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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 gamecon.map[2|3]=
783 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
784 support via parallel port (up to 5 devices per port)
785 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
786 See also Documentation/input/joystick-parport.txt
788 gamma= [HW,DRM]
790 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
791 Format: off | on
792 default: on
794 gcov_persist= [GCOV] When non-zero (default), profiling data for
795 kernel modules is saved and remains accessible via
796 debugfs, even when the module is unloaded/reloaded.
797 When zero, profiling data is discarded and associated
798 debugfs files are removed at module unload time.
800 gdth= [HW,SCSI]
801 See header of drivers/scsi/gdth.c.
803 gpt [EFI] Forces disk with valid GPT signature but
804 invalid Protective MBR to be treated as GPT.
806 gvp11= [HW,SCSI]
808 hashdist= [KNL,NUMA] Large hashes allocated during boot
809 are distributed across NUMA nodes. Defaults on
810 for 64bit NUMA, off otherwise.
811 Format: 0 | 1 (for off | on)
813 hcl= [IA-64] SGI's Hardware Graph compatibility layer
815 hd= [EIDE] (E)IDE hard drive subsystem geometry
816 Format: <cyl>,<head>,<sect>
818 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
819 size of <nn>. This works even on boxes that have no
820 highmem otherwise. This also works to reduce highmem
821 size on bigger boxes.
823 highres= [KNL] Enable/disable high resolution timer mode.
824 Valid parameters: "on", "off"
825 Default: "on"
827 hisax= [HW,ISDN]
828 See Documentation/isdn/README.HiSax.
830 hlt [BUGS=ARM,SH]
832 hpet= [X86-32,HPET] option to control HPET usage
833 Format: { enable (default) | disable | force |
834 verbose }
835 disable: disable HPET and use PIT instead
836 force: allow force enabled of undocumented chips (ICH4,
837 VIA, nVidia)
838 verbose: show contents of HPET registers during setup
840 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
841 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
842 On x86-64 and powerpc, this option can be specified
843 multiple times interleaved with hugepages= to reserve
844 huge pages of different sizes. Valid pages sizes on
845 x86-64 are 2M (when the CPU supports "pse") and 1G
846 (when the CPU supports the "pdpe1gb" cpuinfo flag)
847 Note that 1GB pages can only be allocated at boot time
848 using hugepages= and not freed afterwards.
850 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
851 terminal devices. Valid values: 0..8
852 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
853 If specified, z/VM IUCV HVC accepts connections
854 from listed z/VM user IDs only.
856 i2c_bus= [HW] Override the default board specific I2C bus speed
857 or register an additional I2C bus that is not
858 registered from board initialization code.
859 Format:
860 <bus_id>,<clkrate>
862 i8042.debug [HW] Toggle i8042 debug mode
863 i8042.direct [HW] Put keyboard port into non-translated mode
864 i8042.dumbkbd [HW] Pretend that controller can only read data from
865 keyboard and cannot control its state
866 (Don't attempt to blink the leds)
867 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
868 i8042.nokbd [HW] Don't check/create keyboard port
869 i8042.noloop [HW] Disable the AUX Loopback command while probing
870 for the AUX port
871 i8042.nomux [HW] Don't check presence of an active multiplexing
872 controller
873 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
874 controllers
875 i8042.panicblink=
876 [HW] Frequency with which keyboard LEDs should blink
877 when kernel panics (default is 0.5 sec)
878 i8042.reset [HW] Reset the controller during init and cleanup
879 i8042.unlock [HW] Unlock (ignore) the keylock
881 i810= [HW,DRM]
883 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
884 indicates that the driver is running on unsupported
885 hardware.
886 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
887 does not match list of supported models.
888 i8k.power_status
889 [HW] Report power status in /proc/i8k
890 (disabled by default)
891 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
892 capability is set.
894 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
895 See Documentation/mca.txt.
897 icn= [HW,ISDN]
898 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
900 ide-core.nodma= [HW] (E)IDE subsystem
901 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
902 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
903 .cdrom .chs .ignore_cable are additional options
904 See Documentation/ide/ide.txt.
906 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
907 Claim all unknown PCI IDE storage controllers.
909 idle= [X86]
910 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
911 Poll forces a polling idle loop that can slightly
912 improve the performance of waking up a idle CPU, but
913 will use a lot of power and make the system run hot.
914 Not recommended.
915 idle=mwait: On systems which support MONITOR/MWAIT but
916 the kernel chose to not use it because it doesn't save
917 as much power as a normal idle loop, use the
918 MONITOR/MWAIT idle loop anyways. Performance should be
919 the same as idle=poll.
920 idle=halt: Halt is forced to be used for CPU idle.
921 In such case C2/C3 won't be used again.
922 idle=nomwait: Disable mwait for CPU C-states
924 ignore_loglevel [KNL]
925 Ignore loglevel setting - this will print /all/
926 kernel messages to the console. Useful for debugging.
928 ihash_entries= [KNL]
929 Set number of hash buckets for inode cache.
931 ima_audit= [IMA]
932 Format: { "0" | "1" }
933 0 -- integrity auditing messages. (Default)
934 1 -- enable informational integrity auditing messages.
936 ima_hash= [IMA]
937 Format: { "sha1" | "md5" }
938 default: "sha1"
940 ima_tcb [IMA]
941 Load a policy which meets the needs of the Trusted
942 Computing Base. This means IMA will measure all
943 programs exec'd, files mmap'd for exec, and all files
944 opened for read by uid=0.
946 in2000= [HW,SCSI]
947 See header of drivers/scsi/in2000.c.
949 init= [KNL]
950 Format: <full_path>
951 Run specified binary instead of /sbin/init as init
952 process.
954 initcall_debug [KNL] Trace initcalls as they are executed. Useful
955 for working out where the kernel is dying during
956 startup.
958 initrd= [BOOT] Specify the location of the initial ramdisk
960 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
961 Format: <irq>
963 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
964 on
965 Enable intel iommu driver.
966 off
967 Disable intel iommu driver.
968 igfx_off [Default Off]
969 By default, gfx is mapped as normal device. If a gfx
970 device has a dedicated DMAR unit, the DMAR unit is
971 bypassed by not enabling DMAR with this option. In
972 this case, gfx device will use physical address for
973 DMA.
974 forcedac [x86_64]
975 With this option iommu will not optimize to look
976 for io virtual address below 32 bit forcing dual
977 address cycle on pci bus for cards supporting greater
978 than 32 bit addressing. The default is to look
979 for translation below 32 bit and if not available
980 then look in the higher range.
981 strict [Default Off]
982 With this option on every unmap_single operation will
983 result in a hardware IOTLB flush operation as opposed
984 to batching them for performance.
986 inttest= [IA64]
988 iomem= Disable strict checking of access to MMIO memory
989 strict regions from userspace.
990 relaxed
992 iommu= [x86]
993 off
994 force
995 noforce
996 biomerge
997 panic
998 nopanic
999 merge
1000 nomerge
1001 forcesac
1002 soft
1003 pt [x86, IA64]
1005 io7= [HW] IO7 for Marvel based alpha systems
1006 See comment before marvel_specify_io7 in
1007 arch/alpha/kernel/core_marvel.c.
1009 io_delay= [X86] I/O delay method
1010 0x80
1011 Standard port 0x80 based delay
1012 0xed
1013 Alternate port 0xed based delay (needed on some systems)
1014 udelay
1015 Simple two microseconds delay
1016 none
1017 No delay
1019 ip= [IP_PNP]
1020 See Documentation/filesystems/nfsroot.txt.
1022 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1023 See comment before ip2_setup() in
1024 drivers/char/ip2/ip2base.c.
1026 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1027 See header of drivers/scsi/ips.c.
1029 irqfixup [HW]
1030 When an interrupt is not handled search all handlers
1031 for it. Intended to get systems with badly broken
1032 firmware running.
1034 irqpoll [HW]
1035 When an interrupt is not handled search all handlers
1036 for it. Also check all handlers each timer
1037 interrupt. Intended to get systems with badly broken
1038 firmware running.
