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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 opl3= [HW,OSS]
1791 Format: <io>
1793 oprofile.timer= [HW]
1794 Use timer interrupt instead of performance counters
1796 oprofile.cpu_type= Force an oprofile cpu type
1797 This might be useful if you have an older oprofile
1798 userland or if you want common events.
1799 Format: { arch_perfmon }
1800 arch_perfmon: [X86] Force use of architectural
1801 perfmon on Intel CPUs instead of the
1802 CPU specific event set.
1804 osst= [HW,SCSI] SCSI Tape Driver
1805 Format: <buffer_size>,<write_threshold>
1806 See also Documentation/scsi/st.txt.
1808 panic= [KNL] Kernel behaviour on panic
1809 Format: <timeout>
1811 parkbd.port= [HW] Parallel port number the keyboard adapter is
1812 connected to, default is 0.
1813 Format: <parport#>
1814 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1815 0 for XT, 1 for AT (default is AT).
1816 Format: <mode>
1818 parport= [HW,PPT] Specify parallel ports. 0 disables.
1819 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1820 Use 'auto' to force the driver to use any
1821 IRQ/DMA settings detected (the default is to
1822 ignore detected IRQ/DMA settings because of
1823 possible conflicts). You can specify the base
1824 address, IRQ, and DMA settings; IRQ and DMA
1825 should be numbers, or 'auto' (for using detected
1826 settings on that particular port), or 'nofifo'
1827 (to avoid using a FIFO even if it is detected).
1828 Parallel ports are assigned in the order they
1829 are specified on the command line, starting
1830 with parport0.
1832 parport_init_mode= [HW,PPT]
1833 Configure VIA parallel port to operate in
1834 a specific mode. This is necessary on Pegasos
1835 computer where firmware has no options for setting
1836 up parallel port mode and sets it to spp.
1837 Currently this function knows 686a and 8231 chips.
1838 Format: [spp|ps2|epp|ecp|ecpepp]
1840 pas2= [HW,OSS] Format:
1841 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1843 pas16= [HW,SCSI]
1844 See header of drivers/scsi/pas16.c.
1846 pause_on_oops=
1847 Halt all CPUs after the first oops has been printed for
1848 the specified number of seconds. This is to be used if
1849 your oopses keep scrolling off the screen.
1851 pcbit= [HW,ISDN]
1853 pcd. [PARIDE]
1854 See header of drivers/block/paride/pcd.c.
1855 See also Documentation/blockdev/paride.txt.
1857 pci=option[,option...] [PCI] various PCI subsystem options:
1858 earlydump [X86] dump PCI config space before the kernel
1859 changes anything
1860 off [X86] don't probe for the PCI bus
1861 bios [X86-32] force use of PCI BIOS, don't access
1862 the hardware directly. Use this if your machine
1863 has a non-standard PCI host bridge.
1864 nobios [X86-32] disallow use of PCI BIOS, only direct
1865 hardware access methods are allowed. Use this
1866 if you experience crashes upon bootup and you
1867 suspect they are caused by the BIOS.
1868 conf1 [X86] Force use of PCI Configuration
1869 Mechanism 1.
1870 conf2 [X86] Force use of PCI Configuration
1871 Mechanism 2.
1872 noaer [PCIE] If the PCIEAER kernel config parameter is
1873 enabled, this kernel boot option can be used to
1874 disable the use of PCIE advanced error reporting.
1875 nodomains [PCI] Disable support for multiple PCI
1876 root domains (aka PCI segments, in ACPI-speak).
1877 nommconf [X86] Disable use of MMCONFIG for PCI
1878 Configuration
1879 check_enable_amd_mmconf [X86] check for and enable
1880 properly configured MMIO access to PCI
1881 config space on AMD family 10h CPU
1882 nomsi [MSI] If the PCI_MSI kernel config parameter is
1883 enabled, this kernel boot option can be used to
1884 disable the use of MSI interrupts system-wide.
1885 noioapicquirk [APIC] Disable all boot interrupt quirks.
1886 Safety option to keep boot IRQs enabled. This
1887 should never be necessary.
1888 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1889 primary IO-APIC for bridges that cannot disable
1890 boot IRQs. This fixes a source of spurious IRQs
1891 when the system masks IRQs.
