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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 ROOTPLUG The example Root Plug LSM is enabled.
89 S390 S390 architecture is enabled.
90 SCSI Appropriate SCSI support is enabled.
91 A lot of drivers has their options described inside of
92 Documentation/scsi/.
93 SECURITY Different security models are enabled.
94 SELINUX SELinux support is enabled.
95 SERIAL Serial support is enabled.
96 SH SuperH architecture is enabled.
97 SMP The kernel is an SMP kernel.
98 SPARC Sparc architecture is enabled.
99 SWSUSP Software suspend (hibernation) is enabled.
100 SUSPEND System suspend states are enabled.
101 FTRACE Function tracing enabled.
102 TS Appropriate touchscreen support is enabled.
103 UMS USB Mass Storage support is enabled.
104 USB USB support is enabled.
105 USBHID USB Human Interface Device support is enabled.
106 V4L Video For Linux support is enabled.
107 VGA The VGA console has been enabled.
108 VT Virtual terminal support is enabled.
109 WDT Watchdog support is enabled.
110 XT IBM PC/XT MFM hard disk support is enabled.
111 X86-32 X86-32, aka i386 architecture is enabled.
112 X86-64 X86-64 architecture is enabled.
113 More X86-64 boot options can be found in
114 Documentation/x86/x86_64/boot-options.txt .
115 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
117 In addition, the following text indicates that the option:
119 BUGS= Relates to possible processor bugs on the said processor.
120 KNL Is a kernel start-up parameter.
121 BOOT Is a boot loader parameter.
123 Parameters denoted with BOOT are actually interpreted by the boot
124 loader, and have no meaning to the kernel directly.
125 Do not modify the syntax of boot loader parameters without extreme
126 need or coordination with <Documentation/x86/boot.txt>.
128 There are also arch-specific kernel-parameters not documented here.
129 See for example <Documentation/x86/x86_64/boot-options.txt>.
131 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
132 a trailing = on the name of any parameter states that that parameter will
133 be entered as an environment variable, whereas its absence indicates that
134 it will appear as a kernel argument readable via /proc/cmdline by programs
135 running once the system is up.
137 The number of kernel parameters is not limited, but the length of the
138 complete command line (parameters including spaces etc.) is limited to
139 a fixed number of characters. This limit depends on the architecture
140 and is between 256 and 4096 characters. It is defined in the file
141 ./include/asm/setup.h as COMMAND_LINE_SIZE.
144 acpi= [HW,ACPI,X86]
145 Advanced Configuration and Power Interface
146 Format: { force | off | ht | strict | noirq | rsdt }
147 force -- enable ACPI if default was off
148 off -- disable ACPI if default was on
149 noirq -- do not use ACPI for IRQ routing
150 ht -- run only enough ACPI to enable Hyper Threading
151 strict -- Be less tolerant of platforms that are not
152 strictly ACPI specification compliant.
153 rsdt -- prefer RSDT over (default) XSDT
155 See also Documentation/power/pm.txt, pci=noacpi
157 acpi_apic_instance= [ACPI, IOAPIC]
158 Format: <int>
159 2: use 2nd APIC table, if available
160 1,0: use 1st APIC table
161 default: 0
163 acpi_backlight= [HW,ACPI]
164 acpi_backlight=vendor
165 acpi_backlight=video
166 If set to vendor, prefer vendor specific driver
167 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
168 of the ACPI video.ko driver.
170 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
171 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
172 Format: <int>
173 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
174 debug output. Bits in debug_layer correspond to a
175 _COMPONENT in an ACPI source file, e.g.,
176 #define _COMPONENT ACPI_PCI_COMPONENT
177 Bits in debug_level correspond to a level in
178 ACPI_DEBUG_PRINT statements, e.g.,
179 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
180 The debug_level mask defaults to "info". See
181 Documentation/acpi/debug.txt for more information about
182 debug layers and levels.
184 Enable processor driver info messages:
185 acpi.debug_layer=0x20000000
186 Enable PCI/PCI interrupt routing info messages:
187 acpi.debug_layer=0x400000
188 Enable AML "Debug" output, i.e., stores to the Debug
189 object while interpreting AML:
190 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
191 Enable all messages related to ACPI hardware:
192 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
194 Some values produce so much output that the system is
195 unusable. The "log_buf_len" parameter may be useful
196 if you need to capture more output.
198 acpi_display_output= [HW,ACPI]
199 acpi_display_output=vendor
200 acpi_display_output=video
201 See above.
203 acpi_irq_balance [HW,ACPI]
204 ACPI will balance active IRQs
205 default in APIC mode
207 acpi_irq_nobalance [HW,ACPI]
208 ACPI will not move active IRQs (default)
209 default in PIC mode
211 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
212 Format: <irq>,<irq>...
214 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
215 use by PCI
216 Format: <irq>,<irq>...
218 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
220 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
221 Format: To spoof as Windows 98: ="Microsoft Windows"
223 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
224 acpi_osi="string1" # add string1 -- only one string
225 acpi_osi="!string2" # remove built-in string2
226 acpi_osi= # disable all strings
228 acpi_pm_good [X86]
229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
233 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
234 Format: { level | edge | high | low }
236 acpi_serialize [HW,ACPI] force serialization of AML methods
238 acpi_skip_timer_override [HW,ACPI]
239 Recognize and ignore IRQ0/pin2 Interrupt Override.
240 For broken nForce2 BIOS resulting in XT-PIC timer.
242 acpi_sleep= [HW,ACPI] Sleep options
243 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
244 old_ordering, s4_nonvs }
245 See Documentation/power/video.txt for information on
246 s3_bios and s3_mode.
247 s3_beep is for debugging; it makes the PC's speaker beep
248 as soon as the kernel's real-mode entry point is called.
249 s4_nohwsig prevents ACPI hardware signature from being
250 used during resume from hibernation.
251 old_ordering causes the ACPI 1.0 ordering of the _PTS
252 control method, with respect to putting devices into
253 low power states, to be enforced (the ACPI 2.0 ordering
254 of _PTS is used by default).
255 s4_nonvs prevents the kernel from saving/restoring the
256 ACPI NVS memory during hibernation.
258 acpi_use_timer_override [HW,ACPI]
259 Use timer override. For some broken Nvidia NF5 boards
260 that require a timer override, but don't have HPET
262 acpi_enforce_resources= [ACPI]
263 { strict | lax | no }
264 Check for resource conflicts between native drivers
265 and ACPI OperationRegions (SystemIO and SystemMemory
266 only). IO ports and memory declared in ACPI might be
267 used by the ACPI subsystem in arbitrary AML code and
268 can interfere with legacy drivers.
269 strict (default): access to resources claimed by ACPI
270 is denied; legacy drivers trying to access reserved
271 resources will fail to bind to device using them.
272 lax: access to resources claimed by ACPI is allowed;
273 legacy drivers trying to access reserved resources
274 will bind successfully but a warning message is logged.
275 no: ACPI OperationRegions are not marked as reserved,
276 no further checks are performed.
278 ad1848= [HW,OSS]
279 Format: <io>,<irq>,<dma>,<dma2>,<type>
281 add_efi_memmap [EFI; X86] Include EFI memory map in
282 kernel's map of available physical RAM.
284 advansys= [HW,SCSI]
285 See header of drivers/scsi/advansys.c.
287 advwdt= [HW,WDT] Advantech WDT
288 Format: <iostart>,<iostop>
290 aedsp16= [HW,OSS] Audio Excel DSP 16
291 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
292 See also header of sound/oss/aedsp16.c.
294 agp= [AGP]
295 { off | try_unsupported }
296 off: disable AGP support
297 try_unsupported: try to drive unsupported chipsets
298 (may crash computer or cause data corruption)
300 aha152x= [HW,SCSI]
301 See Documentation/scsi/aha152x.txt.
303 aha1542= [HW,SCSI]
304 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
306 aic7xxx= [HW,SCSI]
307 See Documentation/scsi/aic7xxx.txt.
309 aic79xx= [HW,SCSI]
310 See Documentation/scsi/aic79xx.txt.
312 amd_iommu= [HW,X86-84]
313 Pass parameters to the AMD IOMMU driver in the system.
314 Possible values are:
315 isolate - enable device isolation (each device, as far
316 as possible, will get its own protection
317 domain) [default]
318 share - put every device behind one IOMMU into the
319 same protection domain
320 fullflush - enable flushing of IO/TLB entries when
321 they are unmapped. Otherwise they are
322 flushed before they will be reused, which
323 is a lot of faster
325 amijoy.map= [HW,JOY] Amiga joystick support
326 Map of devices attached to JOY0DAT and JOY1DAT
327 Format: <a>,<b>
328 See also Documentation/kernel/input/joystick.txt
330 analog.map= [HW,JOY] Analog joystick and gamepad support
331 Specifies type or capabilities of an analog joystick
332 connected to one of 16 gameports
333 Format: <type1>,<type2>,..<type16>
335 apc= [HW,SPARC]
336 Power management functions (SPARCstation-4/5 + deriv.)
337 Format: noidle
338 Disable APC CPU standby support. SPARCstation-Fox does
339 not play well with APC CPU idle - disable it if you have
340 APC and your system crashes randomly.
342 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
343 Change the output verbosity whilst booting
344 Format: { quiet (default) | verbose | debug }
345 Change the amount of debugging information output
346 when initialising the APIC and IO-APIC components.
348 apm= [APM] Advanced Power Management
349 See header of arch/x86/kernel/apm_32.c.
351 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
352 Format: <io>,<irq>,<nodeID>
354 ataflop= [HW,M68k]
356 atarimouse= [HW,MOUSE] Atari Mouse
358 atascsi= [HW,SCSI] Atari SCSI
360 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
361 EzKey and similar keyboards
363 atkbd.reset= [HW] Reset keyboard during initialization
365 atkbd.set= [HW] Select keyboard code set
366 Format: <int> (2 = AT (default), 3 = PS/2)
368 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
369 keyboards
371 atkbd.softraw= [HW] Choose between synthetic and real raw mode
372 Format: <bool> (0 = real, 1 = synthetic (default))
374 atkbd.softrepeat= [HW]
375 Use software keyboard repeat
377 autotest [IA64]
379 baycom_epp= [HW,AX25]
380 Format: <io>,<mode>
382 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
383 Format: <io>,<mode>
384 See header of drivers/net/hamradio/baycom_par.c.
386 baycom_ser_fdx= [HW,AX25]
387 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
388 Format: <io>,<irq>,<mode>[,<baud>]
389 See header of drivers/net/hamradio/baycom_ser_fdx.c.
391 baycom_ser_hdx= [HW,AX25]
392 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
393 Format: <io>,<irq>,<mode>
394 See header of drivers/net/hamradio/baycom_ser_hdx.c.
396 boot_delay= Milliseconds to delay each printk during boot.
397 Values larger than 10 seconds (10000) are changed to
398 no delay (0).
399 Format: integer
401 bootmem_debug [KNL] Enable bootmem allocator debug messages.
403 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
404 bttv.radio= Most important insmod options are available as
405 kernel args too.