1040 isapnp= [ISAPNP]
1041 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1043 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1044 Format:
1045 <cpu number>,...,<cpu number>
1046 or
1047 <cpu number>-<cpu number>
1048 (must be a positive range in ascending order)
1049 or a mixture
1050 <cpu number>,...,<cpu number>-<cpu number>
1052 This option can be used to specify one or more CPUs
1053 to isolate from the general SMP balancing and scheduling
1054 algorithms. You can move a process onto or off an
1055 "isolated" CPU via the CPU affinity syscalls or cpuset.
1056 <cpu number> begins at 0 and the maximum value is
1057 "number of CPUs in system - 1".
1059 This option is the preferred way to isolate CPUs. The
1060 alternative -- manually setting the CPU mask of all
1061 tasks in the system -- can cause problems and
1062 suboptimal load balancer performance.
1064 iucv= [HW,NET]
1066 js= [HW,JOY] Analog joystick
1067 See Documentation/input/joystick.txt.
1069 keepinitrd [HW,ARM]
1071 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1072 specifies the amount of memory usable by the kernel
1073 for non-movable allocations. The requested amount is
1074 spread evenly throughout all nodes in the system. The
1075 remaining memory in each node is used for Movable
1076 pages. In the event, a node is too small to have both
1077 kernelcore and Movable pages, kernelcore pages will
1078 take priority and other nodes will have a larger number
1079 of kernelcore pages. The Movable zone is used for the
1080 allocation of pages that may be reclaimed or moved
1081 by the page migration subsystem. This means that
1082 HugeTLB pages may not be allocated from this zone.
1083 Note that allocations like PTEs-from-HighMem still
1084 use the HighMem zone if it exists, and the Normal
1085 zone if it does not.
1087 kgdboc= [HW] kgdb over consoles.
1088 Requires a tty driver that supports console polling.
1089 (only serial supported for now)
1090 Format: <serial_device>[,baud]
1092 kmac= [MIPS] korina ethernet MAC address.
1093 Configure the RouterBoard 532 series on-chip
1094 Ethernet adapter MAC address.
1096 kmemleak= [KNL] Boot-time kmemleak enable/disable
1097 Valid arguments: on, off
1098 Default: on
1100 kstack=N [X86] Print N words from the kernel stack
1101 in oops dumps.
1103 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1104 Default is 0 (don't ignore, but inject #GP)
1106 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1107 Default is 1 (enabled)
1109 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1110 Default is 0 (off)
1112 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1113 for all guests.
1114 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1116 kvm-intel.bypass_guest_pf=
1117 [KVM,Intel] Disables bypassing of guest page faults
1118 on Intel chips. Default is 1 (enabled)
1120 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1121 (virtualized MMU) support on capable Intel chips.
1122 Default is 1 (enabled)
1124 kvm-intel.emulate_invalid_guest_state=
1125 [KVM,Intel] Enable emulation of invalid guest states
1126 Default is 0 (disabled)
1128 kvm-intel.flexpriority=
1129 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1130 Default is 1 (enabled)
1132 kvm-intel.unrestricted_guest=
1133 [KVM,Intel] Disable unrestricted guest feature
1134 (virtualized real and unpaged mode) on capable
1135 Intel chips. Default is 1 (enabled)
1137 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1138 feature (tagged TLBs) on capable Intel chips.
1139 Default is 1 (enabled)
1141 l2cr= [PPC]
1143 l3cr= [PPC]
1145 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1146 disabled it.
1148 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1149 in C2 power state.
1151 libata.dma= [LIBATA] DMA control
1152 libata.dma=0 Disable all PATA and SATA DMA
1153 libata.dma=1 PATA and SATA Disk DMA only
1154 libata.dma=2 ATAPI (CDROM) DMA only
1155 libata.dma=4 Compact Flash DMA only
1156 Combinations also work, so libata.dma=3 enables DMA
1157 for disks and CDROMs, but not CFs.
1159 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1160 libata.ignore_hpa=0 keep BIOS limits (default)
1161 libata.ignore_hpa=1 ignore limits, using full disk
1163 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1164 when set.
1165 Format: <int>
1167 libata.force= [LIBATA] Force configurations. The format is comma
1168 separated list of "[ID:]VAL" where ID is
1169 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1170 matching port, link or device. Basically, it matches
1171 the ATA ID string printed on console by libata. If
1172 the whole ID part is omitted, the last PORT and DEVICE
1173 values are used. If ID hasn't been specified yet, the
1174 configuration applies to all ports, links and devices.
1176 If only DEVICE is omitted, the parameter applies to
1177 the port and all links and devices behind it. DEVICE
1178 number of 0 either selects the first device or the
1179 first fan-out link behind PMP device. It does not
1180 select the host link. DEVICE number of 15 selects the
1181 host link and device attached to it.
1183 The VAL specifies the configuration to force. As long
1184 as there's no ambiguity shortcut notation is allowed.
1185 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1186 The following configurations can be forced.
1188 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1189 Any ID with matching PORT is used.
1191 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1193 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1194 udma[/][16,25,33,44,66,100,133] notation is also
1195 allowed.
1197 * [no]ncq: Turn on or off NCQ.
1199 * nohrst, nosrst, norst: suppress hard, soft
1200 and both resets.
1202 If there are multiple matching configurations changing
1203 the same attribute, the last one is used.
1205 lmb=debug [KNL] Enable lmb debug messages.
1207 load_ramdisk= [RAM] List of ramdisks to load from floppy
1208 See Documentation/blockdev/ramdisk.txt.
1210 lockd.nlm_grace_period=P [NFS] Assign grace period.
1211 Format: <integer>
1213 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1214 Format: <integer>
1216 lockd.nlm_timeout=T [NFS] Assign timeout value.
1217 Format: <integer>
1219 lockd.nlm_udpport=M [NFS] Assign UDP port.
1220 Format: <integer>
1222 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1223 Format: <irq>
1225 loglevel= All Kernel Messages with a loglevel smaller than the
1226 console loglevel will be printed to the console. It can
1227 also be changed with klogd or other programs. The
1228 loglevels are defined as follows:
1230 0 (KERN_EMERG) system is unusable
1231 1 (KERN_ALERT) action must be taken immediately
1232 2 (KERN_CRIT) critical conditions
1233 3 (KERN_ERR) error conditions
1234 4 (KERN_WARNING) warning conditions
1235 5 (KERN_NOTICE) normal but significant condition
1236 6 (KERN_INFO) informational
1237 7 (KERN_DEBUG) debug-level messages
1239 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1240 Format: { n | nk | nM }
1241 n must be a power of two. The default size
1242 is set in the kernel config file.
1244 logo.nologo [FB] Disables display of the built-in Linux logo.
1245 This may be used to provide more screen space for
1246 kernel log messages and is useful when debugging
1247 kernel boot problems.
1249 lp=0 [LP] Specify parallel ports to use, e.g,
1250 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1251 lp=reset first parallel port). 'lp=0' disables the
1252 lp=auto printer driver. 'lp=reset' (which can be
1253 specified in addition to the ports) causes
1254 attached printers to be reset. Using
1255 lp=port1,port2,... specifies the parallel ports
1256 to associate lp devices with, starting with
1257 lp0. A port specification may be 'none' to skip
1258 that lp device, or a parport name such as
1259 'parport0'. Specifying 'lp=auto' instead of a
1260 port specification list means that device IDs
1261 from each port should be examined, to see if
1262 an IEEE 1284-compliant printer is attached; if
1263 so, the driver will manage that printer.
1264 See also header of drivers/char/lp.c.
1266 lpj=n [KNL]
1267 Sets loops_per_jiffy to given constant, thus avoiding
1268 time-consuming boot-time autodetection (up to 250 ms per
1269 CPU). 0 enables autodetection (default). To determine
1270 the correct value for your kernel, boot with normal
1271 autodetection and see what value is printed. Note that
1272 on SMP systems the preset will be applied to all CPUs,
1273 which is likely to cause problems if your CPUs need
1274 significantly divergent settings. An incorrect value
1275 will cause delays in the kernel to be wrong, leading to
1276 unpredictable I/O errors and other breakage. Although
1277 unlikely, in the extreme case this might damage your
1278 hardware.
1280 ltpc= [NET]
1281 Format: <io>,<irq>,<dma>
1283 mac5380= [HW,SCSI] Format:
1284 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1286 machvec= [IA64] Force the use of a particular machine-vector
1287 (machvec) in a generic kernel.
