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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=ttySn[,baudrate]
675 earlyprintk=dbgp[debugController#]
677 Append ",keep" to not disable it when the real console
678 takes over.
680 Only vga or serial or usb debug port at a time.
682 Currently only ttyS0 and ttyS1 are supported.
684 Interaction with the standard serial driver is not
685 very good.
687 The VGA output is eventually overwritten by the real
688 console.
690 eata= [HW,SCSI]
692 edd= [EDD]
693 Format: {"off" | "on" | "skip[mbr]"}
695 eisa_irq_edge= [PARISC,HW]
696 See header of drivers/parisc/eisa.c.
698 elanfreq= [X86-32]
699 See comment before function elanfreq_setup() in
700 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
702 elevator= [IOSCHED]
703 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
704 See Documentation/block/as-iosched.txt and
705 Documentation/block/deadline-iosched.txt for details.
707 elfcorehdr= [IA64,PPC,SH,X86]
708 Specifies physical address of start of kernel core
709 image elf header. Generally kexec loader will
710 pass this option to capture kernel.
711 See Documentation/kdump/kdump.txt for details.
713 enable_mtrr_cleanup [X86]
714 The kernel tries to adjust MTRR layout from continuous
715 to discrete, to make X server driver able to add WB
716 entry later. This parameter enables that.
718 enable_timer_pin_1 [X86]
719 Enable PIN 1 of APIC timer
720 Can be useful to work around chipset bugs
721 (in particular on some ATI chipsets).
722 The kernel tries to set a reasonable default.
724 enforcing [SELINUX] Set initial enforcing status.
725 Format: {"0" | "1"}
726 See security/selinux/Kconfig help text.
727 0 -- permissive (log only, no denials).
728 1 -- enforcing (deny and log).
729 Default value is 0.
730 Value can be changed at runtime via /selinux/enforce.
732 ether= [HW,NET] Ethernet cards parameters
733 This option is obsoleted by the "netdev=" option, which
734 has equivalent usage. See its documentation for details.
736 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
737 Format: <io>[,<irq>]
739 failslab=
740 fail_page_alloc=
741 fail_make_request=[KNL]
742 General fault injection mechanism.
743 Format: <interval>,<probability>,<space>,<times>
744 See also /Documentation/fault-injection/.
746 fd_mcs= [HW,SCSI]
747 See header of drivers/scsi/fd_mcs.c.
749 fdomain= [HW,SCSI]
750 See header of drivers/scsi/fdomain.c.
752 floppy= [HW]
753 See Documentation/blockdev/floppy.txt.
755 force_pal_cache_flush
756 [IA-64] Avoid check_sal_cache_flush which may hang on
757 buggy SAL_CACHE_FLUSH implementations. Using this
758 parameter will force ia64_sal_cache_flush to call
759 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
761 ftrace=[tracer]
762 [FTRACE] will set and start the specified tracer
763 as early as possible in order to facilitate early
764 boot debugging.
766 ftrace_dump_on_oops
767 [FTRACE] will dump the trace buffers on oops.
769 ftrace_filter=[function-list]
770 [FTRACE] Limit the functions traced by the function
771 tracer at boot up. function-list is a comma separated
772 list of functions. This list can be changed at run
773 time by the set_ftrace_filter file in the debugfs
774 tracing directory.
776 ftrace_notrace=[function-list]
777 [FTRACE] Do not trace the functions specified in
778 function-list. This list can be changed at run time
779 by the set_ftrace_notrace file in the debugfs
780 tracing directory.
782 ftrace_graph_filter=[function-list]
783 [FTRACE] Limit the top level callers functions traced
784 by the function graph tracer at boot up.
785 function-list is a comma separated list of functions
786 that can be changed at run time by the
787 set_graph_function file in the debugfs tracing directory.
789 gamecon.map[2|3]=
790 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
791 support via parallel port (up to 5 devices per port)
792 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
793 See also Documentation/input/joystick-parport.txt
795 gamma= [HW,DRM]
797 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
798 Format: off | on
799 default: on
801 gcov_persist= [GCOV] When non-zero (default), profiling data for
802 kernel modules is saved and remains accessible via
803 debugfs, even when the module is unloaded/reloaded.
804 When zero, profiling data is discarded and associated
805 debugfs files are removed at module unload time.
807 gdth= [HW,SCSI]
808 See header of drivers/scsi/gdth.c.
810 gpt [EFI] Forces disk with valid GPT signature but
811 invalid Protective MBR to be treated as GPT.
813 gvp11= [HW,SCSI]
815 hashdist= [KNL,NUMA] Large hashes allocated during boot
816 are distributed across NUMA nodes. Defaults on
817 for 64bit NUMA, off otherwise.
818 Format: 0 | 1 (for off | on)
820 hcl= [IA-64] SGI's Hardware Graph compatibility layer
822 hd= [EIDE] (E)IDE hard drive subsystem geometry
823 Format: <cyl>,<head>,<sect>
825 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
826 size of <nn>. This works even on boxes that have no
827 highmem otherwise. This also works to reduce highmem
828 size on bigger boxes.
830 highres= [KNL] Enable/disable high resolution timer mode.
831 Valid parameters: "on", "off"
832 Default: "on"
834 hisax= [HW,ISDN]
835 See Documentation/isdn/README.HiSax.
837 hlt [BUGS=ARM,SH]
839 hpet= [X86-32,HPET] option to control HPET usage
840 Format: { enable (default) | disable | force |
841 verbose }
842 disable: disable HPET and use PIT instead
843 force: allow force enabled of undocumented chips (ICH4,
844 VIA, nVidia)
845 verbose: show contents of HPET registers during setup
847 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
848 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
849 On x86-64 and powerpc, this option can be specified
850 multiple times interleaved with hugepages= to reserve
851 huge pages of different sizes. Valid pages sizes on
852 x86-64 are 2M (when the CPU supports "pse") and 1G
853 (when the CPU supports the "pdpe1gb" cpuinfo flag)
854 Note that 1GB pages can only be allocated at boot time
855 using hugepages= and not freed afterwards.
857 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
858 terminal devices. Valid values: 0..8
859 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
860 If specified, z/VM IUCV HVC accepts connections
861 from listed z/VM user IDs only.
863 i2c_bus= [HW] Override the default board specific I2C bus speed
864 or register an additional I2C bus that is not
865 registered from board initialization code.
866 Format:
867 <bus_id>,<clkrate>
869 i8042.debug [HW] Toggle i8042 debug mode
870 i8042.direct [HW] Put keyboard port into non-translated mode
871 i8042.dumbkbd [HW] Pretend that controller can only read data from
872 keyboard and cannot control its state
873 (Don't attempt to blink the leds)
874 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
875 i8042.nokbd [HW] Don't check/create keyboard port
876 i8042.noloop [HW] Disable the AUX Loopback command while probing
877 for the AUX port
878 i8042.nomux [HW] Don't check presence of an active multiplexing
879 controller
880 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
881 controllers
882 i8042.panicblink=
883 [HW] Frequency with which keyboard LEDs should blink
884 when kernel panics (default is 0.5 sec)
885 i8042.reset [HW] Reset the controller during init and cleanup
886 i8042.unlock [HW] Unlock (ignore) the keylock
888 i810= [HW,DRM]
890 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
891 indicates that the driver is running on unsupported
892 hardware.
893 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
894 does not match list of supported models.
895 i8k.power_status
896 [HW] Report power status in /proc/i8k
897 (disabled by default)
898 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
899 capability is set.
901 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
902 See Documentation/mca.txt.
904 icn= [HW,ISDN]
905 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
907 ide-core.nodma= [HW] (E)IDE subsystem
908 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
909 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
910 .cdrom .chs .ignore_cable are additional options
911 See Documentation/ide/ide.txt.
913 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
914 Claim all unknown PCI IDE storage controllers.
916 idle= [X86]
917 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
918 Poll forces a polling idle loop that can slightly
919 improve the performance of waking up a idle CPU, but
920 will use a lot of power and make the system run hot.
921 Not recommended.
922 idle=mwait: On systems which support MONITOR/MWAIT but
923 the kernel chose to not use it because it doesn't save
924 as much power as a normal idle loop, use the
925 MONITOR/MWAIT idle loop anyways. Performance should be
926 the same as idle=poll.
927 idle=halt: Halt is forced to be used for CPU idle.
928 In such case C2/C3 won't be used again.
929 idle=nomwait: Disable mwait for CPU C-states
931 ignore_loglevel [KNL]
932 Ignore loglevel setting - this will print /all/
933 kernel messages to the console. Useful for debugging.