406 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
407 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
409 BusLogic= [HW,SCSI]
410 See drivers/scsi/BusLogic.c, comment before function
411 BusLogic_ParseDriverOptions().
413 c101= [NET] Moxa C101 synchronous serial card
415 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
416 Sometimes CPU hardware bugs make them report the cache
417 size incorrectly. The kernel will attempt work arounds
418 to fix known problems, but for some CPUs it is not
419 possible to determine what the correct size should be.
420 This option provides an override for these situations.
422 capability.disable=
423 [SECURITY] Disable capabilities. This would normally
424 be used only if an alternative security model is to be
425 configured. Potentially dangerous and should only be
426 used if you are entirely sure of the consequences.
428 ccw_timeout_log [S390]
429 See Documentation/s390/CommonIO for details.
431 cgroup_disable= [KNL] Disable a particular controller
432 Format: {name of the controller(s) to disable}
433 {Currently supported controllers - "memory"}
435 checkreqprot [SELINUX] Set initial checkreqprot flag value.
436 Format: { "0" | "1" }
437 See security/selinux/Kconfig help text.
438 0 -- check protection applied by kernel (includes
439 any implied execute protection).
440 1 -- check protection requested by application.
441 Default value is set via a kernel config option.
442 Value can be changed at runtime via
443 /selinux/checkreqprot.
445 cio_ignore= [S390]
446 See Documentation/s390/CommonIO for details.
448 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
449 [Deprecated]
450 Forces specified clocksource (if available) to be used
451 when calculating gettimeofday(). If specified
452 clocksource is not available, it defaults to PIT.
453 Format: { pit | tsc | cyclone | pmtmr }
455 clocksource= [GENERIC_TIME] Override the default clocksource
456 Format: <string>
457 Override the default clocksource and use the clocksource
458 with the name specified.
459 Some clocksource names to choose from, depending on
460 the platform:
461 [all] jiffies (this is the base, fallback clocksource)
462 [ACPI] acpi_pm
463 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
464 pxa_timer,timer3,32k_counter,timer0_1
465 [AVR32] avr32
466 [X86-32] pit,hpet,tsc,vmi-timer;
467 scx200_hrt on Geode; cyclone on IBM x440
468 [MIPS] MIPS
469 [PARISC] cr16
470 [S390] tod
471 [SH] SuperH
472 [SPARC64] tick
473 [X86-64] hpet,tsc
475 clearcpuid=BITNUM [X86]
476 Disable CPUID feature X for the kernel. See
477 arch/x86/include/asm/cpufeature.h for the valid bit
478 numbers. Note the Linux specific bits are not necessarily
479 stable over kernel options, but the vendor specific
480 ones should be.
481 Also note that user programs calling CPUID directly
482 or using the feature without checking anything
483 will still see it. This just prevents it from
484 being used by the kernel or shown in /proc/cpuinfo.
485 Also note the kernel might malfunction if you disable
486 some critical bits.
488 cmo_free_hint= [PPC] Format: { yes | no }
489 Specify whether pages are marked as being inactive
490 when they are freed. This is used in CMO environments
491 to determine OS memory pressure for page stealing by
492 a hypervisor.
493 Default: yes
495 code_bytes [X86] How many bytes of object code to print
496 in an oops report.
497 Range: 0 - 8192
498 Default: 64
500 com20020= [HW,NET] ARCnet - COM20020 chipset
501 Format:
502 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
504 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
505 Format: <io>[,<irq>]
507 com90xx= [HW,NET]
508 ARCnet - COM90xx chipset (memory-mapped buffers)
509 Format: <io>[,<irq>[,<memstart>]]
511 condev= [HW,S390] console device
512 conmode=
514 console= [KNL] Output console device and options.
516 tty<n> Use the virtual console device <n>.
518 ttyS<n>[,options]
519 ttyUSB0[,options]
520 Use the specified serial port. The options are of
521 the form "bbbbpnf", where "bbbb" is the baud rate,
522 "p" is parity ("n", "o", or "e"), "n" is number of
523 bits, and "f" is flow control ("r" for RTS or
524 omit it). Default is "9600n8".
526 See Documentation/serial-console.txt for more
527 information. See
528 Documentation/networking/netconsole.txt for an
529 alternative.
531 uart[8250],io,<addr>[,options]
532 uart[8250],mmio,<addr>[,options]
533 Start an early, polled-mode console on the 8250/16550
534 UART at the specified I/O port or MMIO address,
535 switching to the matching ttyS device later. The
536 options are the same as for ttyS, above.
538 If the device connected to the port is not a TTY but a braille
539 device, prepend "brl," before the device type, for instance
540 console=brl,ttyS0
541 For now, only VisioBraille is supported.
543 consoleblank= [KNL] The console blank (screen saver) timeout in
544 seconds. Defaults to 10*60 = 10mins. A value of 0
545 disables the blank timer.
547 coredump_filter=
548 [KNL] Change the default value for
549 /proc/<pid>/coredump_filter.
550 See also Documentation/filesystems/proc.txt.
552 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
553 Format:
554 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
556 crashkernel=nn[KMG]@ss[KMG]
557 [KNL] Reserve a chunk of physical memory to
558 hold a kernel to switch to with kexec on panic.
560 crashkernel=range1:size1[,range2:size2,...][@offset]
561 [KNL] Same as above, but depends on the memory
562 in the running system. The syntax of range is
563 start-[end] where start and end are both
564 a memory unit (amount[KMG]). See also
565 Documentation/kdump/kdump.txt for a example.
567 cs89x0_dma= [HW,NET]
568 Format: <dma>
570 cs89x0_media= [HW,NET]
571 Format: { rj45 | aui | bnc }
573 dasd= [HW,NET]
574 See header of drivers/s390/block/dasd_devmap.c.
576 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
577 (one device per port)
578 Format: <port#>,<type>
579 See also Documentation/input/joystick-parport.txt
581 debug [KNL] Enable kernel debugging (events log level).
583 debug_locks_verbose=
584 [KNL] verbose self-tests
585 Format=<0|1>
586 Print debugging info while doing the locking API
587 self-tests.
588 We default to 0 (no extra messages), setting it to
589 1 will print _a lot_ more information - normally
590 only useful to kernel developers.
592 debug_objects [KNL] Enable object debugging
594 no_debug_objects
595 [KNL] Disable object debugging
597 debugpat [X86] Enable PAT debugging
599 decnet.addr= [HW,NET]
600 Format: <area>[,<node>]
601 See also Documentation/networking/decnet.txt.
603 default_hugepagesz=
604 [same as hugepagesz=] The size of the default
605 HugeTLB page size. This is the size represented by
606 the legacy /proc/ hugepages APIs, used for SHM, and
607 default size when mounting hugetlbfs filesystems.
608 Defaults to the default architecture's huge page size
609 if not specified.
611 dhash_entries= [KNL]
612 Set number of hash buckets for dentry cache.
614 digi= [HW,SERIAL]
615 IO parameters + enable/disable command.
617 digiepca= [HW,SERIAL]
618 See drivers/char/README.epca and
619 Documentation/serial/digiepca.txt.
621 disable_mtrr_cleanup [X86]
622 The kernel tries to adjust MTRR layout from continuous
623 to discrete, to make X server driver able to add WB
624 entry later. This parameter disables that.
626 disable_mtrr_trim [X86, Intel and AMD only]
627 By default the kernel will trim any uncacheable
628 memory out of your available memory pool based on
629 MTRR settings. This parameter disables that behavior,
630 possibly causing your machine to run very slowly.
632 disable_timer_pin_1 [X86]
633 Disable PIN 1 of APIC timer
634 Can be useful to work around chipset bugs.
636 dmasound= [HW,OSS] Sound subsystem buffers
638 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
639 this option disables the debugging code at boot.
641 dma_debug_entries=<number>
642 This option allows to tune the number of preallocated
643 entries for DMA-API debugging code. One entry is
644 required per DMA-API allocation. Use this if the
645 DMA-API debugging code disables itself because the
646 architectural default is too low.
648 dma_debug_driver=<driver_name>
649 With this option the DMA-API debugging driver
650 filter feature can be enabled at boot time. Just
651 pass the driver to filter for as the parameter.
652 The filter can be disabled or changed to another
653 driver later using sysfs.
655 dscc4.setup= [NET]
657 dtc3181e= [HW,SCSI]
659 dynamic_printk Enables pr_debug()/dev_dbg() calls if
660 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
661 These can also be switched on/off via
662 <debugfs>/dynamic_printk/modules
664 earlycon= [KNL] Output early console device and options.
665 uart[8250],io,<addr>[,options]
666 uart[8250],mmio,<addr>[,options]
667 Start an early, polled-mode console on the 8250/16550
668 UART at the specified I/O port or MMIO address.
669 The options are the same as for ttyS, above.
671 earlyprintk= [X86,SH,BLACKFIN]
672 earlyprintk=vga
673 earlyprintk=serial[,ttySn[,baudrate]]
674 earlyprintk=dbgp[debugController#]
676 Append ",keep" to not disable it when the real console
677 takes over.
679 Only vga or serial or usb debug port at a time.
681 Currently only ttyS0 and ttyS1 are supported.
683 Interaction with the standard serial driver is not
684 very good.
686 The VGA output is eventually overwritten by the real
687 console.
689 eata= [HW,SCSI]
691 edd= [EDD]
692 Format: {"off" | "on" | "skip[mbr]"}
694 eisa_irq_edge= [PARISC,HW]
695 See header of drivers/parisc/eisa.c.
697 elanfreq= [X86-32]
698 See comment before function elanfreq_setup() in
699 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
701 elevator= [IOSCHED]
702 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
703 See Documentation/block/as-iosched.txt and
704 Documentation/block/deadline-iosched.txt for details.
706 elfcorehdr= [IA64,PPC,SH,X86]
707 Specifies physical address of start of kernel core
708 image elf header. Generally kexec loader will
709 pass this option to capture kernel.
710 See Documentation/kdump/kdump.txt for details.
712 enable_mtrr_cleanup [X86]
713 The kernel tries to adjust MTRR layout from continuous
714 to discrete, to make X server driver able to add WB
715 entry later. This parameter enables that.
717 enable_timer_pin_1 [X86]
718 Enable PIN 1 of APIC timer
719 Can be useful to work around chipset bugs
720 (in particular on some ATI chipsets).
721 The kernel tries to set a reasonable default.
723 enforcing [SELINUX] Set initial enforcing status.
724 Format: {"0" | "1"}
725 See security/selinux/Kconfig help text.
726 0 -- permissive (log only, no denials).
727 1 -- enforcing (deny and log).
728 Default value is 0.
729 Value can be changed at runtime via /selinux/enforce.
731 ether= [HW,NET] Ethernet cards parameters
732 This option is obsoleted by the "netdev=" option, which
733 has equivalent usage. See its documentation for details.
