 Format: <green0>,<green1>,<green2>,...,<green15>
2745 Change the default green palette of the console.
2746 This is a 16-member array composed of values
2747 ranging from 0-255.
2749 vt.default_red= [VT]
2750 Format: <red0>,<red1>,<red2>,...,<red15>
2751 Change the default red palette of the console.
2752 This is a 16-member array composed of values
2753 ranging from 0-255.
2755 vt.default_utf8=
2756 [VT]
2757 Format=<0|1>
2758 Set system-wide default UTF-8 mode for all tty's.
2759 Default is 1, i.e. UTF-8 mode is enabled for all
2760 newly opened terminals.
2762 vt.global_cursor_default=
2763 [VT]
2764 Format=<-1|0|1>
2765 Set system-wide default for whether a cursor
2766 is shown on new VTs. Default is -1,
2767 i.e. cursors will be created by default unless
2768 overridden by individual drivers. 0 will hide
2769 cursors, 1 will display them.
2771 waveartist= [HW,OSS]
2772 Format: <io>,<irq>,<dma>,<dma2>
2774 wd33c93= [HW,SCSI]
2775 See header of drivers/scsi/wd33c93.c.
2777 wd7000= [HW,SCSI]
2778 See header of drivers/scsi/wd7000.c.
2780 wdt= [WDT] Watchdog
2781 See Documentation/watchdog/wdt.txt.
2783 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2784 default x2apic cluster mode on platforms
2785 supporting x2apic.
2787 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2788 xd_geo= See header of drivers/block/xd.c.
2790 xirc2ps_cs= [NET,PCMCIA]
2791 Format:
2792 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2794 ______________________________________________________________________
2796 TODO:
2798 Add documentation for ALSA options.
2799 Add more DRM drivers.