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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, sci_force_enable }
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.
256 sci_force_enable causes the kernel to set SCI_EN directly
257 on resume from S1/S3 (which is against the ACPI spec,
258 but some broken systems don't work without it).
260 acpi_use_timer_override [HW,ACPI]
261 Use timer override. For some broken Nvidia NF5 boards
262 that require a timer override, but don't have HPET
264 acpi_enforce_resources= [ACPI]
265 { strict | lax | no }
266 Check for resource conflicts between native drivers
267 and ACPI OperationRegions (SystemIO and SystemMemory
268 only). IO ports and memory declared in ACPI might be
269 used by the ACPI subsystem in arbitrary AML code and
270 can interfere with legacy drivers.
271 strict (default): access to resources claimed by ACPI
272 is denied; legacy drivers trying to access reserved
273 resources will fail to bind to device using them.
274 lax: access to resources claimed by ACPI is allowed;
275 legacy drivers trying to access reserved resources
276 will bind successfully but a warning message is logged.
277 no: ACPI OperationRegions are not marked as reserved,
278 no further checks are performed.
280 ad1848= [HW,OSS]
281 Format: <io>,<irq>,<dma>,<dma2>,<type>
283 add_efi_memmap [EFI; X86] Include EFI memory map in
284 kernel's map of available physical RAM.
286 advansys= [HW,SCSI]
287 See header of drivers/scsi/advansys.c.
289 advwdt= [HW,WDT] Advantech WDT
290 Format: <iostart>,<iostop>
292 aedsp16= [HW,OSS] Audio Excel DSP 16
293 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
294 See also header of sound/oss/aedsp16.c.
296 agp= [AGP]
297 { off | try_unsupported }
298 off: disable AGP support
299 try_unsupported: try to drive unsupported chipsets
300 (may crash computer or cause data corruption)
302 aha152x= [HW,SCSI]
303 See Documentation/scsi/aha152x.txt.
305 aha1542= [HW,SCSI]
306 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
308 aic7xxx= [HW,SCSI]
309 See Documentation/scsi/aic7xxx.txt.
311 aic79xx= [HW,SCSI]
312 See Documentation/scsi/aic79xx.txt.
314 amd_iommu= [HW,X86-84]
315 Pass parameters to the AMD IOMMU driver in the system.
316 Possible values are:
317 isolate - enable device isolation (each device, as far
318 as possible, will get its own protection
319 domain) [default]
320 share - put every device behind one IOMMU into the
321 same protection domain
322 fullflush - enable flushing of IO/TLB entries when
323 they are unmapped. Otherwise they are
324 flushed before they will be reused, which
325 is a lot of faster
327 amijoy.map= [HW,JOY] Amiga joystick support
328 Map of devices attached to JOY0DAT and JOY1DAT
329 Format: <a>,<b>
330 See also Documentation/kernel/input/joystick.txt
332 analog.map= [HW,JOY] Analog joystick and gamepad support
333 Specifies type or capabilities of an analog joystick
334 connected to one of 16 gameports
335 Format: <type1>,<type2>,..<type16>
337 apc= [HW,SPARC]
338 Power management functions (SPARCstation-4/5 + deriv.)
339 Format: noidle
340 Disable APC CPU standby support. SPARCstation-Fox does
341 not play well with APC CPU idle - disable it if you have
342 APC and your system crashes randomly.
344 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
345 Change the output verbosity whilst booting
346 Format: { quiet (default) | verbose | debug }
347 Change the amount of debugging information output
348 when initialising the APIC and IO-APIC components.
350 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
351 Limit apic dumping. The parameter defines the maximal
352 number of local apics being dumped. Also it is possible
353 to set it to "all" by meaning -- no limit here.
354 Format: { 1 (default) | 2 | ... | all }.
355 The parameter valid if only apic=debug or
356 apic=verbose is specified.
357 Example: apic=debug show_lapic=all
359 apm= [APM] Advanced Power Management
360 See header of arch/x86/kernel/apm_32.c.
362 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
363 Format: <io>,<irq>,<nodeID>
365 ataflop= [HW,M68k]
367 atarimouse= [HW,MOUSE] Atari Mouse
369 atascsi= [HW,SCSI] Atari SCSI
371 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
372 EzKey and similar keyboards
374 atkbd.reset= [HW] Reset keyboard during initialization
376 atkbd.set= [HW] Select keyboard code set
377 Format: <int> (2 = AT (default), 3 = PS/2)
379 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
380 keyboards
382 atkbd.softraw= [HW] Choose between synthetic and real raw mode
383 Format: <bool> (0 = real, 1 = synthetic (default))
385 atkbd.softrepeat= [HW]
386 Use software keyboard repeat
388 autotest [IA64]
390 baycom_epp= [HW,AX25]
391 Format: <io>,<mode>
393 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
394 Format: <io>,<mode>
395 See header of drivers/net/hamradio/baycom_par.c.
397 baycom_ser_fdx= [HW,AX25]
398 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
399 Format: <io>,<irq>,<mode>[,<baud>]
400 See header of drivers/net/hamradio/baycom_ser_fdx.c.
402 baycom_ser_hdx= [HW,AX25]
403 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
404 Format: <io>,<irq>,<mode>
405 See header of drivers/net/hamradio/baycom_ser_hdx.c.
407 boot_delay= Milliseconds to delay each printk during boot.
408 Values larger than 10 seconds (10000) are changed to
409 no delay (0).
410 Format: integer
412 bootmem_debug [KNL] Enable bootmem allocator debug messages.
414 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
415 bttv.radio= Most important insmod options are available as
416 kernel args too.
417 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
418 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
420 BusLogic= [HW,SCSI]
421 See drivers/scsi/BusLogic.c, comment before function
422 BusLogic_ParseDriverOptions().
424 c101= [NET] Moxa C101 synchronous serial card
426 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
427 Sometimes CPU hardware bugs make them report the cache
428 size incorrectly. The kernel will attempt work arounds
429 to fix known problems, but for some CPUs it is not
430 possible to determine what the correct size should be.
431 This option provides an override for these situations.
433 capability.disable=
434 [SECURITY] Disable capabilities. This would normally
435 be used only if an alternative security model is to be
436 configured. Potentially dangerous and should only be
437 used if you are entirely sure of the consequences.
439 ccw_timeout_log [S390]
440 See Documentation/s390/CommonIO for details.
442 cgroup_disable= [KNL] Disable a particular controller
443 Format: {name of the controller(s) to disable}
444 {Currently supported controllers - "memory"}
446 checkreqprot [SELINUX] Set initial checkreqprot flag value.
447 Format: { "0" | "1" }
448 See security/selinux/Kconfig help text.
449 0 -- check protection applied by kernel (includes
450 any implied execute protection).
451 1 -- check protection requested by application.
452 Default value is set via a kernel config option.
453 Value can be changed at runtime via
454 /selinux/checkreqprot.
456 cio_ignore= [S390]
457 See Documentation/s390/CommonIO for details.
459 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
460 [Deprecated]
461 Forces specified clocksource (if available) to be used
462 when calculating gettimeofday(). If specified
463 clocksource is not available, it defaults to PIT.
464 Format: { pit | tsc | cyclone | pmtmr }
466 clocksource= [GENERIC_TIME] Override the default clocksource
467 Format: <string>
468 Override the default clocksource and use the clocksource
469 with the name specified.
470 Some clocksource names to choose from, depending on
471 the platform:
472 [all] jiffies (this is the base, fallback clocksource)
473 [ACPI] acpi_pm
474 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
475 pxa_timer,timer3,32k_counter,timer0_1
476 [AVR32] avr32
477 [X86-32] pit,hpet,tsc,vmi-timer;
478 scx200_hrt on Geode; cyclone on IBM x440
479 [MIPS] MIPS
480 [PARISC] cr16
481 [S390] tod
482 [SH] SuperH
483 [SPARC64] tick
484 [X86-64] hpet,tsc
486 clearcpuid=BITNUM [X86]
487 Disable CPUID feature X for the kernel. See
488 arch/x86/include/asm/cpufeature.h for the valid bit
489 numbers. Note the Linux specific bits are not necessarily
490 stable over kernel options, but the vendor specific
491 ones should be.
492 Also note that user programs calling CPUID directly
493 or using the feature without checking anything
494 will still see it. This just prevents it from
495 being used by the kernel or shown in /proc/cpuinfo.
496 Also note the kernel might malfunction if you disable
497 some critical bits.
499 cmo_free_hint= [PPC] Format: { yes | no }
500 Specify whether pages are marked as being inactive
501 when they are freed. This is used in CMO environments
502 to determine OS memory pressure for page stealing by
503 a hypervisor.
504 Default: yes
506 code_bytes [X86] How many bytes of object code to print
507 in an oops report.
508 Range: 0 - 8192
509 Default: 64
511 com20020= [HW,NET] ARCnet - COM20020 chipset
512 Format:
513 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
515 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
516 Format: <io>[,<irq>]
518 com90xx= [HW,NET]
519 ARCnet - COM90xx chipset (memory-mapped buffers)
520 Format: <io>[,<irq>[,<memstart>]]
522 condev= [HW,S390] console device
523 conmode=
525 console= [KNL] Output console device and options.
527 tty<n> Use the virtual console device <n>.
529 ttyS<n>[,options]
530 ttyUSB0[,options]
531 Use the specified serial port. The options are of
532 the form "bbbbpnf", where "bbbb" is the baud rate,
533 "p" is parity ("n", "o", or "e"), "n" is number of
534 bits, and "f" is flow control ("r" for RTS or
535 omit it). Default is "9600n8".
537 See Documentation/serial-console.txt for more
538 information. See
539 Documentation/networking/netconsole.txt for an
540 alternative.
542 uart[8250],io,<addr>[,options]
543 uart[8250],mmio,<addr>[,options]
544 Start an early, polled-mode console on the 8250/16550
545 UART at the specified I/O port or MMIO address,
546 switching to the matching ttyS device later. The
547 options are the same as for ttyS, above.
549 If the device connected to the port is not a TTY but a braille
550 device, prepend "brl," before the device type, for instance
551 console=brl,ttyS0
552 For now, only VisioBraille is supported.
554 consoleblank= [KNL] The console blank (screen saver) timeout in
555 seconds. Defaults to 10*60 = 10mins. A value of 0
556 disables the blank timer.
558 coredump_filter=
559 [KNL] Change the default value for
560 /proc/<pid>/coredump_filter.
561 See also Documentation/filesystems/proc.txt.
563 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
564 Format:
565 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
567 crashkernel=nn[KMG]@ss[KMG]
568 [KNL] Reserve a chunk of physical memory to
569 hold a kernel to switch to with kexec on panic.