735 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
736 Format: <io>[,<irq>]
738 failslab=
739 fail_page_alloc=
740 fail_make_request=[KNL]
741 General fault injection mechanism.
742 Format: <interval>,<probability>,<space>,<times>
743 See also /Documentation/fault-injection/.
745 fd_mcs= [HW,SCSI]
746 See header of drivers/scsi/fd_mcs.c.
748 fdomain= [HW,SCSI]
749 See header of drivers/scsi/fdomain.c.
751 floppy= [HW]
752 See Documentation/blockdev/floppy.txt.
754 force_pal_cache_flush
755 [IA-64] Avoid check_sal_cache_flush which may hang on
756 buggy SAL_CACHE_FLUSH implementations. Using this
757 parameter will force ia64_sal_cache_flush to call
758 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
760 ftrace=[tracer]
761 [FTRACE] will set and start the specified tracer
762 as early as possible in order to facilitate early
763 boot debugging.
765 ftrace_dump_on_oops
766 [FTRACE] will dump the trace buffers on oops.
768 ftrace_filter=[function-list]
769 [FTRACE] Limit the functions traced by the function
770 tracer at boot up. function-list is a comma separated
771 list of functions. This list can be changed at run
772 time by the set_ftrace_filter file in the debugfs
773 tracing directory.
775 ftrace_notrace=[function-list]
776 [FTRACE] Do not trace the functions specified in
777 function-list. This list can be changed at run time
778 by the set_ftrace_notrace file in the debugfs
779 tracing directory.
781 gamecon.map[2|3]=
782 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
783 support via parallel port (up to 5 devices per port)
784 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
785 See also Documentation/input/joystick-parport.txt
787 gamma= [HW,DRM]
789 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
790 Format: off | on
791 default: on
793 gcov_persist= [GCOV] When non-zero (default), profiling data for
794 kernel modules is saved and remains accessible via
795 debugfs, even when the module is unloaded/reloaded.
796 When zero, profiling data is discarded and associated
797 debugfs files are removed at module unload time.
799 gdth= [HW,SCSI]
800 See header of drivers/scsi/gdth.c.
802 gpt [EFI] Forces disk with valid GPT signature but
803 invalid Protective MBR to be treated as GPT.
805 gvp11= [HW,SCSI]
807 hashdist= [KNL,NUMA] Large hashes allocated during boot
808 are distributed across NUMA nodes. Defaults on
809 for 64bit NUMA, off otherwise.
810 Format: 0 | 1 (for off | on)
812 hcl= [IA-64] SGI's Hardware Graph compatibility layer
814 hd= [EIDE] (E)IDE hard drive subsystem geometry
815 Format: <cyl>,<head>,<sect>
817 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
818 size of <nn>. This works even on boxes that have no
819 highmem otherwise. This also works to reduce highmem
820 size on bigger boxes.
822 highres= [KNL] Enable/disable high resolution timer mode.
823 Valid parameters: "on", "off"
824 Default: "on"
826 hisax= [HW,ISDN]
827 See Documentation/isdn/README.HiSax.
829 hlt [BUGS=ARM,SH]
831 hpet= [X86-32,HPET] option to control HPET usage
832 Format: { enable (default) | disable | force |
833 verbose }
834 disable: disable HPET and use PIT instead
835 force: allow force enabled of undocumented chips (ICH4,
836 VIA, nVidia)
837 verbose: show contents of HPET registers during setup
839 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
840 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
841 On x86-64 and powerpc, this option can be specified
842 multiple times interleaved with hugepages= to reserve
843 huge pages of different sizes. Valid pages sizes on
844 x86-64 are 2M (when the CPU supports "pse") and 1G
845 (when the CPU supports the "pdpe1gb" cpuinfo flag)
846 Note that 1GB pages can only be allocated at boot time
847 using hugepages= and not freed afterwards.
849 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
850 terminal devices. Valid values: 0..8
851 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
852 If specified, z/VM IUCV HVC accepts connections
853 from listed z/VM user IDs only.
855 i2c_bus= [HW] Override the default board specific I2C bus speed
856 or register an additional I2C bus that is not
857 registered from board initialization code.
858 Format:
859 <bus_id>,<clkrate>
861 i8042.debug [HW] Toggle i8042 debug mode
862 i8042.direct [HW] Put keyboard port into non-translated mode
863 i8042.dumbkbd [HW] Pretend that controller can only read data from
864 keyboard and cannot control its state
865 (Don't attempt to blink the leds)
866 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
867 i8042.nokbd [HW] Don't check/create keyboard port
868 i8042.noloop [HW] Disable the AUX Loopback command while probing
869 for the AUX port
870 i8042.nomux [HW] Don't check presence of an active multiplexing
871 controller
872 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
873 controllers
874 i8042.panicblink=
875 [HW] Frequency with which keyboard LEDs should blink
876 when kernel panics (default is 0.5 sec)
877 i8042.reset [HW] Reset the controller during init and cleanup
878 i8042.unlock [HW] Unlock (ignore) the keylock
880 i810= [HW,DRM]
882 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
883 indicates that the driver is running on unsupported
884 hardware.
885 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
886 does not match list of supported models.
887 i8k.power_status
888 [HW] Report power status in /proc/i8k
889 (disabled by default)
890 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
891 capability is set.
893 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
894 See Documentation/mca.txt.
896 icn= [HW,ISDN]
897 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
899 ide-core.nodma= [HW] (E)IDE subsystem
900 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
901 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
902 .cdrom .chs .ignore_cable are additional options
903 See Documentation/ide/ide.txt.
905 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
906 Claim all unknown PCI IDE storage controllers.
908 idle= [X86]
909 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
910 Poll forces a polling idle loop that can slightly
911 improve the performance of waking up a idle CPU, but
912 will use a lot of power and make the system run hot.
913 Not recommended.
914 idle=mwait: On systems which support MONITOR/MWAIT but
915 the kernel chose to not use it because it doesn't save
916 as much power as a normal idle loop, use the
917 MONITOR/MWAIT idle loop anyways. Performance should be
918 the same as idle=poll.
919 idle=halt: Halt is forced to be used for CPU idle.
920 In such case C2/C3 won't be used again.
921 idle=nomwait: Disable mwait for CPU C-states
923 ignore_loglevel [KNL]
924 Ignore loglevel setting - this will print /all/
925 kernel messages to the console. Useful for debugging.
927 ihash_entries= [KNL]
928 Set number of hash buckets for inode cache.
930 ima_audit= [IMA]
931 Format: { "0" | "1" }
932 0 -- integrity auditing messages. (Default)
933 1 -- enable informational integrity auditing messages.
935 ima_hash= [IMA]
936 Format: { "sha1" | "md5" }
937 default: "sha1"
939 ima_tcb [IMA]
940 Load a policy which meets the needs of the Trusted
941 Computing Base. This means IMA will measure all
942 programs exec'd, files mmap'd for exec, and all files
943 opened for read by uid=0.
945 in2000= [HW,SCSI]
946 See header of drivers/scsi/in2000.c.
948 init= [KNL]
949 Format: <full_path>
950 Run specified binary instead of /sbin/init as init
951 process.
953 initcall_debug [KNL] Trace initcalls as they are executed. Useful
954 for working out where the kernel is dying during
955 startup.
957 initrd= [BOOT] Specify the location of the initial ramdisk
959 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
960 Format: <irq>
962 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
963 on
964 Enable intel iommu driver.
965 off
966 Disable intel iommu driver.
967 igfx_off [Default Off]
968 By default, gfx is mapped as normal device. If a gfx
969 device has a dedicated DMAR unit, the DMAR unit is
970 bypassed by not enabling DMAR with this option. In
971 this case, gfx device will use physical address for
972 DMA.
973 forcedac [x86_64]
974 With this option iommu will not optimize to look
975 for io virtual address below 32 bit forcing dual
976 address cycle on pci bus for cards supporting greater
977 than 32 bit addressing. The default is to look
978 for translation below 32 bit and if not available
979 then look in the higher range.
980 strict [Default Off]
981 With this option on every unmap_single operation will
982 result in a hardware IOTLB flush operation as opposed
983 to batching them for performance.
985 inttest= [IA64]
987 iomem= Disable strict checking of access to MMIO memory
988 strict regions from userspace.
989 relaxed
991 iommu= [x86]
992 off
993 force
994 noforce
995 biomerge
996 panic
997 nopanic
998 merge
999 nomerge
1000 forcesac
1001 soft
1002 pt [x86, IA64]
1004 io7= [HW] IO7 for Marvel based alpha systems
1005 See comment before marvel_specify_io7 in
1006 arch/alpha/kernel/core_marvel.c.
1008 io_delay= [X86] I/O delay method
1009 0x80
1010 Standard port 0x80 based delay
1011 0xed
1012 Alternate port 0xed based delay (needed on some systems)
1013 udelay
1014 Simple two microseconds delay
1015 none
1016 No delay
1018 ip= [IP_PNP]
1019 See Documentation/filesystems/nfsroot.txt.
1021 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1022 See comment before ip2_setup() in
1023 drivers/char/ip2/ip2base.c.
1025 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1026 See header of drivers/scsi/ips.c.
1028 irqfixup [HW]
1029 When an interrupt is not handled search all handlers
1030 for it. Intended to get systems with badly broken
1031 firmware running.
1033 irqpoll [HW]
1034 When an interrupt is not handled search all handlers
1035 for it. Also check all handlers each timer
1036 interrupt. Intended to get systems with badly broken
1037 firmware running.
1039 isapnp= [ISAPNP]
1040 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1042 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1043 Format:
1044 <cpu number>,...,<cpu number>
1045 or
1046 <cpu number>-<cpu number>
1047 (must be a positive range in ascending order)
1048 or a mixture
1049 <cpu number>,...,<cpu number>-<cpu number>
1051 This option can be used to specify one or more CPUs
1052 to isolate from the general SMP balancing and scheduling
1053 algorithms. You can move a process onto or off an
1054 "isolated" CPU via the CPU affinity syscalls or cpuset.
1055 <cpu number> begins at 0 and the maximum value is
1056 "number of CPUs in system - 1".
1058 This option is the preferred way to isolate CPUs. The
1059 alternative -- manually setting the CPU mask of all
1060 tasks in the system -- can cause problems and
1061 suboptimal load balancer performance.
1063 iucv= [HW,NET]
1065 js= [HW,JOY] Analog joystick
1066 See Documentation/input/joystick.txt.
1068 keepinitrd [HW,ARM]
1070 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1071 specifies the amount of memory usable by the kernel
1072 for non-movable allocations. The requested amount is
1073 spread evenly throughout all nodes in the system. The
1074 remaining memory in each node is used for Movable
1075 pages. In the event, a node is too small to have both
1076 kernelcore and Movable pages, kernelcore pages will
1077 take priority and other nodes will have a larger number
1078 of kernelcore pages. The Movable zone is used for the
1079 allocation of pages that may be reclaimed or moved
1080 by the page migration subsystem. This means that
1081 HugeTLB pages may not be allocated from this zone.
1082 Note that allocations like PTEs-from-HighMem still
1083 use the HighMem zone if it exists, and the Normal
1084 zone if it does not.
1086 kgdboc= [HW] kgdb over consoles.
1087 Requires a tty driver that supports console polling.
1088 (only serial supported for now)
1089 Format: <serial_device>[,baud]
1091 kmac= [MIPS] korina ethernet MAC address.