1892 noioapicreroute [APIC] Disable workaround that uses the
1893 boot IRQ equivalent of an IRQ that connects to
1894 a chipset where boot IRQs cannot be disabled.
1895 The opposite of ioapicreroute.
1896 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1897 routing table. These calls are known to be buggy
1898 on several machines and they hang the machine
1899 when used, but on other computers it's the only
1900 way to get the interrupt routing table. Try
1901 this option if the kernel is unable to allocate
1902 IRQs or discover secondary PCI buses on your
1903 motherboard.
1904 rom [X86] Assign address space to expansion ROMs.
1905 Use with caution as certain devices share
1906 address decoders between ROMs and other
1907 resources.
1908 norom [X86] Do not assign address space to
1909 expansion ROMs that do not already have
1910 BIOS assigned address ranges.
1911 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1912 assigned automatically to PCI devices. You can
1913 make the kernel exclude IRQs of your ISA cards
1914 this way.
1915 pirqaddr=0xAAAAA [X86] Specify the physical address
1916 of the PIRQ table (normally generated
1917 by the BIOS) if it is outside the
1918 F0000h-100000h range.
1919 lastbus=N [X86] Scan all buses thru bus #N. Can be
1920 useful if the kernel is unable to find your
1921 secondary buses and you want to tell it
1922 explicitly which ones they are.
1923 assign-busses [X86] Always assign all PCI bus
1924 numbers ourselves, overriding
1925 whatever the firmware may have done.
1926 usepirqmask [X86] Honor the possible IRQ mask stored
1927 in the BIOS $PIR table. This is needed on
1928 some systems with broken BIOSes, notably
1929 some HP Pavilion N5400 and Omnibook XE3
1930 notebooks. This will have no effect if ACPI
1931 IRQ routing is enabled.
1932 noacpi [X86] Do not use ACPI for IRQ routing
1933 or for PCI scanning.
1934 use_crs [X86] Use _CRS for PCI resource
1935 allocation.
1936 routeirq Do IRQ routing for all PCI devices.
1937 This is normally done in pci_enable_device(),
1938 so this option is a temporary workaround
1939 for broken drivers that don't call it.
1940 skip_isa_align [X86] do not align io start addr, so can
1941 handle more pci cards
1942 firmware [ARM] Do not re-enumerate the bus but instead
1943 just use the configuration from the
1944 bootloader. This is currently used on
1945 IXP2000 systems where the bus has to be
1946 configured a certain way for adjunct CPUs.
1947 noearly [X86] Don't do any early type 1 scanning.
1948 This might help on some broken boards which
1949 machine check when some devices' config space
1950 is read. But various workarounds are disabled
1951 and some IOMMU drivers will not work.
1952 bfsort Sort PCI devices into breadth-first order.
1953 This sorting is done to get a device
1954 order compatible with older (<= 2.4) kernels.
1955 nobfsort Don't sort PCI devices into breadth-first order.
1956 cbiosize=nn[KMG] The fixed amount of bus space which is
1957 reserved for the CardBus bridge's IO window.
1958 The default value is 256 bytes.
1959 cbmemsize=nn[KMG] The fixed amount of bus space which is
1960 reserved for the CardBus bridge's memory
1961 window. The default value is 64 megabytes.
1962 resource_alignment=
1963 Format:
1964 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1965 Specifies alignment and device to reassign
1966 aligned memory resources.
1967 If <order of align> is not specified,
1968 PAGE_SIZE is used as alignment.
1969 PCI-PCI bridge can be specified, if resource
1970 windows need to be expanded.
1971 ecrc= Enable/disable PCIe ECRC (transaction layer
1972 end-to-end CRC checking).
1973 bios: Use BIOS/firmware settings. This is the
1974 the default.
1975 off: Turn ECRC off
1976 on: Turn ECRC on.
1978 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1979 Management.
1980 off Disable ASPM.
1981 force Enable ASPM even on devices that claim not to support it.
1982 WARNING: Forcing ASPM on may cause system lockups.
1984 pcmv= [HW,PCMCIA] BadgePAD 4
1986 pd. [PARIDE]
1987 See Documentation/blockdev/paride.txt.
1989 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1990 boot time.