935 ihash_entries= [KNL]
936 Set number of hash buckets for inode cache.
938 ima_audit= [IMA]
939 Format: { "0" | "1" }
940 0 -- integrity auditing messages. (Default)
941 1 -- enable informational integrity auditing messages.
943 ima_hash= [IMA]
944 Format: { "sha1" | "md5" }
945 default: "sha1"
947 ima_tcb [IMA]
948 Load a policy which meets the needs of the Trusted
949 Computing Base. This means IMA will measure all
950 programs exec'd, files mmap'd for exec, and all files
951 opened for read by uid=0.
953 in2000= [HW,SCSI]
954 See header of drivers/scsi/in2000.c.
956 init= [KNL]
957 Format: <full_path>
958 Run specified binary instead of /sbin/init as init
959 process.
961 initcall_debug [KNL] Trace initcalls as they are executed. Useful
962 for working out where the kernel is dying during
963 startup.
965 initrd= [BOOT] Specify the location of the initial ramdisk
967 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
968 Format: <irq>
970 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
971 on
972 Enable intel iommu driver.
973 off
974 Disable intel iommu driver.
975 igfx_off [Default Off]
976 By default, gfx is mapped as normal device. If a gfx
977 device has a dedicated DMAR unit, the DMAR unit is
978 bypassed by not enabling DMAR with this option. In
979 this case, gfx device will use physical address for
980 DMA.
981 forcedac [x86_64]
982 With this option iommu will not optimize to look
983 for io virtual address below 32 bit forcing dual
984 address cycle on pci bus for cards supporting greater
985 than 32 bit addressing. The default is to look
986 for translation below 32 bit and if not available
987 then look in the higher range.
988 strict [Default Off]
989 With this option on every unmap_single operation will
990 result in a hardware IOTLB flush operation as opposed
991 to batching them for performance.
993 inttest= [IA64]
995 iomem= Disable strict checking of access to MMIO memory
996 strict regions from userspace.
997 relaxed
999 iommu= [x86]
1000 off
1001 force
1002 noforce
1003 biomerge
1004 panic
1005 nopanic
1006 merge
1007 nomerge
1008 forcesac
1009 soft
1010 pt [x86, IA64]
1012 io7= [HW] IO7 for Marvel based alpha systems
1013 See comment before marvel_specify_io7 in
1014 arch/alpha/kernel/core_marvel.c.
1016 io_delay= [X86] I/O delay method
1017 0x80
1018 Standard port 0x80 based delay
1019 0xed
1020 Alternate port 0xed based delay (needed on some systems)
1021 udelay
1022 Simple two microseconds delay
1023 none
1024 No delay
1026 ip= [IP_PNP]
1027 See Documentation/filesystems/nfsroot.txt.
1029 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1030 See comment before ip2_setup() in
1031 drivers/char/ip2/ip2base.c.
1033 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1034 See header of drivers/scsi/ips.c.
1036 irqfixup [HW]
1037 When an interrupt is not handled search all handlers
1038 for it. Intended to get systems with badly broken
1039 firmware running.
1041 irqpoll [HW]
1042 When an interrupt is not handled search all handlers
1043 for it. Also check all handlers each timer
1044 interrupt. Intended to get systems with badly broken
1045 firmware running.
1047 isapnp= [ISAPNP]
1048 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1050 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1051 Format:
1052 <cpu number>,...,<cpu number>
1053 or
1054 <cpu number>-<cpu number>
1055 (must be a positive range in ascending order)
1056 or a mixture
1057 <cpu number>,...,<cpu number>-<cpu number>
1059 This option can be used to specify one or more CPUs
1060 to isolate from the general SMP balancing and scheduling
1061 algorithms. You can move a process onto or off an
1062 "isolated" CPU via the CPU affinity syscalls or cpuset.
1063 <cpu number> begins at 0 and the maximum value is
1064 "number of CPUs in system - 1".
1066 This option is the preferred way to isolate CPUs. The
1067 alternative -- manually setting the CPU mask of all
1068 tasks in the system -- can cause problems and
1069 suboptimal load balancer performance.
1071 iucv= [HW,NET]
1073 js= [HW,JOY] Analog joystick
1074 See Documentation/input/joystick.txt.
1076 keepinitrd [HW,ARM]
1078 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1079 specifies the amount of memory usable by the kernel
1080 for non-movable allocations. The requested amount is
1081 spread evenly throughout all nodes in the system. The
1082 remaining memory in each node is used for Movable
1083 pages. In the event, a node is too small to have both
1084 kernelcore and Movable pages, kernelcore pages will
1085 take priority and other nodes will have a larger number
1086 of kernelcore pages. The Movable zone is used for the
1087 allocation of pages that may be reclaimed or moved
1088 by the page migration subsystem. This means that
1089 HugeTLB pages may not be allocated from this zone.
1090 Note that allocations like PTEs-from-HighMem still
1091 use the HighMem zone if it exists, and the Normal
1092 zone if it does not.
1094 kgdboc= [HW] kgdb over consoles.
1095 Requires a tty driver that supports console polling.
1096 (only serial supported for now)
1097 Format: <serial_device>[,baud]
1099 kmac= [MIPS] korina ethernet MAC address.
1100 Configure the RouterBoard 532 series on-chip
1101 Ethernet adapter MAC address.
1103 kmemleak= [KNL] Boot-time kmemleak enable/disable
1104 Valid arguments: on, off
1105 Default: on
1107 kstack=N [X86] Print N words from the kernel stack
1108 in oops dumps.
1110 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1111 Default is 0 (don't ignore, but inject #GP)
1113 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1114 Default is 1 (enabled)
1116 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1117 Default is 0 (off)
1119 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1120 for all guests.
1121 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1123 kvm-intel.bypass_guest_pf=
1124 [KVM,Intel] Disables bypassing of guest page faults
1125 on Intel chips. Default is 1 (enabled)
1127 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1128 (virtualized MMU) support on capable Intel chips.
1129 Default is 1 (enabled)
1131 kvm-intel.emulate_invalid_guest_state=
1132 [KVM,Intel] Enable emulation of invalid guest states
1133 Default is 0 (disabled)
1135 kvm-intel.flexpriority=
1136 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1137 Default is 1 (enabled)
1139 kvm-intel.unrestricted_guest=
1140 [KVM,Intel] Disable unrestricted guest feature
1141 (virtualized real and unpaged mode) on capable
1142 Intel chips. Default is 1 (enabled)
1144 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1145 feature (tagged TLBs) on capable Intel chips.
1146 Default is 1 (enabled)
1148 l2cr= [PPC]
1150 l3cr= [PPC]
1152 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1153 disabled it.
1155 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1156 in C2 power state.
1158 libata.dma= [LIBATA] DMA control
1159 libata.dma=0 Disable all PATA and SATA DMA
1160 libata.dma=1 PATA and SATA Disk DMA only
1161 libata.dma=2 ATAPI (CDROM) DMA only
1162 libata.dma=4 Compact Flash DMA only
1163 Combinations also work, so libata.dma=3 enables DMA
1164 for disks and CDROMs, but not CFs.
1166 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1167 libata.ignore_hpa=0 keep BIOS limits (default)
1168 libata.ignore_hpa=1 ignore limits, using full disk
1170 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1171 when set.
1172 Format: <int>
1174 libata.force= [LIBATA] Force configurations. The format is comma
1175 separated list of "[ID:]VAL" where ID is
1176 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1177 matching port, link or device. Basically, it matches
1178 the ATA ID string printed on console by libata. If
1179 the whole ID part is omitted, the last PORT and DEVICE
1180 values are used. If ID hasn't been specified yet, the
1181 configuration applies to all ports, links and devices.
1183 If only DEVICE is omitted, the parameter applies to
1184 the port and all links and devices behind it. DEVICE
1185 number of 0 either selects the first device or the
1186 first fan-out link behind PMP device. It does not
1187 select the host link. DEVICE number of 15 selects the
1188 host link and device attached to it.
1190 The VAL specifies the configuration to force. As long
1191 as there's no ambiguity shortcut notation is allowed.
1192 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1193 The following configurations can be forced.
1195 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1196 Any ID with matching PORT is used.
1198 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1200 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1201 udma[/][16,25,33,44,66,100,133] notation is also
1202 allowed.
1204 * [no]ncq: Turn on or off NCQ.
1206 * nohrst, nosrst, norst: suppress hard, soft
1207 and both resets.
1209 If there are multiple matching configurations changing
1210 the same attribute, the last one is used.
1212 lmb=debug [KNL] Enable lmb debug messages.
1214 load_ramdisk= [RAM] List of ramdisks to load from floppy
1215 See Documentation/blockdev/ramdisk.txt.
1217 lockd.nlm_grace_period=P [NFS] Assign grace period.