1092 Configure the RouterBoard 532 series on-chip
1093 Ethernet adapter MAC address.
1095 kmemleak= [KNL] Boot-time kmemleak enable/disable
1096 Valid arguments: on, off
1097 Default: on
1099 kstack=N [X86] Print N words from the kernel stack
1100 in oops dumps.
1102 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1103 Default is 0 (don't ignore, but inject #GP)
1105 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1106 Default is 1 (enabled)
1108 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1109 Default is 0 (off)
1111 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1112 for all guests.
1113 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1115 kvm-intel.bypass_guest_pf=
1116 [KVM,Intel] Disables bypassing of guest page faults
1117 on Intel chips. Default is 1 (enabled)
1119 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1120 (virtualized MMU) support on capable Intel chips.
1121 Default is 1 (enabled)
1123 kvm-intel.emulate_invalid_guest_state=
1124 [KVM,Intel] Enable emulation of invalid guest states
1125 Default is 0 (disabled)
1127 kvm-intel.flexpriority=
1128 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1129 Default is 1 (enabled)
1131 kvm-intel.unrestricted_guest=
1132 [KVM,Intel] Disable unrestricted guest feature
1133 (virtualized real and unpaged mode) on capable
1134 Intel chips. Default is 1 (enabled)
1136 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1137 feature (tagged TLBs) on capable Intel chips.
1138 Default is 1 (enabled)
1140 l2cr= [PPC]
1142 l3cr= [PPC]
1144 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1145 disabled it.
1147 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1148 in C2 power state.
1150 libata.dma= [LIBATA] DMA control
1151 libata.dma=0 Disable all PATA and SATA DMA
1152 libata.dma=1 PATA and SATA Disk DMA only
1153 libata.dma=2 ATAPI (CDROM) DMA only
1154 libata.dma=4 Compact Flash DMA only
1155 Combinations also work, so libata.dma=3 enables DMA
1156 for disks and CDROMs, but not CFs.
1158 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1159 libata.ignore_hpa=0 keep BIOS limits (default)
1160 libata.ignore_hpa=1 ignore limits, using full disk
1162 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1163 when set.
1164 Format: <int>
1166 libata.force= [LIBATA] Force configurations. The format is comma
1167 separated list of "[ID:]VAL" where ID is
1168 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1169 matching port, link or device. Basically, it matches
1170 the ATA ID string printed on console by libata. If
1171 the whole ID part is omitted, the last PORT and DEVICE
1172 values are used. If ID hasn't been specified yet, the
1173 configuration applies to all ports, links and devices.
1175 If only DEVICE is omitted, the parameter applies to
1176 the port and all links and devices behind it. DEVICE
1177 number of 0 either selects the first device or the
1178 first fan-out link behind PMP device. It does not
1179 select the host link. DEVICE number of 15 selects the
1180 host link and device attached to it.
1182 The VAL specifies the configuration to force. As long
1183 as there's no ambiguity shortcut notation is allowed.
1184 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1185 The following configurations can be forced.
1187 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1188 Any ID with matching PORT is used.
1190 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1192 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1193 udma[/][16,25,33,44,66,100,133] notation is also
1194 allowed.
1196 * [no]ncq: Turn on or off NCQ.
1198 * nohrst, nosrst, norst: suppress hard, soft
1199 and both resets.
1201 If there are multiple matching configurations changing
1202 the same attribute, the last one is used.
1204 lmb=debug [KNL] Enable lmb debug messages.
1206 load_ramdisk= [RAM] List of ramdisks to load from floppy
1207 See Documentation/blockdev/ramdisk.txt.
1209 lockd.nlm_grace_period=P [NFS] Assign grace period.
1210 Format: <integer>
1212 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1213 Format: <integer>
1215 lockd.nlm_timeout=T [NFS] Assign timeout value.
1216 Format: <integer>
1218 lockd.nlm_udpport=M [NFS] Assign UDP port.
1219 Format: <integer>
1221 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1222 Format: <irq>
1224 loglevel= All Kernel Messages with a loglevel smaller than the
1225 console loglevel will be printed to the console. It can
1226 also be changed with klogd or other programs. The
1227 loglevels are defined as follows:
1229 0 (KERN_EMERG) system is unusable
1230 1 (KERN_ALERT) action must be taken immediately
1231 2 (KERN_CRIT) critical conditions
1232 3 (KERN_ERR) error conditions
1233 4 (KERN_WARNING) warning conditions
1234 5 (KERN_NOTICE) normal but significant condition
1235 6 (KERN_INFO) informational
1236 7 (KERN_DEBUG) debug-level messages
1238 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1239 Format: { n | nk | nM }
1240 n must be a power of two. The default size
1241 is set in the kernel config file.
1243 logo.nologo [FB] Disables display of the built-in Linux logo.
1244 This may be used to provide more screen space for
1245 kernel log messages and is useful when debugging
1246 kernel boot problems.
1248 lp=0 [LP] Specify parallel ports to use, e.g,
1249 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1250 lp=reset first parallel port). 'lp=0' disables the
1251 lp=auto printer driver. 'lp=reset' (which can be
1252 specified in addition to the ports) causes
1253 attached printers to be reset. Using
1254 lp=port1,port2,... specifies the parallel ports
1255 to associate lp devices with, starting with
1256 lp0. A port specification may be 'none' to skip
1257 that lp device, or a parport name such as
1258 'parport0'. Specifying 'lp=auto' instead of a
1259 port specification list means that device IDs
1260 from each port should be examined, to see if
1261 an IEEE 1284-compliant printer is attached; if
1262 so, the driver will manage that printer.
1263 See also header of drivers/char/lp.c.
1265 lpj=n [KNL]
1266 Sets loops_per_jiffy to given constant, thus avoiding
1267 time-consuming boot-time autodetection (up to 250 ms per
1268 CPU). 0 enables autodetection (default). To determine
1269 the correct value for your kernel, boot with normal
1270 autodetection and see what value is printed. Note that
1271 on SMP systems the preset will be applied to all CPUs,
1272 which is likely to cause problems if your CPUs need
1273 significantly divergent settings. An incorrect value
1274 will cause delays in the kernel to be wrong, leading to
1275 unpredictable I/O errors and other breakage. Although
1276 unlikely, in the extreme case this might damage your
1277 hardware.
1279 ltpc= [NET]
1280 Format: <io>,<irq>,<dma>
1282 mac5380= [HW,SCSI] Format:
1283 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1285 machvec= [IA64] Force the use of a particular machine-vector
1286 (machvec) in a generic kernel.
1287 Example: machvec=hpzx1_swiotlb
1289 machtype= [Loongson] Share the same kernel image file between different
1290 yeeloong laptop.
1291 Example: machtype=lemote-yeeloong-2f-7inch
1293 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1294 than or equal to this physical address is ignored.
1296 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1297 should make use of. maxcpus=n : n >= 0 limits the
1298 kernel to using 'n' processors. n=0 is a special case,
1299 it is equivalent to "nosmp", which also disables
1300 the IO APIC.
1302 max_loop= [LOOP] Maximum number of loopback devices that can
1303 be mounted
1304 Format: <1-256>
1306 max_luns= [SCSI] Maximum number of LUNs to probe.
1307 Should be between 1 and 2^32-1.
1309 max_report_luns=
1310 [SCSI] Maximum number of LUNs received.
1311 Should be between 1 and 16384.
1313 mcatest= [IA-64]
1315 mce [X86-32] Machine Check Exception
1317 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1319 md= [HW] RAID subsystems devices and level
1320 See Documentation/md.txt.
1322 mdacon= [MDA]
1323 Format: <first>,<last>
1324 Specifies range of consoles to be captured by the MDA.
1326 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1327 Amount of memory to be used when the kernel is not able
1328 to see the whole system memory or for test.
1329 [X86-32] Use together with memmap= to avoid physical
1330 address space collisions. Without memmap= PCI devices
1331 could be placed at addresses belonging to unused RAM.
1333 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1334 memory.
1336 memchunk=nn[KMG]
1337 [KNL,SH] Allow user to override the default size for
1338 per-device physically contiguous DMA buffers.
1340 memmap=exactmap [KNL,X86] Enable setting of an exact
1341 E820 memory map, as specified by the user.
1342 Such memmap=exactmap lines can be constructed based on
1343 BIOS output or other requirements. See the memmap=nn@ss
1344 option description.
1346 memmap=nn[KMG]@ss[KMG]
1347 [KNL] Force usage of a specific region of memory
1348 Region of memory to be used, from ss to ss+nn.
1350 memmap=nn[KMG]#ss[KMG]
1351 [KNL,ACPI] Mark specific memory as ACPI data.
1352 Region of memory to be used, from ss to ss+nn.
1354 memmap=nn[KMG]$ss[KMG]
1355 [KNL,ACPI] Mark specific memory as reserved.
1356 Region of memory to be used, from ss to ss+nn.
1357 Example: Exclude memory from 0x18690000-0x1869ffff
1358 memmap=64K$0x18690000
1359 or
1360 memmap=0x10000$0x18690000
1362 memory_corruption_check=0/1 [X86]
1363 Some BIOSes seem to corrupt the first 64k of
1364 memory when doing things like suspend/resume.
1365 Setting this option will scan the memory
1366 looking for corruption. Enabling this will
1367 both detect corruption and prevent the kernel
1368 from using the memory being corrupted.
1369 However, its intended as a diagnostic tool; if
1370 repeatable BIOS-originated corruption always
1371 affects the same memory, you can use memmap=
1372 to prevent the kernel from using that memory.
1374 memory_corruption_check_size=size [X86]
1375 By default it checks for corruption in the low
1376 64k, making this memory unavailable for normal
1377 use. Use this parameter to scan for
1378 corruption in more or less memory.
1380 memory_corruption_check_period=seconds [X86]
1381 By default it checks for corruption every 60
1382 seconds. Use this parameter to check at some
1383 other rate. 0 disables periodic checking.
1385 memtest= [KNL,X86] Enable memtest
1386 Format: <integer>
1387 default : 0 <disable>
1388 Specifies the number of memtest passes to be
1389 performed. Each pass selects another test
1390 pattern from a given set of patterns. Memtest
1391 fills the memory with this pattern, validates
1392 memory contents and reserves bad memory
1393 regions that are detected.
1395 meye.*= [HW] Set MotionEye Camera parameters
1396 See Documentation/video4linux/meye.txt.
1398 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1399 Multi-Function General Purpose Timers on AMD Geode
1400 platforms.
1402 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1403 the BIOS has incorrectly applied a workaround. TinyBIOS
1404 version 0.98 is known to be affected, 0.99 fixes the
1405 problem by letting the user disable the workaround.
1407 mga= [HW,DRM]
1409 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1410 physical address is ignored.
1412 mini2440= [ARM,HW,KNL]
1413 Format:[0..2][b][c][t]
1414 Default: "0tb"
1415 MINI2440 configuration specification:
1416 0 - The attached screen is the 3.5" TFT
1417 1 - The attached screen is the 7" TFT
1418 2 - The VGA Shield is attached (1024x768)
1419 Leaving out the screen size parameter will not load
1420 the TFT driver, and the framebuffer will be left
1421 unconfigured.
