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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, sci_force_enable }
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.
257 sci_force_enable causes the kernel to set SCI_EN directly
258 on resume from S1/S3 (which is against the ACPI spec,
259 but some broken systems don't work without it).
261 acpi_use_timer_override [HW,ACPI]
262 Use timer override. For some broken Nvidia NF5 boards
263 that require a timer override, but don't have HPET
265 acpi_enforce_resources= [ACPI]
266 { strict | lax | no }
267 Check for resource conflicts between native drivers
268 and ACPI OperationRegions (SystemIO and SystemMemory
269 only). IO ports and memory declared in ACPI might be
270 used by the ACPI subsystem in arbitrary AML code and
271 can interfere with legacy drivers.
272 strict (default): access to resources claimed by ACPI
273 is denied; legacy drivers trying to access reserved
274 resources will fail to bind to device using them.
275 lax: access to resources claimed by ACPI is allowed;
276 legacy drivers trying to access reserved resources
277 will bind successfully but a warning message is logged.
278 no: ACPI OperationRegions are not marked as reserved,
279 no further checks are performed.
281 ad1848= [HW,OSS]
282 Format: <io>,<irq>,<dma>,<dma2>,<type>
284 add_efi_memmap [EFI; X86] Include EFI memory map in
285 kernel's map of available physical RAM.
287 advansys= [HW,SCSI]
288 See header of drivers/scsi/advansys.c.
290 advwdt= [HW,WDT] Advantech WDT
291 Format: <iostart>,<iostop>
293 aedsp16= [HW,OSS] Audio Excel DSP 16
294 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
295 See also header of sound/oss/aedsp16.c.
297 agp= [AGP]
298 { off | try_unsupported }
299 off: disable AGP support
300 try_unsupported: try to drive unsupported chipsets
301 (may crash computer or cause data corruption)
303 aha152x= [HW,SCSI]
304 See Documentation/scsi/aha152x.txt.
306 aha1542= [HW,SCSI]
307 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
309 aic7xxx= [HW,SCSI]
310 See Documentation/scsi/aic7xxx.txt.
312 aic79xx= [HW,SCSI]
313 See Documentation/scsi/aic79xx.txt.
315 amd_iommu= [HW,X86-84]
316 Pass parameters to the AMD IOMMU driver in the system.
317 Possible values are:
318 isolate - enable device isolation (each device, as far
319 as possible, will get its own protection
320 domain) [default]
321 share - put every device behind one IOMMU into the
322 same protection domain
323 fullflush - enable flushing of IO/TLB entries when
324 they are unmapped. Otherwise they are
325 flushed before they will be reused, which
326 is a lot of faster
328 amijoy.map= [HW,JOY] Amiga joystick support
329 Map of devices attached to JOY0DAT and JOY1DAT
330 Format: <a>,<b>
331 See also Documentation/kernel/input/joystick.txt
333 analog.map= [HW,JOY] Analog joystick and gamepad support
334 Specifies type or capabilities of an analog joystick
335 connected to one of 16 gameports
336 Format: <type1>,<type2>,..<type16>
338 apc= [HW,SPARC]
339 Power management functions (SPARCstation-4/5 + deriv.)
340 Format: noidle
341 Disable APC CPU standby support. SPARCstation-Fox does
342 not play well with APC CPU idle - disable it if you have
343 APC and your system crashes randomly.
345 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
346 Change the output verbosity whilst booting
347 Format: { quiet (default) | verbose | debug }
348 Change the amount of debugging information output
349 when initialising the APIC and IO-APIC components.
351 apm= [APM] Advanced Power Management
352 See header of arch/x86/kernel/apm_32.c.
354 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
355 Format: <io>,<irq>,<nodeID>
357 ataflop= [HW,M68k]
359 atarimouse= [HW,MOUSE] Atari Mouse
361 atascsi= [HW,SCSI] Atari SCSI
363 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
364 EzKey and similar keyboards
366 atkbd.reset= [HW] Reset keyboard during initialization
368 atkbd.set= [HW] Select keyboard code set
369 Format: <int> (2 = AT (default), 3 = PS/2)
371 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
372 keyboards
374 atkbd.softraw= [HW] Choose between synthetic and real raw mode
375 Format: <bool> (0 = real, 1 = synthetic (default))
377 atkbd.softrepeat= [HW]
378 Use software keyboard repeat
380 autotest [IA64]
382 baycom_epp= [HW,AX25]
383 Format: <io>,<mode>
385 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
386 Format: <io>,<mode>
387 See header of drivers/net/hamradio/baycom_par.c.
389 baycom_ser_fdx= [HW,AX25]
390 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
391 Format: <io>,<irq>,<mode>[,<baud>]
392 See header of drivers/net/hamradio/baycom_ser_fdx.c.
394 baycom_ser_hdx= [HW,AX25]
395 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
396 Format: <io>,<irq>,<mode>
397 See header of drivers/net/hamradio/baycom_ser_hdx.c.
399 boot_delay= Milliseconds to delay each printk during boot.