1991 Format: { 0 | 1 }
1992 See arch/parisc/kernel/pdc_chassis.c
1994 percpu_alloc= Select which percpu first chunk allocator to use.
1995 Currently supported values are "embed" and "page".
1996 Archs may support subset or none of the selections.
1997 See comments in mm/percpu.c for details on each
1998 allocator. This parameter is primarily for debugging
1999 and performance comparison.
2001 pf. [PARIDE]
2002 See Documentation/blockdev/paride.txt.
2004 pg. [PARIDE]
2005 See Documentation/blockdev/paride.txt.
2007 pirq= [SMP,APIC] Manual mp-table setup
2008 See Documentation/x86/i386/IO-APIC.txt.
2010 plip= [PPT,NET] Parallel port network link
2011 Format: { parport<nr> | timid | 0 }
2012 See also Documentation/parport.txt.
2014 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2015 Override pmtimer IOPort with a hex value.
2016 e.g. pmtmr=0x508
2018 pnp.debug [PNP]
2019 Enable PNP debug messages. This depends on the
2020 CONFIG_PNP_DEBUG_MESSAGES option.
2022 pnpacpi= [ACPI]
2023 { off }
2025 pnpbios= [ISAPNP]
2026 { on | off | curr | res | no-curr | no-res }
2028 pnp_reserve_irq=
2029 [ISAPNP] Exclude IRQs for the autoconfiguration
2031 pnp_reserve_dma=
2032 [ISAPNP] Exclude DMAs for the autoconfiguration
2034 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2035 Ranges are in pairs (I/O port base and size).
2037 pnp_reserve_mem=
2038 [ISAPNP] Exclude memory regions for the
2039 autoconfiguration.
2040 Ranges are in pairs (memory base and size).
2042 ports= [IP_VS_FTP] IPVS ftp helper module
2043 Default is 21.
2044 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2045 may be specified.
2046 Format: <port>,<port>....
2048 print-fatal-signals=
2049 [KNL] debug: print fatal signals
2051 If enabled, warn about various signal handling
2052 related application anomalies: too many signals,
2053 too many POSIX.1 timers, fatal signals causing a
2054 coredump - etc.
2056 If you hit the warning due to signal overflow,
2057 you might want to try "ulimit -i unlimited".
2059 default: off.
2061 printk.time= Show timing data prefixed to each printk message line
2062 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2064 processor.max_cstate= [HW,ACPI]
2065 Limit processor to maximum C-state
2066 max_cstate=9 overrides any DMI blacklist limit.
2068 processor.nocst [HW,ACPI]
2069 Ignore the _CST method to determine C-states,
2070 instead using the legacy FADT method
2072 profile= [KNL] Enable kernel profiling via /proc/profile
2073 Format: [schedule,]<number>
2074 Param: "schedule" - profile schedule points.
2075 Param: <number> - step/bucket size as a power of 2 for
2076 statistical time based profiling.
2077 Param: "sleep" - profile D-state sleeping (millisecs).
2078 Requires CONFIG_SCHEDSTATS
2079 Param: "kvm" - profile VM exits.
2081 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2082 before loading.
2083 See Documentation/blockdev/ramdisk.txt.
2085 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2086 probe for; one of (bare|imps|exps|lifebook|any).
2087 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2088 per second.
2089 psmouse.resetafter= [HW,MOUSE]
2090 Try to reset the device after so many bad packets
2091 (0 = never).
2092 psmouse.resolution=
2093 [HW,MOUSE] Set desired mouse resolution, in dpi.
2094 psmouse.smartscroll=
2095 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2096 0 = disabled, 1 = enabled (default).
2098 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2099 Format:
2100 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2102 pt. [PARIDE]
2103 See Documentation/blockdev/paride.txt.
2105 pty.legacy_count=
2106 [KNL] Number of legacy pty's. Overwrites compiled-in
2107 default number.
2109 quiet [KNL] Disable most log messages
2111 r128= [HW,DRM]
2113 raid= [HW,RAID]
2114 See Documentation/md.txt.
2116 ramdisk_blocksize= [RAM]
2117 See Documentation/blockdev/ramdisk.txt.
2119 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2120 See Documentation/blockdev/ramdisk.txt.