571 crashkernel=range1:size1[,range2:size2,...][@offset]
572 [KNL] Same as above, but depends on the memory
573 in the running system. The syntax of range is
574 start-[end] where start and end are both
575 a memory unit (amount[KMG]). See also
576 Documentation/kdump/kdump.txt for a example.
578 cs89x0_dma= [HW,NET]
579 Format: <dma>
581 cs89x0_media= [HW,NET]
582 Format: { rj45 | aui | bnc }
584 dasd= [HW,NET]
585 See header of drivers/s390/block/dasd_devmap.c.
587 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
588 (one device per port)
589 Format: <port#>,<type>
590 See also Documentation/input/joystick-parport.txt
592 debug [KNL] Enable kernel debugging (events log level).
594 debug_locks_verbose=
595 [KNL] verbose self-tests
596 Format=<0|1>
597 Print debugging info while doing the locking API
598 self-tests.
599 We default to 0 (no extra messages), setting it to
600 1 will print _a lot_ more information - normally
601 only useful to kernel developers.
603 debug_objects [KNL] Enable object debugging
605 no_debug_objects
606 [KNL] Disable object debugging
608 debugpat [X86] Enable PAT debugging
610 decnet.addr= [HW,NET]
611 Format: <area>[,<node>]
612 See also Documentation/networking/decnet.txt.
614 default_hugepagesz=
615 [same as hugepagesz=] The size of the default
616 HugeTLB page size. This is the size represented by
617 the legacy /proc/ hugepages APIs, used for SHM, and
618 default size when mounting hugetlbfs filesystems.
619 Defaults to the default architecture's huge page size
620 if not specified.
622 dhash_entries= [KNL]
623 Set number of hash buckets for dentry cache.
625 digi= [HW,SERIAL]
626 IO parameters + enable/disable command.
628 digiepca= [HW,SERIAL]
629 See drivers/char/README.epca and
630 Documentation/serial/digiepca.txt.
632 disable_mtrr_cleanup [X86]
633 The kernel tries to adjust MTRR layout from continuous
634 to discrete, to make X server driver able to add WB
635 entry later. This parameter disables that.
637 disable_mtrr_trim [X86, Intel and AMD only]
638 By default the kernel will trim any uncacheable
639 memory out of your available memory pool based on
640 MTRR settings. This parameter disables that behavior,
641 possibly causing your machine to run very slowly.
643 disable_timer_pin_1 [X86]
644 Disable PIN 1 of APIC timer
645 Can be useful to work around chipset bugs.
647 dmasound= [HW,OSS] Sound subsystem buffers
649 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
650 this option disables the debugging code at boot.
652 dma_debug_entries=<number>
653 This option allows to tune the number of preallocated
654 entries for DMA-API debugging code. One entry is
655 required per DMA-API allocation. Use this if the
656 DMA-API debugging code disables itself because the
657 architectural default is too low.
659 dma_debug_driver=<driver_name>
660 With this option the DMA-API debugging driver
661 filter feature can be enabled at boot time. Just
662 pass the driver to filter for as the parameter.
663 The filter can be disabled or changed to another
664 driver later using sysfs.
666 dscc4.setup= [NET]
668 dtc3181e= [HW,SCSI]
670 dynamic_printk Enables pr_debug()/dev_dbg() calls if
671 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
672 These can also be switched on/off via
673 <debugfs>/dynamic_printk/modules
675 earlycon= [KNL] Output early console device and options.
676 uart[8250],io,<addr>[,options]
677 uart[8250],mmio,<addr>[,options]
678 Start an early, polled-mode console on the 8250/16550
679 UART at the specified I/O port or MMIO address.
680 The options are the same as for ttyS, above.
682 earlyprintk= [X86,SH,BLACKFIN]
683 earlyprintk=vga
684 earlyprintk=serial[,ttySn[,baudrate]]
685 earlyprintk=ttySn[,baudrate]
686 earlyprintk=dbgp[debugController#]
688 Append ",keep" to not disable it when the real console
689 takes over.
691 Only vga or serial or usb debug port at a time.
693 Currently only ttyS0 and ttyS1 are supported.
695 Interaction with the standard serial driver is not
696 very good.
698 The VGA output is eventually overwritten by the real
699 console.
701 eata= [HW,SCSI]
703 edd= [EDD]
704 Format: {"off" | "on" | "skip[mbr]"}
706 eisa_irq_edge= [PARISC,HW]
707 See header of drivers/parisc/eisa.c.
709 elanfreq= [X86-32]
710 See comment before function elanfreq_setup() in
711 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
713 elevator= [IOSCHED]
714 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
715 See Documentation/block/as-iosched.txt and
716 Documentation/block/deadline-iosched.txt for details.
718 elfcorehdr= [IA64,PPC,SH,X86]
719 Specifies physical address of start of kernel core
720 image elf header. Generally kexec loader will
721 pass this option to capture kernel.
722 See Documentation/kdump/kdump.txt for details.
724 enable_mtrr_cleanup [X86]
725 The kernel tries to adjust MTRR layout from continuous
726 to discrete, to make X server driver able to add WB
727 entry later. This parameter enables that.
729 enable_timer_pin_1 [X86]
730 Enable PIN 1 of APIC timer
731 Can be useful to work around chipset bugs
732 (in particular on some ATI chipsets).
733 The kernel tries to set a reasonable default.
735 enforcing [SELINUX] Set initial enforcing status.
736 Format: {"0" | "1"}
737 See security/selinux/Kconfig help text.
738 0 -- permissive (log only, no denials).
739 1 -- enforcing (deny and log).
740 Default value is 0.
741 Value can be changed at runtime via /selinux/enforce.
743 ether= [HW,NET] Ethernet cards parameters
744 This option is obsoleted by the "netdev=" option, which
745 has equivalent usage. See its documentation for details.
747 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
748 Format: <io>[,<irq>]
750 failslab=
751 fail_page_alloc=
752 fail_make_request=[KNL]
753 General fault injection mechanism.
754 Format: <interval>,<probability>,<space>,<times>
755 See also /Documentation/fault-injection/.
757 fd_mcs= [HW,SCSI]
758 See header of drivers/scsi/fd_mcs.c.
760 fdomain= [HW,SCSI]
761 See header of drivers/scsi/fdomain.c.
763 floppy= [HW]
764 See Documentation/blockdev/floppy.txt.
766 force_pal_cache_flush
767 [IA-64] Avoid check_sal_cache_flush which may hang on
768 buggy SAL_CACHE_FLUSH implementations. Using this
769 parameter will force ia64_sal_cache_flush to call
770 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
772 ftrace=[tracer]
773 [FTRACE] will set and start the specified tracer
774 as early as possible in order to facilitate early
775 boot debugging.
777 ftrace_dump_on_oops
778 [FTRACE] will dump the trace buffers on oops.
780 ftrace_filter=[function-list]
781 [FTRACE] Limit the functions traced by the function
782 tracer at boot up. function-list is a comma separated
783 list of functions. This list can be changed at run
784 time by the set_ftrace_filter file in the debugfs
785 tracing directory.
787 ftrace_notrace=[function-list]
788 [FTRACE] Do not trace the functions specified in
789 function-list. This list can be changed at run time
790 by the set_ftrace_notrace file in the debugfs
791 tracing directory.
793 ftrace_graph_filter=[function-list]
794 [FTRACE] Limit the top level callers functions traced
795 by the function graph tracer at boot up.
796 function-list is a comma separated list of functions
797 that can be changed at run time by the
798 set_graph_function file in the debugfs tracing directory.
800 gamecon.map[2|3]=
801 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
802 support via parallel port (up to 5 devices per port)
803 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
804 See also Documentation/input/joystick-parport.txt
806 gamma= [HW,DRM]
808 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
809 Format: off | on
810 default: on
812 gcov_persist= [GCOV] When non-zero (default), profiling data for
813 kernel modules is saved and remains accessible via
814 debugfs, even when the module is unloaded/reloaded.
815 When zero, profiling data is discarded and associated
816 debugfs files are removed at module unload time.
818 gdth= [HW,SCSI]
819 See header of drivers/scsi/gdth.c.
821 gpt [EFI] Forces disk with valid GPT signature but
822 invalid Protective MBR to be treated as GPT.
824 gvp11= [HW,SCSI]
826 hashdist= [KNL,NUMA] Large hashes allocated during boot
827 are distributed across NUMA nodes. Defaults on
828 for 64bit NUMA, off otherwise.
829 Format: 0 | 1 (for off | on)
831 hcl= [IA-64] SGI's Hardware Graph compatibility layer
833 hd= [EIDE] (E)IDE hard drive subsystem geometry
834 Format: <cyl>,<head>,<sect>
836 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
837 size of <nn>. This works even on boxes that have no
838 highmem otherwise. This also works to reduce highmem
839 size on bigger boxes.
841 highres= [KNL] Enable/disable high resolution timer mode.
842 Valid parameters: "on", "off"
843 Default: "on"
845 hisax= [HW,ISDN]
846 See Documentation/isdn/README.HiSax.
848 hlt [BUGS=ARM,SH]
850 hpet= [X86-32,HPET] option to control HPET usage
851 Format: { enable (default) | disable | force |
852 verbose }
853 disable: disable HPET and use PIT instead
854 force: allow force enabled of undocumented chips (ICH4,
855 VIA, nVidia)
856 verbose: show contents of HPET registers during setup
858 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
859 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
860 On x86-64 and powerpc, this option can be specified
861 multiple times interleaved with hugepages= to reserve
862 huge pages of different sizes. Valid pages sizes on
863 x86-64 are 2M (when the CPU supports "pse") and 1G
864 (when the CPU supports the "pdpe1gb" cpuinfo flag)
865 Note that 1GB pages can only be allocated at boot time
866 using hugepages= and not freed afterwards.
868 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
869 terminal devices. Valid values: 0..8
870 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
871 If specified, z/VM IUCV HVC accepts connections
872 from listed z/VM user IDs only.
874 i2c_bus= [HW] Override the default board specific I2C bus speed
875 or register an additional I2C bus that is not
876 registered from board initialization code.