1422 b - Enable backlight. The TFT backlight pin will be
1423 linked to the kernel VESA blanking code and a GPIO
1424 LED. This parameter is not necessary when using the
1425 VGA shield.
1426 c - Enable the s3c camera interface.
1427 t - Reserved for enabling touchscreen support. The
1428 touchscreen support is not enabled in the mainstream
1429 kernel as of 2.6.30, a preliminary port can be found
1430 in the "bleeding edge" mini2440 support kernel at
1431 http://repo.or.cz/w/linux-2.6/mini2440.git
1433 mminit_loglevel=
1434 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1435 parameter allows control of the logging verbosity for
1436 the additional memory initialisation checks. A value
1437 of 0 disables mminit logging and a level of 4 will
1438 log everything. Information is printed at KERN_DEBUG
1439 so loglevel=8 may also need to be specified.
1441 mousedev.tap_time=
1442 [MOUSE] Maximum time between finger touching and
1443 leaving touchpad surface for touch to be considered
1444 a tap and be reported as a left button click (for
1445 touchpads working in absolute mode only).
1446 Format: <msecs>
1447 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1448 reporting absolute coordinates, such as tablets
1449 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1450 reporting absolute coordinates, such as tablets
1452 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1453 is similar to kernelcore except it specifies the
1454 amount of memory used for migratable allocations.
1455 If both kernelcore and movablecore is specified,
1456 then kernelcore will be at *least* the specified
1457 value but may be more. If movablecore on its own
1458 is specified, the administrator must be careful
1459 that the amount of memory usable for all allocations
1460 is not too small.
1462 mpu401= [HW,OSS]
1463 Format: <io>,<irq>
1465 MTD_Partition= [MTD]
1466 Format: <name>,<region-number>,<size>,<offset>
1468 MTD_Region= [MTD] Format:
1469 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1471 mtdparts= [MTD]
1472 See drivers/mtd/cmdlinepart.c.
1474 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1476 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1478 boundary - index of last SLC block on Flex-OneNAND.
1479 The remaining blocks are configured as MLC blocks.
1480 lock - Configure if Flex-OneNAND boundary should be locked.
1481 Once locked, the boundary cannot be changed.
1482 1 indicates lock status, 0 indicates unlock status.
1484 mtdset= [ARM]
1485 ARM/S3C2412 JIVE boot control
1487 See arch/arm/mach-s3c2412/mach-jive.c
1489 mtouchusb.raw_coordinates=
1490 [HW] Make the MicroTouch USB driver use raw coordinates
1491 ('y', default) or cooked coordinates ('n')
1493 mtrr_chunk_size=nn[KMG] [X86]
1494 used for mtrr cleanup. It is largest continuous chunk
1495 that could hold holes aka. UC entries.
1497 mtrr_gran_size=nn[KMG] [X86]
1498 Used for mtrr cleanup. It is granularity of mtrr block.
1499 Default is 1.
1500 Large value could prevent small alignment from
1501 using up MTRRs.
1503 mtrr_spare_reg_nr=n [X86]
1504 Format: <integer>
1505 Range: 0,7 : spare reg number
1506 Default : 1
1507 Used for mtrr cleanup. It is spare mtrr entries number.
1508 Set to 2 or more if your graphical card needs more.
1510 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1512 NCR_D700= [HW,SCSI]
1513 See header of drivers/scsi/NCR_D700.c.
1515 ncr5380= [HW,SCSI]
1517 ncr53c400= [HW,SCSI]
1519 ncr53c400a= [HW,SCSI]
1521 ncr53c406a= [HW,SCSI]
1523 ncr53c8xx= [HW,SCSI]
1525 netdev= [NET] Network devices parameters
1526 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1527 Note that mem_start is often overloaded to mean
1528 something different and driver-specific.
1529 This usage is only documented in each driver source
1530 file if at all.
1532 nf_conntrack.acct=
1533 [NETFILTER] Enable connection tracking flow accounting
1534 0 to disable accounting
1535 1 to enable accounting
1536 Default value depends on CONFIG_NF_CT_ACCT that is
1537 going to be removed in 2.6.29.
1539 nfsaddrs= [NFS]
1540 See Documentation/filesystems/nfsroot.txt.
1542 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1543 See Documentation/filesystems/nfsroot.txt.
1545 nfs.callback_tcpport=
1546 [NFS] set the TCP port on which the NFSv4 callback
1547 channel should listen.
1549 nfs.cache_getent=
1550 [NFS] sets the pathname to the program which is used
1551 to update the NFS client cache entries.
1553 nfs.cache_getent_timeout=
1554 [NFS] sets the timeout after which an attempt to
1555 update a cache entry is deemed to have failed.
1557 nfs.idmap_cache_timeout=
1558 [NFS] set the maximum lifetime for idmapper cache
1559 entries.
1561 nfs.enable_ino64=
1562 [NFS] enable 64-bit inode numbers.
1563 If zero, the NFS client will fake up a 32-bit inode
1564 number for the readdir() and stat() syscalls instead
1565 of returning the full 64-bit number.
1566 The default is to return 64-bit inode numbers.
1568 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1569 when a NMI is triggered.
1570 Format: [state][,regs][,debounce][,die]
1572 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1573 Format: [panic,][num]
1574 Valid num: 0,1,2
1575 0 - turn nmi_watchdog off
1576 1 - use the IO-APIC timer for the NMI watchdog
1577 2 - use the local APIC for the NMI watchdog using
1578 a performance counter. Note: This will use one
1579 performance counter and the local APIC's performance
1580 vector.
1581 When panic is specified, panic when an NMI watchdog
1582 timeout occurs.
1583 This is useful when you use a panic=... timeout and
1584 need the box quickly up again.
1585 Instead of 1 and 2 it is possible to use the following
1586 symbolic names: lapic and ioapic
1587 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1589 netpoll.carrier_timeout=
1590 [NET] Specifies amount of time (in seconds) that
1591 netpoll should wait for a carrier. By default netpoll
1592 waits 4 seconds.
1594 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1595 emulation library even if a 387 maths coprocessor
1596 is present.
1598 no_console_suspend
1599 [HW] Never suspend the console
1600 Disable suspending of consoles during suspend and
1601 hibernate operations. Once disabled, debugging
1602 messages can reach various consoles while the rest
1603 of the system is being put to sleep (ie, while
1604 debugging driver suspend/resume hooks). This may
1605 not work reliably with all consoles, but is known
1606 to work with serial and VGA consoles.
1608 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1609 caches in the slab allocator. Saves per-node memory,
1610 but will impact performance.
1612 noalign [KNL,ARM]
1614 noapic [SMP,APIC] Tells the kernel to not make use of any
1615 IOAPICs that may be present in the system.
1617 nobats [PPC] Do not use BATs for mapping kernel lowmem
1618 on "Classic" PPC cores.
1620 nocache [ARM]
1622 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1624 nodelayacct [KNL] Disable per-task delay accounting
1626 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1628 nodsp [SH] Disable hardware DSP at boot time.
1630 noefi [X86] Disable EFI runtime services support.
1632 noexec [IA-64]
1634 noexec [X86]
1635 On X86-32 available only on PAE configured kernels.
1636 noexec=on: enable non-executable mappings (default)
1637 noexec=off: disable non-executable mappings
1639 noexec32 [X86-64]
1640 This affects only 32-bit executables.
1641 noexec32=on: enable non-executable mappings (default)
1642 read doesn't imply executable mappings
1643 noexec32=off: disable non-executable mappings
1644 read implies executable mappings
1646 nofpu [SH] Disable hardware FPU at boot time.
1648 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1649 register save and restore. The kernel will only save
1650 legacy floating-point registers on task switch.
1652 noxsave [BUGS=X86] Disables x86 extended register state save
1653 and restore using xsave. The kernel will fallback to
1654 enabling legacy floating-point and sse state.
1656 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1657 wfi(ARM) instruction doesn't work correctly and not to
1658 use it. This is also useful when using JTAG debugger.
1660 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1661 instruction doesn't work correctly and not to
1662 use it.
1664 no_file_caps Tells the kernel not to honor file capabilities. The
1665 only way then for a file to be executed with privilege
1666 is to be setuid root or executed by root.
1668 nohalt [IA-64] Tells the kernel not to use the power saving
1669 function PAL_HALT_LIGHT when idle. This increases
1670 power-consumption. On the positive side, it reduces
1671 interrupt wake-up latency, which may improve performance
1672 in certain environments such as networked servers or
1673 real-time systems.
1675 nohz= [KNL] Boottime enable/disable dynamic ticks
1676 Valid arguments: on, off
1677 Default: on
1679 noiotrap [SH] Disables trapped I/O port accesses.
1681 noirqdebug [X86-32] Disables the code which attempts to detect and
1682 disable unhandled interrupt sources.
1684 no_timer_check [X86,APIC] Disables the code which tests for
1685 broken timer IRQ sources.
1687 noisapnp [ISAPNP] Disables ISA PnP code.
1689 noinitrd [RAM] Tells the kernel not to load any configured
1690 initial RAM disk.
1692 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1693 remapping.
1695 nointroute [IA-64]
1697 nojitter [IA64] Disables jitter checking for ITC timers.
1699 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1701 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1703 noltlbs [PPC] Do not use large page/tlb entries for kernel
1704 lowmem mapping on PPC40x.
1706 nomca [IA-64] Disable machine check abort handling
1708 nomce [X86-32] Machine Check Exception
1710 nomfgpt [X86-32] Disable Multi-Function General Purpose
1711 Timer usage (for AMD Geode machines).
1713 norandmaps Don't use address space randomization. Equivalent to
1714 echo 0 > /proc/sys/kernel/randomize_va_space
1716 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1718 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1719 with UP alternatives
1721 noresidual [PPC] Don't use residual data on PReP machines.
1723 noresume [SWSUSP] Disables resume and restores original swap
1724 space.
1726 no-scroll [VGA] Disables scrollback.
1727 This is required for the Braillex ib80-piezo Braille
1728 reader made by F.H. Papenmeier (Germany).
1730 nosbagart [IA-64]
1732 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1734 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1735 and disable the IO APIC. legacy for "maxcpus=0".
1737 nosoftlockup [KNL] Disable the soft-lockup detector.
1739 noswapaccount [KNL] Disable accounting of swap in memory resource
1740 controller. (See Documentation/cgroups/memory.txt)
1742 nosync [HW,M68K] Disables sync negotiation for all devices.
1744 notsc [BUGS=X86-32] Disable Time Stamp Counter
1746 nousb [USB] Disable the USB subsystem
1748 nowb [ARM]
1750 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1752 nptcg= [IA64] Override max number of concurrent global TLB
1753 purges which is reported from either PAL_VM_SUMMARY or
1754 SAL PALO.
1756 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1758 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1759 one of ['zone', 'node', 'default'] can be specified
1760 This can be set from sysctl after boot.
1761 See Documentation/sysctl/vm.txt for details.
1763 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1764 See Documentation/debugging-via-ohci1394.txt for more
1765 info.