400 Values larger than 10 seconds (10000) are changed to
401 no delay (0).
402 Format: integer
404 bootmem_debug [KNL] Enable bootmem allocator debug messages.
406 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
407 bttv.radio= Most important insmod options are available as
408 kernel args too.
409 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
410 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
412 BusLogic= [HW,SCSI]
413 See drivers/scsi/BusLogic.c, comment before function
414 BusLogic_ParseDriverOptions().
416 c101= [NET] Moxa C101 synchronous serial card
418 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
419 Sometimes CPU hardware bugs make them report the cache
420 size incorrectly. The kernel will attempt work arounds
421 to fix known problems, but for some CPUs it is not
422 possible to determine what the correct size should be.
423 This option provides an override for these situations.
425 capability.disable=
426 [SECURITY] Disable capabilities. This would normally
427 be used only if an alternative security model is to be
428 configured. Potentially dangerous and should only be
429 used if you are entirely sure of the consequences.
431 ccw_timeout_log [S390]
432 See Documentation/s390/CommonIO for details.
434 cgroup_disable= [KNL] Disable a particular controller
435 Format: {name of the controller(s) to disable}
436 {Currently supported controllers - "memory"}
438 checkreqprot [SELINUX] Set initial checkreqprot flag value.
439 Format: { "0" | "1" }
440 See security/selinux/Kconfig help text.
441 0 -- check protection applied by kernel (includes
442 any implied execute protection).
443 1 -- check protection requested by application.
444 Default value is set via a kernel config option.
445 Value can be changed at runtime via
446 /selinux/checkreqprot.
448 cio_ignore= [S390]
449 See Documentation/s390/CommonIO for details.
451 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
452 [Deprecated]
453 Forces specified clocksource (if available) to be used
454 when calculating gettimeofday(). If specified
455 clocksource is not available, it defaults to PIT.
456 Format: { pit | tsc | cyclone | pmtmr }
458 clocksource= [GENERIC_TIME] Override the default clocksource
459 Format: <string>
460 Override the default clocksource and use the clocksource
461 with the name specified.
462 Some clocksource names to choose from, depending on
463 the platform:
464 [all] jiffies (this is the base, fallback clocksource)
465 [ACPI] acpi_pm
466 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
467 pxa_timer,timer3,32k_counter,timer0_1
468 [AVR32] avr32
469 [X86-32] pit,hpet,tsc,vmi-timer;
470 scx200_hrt on Geode; cyclone on IBM x440
471 [MIPS] MIPS
472 [PARISC] cr16
473 [S390] tod
474 [SH] SuperH
475 [SPARC64] tick
476 [X86-64] hpet,tsc
478 clearcpuid=BITNUM [X86]
479 Disable CPUID feature X for the kernel. See
480 arch/x86/include/asm/cpufeature.h for the valid bit
481 numbers. Note the Linux specific bits are not necessarily
482 stable over kernel options, but the vendor specific
483 ones should be.
484 Also note that user programs calling CPUID directly
485 or using the feature without checking anything
486 will still see it. This just prevents it from
487 being used by the kernel or shown in /proc/cpuinfo.
488 Also note the kernel might malfunction if you disable
489 some critical bits.
491 cmo_free_hint= [PPC] Format: { yes | no }
492 Specify whether pages are marked as being inactive
493 when they are freed. This is used in CMO environments
494 to determine OS memory pressure for page stealing by
495 a hypervisor.
496 Default: yes
498 code_bytes [X86] How many bytes of object code to print
499 in an oops report.
500 Range: 0 - 8192
501 Default: 64
503 com20020= [HW,NET] ARCnet - COM20020 chipset
504 Format:
505 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
507 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
508 Format: <io>[,<irq>]
510 com90xx= [HW,NET]
511 ARCnet - COM90xx chipset (memory-mapped buffers)
512 Format: <io>[,<irq>[,<memstart>]]
514 condev= [HW,S390] console device
515 conmode=
517 console= [KNL] Output console device and options.
519 tty<n> Use the virtual console device <n>.
521 ttyS<n>[,options]
522 ttyUSB0[,options]
523 Use the specified serial port. The options are of
524 the form "bbbbpnf", where "bbbb" is the baud rate,
525 "p" is parity ("n", "o", or "e"), "n" is number of
526 bits, and "f" is flow control ("r" for RTS or
527 omit it). Default is "9600n8".