1288 Example: machvec=hpzx1_swiotlb
1290 machtype= [Loongson] Share the same kernel image file between different
1291 yeeloong laptop.
1292 Example: machtype=lemote-yeeloong-2f-7inch
1294 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1295 than or equal to this physical address is ignored.
1297 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1298 should make use of. maxcpus=n : n >= 0 limits the
1299 kernel to using 'n' processors. n=0 is a special case,
1300 it is equivalent to "nosmp", which also disables
1301 the IO APIC.
1303 max_loop= [LOOP] Maximum number of loopback devices that can
1304 be mounted
1305 Format: <1-256>
1307 max_luns= [SCSI] Maximum number of LUNs to probe.
1308 Should be between 1 and 2^32-1.
1310 max_report_luns=
1311 [SCSI] Maximum number of LUNs received.
1312 Should be between 1 and 16384.
1314 mcatest= [IA-64]
1316 mce [X86-32] Machine Check Exception
1318 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1320 md= [HW] RAID subsystems devices and level
1321 See Documentation/md.txt.
1323 mdacon= [MDA]
1324 Format: <first>,<last>
1325 Specifies range of consoles to be captured by the MDA.
1327 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1328 Amount of memory to be used when the kernel is not able
1329 to see the whole system memory or for test.
1330 [X86-32] Use together with memmap= to avoid physical
1331 address space collisions. Without memmap= PCI devices
1332 could be placed at addresses belonging to unused RAM.
1334 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1335 memory.
1337 memchunk=nn[KMG]
1338 [KNL,SH] Allow user to override the default size for
1339 per-device physically contiguous DMA buffers.
1341 memmap=exactmap [KNL,X86] Enable setting of an exact
1342 E820 memory map, as specified by the user.
1343 Such memmap=exactmap lines can be constructed based on
1344 BIOS output or other requirements. See the memmap=nn@ss
1345 option description.
1347 memmap=nn[KMG]@ss[KMG]
1348 [KNL] Force usage of a specific region of memory
1349 Region of memory to be used, from ss to ss+nn.
1351 memmap=nn[KMG]#ss[KMG]
1352 [KNL,ACPI] Mark specific memory as ACPI data.
1353 Region of memory to be used, from ss to ss+nn.
1355 memmap=nn[KMG]$ss[KMG]
1356 [KNL,ACPI] Mark specific memory as reserved.
1357 Region of memory to be used, from ss to ss+nn.
1358 Example: Exclude memory from 0x18690000-0x1869ffff
1359 memmap=64K$0x18690000
1360 or
1361 memmap=0x10000$0x18690000
1363 memory_corruption_check=0/1 [X86]
1364 Some BIOSes seem to corrupt the first 64k of
1365 memory when doing things like suspend/resume.
1366 Setting this option will scan the memory
1367 looking for corruption. Enabling this will
1368 both detect corruption and prevent the kernel
1369 from using the memory being corrupted.
1370 However, its intended as a diagnostic tool; if
1371 repeatable BIOS-originated corruption always
1372 affects the same memory, you can use memmap=
1373 to prevent the kernel from using that memory.
1375 memory_corruption_check_size=size [X86]
1376 By default it checks for corruption in the low
1377 64k, making this memory unavailable for normal
1378 use. Use this parameter to scan for
1379 corruption in more or less memory.
1381 memory_corruption_check_period=seconds [X86]
1382 By default it checks for corruption every 60
1383 seconds. Use this parameter to check at some
1384 other rate. 0 disables periodic checking.
1386 memtest= [KNL,X86] Enable memtest
1387 Format: <integer>
1388 default : 0 <disable>
1389 Specifies the number of memtest passes to be
1390 performed. Each pass selects another test
1391 pattern from a given set of patterns. Memtest
1392 fills the memory with this pattern, validates
1393 memory contents and reserves bad memory
1394 regions that are detected.
1396 meye.*= [HW] Set MotionEye Camera parameters
1397 See Documentation/video4linux/meye.txt.
1399 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1400 Multi-Function General Purpose Timers on AMD Geode
1401 platforms.
1403 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1404 the BIOS has incorrectly applied a workaround. TinyBIOS
1405 version 0.98 is known to be affected, 0.99 fixes the
1406 problem by letting the user disable the workaround.
1408 mga= [HW,DRM]
1410 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1411 physical address is ignored.
1413 mini2440= [ARM,HW,KNL]
1414 Format:[0..2][b][c][t]
1415 Default: "0tb"
1416 MINI2440 configuration specification:
1417 0 - The attached screen is the 3.5" TFT
1418 1 - The attached screen is the 7" TFT
1419 2 - The VGA Shield is attached (1024x768)
1420 Leaving out the screen size parameter will not load
1421 the TFT driver, and the framebuffer will be left
1422 unconfigured.
1423 b - Enable backlight. The TFT backlight pin will be
1424 linked to the kernel VESA blanking code and a GPIO
1425 LED. This parameter is not necessary when using the
1426 VGA shield.
1427 c - Enable the s3c camera interface.
1428 t - Reserved for enabling touchscreen support. The
1429 touchscreen support is not enabled in the mainstream
1430 kernel as of 2.6.30, a preliminary port can be found
1431 in the "bleeding edge" mini2440 support kernel at
1432 http://repo.or.cz/w/linux-2.6/mini2440.git
1434 mminit_loglevel=
1435 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1436 parameter allows control of the logging verbosity for
1437 the additional memory initialisation checks. A value
1438 of 0 disables mminit logging and a level of 4 will
1439 log everything. Information is printed at KERN_DEBUG
1440 so loglevel=8 may also need to be specified.
1442 mousedev.tap_time=
1443 [MOUSE] Maximum time between finger touching and
1444 leaving touchpad surface for touch to be considered
1445 a tap and be reported as a left button click (for
1446 touchpads working in absolute mode only).
1447 Format: <msecs>
1448 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1449 reporting absolute coordinates, such as tablets
1450 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1451 reporting absolute coordinates, such as tablets
1453 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1454 is similar to kernelcore except it specifies the
1455 amount of memory used for migratable allocations.
1456 If both kernelcore and movablecore is specified,
1457 then kernelcore will be at *least* the specified
1458 value but may be more. If movablecore on its own
1459 is specified, the administrator must be careful
1460 that the amount of memory usable for all allocations
1461 is not too small.
1463 mpu401= [HW,OSS]
1464 Format: <io>,<irq>
1466 MTD_Partition= [MTD]
1467 Format: <name>,<region-number>,<size>,<offset>
1469 MTD_Region= [MTD] Format:
1470 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1472 mtdparts= [MTD]
1473 See drivers/mtd/cmdlinepart.c.
1475 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1477 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1479 boundary - index of last SLC block on Flex-OneNAND.
1480 The remaining blocks are configured as MLC blocks.
1481 lock - Configure if Flex-OneNAND boundary should be locked.
1482 Once locked, the boundary cannot be changed.
1483 1 indicates lock status, 0 indicates unlock status.
1485 mtdset= [ARM]
1486 ARM/S3C2412 JIVE boot control
1488 See arch/arm/mach-s3c2412/mach-jive.c
1490 mtouchusb.raw_coordinates=
1491 [HW] Make the MicroTouch USB driver use raw coordinates
1492 ('y', default) or cooked coordinates ('n')
1494 mtrr_chunk_size=nn[KMG] [X86]
1495 used for mtrr cleanup. It is largest continuous chunk
1496 that could hold holes aka. UC entries.
1498 mtrr_gran_size=nn[KMG] [X86]
1499 Used for mtrr cleanup. It is granularity of mtrr block.
1500 Default is 1.
1501 Large value could prevent small alignment from
1502 using up MTRRs.
1504 mtrr_spare_reg_nr=n [X86]
1505 Format: <integer>
1506 Range: 0,7 : spare reg number
1507 Default : 1
1508 Used for mtrr cleanup. It is spare mtrr entries number.
1509 Set to 2 or more if your graphical card needs more.
1511 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1513 NCR_D700= [HW,SCSI]
1514 See header of drivers/scsi/NCR_D700.c.
1516 ncr5380= [HW,SCSI]
1518 ncr53c400= [HW,SCSI]
1520 ncr53c400a= [HW,SCSI]
1522 ncr53c406a= [HW,SCSI]
1524 ncr53c8xx= [HW,SCSI]
1526 netdev= [NET] Network devices parameters
1527 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1528 Note that mem_start is often overloaded to mean
1529 something different and driver-specific.