877 Format:
878 <bus_id>,<clkrate>
880 i8042.debug [HW] Toggle i8042 debug mode
881 i8042.direct [HW] Put keyboard port into non-translated mode
882 i8042.dumbkbd [HW] Pretend that controller can only read data from
883 keyboard and cannot control its state
884 (Don't attempt to blink the leds)
885 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
886 i8042.nokbd [HW] Don't check/create keyboard port
887 i8042.noloop [HW] Disable the AUX Loopback command while probing
888 for the AUX port
889 i8042.nomux [HW] Don't check presence of an active multiplexing
890 controller
891 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
892 controllers
893 i8042.panicblink=
894 [HW] Frequency with which keyboard LEDs should blink
895 when kernel panics (default is 0.5 sec)
896 i8042.reset [HW] Reset the controller during init and cleanup
897 i8042.unlock [HW] Unlock (ignore) the keylock
899 i810= [HW,DRM]
901 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
902 indicates that the driver is running on unsupported
903 hardware.
904 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
905 does not match list of supported models.
906 i8k.power_status
907 [HW] Report power status in /proc/i8k
908 (disabled by default)
909 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
910 capability is set.
912 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
913 See Documentation/mca.txt.
915 icn= [HW,ISDN]
916 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
918 ide-core.nodma= [HW] (E)IDE subsystem
919 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
920 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
921 .cdrom .chs .ignore_cable are additional options
922 See Documentation/ide/ide.txt.
924 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
925 Claim all unknown PCI IDE storage controllers.
927 idle= [X86]
928 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
929 Poll forces a polling idle loop that can slightly
930 improve the performance of waking up a idle CPU, but
931 will use a lot of power and make the system run hot.
932 Not recommended.
933 idle=mwait: On systems which support MONITOR/MWAIT but
934 the kernel chose to not use it because it doesn't save
935 as much power as a normal idle loop, use the
936 MONITOR/MWAIT idle loop anyways. Performance should be
937 the same as idle=poll.
938 idle=halt: Halt is forced to be used for CPU idle.
939 In such case C2/C3 won't be used again.
940 idle=nomwait: Disable mwait for CPU C-states
942 ignore_loglevel [KNL]
943 Ignore loglevel setting - this will print /all/
944 kernel messages to the console. Useful for debugging.
946 ihash_entries= [KNL]
947 Set number of hash buckets for inode cache.
949 ima_audit= [IMA]
950 Format: { "0" | "1" }
951 0 -- integrity auditing messages. (Default)
952 1 -- enable informational integrity auditing messages.
954 ima_hash= [IMA]
955 Format: { "sha1" | "md5" }
956 default: "sha1"
958 ima_tcb [IMA]
959 Load a policy which meets the needs of the Trusted
960 Computing Base. This means IMA will measure all
961 programs exec'd, files mmap'd for exec, and all files
962 opened for read by uid=0.
964 in2000= [HW,SCSI]
965 See header of drivers/scsi/in2000.c.
967 init= [KNL]
968 Format: <full_path>
969 Run specified binary instead of /sbin/init as init
970 process.
972 initcall_debug [KNL] Trace initcalls as they are executed. Useful
973 for working out where the kernel is dying during
974 startup.
976 initrd= [BOOT] Specify the location of the initial ramdisk
978 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
979 Format: <irq>
981 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
982 on
983 Enable intel iommu driver.
984 off
985 Disable intel iommu driver.
986 igfx_off [Default Off]
987 By default, gfx is mapped as normal device. If a gfx
988 device has a dedicated DMAR unit, the DMAR unit is
989 bypassed by not enabling DMAR with this option. In
990 this case, gfx device will use physical address for
991 DMA.
992 forcedac [x86_64]
993 With this option iommu will not optimize to look
994 for io virtual address below 32 bit forcing dual
995 address cycle on pci bus for cards supporting greater
996 than 32 bit addressing. The default is to look
997 for translation below 32 bit and if not available
998 then look in the higher range.
999 strict [Default Off]
1000 With this option on every unmap_single operation will
1001 result in a hardware IOTLB flush operation as opposed
1002 to batching them for performance.
1004 inttest= [IA64]
1006 iomem= Disable strict checking of access to MMIO memory
1007 strict regions from userspace.
1008 relaxed
1010 iommu= [x86]
1011 off
1012 force
1013 noforce
1014 biomerge
1015 panic
1016 nopanic
1017 merge
1018 nomerge
1019 forcesac
1020 soft
1021 pt [x86, IA64]
1023 io7= [HW] IO7 for Marvel based alpha systems
1024 See comment before marvel_specify_io7 in
1025 arch/alpha/kernel/core_marvel.c.
1027 io_delay= [X86] I/O delay method
1028 0x80
1029 Standard port 0x80 based delay
1030 0xed
1031 Alternate port 0xed based delay (needed on some systems)
1032 udelay
1033 Simple two microseconds delay
1034 none
1035 No delay
1037 ip= [IP_PNP]
1038 See Documentation/filesystems/nfs/nfsroot.txt.
1040 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1041 See comment before ip2_setup() in
1042 drivers/char/ip2/ip2base.c.
1044 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1045 See header of drivers/scsi/ips.c.
1047 irqfixup [HW]
1048 When an interrupt is not handled search all handlers
1049 for it. Intended to get systems with badly broken
1050 firmware running.
1052 irqpoll [HW]
1053 When an interrupt is not handled search all handlers
1054 for it. Also check all handlers each timer
1055 interrupt. Intended to get systems with badly broken
1056 firmware running.
1058 isapnp= [ISAPNP]
1059 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1061 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1062 Format:
1063 <cpu number>,...,<cpu number>
1064 or
1065 <cpu number>-<cpu number>
1066 (must be a positive range in ascending order)
1067 or a mixture
1068 <cpu number>,...,<cpu number>-<cpu number>
1070 This option can be used to specify one or more CPUs
1071 to isolate from the general SMP balancing and scheduling
1072 algorithms. You can move a process onto or off an
1073 "isolated" CPU via the CPU affinity syscalls or cpuset.
1074 <cpu number> begins at 0 and the maximum value is
1075 "number of CPUs in system - 1".
1077 This option is the preferred way to isolate CPUs. The
1078 alternative -- manually setting the CPU mask of all
1079 tasks in the system -- can cause problems and
1080 suboptimal load balancer performance.
1082 iucv= [HW,NET]
1084 js= [HW,JOY] Analog joystick
1085 See Documentation/input/joystick.txt.
1087 keepinitrd [HW,ARM]
1089 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1090 specifies the amount of memory usable by the kernel
1091 for non-movable allocations. The requested amount is
1092 spread evenly throughout all nodes in the system. The
1093 remaining memory in each node is used for Movable
1094 pages. In the event, a node is too small to have both
1095 kernelcore and Movable pages, kernelcore pages will
1096 take priority and other nodes will have a larger number
1097 of kernelcore pages. The Movable zone is used for the
1098 allocation of pages that may be reclaimed or moved
1099 by the page migration subsystem. This means that
1100 HugeTLB pages may not be allocated from this zone.
1101 Note that allocations like PTEs-from-HighMem still
1102 use the HighMem zone if it exists, and the Normal
1103 zone if it does not.
1105 kgdboc= [HW] kgdb over consoles.
1106 Requires a tty driver that supports console polling.
1107 (only serial supported for now)
1108 Format: <serial_device>[,baud]
1110 kmac= [MIPS] korina ethernet MAC address.
1111 Configure the RouterBoard 532 series on-chip
1112 Ethernet adapter MAC address.
1114 kmemleak= [KNL] Boot-time kmemleak enable/disable
1115 Valid arguments: on, off
1116 Default: on
1118 kstack=N [X86] Print N words from the kernel stack
1119 in oops dumps.
1121 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1122 Default is 0 (don't ignore, but inject #GP)
1124 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1125 Default is 1 (enabled)
1127 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1128 Default is 0 (off)
1130 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1131 for all guests.
1132 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1134 kvm-intel.bypass_guest_pf=
1135 [KVM,Intel] Disables bypassing of guest page faults
1136 on Intel chips. Default is 1 (enabled)
1138 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1139 (virtualized MMU) support on capable Intel chips.
1140 Default is 1 (enabled)
1142 kvm-intel.emulate_invalid_guest_state=
1143 [KVM,Intel] Enable emulation of invalid guest states
1144 Default is 0 (disabled)
1146 kvm-intel.flexpriority=
1147 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1148 Default is 1 (enabled)
1150 kvm-intel.unrestricted_guest=
1151 [KVM,Intel] Disable unrestricted guest feature
1152 (virtualized real and unpaged mode) on capable
1153 Intel chips. Default is 1 (enabled)
1155 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1156 feature (tagged TLBs) on capable Intel chips.
1157 Default is 1 (enabled)
1159 l2cr= [PPC]
1161 l3cr= [PPC]
1163 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1164 disabled it.
1166 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1167 in C2 power state.
1169 libata.dma= [LIBATA] DMA control
1170 libata.dma=0 Disable all PATA and SATA DMA
1171 libata.dma=1 PATA and SATA Disk DMA only
1172 libata.dma=2 ATAPI (CDROM) DMA only
1173 libata.dma=4 Compact Flash DMA only
1174 Combinations also work, so libata.dma=3 enables DMA
1175 for disks and CDROMs, but not CFs.
1177 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1178 libata.ignore_hpa=0 keep BIOS limits (default)
1179 libata.ignore_hpa=1 ignore limits, using full disk
1181 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1182 when set.
1183 Format: <int>
1185 libata.force= [LIBATA] Force configurations. The format is comma
1186 separated list of "[ID:]VAL" where ID is
1187 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1188 matching port, link or device. Basically, it matches
1189 the ATA ID string printed on console by libata. If
1190 the whole ID part is omitted, the last PORT and DEVICE
1191 values are used. If ID hasn't been specified yet, the
1192 configuration applies to all ports, links and devices.
1194 If only DEVICE is omitted, the parameter applies to
1195 the port and all links and devices behind it. DEVICE
1196 number of 0 either selects the first device or the
1197 first fan-out link behind PMP device. It does not
1198 select the host link. DEVICE number of 15 selects the
1199 host link and device attached to it.
1201 The VAL specifies the configuration to force. As long
1202 as there's no ambiguity shortcut notation is allowed.
1203 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1204 The following configurations can be forced.
1206 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1207 Any ID with matching PORT is used.
1209 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1211 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1212 udma[/][16,25,33,44,66,100,133] notation is also
1213 allowed.
1215 * [no]ncq: Turn on or off NCQ.
1217 * nohrst, nosrst, norst: suppress hard, soft
1218 and both resets.
1220 If there are multiple matching configurations changing
1221 the same attribute, the last one is used.
1223 lmb=debug [KNL] Enable lmb debug messages.
1225 load_ramdisk= [RAM] List of ramdisks to load from floppy
1226 See Documentation/blockdev/ramdisk.txt.
1228 lockd.nlm_grace_period=P [NFS] Assign grace period.