529 See Documentation/serial-console.txt for more
530 information. See
531 Documentation/networking/netconsole.txt for an
532 alternative.
534 uart[8250],io,<addr>[,options]
535 uart[8250],mmio,<addr>[,options]
536 Start an early, polled-mode console on the 8250/16550
537 UART at the specified I/O port or MMIO address,
538 switching to the matching ttyS device later. The
539 options are the same as for ttyS, above.
541 If the device connected to the port is not a TTY but a braille
542 device, prepend "brl," before the device type, for instance
543 console=brl,ttyS0
544 For now, only VisioBraille is supported.
546 consoleblank= [KNL] The console blank (screen saver) timeout in
547 seconds. Defaults to 10*60 = 10mins. A value of 0
548 disables the blank timer.
550 coredump_filter=
551 [KNL] Change the default value for
552 /proc/<pid>/coredump_filter.
553 See also Documentation/filesystems/proc.txt.
555 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
556 Format:
557 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
559 crashkernel=nn[KMG]@ss[KMG]
560 [KNL] Reserve a chunk of physical memory to
561 hold a kernel to switch to with kexec on panic.
563 crashkernel=range1:size1[,range2:size2,...][@offset]
564 [KNL] Same as above, but depends on the memory
565 in the running system. The syntax of range is
566 start-[end] where start and end are both
567 a memory unit (amount[KMG]). See also
568 Documentation/kdump/kdump.txt for a example.
570 cs89x0_dma= [HW,NET]
571 Format: <dma>
573 cs89x0_media= [HW,NET]
574 Format: { rj45 | aui | bnc }
576 dasd= [HW,NET]
577 See header of drivers/s390/block/dasd_devmap.c.
579 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
580 (one device per port)
581 Format: <port#>,<type>
582 See also Documentation/input/joystick-parport.txt
584 debug [KNL] Enable kernel debugging (events log level).
586 debug_locks_verbose=
587 [KNL] verbose self-tests
588 Format=<0|1>
589 Print debugging info while doing the locking API
590 self-tests.
591 We default to 0 (no extra messages), setting it to
592 1 will print _a lot_ more information - normally
593 only useful to kernel developers.
595 debug_objects [KNL] Enable object debugging
597 no_debug_objects
598 [KNL] Disable object debugging
600 debugpat [X86] Enable PAT debugging
602 decnet.addr= [HW,NET]
603 Format: <area>[,<node>]
604 See also Documentation/networking/decnet.txt.
606 default_hugepagesz=
607 [same as hugepagesz=] The size of the default
608 HugeTLB page size. This is the size represented by
609 the legacy /proc/ hugepages APIs, used for SHM, and
610 default size when mounting hugetlbfs filesystems.
611 Defaults to the default architecture's huge page size
612 if not specified.
614 dhash_entries= [KNL]
615 Set number of hash buckets for dentry cache.
617 digi= [HW,SERIAL]
618 IO parameters + enable/disable command.
620 digiepca= [HW,SERIAL]
621 See drivers/char/README.epca and
622 Documentation/serial/digiepca.txt.
624 disable_mtrr_cleanup [X86]
625 The kernel tries to adjust MTRR layout from continuous
626 to discrete, to make X server driver able to add WB
627 entry later. This parameter disables that.
629 disable_mtrr_trim [X86, Intel and AMD only]
630 By default the kernel will trim any uncacheable
631 memory out of your available memory pool based on
632 MTRR settings. This parameter disables that behavior,
633 possibly causing your machine to run very slowly.
635 disable_timer_pin_1 [X86]
636 Disable PIN 1 of APIC timer
637 Can be useful to work around chipset bugs.
639 dmasound= [HW,OSS] Sound subsystem buffers
641 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
642 this option disables the debugging code at boot.
644 dma_debug_entries=<number>
645 This option allows to tune the number of preallocated
646 entries for DMA-API debugging code. One entry is
647 required per DMA-API allocation. Use this if the
648 DMA-API debugging code disables itself because the
649 architectural default is too low.
651 dma_debug_driver=<driver_name>
652 With this option the DMA-API debugging driver
653 filter feature can be enabled at boot time. Just
654 pass the driver to filter for as the parameter.
655 The filter can be disabled or changed to another
656 driver later using sysfs.
658 dscc4.setup= [NET]
660 dtc3181e= [HW,SCSI]
662 dynamic_printk Enables pr_debug()/dev_dbg() calls if
663 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
664 These can also be switched on/off via
665 <debugfs>/dynamic_printk/modules
667 earlycon= [KNL] Output early console device and options.