1530 This usage is only documented in each driver source
1531 file if at all.
1533 nf_conntrack.acct=
1534 [NETFILTER] Enable connection tracking flow accounting
1535 0 to disable accounting
1536 1 to enable accounting
1537 Default value depends on CONFIG_NF_CT_ACCT that is
1538 going to be removed in 2.6.29.
1540 nfsaddrs= [NFS]
1541 See Documentation/filesystems/nfsroot.txt.
1543 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1544 See Documentation/filesystems/nfsroot.txt.
1546 nfs.callback_tcpport=
1547 [NFS] set the TCP port on which the NFSv4 callback
1548 channel should listen.
1550 nfs.cache_getent=
1551 [NFS] sets the pathname to the program which is used
1552 to update the NFS client cache entries.
1554 nfs.cache_getent_timeout=
1555 [NFS] sets the timeout after which an attempt to
1556 update a cache entry is deemed to have failed.
1558 nfs.idmap_cache_timeout=
1559 [NFS] set the maximum lifetime for idmapper cache
1560 entries.
1562 nfs.enable_ino64=
1563 [NFS] enable 64-bit inode numbers.
1564 If zero, the NFS client will fake up a 32-bit inode
1565 number for the readdir() and stat() syscalls instead
1566 of returning the full 64-bit number.
1567 The default is to return 64-bit inode numbers.
1569 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1570 when a NMI is triggered.
1571 Format: [state][,regs][,debounce][,die]
1573 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1574 Format: [panic,][num]
1575 Valid num: 0,1,2
1576 0 - turn nmi_watchdog off
1577 1 - use the IO-APIC timer for the NMI watchdog
1578 2 - use the local APIC for the NMI watchdog using
1579 a performance counter. Note: This will use one
1580 performance counter and the local APIC's performance
1581 vector.
1582 When panic is specified, panic when an NMI watchdog
1583 timeout occurs.
1584 This is useful when you use a panic=... timeout and
1585 need the box quickly up again.
1586 Instead of 1 and 2 it is possible to use the following
1587 symbolic names: lapic and ioapic
1588 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1590 netpoll.carrier_timeout=
1591 [NET] Specifies amount of time (in seconds) that
1592 netpoll should wait for a carrier. By default netpoll
1593 waits 4 seconds.
1595 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1596 emulation library even if a 387 maths coprocessor
1597 is present.
1599 no_console_suspend
1600 [HW] Never suspend the console
1601 Disable suspending of consoles during suspend and
1602 hibernate operations. Once disabled, debugging
1603 messages can reach various consoles while the rest
1604 of the system is being put to sleep (ie, while
1605 debugging driver suspend/resume hooks). This may
1606 not work reliably with all consoles, but is known
1607 to work with serial and VGA consoles.
1609 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1610 caches in the slab allocator. Saves per-node memory,
1611 but will impact performance.
1613 noalign [KNL,ARM]
1615 noapic [SMP,APIC] Tells the kernel to not make use of any
1616 IOAPICs that may be present in the system.
1618 nobats [PPC] Do not use BATs for mapping kernel lowmem
1619 on "Classic" PPC cores.
1621 nocache [ARM]
1623 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1625 nodelayacct [KNL] Disable per-task delay accounting
1627 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1629 nodsp [SH] Disable hardware DSP at boot time.
1631 noefi [X86] Disable EFI runtime services support.
1633 noexec [IA-64]
1635 noexec [X86]
1636 On X86-32 available only on PAE configured kernels.
1637 noexec=on: enable non-executable mappings (default)
1638 noexec=off: disable non-executable mappings
1640 noexec32 [X86-64]
1641 This affects only 32-bit executables.
1642 noexec32=on: enable non-executable mappings (default)
1643 read doesn't imply executable mappings
1644 noexec32=off: disable non-executable mappings
1645 read implies executable mappings
1647 nofpu [SH] Disable hardware FPU at boot time.
1649 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1650 register save and restore. The kernel will only save
1651 legacy floating-point registers on task switch.
1653 noxsave [BUGS=X86] Disables x86 extended register state save
1654 and restore using xsave. The kernel will fallback to
1655 enabling legacy floating-point and sse state.
1657 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1658 wfi(ARM) instruction doesn't work correctly and not to
1659 use it. This is also useful when using JTAG debugger.
1661 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1662 instruction doesn't work correctly and not to
1663 use it.
1665 no_file_caps Tells the kernel not to honor file capabilities. The
1666 only way then for a file to be executed with privilege
1667 is to be setuid root or executed by root.
1669 nohalt [IA-64] Tells the kernel not to use the power saving
1670 function PAL_HALT_LIGHT when idle. This increases
1671 power-consumption. On the positive side, it reduces
1672 interrupt wake-up latency, which may improve performance
1673 in certain environments such as networked servers or
1674 real-time systems.
1676 nohz= [KNL] Boottime enable/disable dynamic ticks
1677 Valid arguments: on, off
1678 Default: on
1680 noiotrap [SH] Disables trapped I/O port accesses.
1682 noirqdebug [X86-32] Disables the code which attempts to detect and
1683 disable unhandled interrupt sources.
1685 no_timer_check [X86,APIC] Disables the code which tests for
1686 broken timer IRQ sources.
1688 noisapnp [ISAPNP] Disables ISA PnP code.
1690 noinitrd [RAM] Tells the kernel not to load any configured
1691 initial RAM disk.
1693 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1694 remapping.
1696 nointroute [IA-64]
1698 nojitter [IA64] Disables jitter checking for ITC timers.
1700 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1702 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1704 noltlbs [PPC] Do not use large page/tlb entries for kernel
1705 lowmem mapping on PPC40x.
1707 nomca [IA-64] Disable machine check abort handling
1709 nomce [X86-32] Machine Check Exception
1711 nomfgpt [X86-32] Disable Multi-Function General Purpose
1712 Timer usage (for AMD Geode machines).
1714 norandmaps Don't use address space randomization. Equivalent to
1715 echo 0 > /proc/sys/kernel/randomize_va_space
1717 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1719 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1720 with UP alternatives
1722 noresidual [PPC] Don't use residual data on PReP machines.
1724 noresume [SWSUSP] Disables resume and restores original swap
1725 space.
1727 no-scroll [VGA] Disables scrollback.
1728 This is required for the Braillex ib80-piezo Braille
1729 reader made by F.H. Papenmeier (Germany).
1731 nosbagart [IA-64]
1733 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1735 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1736 and disable the IO APIC. legacy for "maxcpus=0".
1738 nosoftlockup [KNL] Disable the soft-lockup detector.
1740 noswapaccount [KNL] Disable accounting of swap in memory resource
1741 controller. (See Documentation/cgroups/memory.txt)
1743 nosync [HW,M68K] Disables sync negotiation for all devices.
1745 notsc [BUGS=X86-32] Disable Time Stamp Counter
1747 nousb [USB] Disable the USB subsystem
1749 nowb [ARM]
1751 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1753 nptcg= [IA64] Override max number of concurrent global TLB
1754 purges which is reported from either PAL_VM_SUMMARY or
1755 SAL PALO.
1757 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1759 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1760 one of ['zone', 'node', 'default'] can be specified
1761 This can be set from sysctl after boot.
1762 See Documentation/sysctl/vm.txt for details.
1764 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1765 See Documentation/debugging-via-ohci1394.txt for more
1766 info.
1768 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1769 Rather than timing out after 20 ms if an EC
1770 command is not properly ACKed, override the length
1771 of the timeout. We have interrupts disabled while
1772 waiting for the ACK, so if this is set too high
1773 interrupts *may* be lost!
1775 opl3= [HW,OSS]
1776 Format: <io>
1778 oprofile.timer= [HW]
1779 Use timer interrupt instead of performance counters
1781 oprofile.cpu_type= Force an oprofile cpu type
1782 This might be useful if you have an older oprofile
1783 userland or if you want common events.