1218 Format: <integer>
1220 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1221 Format: <integer>
1223 lockd.nlm_timeout=T [NFS] Assign timeout value.
1224 Format: <integer>
1226 lockd.nlm_udpport=M [NFS] Assign UDP port.
1227 Format: <integer>
1229 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1230 Format: <irq>
1232 loglevel= All Kernel Messages with a loglevel smaller than the
1233 console loglevel will be printed to the console. It can
1234 also be changed with klogd or other programs. The
1235 loglevels are defined as follows:
1237 0 (KERN_EMERG) system is unusable
1238 1 (KERN_ALERT) action must be taken immediately
1239 2 (KERN_CRIT) critical conditions
1240 3 (KERN_ERR) error conditions
1241 4 (KERN_WARNING) warning conditions
1242 5 (KERN_NOTICE) normal but significant condition
1243 6 (KERN_INFO) informational
1244 7 (KERN_DEBUG) debug-level messages
1246 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1247 Format: { n | nk | nM }
1248 n must be a power of two. The default size
1249 is set in the kernel config file.
1251 logo.nologo [FB] Disables display of the built-in Linux logo.
1252 This may be used to provide more screen space for
1253 kernel log messages and is useful when debugging
1254 kernel boot problems.
1256 lp=0 [LP] Specify parallel ports to use, e.g,
1257 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1258 lp=reset first parallel port). 'lp=0' disables the
1259 lp=auto printer driver. 'lp=reset' (which can be
1260 specified in addition to the ports) causes
1261 attached printers to be reset. Using
1262 lp=port1,port2,... specifies the parallel ports
1263 to associate lp devices with, starting with
1264 lp0. A port specification may be 'none' to skip
1265 that lp device, or a parport name such as
1266 'parport0'. Specifying 'lp=auto' instead of a
1267 port specification list means that device IDs
1268 from each port should be examined, to see if
1269 an IEEE 1284-compliant printer is attached; if
1270 so, the driver will manage that printer.
1271 See also header of drivers/char/lp.c.
1273 lpj=n [KNL]
1274 Sets loops_per_jiffy to given constant, thus avoiding
1275 time-consuming boot-time autodetection (up to 250 ms per
1276 CPU). 0 enables autodetection (default). To determine
1277 the correct value for your kernel, boot with normal
1278 autodetection and see what value is printed. Note that
1279 on SMP systems the preset will be applied to all CPUs,
1280 which is likely to cause problems if your CPUs need
1281 significantly divergent settings. An incorrect value
1282 will cause delays in the kernel to be wrong, leading to
1283 unpredictable I/O errors and other breakage. Although
1284 unlikely, in the extreme case this might damage your
1285 hardware.
1287 ltpc= [NET]
1288 Format: <io>,<irq>,<dma>
1290 mac5380= [HW,SCSI] Format:
1291 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1293 machvec= [IA64] Force the use of a particular machine-vector
1294 (machvec) in a generic kernel.
1295 Example: machvec=hpzx1_swiotlb
1297 machtype= [Loongson] Share the same kernel image file between different
1298 yeeloong laptop.
1299 Example: machtype=lemote-yeeloong-2f-7inch
1301 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1302 than or equal to this physical address is ignored.
1304 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1305 should make use of. maxcpus=n : n >= 0 limits the
1306 kernel to using 'n' processors. n=0 is a special case,
1307 it is equivalent to "nosmp", which also disables
1308 the IO APIC.
1310 max_loop= [LOOP] Maximum number of loopback devices that can
1311 be mounted
1312 Format: <1-256>
1314 max_luns= [SCSI] Maximum number of LUNs to probe.
1315 Should be between 1 and 2^32-1.
1317 max_report_luns=
1318 [SCSI] Maximum number of LUNs received.
1319 Should be between 1 and 16384.
1321 mcatest= [IA-64]
1323 mce [X86-32] Machine Check Exception
1325 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1327 md= [HW] RAID subsystems devices and level
1328 See Documentation/md.txt.
1330 mdacon= [MDA]
1331 Format: <first>,<last>
1332 Specifies range of consoles to be captured by the MDA.
1334 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1335 Amount of memory to be used when the kernel is not able
1336 to see the whole system memory or for test.
1337 [X86-32] Use together with memmap= to avoid physical
1338 address space collisions. Without memmap= PCI devices
1339 could be placed at addresses belonging to unused RAM.
1341 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1342 memory.
1344 memchunk=nn[KMG]
1345 [KNL,SH] Allow user to override the default size for
1346 per-device physically contiguous DMA buffers.
1348 memmap=exactmap [KNL,X86] Enable setting of an exact
1349 E820 memory map, as specified by the user.
1350 Such memmap=exactmap lines can be constructed based on
1351 BIOS output or other requirements. See the memmap=nn@ss
1352 option description.
1354 memmap=nn[KMG]@ss[KMG]
1355 [KNL] Force usage of a specific region of memory
1356 Region of memory to be used, from ss to ss+nn.
1358 memmap=nn[KMG]#ss[KMG]
1359 [KNL,ACPI] Mark specific memory as ACPI data.
1360 Region of memory to be used, from ss to ss+nn.
1362 memmap=nn[KMG]$ss[KMG]
1363 [KNL,ACPI] Mark specific memory as reserved.
1364 Region of memory to be used, from ss to ss+nn.
1365 Example: Exclude memory from 0x18690000-0x1869ffff
1366 memmap=64K$0x18690000
1367 or
1368 memmap=0x10000$0x18690000
1370 memory_corruption_check=0/1 [X86]
1371 Some BIOSes seem to corrupt the first 64k of
1372 memory when doing things like suspend/resume.
1373 Setting this option will scan the memory
1374 looking for corruption. Enabling this will
1375 both detect corruption and prevent the kernel
1376 from using the memory being corrupted.
1377 However, its intended as a diagnostic tool; if
1378 repeatable BIOS-originated corruption always
1379 affects the same memory, you can use memmap=
1380 to prevent the kernel from using that memory.
1382 memory_corruption_check_size=size [X86]
1383 By default it checks for corruption in the low
1384 64k, making this memory unavailable for normal
1385 use. Use this parameter to scan for
1386 corruption in more or less memory.
1388 memory_corruption_check_period=seconds [X86]
1389 By default it checks for corruption every 60
1390 seconds. Use this parameter to check at some
1391 other rate. 0 disables periodic checking.
1393 memtest= [KNL,X86] Enable memtest
1394 Format: <integer>
1395 default : 0 <disable>
1396 Specifies the number of memtest passes to be
1397 performed. Each pass selects another test
1398 pattern from a given set of patterns. Memtest
1399 fills the memory with this pattern, validates
1400 memory contents and reserves bad memory
1401 regions that are detected.
1403 meye.*= [HW] Set MotionEye Camera parameters
1404 See Documentation/video4linux/meye.txt.
1406 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1407 Multi-Function General Purpose Timers on AMD Geode
1408 platforms.
1410 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1411 the BIOS has incorrectly applied a workaround. TinyBIOS
1412 version 0.98 is known to be affected, 0.99 fixes the
1413 problem by letting the user disable the workaround.
1415 mga= [HW,DRM]
1417 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1418 physical address is ignored.
1420 mini2440= [ARM,HW,KNL]
1421 Format:[0..2][b][c][t]
1422 Default: "0tb"
1423 MINI2440 configuration specification:
1424 0 - The attached screen is the 3.5" TFT
1425 1 - The attached screen is the 7" TFT
1426 2 - The VGA Shield is attached (1024x768)
1427 Leaving out the screen size parameter will not load
1428 the TFT driver, and the framebuffer will be left
1429 unconfigured.
1430 b - Enable backlight. The TFT backlight pin will be
1431 linked to the kernel VESA blanking code and a GPIO
1432 LED. This parameter is not necessary when using the
1433 VGA shield.
1434 c - Enable the s3c camera interface.
1435 t - Reserved for enabling touchscreen support. The
1436 touchscreen support is not enabled in the mainstream
1437 kernel as of 2.6.30, a preliminary port can be found
1438 in the "bleeding edge" mini2440 support kernel at
1439 http://repo.or.cz/w/linux-2.6/mini2440.git
1441 mminit_loglevel=
1442 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1443 parameter allows control of the logging verbosity for
1444 the additional memory initialisation checks. A value
1445 of 0 disables mminit logging and a level of 4 will
1446 log everything. Information is printed at KERN_DEBUG
1447 so loglevel=8 may also need to be specified.
1449 mousedev.tap_time=
1450 [MOUSE] Maximum time between finger touching and
1451 leaving touchpad surface for touch to be considered
1452 a tap and be reported as a left button click (for
1453 touchpads working in absolute mode only).