668 uart[8250],io,<addr>[,options]
669 uart[8250],mmio,<addr>[,options]
670 Start an early, polled-mode console on the 8250/16550
671 UART at the specified I/O port or MMIO address.
672 The options are the same as for ttyS, above.
674 earlyprintk= [X86,SH,BLACKFIN]
675 earlyprintk=vga
676 earlyprintk=serial[,ttySn[,baudrate]]
677 earlyprintk=ttySn[,baudrate]
678 earlyprintk=dbgp[debugController#]
680 Append ",keep" to not disable it when the real console
681 takes over.
683 Only vga or serial or usb debug port at a time.
685 Currently only ttyS0 and ttyS1 are supported.
687 Interaction with the standard serial driver is not
688 very good.
690 The VGA output is eventually overwritten by the real
691 console.
693 eata= [HW,SCSI]
695 edd= [EDD]
696 Format: {"off" | "on" | "skip[mbr]"}
698 eisa_irq_edge= [PARISC,HW]
699 See header of drivers/parisc/eisa.c.
701 elanfreq= [X86-32]
702 See comment before function elanfreq_setup() in
703 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
705 elevator= [IOSCHED]
706 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
707 See Documentation/block/as-iosched.txt and
708 Documentation/block/deadline-iosched.txt for details.
710 elfcorehdr= [IA64,PPC,SH,X86]
711 Specifies physical address of start of kernel core
712 image elf header. Generally kexec loader will
713 pass this option to capture kernel.
714 See Documentation/kdump/kdump.txt for details.
716 enable_mtrr_cleanup [X86]
717 The kernel tries to adjust MTRR layout from continuous
718 to discrete, to make X server driver able to add WB
719 entry later. This parameter enables that.
721 enable_timer_pin_1 [X86]
722 Enable PIN 1 of APIC timer
723 Can be useful to work around chipset bugs
724 (in particular on some ATI chipsets).
725 The kernel tries to set a reasonable default.
727 enforcing [SELINUX] Set initial enforcing status.
728 Format: {"0" | "1"}
729 See security/selinux/Kconfig help text.
730 0 -- permissive (log only, no denials).
731 1 -- enforcing (deny and log).
732 Default value is 0.
733 Value can be changed at runtime via /selinux/enforce.
735 ether= [HW,NET] Ethernet cards parameters
736 This option is obsoleted by the "netdev=" option, which
737 has equivalent usage. See its documentation for details.
739 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
740 Format: <io>[,<irq>]
742 failslab=
743 fail_page_alloc=
744 fail_make_request=[KNL]
745 General fault injection mechanism.
746 Format: <interval>,<probability>,<space>,<times>
747 See also /Documentation/fault-injection/.
749 fd_mcs= [HW,SCSI]
750 See header of drivers/scsi/fd_mcs.c.
752 fdomain= [HW,SCSI]
753 See header of drivers/scsi/fdomain.c.
755 floppy= [HW]
756 See Documentation/blockdev/floppy.txt.
758 force_pal_cache_flush
759 [IA-64] Avoid check_sal_cache_flush which may hang on
760 buggy SAL_CACHE_FLUSH implementations. Using this
761 parameter will force ia64_sal_cache_flush to call
762 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
764 ftrace=[tracer]
765 [FTRACE] will set and start the specified tracer
766 as early as possible in order to facilitate early
767 boot debugging.
769 ftrace_dump_on_oops
770 [FTRACE] will dump the trace buffers on oops.
772 ftrace_filter=[function-list]
773 [FTRACE] Limit the functions traced by the function
774 tracer at boot up. function-list is a comma separated
775 list of functions. This list can be changed at run
776 time by the set_ftrace_filter file in the debugfs
777 tracing directory.
779 ftrace_notrace=[function-list]
780 [FTRACE] Do not trace the functions specified in
781 function-list. This list can be changed at run time
782 by the set_ftrace_notrace file in the debugfs
783 tracing directory.
785 gamecon.map[2|3]=
786 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
787 support via parallel port (up to 5 devices per port)
788 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
789 See also Documentation/input/joystick-parport.txt
791 gamma= [HW,DRM]
793 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
794 Format: off | on
795 default: on
797 gcov_persist= [GCOV] When non-zero (default), profiling data for
798 kernel modules is saved and remains accessible via
799 debugfs, even when the module is unloaded/reloaded.
800 When zero, profiling data is discarded and associated
801 debugfs files are removed at module unload time.
803 gdth= [HW,SCSI]
804 See header of drivers/scsi/gdth.c.
806 gpt [EFI] Forces disk with valid GPT signature but
807 invalid Protective MBR to be treated as GPT.
809 gvp11= [HW,SCSI]
811 hashdist= [KNL,NUMA] Large hashes allocated during boot
812 are distributed across NUMA nodes. Defaults on
813 for 64bit NUMA, off otherwise.