1767 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1768 Rather than timing out after 20 ms if an EC
1769 command is not properly ACKed, override the length
1770 of the timeout. We have interrupts disabled while
1771 waiting for the ACK, so if this is set too high
1772 interrupts *may* be lost!
1774 opl3= [HW,OSS]
1775 Format: <io>
1777 oprofile.timer= [HW]
1778 Use timer interrupt instead of performance counters
1780 oprofile.cpu_type= Force an oprofile cpu type
1781 This might be useful if you have an older oprofile
1782 userland or if you want common events.
1783 Format: { arch_perfmon }
1784 arch_perfmon: [X86] Force use of architectural
1785 perfmon on Intel CPUs instead of the
1786 CPU specific event set.
1788 osst= [HW,SCSI] SCSI Tape Driver
1789 Format: <buffer_size>,<write_threshold>
1790 See also Documentation/scsi/st.txt.
1792 panic= [KNL] Kernel behaviour on panic
1793 Format: <timeout>
1795 parkbd.port= [HW] Parallel port number the keyboard adapter is
1796 connected to, default is 0.
1797 Format: <parport#>
1798 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1799 0 for XT, 1 for AT (default is AT).
1800 Format: <mode>
1802 parport= [HW,PPT] Specify parallel ports. 0 disables.
1803 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1804 Use 'auto' to force the driver to use any
1805 IRQ/DMA settings detected (the default is to
1806 ignore detected IRQ/DMA settings because of
1807 possible conflicts). You can specify the base
1808 address, IRQ, and DMA settings; IRQ and DMA
1809 should be numbers, or 'auto' (for using detected
1810 settings on that particular port), or 'nofifo'
1811 (to avoid using a FIFO even if it is detected).
1812 Parallel ports are assigned in the order they
1813 are specified on the command line, starting
1814 with parport0.
1816 parport_init_mode= [HW,PPT]
1817 Configure VIA parallel port to operate in
1818 a specific mode. This is necessary on Pegasos
1819 computer where firmware has no options for setting
1820 up parallel port mode and sets it to spp.
1821 Currently this function knows 686a and 8231 chips.
1822 Format: [spp|ps2|epp|ecp|ecpepp]
1824 pas2= [HW,OSS] Format:
1825 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1827 pas16= [HW,SCSI]
1828 See header of drivers/scsi/pas16.c.
1830 pause_on_oops=
1831 Halt all CPUs after the first oops has been printed for
1832 the specified number of seconds. This is to be used if
1833 your oopses keep scrolling off the screen.
1835 pcbit= [HW,ISDN]
1837 pcd. [PARIDE]
1838 See header of drivers/block/paride/pcd.c.
1839 See also Documentation/blockdev/paride.txt.
1841 pci=option[,option...] [PCI] various PCI subsystem options:
1842 earlydump [X86] dump PCI config space before the kernel
1843 changes anything
1844 off [X86] don't probe for the PCI bus
1845 bios [X86-32] force use of PCI BIOS, don't access
1846 the hardware directly. Use this if your machine
1847 has a non-standard PCI host bridge.
1848 nobios [X86-32] disallow use of PCI BIOS, only direct
1849 hardware access methods are allowed. Use this
1850 if you experience crashes upon bootup and you
1851 suspect they are caused by the BIOS.
1852 conf1 [X86] Force use of PCI Configuration
1853 Mechanism 1.
1854 conf2 [X86] Force use of PCI Configuration
1855 Mechanism 2.
1856 noaer [PCIE] If the PCIEAER kernel config parameter is
1857 enabled, this kernel boot option can be used to
1858 disable the use of PCIE advanced error reporting.
1859 nodomains [PCI] Disable support for multiple PCI
1860 root domains (aka PCI segments, in ACPI-speak).
1861 nommconf [X86] Disable use of MMCONFIG for PCI
1862 Configuration
1863 check_enable_amd_mmconf [X86] check for and enable
1864 properly configured MMIO access to PCI
1865 config space on AMD family 10h CPU
1866 nomsi [MSI] If the PCI_MSI kernel config parameter is
1867 enabled, this kernel boot option can be used to
1868 disable the use of MSI interrupts system-wide.
1869 noioapicquirk [APIC] Disable all boot interrupt quirks.
1870 Safety option to keep boot IRQs enabled. This
1871 should never be necessary.
1872 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1873 primary IO-APIC for bridges that cannot disable
1874 boot IRQs. This fixes a source of spurious IRQs
1875 when the system masks IRQs.
1876 noioapicreroute [APIC] Disable workaround that uses the
1877 boot IRQ equivalent of an IRQ that connects to
1878 a chipset where boot IRQs cannot be disabled.
1879 The opposite of ioapicreroute.
1880 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1881 routing table. These calls are known to be buggy
1882 on several machines and they hang the machine
1883 when used, but on other computers it's the only
1884 way to get the interrupt routing table. Try
1885 this option if the kernel is unable to allocate
1886 IRQs or discover secondary PCI buses on your
1887 motherboard.
1888 rom [X86] Assign address space to expansion ROMs.
1889 Use with caution as certain devices share
1890 address decoders between ROMs and other
1891 resources.
1892 norom [X86] Do not assign address space to
1893 expansion ROMs that do not already have
1894 BIOS assigned address ranges.
1895 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1896 assigned automatically to PCI devices. You can
1897 make the kernel exclude IRQs of your ISA cards
1898 this way.
1899 pirqaddr=0xAAAAA [X86] Specify the physical address
1900 of the PIRQ table (normally generated
1901 by the BIOS) if it is outside the
1902 F0000h-100000h range.
1903 lastbus=N [X86] Scan all buses thru bus #N. Can be
1904 useful if the kernel is unable to find your
1905 secondary buses and you want to tell it
1906 explicitly which ones they are.
1907 assign-busses [X86] Always assign all PCI bus
1908 numbers ourselves, overriding
1909 whatever the firmware may have done.
1910 usepirqmask [X86] Honor the possible IRQ mask stored
1911 in the BIOS $PIR table. This is needed on
1912 some systems with broken BIOSes, notably
1913 some HP Pavilion N5400 and Omnibook XE3
1914 notebooks. This will have no effect if ACPI
1915 IRQ routing is enabled.
1916 noacpi [X86] Do not use ACPI for IRQ routing
1917 or for PCI scanning.
1918 use_crs [X86] Use _CRS for PCI resource
1919 allocation.
1920 routeirq Do IRQ routing for all PCI devices.
1921 This is normally done in pci_enable_device(),
1922 so this option is a temporary workaround
1923 for broken drivers that don't call it.
1924 skip_isa_align [X86] do not align io start addr, so can
1925 handle more pci cards
1926 firmware [ARM] Do not re-enumerate the bus but instead
1927 just use the configuration from the
1928 bootloader. This is currently used on
1929 IXP2000 systems where the bus has to be
1930 configured a certain way for adjunct CPUs.
1931 noearly [X86] Don't do any early type 1 scanning.
1932 This might help on some broken boards which
1933 machine check when some devices' config space
1934 is read. But various workarounds are disabled
1935 and some IOMMU drivers will not work.
1936 bfsort Sort PCI devices into breadth-first order.
1937 This sorting is done to get a device
1938 order compatible with older (<= 2.4) kernels.
1939 nobfsort Don't sort PCI devices into breadth-first order.
1940 cbiosize=nn[KMG] The fixed amount of bus space which is
1941 reserved for the CardBus bridge's IO window.
1942 The default value is 256 bytes.
1943 cbmemsize=nn[KMG] The fixed amount of bus space which is
1944 reserved for the CardBus bridge's memory
1945 window. The default value is 64 megabytes.
1946 resource_alignment=
1947 Format:
1948 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1949 Specifies alignment and device to reassign
1950 aligned memory resources.
1951 If <order of align> is not specified,
1952 PAGE_SIZE is used as alignment.
1953 PCI-PCI bridge can be specified, if resource
1954 windows need to be expanded.
1955 ecrc= Enable/disable PCIe ECRC (transaction layer
1956 end-to-end CRC checking).
1957 bios: Use BIOS/firmware settings. This is the
1958 the default.
1959 off: Turn ECRC off
1960 on: Turn ECRC on.
1962 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1963 Management.
1964 off Disable ASPM.
1965 force Enable ASPM even on devices that claim not to support it.
1966 WARNING: Forcing ASPM on may cause system lockups.
1968 pcmv= [HW,PCMCIA] BadgePAD 4
1970 pd. [PARIDE]
1971 See Documentation/blockdev/paride.txt.
1973 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1974 boot time.
1975 Format: { 0 | 1 }
1976 See arch/parisc/kernel/pdc_chassis.c
1978 percpu_alloc= Select which percpu first chunk allocator to use.
1979 Currently supported values are "embed" and "page".
1980 Archs may support subset or none of the selections.
1981 See comments in mm/percpu.c for details on each
1982 allocator. This parameter is primarily for debugging
1983 and performance comparison.
1985 pf. [PARIDE]
1986 See Documentation/blockdev/paride.txt.
1988 pg. [PARIDE]
1989 See Documentation/blockdev/paride.txt.
1991 pirq= [SMP,APIC] Manual mp-table setup
1992 See Documentation/x86/i386/IO-APIC.txt.
1994 plip= [PPT,NET] Parallel port network link
1995 Format: { parport<nr> | timid | 0 }
1996 See also Documentation/parport.txt.
1998 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1999 Override pmtimer IOPort with a hex value.
2000 e.g. pmtmr=0x508
2002 pnp.debug [PNP]
2003 Enable PNP debug messages. This depends on the
2004 CONFIG_PNP_DEBUG_MESSAGES option.
2006 pnpacpi= [ACPI]
2007 { off }
2009 pnpbios= [ISAPNP]
2010 { on | off | curr | res | no-curr | no-res }
2012 pnp_reserve_irq=
2013 [ISAPNP] Exclude IRQs for the autoconfiguration
2015 pnp_reserve_dma=
2016 [ISAPNP] Exclude DMAs for the autoconfiguration
2018 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2019 Ranges are in pairs (I/O port base and size).
2021 pnp_reserve_mem=
2022 [ISAPNP] Exclude memory regions for the
2023 autoconfiguration.
2024 Ranges are in pairs (memory base and size).
2026 ports= [IP_VS_FTP] IPVS ftp helper module
2027 Default is 21.
2028 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2029 may be specified.
2030 Format: <port>,<port>....
2032 print-fatal-signals=
2033 [KNL] debug: print fatal signals
2034 print-fatal-signals=1: print segfault info to
2035 the kernel console.
2036 default: off.
2038 printk.time= Show timing data prefixed to each printk message line
2039 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2041 processor.max_cstate= [HW,ACPI]
2042 Limit processor to maximum C-state
2043 max_cstate=9 overrides any DMI blacklist limit.
2045 processor.nocst [HW,ACPI]
2046 Ignore the _CST method to determine C-states,
2047 instead using the legacy FADT method
2049 profile= [KNL] Enable kernel profiling via /proc/profile
2050 Format: [schedule,]<number>
2051 Param: "schedule" - profile schedule points.
2052 Param: <number> - step/bucket size as a power of 2 for
2053 statistical time based profiling.