1784 Format: { arch_perfmon }
1785 arch_perfmon: [X86] Force use of architectural
1786 perfmon on Intel CPUs instead of the
1787 CPU specific event set.
1789 osst= [HW,SCSI] SCSI Tape Driver
1790 Format: <buffer_size>,<write_threshold>
1791 See also Documentation/scsi/st.txt.
1793 panic= [KNL] Kernel behaviour on panic
1794 Format: <timeout>
1796 parkbd.port= [HW] Parallel port number the keyboard adapter is
1797 connected to, default is 0.
1798 Format: <parport#>
1799 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1800 0 for XT, 1 for AT (default is AT).
1801 Format: <mode>
1803 parport= [HW,PPT] Specify parallel ports. 0 disables.
1804 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1805 Use 'auto' to force the driver to use any
1806 IRQ/DMA settings detected (the default is to
1807 ignore detected IRQ/DMA settings because of
1808 possible conflicts). You can specify the base
1809 address, IRQ, and DMA settings; IRQ and DMA
1810 should be numbers, or 'auto' (for using detected
1811 settings on that particular port), or 'nofifo'
1812 (to avoid using a FIFO even if it is detected).
1813 Parallel ports are assigned in the order they
1814 are specified on the command line, starting
1815 with parport0.
1817 parport_init_mode= [HW,PPT]
1818 Configure VIA parallel port to operate in
1819 a specific mode. This is necessary on Pegasos
1820 computer where firmware has no options for setting
1821 up parallel port mode and sets it to spp.
1822 Currently this function knows 686a and 8231 chips.
1823 Format: [spp|ps2|epp|ecp|ecpepp]
1825 pas2= [HW,OSS] Format:
1826 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1828 pas16= [HW,SCSI]
1829 See header of drivers/scsi/pas16.c.
1831 pause_on_oops=
1832 Halt all CPUs after the first oops has been printed for
1833 the specified number of seconds. This is to be used if
1834 your oopses keep scrolling off the screen.
1836 pcbit= [HW,ISDN]
1838 pcd. [PARIDE]
1839 See header of drivers/block/paride/pcd.c.
1840 See also Documentation/blockdev/paride.txt.
1842 pci=option[,option...] [PCI] various PCI subsystem options:
1843 earlydump [X86] dump PCI config space before the kernel
1844 changes anything
1845 off [X86] don't probe for the PCI bus
1846 bios [X86-32] force use of PCI BIOS, don't access
1847 the hardware directly. Use this if your machine
1848 has a non-standard PCI host bridge.
1849 nobios [X86-32] disallow use of PCI BIOS, only direct
1850 hardware access methods are allowed. Use this
1851 if you experience crashes upon bootup and you
1852 suspect they are caused by the BIOS.
1853 conf1 [X86] Force use of PCI Configuration
1854 Mechanism 1.
1855 conf2 [X86] Force use of PCI Configuration
1856 Mechanism 2.
1857 noaer [PCIE] If the PCIEAER kernel config parameter is
1858 enabled, this kernel boot option can be used to
1859 disable the use of PCIE advanced error reporting.
1860 nodomains [PCI] Disable support for multiple PCI
1861 root domains (aka PCI segments, in ACPI-speak).
1862 nommconf [X86] Disable use of MMCONFIG for PCI
1863 Configuration
1864 check_enable_amd_mmconf [X86] check for and enable
1865 properly configured MMIO access to PCI
1866 config space on AMD family 10h CPU
1867 nomsi [MSI] If the PCI_MSI kernel config parameter is
1868 enabled, this kernel boot option can be used to
1869 disable the use of MSI interrupts system-wide.
1870 noioapicquirk [APIC] Disable all boot interrupt quirks.
1871 Safety option to keep boot IRQs enabled. This
1872 should never be necessary.
1873 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1874 primary IO-APIC for bridges that cannot disable
1875 boot IRQs. This fixes a source of spurious IRQs
1876 when the system masks IRQs.
1877 noioapicreroute [APIC] Disable workaround that uses the
1878 boot IRQ equivalent of an IRQ that connects to
1879 a chipset where boot IRQs cannot be disabled.
1880 The opposite of ioapicreroute.
1881 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1882 routing table. These calls are known to be buggy
1883 on several machines and they hang the machine
1884 when used, but on other computers it's the only
1885 way to get the interrupt routing table. Try
1886 this option if the kernel is unable to allocate
1887 IRQs or discover secondary PCI buses on your
1888 motherboard.
1889 rom [X86] Assign address space to expansion ROMs.
1890 Use with caution as certain devices share
1891 address decoders between ROMs and other
1892 resources.
1893 norom [X86] Do not assign address space to
1894 expansion ROMs that do not already have
1895 BIOS assigned address ranges.
1896 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1897 assigned automatically to PCI devices. You can
1898 make the kernel exclude IRQs of your ISA cards
1899 this way.
1900 pirqaddr=0xAAAAA [X86] Specify the physical address
1901 of the PIRQ table (normally generated
1902 by the BIOS) if it is outside the
1903 F0000h-100000h range.
1904 lastbus=N [X86] Scan all buses thru bus #N. Can be
1905 useful if the kernel is unable to find your
1906 secondary buses and you want to tell it
1907 explicitly which ones they are.
1908 assign-busses [X86] Always assign all PCI bus
1909 numbers ourselves, overriding
1910 whatever the firmware may have done.
1911 usepirqmask [X86] Honor the possible IRQ mask stored
1912 in the BIOS $PIR table. This is needed on
1913 some systems with broken BIOSes, notably
1914 some HP Pavilion N5400 and Omnibook XE3
1915 notebooks. This will have no effect if ACPI
1916 IRQ routing is enabled.
1917 noacpi [X86] Do not use ACPI for IRQ routing
1918 or for PCI scanning.
1919 use_crs [X86] Use _CRS for PCI resource
1920 allocation.
1921 routeirq Do IRQ routing for all PCI devices.
1922 This is normally done in pci_enable_device(),
1923 so this option is a temporary workaround
1924 for broken drivers that don't call it.
1925 skip_isa_align [X86] do not align io start addr, so can
1926 handle more pci cards
1927 firmware [ARM] Do not re-enumerate the bus but instead
1928 just use the configuration from the
1929 bootloader. This is currently used on
1930 IXP2000 systems where the bus has to be
1931 configured a certain way for adjunct CPUs.
1932 noearly [X86] Don't do any early type 1 scanning.
1933 This might help on some broken boards which
1934 machine check when some devices' config space
1935 is read. But various workarounds are disabled
1936 and some IOMMU drivers will not work.
1937 bfsort Sort PCI devices into breadth-first order.
1938 This sorting is done to get a device
1939 order compatible with older (<= 2.4) kernels.
1940 nobfsort Don't sort PCI devices into breadth-first order.
1941 cbiosize=nn[KMG] The fixed amount of bus space which is
1942 reserved for the CardBus bridge's IO window.
1943 The default value is 256 bytes.
1944 cbmemsize=nn[KMG] The fixed amount of bus space which is
1945 reserved for the CardBus bridge's memory
1946 window. The default value is 64 megabytes.
1947 resource_alignment=
1948 Format:
1949 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1950 Specifies alignment and device to reassign
1951 aligned memory resources.
1952 If <order of align> is not specified,
1953 PAGE_SIZE is used as alignment.
1954 PCI-PCI bridge can be specified, if resource
1955 windows need to be expanded.
1956 ecrc= Enable/disable PCIe ECRC (transaction layer
1957 end-to-end CRC checking).
1958 bios: Use BIOS/firmware settings. This is the
1959 the default.
1960 off: Turn ECRC off
1961 on: Turn ECRC on.
1963 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1964 Management.
1965 off Disable ASPM.
1966 force Enable ASPM even on devices that claim not to support it.
1967 WARNING: Forcing ASPM on may cause system lockups.
1969 pcmv= [HW,PCMCIA] BadgePAD 4
1971 pd. [PARIDE]
1972 See Documentation/blockdev/paride.txt.
1974 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1975 boot time.
1976 Format: { 0 | 1 }
1977 See arch/parisc/kernel/pdc_chassis.c
1979 percpu_alloc= Select which percpu first chunk allocator to use.
1980 Currently supported values are "embed" and "page".
1981 Archs may support subset or none of the selections.
1982 See comments in mm/percpu.c for details on each
1983 allocator. This parameter is primarily for debugging
1984 and performance comparison.