814 Format: 0 | 1 (for off | on)
816 hcl= [IA-64] SGI's Hardware Graph compatibility layer
818 hd= [EIDE] (E)IDE hard drive subsystem geometry
819 Format: <cyl>,<head>,<sect>
821 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
822 size of <nn>. This works even on boxes that have no
823 highmem otherwise. This also works to reduce highmem
824 size on bigger boxes.
826 highres= [KNL] Enable/disable high resolution timer mode.
827 Valid parameters: "on", "off"
828 Default: "on"
830 hisax= [HW,ISDN]
831 See Documentation/isdn/README.HiSax.
833 hlt [BUGS=ARM,SH]
835 hpet= [X86-32,HPET] option to control HPET usage
836 Format: { enable (default) | disable | force |
837 verbose }
838 disable: disable HPET and use PIT instead
839 force: allow force enabled of undocumented chips (ICH4,
840 VIA, nVidia)
841 verbose: show contents of HPET registers during setup
843 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
844 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
845 On x86-64 and powerpc, this option can be specified
846 multiple times interleaved with hugepages= to reserve
847 huge pages of different sizes. Valid pages sizes on
848 x86-64 are 2M (when the CPU supports "pse") and 1G
849 (when the CPU supports the "pdpe1gb" cpuinfo flag)
850 Note that 1GB pages can only be allocated at boot time
851 using hugepages= and not freed afterwards.
853 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
854 terminal devices. Valid values: 0..8
855 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
856 If specified, z/VM IUCV HVC accepts connections
857 from listed z/VM user IDs only.
859 i2c_bus= [HW] Override the default board specific I2C bus speed
860 or register an additional I2C bus that is not
861 registered from board initialization code.
862 Format:
863 <bus_id>,<clkrate>
865 i8042.debug [HW] Toggle i8042 debug mode
866 i8042.direct [HW] Put keyboard port into non-translated mode
867 i8042.dumbkbd [HW] Pretend that controller can only read data from
868 keyboard and cannot control its state
869 (Don't attempt to blink the leds)
870 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
871 i8042.nokbd [HW] Don't check/create keyboard port
872 i8042.noloop [HW] Disable the AUX Loopback command while probing
873 for the AUX port
874 i8042.nomux [HW] Don't check presence of an active multiplexing
875 controller
876 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
877 controllers
878 i8042.panicblink=
879 [HW] Frequency with which keyboard LEDs should blink
880 when kernel panics (default is 0.5 sec)
881 i8042.reset [HW] Reset the controller during init and cleanup
882 i8042.unlock [HW] Unlock (ignore) the keylock
884 i810= [HW,DRM]
886 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
887 indicates that the driver is running on unsupported
888 hardware.
889 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
890 does not match list of supported models.
891 i8k.power_status
892 [HW] Report power status in /proc/i8k
893 (disabled by default)
894 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
895 capability is set.
897 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
898 See Documentation/mca.txt.
900 icn= [HW,ISDN]
901 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
903 ide-core.nodma= [HW] (E)IDE subsystem
904 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
905 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
906 .cdrom .chs .ignore_cable are additional options
907 See Documentation/ide/ide.txt.
909 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
910 Claim all unknown PCI IDE storage controllers.
912 idle= [X86]
913 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
914 Poll forces a polling idle loop that can slightly
915 improve the performance of waking up a idle CPU, but
916 will use a lot of power and make the system run hot.
917 Not recommended.
918 idle=mwait: On systems which support MONITOR/MWAIT but
919 the kernel chose to not use it because it doesn't save
920 as much power as a normal idle loop, use the
921 MONITOR/MWAIT idle loop anyways. Performance should be
922 the same as idle=poll.
923 idle=halt: Halt is forced to be used for CPU idle.
924 In such case C2/C3 won't be used again.
925 idle=nomwait: Disable mwait for CPU C-states
927 ignore_loglevel [KNL]
928 Ignore loglevel setting - this will print /all/
929 kernel messages to the console. Useful for debugging.
931 ihash_entries= [KNL]
932 Set number of hash buckets for inode cache.
934 ima_audit= [IMA]
935 Format: { "0" | "1" }
936 0 -- integrity auditing messages. (Default)
937 1 -- enable informational integrity auditing messages.
939 ima_hash= [IMA]
940 Format: { "sha1" | "md5" }
941 default: "sha1"
943 ima_tcb [IMA]
944 Load a policy which meets the needs of the Trusted
945 Computing Base. This means IMA will measure all
946 programs exec'd, files mmap'd for exec, and all files
947 opened for read by uid=0.