1454 Format: <msecs>
1455 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1456 reporting absolute coordinates, such as tablets
1457 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1458 reporting absolute coordinates, such as tablets
1460 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1461 is similar to kernelcore except it specifies the
1462 amount of memory used for migratable allocations.
1463 If both kernelcore and movablecore is specified,
1464 then kernelcore will be at *least* the specified
1465 value but may be more. If movablecore on its own
1466 is specified, the administrator must be careful
1467 that the amount of memory usable for all allocations
1468 is not too small.
1470 mpu401= [HW,OSS]
1471 Format: <io>,<irq>
1473 MTD_Partition= [MTD]
1474 Format: <name>,<region-number>,<size>,<offset>
1476 MTD_Region= [MTD] Format:
1477 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1479 mtdparts= [MTD]
1480 See drivers/mtd/cmdlinepart.c.
1482 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1484 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1486 boundary - index of last SLC block on Flex-OneNAND.
1487 The remaining blocks are configured as MLC blocks.
1488 lock - Configure if Flex-OneNAND boundary should be locked.
1489 Once locked, the boundary cannot be changed.
1490 1 indicates lock status, 0 indicates unlock status.
1492 mtdset= [ARM]
1493 ARM/S3C2412 JIVE boot control
1495 See arch/arm/mach-s3c2412/mach-jive.c
1497 mtouchusb.raw_coordinates=
1498 [HW] Make the MicroTouch USB driver use raw coordinates
1499 ('y', default) or cooked coordinates ('n')
1501 mtrr_chunk_size=nn[KMG] [X86]
1502 used for mtrr cleanup. It is largest continuous chunk
1503 that could hold holes aka. UC entries.
1505 mtrr_gran_size=nn[KMG] [X86]
1506 Used for mtrr cleanup. It is granularity of mtrr block.
1507 Default is 1.
1508 Large value could prevent small alignment from
1509 using up MTRRs.
1511 mtrr_spare_reg_nr=n [X86]
1512 Format: <integer>
1513 Range: 0,7 : spare reg number
1514 Default : 1
1515 Used for mtrr cleanup. It is spare mtrr entries number.
1516 Set to 2 or more if your graphical card needs more.
1518 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1520 NCR_D700= [HW,SCSI]
1521 See header of drivers/scsi/NCR_D700.c.
1523 ncr5380= [HW,SCSI]
1525 ncr53c400= [HW,SCSI]
1527 ncr53c400a= [HW,SCSI]
1529 ncr53c406a= [HW,SCSI]
1531 ncr53c8xx= [HW,SCSI]
1533 netdev= [NET] Network devices parameters
1534 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1535 Note that mem_start is often overloaded to mean
1536 something different and driver-specific.
1537 This usage is only documented in each driver source
1538 file if at all.
1540 nf_conntrack.acct=
1541 [NETFILTER] Enable connection tracking flow accounting
1542 0 to disable accounting
1543 1 to enable accounting
1544 Default value depends on CONFIG_NF_CT_ACCT that is
1545 going to be removed in 2.6.29.
1547 nfsaddrs= [NFS]
1548 See Documentation/filesystems/nfsroot.txt.
1550 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1551 See Documentation/filesystems/nfsroot.txt.
1553 nfs.callback_tcpport=
1554 [NFS] set the TCP port on which the NFSv4 callback
1555 channel should listen.
1557 nfs.cache_getent=
1558 [NFS] sets the pathname to the program which is used
1559 to update the NFS client cache entries.
1561 nfs.cache_getent_timeout=
1562 [NFS] sets the timeout after which an attempt to
1563 update a cache entry is deemed to have failed.
1565 nfs.idmap_cache_timeout=
1566 [NFS] set the maximum lifetime for idmapper cache
1567 entries.
1569 nfs.enable_ino64=
1570 [NFS] enable 64-bit inode numbers.
1571 If zero, the NFS client will fake up a 32-bit inode
1572 number for the readdir() and stat() syscalls instead
1573 of returning the full 64-bit number.
1574 The default is to return 64-bit inode numbers.
1576 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1577 when a NMI is triggered.
1578 Format: [state][,regs][,debounce][,die]
1580 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1581 Format: [panic,][num]
1582 Valid num: 0,1,2
1583 0 - turn nmi_watchdog off
1584 1 - use the IO-APIC timer for the NMI watchdog
1585 2 - use the local APIC for the NMI watchdog using
1586 a performance counter. Note: This will use one
1587 performance counter and the local APIC's performance
1588 vector.
1589 When panic is specified, panic when an NMI watchdog
1590 timeout occurs.
1591 This is useful when you use a panic=... timeout and
1592 need the box quickly up again.
1593 Instead of 1 and 2 it is possible to use the following
1594 symbolic names: lapic and ioapic
1595 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1597 netpoll.carrier_timeout=
1598 [NET] Specifies amount of time (in seconds) that
1599 netpoll should wait for a carrier. By default netpoll
1600 waits 4 seconds.
1602 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1603 emulation library even if a 387 maths coprocessor
1604 is present.
1606 no_console_suspend
1607 [HW] Never suspend the console
1608 Disable suspending of consoles during suspend and
1609 hibernate operations. Once disabled, debugging
1610 messages can reach various consoles while the rest
1611 of the system is being put to sleep (ie, while
1612 debugging driver suspend/resume hooks). This may
1613 not work reliably with all consoles, but is known
1614 to work with serial and VGA consoles.
1616 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1617 caches in the slab allocator. Saves per-node memory,
1618 but will impact performance.
1620 noalign [KNL,ARM]
1622 noapic [SMP,APIC] Tells the kernel to not make use of any
1623 IOAPICs that may be present in the system.
1625 nobats [PPC] Do not use BATs for mapping kernel lowmem
1626 on "Classic" PPC cores.
1628 nocache [ARM]
1630 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1632 nodelayacct [KNL] Disable per-task delay accounting
1634 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1636 nodsp [SH] Disable hardware DSP at boot time.
1638 noefi [X86] Disable EFI runtime services support.
1640 noexec [IA-64]
1642 noexec [X86]
1643 On X86-32 available only on PAE configured kernels.
1644 noexec=on: enable non-executable mappings (default)
1645 noexec=off: disable non-executable mappings
1647 noexec32 [X86-64]
1648 This affects only 32-bit executables.
1649 noexec32=on: enable non-executable mappings (default)
1650 read doesn't imply executable mappings
1651 noexec32=off: disable non-executable mappings
1652 read implies executable mappings
1654 nofpu [SH] Disable hardware FPU at boot time.
1656 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1657 register save and restore. The kernel will only save
1658 legacy floating-point registers on task switch.
1660 noxsave [BUGS=X86] Disables x86 extended register state save
1661 and restore using xsave. The kernel will fallback to
1662 enabling legacy floating-point and sse state.
1664 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1665 wfi(ARM) instruction doesn't work correctly and not to
1666 use it. This is also useful when using JTAG debugger.
1668 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1669 instruction doesn't work correctly and not to
1670 use it.
1672 no_file_caps Tells the kernel not to honor file capabilities. The
1673 only way then for a file to be executed with privilege
1674 is to be setuid root or executed by root.
1676 nohalt [IA-64] Tells the kernel not to use the power saving
1677 function PAL_HALT_LIGHT when idle. This increases
1678 power-consumption. On the positive side, it reduces
1679 interrupt wake-up latency, which may improve performance
1680 in certain environments such as networked servers or
1681 real-time systems.
1683 nohz= [KNL] Boottime enable/disable dynamic ticks
1684 Valid arguments: on, off
1685 Default: on
1687 noiotrap [SH] Disables trapped I/O port accesses.
1689 noirqdebug [X86-32] Disables the code which attempts to detect and
1690 disable unhandled interrupt sources.
1692 no_timer_check [X86,APIC] Disables the code which tests for
1693 broken timer IRQ sources.
1695 noisapnp [ISAPNP] Disables ISA PnP code.
1697 noinitrd [RAM] Tells the kernel not to load any configured
1698 initial RAM disk.
1700 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1701 remapping.
1703 nointroute [IA-64]
1705 nojitter [IA64] Disables jitter checking for ITC timers.
1707 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1709 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1711 noltlbs [PPC] Do not use large page/tlb entries for kernel
1712 lowmem mapping on PPC40x.
1714 nomca [IA-64] Disable machine check abort handling
1716 nomce [X86-32] Machine Check Exception
1718 nomfgpt [X86-32] Disable Multi-Function General Purpose
1719 Timer usage (for AMD Geode machines).
1721 norandmaps Don't use address space randomization. Equivalent to
1722 echo 0 > /proc/sys/kernel/randomize_va_space
1724 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1726 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1727 with UP alternatives
1729 noresidual [PPC] Don't use residual data on PReP machines.