1229 Format: <integer>
1231 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1232 Format: <integer>
1234 lockd.nlm_timeout=T [NFS] Assign timeout value.
1235 Format: <integer>
1237 lockd.nlm_udpport=M [NFS] Assign UDP port.
1238 Format: <integer>
1240 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1241 Format: <irq>
1243 loglevel= All Kernel Messages with a loglevel smaller than the
1244 console loglevel will be printed to the console. It can
1245 also be changed with klogd or other programs. The
1246 loglevels are defined as follows:
1248 0 (KERN_EMERG) system is unusable
1249 1 (KERN_ALERT) action must be taken immediately
1250 2 (KERN_CRIT) critical conditions
1251 3 (KERN_ERR) error conditions
1252 4 (KERN_WARNING) warning conditions
1253 5 (KERN_NOTICE) normal but significant condition
1254 6 (KERN_INFO) informational
1255 7 (KERN_DEBUG) debug-level messages
1257 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1258 Format: { n | nk | nM }
1259 n must be a power of two. The default size
1260 is set in the kernel config file.
1262 logo.nologo [FB] Disables display of the built-in Linux logo.
1263 This may be used to provide more screen space for
1264 kernel log messages and is useful when debugging
1265 kernel boot problems.
1267 lp=0 [LP] Specify parallel ports to use, e.g,
1268 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1269 lp=reset first parallel port). 'lp=0' disables the
1270 lp=auto printer driver. 'lp=reset' (which can be
1271 specified in addition to the ports) causes
1272 attached printers to be reset. Using
1273 lp=port1,port2,... specifies the parallel ports
1274 to associate lp devices with, starting with
1275 lp0. A port specification may be 'none' to skip
1276 that lp device, or a parport name such as
1277 'parport0'. Specifying 'lp=auto' instead of a
1278 port specification list means that device IDs
1279 from each port should be examined, to see if
1280 an IEEE 1284-compliant printer is attached; if
1281 so, the driver will manage that printer.
1282 See also header of drivers/char/lp.c.
1284 lpj=n [KNL]
1285 Sets loops_per_jiffy to given constant, thus avoiding
1286 time-consuming boot-time autodetection (up to 250 ms per
1287 CPU). 0 enables autodetection (default). To determine
1288 the correct value for your kernel, boot with normal
1289 autodetection and see what value is printed. Note that
1290 on SMP systems the preset will be applied to all CPUs,
1291 which is likely to cause problems if your CPUs need
1292 significantly divergent settings. An incorrect value
1293 will cause delays in the kernel to be wrong, leading to
1294 unpredictable I/O errors and other breakage. Although
1295 unlikely, in the extreme case this might damage your
1296 hardware.
1298 ltpc= [NET]
1299 Format: <io>,<irq>,<dma>
1301 mac5380= [HW,SCSI] Format:
1302 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1304 machvec= [IA64] Force the use of a particular machine-vector
1305 (machvec) in a generic kernel.
1306 Example: machvec=hpzx1_swiotlb
1308 machtype= [Loongson] Share the same kernel image file between different
1309 yeeloong laptop.
1310 Example: machtype=lemote-yeeloong-2f-7inch
1312 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1313 than or equal to this physical address is ignored.
1315 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1316 should make use of. maxcpus=n : n >= 0 limits the
1317 kernel to using 'n' processors. n=0 is a special case,
1318 it is equivalent to "nosmp", which also disables
1319 the IO APIC.
1321 max_loop= [LOOP] Maximum number of loopback devices that can
1322 be mounted
1323 Format: <1-256>
1325 max_luns= [SCSI] Maximum number of LUNs to probe.
1326 Should be between 1 and 2^32-1.
1328 max_report_luns=
1329 [SCSI] Maximum number of LUNs received.
1330 Should be between 1 and 16384.
1332 mcatest= [IA-64]
1334 mce [X86-32] Machine Check Exception
1336 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1338 md= [HW] RAID subsystems devices and level
1339 See Documentation/md.txt.
1341 mdacon= [MDA]
1342 Format: <first>,<last>
1343 Specifies range of consoles to be captured by the MDA.
1345 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1346 Amount of memory to be used when the kernel is not able
1347 to see the whole system memory or for test.
1348 [X86-32] Use together with memmap= to avoid physical
1349 address space collisions. Without memmap= PCI devices
1350 could be placed at addresses belonging to unused RAM.
1352 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1353 memory.
1355 memchunk=nn[KMG]
1356 [KNL,SH] Allow user to override the default size for
1357 per-device physically contiguous DMA buffers.
1359 memmap=exactmap [KNL,X86] Enable setting of an exact
1360 E820 memory map, as specified by the user.
1361 Such memmap=exactmap lines can be constructed based on
1362 BIOS output or other requirements. See the memmap=nn@ss
1363 option description.
1365 memmap=nn[KMG]@ss[KMG]
1366 [KNL] Force usage of a specific region of memory
1367 Region of memory to be used, from ss to ss+nn.
1369 memmap=nn[KMG]#ss[KMG]
1370 [KNL,ACPI] Mark specific memory as ACPI data.
1371 Region of memory to be used, from ss to ss+nn.
1373 memmap=nn[KMG]$ss[KMG]
1374 [KNL,ACPI] Mark specific memory as reserved.
1375 Region of memory to be used, from ss to ss+nn.
1376 Example: Exclude memory from 0x18690000-0x1869ffff
1377 memmap=64K$0x18690000
1378 or
1379 memmap=0x10000$0x18690000
1381 memory_corruption_check=0/1 [X86]
1382 Some BIOSes seem to corrupt the first 64k of
1383 memory when doing things like suspend/resume.
1384 Setting this option will scan the memory
1385 looking for corruption. Enabling this will
1386 both detect corruption and prevent the kernel
1387 from using the memory being corrupted.
1388 However, its intended as a diagnostic tool; if
1389 repeatable BIOS-originated corruption always
1390 affects the same memory, you can use memmap=
1391 to prevent the kernel from using that memory.
1393 memory_corruption_check_size=size [X86]
1394 By default it checks for corruption in the low
1395 64k, making this memory unavailable for normal
1396 use. Use this parameter to scan for
1397 corruption in more or less memory.
1399 memory_corruption_check_period=seconds [X86]
1400 By default it checks for corruption every 60
1401 seconds. Use this parameter to check at some
1402 other rate. 0 disables periodic checking.
1404 memtest= [KNL,X86] Enable memtest
1405 Format: <integer>
1406 default : 0 <disable>
1407 Specifies the number of memtest passes to be
1408 performed. Each pass selects another test
1409 pattern from a given set of patterns. Memtest
1410 fills the memory with this pattern, validates
1411 memory contents and reserves bad memory
1412 regions that are detected.
1414 meye.*= [HW] Set MotionEye Camera parameters
1415 See Documentation/video4linux/meye.txt.
1417 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1418 Multi-Function General Purpose Timers on AMD Geode
1419 platforms.
1421 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1422 the BIOS has incorrectly applied a workaround. TinyBIOS
1423 version 0.98 is known to be affected, 0.99 fixes the
1424 problem by letting the user disable the workaround.
1426 mga= [HW,DRM]
1428 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1429 physical address is ignored.
1431 mini2440= [ARM,HW,KNL]
1432 Format:[0..2][b][c][t]
1433 Default: "0tb"
1434 MINI2440 configuration specification:
1435 0 - The attached screen is the 3.5" TFT
1436 1 - The attached screen is the 7" TFT
1437 2 - The VGA Shield is attached (1024x768)
1438 Leaving out the screen size parameter will not load
1439 the TFT driver, and the framebuffer will be left
1440 unconfigured.
1441 b - Enable backlight. The TFT backlight pin will be
1442 linked to the kernel VESA blanking code and a GPIO
1443 LED. This parameter is not necessary when using the
1444 VGA shield.
1445 c - Enable the s3c camera interface.
1446 t - Reserved for enabling touchscreen support. The
1447 touchscreen support is not enabled in the mainstream
1448 kernel as of 2.6.30, a preliminary port can be found
1449 in the "bleeding edge" mini2440 support kernel at
1450 http://repo.or.cz/w/linux-2.6/mini2440.git
1452 mminit_loglevel=
1453 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1454 parameter allows control of the logging verbosity for
1455 the additional memory initialisation checks. A value
1456 of 0 disables mminit logging and a level of 4 will
1457 log everything. Information is printed at KERN_DEBUG
1458 so loglevel=8 may also need to be specified.
1460 mousedev.tap_time=
1461 [MOUSE] Maximum time between finger touching and
1462 leaving touchpad surface for touch to be considered
1463 a tap and be reported as a left button click (for
1464 touchpads working in absolute mode only).
1465 Format: <msecs>
1466 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1467 reporting absolute coordinates, such as tablets
1468 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1469 reporting absolute coordinates, such as tablets
1471 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1472 is similar to kernelcore except it specifies the
1473 amount of memory used for migratable allocations.
1474 If both kernelcore and movablecore is specified,
1475 then kernelcore will be at *least* the specified
1476 value but may be more. If movablecore on its own
1477 is specified, the administrator must be careful
1478 that the amount of memory usable for all allocations
1479 is not too small.
1481 mpu401= [HW,OSS]
1482 Format: <io>,<irq>
1484 MTD_Partition= [MTD]
1485 Format: <name>,<region-number>,<size>,<offset>
1487 MTD_Region= [MTD] Format:
1488 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1490 mtdparts= [MTD]
1491 See drivers/mtd/cmdlinepart.c.
1493 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1495 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1497 boundary - index of last SLC block on Flex-OneNAND.
1498 The remaining blocks are configured as MLC blocks.
1499 lock - Configure if Flex-OneNAND boundary should be locked.
1500 Once locked, the boundary cannot be changed.
1501 1 indicates lock status, 0 indicates unlock status.
1503 mtdset= [ARM]
1504 ARM/S3C2412 JIVE boot control
1506 See arch/arm/mach-s3c2412/mach-jive.c
1508 mtouchusb.raw_coordinates=
1509 [HW] Make the MicroTouch USB driver use raw coordinates
1510 ('y', default) or cooked coordinates ('n')
1512 mtrr_chunk_size=nn[KMG] [X86]
1513 used for mtrr cleanup. It is largest continuous chunk
1514 that could hold holes aka. UC entries.
1516 mtrr_gran_size=nn[KMG] [X86]
1517 Used for mtrr cleanup. It is granularity of mtrr block.
1518 Default is 1.
1519 Large value could prevent small alignment from
1520 using up MTRRs.