949 in2000= [HW,SCSI]
950 See header of drivers/scsi/in2000.c.
952 init= [KNL]
953 Format: <full_path>
954 Run specified binary instead of /sbin/init as init
955 process.
957 initcall_debug [KNL] Trace initcalls as they are executed. Useful
958 for working out where the kernel is dying during
959 startup.
961 initrd= [BOOT] Specify the location of the initial ramdisk
963 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
964 Format: <irq>
966 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
967 on
968 Enable intel iommu driver.
969 off
970 Disable intel iommu driver.
971 igfx_off [Default Off]
972 By default, gfx is mapped as normal device. If a gfx
973 device has a dedicated DMAR unit, the DMAR unit is
974 bypassed by not enabling DMAR with this option. In
975 this case, gfx device will use physical address for
976 DMA.
977 forcedac [x86_64]
978 With this option iommu will not optimize to look
979 for io virtual address below 32 bit forcing dual
980 address cycle on pci bus for cards supporting greater
981 than 32 bit addressing. The default is to look
982 for translation below 32 bit and if not available
983 then look in the higher range.
984 strict [Default Off]
985 With this option on every unmap_single operation will
986 result in a hardware IOTLB flush operation as opposed
987 to batching them for performance.
989 inttest= [IA64]
991 iomem= Disable strict checking of access to MMIO memory
992 strict regions from userspace.
993 relaxed
995 iommu= [x86]
996 off
997 force
998 noforce
999 biomerge
1000 panic
1001 nopanic
1002 merge
1003 nomerge
1004 forcesac
1005 soft
1006 pt [x86, IA64]
1008 io7= [HW] IO7 for Marvel based alpha systems
1009 See comment before marvel_specify_io7 in
1010 arch/alpha/kernel/core_marvel.c.
1012 io_delay= [X86] I/O delay method
1013 0x80
1014 Standard port 0x80 based delay
1015 0xed
1016 Alternate port 0xed based delay (needed on some systems)
1017 udelay
1018 Simple two microseconds delay
1019 none
1020 No delay
1022 ip= [IP_PNP]
1023 See Documentation/filesystems/nfsroot.txt.
1025 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1026 See comment before ip2_setup() in
1027 drivers/char/ip2/ip2base.c.
1029 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1030 See header of drivers/scsi/ips.c.
1032 irqfixup [HW]
1033 When an interrupt is not handled search all handlers
1034 for it. Intended to get systems with badly broken
1035 firmware running.
1037 irqpoll [HW]
1038 When an interrupt is not handled search all handlers
1039 for it. Also check all handlers each timer
1040 interrupt. Intended to get systems with badly broken
1041 firmware running.
1043 isapnp= [ISAPNP]
1044 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1046 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1047 Format:
1048 <cpu number>,...,<cpu number>
1049 or
1050 <cpu number>-<cpu number>
1051 (must be a positive range in ascending order)
1052 or a mixture
1053 <cpu number>,...,<cpu number>-<cpu number>
1055 This option can be used to specify one or more CPUs
1056 to isolate from the general SMP balancing and scheduling
1057 algorithms. You can move a process onto or off an
1058 "isolated" CPU via the CPU affinity syscalls or cpuset.
1059 <cpu number> begins at 0 and the maximum value is
1060 "number of CPUs in system - 1".
1062 This option is the preferred way to isolate CPUs. The
1063 alternative -- manually setting the CPU mask of all
1064 tasks in the system -- can cause problems and
1065 suboptimal load balancer performance.
1067 iucv= [HW,NET]
1069 js= [HW,JOY] Analog joystick
1070 See Documentation/input/joystick.txt.
1072 keepinitrd [HW,ARM]
1074 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1075 specifies the amount of memory usable by the kernel
1076 for non-movable allocations. The requested amount is
1077 spread evenly throughout all nodes in the system. The
1078 remaining memory in each node is used for Movable
1079 pages. In the event, a node is too small to have both
1080 kernelcore and Movable pages, kernelcore pages will
1081 take priority and other nodes will have a larger number
1082 of kernelcore pages. The Movable zone is used for the
1083 allocation of pages that may be reclaimed or moved
1084 by the page migration subsystem. This means that
1085 HugeTLB pages may not be allocated from this zone.
1086 Note that allocations like PTEs-from-HighMem still
1087 use the HighMem zone if it exists, and the Normal
1088 zone if it does not.
1090 kgdboc= [HW] kgdb over consoles.
1091 Requires a tty driver that supports console polling.
1092 (only serial supported for now)
1093 Format: <serial_device>[,baud]
1095 kmac= [MIPS] korina ethernet MAC address.