1731 noresume [SWSUSP] Disables resume and restores original swap
1732 space.
1734 no-scroll [VGA] Disables scrollback.
1735 This is required for the Braillex ib80-piezo Braille
1736 reader made by F.H. Papenmeier (Germany).
1738 nosbagart [IA-64]
1740 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1742 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1743 and disable the IO APIC. legacy for "maxcpus=0".
1745 nosoftlockup [KNL] Disable the soft-lockup detector.
1747 noswapaccount [KNL] Disable accounting of swap in memory resource
1748 controller. (See Documentation/cgroups/memory.txt)
1750 nosync [HW,M68K] Disables sync negotiation for all devices.
1752 notsc [BUGS=X86-32] Disable Time Stamp Counter
1754 nousb [USB] Disable the USB subsystem
1756 nowb [ARM]
1758 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1760 nptcg= [IA64] Override max number of concurrent global TLB
1761 purges which is reported from either PAL_VM_SUMMARY or
1762 SAL PALO.
1764 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1766 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1767 one of ['zone', 'node', 'default'] can be specified
1768 This can be set from sysctl after boot.
1769 See Documentation/sysctl/vm.txt for details.
1771 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1772 See Documentation/debugging-via-ohci1394.txt for more
1773 info.
1775 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1776 Rather than timing out after 20 ms if an EC
1777 command is not properly ACKed, override the length
1778 of the timeout. We have interrupts disabled while
1779 waiting for the ACK, so if this is set too high
1780 interrupts *may* be lost!
1782 opl3= [HW,OSS]
1783 Format: <io>
1785 oprofile.timer= [HW]
1786 Use timer interrupt instead of performance counters
1788 oprofile.cpu_type= Force an oprofile cpu type
1789 This might be useful if you have an older oprofile
1790 userland or if you want common events.
1791 Format: { arch_perfmon }
1792 arch_perfmon: [X86] Force use of architectural
1793 perfmon on Intel CPUs instead of the
1794 CPU specific event set.
1796 osst= [HW,SCSI] SCSI Tape Driver
1797 Format: <buffer_size>,<write_threshold>
1798 See also Documentation/scsi/st.txt.
1800 panic= [KNL] Kernel behaviour on panic
1801 Format: <timeout>
1803 parkbd.port= [HW] Parallel port number the keyboard adapter is
1804 connected to, default is 0.
1805 Format: <parport#>
1806 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1807 0 for XT, 1 for AT (default is AT).
1808 Format: <mode>
1810 parport= [HW,PPT] Specify parallel ports. 0 disables.
1811 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1812 Use 'auto' to force the driver to use any
1813 IRQ/DMA settings detected (the default is to
1814 ignore detected IRQ/DMA settings because of
1815 possible conflicts). You can specify the base
1816 address, IRQ, and DMA settings; IRQ and DMA
1817 should be numbers, or 'auto' (for using detected
1818 settings on that particular port), or 'nofifo'
1819 (to avoid using a FIFO even if it is detected).
1820 Parallel ports are assigned in the order they
1821 are specified on the command line, starting
1822 with parport0.
1824 parport_init_mode= [HW,PPT]
1825 Configure VIA parallel port to operate in
1826 a specific mode. This is necessary on Pegasos
1827 computer where firmware has no options for setting
1828 up parallel port mode and sets it to spp.
1829 Currently this function knows 686a and 8231 chips.
1830 Format: [spp|ps2|epp|ecp|ecpepp]
1832 pas2= [HW,OSS] Format:
1833 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1835 pas16= [HW,SCSI]
1836 See header of drivers/scsi/pas16.c.
1838 pause_on_oops=
1839 Halt all CPUs after the first oops has been printed for
1840 the specified number of seconds. This is to be used if
1841 your oopses keep scrolling off the screen.
1843 pcbit= [HW,ISDN]
1845 pcd. [PARIDE]
1846 See header of drivers/block/paride/pcd.c.
1847 See also Documentation/blockdev/paride.txt.
1849 pci=option[,option...] [PCI] various PCI subsystem options:
1850 earlydump [X86] dump PCI config space before the kernel
1851 changes anything
1852 off [X86] don't probe for the PCI bus
1853 bios [X86-32] force use of PCI BIOS, don't access
1854 the hardware directly. Use this if your machine
1855 has a non-standard PCI host bridge.
1856 nobios [X86-32] disallow use of PCI BIOS, only direct
1857 hardware access methods are allowed. Use this
1858 if you experience crashes upon bootup and you
1859 suspect they are caused by the BIOS.
1860 conf1 [X86] Force use of PCI Configuration
1861 Mechanism 1.
1862 conf2 [X86] Force use of PCI Configuration
1863 Mechanism 2.
1864 noaer [PCIE] If the PCIEAER kernel config parameter is
1865 enabled, this kernel boot option can be used to
1866 disable the use of PCIE advanced error reporting.
1867 nodomains [PCI] Disable support for multiple PCI
1868 root domains (aka PCI segments, in ACPI-speak).
1869 nommconf [X86] Disable use of MMCONFIG for PCI
1870 Configuration
1871 check_enable_amd_mmconf [X86] check for and enable
1872 properly configured MMIO access to PCI
1873 config space on AMD family 10h CPU
1874 nomsi [MSI] If the PCI_MSI kernel config parameter is
1875 enabled, this kernel boot option can be used to
1876 disable the use of MSI interrupts system-wide.
1877 noioapicquirk [APIC] Disable all boot interrupt quirks.
1878 Safety option to keep boot IRQs enabled. This
1879 should never be necessary.
1880 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1881 primary IO-APIC for bridges that cannot disable
1882 boot IRQs. This fixes a source of spurious IRQs
1883 when the system masks IRQs.
1884 noioapicreroute [APIC] Disable workaround that uses the
1885 boot IRQ equivalent of an IRQ that connects to
1886 a chipset where boot IRQs cannot be disabled.
1887 The opposite of ioapicreroute.
1888 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1889 routing table. These calls are known to be buggy
1890 on several machines and they hang the machine
1891 when used, but on other computers it's the only
1892 way to get the interrupt routing table. Try
1893 this option if the kernel is unable to allocate
1894 IRQs or discover secondary PCI buses on your
1895 motherboard.
1896 rom [X86] Assign address space to expansion ROMs.
1897 Use with caution as certain devices share
1898 address decoders between ROMs and other
1899 resources.
1900 norom [X86] Do not assign address space to
1901 expansion ROMs that do not already have
1902 BIOS assigned address ranges.
1903 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1904 assigned automatically to PCI devices. You can
1905 make the kernel exclude IRQs of your ISA cards
1906 this way.
1907 pirqaddr=0xAAAAA [X86] Specify the physical address
1908 of the PIRQ table (normally generated
1909 by the BIOS) if it is outside the
1910 F0000h-100000h range.
1911 lastbus=N [X86] Scan all buses thru bus #N. Can be
1912 useful if the kernel is unable to find your
1913 secondary buses and you want to tell it
1914 explicitly which ones they are.
1915 assign-busses [X86] Always assign all PCI bus
1916 numbers ourselves, overriding
1917 whatever the firmware may have done.
1918 usepirqmask [X86] Honor the possible IRQ mask stored
1919 in the BIOS $PIR table. This is needed on
1920 some systems with broken BIOSes, notably
1921 some HP Pavilion N5400 and Omnibook XE3
1922 notebooks. This will have no effect if ACPI
1923 IRQ routing is enabled.
1924 noacpi [X86] Do not use ACPI for IRQ routing
1925 or for PCI scanning.
1926 use_crs [X86] Use _CRS for PCI resource
1927 allocation.
1928 routeirq Do IRQ routing for all PCI devices.
1929 This is normally done in pci_enable_device(),
1930 so this option is a temporary workaround
1931 for broken drivers that don't call it.
1932 skip_isa_align [X86] do not align io start addr, so can
1933 handle more pci cards
1934 firmware [ARM] Do not re-enumerate the bus but instead
1935 just use the configuration from the
1936 bootloader. This is currently used on
1937 IXP2000 systems where the bus has to be
1938 configured a certain way for adjunct CPUs.
1939 noearly [X86] Don't do any early type 1 scanning.
1940 This might help on some broken boards which
1941 machine check when some devices' config space
1942 is read. But various workarounds are disabled
1943 and some IOMMU drivers will not work.
1944 bfsort Sort PCI devices into breadth-first order.
1945 This sorting is done to get a device
1946 order compatible with older (<= 2.4) kernels.
1947 nobfsort Don't sort PCI devices into breadth-first order.
1948 cbiosize=nn[KMG] The fixed amount of bus space which is
1949 reserved for the CardBus bridge's IO window.