2122 rcupdate.blimit= [KNL,BOOT]
2123 Set maximum number of finished RCU callbacks to process
2124 in one batch.
2126 rcupdate.qhimark= [KNL,BOOT]
2127 Set threshold of queued
2128 RCU callbacks over which batch limiting is disabled.
2130 rcupdate.qlowmark= [KNL,BOOT]
2131 Set threshold of queued RCU callbacks below which
2132 batch limiting is re-enabled.
2134 rdinit= [KNL]
2135 Format: <full_path>
2136 Run specified binary instead of /init from the ramdisk,
2137 used for early userspace startup. See initrd.
2139 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2140 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2141 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2143 relax_domain_level=
2144 [KNL, SMP] Set scheduler's default relax_domain_level.
2145 See Documentation/cgroups/cpusets.txt.
2147 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2149 reservetop= [X86-32]
2150 Format: nn[KMG]
2151 Reserves a hole at the top of the kernel virtual
2152 address space.
2154 reset_devices [KNL] Force drivers to reset the underlying device
2155 during initialization.
2157 resume= [SWSUSP]
2158 Specify the partition device for software suspend
2160 resume_offset= [SWSUSP]
2161 Specify the offset from the beginning of the partition
2162 given by "resume=" at which the swap header is located,
2163 in <PAGE_SIZE> units (needed only for swap files).
2164 See Documentation/power/swsusp-and-swap-files.txt
2166 retain_initrd [RAM] Keep initrd memory after extraction
2168 rhash_entries= [KNL,NET]
2169 Set number of hash buckets for route cache
2171 riscom8= [HW,SERIAL]
2172 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2174 ro [KNL] Mount root device read-only on boot
2176 root= [KNL] Root filesystem
2178 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2179 mount the root filesystem
2181 rootflags= [KNL] Set root filesystem mount option string
2183 rootfstype= [KNL] Set root filesystem type
2185 rootwait [KNL] Wait (indefinitely) for root device to show up.
2186 Useful for devices that are detected asynchronously
2187 (e.g. USB and MMC devices).
2189 rw [KNL] Mount root device read-write on boot
2191 S [KNL] Run init in single mode
2193 sa1100ir [NET]
2194 See drivers/net/irda/sa1100_ir.c.
2196 sbni= [NET] Granch SBNI12 leased line adapter
2198 sched_debug [KNL] Enables verbose scheduler debug messages.
2200 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2201 Format: <io>[,<timeout>[,<isapnp>]]
2203 scsi_debug_*= [SCSI]
2204 See drivers/scsi/scsi_debug.c.
2206 scsi_default_dev_flags=
2207 [SCSI] SCSI default device flags
2208 Format: <integer>
2210 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2211 Format: <vendor>:<model>:<flags>
2212 (flags are integer value)
2214 scsi_logging_level= [SCSI] a bit mask of logging levels
2215 See drivers/scsi/scsi_logging.h for bits. Also
2216 settable via sysctl at dev.scsi.logging_level
2217 (/proc/sys/dev/scsi/logging_level).
2218 There is also a nice 'scsi_logging_level' script in the
2219 S390-tools package, available for download at
2220 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2222 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2223 discovered. async scans them in kernel threads,
2224 allowing boot to proceed. none ignores them, expecting
2225 user space to do the scan.
2227 security= [SECURITY] Choose a security module to enable at boot.
2228 If this boot parameter is not specified, only the first
2229 security module asking for security registration will be
2230 loaded. An invalid security module name will be treated
2231 as if no module has been chosen.
2233 selinux= [SELINUX] Disable or enable SELinux at boot time.
2234 Format: { "0" | "1" }
2235 See security/selinux/Kconfig help text.
2236 0 -- disable.
2237 1 -- enable.
2238 Default value is set via kernel config option.
2239 If enabled at boot time, /selinux/disable can be used
2240 later to disable prior to initial policy load.
2242 serialnumber [BUGS=X86-32]
2244 shapers= [NET]
2245 Maximal number of shapers.
2247 show_msr= [x86] show boot-time MSR settings
2248 Format: { <integer> }
2249 Show boot-time (BIOS-initialized) MSR settings.
2250 The parameter means the number of CPUs to show,
2251 for example 1 means boot CPU only.