1096 Configure the RouterBoard 532 series on-chip
1097 Ethernet adapter MAC address.
1099 kmemleak= [KNL] Boot-time kmemleak enable/disable
1100 Valid arguments: on, off
1101 Default: on
1103 kstack=N [X86] Print N words from the kernel stack
1104 in oops dumps.
1106 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1107 Default is 0 (don't ignore, but inject #GP)
1109 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1110 Default is 1 (enabled)
1112 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1113 Default is 0 (off)
1115 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1116 for all guests.
1117 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1119 kvm-intel.bypass_guest_pf=
1120 [KVM,Intel] Disables bypassing of guest page faults
1121 on Intel chips. Default is 1 (enabled)
1123 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1124 (virtualized MMU) support on capable Intel chips.
1125 Default is 1 (enabled)
1127 kvm-intel.emulate_invalid_guest_state=
1128 [KVM,Intel] Enable emulation of invalid guest states
1129 Default is 0 (disabled)
1131 kvm-intel.flexpriority=
1132 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1133 Default is 1 (enabled)
1135 kvm-intel.unrestricted_guest=
1136 [KVM,Intel] Disable unrestricted guest feature
1137 (virtualized real and unpaged mode) on capable
1138 Intel chips. Default is 1 (enabled)
1140 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1141 feature (tagged TLBs) on capable Intel chips.
1142 Default is 1 (enabled)
1144 l2cr= [PPC]
1146 l3cr= [PPC]
1148 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1149 disabled it.
1151 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1152 in C2 power state.
1154 libata.dma= [LIBATA] DMA control
1155 libata.dma=0 Disable all PATA and SATA DMA
1156 libata.dma=1 PATA and SATA Disk DMA only
1157 libata.dma=2 ATAPI (CDROM) DMA only
1158 libata.dma=4 Compact Flash DMA only
1159 Combinations also work, so libata.dma=3 enables DMA
1160 for disks and CDROMs, but not CFs.
1162 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1163 libata.ignore_hpa=0 keep BIOS limits (default)
1164 libata.ignore_hpa=1 ignore limits, using full disk
1166 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1167 when set.
1168 Format: <int>
1170 libata.force= [LIBATA] Force configurations. The format is comma
1171 separated list of "[ID:]VAL" where ID is
1172 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1173 matching port, link or device. Basically, it matches
1174 the ATA ID string printed on console by libata. If
1175 the whole ID part is omitted, the last PORT and DEVICE
1176 values are used. If ID hasn't been specified yet, the
1177 configuration applies to all ports, links and devices.
1179 If only DEVICE is omitted, the parameter applies to
1180 the port and all links and devices behind it. DEVICE
1181 number of 0 either selects the first device or the
1182 first fan-out link behind PMP device. It does not
1183 select the host link. DEVICE number of 15 selects the
1184 host link and device attached to it.
1186 The VAL specifies the configuration to force. As long
1187 as there's no ambiguity shortcut notation is allowed.
1188 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1189 The following configurations can be forced.
1191 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1192 Any ID with matching PORT is used.
1194 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1196 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1197 udma[/][16,25,33,44,66,100,133] notation is also
1198 allowed.
1200 * [no]ncq: Turn on or off NCQ.
1202 * nohrst, nosrst, norst: suppress hard, soft
1203 and both resets.
1205 If there are multiple matching configurations changing
1206 the same attribute, the last one is used.
1208 lmb=debug [KNL] Enable lmb debug messages.
1210 load_ramdisk= [RAM] List of ramdisks to load from floppy
1211 See Documentation/blockdev/ramdisk.txt.
1213 lockd.nlm_grace_period=P [NFS] Assign grace period.
1214 Format: <integer>
1216 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1217 Format: <integer>
1219 lockd.nlm_timeout=T [NFS] Assign timeout value.
1220 Format: <integer>
1222 lockd.nlm_udpport=M [NFS] Assign UDP port.
1223 Format: <integer>
1225 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1226 Format: <irq>
1228 loglevel= All Kernel Messages with a loglevel smaller than the
1229 console loglevel will be printed to the console. It can
1230 also be changed with klogd or other programs. The
1231 loglevels are defined as follows:
1233 0 (KERN_EMERG) system is unusable
1234 1 (KERN_ALERT) action must be taken immediately
1235 2 (KERN_CRIT) critical conditions
1236 3 (KERN_ERR) error conditions
1237 4 (KERN_WARNING) warning conditions
1238 5 (KERN_NOTICE) normal but significant condition
1239 6 (KERN_INFO) informational
1240 7 (KERN_DEBUG) debug-level messages
1242 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1243 Format: { n | nk | nM }
1244 n must be a power of two. The default size
1245 is set in the kernel config file.