1950 The default value is 256 bytes.
1951 cbmemsize=nn[KMG] The fixed amount of bus space which is
1952 reserved for the CardBus bridge's memory
1953 window. The default value is 64 megabytes.
1954 resource_alignment=
1955 Format:
1956 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1957 Specifies alignment and device to reassign
1958 aligned memory resources.
1959 If <order of align> is not specified,
1960 PAGE_SIZE is used as alignment.
1961 PCI-PCI bridge can be specified, if resource
1962 windows need to be expanded.
1963 ecrc= Enable/disable PCIe ECRC (transaction layer
1964 end-to-end CRC checking).
1965 bios: Use BIOS/firmware settings. This is the
1966 the default.
1967 off: Turn ECRC off
1968 on: Turn ECRC on.
1970 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1971 Management.
1972 off Disable ASPM.
1973 force Enable ASPM even on devices that claim not to support it.
1974 WARNING: Forcing ASPM on may cause system lockups.
1976 pcmv= [HW,PCMCIA] BadgePAD 4
1978 pd. [PARIDE]
1979 See Documentation/blockdev/paride.txt.
1981 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1982 boot time.
1983 Format: { 0 | 1 }
1984 See arch/parisc/kernel/pdc_chassis.c
1986 percpu_alloc= Select which percpu first chunk allocator to use.
1987 Currently supported values are "embed" and "page".
1988 Archs may support subset or none of the selections.
1989 See comments in mm/percpu.c for details on each
1990 allocator. This parameter is primarily for debugging
1991 and performance comparison.
1993 pf. [PARIDE]
1994 See Documentation/blockdev/paride.txt.
1996 pg. [PARIDE]
1997 See Documentation/blockdev/paride.txt.
1999 pirq= [SMP,APIC] Manual mp-table setup
2000 See Documentation/x86/i386/IO-APIC.txt.
2002 plip= [PPT,NET] Parallel port network link
2003 Format: { parport<nr> | timid | 0 }
2004 See also Documentation/parport.txt.
2006 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2007 Override pmtimer IOPort with a hex value.
2008 e.g. pmtmr=0x508
2010 pnp.debug [PNP]
2011 Enable PNP debug messages. This depends on the
2012 CONFIG_PNP_DEBUG_MESSAGES option.
2014 pnpacpi= [ACPI]
2015 { off }
2017 pnpbios= [ISAPNP]
2018 { on | off | curr | res | no-curr | no-res }
2020 pnp_reserve_irq=
2021 [ISAPNP] Exclude IRQs for the autoconfiguration
2023 pnp_reserve_dma=
2024 [ISAPNP] Exclude DMAs for the autoconfiguration
2026 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2027 Ranges are in pairs (I/O port base and size).
2029 pnp_reserve_mem=
2030 [ISAPNP] Exclude memory regions for the
2031 autoconfiguration.
2032 Ranges are in pairs (memory base and size).
2034 ports= [IP_VS_FTP] IPVS ftp helper module
2035 Default is 21.
2036 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2037 may be specified.
2038 Format: <port>,<port>....
2040 print-fatal-signals=
2041 [KNL] debug: print fatal signals
2042 print-fatal-signals=1: print segfault info to
2043 the kernel console.
2044 default: off.
2046 printk.time= Show timing data prefixed to each printk message line
2047 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2049 processor.max_cstate= [HW,ACPI]
2050 Limit processor to maximum C-state
2051 max_cstate=9 overrides any DMI blacklist limit.
2053 processor.nocst [HW,ACPI]
2054 Ignore the _CST method to determine C-states,
2055 instead using the legacy FADT method
2057 profile= [KNL] Enable kernel profiling via /proc/profile
2058 Format: [schedule,]<number>
2059 Param: "schedule" - profile schedule points.
2060 Param: <number> - step/bucket size as a power of 2 for
2061 statistical time based profiling.
2062 Param: "sleep" - profile D-state sleeping (millisecs).
2063 Requires CONFIG_SCHEDSTATS
2064 Param: "kvm" - profile VM exits.
2066 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2067 before loading.
2068 See Documentation/blockdev/ramdisk.txt.
2070 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2071 probe for; one of (bare|imps|exps|lifebook|any).
2072 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2073 per second.
2074 psmouse.resetafter= [HW,MOUSE]
2075 Try to reset the device after so many bad packets
2076 (0 = never).
2077 psmouse.resolution=
2078 [HW,MOUSE] Set desired mouse resolution, in dpi.
2079 psmouse.smartscroll=
2080 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2081 0 = disabled, 1 = enabled (default).
2083 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2084 Format:
2085 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2087 pt. [PARIDE]
2088 See Documentation/blockdev/paride.txt.
2090 pty.legacy_count=
2091 [KNL] Number of legacy pty's. Overwrites compiled-in
2092 default number.
2094 quiet [KNL] Disable most log messages
2096 r128= [HW,DRM]
2098 raid= [HW,RAID]
2099 See Documentation/md.txt.
2101 ramdisk_blocksize= [RAM]
2102 See Documentation/blockdev/ramdisk.txt.
2104 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2105 See Documentation/blockdev/ramdisk.txt.
2107 rcupdate.blimit= [KNL,BOOT]
2108 Set maximum number of finished RCU callbacks to process
2109 in one batch.
2111 rcupdate.qhimark= [KNL,BOOT]
2112 Set threshold of queued
2113 RCU callbacks over which batch limiting is disabled.
2115 rcupdate.qlowmark= [KNL,BOOT]
2116 Set threshold of queued RCU callbacks below which
2117 batch limiting is re-enabled.
2119 rdinit= [KNL]
2120 Format: <full_path>
2121 Run specified binary instead of /init from the ramdisk,
2122 used for early userspace startup. See initrd.
2124 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2125 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2126 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2128 relax_domain_level=
2129 [KNL, SMP] Set scheduler's default relax_domain_level.
2130 See Documentation/cgroups/cpusets.txt.
2132 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2134 reservetop= [X86-32]
2135 Format: nn[KMG]
2136 Reserves a hole at the top of the kernel virtual
2137 address space.
2139 reset_devices [KNL] Force drivers to reset the underlying device
2140 during initialization.
2142 resume= [SWSUSP]
2143 Specify the partition device for software suspend
2145 resume_offset= [SWSUSP]
2146 Specify the offset from the beginning of the partition
2147 given by "resume=" at which the swap header is located,
2148 in <PAGE_SIZE> units (needed only for swap files).
2149 See Documentation/power/swsusp-and-swap-files.txt
2151 retain_initrd [RAM] Keep initrd memory after extraction
2153 rhash_entries= [KNL,NET]
2154 Set number of hash buckets for route cache
2156 riscom8= [HW,SERIAL]
2157 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2159 ro [KNL] Mount root device read-only on boot
2161 root= [KNL] Root filesystem
2163 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2164 mount the root filesystem
2166 rootflags= [KNL] Set root filesystem mount option string
2168 rootfstype= [KNL] Set root filesystem type
2170 rootwait [KNL] Wait (indefinitely) for root device to show up.
2171 Useful for devices that are detected asynchronously
2172 (e.g. USB and MMC devices).
2174 root_plug.vendor_id=
2175 [ROOTPLUG] Override the default vendor ID
2177 root_plug.product_id=
2178 [ROOTPLUG] Override the default product ID
2180 root_plug.debug=
2181 [ROOTPLUG] Enable debugging output
2183 rw [KNL] Mount root device read-write on boot
2185 S [KNL] Run init in single mode
2187 sa1100ir [NET]
2188 See drivers/net/irda/sa1100_ir.c.
2190 sbni= [NET] Granch SBNI12 leased line adapter
2192 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2193 Format: <io>[,<timeout>[,<isapnp>]]
2195 scsi_debug_*= [SCSI]
2196 See drivers/scsi/scsi_debug.c.
2198 scsi_default_dev_flags=
2199 [SCSI] SCSI default device flags
2200 Format: <integer>
2202 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2203 Format: <vendor>:<model>:<flags>
2204 (flags are integer value)
2206 scsi_logging_level= [SCSI] a bit mask of logging levels
2207 See drivers/scsi/scsi_logging.h for bits. Also
2208 settable via sysctl at dev.scsi.logging_level
2209 (/proc/sys/dev/scsi/logging_level).
2210 There is also a nice 'scsi_logging_level' script in the
2211 S390-tools package, available for download at
2212 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2214 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2215 discovered. async scans them in kernel threads,
2216 allowing boot to proceed. none ignores them, expecting
2217 user space to do the scan.
2219 security= [SECURITY] Choose a security module to enable at boot.
2220 If this boot parameter is not specified, only the first
2221 security module asking for security registration will be
2222 loaded. An invalid security module name will be treated
2223 as if no module has been chosen.