1522 mtrr_spare_reg_nr=n [X86]
1523 Format: <integer>
1524 Range: 0,7 : spare reg number
1525 Default : 1
1526 Used for mtrr cleanup. It is spare mtrr entries number.
1527 Set to 2 or more if your graphical card needs more.
1529 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1531 NCR_D700= [HW,SCSI]
1532 See header of drivers/scsi/NCR_D700.c.
1534 ncr5380= [HW,SCSI]
1536 ncr53c400= [HW,SCSI]
1538 ncr53c400a= [HW,SCSI]
1540 ncr53c406a= [HW,SCSI]
1542 ncr53c8xx= [HW,SCSI]
1544 netdev= [NET] Network devices parameters
1545 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1546 Note that mem_start is often overloaded to mean
1547 something different and driver-specific.
1548 This usage is only documented in each driver source
1549 file if at all.
1551 nf_conntrack.acct=
1552 [NETFILTER] Enable connection tracking flow accounting
1553 0 to disable accounting
1554 1 to enable accounting
1555 Default value depends on CONFIG_NF_CT_ACCT that is
1556 going to be removed in 2.6.29.
1558 nfsaddrs= [NFS]
1559 See Documentation/filesystems/nfs/nfsroot.txt.
1561 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1562 See Documentation/filesystems/nfs/nfsroot.txt.
1564 nfs.callback_tcpport=
1565 [NFS] set the TCP port on which the NFSv4 callback
1566 channel should listen.
1568 nfs.cache_getent=
1569 [NFS] sets the pathname to the program which is used
1570 to update the NFS client cache entries.
1572 nfs.cache_getent_timeout=
1573 [NFS] sets the timeout after which an attempt to
1574 update a cache entry is deemed to have failed.
1576 nfs.idmap_cache_timeout=
1577 [NFS] set the maximum lifetime for idmapper cache
1578 entries.
1580 nfs.enable_ino64=
1581 [NFS] enable 64-bit inode numbers.
1582 If zero, the NFS client will fake up a 32-bit inode
1583 number for the readdir() and stat() syscalls instead
1584 of returning the full 64-bit number.
1585 The default is to return 64-bit inode numbers.
1587 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1588 when a NMI is triggered.
1589 Format: [state][,regs][,debounce][,die]
1591 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1592 Format: [panic,][num]
1593 Valid num: 0,1,2
1594 0 - turn nmi_watchdog off
1595 1 - use the IO-APIC timer for the NMI watchdog
1596 2 - use the local APIC for the NMI watchdog using
1597 a performance counter. Note: This will use one
1598 performance counter and the local APIC's performance
1599 vector.
1600 When panic is specified, panic when an NMI watchdog
1601 timeout occurs.
1602 This is useful when you use a panic=... timeout and
1603 need the box quickly up again.
1604 Instead of 1 and 2 it is possible to use the following
1605 symbolic names: lapic and ioapic
1606 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1608 netpoll.carrier_timeout=
1609 [NET] Specifies amount of time (in seconds) that
1610 netpoll should wait for a carrier. By default netpoll
1611 waits 4 seconds.
1613 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1614 emulation library even if a 387 maths coprocessor
1615 is present.
1617 no_console_suspend
1618 [HW] Never suspend the console
1619 Disable suspending of consoles during suspend and
1620 hibernate operations. Once disabled, debugging
1621 messages can reach various consoles while the rest
1622 of the system is being put to sleep (ie, while
1623 debugging driver suspend/resume hooks). This may
1624 not work reliably with all consoles, but is known
1625 to work with serial and VGA consoles.
1627 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1628 caches in the slab allocator. Saves per-node memory,
1629 but will impact performance.
1631 noalign [KNL,ARM]
1633 noapic [SMP,APIC] Tells the kernel to not make use of any
1634 IOAPICs that may be present in the system.
1636 nobats [PPC] Do not use BATs for mapping kernel lowmem
1637 on "Classic" PPC cores.
1639 nocache [ARM]
1641 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1643 nodelayacct [KNL] Disable per-task delay accounting
1645 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1647 nodsp [SH] Disable hardware DSP at boot time.
1649 noefi [X86] Disable EFI runtime services support.
1651 noexec [IA-64]
1653 noexec [X86]
1654 On X86-32 available only on PAE configured kernels.
1655 noexec=on: enable non-executable mappings (default)
1656 noexec=off: disable non-executable mappings
1658 noexec32 [X86-64]
1659 This affects only 32-bit executables.
1660 noexec32=on: enable non-executable mappings (default)
1661 read doesn't imply executable mappings
1662 noexec32=off: disable non-executable mappings
1663 read implies executable mappings
1665 nofpu [SH] Disable hardware FPU at boot time.
1667 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1668 register save and restore. The kernel will only save
1669 legacy floating-point registers on task switch.
1671 noxsave [BUGS=X86] Disables x86 extended register state save
1672 and restore using xsave. The kernel will fallback to
1673 enabling legacy floating-point and sse state.
1675 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1676 wfi(ARM) instruction doesn't work correctly and not to
1677 use it. This is also useful when using JTAG debugger.
1679 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1680 instruction doesn't work correctly and not to
1681 use it.
1683 no_file_caps Tells the kernel not to honor file capabilities. The
1684 only way then for a file to be executed with privilege
1685 is to be setuid root or executed by root.
1687 nohalt [IA-64] Tells the kernel not to use the power saving
1688 function PAL_HALT_LIGHT when idle. This increases
1689 power-consumption. On the positive side, it reduces
1690 interrupt wake-up latency, which may improve performance
1691 in certain environments such as networked servers or
1692 real-time systems.
1694 nohz= [KNL] Boottime enable/disable dynamic ticks
1695 Valid arguments: on, off
1696 Default: on
1698 noiotrap [SH] Disables trapped I/O port accesses.
1700 noirqdebug [X86-32] Disables the code which attempts to detect and
1701 disable unhandled interrupt sources.
1703 no_timer_check [X86,APIC] Disables the code which tests for
1704 broken timer IRQ sources.
1706 noisapnp [ISAPNP] Disables ISA PnP code.
1708 noinitrd [RAM] Tells the kernel not to load any configured
1709 initial RAM disk.
1711 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1712 remapping.
1714 nointroute [IA-64]
1716 nojitter [IA64] Disables jitter checking for ITC timers.
1718 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1720 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1722 noltlbs [PPC] Do not use large page/tlb entries for kernel
1723 lowmem mapping on PPC40x.
1725 nomca [IA-64] Disable machine check abort handling
1727 nomce [X86-32] Machine Check Exception
1729 nomfgpt [X86-32] Disable Multi-Function General Purpose
1730 Timer usage (for AMD Geode machines).
1732 norandmaps Don't use address space randomization. Equivalent to
1733 echo 0 > /proc/sys/kernel/randomize_va_space
1735 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1737 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1738 with UP alternatives
1740 noresidual [PPC] Don't use residual data on PReP machines.
1742 noresume [SWSUSP] Disables resume and restores original swap
1743 space.
1745 no-scroll [VGA] Disables scrollback.
1746 This is required for the Braillex ib80-piezo Braille
1747 reader made by F.H. Papenmeier (Germany).
1749 nosbagart [IA-64]
1751 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1753 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1754 and disable the IO APIC. legacy for "maxcpus=0".
1756 nosoftlockup [KNL] Disable the soft-lockup detector.
1758 noswapaccount [KNL] Disable accounting of swap in memory resource
1759 controller. (See Documentation/cgroups/memory.txt)
1761 nosync [HW,M68K] Disables sync negotiation for all devices.
1763 notsc [BUGS=X86-32] Disable Time Stamp Counter
1765 nousb [USB] Disable the USB subsystem
1767 nowb [ARM]
1769 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1771 nptcg= [IA64] Override max number of concurrent global TLB
1772 purges which is reported from either PAL_VM_SUMMARY or
1773 SAL PALO.
1775 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1777 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1778 one of ['zone', 'node', 'default'] can be specified
1779 This can be set from sysctl after boot.
1780 See Documentation/sysctl/vm.txt for details.
1782 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1783 See Documentation/debugging-via-ohci1394.txt for more
1784 info.
1786 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1787 Rather than timing out after 20 ms if an EC
1788 command is not properly ACKed, override the length
1789 of the timeout. We have interrupts disabled while
1790 waiting for the ACK, so if this is set too high
1791 interrupts *may* be lost!
1793 omap_mux= [OMAP] Override bootloader pin multiplexing.
1794 Format: <mux_mode0.mode_name=value>...
1795 For example, to override I2C bus2:
1796 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1798 opl3= [HW,OSS]
1799 Format: <io>
1801 oprofile.timer= [HW]
1802 Use timer interrupt instead of performance counters
1804 oprofile.cpu_type= Force an oprofile cpu type
1805 This might be useful if you have an older oprofile
1806 userland or if you want common events.
1807 Format: { arch_perfmon }
1808 arch_perfmon: [X86] Force use of architectural
1809 perfmon on Intel CPUs instead of the
1810 CPU specific event set.
1812 osst= [HW,SCSI] SCSI Tape Driver
1813 Format: <buffer_size>,<write_threshold>
1814 See also Documentation/scsi/st.txt.
1816 panic= [KNL] Kernel behaviour on panic
1817 Format: <timeout>
1819 parkbd.port= [HW] Parallel port number the keyboard adapter is
1820 connected to, default is 0.
1821 Format: <parport#>
1822 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1823 0 for XT, 1 for AT (default is AT).
1824 Format: <mode>
1826 parport= [HW,PPT] Specify parallel ports. 0 disables.
1827 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1828 Use 'auto' to force the driver to use any
1829 IRQ/DMA settings detected (the default is to
1830 ignore detected IRQ/DMA settings because of
1831 possible conflicts). You can specify the base
1832 address, IRQ, and DMA settings; IRQ and DMA
1833 should be numbers, or 'auto' (for using detected
1834 settings on that particular port), or 'nofifo'
1835 (to avoid using a FIFO even if it is detected).
1836 Parallel ports are assigned in the order they
1837 are specified on the command line, starting
1838 with parport0.
1840 parport_init_mode= [HW,PPT]
1841 Configure VIA parallel port to operate in
1842 a specific mode. This is necessary on Pegasos
1843 computer where firmware has no options for setting
1844 up parallel port mode and sets it to spp.
1845 Currently this function knows 686a and 8231 chips.
1846 Format: [spp|ps2|epp|ecp|ecpepp]
1848 pas2= [HW,OSS] Format:
1849 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1851 pas16= [HW,SCSI]
1852 See header of drivers/scsi/pas16.c.
1854 pause_on_oops=
1855 Halt all CPUs after the first oops has been printed for
1856 the specified number of seconds. This is to be used if
1857 your oopses keep scrolling off the screen.