2253 sim710= [SCSI,HW]
2254 See header of drivers/scsi/sim710.c.
2256 simeth= [IA-64]
2257 simscsi=
2259 slram= [HW,MTD]
2261 slub_debug[=options[,slabs]] [MM, SLUB]
2262 Enabling slub_debug allows one to determine the
2263 culprit if slab objects become corrupted. Enabling
2264 slub_debug can create guard zones around objects and
2265 may poison objects when not in use. Also tracks the
2266 last alloc / free. For more information see
2267 Documentation/vm/slub.txt.
2269 slub_max_order= [MM, SLUB]
2270 Determines the maximum allowed order for slabs.
2271 A high setting may cause OOMs due to memory
2272 fragmentation. For more information see
2273 Documentation/vm/slub.txt.
2275 slub_min_objects= [MM, SLUB]
2276 The minimum number of objects per slab. SLUB will
2277 increase the slab order up to slub_max_order to
2278 generate a sufficiently large slab able to contain
2279 the number of objects indicated. The higher the number
2280 of objects the smaller the overhead of tracking slabs
2281 and the less frequently locks need to be acquired.
2282 For more information see Documentation/vm/slub.txt.
2284 slub_min_order= [MM, SLUB]
2285 Determines the mininum page order for slabs. Must be
2286 lower than slub_max_order.
2287 For more information see Documentation/vm/slub.txt.
2289 slub_nomerge [MM, SLUB]
2290 Disable merging of slabs with similar size. May be
2291 necessary if there is some reason to distinguish
2292 allocs to different slabs. Debug options disable
2293 merging on their own.
2294 For more information see Documentation/vm/slub.txt.
2296 smart2= [HW]
2297 Format: <io1>[,<io2>[,...,<io8>]]
2299 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2300 attempt to substitute SMP alternatives once at boot.
2302 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2303 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2304 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2305 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2306 smsc-ircc2.ircc_irq= [HW] IRQ line
2307 smsc-ircc2.ircc_dma= [HW] DMA channel
2308 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2309 0: Toshiba Satellite 1800 (GP data pin select)
2310 1: Fast pin select (default)
2311 2: ATC IRMode
2313 snd-ad1816a= [HW,ALSA]
2315 snd-ad1848= [HW,ALSA]
2317 snd-ali5451= [HW,ALSA]
2319 snd-als100= [HW,ALSA]
2321 snd-als4000= [HW,ALSA]
2323 snd-azt2320= [HW,ALSA]
2325 snd-cmi8330= [HW,ALSA]
2327 snd-cmipci= [HW,ALSA]
2329 snd-cs4231= [HW,ALSA]
2331 snd-cs4232= [HW,ALSA]
2333 snd-cs4236= [HW,ALSA]
2335 snd-cs4281= [HW,ALSA]
2337 snd-cs46xx= [HW,ALSA]
2339 snd-dt019x= [HW,ALSA]
2341 snd-dummy= [HW,ALSA]
2343 snd-emu10k1= [HW,ALSA]
2345 snd-ens1370= [HW,ALSA]
2347 snd-ens1371= [HW,ALSA]
2349 snd-es968= [HW,ALSA]
2351 snd-es1688= [HW,ALSA]
2353 snd-es18xx= [HW,ALSA]
2355 snd-es1938= [HW,ALSA]
2357 snd-es1968= [HW,ALSA]
2359 snd-fm801= [HW,ALSA]
2361 snd-gusclassic= [HW,ALSA]
2363 snd-gusextreme= [HW,ALSA]
2365 snd-gusmax= [HW,ALSA]
2367 snd-hdsp= [HW,ALSA]
2369 snd-ice1712= [HW,ALSA]
2371 snd-intel8x0= [HW,ALSA]
2373 snd-interwave= [HW,ALSA]
2375 snd-interwave-stb=
2376 [HW,ALSA]
2378 snd-korg1212= [HW,ALSA]
2380 snd-maestro3= [HW,ALSA]
2382 snd-mpu401= [HW,ALSA]
2384 snd-mtpav= [HW,ALSA]
2386 snd-nm256= [HW,ALSA]
2388 snd-opl3sa2= [HW,ALSA]
2390 snd-opti92x-ad1848=
2391 [HW,ALSA]
2393 snd-opti92x-cs4231=
2394 [HW,ALSA]
2396 snd-opti93x= [HW,ALSA]
2398 snd-pmac= [HW,ALSA]
2400 snd-rme32= [HW,ALSA]
2402 snd-rme96= [HW,ALSA]
2404 snd-rme9652= [HW,ALSA]
2406 snd-sb8= [HW,ALSA]
2408 snd-sb16= [HW,ALSA]
2410 snd-sbawe= [HW,ALSA]
2412 snd-serial= [HW,ALSA]
2414 snd-sgalaxy= [HW,ALSA]
2416 snd-sonicvibes= [HW,ALSA]
2418 snd-sun-amd7930=
2419 [HW,ALSA]
2421 snd-sun-cs4231= [HW,ALSA]
2423 snd-trident= [HW,ALSA]
2425 snd-usb-audio= [HW,ALSA,USB]
2427 snd-via82xx= [HW,ALSA]
2429 snd-virmidi= [HW,ALSA]
2431 snd-wavefront= [HW,ALSA]
2433 snd-ymfpci= [HW,ALSA]
2435 softlockup_panic=
2436 [KNL] Should the soft-lockup detector generate panics.