1986 pf. [PARIDE]
1987 See Documentation/blockdev/paride.txt.
1989 pg. [PARIDE]
1990 See Documentation/blockdev/paride.txt.
1992 pirq= [SMP,APIC] Manual mp-table setup
1993 See Documentation/x86/i386/IO-APIC.txt.
1995 plip= [PPT,NET] Parallel port network link
1996 Format: { parport<nr> | timid | 0 }
1997 See also Documentation/parport.txt.
1999 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2000 Override pmtimer IOPort with a hex value.
2001 e.g. pmtmr=0x508
2003 pnp.debug [PNP]
2004 Enable PNP debug messages. This depends on the
2005 CONFIG_PNP_DEBUG_MESSAGES option.
2007 pnpacpi= [ACPI]
2008 { off }
2010 pnpbios= [ISAPNP]
2011 { on | off | curr | res | no-curr | no-res }
2013 pnp_reserve_irq=
2014 [ISAPNP] Exclude IRQs for the autoconfiguration
2016 pnp_reserve_dma=
2017 [ISAPNP] Exclude DMAs for the autoconfiguration
2019 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2020 Ranges are in pairs (I/O port base and size).
2022 pnp_reserve_mem=
2023 [ISAPNP] Exclude memory regions for the
2024 autoconfiguration.
2025 Ranges are in pairs (memory base and size).
2027 ports= [IP_VS_FTP] IPVS ftp helper module
2028 Default is 21.
2029 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2030 may be specified.
2031 Format: <port>,<port>....
2033 print-fatal-signals=
2034 [KNL] debug: print fatal signals
2035 print-fatal-signals=1: print segfault info to
2036 the kernel console.
2037 default: off.
2039 printk.time= Show timing data prefixed to each printk message line
2040 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2042 processor.max_cstate= [HW,ACPI]
2043 Limit processor to maximum C-state
2044 max_cstate=9 overrides any DMI blacklist limit.
2046 processor.nocst [HW,ACPI]
2047 Ignore the _CST method to determine C-states,
2048 instead using the legacy FADT method
2050 profile= [KNL] Enable kernel profiling via /proc/profile
2051 Format: [schedule,]<number>
2052 Param: "schedule" - profile schedule points.
2053 Param: <number> - step/bucket size as a power of 2 for
2054 statistical time based profiling.
2055 Param: "sleep" - profile D-state sleeping (millisecs).
2056 Requires CONFIG_SCHEDSTATS
2057 Param: "kvm" - profile VM exits.
2059 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2060 before loading.
2061 See Documentation/blockdev/ramdisk.txt.
2063 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2064 probe for; one of (bare|imps|exps|lifebook|any).
2065 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2066 per second.
2067 psmouse.resetafter= [HW,MOUSE]
2068 Try to reset the device after so many bad packets
2069 (0 = never).
2070 psmouse.resolution=
2071 [HW,MOUSE] Set desired mouse resolution, in dpi.
2072 psmouse.smartscroll=
2073 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2074 0 = disabled, 1 = enabled (default).
2076 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2077 Format:
2078 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2080 pt. [PARIDE]
2081 See Documentation/blockdev/paride.txt.
2083 pty.legacy_count=
2084 [KNL] Number of legacy pty's. Overwrites compiled-in
2085 default number.
2087 quiet [KNL] Disable most log messages
2089 r128= [HW,DRM]
2091 raid= [HW,RAID]
2092 See Documentation/md.txt.
2094 ramdisk_blocksize= [RAM]
2095 See Documentation/blockdev/ramdisk.txt.
2097 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2098 See Documentation/blockdev/ramdisk.txt.
2100 rcupdate.blimit= [KNL,BOOT]
2101 Set maximum number of finished RCU callbacks to process
2102 in one batch.
2104 rcupdate.qhimark= [KNL,BOOT]
2105 Set threshold of queued
2106 RCU callbacks over which batch limiting is disabled.
2108 rcupdate.qlowmark= [KNL,BOOT]
2109 Set threshold of queued RCU callbacks below which
2110 batch limiting is re-enabled.
2112 rdinit= [KNL]
2113 Format: <full_path>
2114 Run specified binary instead of /init from the ramdisk,
2115 used for early userspace startup. See initrd.
2117 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2118 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2119 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2121 relax_domain_level=
2122 [KNL, SMP] Set scheduler's default relax_domain_level.
2123 See Documentation/cgroups/cpusets.txt.
2125 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2127 reservetop= [X86-32]
2128 Format: nn[KMG]
2129 Reserves a hole at the top of the kernel virtual
2130 address space.
2132 reset_devices [KNL] Force drivers to reset the underlying device
2133 during initialization.
2135 resume= [SWSUSP]
2136 Specify the partition device for software suspend
2138 resume_offset= [SWSUSP]
2139 Specify the offset from the beginning of the partition
2140 given by "resume=" at which the swap header is located,
2141 in <PAGE_SIZE> units (needed only for swap files).
2142 See Documentation/power/swsusp-and-swap-files.txt
2144 retain_initrd [RAM] Keep initrd memory after extraction
2146 rhash_entries= [KNL,NET]
2147 Set number of hash buckets for route cache
2149 riscom8= [HW,SERIAL]
2150 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2152 ro [KNL] Mount root device read-only on boot
2154 root= [KNL] Root filesystem
2156 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2157 mount the root filesystem
2159 rootflags= [KNL] Set root filesystem mount option string
2161 rootfstype= [KNL] Set root filesystem type
2163 rootwait [KNL] Wait (indefinitely) for root device to show up.
2164 Useful for devices that are detected asynchronously
2165 (e.g. USB and MMC devices).
2167 root_plug.vendor_id=
2168 [ROOTPLUG] Override the default vendor ID
2170 root_plug.product_id=
2171 [ROOTPLUG] Override the default product ID
2173 root_plug.debug=
2174 [ROOTPLUG] Enable debugging output
2176 rw [KNL] Mount root device read-write on boot
2178 S [KNL] Run init in single mode
2180 sa1100ir [NET]
2181 See drivers/net/irda/sa1100_ir.c.
2183 sbni= [NET] Granch SBNI12 leased line adapter
2185 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2186 Format: <io>[,<timeout>[,<isapnp>]]
2188 scsi_debug_*= [SCSI]
2189 See drivers/scsi/scsi_debug.c.
2191 scsi_default_dev_flags=
2192 [SCSI] SCSI default device flags
2193 Format: <integer>
2195 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2196 Format: <vendor>:<model>:<flags>
2197 (flags are integer value)
2199 scsi_logging_level= [SCSI] a bit mask of logging levels
2200 See drivers/scsi/scsi_logging.h for bits. Also
2201 settable via sysctl at dev.scsi.logging_level
2202 (/proc/sys/dev/scsi/logging_level).
2203 There is also a nice 'scsi_logging_level' script in the
2204 S390-tools package, available for download at
2205 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2207 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2208 discovered. async scans them in kernel threads,
2209 allowing boot to proceed. none ignores them, expecting
2210 user space to do the scan.
2212 security= [SECURITY] Choose a security module to enable at boot.
2213 If this boot parameter is not specified, only the first
2214 security module asking for security registration will be
2215 loaded. An invalid security module name will be treated
2216 as if no module has been chosen.
2218 selinux= [SELINUX] Disable or enable SELinux at boot time.
2219 Format: { "0" | "1" }
2220 See security/selinux/Kconfig help text.
2221 0 -- disable.
2222 1 -- enable.
2223 Default value is set via kernel config option.
2224 If enabled at boot time, /selinux/disable can be used
2225 later to disable prior to initial policy load.
2227 serialnumber [BUGS=X86-32]
2229 shapers= [NET]
2230 Maximal number of shapers.
2232 show_msr= [x86] show boot-time MSR settings
2233 Format: { <integer> }
2234 Show boot-time (BIOS-initialized) MSR settings.
2235 The parameter means the number of CPUs to show,
2236 for example 1 means boot CPU only.