1859 pcbit= [HW,ISDN]
1861 pcd. [PARIDE]
1862 See header of drivers/block/paride/pcd.c.
1863 See also Documentation/blockdev/paride.txt.
1865 pci=option[,option...] [PCI] various PCI subsystem options:
1866 earlydump [X86] dump PCI config space before the kernel
1867 changes anything
1868 off [X86] don't probe for the PCI bus
1869 bios [X86-32] force use of PCI BIOS, don't access
1870 the hardware directly. Use this if your machine
1871 has a non-standard PCI host bridge.
1872 nobios [X86-32] disallow use of PCI BIOS, only direct
1873 hardware access methods are allowed. Use this
1874 if you experience crashes upon bootup and you
1875 suspect they are caused by the BIOS.
1876 conf1 [X86] Force use of PCI Configuration
1877 Mechanism 1.
1878 conf2 [X86] Force use of PCI Configuration
1879 Mechanism 2.
1880 noaer [PCIE] If the PCIEAER kernel config parameter is
1881 enabled, this kernel boot option can be used to
1882 disable the use of PCIE advanced error reporting.
1883 nodomains [PCI] Disable support for multiple PCI
1884 root domains (aka PCI segments, in ACPI-speak).
1885 nommconf [X86] Disable use of MMCONFIG for PCI
1886 Configuration
1887 check_enable_amd_mmconf [X86] check for and enable
1888 properly configured MMIO access to PCI
1889 config space on AMD family 10h CPU
1890 nomsi [MSI] If the PCI_MSI kernel config parameter is
1891 enabled, this kernel boot option can be used to
1892 disable the use of MSI interrupts system-wide.
1893 noioapicquirk [APIC] Disable all boot interrupt quirks.
1894 Safety option to keep boot IRQs enabled. This
1895 should never be necessary.
1896 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1897 primary IO-APIC for bridges that cannot disable
1898 boot IRQs. This fixes a source of spurious IRQs
1899 when the system masks IRQs.
1900 noioapicreroute [APIC] Disable workaround that uses the
1901 boot IRQ equivalent of an IRQ that connects to
1902 a chipset where boot IRQs cannot be disabled.
1903 The opposite of ioapicreroute.
1904 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1905 routing table. These calls are known to be buggy
1906 on several machines and they hang the machine
1907 when used, but on other computers it's the only
1908 way to get the interrupt routing table. Try
1909 this option if the kernel is unable to allocate
1910 IRQs or discover secondary PCI buses on your
1911 motherboard.
1912 rom [X86] Assign address space to expansion ROMs.
1913 Use with caution as certain devices share
1914 address decoders between ROMs and other
1915 resources.
1916 norom [X86] Do not assign address space to
1917 expansion ROMs that do not already have
1918 BIOS assigned address ranges.
1919 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1920 assigned automatically to PCI devices. You can
1921 make the kernel exclude IRQs of your ISA cards
1922 this way.
1923 pirqaddr=0xAAAAA [X86] Specify the physical address
1924 of the PIRQ table (normally generated
1925 by the BIOS) if it is outside the
1926 F0000h-100000h range.
1927 lastbus=N [X86] Scan all buses thru bus #N. Can be
1928 useful if the kernel is unable to find your
1929 secondary buses and you want to tell it
1930 explicitly which ones they are.
1931 assign-busses [X86] Always assign all PCI bus
1932 numbers ourselves, overriding
1933 whatever the firmware may have done.
1934 usepirqmask [X86] Honor the possible IRQ mask stored
1935 in the BIOS $PIR table. This is needed on
1936 some systems with broken BIOSes, notably
1937 some HP Pavilion N5400 and Omnibook XE3
1938 notebooks. This will have no effect if ACPI
1939 IRQ routing is enabled.
1940 noacpi [X86] Do not use ACPI for IRQ routing
1941 or for PCI scanning.
1942 use_crs [X86] Use _CRS for PCI resource
1943 allocation.
1944 routeirq Do IRQ routing for all PCI devices.
1945 This is normally done in pci_enable_device(),
1946 so this option is a temporary workaround
1947 for broken drivers that don't call it.
1948 skip_isa_align [X86] do not align io start addr, so can
1949 handle more pci cards
1950 firmware [ARM] Do not re-enumerate the bus but instead
1951 just use the configuration from the
1952 bootloader. This is currently used on
1953 IXP2000 systems where the bus has to be
1954 configured a certain way for adjunct CPUs.
1955 noearly [X86] Don't do any early type 1 scanning.
1956 This might help on some broken boards which
1957 machine check when some devices' config space
1958 is read. But various workarounds are disabled
1959 and some IOMMU drivers will not work.
1960 bfsort Sort PCI devices into breadth-first order.
1961 This sorting is done to get a device
1962 order compatible with older (<= 2.4) kernels.
1963 nobfsort Don't sort PCI devices into breadth-first order.
1964 cbiosize=nn[KMG] The fixed amount of bus space which is
1965 reserved for the CardBus bridge's IO window.
1966 The default value is 256 bytes.
1967 cbmemsize=nn[KMG] The fixed amount of bus space which is
1968 reserved for the CardBus bridge's memory
1969 window. The default value is 64 megabytes.
1970 resource_alignment=
1971 Format:
1972 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1973 Specifies alignment and device to reassign
1974 aligned memory resources.
1975 If <order of align> is not specified,
1976 PAGE_SIZE is used as alignment.
1977 PCI-PCI bridge can be specified, if resource
1978 windows need to be expanded.
1979 ecrc= Enable/disable PCIe ECRC (transaction layer
1980 end-to-end CRC checking).
1981 bios: Use BIOS/firmware settings. This is the
1982 the default.
1983 off: Turn ECRC off
1984 on: Turn ECRC on.
1986 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1987 Management.
1988 off Disable ASPM.
1989 force Enable ASPM even on devices that claim not to support it.
1990 WARNING: Forcing ASPM on may cause system lockups.
1992 pcmv= [HW,PCMCIA] BadgePAD 4
1994 pd. [PARIDE]
1995 See Documentation/blockdev/paride.txt.
1997 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1998 boot time.
1999 Format: { 0 | 1 }
2000 See arch/parisc/kernel/pdc_chassis.c
2002 percpu_alloc= Select which percpu first chunk allocator to use.
2003 Currently supported values are "embed" and "page".
2004 Archs may support subset or none of the selections.
2005 See comments in mm/percpu.c for details on each
2006 allocator. This parameter is primarily for debugging
2007 and performance comparison.
2009 pf. [PARIDE]
2010 See Documentation/blockdev/paride.txt.
2012 pg. [PARIDE]
2013 See Documentation/blockdev/paride.txt.
2015 pirq= [SMP,APIC] Manual mp-table setup
2016 See Documentation/x86/i386/IO-APIC.txt.
2018 plip= [PPT,NET] Parallel port network link
2019 Format: { parport<nr> | timid | 0 }
2020 See also Documentation/parport.txt.
2022 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2023 Override pmtimer IOPort with a hex value.
2024 e.g. pmtmr=0x508
2026 pnp.debug [PNP]
2027 Enable PNP debug messages. This depends on the
2028 CONFIG_PNP_DEBUG_MESSAGES option.
2030 pnpacpi= [ACPI]
2031 { off }
2033 pnpbios= [ISAPNP]
2034 { on | off | curr | res | no-curr | no-res }
2036 pnp_reserve_irq=
2037 [ISAPNP] Exclude IRQs for the autoconfiguration
2039 pnp_reserve_dma=
2040 [ISAPNP] Exclude DMAs for the autoconfiguration
2042 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2043 Ranges are in pairs (I/O port base and size).
2045 pnp_reserve_mem=
2046 [ISAPNP] Exclude memory regions for the
2047 autoconfiguration.
2048 Ranges are in pairs (memory base and size).
2050 ports= [IP_VS_FTP] IPVS ftp helper module
2051 Default is 21.
2052 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2053 may be specified.
2054 Format: <port>,<port>....
2056 print-fatal-signals=
2057 [KNL] debug: print fatal signals
2059 If enabled, warn about various signal handling
2060 related application anomalies: too many signals,
2061 too many POSIX.1 timers, fatal signals causing a
2062 coredump - etc.
2064 If you hit the warning due to signal overflow,
2065 you might want to try "ulimit -i unlimited".
2067 default: off.
2069 printk.time= Show timing data prefixed to each printk message line
2070 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2072 processor.max_cstate= [HW,ACPI]
2073 Limit processor to maximum C-state
2074 max_cstate=9 overrides any DMI blacklist limit.
2076 processor.nocst [HW,ACPI]
2077 Ignore the _CST method to determine C-states,
2078 instead using the legacy FADT method
2080 profile= [KNL] Enable kernel profiling via /proc/profile
2081 Format: [schedule,]<number>
2082 Param: "schedule" - profile schedule points.
2083 Param: <number> - step/bucket size as a power of 2 for
2084 statistical time based profiling.
2085 Param: "sleep" - profile D-state sleeping (millisecs).
2086 Requires CONFIG_SCHEDSTATS
2087 Param: "kvm" - profile VM exits.
2089 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2090 before loading.
2091 See Documentation/blockdev/ramdisk.txt.
2093 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2094 probe for; one of (bare|imps|exps|lifebook|any).
2095 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2096 per second.
2097 psmouse.resetafter= [HW,MOUSE]
2098 Try to reset the device after so many bad packets
2099 (0 = never).
2100 psmouse.resolution=
2101 [HW,MOUSE] Set desired mouse resolution, in dpi.
2102 psmouse.smartscroll=
2103 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2104 0 = disabled, 1 = enabled (default).
2106 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2107 Format:
2108 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2110 pt. [PARIDE]
2111 See Documentation/blockdev/paride.txt.
2113 pty.legacy_count=
2114 [KNL] Number of legacy pty's. Overwrites compiled-in
2115 default number.
2117 quiet [KNL] Disable most log messages
2119 r128= [HW,DRM]
2121 raid= [HW,RAID]
2122 See Documentation/md.txt.
2124 ramdisk_blocksize= [RAM]
2125 See Documentation/blockdev/ramdisk.txt.
2127 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2128 See Documentation/blockdev/ramdisk.txt.
2130 rcupdate.blimit= [KNL,BOOT]
2131 Set maximum number of finished RCU callbacks to process
2132 in one batch.