2438 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2439 See Documentation/sonypi.txt
2441 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2442 See Documentation/serial/specialix.txt.
2444 spia_io_base= [HW,MTD]
2445 spia_fio_base=
2446 spia_pedr=
2447 spia_peddr=
2449 sscape= [HW,OSS]
2450 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2452 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2453 See Documentation/scsi/st.txt.
2455 stacktrace [FTRACE]
2456 Enabled the stack tracer on boot up.
2458 sti= [PARISC,HW]
2459 Format: <num>
2460 Set the STI (builtin display/keyboard on the HP-PARISC
2461 machines) console (graphic card) which should be used
2462 as the initial boot-console.
2463 See also comment in drivers/video/console/sticore.c.
2465 sti_font= [HW]
2466 See comment in drivers/video/console/sticore.c.
2468 stifb= [HW]
2469 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2471 sunrpc.min_resvport=
2472 sunrpc.max_resvport=
2473 [NFS,SUNRPC]
2474 SunRPC servers often require that client requests
2475 originate from a privileged port (i.e. a port in the
2476 range 0 < portnr < 1024).
2477 An administrator who wishes to reserve some of these
2478 ports for other uses may adjust the range that the
2479 kernel's sunrpc client considers to be privileged
2480 using these two parameters to set the minimum and
2481 maximum port values.
2483 sunrpc.pool_mode=
2484 [NFS]
2485 Control how the NFS server code allocates CPUs to
2486 service thread pools. Depending on how many NICs
2487 you have and where their interrupts are bound, this
2488 option will affect which CPUs will do NFS serving.
2489 Note: this parameter cannot be changed while the
2490 NFS server is running.
2492 auto the server chooses an appropriate mode
2493 automatically using heuristics
2494 global a single global pool contains all CPUs
2495 percpu one pool for each CPU
2496 pernode one pool for each NUMA node (equivalent
2497 to global on non-NUMA machines)
2499 sunrpc.tcp_slot_table_entries=
2500 sunrpc.udp_slot_table_entries=
2501 [NFS,SUNRPC]
2502 Sets the upper limit on the number of simultaneous
2503 RPC calls that can be sent from the client to a
2504 server. Increasing these values may allow you to
2505 improve throughput, but will also increase the
2506 amount of memory reserved for use by the client.
2508 swiotlb= [IA-64] Number of I/O TLB slabs
2510 switches= [HW,M68k]
2512 sym53c416= [HW,SCSI]
2513 See header of drivers/scsi/sym53c416.c.
2515 sysrq_always_enabled
2516 [KNL]
2517 Ignore sysrq setting - this boot parameter will
2518 neutralize any effect of /proc/sys/kernel/sysrq.
2519 Useful for debugging.
2521 t128= [HW,SCSI]
2522 See header of drivers/scsi/t128.c.
2524 tdfx= [HW,DRM]
2526 test_suspend= [SUSPEND]
2527 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2528 standby suspend) as the system sleep state to briefly
2529 enter during system startup. The system is woken from
2530 this state using a wakeup-capable RTC alarm.