2238 sim710= [SCSI,HW]
2239 See header of drivers/scsi/sim710.c.
2241 simeth= [IA-64]
2242 simscsi=
2244 slram= [HW,MTD]
2246 slub_debug[=options[,slabs]] [MM, SLUB]
2247 Enabling slub_debug allows one to determine the
2248 culprit if slab objects become corrupted. Enabling
2249 slub_debug can create guard zones around objects and
2250 may poison objects when not in use. Also tracks the
2251 last alloc / free. For more information see
2252 Documentation/vm/slub.txt.
2254 slub_max_order= [MM, SLUB]
2255 Determines the maximum allowed order for slabs.
2256 A high setting may cause OOMs due to memory
2257 fragmentation. For more information see
2258 Documentation/vm/slub.txt.
2260 slub_min_objects= [MM, SLUB]
2261 The minimum number of objects per slab. SLUB will
2262 increase the slab order up to slub_max_order to
2263 generate a sufficiently large slab able to contain
2264 the number of objects indicated. The higher the number
2265 of objects the smaller the overhead of tracking slabs
2266 and the less frequently locks need to be acquired.
2267 For more information see Documentation/vm/slub.txt.
2269 slub_min_order= [MM, SLUB]
2270 Determines the mininum page order for slabs. Must be
2271 lower than slub_max_order.
2272 For more information see Documentation/vm/slub.txt.
2274 slub_nomerge [MM, SLUB]
2275 Disable merging of slabs with similar size. May be
2276 necessary if there is some reason to distinguish
2277 allocs to different slabs. Debug options disable
2278 merging on their own.
2279 For more information see Documentation/vm/slub.txt.
2281 smart2= [HW]
2282 Format: <io1>[,<io2>[,...,<io8>]]
2284 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2285 attempt to substitute SMP alternatives once at boot.
2287 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2288 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2289 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2290 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2291 smsc-ircc2.ircc_irq= [HW] IRQ line
2292 smsc-ircc2.ircc_dma= [HW] DMA channel
2293 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2294 0: Toshiba Satellite 1800 (GP data pin select)
2295 1: Fast pin select (default)
2296 2: ATC IRMode
2298 snd-ad1816a= [HW,ALSA]
2300 snd-ad1848= [HW,ALSA]
2302 snd-ali5451= [HW,ALSA]
2304 snd-als100= [HW,ALSA]
2306 snd-als4000= [HW,ALSA]
2308 snd-azt2320= [HW,ALSA]
2310 snd-cmi8330= [HW,ALSA]
2312 snd-cmipci= [HW,ALSA]
2314 snd-cs4231= [HW,ALSA]
2316 snd-cs4232= [HW,ALSA]
2318 snd-cs4236= [HW,ALSA]
2320 snd-cs4281= [HW,ALSA]
2322 snd-cs46xx= [HW,ALSA]
2324 snd-dt019x= [HW,ALSA]
2326 snd-dummy= [HW,ALSA]
2328 snd-emu10k1= [HW,ALSA]
2330 snd-ens1370= [HW,ALSA]
2332 snd-ens1371= [HW,ALSA]
2334 snd-es968= [HW,ALSA]
2336 snd-es1688= [HW,ALSA]
2338 snd-es18xx= [HW,ALSA]
2340 snd-es1938= [HW,ALSA]
2342 snd-es1968= [HW,ALSA]
2344 snd-fm801= [HW,ALSA]
2346 snd-gusclassic= [HW,ALSA]
2348 snd-gusextreme= [HW,ALSA]
2350 snd-gusmax= [HW,ALSA]
2352 snd-hdsp= [HW,ALSA]
2354 snd-ice1712= [HW,ALSA]
2356 snd-intel8x0= [HW,ALSA]
2358 snd-interwave= [HW,ALSA]
2360 snd-interwave-stb=
2361 [HW,ALSA]
2363 snd-korg1212= [HW,ALSA]
2365 snd-maestro3= [HW,ALSA]
2367 snd-mpu401= [HW,ALSA]
2369 snd-mtpav= [HW,ALSA]
2371 snd-nm256= [HW,ALSA]
2373 snd-opl3sa2= [HW,ALSA]
2375 snd-opti92x-ad1848=
2376 [HW,ALSA]
2378 snd-opti92x-cs4231=
2379 [HW,ALSA]
2381 snd-opti93x= [HW,ALSA]
2383 snd-pmac= [HW,ALSA]
2385 snd-rme32= [HW,ALSA]
2387 snd-rme96= [HW,ALSA]
2389 snd-rme9652= [HW,ALSA]
2391 snd-sb8= [HW,ALSA]
2393 snd-sb16= [HW,ALSA]
2395 snd-sbawe= [HW,ALSA]
2397 snd-serial= [HW,ALSA]
2399 snd-sgalaxy= [HW,ALSA]
2401 snd-sonicvibes= [HW,ALSA]
2403 snd-sun-amd7930=
2404 [HW,ALSA]
2406 snd-sun-cs4231= [HW,ALSA]
2408 snd-trident= [HW,ALSA]
2410 snd-usb-audio= [HW,ALSA,USB]
2412 snd-via82xx= [HW,ALSA]
2414 snd-virmidi= [HW,ALSA]
2416 snd-wavefront= [HW,ALSA]
2418 snd-ymfpci= [HW,ALSA]
2420 softlockup_panic=
2421 [KNL] Should the soft-lockup detector generate panics.
2423 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2424 See Documentation/sonypi.txt
2426 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2427 See Documentation/serial/specialix.txt.
2429 spia_io_base= [HW,MTD]
2430 spia_fio_base=
2431 spia_pedr=
2432 spia_peddr=
2434 sscape= [HW,OSS]
2435 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2437 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2438 See Documentation/scsi/st.txt.
2440 stacktrace [FTRACE]
2441 Enabled the stack tracer on boot up.
2443 sti= [PARISC,HW]
2444 Format: <num>
2445 Set the STI (builtin display/keyboard on the HP-PARISC
2446 machines) console (graphic card) which should be used
2447 as the initial boot-console.
2448 See also comment in drivers/video/console/sticore.c.
2450 sti_font= [HW]
2451 See comment in drivers/video/console/sticore.c.
2453 stifb= [HW]
2454 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2456 sunrpc.min_resvport=
2457 sunrpc.max_resvport=
2458 [NFS,SUNRPC]
2459 SunRPC servers often require that client requests
2460 originate from a privileged port (i.e. a port in the
2461 range 0 < portnr < 1024).
2462 An administrator who wishes to reserve some of these
2463 ports for other uses may adjust the range that the
2464 kernel's sunrpc client considers to be privileged
2465 using these two parameters to set the minimum and
2466 maximum port values.
2468 sunrpc.pool_mode=
2469 [NFS]
2470 Control how the NFS server code allocates CPUs to
2471 service thread pools. Depending on how many NICs
2472 you have and where their interrupts are bound, this
2473 option will affect which CPUs will do NFS serving.
2474 Note: this parameter cannot be changed while the
2475 NFS server is running.
2477 auto the server chooses an appropriate mode
2478 automatically using heuristics
2479 global a single global pool contains all CPUs
2480 percpu one pool for each CPU
2481 pernode one pool for each NUMA node (equivalent
2482 to global on non-NUMA machines)
2484 sunrpc.tcp_slot_table_entries=
2485 sunrpc.udp_slot_table_entries=
2486 [NFS,SUNRPC]
2487 Sets the upper limit on the number of simultaneous
2488 RPC calls that can be sent from the client to a
2489 server. Increasing these values may allow you to
2490 improve throughput, but will also increase the
2491 amount of memory reserved for use by the client.
2493 swiotlb= [IA-64] Number of I/O TLB slabs
2495 switches= [HW,M68k]
2497 sym53c416= [HW,SCSI]
2498 See header of drivers/scsi/sym53c416.c.
2500 sysrq_always_enabled
2501 [KNL]
2502 Ignore sysrq setting - this boot parameter will
2503 neutralize any effect of /proc/sys/kernel/sysrq.
2504 Useful for debugging.
2506 t128= [HW,SCSI]
2507 See header of drivers/scsi/t128.c.
2509 tdfx= [HW,DRM]
2511 test_suspend= [SUSPEND]
2512 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2513 standby suspend) as the system sleep state to briefly
2514 enter during system startup. The system is woken from
2515 this state using a wakeup-capable RTC alarm.