2054 Param: "sleep" - profile D-state sleeping (millisecs).
2055 Requires CONFIG_SCHEDSTATS
2056 Param: "kvm" - profile VM exits.
2058 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2059 before loading.
2060 See Documentation/blockdev/ramdisk.txt.
2062 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2063 probe for; one of (bare|imps|exps|lifebook|any).
2064 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2065 per second.
2066 psmouse.resetafter= [HW,MOUSE]
2067 Try to reset the device after so many bad packets
2068 (0 = never).
2069 psmouse.resolution=
2070 [HW,MOUSE] Set desired mouse resolution, in dpi.
2071 psmouse.smartscroll=
2072 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2073 0 = disabled, 1 = enabled (default).
2075 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2076 Format:
2077 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2079 pt. [PARIDE]
2080 See Documentation/blockdev/paride.txt.
2082 pty.legacy_count=
2083 [KNL] Number of legacy pty's. Overwrites compiled-in
2084 default number.
2086 quiet [KNL] Disable most log messages
2088 r128= [HW,DRM]
2090 raid= [HW,RAID]
2091 See Documentation/md.txt.
2093 ramdisk_blocksize= [RAM]
2094 See Documentation/blockdev/ramdisk.txt.
2096 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2097 See Documentation/blockdev/ramdisk.txt.
2099 rcupdate.blimit= [KNL,BOOT]
2100 Set maximum number of finished RCU callbacks to process
2101 in one batch.
2103 rcupdate.qhimark= [KNL,BOOT]
2104 Set threshold of queued
2105 RCU callbacks over which batch limiting is disabled.
2107 rcupdate.qlowmark= [KNL,BOOT]
2108 Set threshold of queued RCU callbacks below which
2109 batch limiting is re-enabled.
2111 rdinit= [KNL]
2112 Format: <full_path>
2113 Run specified binary instead of /init from the ramdisk,
2114 used for early userspace startup. See initrd.
2116 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2117 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2118 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2120 relax_domain_level=
2121 [KNL, SMP] Set scheduler's default relax_domain_level.
2122 See Documentation/cgroups/cpusets.txt.
2124 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2126 reservetop= [X86-32]
2127 Format: nn[KMG]
2128 Reserves a hole at the top of the kernel virtual
2129 address space.
2131 reset_devices [KNL] Force drivers to reset the underlying device
2132 during initialization.
2134 resume= [SWSUSP]
2135 Specify the partition device for software suspend
2137 resume_offset= [SWSUSP]
2138 Specify the offset from the beginning of the partition
2139 given by "resume=" at which the swap header is located,
2140 in <PAGE_SIZE> units (needed only for swap files).
2141 See Documentation/power/swsusp-and-swap-files.txt
2143 retain_initrd [RAM] Keep initrd memory after extraction
2145 rhash_entries= [KNL,NET]
2146 Set number of hash buckets for route cache
2148 riscom8= [HW,SERIAL]
2149 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2151 ro [KNL] Mount root device read-only on boot
2153 root= [KNL] Root filesystem
2155 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2156 mount the root filesystem
2158 rootflags= [KNL] Set root filesystem mount option string
2160 rootfstype= [KNL] Set root filesystem type
2162 rootwait [KNL] Wait (indefinitely) for root device to show up.
2163 Useful for devices that are detected asynchronously
2164 (e.g. USB and MMC devices).
2166 root_plug.vendor_id=
2167 [ROOTPLUG] Override the default vendor ID
2169 root_plug.product_id=
2170 [ROOTPLUG] Override the default product ID
2172 root_plug.debug=
2173 [ROOTPLUG] Enable debugging output
2175 rw [KNL] Mount root device read-write on boot
2177 S [KNL] Run init in single mode
2179 sa1100ir [NET]
2180 See drivers/net/irda/sa1100_ir.c.
2182 sbni= [NET] Granch SBNI12 leased line adapter
2184 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2185 Format: <io>[,<timeout>[,<isapnp>]]
2187 scsi_debug_*= [SCSI]
2188 See drivers/scsi/scsi_debug.c.
2190 scsi_default_dev_flags=
2191 [SCSI] SCSI default device flags
2192 Format: <integer>
2194 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2195 Format: <vendor>:<model>:<flags>
2196 (flags are integer value)
2198 scsi_logging_level= [SCSI] a bit mask of logging levels
2199 See drivers/scsi/scsi_logging.h for bits. Also
2200 settable via sysctl at dev.scsi.logging_level
2201 (/proc/sys/dev/scsi/logging_level).
2202 There is also a nice 'scsi_logging_level' script in the
2203 S390-tools package, available for download at
2204 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2206 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2207 discovered. async scans them in kernel threads,
2208 allowing boot to proceed. none ignores them, expecting
2209 user space to do the scan.
2211 security= [SECURITY] Choose a security module to enable at boot.
2212 If this boot parameter is not specified, only the first
2213 security module asking for security registration will be
2214 loaded. An invalid security module name will be treated
2215 as if no module has been chosen.
2217 selinux= [SELINUX] Disable or enable SELinux at boot time.
2218 Format: { "0" | "1" }
2219 See security/selinux/Kconfig help text.
2220 0 -- disable.
2221 1 -- enable.
2222 Default value is set via kernel config option.
2223 If enabled at boot time, /selinux/disable can be used
2224 later to disable prior to initial policy load.
2226 serialnumber [BUGS=X86-32]
2228 shapers= [NET]
2229 Maximal number of shapers.
2231 show_msr= [x86] show boot-time MSR settings
2232 Format: { <integer> }
2233 Show boot-time (BIOS-initialized) MSR settings.
2234 The parameter means the number of CPUs to show,
2235 for example 1 means boot CPU only.
2237 sim710= [SCSI,HW]
2238 See header of drivers/scsi/sim710.c.
2240 simeth= [IA-64]
2241 simscsi=
2243 slram= [HW,MTD]
2245 slub_debug[=options[,slabs]] [MM, SLUB]
2246 Enabling slub_debug allows one to determine the
2247 culprit if slab objects become corrupted. Enabling
2248 slub_debug can create guard zones around objects and
2249 may poison objects when not in use. Also tracks the
2250 last alloc / free. For more information see
2251 Documentation/vm/slub.txt.
2253 slub_max_order= [MM, SLUB]
2254 Determines the maximum allowed order for slabs.
2255 A high setting may cause OOMs due to memory
2256 fragmentation. For more information see
2257 Documentation/vm/slub.txt.
2259 slub_min_objects= [MM, SLUB]
2260 The minimum number of objects per slab. SLUB will
2261 increase the slab order up to slub_max_order to
2262 generate a sufficiently large slab able to contain
2263 the number of objects indicated. The higher the number
2264 of objects the smaller the overhead of tracking slabs
2265 and the less frequently locks need to be acquired.
2266 For more information see Documentation/vm/slub.txt.
2268 slub_min_order= [MM, SLUB]
2269 Determines the mininum page order for slabs. Must be
2270 lower than slub_max_order.
2271 For more information see Documentation/vm/slub.txt.
2273 slub_nomerge [MM, SLUB]
2274 Disable merging of slabs with similar size. May be
2275 necessary if there is some reason to distinguish
2276 allocs to different slabs. Debug options disable
2277 merging on their own.
2278 For more information see Documentation/vm/slub.txt.
2280 smart2= [HW]
2281 Format: <io1>[,<io2>[,...,<io8>]]
2283 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2284 attempt to substitute SMP alternatives once at boot.
2286 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2287 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2288 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2289 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2290 smsc-ircc2.ircc_irq= [HW] IRQ line
2291 smsc-ircc2.ircc_dma= [HW] DMA channel
2292 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2293 0: Toshiba Satellite 1800 (GP data pin select)
2294 1: Fast pin select (default)
2295 2: ATC IRMode
2297 snd-ad1816a= [HW,ALSA]
2299 snd-ad1848= [HW,ALSA]
2301 snd-ali5451= [HW,ALSA]
2303 snd-als100= [HW,ALSA]
2305 snd-als4000= [HW,ALSA]
2307 snd-azt2320= [HW,ALSA]
2309 snd-cmi8330= [HW,ALSA]
2311 snd-cmipci= [HW,ALSA]
2313 snd-cs4231= [HW,ALSA]
2315 snd-cs4232= [HW,ALSA]
2317 snd-cs4236= [HW,ALSA]
2319 snd-cs4281= [HW,ALSA]
2321 snd-cs46xx= [HW,ALSA]
2323 snd-dt019x= [HW,ALSA]
2325 snd-dummy= [HW,ALSA]
2327 snd-emu10k1= [HW,ALSA]
2329 snd-ens1370= [HW,ALSA]
2331 snd-ens1371= [HW,ALSA]
2333 snd-es968= [HW,ALSA]
2335 snd-es1688= [HW,ALSA]
2337 snd-es18xx= [HW,ALSA]
2339 snd-es1938= [HW,ALSA]
2341 snd-es1968= [HW,ALSA]
2343 snd-fm801= [HW,ALSA]
2345 snd-gusclassic= [HW,ALSA]
2347 snd-gusextreme= [HW,ALSA]
2349 snd-gusmax= [HW,ALSA]
2351 snd-hdsp= [HW,ALSA]
2353 snd-ice1712= [HW,ALSA]
2355 snd-intel8x0= [HW,ALSA]
2357 snd-interwave= [HW,ALSA]
2359 snd-interwave-stb=
2360 [HW,ALSA]
2362 snd-korg1212= [HW,ALSA]
2364 snd-maestro3= [HW,ALSA]
2366 snd-mpu401= [HW,ALSA]
2368 snd-mtpav= [HW,ALSA]
2370 snd-nm256= [HW,ALSA]
2372 snd-opl3sa2= [HW,ALSA]
2374 snd-opti92x-ad1848=
2375 [HW,ALSA]
2377 snd-opti92x-cs4231=
2378 [HW,ALSA]
2380 snd-opti93x= [HW,ALSA]
2382 snd-pmac= [HW,ALSA]
2384 snd-rme32= [HW,ALSA]
2386 snd-rme96= [HW,ALSA]
2388 snd-rme9652= [HW,ALSA]
2390 snd-sb8= [HW,ALSA]
2392 snd-sb16= [HW,ALSA]
2394 snd-sbawe= [HW,ALSA]
2396 snd-serial= [HW,ALSA]
2398 snd-sgalaxy= [HW,ALSA]
2400 snd-sonicvibes= [HW,ALSA]
2402 snd-sun-amd7930=
2403 [HW,ALSA]
2405 snd-sun-cs4231= [HW,ALSA]
2407 snd-trident= [HW,ALSA]
2409 snd-usb-audio= [HW,ALSA,USB]
2411 snd-via82xx= [HW,ALSA]
2413 snd-virmidi= [HW,ALSA]
2415 snd-wavefront= [HW,ALSA]
2417 snd-ymfpci= [HW,ALSA]
2419 softlockup_panic=
2420 [KNL] Should the soft-lockup detector generate panics.
2422 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2423 See Documentation/sonypi.txt
2425 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2426 See Documentation/serial/specialix.txt.