2532 thash_entries= [KNL,NET]
2533 Set number of hash buckets for TCP connection
2535 thermal.act= [HW,ACPI]
2536 -1: disable all active trip points in all thermal zones
2537 <degrees C>: override all lowest active trip points
2539 thermal.crt= [HW,ACPI]
2540 -1: disable all critical trip points in all thermal zones
2541 <degrees C>: override all critical trip points
2543 thermal.nocrt= [HW,ACPI]
2544 Set to disable actions on ACPI thermal zone
2545 critical and hot trip points.
2547 thermal.off= [HW,ACPI]
2548 1: disable ACPI thermal control
2550 thermal.psv= [HW,ACPI]
2551 -1: disable all passive trip points
2552 <degrees C>: override all passive trip points to this
2553 value
2555 thermal.tzp= [HW,ACPI]
2556 Specify global default ACPI thermal zone polling rate
2557 <deci-seconds>: poll all this frequency
2558 0: no polling (default)
2560 tmscsim= [HW,SCSI]
2561 See comment before function dc390_setup() in
2562 drivers/scsi/tmscsim.c.
2564 topology= [S390]
2565 Format: {off | on}
2566 Specify if the kernel should make use of the cpu
2567 topology informations if the hardware supports these.
2568 The scheduler will make use of these informations and
2569 e.g. base its process migration decisions on it.
2570 Default is off.
2572 tp720= [HW,PS2]
2574 trace_buf_size=nn[KMG]
2575 [FTRACE] will set tracing buffer size.
2577 trace_event=[event-list]
2578 [FTRACE] Set and start specified trace events in order
2579 to facilitate early boot debugging.
2580 See also Documentation/trace/events.txt
2582 trix= [HW,OSS] MediaTrix AudioTrix Pro
2583 Format:
2584 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2586 tsc= Disable clocksource-must-verify flag for TSC.
2587 Format: <string>
2588 [x86] reliable: mark tsc clocksource as reliable, this
2589 disables clocksource verification at runtime.
2590 Used to enable high-resolution timer mode on older
2591 hardware, and in virtualized environment.
2593 turbografx.map[2|3]= [HW,JOY]
2594 TurboGraFX parallel port interface
2595 Format:
2596 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2597 See also Documentation/input/joystick-parport.txt
2599 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2600 See header of drivers/scsi/u14-34f.c.
2602 uart401= [HW,OSS]
2603 Format: <io>,<irq>
2605 uart6850= [HW,OSS]
2606 Format: <io>,<irq>
2608 uhash_entries= [KNL,NET]
2609 Set number of hash buckets for UDP/UDP-Lite connections
2611 uhci-hcd.ignore_oc=
2612 [USB] Ignore overcurrent events (default N).
2613 Some badly-designed motherboards generate lots of
2614 bogus events, for ports that aren't wired to
2615 anything. Set this parameter to avoid log spamming.
2616 Note that genuine overcurrent events won't be
2617 reported either.
2619 unknown_nmi_panic
2620 [X86]
2621 Set unknown_nmi_panic=1 early on boot.
2623 usbcore.autosuspend=
2624 [USB] The autosuspend time delay (in seconds) used
2625 for newly-detected USB devices (default 2). This
2626 is the time required before an idle device will be
2627 autosuspended. Devices for which the delay is set
2628 to a negative value won't be autosuspended at all.
2630 usbcore.usbfs_snoop=
2631 [USB] Set to log all usbfs traffic (default 0 = off).
2633 usbcore.blinkenlights=
2634 [USB] Set to cycle leds on hubs (default 0 = off).
2636 usbcore.old_scheme_first=
2637 [USB] Start with the old device initialization
2638 scheme (default 0 = off).
2640 usbcore.use_both_schemes=
2641 [USB] Try the other device initialization scheme
2642 if the first one fails (default 1 = enabled).
2644 usbcore.initial_descriptor_timeout=
2645 [USB] Specifies timeout for the initial 64-byte
2646 USB_REQ_GET_DESCRIPTOR request in milliseconds
2647 (default 5000 = 5.0 seconds).
2649 usbhid.mousepoll=
2650 [USBHID] The interval which mice are to be polled at.