2134 rcupdate.qhimark= [KNL,BOOT]
2135 Set threshold of queued
2136 RCU callbacks over which batch limiting is disabled.
2138 rcupdate.qlowmark= [KNL,BOOT]
2139 Set threshold of queued RCU callbacks below which
2140 batch limiting is re-enabled.
2142 rdinit= [KNL]
2143 Format: <full_path>
2144 Run specified binary instead of /init from the ramdisk,
2145 used for early userspace startup. See initrd.
2147 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2148 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2149 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2151 relax_domain_level=
2152 [KNL, SMP] Set scheduler's default relax_domain_level.
2153 See Documentation/cgroups/cpusets.txt.
2155 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2157 reservetop= [X86-32]
2158 Format: nn[KMG]
2159 Reserves a hole at the top of the kernel virtual
2160 address space.
2162 reset_devices [KNL] Force drivers to reset the underlying device
2163 during initialization.
2165 resume= [SWSUSP]
2166 Specify the partition device for software suspend
2168 resume_offset= [SWSUSP]
2169 Specify the offset from the beginning of the partition
2170 given by "resume=" at which the swap header is located,
2171 in <PAGE_SIZE> units (needed only for swap files).
2172 See Documentation/power/swsusp-and-swap-files.txt
2174 retain_initrd [RAM] Keep initrd memory after extraction
2176 rhash_entries= [KNL,NET]
2177 Set number of hash buckets for route cache
2179 riscom8= [HW,SERIAL]
2180 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2182 ro [KNL] Mount root device read-only on boot
2184 root= [KNL] Root filesystem
2186 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2187 mount the root filesystem
2189 rootflags= [KNL] Set root filesystem mount option string
2191 rootfstype= [KNL] Set root filesystem type
2193 rootwait [KNL] Wait (indefinitely) for root device to show up.
2194 Useful for devices that are detected asynchronously
2195 (e.g. USB and MMC devices).
2197 rw [KNL] Mount root device read-write on boot
2199 S [KNL] Run init in single mode
2201 sa1100ir [NET]
2202 See drivers/net/irda/sa1100_ir.c.
2204 sbni= [NET] Granch SBNI12 leased line adapter
2206 sched_debug [KNL] Enables verbose scheduler debug messages.
2208 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2209 Format: <io>[,<timeout>[,<isapnp>]]
2211 scsi_debug_*= [SCSI]
2212 See drivers/scsi/scsi_debug.c.
2214 scsi_default_dev_flags=
2215 [SCSI] SCSI default device flags
2216 Format: <integer>
2218 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2219 Format: <vendor>:<model>:<flags>
2220 (flags are integer value)
2222 scsi_logging_level= [SCSI] a bit mask of logging levels
2223 See drivers/scsi/scsi_logging.h for bits. Also
2224 settable via sysctl at dev.scsi.logging_level
2225 (/proc/sys/dev/scsi/logging_level).
2226 There is also a nice 'scsi_logging_level' script in the
2227 S390-tools package, available for download at
2228 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2230 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2231 discovered. async scans them in kernel threads,
2232 allowing boot to proceed. none ignores them, expecting
2233 user space to do the scan.
2235 security= [SECURITY] Choose a security module to enable at boot.
2236 If this boot parameter is not specified, only the first
2237 security module asking for security registration will be
2238 loaded. An invalid security module name will be treated
2239 as if no module has been chosen.
2241 selinux= [SELINUX] Disable or enable SELinux at boot time.
2242 Format: { "0" | "1" }
2243 See security/selinux/Kconfig help text.
2244 0 -- disable.
2245 1 -- enable.
2246 Default value is set via kernel config option.
2247 If enabled at boot time, /selinux/disable can be used
2248 later to disable prior to initial policy load.
2250 serialnumber [BUGS=X86-32]
2252 shapers= [NET]
2253 Maximal number of shapers.
2255 show_msr= [x86] show boot-time MSR settings
2256 Format: { <integer> }
2257 Show boot-time (BIOS-initialized) MSR settings.
2258 The parameter means the number of CPUs to show,
2259 for example 1 means boot CPU only.
2261 sim710= [SCSI,HW]
2262 See header of drivers/scsi/sim710.c.
2264 simeth= [IA-64]
2265 simscsi=
2267 slram= [HW,MTD]
2269 slub_debug[=options[,slabs]] [MM, SLUB]
2270 Enabling slub_debug allows one to determine the
2271 culprit if slab objects become corrupted. Enabling
2272 slub_debug can create guard zones around objects and
2273 may poison objects when not in use. Also tracks the
2274 last alloc / free. For more information see
2275 Documentation/vm/slub.txt.
2277 slub_max_order= [MM, SLUB]
2278 Determines the maximum allowed order for slabs.
2279 A high setting may cause OOMs due to memory
2280 fragmentation. For more information see
2281 Documentation/vm/slub.txt.
2283 slub_min_objects= [MM, SLUB]
2284 The minimum number of objects per slab. SLUB will
2285 increase the slab order up to slub_max_order to
2286 generate a sufficiently large slab able to contain
2287 the number of objects indicated. The higher the number
2288 of objects the smaller the overhead of tracking slabs
2289 and the less frequently locks need to be acquired.
2290 For more information see Documentation/vm/slub.txt.
2292 slub_min_order= [MM, SLUB]
2293 Determines the mininum page order for slabs. Must be
2294 lower than slub_max_order.
2295 For more information see Documentation/vm/slub.txt.
2297 slub_nomerge [MM, SLUB]
2298 Disable merging of slabs with similar size. May be
2299 necessary if there is some reason to distinguish
2300 allocs to different slabs. Debug options disable
2301 merging on their own.
2302 For more information see Documentation/vm/slub.txt.
2304 smart2= [HW]
2305 Format: <io1>[,<io2>[,...,<io8>]]
2307 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2308 attempt to substitute SMP alternatives once at boot.
2310 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2311 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2312 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2313 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2314 smsc-ircc2.ircc_irq= [HW] IRQ line
2315 smsc-ircc2.ircc_dma= [HW] DMA channel
2316 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2317 0: Toshiba Satellite 1800 (GP data pin select)
2318 1: Fast pin select (default)
2319 2: ATC IRMode
2321 snd-ad1816a= [HW,ALSA]
2323 snd-ad1848= [HW,ALSA]
2325 snd-ali5451= [HW,ALSA]
2327 snd-als100= [HW,ALSA]
2329 snd-als4000= [HW,ALSA]
2331 snd-azt2320= [HW,ALSA]
2333 snd-cmi8330= [HW,ALSA]
2335 snd-cmipci= [HW,ALSA]
2337 snd-cs4231= [HW,ALSA]
2339 snd-cs4232= [HW,ALSA]
2341 snd-cs4236= [HW,ALSA]
2343 snd-cs4281= [HW,ALSA]
2345 snd-cs46xx= [HW,ALSA]
2347 snd-dt019x= [HW,ALSA]
2349 snd-dummy= [HW,ALSA]
2351 snd-emu10k1= [HW,ALSA]
2353 snd-ens1370= [HW,ALSA]
2355 snd-ens1371= [HW,ALSA]
2357 snd-es968= [HW,ALSA]
2359 snd-es1688= [HW,ALSA]
2361 snd-es18xx= [HW,ALSA]
2363 snd-es1938= [HW,ALSA]
2365 snd-es1968= [HW,ALSA]
2367 snd-fm801= [HW,ALSA]
2369 snd-gusclassic= [HW,ALSA]
2371 snd-gusextreme= [HW,ALSA]
2373 snd-gusmax= [HW,ALSA]
2375 snd-hdsp= [HW,ALSA]
2377 snd-ice1712= [HW,ALSA]
2379 snd-intel8x0= [HW,ALSA]
2381 snd-interwave= [HW,ALSA]
2383 snd-interwave-stb=
2384 [HW,ALSA]
2386 snd-korg1212= [HW,ALSA]
2388 snd-maestro3= [HW,ALSA]
2390 snd-mpu401= [HW,ALSA]
2392 snd-mtpav= [HW,ALSA]
2394 snd-nm256= [HW,ALSA]
2396 snd-opl3sa2= [HW,ALSA]
2398 snd-opti92x-ad1848=
2399 [HW,ALSA]
2401 snd-opti92x-cs4231=
2402 [HW,ALSA]
2404 snd-opti93x= [HW,ALSA]
2406 snd-pmac= [HW,ALSA]
2408 snd-rme32= [HW,ALSA]
2410 snd-rme96= [HW,ALSA]
2412 snd-rme9652= [HW,ALSA]
2414 snd-sb8= [HW,ALSA]
2416 snd-sb16= [HW,ALSA]
2418 snd-sbawe= [HW,ALSA]
2420 snd-serial= [HW,ALSA]
2422 snd-sgalaxy= [HW,ALSA]
2424 snd-sonicvibes= [HW,ALSA]
2426 snd-sun-amd7930=
2427 [HW,ALSA]
2429 snd-sun-cs4231= [HW,ALSA]
2431 snd-trident= [HW,ALSA]
2433 snd-usb-audio= [HW,ALSA,USB]
2435 snd-via82xx= [HW,ALSA]
2437 snd-virmidi= [HW,ALSA]
2439 snd-wavefront= [HW,ALSA]
2441 snd-ymfpci= [HW,ALSA]
2443 softlockup_panic=
2444 [KNL] Should the soft-lockup detector generate panics.
2446 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2447 See Documentation/sonypi.txt
2449 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2450 See Documentation/serial/specialix.txt.
2452 spia_io_base= [HW,MTD]
2453 spia_fio_base=
2454 spia_pedr=
2455 spia_peddr=
2457 sscape= [HW,OSS]
2458 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2460 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2461 See Documentation/scsi/st.txt.
2463 stacktrace [FTRACE]
2464 Enabled the stack tracer on boot up.
2466 sti= [PARISC,HW]
2467 Format: <num>
2468 Set the STI (builtin display/keyboard on the HP-PARISC
2469 machines) console (graphic card) which should be used
2470 as the initial boot-console.
2471 See also comment in drivers/video/console/sticore.c.
2473 sti_font= [HW]
2474 See comment in drivers/video/console/sticore.c.
2476 stifb= [HW]
2477 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2479 sunrpc.min_resvport=
2480 sunrpc.max_resvport=
2481 [NFS,SUNRPC]
2482 SunRPC servers often require that client requests
2483 originate from a privileged port (i.e. a port in the
2484 range 0 < portnr < 1024).
2485 An administrator who wishes to reserve some of these
2486 ports for other uses may adjust the range that the
2487 kernel's sunrpc client considers to be privileged
2488 using these two parameters to set the minimum and
2489 maximum port values.