2517 thash_entries= [KNL,NET]
2518 Set number of hash buckets for TCP connection
2520 thermal.act= [HW,ACPI]
2521 -1: disable all active trip points in all thermal zones
2522 <degrees C>: override all lowest active trip points
2524 thermal.crt= [HW,ACPI]
2525 -1: disable all critical trip points in all thermal zones
2526 <degrees C>: override all critical trip points
2528 thermal.nocrt= [HW,ACPI]
2529 Set to disable actions on ACPI thermal zone
2530 critical and hot trip points.
2532 thermal.off= [HW,ACPI]
2533 1: disable ACPI thermal control
2535 thermal.psv= [HW,ACPI]
2536 -1: disable all passive trip points
2537 <degrees C>: override all passive trip points to this
2538 value
2540 thermal.tzp= [HW,ACPI]
2541 Specify global default ACPI thermal zone polling rate
2542 <deci-seconds>: poll all this frequency
2543 0: no polling (default)
2545 tmscsim= [HW,SCSI]
2546 See comment before function dc390_setup() in
2547 drivers/scsi/tmscsim.c.
2549 topology= [S390]
2550 Format: {off | on}
2551 Specify if the kernel should make use of the cpu
2552 topology informations if the hardware supports these.
2553 The scheduler will make use of these informations and
2554 e.g. base its process migration decisions on it.
2555 Default is off.
2557 tp720= [HW,PS2]
2559 trace_buf_size=nn[KMG]
2560 [FTRACE] will set tracing buffer size.
2562 trace_event=[event-list]
2563 [FTRACE] Set and start specified trace events in order
2564 to facilitate early boot debugging.
2565 See also Documentation/trace/events.txt
2567 trix= [HW,OSS] MediaTrix AudioTrix Pro
2568 Format:
2569 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2571 tsc= Disable clocksource-must-verify flag for TSC.
2572 Format: <string>
2573 [x86] reliable: mark tsc clocksource as reliable, this
2574 disables clocksource verification at runtime.
2575 Used to enable high-resolution timer mode on older
2576 hardware, and in virtualized environment.
2578 turbografx.map[2|3]= [HW,JOY]
2579 TurboGraFX parallel port interface
2580 Format:
2581 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2582 See also Documentation/input/joystick-parport.txt
2584 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2585 See header of drivers/scsi/u14-34f.c.
2587 uart401= [HW,OSS]
2588 Format: <io>,<irq>
2590 uart6850= [HW,OSS]
2591 Format: <io>,<irq>
2593 uhash_entries= [KNL,NET]
2594 Set number of hash buckets for UDP/UDP-Lite connections
2596 uhci-hcd.ignore_oc=
2597 [USB] Ignore overcurrent events (default N).
2598 Some badly-designed motherboards generate lots of
2599 bogus events, for ports that aren't wired to
2600 anything. Set this parameter to avoid log spamming.
2601 Note that genuine overcurrent events won't be
2602 reported either.
2604 unknown_nmi_panic
2605 [X86]
2606 Set unknown_nmi_panic=1 early on boot.
2608 usbcore.autosuspend=
2609 [USB] The autosuspend time delay (in seconds) used
2610 for newly-detected USB devices (default 2). This
2611 is the time required before an idle device will be
2612 autosuspended. Devices for which the delay is set
2613 to a negative value won't be autosuspended at all.
2615 usbcore.usbfs_snoop=
2616 [USB] Set to log all usbfs traffic (default 0 = off).
2618 usbcore.blinkenlights=
2619 [USB] Set to cycle leds on hubs (default 0 = off).
2621 usbcore.old_scheme_first=
2622 [USB] Start with the old device initialization
2623 scheme (default 0 = off).
2625 usbcore.use_both_schemes=
2626 [USB] Try the other device initialization scheme
2627 if the first one fails (default 1 = enabled).
2629 usbcore.initial_descriptor_timeout=
2630 [USB] Specifies timeout for the initial 64-byte
2631 USB_REQ_GET_DESCRIPTOR request in milliseconds
2632 (default 5000 = 5.0 seconds).
2634 usbhid.mousepoll=
2635 [USBHID] The interval which mice are to be polled at.
2637 usb-storage.delay_use=
2638 [UMS] The delay in seconds before a new device is
2639 scanned for Logical Units (default 5).
2641 usb-storage.quirks=
2642 [UMS] A list of quirks entries to supplement or
2643 override the built-in unusual_devs list. List
2644 entries are separated by commas. Each entry has
2645 the form VID:PID:Flags where VID and PID are Vendor
2646 and Product ID values (4-digit hex numbers) and
2647 Flags is a set of characters, each corresponding
2648 to a common usb-storage quirk flag as follows:
2649 a = SANE_SENSE (collect more than 18 bytes
2650 of sense data);
2651 c = FIX_CAPACITY (decrease the reported
2652 device capacity by one sector);
2653 h = CAPACITY_HEURISTICS (decrease the
2654 reported device capacity by one
2655 sector if the number is odd);
2656 i = IGNORE_DEVICE (don't bind to this
2657 device);
2658 l = NOT_LOCKABLE (don't try to lock and
2659 unlock ejectable media);
2660 m = MAX_SECTORS_64 (don't transfer more
2661 than 64 sectors = 32 KB at a time);
2662 o = CAPACITY_OK (accept the capacity
2663 reported by the device);
2664 r = IGNORE_RESIDUE (the device reports
2665 bogus residue values);
2666 s = SINGLE_LUN (the device has only one
2667 Logical Unit);
2668 w = NO_WP_DETECT (don't test whether the
2669 medium is write-protected).
2670 Example: quirks=0419:aaf5:rl,0421:0433:rc
2672 vdso= [X86,SH]
2673 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2674 vdso=1: enable VDSO (default)
2675 vdso=0: disable VDSO mapping
2677 vdso32= [X86]
2678 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2679 vdso32=1: enable 32-bit VDSO (default)
2680 vdso32=0: disable 32-bit VDSO mapping
2682 vector= [IA-64,SMP]
2683 vector=percpu: enable percpu vector domain
2685 video= [FB] Frame buffer configuration
2686 See Documentation/fb/modedb.txt.
2688 vga= [BOOT,X86-32] Select a particular video mode
2689 See Documentation/x86/boot.txt and
2690 Documentation/svga.txt.
2691 Use vga=ask for menu.
2692 This is actually a boot loader parameter; the value is
2693 passed to the kernel using a special protocol.
2695 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2696 size of <nn>. This can be used to increase the
2697 minimum size (128MB on x86). It can also be used to
2698 decrease the size and leave more room for directly
2699 mapped kernel RAM.
2701 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2702 Format: <command>
2704 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2705 Format: <command>
2707 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2708 Format: <command>
2710 vt.default_blu= [VT]
2711 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2712 Change the default blue palette of the console.
2713 This is a 16-member array composed of values
2714 ranging from 0-255.
2716 vt.default_grn= [VT]
2717 Format: <green0>,<green1>,<green2>,...,<green15>
2718 Change the default green palette of the console.
2719 This is a 16-member array composed of values
2720 ranging from 0-255.
2722 vt.default_red= [VT]
2723 Format: <red0>,<red1>,<red2>,...,<red15>
2724 Change the default red palette of the console.
2725 This is a 16-member array composed of values
2726 ranging from 0-255.
2728 vt.default_utf8=
2729 [VT]
2730 Format=<0|1>
2731 Set system-wide default UTF-8 mode for all tty's.
2732 Default is 1, i.e. UTF-8 mode is enabled for all
2733 newly opened terminals.
2735 waveartist= [HW,OSS]
2736 Format: <io>,<irq>,<dma>,<dma2>
2738 wd33c93= [HW,SCSI]
2739 See header of drivers/scsi/wd33c93.c.
2741 wd7000= [HW,SCSI]
2742 See header of drivers/scsi/wd7000.c.
2744 wdt= [WDT] Watchdog
2745 See Documentation/watchdog/wdt.txt.
2747 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2748 default x2apic cluster mode on platforms
2749 supporting x2apic.
2751 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2752 xd_geo= See header of drivers/block/xd.c.
2754 xirc2ps_cs= [NET,PCMCIA]
2755 Format:
2756 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2758 ______________________________________________________________________
2760 TODO:
2762 Add documentation for ALSA options.
2763 Add more DRM drivers.