2652 usb-storage.delay_use=
2653 [UMS] The delay in seconds before a new device is
2654 scanned for Logical Units (default 5).
2656 usb-storage.quirks=
2657 [UMS] A list of quirks entries to supplement or
2658 override the built-in unusual_devs list. List
2659 entries are separated by commas. Each entry has
2660 the form VID:PID:Flags where VID and PID are Vendor
2661 and Product ID values (4-digit hex numbers) and
2662 Flags is a set of characters, each corresponding
2663 to a common usb-storage quirk flag as follows:
2664 a = SANE_SENSE (collect more than 18 bytes
2665 of sense data);
2666 c = FIX_CAPACITY (decrease the reported
2667 device capacity by one sector);
2668 h = CAPACITY_HEURISTICS (decrease the
2669 reported device capacity by one
2670 sector if the number is odd);
2671 i = IGNORE_DEVICE (don't bind to this
2672 device);
2673 l = NOT_LOCKABLE (don't try to lock and
2674 unlock ejectable media);
2675 m = MAX_SECTORS_64 (don't transfer more
2676 than 64 sectors = 32 KB at a time);
2677 o = CAPACITY_OK (accept the capacity
2678 reported by the device);
2679 r = IGNORE_RESIDUE (the device reports
2680 bogus residue values);
2681 s = SINGLE_LUN (the device has only one
2682 Logical Unit);
2683 w = NO_WP_DETECT (don't test whether the
2684 medium is write-protected).
2685 Example: quirks=0419:aaf5:rl,0421:0433:rc
2687 vdso= [X86,SH]
2688 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2689 vdso=1: enable VDSO (default)
2690 vdso=0: disable VDSO mapping
2692 vdso32= [X86]
2693 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2694 vdso32=1: enable 32-bit VDSO (default)
2695 vdso32=0: disable 32-bit VDSO mapping
2697 vector= [IA-64,SMP]
2698 vector=percpu: enable percpu vector domain
2700 video= [FB] Frame buffer configuration
2701 See Documentation/fb/modedb.txt.
2703 vga= [BOOT,X86-32] Select a particular video mode
2704 See Documentation/x86/boot.txt and
2705 Documentation/svga.txt.
2706 Use vga=ask for menu.
2707 This is actually a boot loader parameter; the value is
2708 passed to the kernel using a special protocol.
2710 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2711 size of <nn>. This can be used to increase the
2712 minimum size (128MB on x86). It can also be used to
2713 decrease the size and leave more room for directly
2714 mapped kernel RAM.
2716 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2717 Format: <command>
2719 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2720 Format: <command>
2722 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2723 Format: <command>
2725 vt.default_blu= [VT]
2726 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2727 Change the default blue palette of the console.
2728 This is a 16-member array composed of values
2729 ranging from 0-255.
2731 vt.default_grn= [VT]
2732 Format: <green0>,<green1>,<green2>,...,<green15>
2733 Change the default green palette of the console.
2734 This is a 16-member array composed of values
2735 ranging from 0-255.
2737 vt.default_red= [VT]
2738 Format: <red0>,<red1>,<red2>,...,<red15>
2739 Change the default red palette of the console.
2740 This is a 16-member array composed of values
2741 ranging from 0-255.
2743 vt.default_utf8=
2744 [VT]
2745 Format=<0|1>
2746 Set system-wide default UTF-8 mode for all tty's.
2747 Default is 1, i.e. UTF-8 mode is enabled for all
2748 newly opened terminals.
2750 waveartist= [HW,OSS]
2751 Format: <io>,<irq>,<dma>,<dma2>
2753 wd33c93= [HW,SCSI]
2754 See header of drivers/scsi/wd33c93.c.
2756 wd7000= [HW,SCSI]
2757 See header of drivers/scsi/wd7000.c.
2759 wdt= [WDT] Watchdog
2760 See Documentation/watchdog/wdt.txt.
2762 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2763 default x2apic cluster mode on platforms
2764 supporting x2apic.
2766 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2767 xd_geo= See header of drivers/block/xd.c.
2769 xirc2ps_cs= [NET,PCMCIA]
2770 Format:
2771 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2773 ______________________________________________________________________
2775 TODO:
2777 Add documentation for ALSA options.
2778 Add more DRM drivers.