2491 sunrpc.pool_mode=
2492 [NFS]
2493 Control how the NFS server code allocates CPUs to
2494 service thread pools. Depending on how many NICs
2495 you have and where their interrupts are bound, this
2496 option will affect which CPUs will do NFS serving.
2497 Note: this parameter cannot be changed while the
2498 NFS server is running.
2500 auto the server chooses an appropriate mode
2501 automatically using heuristics
2502 global a single global pool contains all CPUs
2503 percpu one pool for each CPU
2504 pernode one pool for each NUMA node (equivalent
2505 to global on non-NUMA machines)
2507 sunrpc.tcp_slot_table_entries=
2508 sunrpc.udp_slot_table_entries=
2509 [NFS,SUNRPC]
2510 Sets the upper limit on the number of simultaneous
2511 RPC calls that can be sent from the client to a
2512 server. Increasing these values may allow you to
2513 improve throughput, but will also increase the
2514 amount of memory reserved for use by the client.
2516 swiotlb= [IA-64] Number of I/O TLB slabs
2518 switches= [HW,M68k]
2520 sym53c416= [HW,SCSI]
2521 See header of drivers/scsi/sym53c416.c.
2523 sysrq_always_enabled
2524 [KNL]
2525 Ignore sysrq setting - this boot parameter will
2526 neutralize any effect of /proc/sys/kernel/sysrq.
2527 Useful for debugging.
2529 t128= [HW,SCSI]
2530 See header of drivers/scsi/t128.c.
2532 tdfx= [HW,DRM]
2534 test_suspend= [SUSPEND]
2535 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2536 standby suspend) as the system sleep state to briefly
2537 enter during system startup. The system is woken from
2538 this state using a wakeup-capable RTC alarm.
2540 thash_entries= [KNL,NET]
2541 Set number of hash buckets for TCP connection
2543 thermal.act= [HW,ACPI]
2544 -1: disable all active trip points in all thermal zones
2545 <degrees C>: override all lowest active trip points
2547 thermal.crt= [HW,ACPI]
2548 -1: disable all critical trip points in all thermal zones
2549 <degrees C>: override all critical trip points
2551 thermal.nocrt= [HW,ACPI]
2552 Set to disable actions on ACPI thermal zone
2553 critical and hot trip points.
2555 thermal.off= [HW,ACPI]
2556 1: disable ACPI thermal control
2558 thermal.psv= [HW,ACPI]
2559 -1: disable all passive trip points
2560 <degrees C>: override all passive trip points to this
2561 value
2563 thermal.tzp= [HW,ACPI]
2564 Specify global default ACPI thermal zone polling rate
2565 <deci-seconds>: poll all this frequency
2566 0: no polling (default)
2568 tmscsim= [HW,SCSI]
2569 See comment before function dc390_setup() in
2570 drivers/scsi/tmscsim.c.
2572 topology= [S390]
2573 Format: {off | on}
2574 Specify if the kernel should make use of the cpu
2575 topology informations if the hardware supports these.
2576 The scheduler will make use of these informations and
2577 e.g. base its process migration decisions on it.
2578 Default is off.
2580 tp720= [HW,PS2]
2582 trace_buf_size=nn[KMG]
2583 [FTRACE] will set tracing buffer size.
2585 trace_event=[event-list]
2586 [FTRACE] Set and start specified trace events in order
2587 to facilitate early boot debugging.
2588 See also Documentation/trace/events.txt
2590 trix= [HW,OSS] MediaTrix AudioTrix Pro
2591 Format:
2592 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2594 tsc= Disable clocksource-must-verify flag for TSC.
2595 Format: <string>
2596 [x86] reliable: mark tsc clocksource as reliable, this
2597 disables clocksource verification at runtime.
2598 Used to enable high-resolution timer mode on older
2599 hardware, and in virtualized environment.
2601 turbografx.map[2|3]= [HW,JOY]
2602 TurboGraFX parallel port interface
2603 Format:
2604 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2605 See also Documentation/input/joystick-parport.txt
2607 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2608 See header of drivers/scsi/u14-34f.c.
2610 uart401= [HW,OSS]
2611 Format: <io>,<irq>
2613 uart6850= [HW,OSS]
2614 Format: <io>,<irq>
2616 uhash_entries= [KNL,NET]
2617 Set number of hash buckets for UDP/UDP-Lite connections
2619 uhci-hcd.ignore_oc=
2620 [USB] Ignore overcurrent events (default N).
2621 Some badly-designed motherboards generate lots of
2622 bogus events, for ports that aren't wired to
2623 anything. Set this parameter to avoid log spamming.
2624 Note that genuine overcurrent events won't be
2625 reported either.
2627 unknown_nmi_panic
2628 [X86]
2629 Set unknown_nmi_panic=1 early on boot.
2631 usbcore.autosuspend=
2632 [USB] The autosuspend time delay (in seconds) used
2633 for newly-detected USB devices (default 2). This
2634 is the time required before an idle device will be
2635 autosuspended. Devices for which the delay is set
2636 to a negative value won't be autosuspended at all.
2638 usbcore.usbfs_snoop=
2639 [USB] Set to log all usbfs traffic (default 0 = off).
2641 usbcore.blinkenlights=
2642 [USB] Set to cycle leds on hubs (default 0 = off).
2644 usbcore.old_scheme_first=
2645 [USB] Start with the old device initialization
2646 scheme (default 0 = off).
2648 usbcore.use_both_schemes=
2649 [USB] Try the other device initialization scheme
2650 if the first one fails (default 1 = enabled).
2652 usbcore.initial_descriptor_timeout=
2653 [USB] Specifies timeout for the initial 64-byte
2654 USB_REQ_GET_DESCRIPTOR request in milliseconds
2655 (default 5000 = 5.0 seconds).
2657 usbhid.mousepoll=
2658 [USBHID] The interval which mice are to be polled at.
2660 usb-storage.delay_use=
2661 [UMS] The delay in seconds before a new device is
2662 scanned for Logical Units (default 5).
2664 usb-storage.quirks=
2665 [UMS] A list of quirks entries to supplement or
2666 override the built-in unusual_devs list. List
2667 entries are separated by commas. Each entry has
2668 the form VID:PID:Flags where VID and PID are Vendor
2669 and Product ID values (4-digit hex numbers) and
2670 Flags is a set of characters, each corresponding
2671 to a common usb-storage quirk flag as follows:
2672 a = SANE_SENSE (collect more than 18 bytes
2673 of sense data);
2674 b = BAD_SENSE (don't collect more than 18
2675 bytes of sense data);
2676 c = FIX_CAPACITY (decrease the reported
2677 device capacity by one sector);
2678 h = CAPACITY_HEURISTICS (decrease the
2679 reported device capacity by one
2680 sector if the number is odd);
2681 i = IGNORE_DEVICE (don't bind to this
2682 device);
2683 l = NOT_LOCKABLE (don't try to lock and
2684 unlock ejectable media);
2685 m = MAX_SECTORS_64 (don't transfer more
2686 than 64 sectors = 32 KB at a time);
2687 o = CAPACITY_OK (accept the capacity
2688 reported by the device);
2689 r = IGNORE_RESIDUE (the device reports
2690 bogus residue values);
2691 s = SINGLE_LUN (the device has only one
2692 Logical Unit);
2693 w = NO_WP_DETECT (don't test whether the
2694 medium is write-protected).
2695 Example: quirks=0419:aaf5:rl,0421:0433:rc
2697 vdso= [X86,SH]
2698 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2699 vdso=1: enable VDSO (default)
2700 vdso=0: disable VDSO mapping
2702 vdso32= [X86]
2703 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2704 vdso32=1: enable 32-bit VDSO (default)
2705 vdso32=0: disable 32-bit VDSO mapping
2707 vector= [IA-64,SMP]
2708 vector=percpu: enable percpu vector domain
2710 video= [FB] Frame buffer configuration
2711 See Documentation/fb/modedb.txt.
2713 vga= [BOOT,X86-32] Select a particular video mode
2714 See Documentation/x86/boot.txt and
2715 Documentation/svga.txt.
2716 Use vga=ask for menu.
2717 This is actually a boot loader parameter; the value is
2718 passed to the kernel using a special protocol.
2720 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2721 size of <nn>. This can be used to increase the
2722 minimum size (128MB on x86). It can also be used to
2723 decrease the size and leave more room for directly
2724 mapped kernel RAM.
2726 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2727 Format: <command>
2729 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2730 Format: <command>
2732 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2733 Format: <command>
2735 vt.cur_default= [VT] Default cursor shape.
2736 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2737 the parameters of the <Esc>[?A;B;Cc escape sequence;
2738 see VGA-softcursor.txt. Default: 2 = underline.
2740 vt.default_blu= [VT]
2741 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2742 Change the default blue palette of the console.
2743 This is a 16-member array composed of values
2744 ranging from 0-255.
2746 vt.default_grn= [VT]
2747 Format: <green0>,<green1>,<green2>,...,<green15>
2748 Change the default green palette of the console.
2749 This is a 16-member array composed of values
2750 ranging from 0-255.
2752 vt.default_red= [VT]
2753 Format: <red0>,<red1>,<red2>,...,<red15>
2754 Change the default red palette of the console.
2755 This is a 16-member array composed of values
2756 ranging from 0-255.
2758 vt.default_utf8=
2759 [VT]
2760 Format=<0|1>
2761 Set system-wide default UTF-8 mode for all tty's.
2762 Default is 1, i.e. UTF-8 mode is enabled for all
2763 newly opened terminals.
2765 vt.global_cursor_default=
2766 [VT]
2767 Format=<-1|0|1>
2768 Set system-wide default for whether a cursor
2769 is shown on new VTs. Default is -1,
2770 i.e. cursors will be created by default unless
2771 overridden by individual drivers. 0 will hide
2772 cursors, 1 will display them.
2774 waveartist= [HW,OSS]
2775 Format: <io>,<irq>,<dma>,<dma2>
2777 wd33c93= [HW,SCSI]
2778 See header of drivers/scsi/wd33c93.c.
2780 wd7000= [HW,SCSI]
2781 See header of drivers/scsi/wd7000.c.
2783 wdt= [WDT] Watchdog
2784 See Documentation/watchdog/wdt.txt.
2786 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2787 default x2apic cluster mode on platforms
2788 supporting x2apic.
2790 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2791 xd_geo= See header of drivers/block/xd.c.
2793 xirc2ps_cs= [NET,PCMCIA]
2794 Format:
2795 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2797 ______________________________________________________________________
2799 TODO:
2801 Add documentation for ALSA options.
2802 Add more DRM drivers.