2225 selinux= [SELINUX] Disable or enable SELinux at boot time.
2226 Format: { "0" | "1" }
2227 See security/selinux/Kconfig help text.
2228 0 -- disable.
2229 1 -- enable.
2230 Default value is set via kernel config option.
2231 If enabled at boot time, /selinux/disable can be used
2232 later to disable prior to initial policy load.
2234 serialnumber [BUGS=X86-32]
2236 shapers= [NET]
2237 Maximal number of shapers.
2239 show_msr= [x86] show boot-time MSR settings
2240 Format: { <integer> }
2241 Show boot-time (BIOS-initialized) MSR settings.
2242 The parameter means the number of CPUs to show,
2243 for example 1 means boot CPU only.
2245 sim710= [SCSI,HW]
2246 See header of drivers/scsi/sim710.c.
2248 simeth= [IA-64]
2249 simscsi=
2251 slram= [HW,MTD]
2253 slub_debug[=options[,slabs]] [MM, SLUB]
2254 Enabling slub_debug allows one to determine the
2255 culprit if slab objects become corrupted. Enabling
2256 slub_debug can create guard zones around objects and
2257 may poison objects when not in use. Also tracks the
2258 last alloc / free. For more information see
2259 Documentation/vm/slub.txt.
2261 slub_max_order= [MM, SLUB]
2262 Determines the maximum allowed order for slabs.
2263 A high setting may cause OOMs due to memory
2264 fragmentation. For more information see
2265 Documentation/vm/slub.txt.
2267 slub_min_objects= [MM, SLUB]
2268 The minimum number of objects per slab. SLUB will
2269 increase the slab order up to slub_max_order to
2270 generate a sufficiently large slab able to contain
2271 the number of objects indicated. The higher the number
2272 of objects the smaller the overhead of tracking slabs
2273 and the less frequently locks need to be acquired.
2274 For more information see Documentation/vm/slub.txt.
2276 slub_min_order= [MM, SLUB]
2277 Determines the mininum page order for slabs. Must be
2278 lower than slub_max_order.
2279 For more information see Documentation/vm/slub.txt.
2281 slub_nomerge [MM, SLUB]
2282 Disable merging of slabs with similar size. May be
2283 necessary if there is some reason to distinguish
2284 allocs to different slabs. Debug options disable
2285 merging on their own.
2286 For more information see Documentation/vm/slub.txt.
2288 smart2= [HW]
2289 Format: <io1>[,<io2>[,...,<io8>]]
2291 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2292 attempt to substitute SMP alternatives once at boot.
2294 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2295 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2296 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2297 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2298 smsc-ircc2.ircc_irq= [HW] IRQ line
2299 smsc-ircc2.ircc_dma= [HW] DMA channel
2300 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2301 0: Toshiba Satellite 1800 (GP data pin select)
2302 1: Fast pin select (default)
2303 2: ATC IRMode
2305 snd-ad1816a= [HW,ALSA]
2307 snd-ad1848= [HW,ALSA]
2309 snd-ali5451= [HW,ALSA]
2311 snd-als100= [HW,ALSA]
2313 snd-als4000= [HW,ALSA]
2315 snd-azt2320= [HW,ALSA]
2317 snd-cmi8330= [HW,ALSA]
2319 snd-cmipci= [HW,ALSA]
2321 snd-cs4231= [HW,ALSA]
2323 snd-cs4232= [HW,ALSA]
2325 snd-cs4236= [HW,ALSA]
2327 snd-cs4281= [HW,ALSA]
2329 snd-cs46xx= [HW,ALSA]
2331 snd-dt019x= [HW,ALSA]
2333 snd-dummy= [HW,ALSA]
2335 snd-emu10k1= [HW,ALSA]
2337 snd-ens1370= [HW,ALSA]
2339 snd-ens1371= [HW,ALSA]
2341 snd-es968= [HW,ALSA]
2343 snd-es1688= [HW,ALSA]
2345 snd-es18xx= [HW,ALSA]
2347 snd-es1938= [HW,ALSA]
2349 snd-es1968= [HW,ALSA]
2351 snd-fm801= [HW,ALSA]
2353 snd-gusclassic= [HW,ALSA]
2355 snd-gusextreme= [HW,ALSA]
2357 snd-gusmax= [HW,ALSA]
2359 snd-hdsp= [HW,ALSA]
2361 snd-ice1712= [HW,ALSA]
2363 snd-intel8x0= [HW,ALSA]
2365 snd-interwave= [HW,ALSA]
2367 snd-interwave-stb=
2368 [HW,ALSA]
2370 snd-korg1212= [HW,ALSA]
2372 snd-maestro3= [HW,ALSA]
2374 snd-mpu401= [HW,ALSA]
2376 snd-mtpav= [HW,ALSA]
2378 snd-nm256= [HW,ALSA]
2380 snd-opl3sa2= [HW,ALSA]
2382 snd-opti92x-ad1848=
2383 [HW,ALSA]
2385 snd-opti92x-cs4231=
2386 [HW,ALSA]
2388 snd-opti93x= [HW,ALSA]
2390 snd-pmac= [HW,ALSA]
2392 snd-rme32= [HW,ALSA]
2394 snd-rme96= [HW,ALSA]
2396 snd-rme9652= [HW,ALSA]
2398 snd-sb8= [HW,ALSA]
2400 snd-sb16= [HW,ALSA]
2402 snd-sbawe= [HW,ALSA]
2404 snd-serial= [HW,ALSA]
2406 snd-sgalaxy= [HW,ALSA]
2408 snd-sonicvibes= [HW,ALSA]
2410 snd-sun-amd7930=
2411 [HW,ALSA]
2413 snd-sun-cs4231= [HW,ALSA]
2415 snd-trident= [HW,ALSA]
2417 snd-usb-audio= [HW,ALSA,USB]
2419 snd-via82xx= [HW,ALSA]
2421 snd-virmidi= [HW,ALSA]
2423 snd-wavefront= [HW,ALSA]
2425 snd-ymfpci= [HW,ALSA]
2427 softlockup_panic=
2428 [KNL] Should the soft-lockup detector generate panics.
2430 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2431 See Documentation/sonypi.txt
2433 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2434 See Documentation/serial/specialix.txt.
2436 spia_io_base= [HW,MTD]
2437 spia_fio_base=
2438 spia_pedr=
2439 spia_peddr=
2441 sscape= [HW,OSS]
2442 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2444 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2445 See Documentation/scsi/st.txt.
2447 stacktrace [FTRACE]
2448 Enabled the stack tracer on boot up.
2450 sti= [PARISC,HW]
2451 Format: <num>
2452 Set the STI (builtin display/keyboard on the HP-PARISC
2453 machines) console (graphic card) which should be used
2454 as the initial boot-console.
2455 See also comment in drivers/video/console/sticore.c.
2457 sti_font= [HW]
2458 See comment in drivers/video/console/sticore.c.
2460 stifb= [HW]
2461 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2463 sunrpc.min_resvport=
2464 sunrpc.max_resvport=
2465 [NFS,SUNRPC]
2466 SunRPC servers often require that client requests
2467 originate from a privileged port (i.e. a port in the
2468 range 0 < portnr < 1024).
2469 An administrator who wishes to reserve some of these
2470 ports for other uses may adjust the range that the
2471 kernel's sunrpc client considers to be privileged
2472 using these two parameters to set the minimum and
2473 maximum port values.
2475 sunrpc.pool_mode=
2476 [NFS]
2477 Control how the NFS server code allocates CPUs to
2478 service thread pools. Depending on how many NICs
2479 you have and where their interrupts are bound, this
2480 option will affect which CPUs will do NFS serving.
2481 Note: this parameter cannot be changed while the
2482 NFS server is running.
2484 auto the server chooses an appropriate mode
2485 automatically using heuristics
2486 global a single global pool contains all CPUs
2487 percpu one pool for each CPU
2488 pernode one pool for each NUMA node (equivalent
2489 to global on non-NUMA machines)
2491 sunrpc.tcp_slot_table_entries=
2492 sunrpc.udp_slot_table_entries=
2493 [NFS,SUNRPC]
2494 Sets the upper limit on the number of simultaneous
2495 RPC calls that can be sent from the client to a
2496 server. Increasing these values may allow you to
2497 improve throughput, but will also increase the
2498 amount of memory reserved for use by the client.
2500 swiotlb= [IA-64] Number of I/O TLB slabs
2502 switches= [HW,M68k]
2504 sym53c416= [HW,SCSI]
2505 See header of drivers/scsi/sym53c416.c.
2507 sysrq_always_enabled
2508 [KNL]
2509 Ignore sysrq setting - this boot parameter will
2510 neutralize any effect of /proc/sys/kernel/sysrq.