2428 spia_io_base= [HW,MTD]
2429 spia_fio_base=
2430 spia_pedr=
2431 spia_peddr=
2433 sscape= [HW,OSS]
2434 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2436 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2437 See Documentation/scsi/st.txt.
2439 stacktrace [FTRACE]
2440 Enabled the stack tracer on boot up.
2442 sti= [PARISC,HW]
2443 Format: <num>
2444 Set the STI (builtin display/keyboard on the HP-PARISC
2445 machines) console (graphic card) which should be used
2446 as the initial boot-console.
2447 See also comment in drivers/video/console/sticore.c.
2449 sti_font= [HW]
2450 See comment in drivers/video/console/sticore.c.
2452 stifb= [HW]
2453 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2455 sunrpc.min_resvport=
2456 sunrpc.max_resvport=
2457 [NFS,SUNRPC]
2458 SunRPC servers often require that client requests
2459 originate from a privileged port (i.e. a port in the
2460 range 0 < portnr < 1024).
2461 An administrator who wishes to reserve some of these
2462 ports for other uses may adjust the range that the
2463 kernel's sunrpc client considers to be privileged
2464 using these two parameters to set the minimum and
2465 maximum port values.
2467 sunrpc.pool_mode=
2468 [NFS]
2469 Control how the NFS server code allocates CPUs to
2470 service thread pools. Depending on how many NICs
2471 you have and where their interrupts are bound, this
2472 option will affect which CPUs will do NFS serving.
2473 Note: this parameter cannot be changed while the
2474 NFS server is running.
2476 auto the server chooses an appropriate mode
2477 automatically using heuristics
2478 global a single global pool contains all CPUs
2479 percpu one pool for each CPU
2480 pernode one pool for each NUMA node (equivalent
2481 to global on non-NUMA machines)
2483 sunrpc.tcp_slot_table_entries=
2484 sunrpc.udp_slot_table_entries=
2485 [NFS,SUNRPC]
2486 Sets the upper limit on the number of simultaneous
2487 RPC calls that can be sent from the client to a
2488 server. Increasing these values may allow you to
2489 improve throughput, but will also increase the
2490 amount of memory reserved for use by the client.
2492 swiotlb= [IA-64] Number of I/O TLB slabs
2494 switches= [HW,M68k]
2496 sym53c416= [HW,SCSI]
2497 See header of drivers/scsi/sym53c416.c.
2499 sysrq_always_enabled
2500 [KNL]
2501 Ignore sysrq setting - this boot parameter will
2502 neutralize any effect of /proc/sys/kernel/sysrq.
2503 Useful for debugging.
2505 t128= [HW,SCSI]
2506 See header of drivers/scsi/t128.c.
2508 tdfx= [HW,DRM]
2510 test_suspend= [SUSPEND]
2511 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2512 standby suspend) as the system sleep state to briefly
2513 enter during system startup. The system is woken from
2514 this state using a wakeup-capable RTC alarm.
2516 thash_entries= [KNL,NET]
2517 Set number of hash buckets for TCP connection
2519 thermal.act= [HW,ACPI]
2520 -1: disable all active trip points in all thermal zones
2521 <degrees C>: override all lowest active trip points
2523 thermal.crt= [HW,ACPI]
2524 -1: disable all critical trip points in all thermal zones
2525 <degrees C>: override all critical trip points
2527 thermal.nocrt= [HW,ACPI]
2528 Set to disable actions on ACPI thermal zone
2529 critical and hot trip points.
2531 thermal.off= [HW,ACPI]
2532 1: disable ACPI thermal control
2534 thermal.psv= [HW,ACPI]
2535 -1: disable all passive trip points
2536 <degrees C>: override all passive trip points to this
2537 value
2539 thermal.tzp= [HW,ACPI]
2540 Specify global default ACPI thermal zone polling rate
2541 <deci-seconds>: poll all this frequency
2542 0: no polling (default)
2544 tmscsim= [HW,SCSI]
2545 See comment before function dc390_setup() in
2546 drivers/scsi/tmscsim.c.
2548 topology= [S390]
2549 Format: {off | on}
2550 Specify if the kernel should make use of the cpu
2551 topology informations if the hardware supports these.
2552 The scheduler will make use of these informations and
2553 e.g. base its process migration decisions on it.
2554 Default is off.
2556 tp720= [HW,PS2]
2558 trace_buf_size=nn[KMG]
2559 [FTRACE] will set tracing buffer size.
2561 trace_event=[event-list]
2562 [FTRACE] Set and start specified trace events in order
2563 to facilitate early boot debugging.
2564 See also Documentation/trace/events.txt
2566 trix= [HW,OSS] MediaTrix AudioTrix Pro
2567 Format:
2568 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2570 tsc= Disable clocksource-must-verify flag for TSC.
2571 Format: <string>
2572 [x86] reliable: mark tsc clocksource as reliable, this
2573 disables clocksource verification at runtime.
2574 Used to enable high-resolution timer mode on older
2575 hardware, and in virtualized environment.
2577 turbografx.map[2|3]= [HW,JOY]
2578 TurboGraFX parallel port interface
2579 Format:
2580 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2581 See also Documentation/input/joystick-parport.txt
2583 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2584 See header of drivers/scsi/u14-34f.c.
2586 uart401= [HW,OSS]
2587 Format: <io>,<irq>
2589 uart6850= [HW,OSS]
2590 Format: <io>,<irq>
2592 uhci-hcd.ignore_oc=
2593 [USB] Ignore overcurrent events (default N).
2594 Some badly-designed motherboards generate lots of
2595 bogus events, for ports that aren't wired to
2596 anything. Set this parameter to avoid log spamming.
2597 Note that genuine overcurrent events won't be
2598 reported either.
2600 unknown_nmi_panic
2601 [X86]
2602 Set unknown_nmi_panic=1 early on boot.
2604 usbcore.autosuspend=
2605 [USB] The autosuspend time delay (in seconds) used
2606 for newly-detected USB devices (default 2). This
2607 is the time required before an idle device will be
2608 autosuspended. Devices for which the delay is set
2609 to a negative value won't be autosuspended at all.
2611 usbcore.usbfs_snoop=
2612 [USB] Set to log all usbfs traffic (default 0 = off).
2614 usbcore.blinkenlights=
2615 [USB] Set to cycle leds on hubs (default 0 = off).
2617 usbcore.old_scheme_first=
2618 [USB] Start with the old device initialization
2619 scheme (default 0 = off).
2621 usbcore.use_both_schemes=
2622 [USB] Try the other device initialization scheme
2623 if the first one fails (default 1 = enabled).
2625 usbcore.initial_descriptor_timeout=
2626 [USB] Specifies timeout for the initial 64-byte
2627 USB_REQ_GET_DESCRIPTOR request in milliseconds
2628 (default 5000 = 5.0 seconds).
2630 usbhid.mousepoll=
2631 [USBHID] The interval which mice are to be polled at.
2633 usb-storage.delay_use=
2634 [UMS] The delay in seconds before a new device is
2635 scanned for Logical Units (default 5).
2637 usb-storage.quirks=
2638 [UMS] A list of quirks entries to supplement or
2639 override the built-in unusual_devs list. List
2640 entries are separated by commas. Each entry has
2641 the form VID:PID:Flags where VID and PID are Vendor
2642 and Product ID values (4-digit hex numbers) and
2643 Flags is a set of characters, each corresponding
2644 to a common usb-storage quirk flag as follows:
2645 a = SANE_SENSE (collect more than 18 bytes
2646 of sense data);
2647 c = FIX_CAPACITY (decrease the reported
2648 device capacity by one sector);
2649 h = CAPACITY_HEURISTICS (decrease the
2650 reported device capacity by one
2651 sector if the number is odd);
2652 i = IGNORE_DEVICE (don't bind to this
2653 device);
2654 l = NOT_LOCKABLE (don't try to lock and
2655 unlock ejectable media);
2656 m = MAX_SECTORS_64 (don't transfer more
2657 than 64 sectors = 32 KB at a time);
2658 o = CAPACITY_OK (accept the capacity
2659 reported by the device);
2660 r = IGNORE_RESIDUE (the device reports
2661 bogus residue values);
2662 s = SINGLE_LUN (the device has only one
2663 Logical Unit);
2664 w = NO_WP_DETECT (don't test whether the
2665 medium is write-protected).
2666 Example: quirks=0419:aaf5:rl,0421:0433:rc
2668 vdso= [X86,SH]
2669 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2670 vdso=1: enable VDSO (default)
2671 vdso=0: disable VDSO mapping
2673 vdso32= [X86]
2674 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2675 vdso32=1: enable 32-bit VDSO (default)
2676 vdso32=0: disable 32-bit VDSO mapping
2678 vector= [IA-64,SMP]
2679 vector=percpu: enable percpu vector domain
2681 video= [FB] Frame buffer configuration
2682 See Documentation/fb/modedb.txt.
2684 vga= [BOOT,X86-32] Select a particular video mode
2685 See Documentation/x86/boot.txt and
2686 Documentation/svga.txt.
2687 Use vga=ask for menu.
2688 This is actually a boot loader parameter; the value is
2689 passed to the kernel using a special protocol.
2691 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2692 size of <nn>. This can be used to increase the
2693 minimum size (128MB on x86). It can also be used to
2694 decrease the size and leave more room for directly
2695 mapped kernel RAM.
2697 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2698 Format: <command>
2700 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2701 Format: <command>
2703 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2704 Format: <command>
2706 vt.default_blu= [VT]
2707 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2708 Change the default blue palette of the console.
2709 This is a 16-member array composed of values
2710 ranging from 0-255.
2712 vt.default_grn= [VT]
2713 Format: <green0>,<green1>,<green2>,...,<green15>
2714 Change the default green palette of the console.
2715 This is a 16-member array composed of values
2716 ranging from 0-255.
2718 vt.default_red= [VT]
2719 Format: <red0>,<red1>,<red2>,...,<red15>
2720 Change the default red palette of the console.
2721 This is a 16-member array composed of values
2722 ranging from 0-255.
2724 vt.default_utf8=
2725 [VT]
2726 Format=<0|1>
2727 Set system-wide default UTF-8 mode for all tty's.
2728 Default is 1, i.e. UTF-8 mode is enabled for all
2729 newly opened terminals.
2731 waveartist= [HW,OSS]
2732 Format: <io>,<irq>,<dma>,<dma2>
2734 wd33c93= [HW,SCSI]
2735 See header of drivers/scsi/wd33c93.c.
2737 wd7000= [HW,SCSI]
2738 See header of drivers/scsi/wd7000.c.
2740 wdt= [WDT] Watchdog
2741 See Documentation/watchdog/wdt.txt.
2743 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2744 default x2apic cluster mode on platforms
2745 supporting x2apic.
2747 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2748 xd_geo= See header of drivers/block/xd.c.
2750 xirc2ps_cs= [NET,PCMCIA]
2751 Format:
2752 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2754 ______________________________________________________________________
2756 TODO:
2758 Add documentation for ALSA options.
2759 Add more DRM drivers.