2511 Useful for debugging.
2513 t128= [HW,SCSI]
2514 See header of drivers/scsi/t128.c.
2516 tdfx= [HW,DRM]
2518 test_suspend= [SUSPEND]
2519 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2520 standby suspend) as the system sleep state to briefly
2521 enter during system startup. The system is woken from
2522 this state using a wakeup-capable RTC alarm.
2524 thash_entries= [KNL,NET]
2525 Set number of hash buckets for TCP connection
2527 thermal.act= [HW,ACPI]
2528 -1: disable all active trip points in all thermal zones
2529 <degrees C>: override all lowest active trip points
2531 thermal.crt= [HW,ACPI]
2532 -1: disable all critical trip points in all thermal zones
2533 <degrees C>: override all critical trip points
2535 thermal.nocrt= [HW,ACPI]
2536 Set to disable actions on ACPI thermal zone
2537 critical and hot trip points.
2539 thermal.off= [HW,ACPI]
2540 1: disable ACPI thermal control
2542 thermal.psv= [HW,ACPI]
2543 -1: disable all passive trip points
2544 <degrees C>: override all passive trip points to this
2545 value
2547 thermal.tzp= [HW,ACPI]
2548 Specify global default ACPI thermal zone polling rate
2549 <deci-seconds>: poll all this frequency
2550 0: no polling (default)
2552 tmscsim= [HW,SCSI]
2553 See comment before function dc390_setup() in
2554 drivers/scsi/tmscsim.c.
2556 topology= [S390]
2557 Format: {off | on}
2558 Specify if the kernel should make use of the cpu
2559 topology informations if the hardware supports these.
2560 The scheduler will make use of these informations and
2561 e.g. base its process migration decisions on it.
2562 Default is off.
2564 tp720= [HW,PS2]
2566 trace_buf_size=nn[KMG]
2567 [FTRACE] will set tracing buffer size.
2569 trace_event=[event-list]
2570 [FTRACE] Set and start specified trace events in order
2571 to facilitate early boot debugging.
2572 See also Documentation/trace/events.txt
2574 trix= [HW,OSS] MediaTrix AudioTrix Pro
2575 Format:
2576 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2578 tsc= Disable clocksource-must-verify flag for TSC.
2579 Format: <string>
2580 [x86] reliable: mark tsc clocksource as reliable, this
2581 disables clocksource verification at runtime.
2582 Used to enable high-resolution timer mode on older
2583 hardware, and in virtualized environment.
2585 turbografx.map[2|3]= [HW,JOY]
2586 TurboGraFX parallel port interface
2587 Format:
2588 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2589 See also Documentation/input/joystick-parport.txt
2591 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2592 See header of drivers/scsi/u14-34f.c.
2594 uart401= [HW,OSS]
2595 Format: <io>,<irq>
2597 uart6850= [HW,OSS]
2598 Format: <io>,<irq>
2600 uhci-hcd.ignore_oc=
2601 [USB] Ignore overcurrent events (default N).
2602 Some badly-designed motherboards generate lots of
2603 bogus events, for ports that aren't wired to
2604 anything. Set this parameter to avoid log spamming.
2605 Note that genuine overcurrent events won't be
2606 reported either.
2608 unknown_nmi_panic
2609 [X86]
2610 Set unknown_nmi_panic=1 early on boot.
2612 usbcore.autosuspend=
2613 [USB] The autosuspend time delay (in seconds) used
2614 for newly-detected USB devices (default 2). This
2615 is the time required before an idle device will be
2616 autosuspended. Devices for which the delay is set
2617 to a negative value won't be autosuspended at all.
2619 usbcore.usbfs_snoop=
2620 [USB] Set to log all usbfs traffic (default 0 = off).
2622 usbcore.blinkenlights=
2623 [USB] Set to cycle leds on hubs (default 0 = off).
2625 usbcore.old_scheme_first=
2626 [USB] Start with the old device initialization
2627 scheme (default 0 = off).
2629 usbcore.use_both_schemes=
2630 [USB] Try the other device initialization scheme
2631 if the first one fails (default 1 = enabled).
2633 usbcore.initial_descriptor_timeout=
2634 [USB] Specifies timeout for the initial 64-byte
2635 USB_REQ_GET_DESCRIPTOR request in milliseconds
2636 (default 5000 = 5.0 seconds).
2638 usbhid.mousepoll=
2639 [USBHID] The interval which mice are to be polled at.
2641 usb-storage.delay_use=
2642 [UMS] The delay in seconds before a new device is
2643 scanned for Logical Units (default 5).
2645 usb-storage.quirks=
2646 [UMS] A list of quirks entries to supplement or
2647 override the built-in unusual_devs list. List
2648 entries are separated by commas. Each entry has
2649 the form VID:PID:Flags where VID and PID are Vendor
2650 and Product ID values (4-digit hex numbers) and
2651 Flags is a set of characters, each corresponding
2652 to a common usb-storage quirk flag as follows:
2653 a = SANE_SENSE (collect more than 18 bytes
2654 of sense data);
2655 c = FIX_CAPACITY (decrease the reported
2656 device capacity by one sector);
2657 h = CAPACITY_HEURISTICS (decrease the
2658 reported device capacity by one
2659 sector if the number is odd);
2660 i = IGNORE_DEVICE (don't bind to this
2661 device);
2662 l = NOT_LOCKABLE (don't try to lock and
2663 unlock ejectable media);
2664 m = MAX_SECTORS_64 (don't transfer more
2665 than 64 sectors = 32 KB at a time);
2666 o = CAPACITY_OK (accept the capacity
2667 reported by the device);
2668 r = IGNORE_RESIDUE (the device reports
2669 bogus residue values);
2670 s = SINGLE_LUN (the device has only one
2671 Logical Unit);
2672 w = NO_WP_DETECT (don't test whether the
2673 medium is write-protected).
2674 Example: quirks=0419:aaf5:rl,0421:0433:rc
2676 vdso= [X86,SH]
2677 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2678 vdso=1: enable VDSO (default)
2679 vdso=0: disable VDSO mapping
2681 vdso32= [X86]
2682 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2683 vdso32=1: enable 32-bit VDSO (default)
2684 vdso32=0: disable 32-bit VDSO mapping
2686 vector= [IA-64,SMP]
2687 vector=percpu: enable percpu vector domain
2689 video= [FB] Frame buffer configuration
2690 See Documentation/fb/modedb.txt.
2692 vga= [BOOT,X86-32] Select a particular video mode
2693 See Documentation/x86/boot.txt and
2694 Documentation/svga.txt.
2695 Use vga=ask for menu.
2696 This is actually a boot loader parameter; the value is
2697 passed to the kernel using a special protocol.
2699 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2700 size of <nn>. This can be used to increase the
2701 minimum size (128MB on x86). It can also be used to
2702 decrease the size and leave more room for directly
2703 mapped kernel RAM.
2705 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2706 Format: <command>
2708 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2709 Format: <command>
2711 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2712 Format: <command>
2714 vt.default_blu= [VT]
2715 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2716 Change the default blue palette of the console.
2717 This is a 16-member array composed of values
2718 ranging from 0-255.
2720 vt.default_grn= [VT]
2721 Format: <green0>,<green1>,<green2>,...,<green15>
2722 Change the default green palette of the console.
2723 This is a 16-member array composed of values
2724 ranging from 0-255.
2726 vt.default_red= [VT]
2727 Format: <red0>,<red1>,<red2>,...,<red15>
2728 Change the default red palette of the console.
2729 This is a 16-member array composed of values
2730 ranging from 0-255.
2732 vt.default_utf8=
2733 [VT]
2734 Format=<0|1>
2735 Set system-wide default UTF-8 mode for all tty's.
2736 Default is 1, i.e. UTF-8 mode is enabled for all
2737 newly opened terminals.
2739 waveartist= [HW,OSS]
2740 Format: <io>,<irq>,<dma>,<dma2>
2742 wd33c93= [HW,SCSI]
2743 See header of drivers/scsi/wd33c93.c.
2745 wd7000= [HW,SCSI]
2746 See header of drivers/scsi/wd7000.c.
2748 wdt= [WDT] Watchdog
2749 See Documentation/watchdog/wdt.txt.
2751 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2752 default x2apic cluster mode on platforms
2753 supporting x2apic.
2755 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2756 xd_geo= See header of drivers/block/xd.c.
2758 xirc2ps_cs= [NET,PCMCIA]
2759 Format:
2760 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2762 ______________________________________________________________________
2764 TODO:
2766 Add documentation for ALSA options.
2767 Add more DRM drivers.