1247 logo.nologo [FB] Disables display of the built-in Linux logo.
1248 This may be used to provide more screen space for
1249 kernel log messages and is useful when debugging
1250 kernel boot problems.
1252 lp=0 [LP] Specify parallel ports to use, e.g,
1253 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1254 lp=reset first parallel port). 'lp=0' disables the
1255 lp=auto printer driver. 'lp=reset' (which can be
1256 specified in addition to the ports) causes
1257 attached printers to be reset. Using
1258 lp=port1,port2,... specifies the parallel ports
1259 to associate lp devices with, starting with
1260 lp0. A port specification may be 'none' to skip
1261 that lp device, or a parport name such as
1262 'parport0'. Specifying 'lp=auto' instead of a
1263 port specification list means that device IDs
1264 from each port should be examined, to see if
1265 an IEEE 1284-compliant printer is attached; if
1266 so, the driver will manage that printer.
1267 See also header of drivers/char/lp.c.
1269 lpj=n [KNL]
1270 Sets loops_per_jiffy to given constant, thus avoiding
1271 time-consuming boot-time autodetection (up to 250 ms per
1272 CPU). 0 enables autodetection (default). To determine
1273 the correct value for your kernel, boot with normal
1274 autodetection and see what value is printed. Note that
1275 on SMP systems the preset will be applied to all CPUs,
1276 which is likely to cause problems if your CPUs need
1277 significantly divergent settings. An incorrect value
1278 will cause delays in the kernel to be wrong, leading to
1279 unpredictable I/O errors and other breakage. Although
1280 unlikely, in the extreme case this might damage your
1281 hardware.
1283 ltpc= [NET]
1284 Format: <io>,<irq>,<dma>
1286 mac5380= [HW,SCSI] Format:
1287 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1289 machvec= [IA64] Force the use of a particular machine-vector
1290 (machvec) in a generic kernel.
1291 Example: machvec=hpzx1_swiotlb
1293 machtype= [Loongson] Share the same kernel image file between different
1294 yeeloong laptop.
1295 Example: machtype=lemote-yeeloong-2f-7inch
1297 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1298 than or equal to this physical address is ignored.
1300 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1301 should make use of. maxcpus=n : n >= 0 limits the
1302 kernel to using 'n' processors. n=0 is a special case,
1303 it is equivalent to "nosmp", which also disables
1304 the IO APIC.
1306 max_loop= [LOOP] Maximum number of loopback devices that can
1307 be mounted
1308 Format: <1-256>
1310 max_luns= [SCSI] Maximum number of LUNs to probe.
1311 Should be between 1 and 2^32-1.
1313 max_report_luns=
1314 [SCSI] Maximum number of LUNs received.
1315 Should be between 1 and 16384.
1317 mcatest= [IA-64]
1319 mce [X86-32] Machine Check Exception
1321 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1323 md= [HW] RAID subsystems devices and level
1324 See Documentation/md.txt.
1326 mdacon= [MDA]
1327 Format: <first>,<last>
1328 Specifies range of consoles to be captured by the MDA.
1330 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1331 Amount of memory to be used when the kernel is not able
1332 to see the whole system memory or for test.
1333 [X86-32] Use together with memmap= to avoid physical
1334 address space collisions. Without memmap= PCI devices
1335 could be placed at addresses belonging to unused RAM.
1337 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1338 memory.
1340 memchunk=nn[KMG]
1341 [KNL,SH] Allow user to override the default size for
1342 per-device physically contiguous DMA buffers.
1344 memmap=exactmap [KNL,X86] Enable setting of an exact
1345 E820 memory map, as specified by the user.
1346 Such memmap=exactmap lines can be constructed based on
1347 BIOS output or other requirements. See the memmap=nn@ss
1348 option description.
1350 memmap=nn[KMG]@ss[KMG]
1351 [KNL] Force usage of a specific region of memory
1352 Region of memory to be used, from ss to ss+nn.
1354 memmap=nn[KMG]#ss[KMG]
1355 [KNL,ACPI] Mark specific memory as ACPI data.
1356 Region of memory to be used, from ss to ss+nn.
1358 memmap=nn[KMG]$ss[KMG]
1359 [KNL,ACPI] Mark specific memory as reserved.
1360 Region of memory to be used, from ss to ss+nn.
1361 Example: Exclude memory from 0x18690000-0x1869ffff
1362 memmap=64K$0x18690000
1363 or
1364 memmap=0x10000$0x18690000
1366 memory_corruption_check=0/1 [X86]
1367 Some BIOSes seem to corrupt the first 64k of
1368 memory when doing things like suspend/resume.
1369 Setting this option will scan the memory
1370 looking for corruption. Enabling this will
1371 both detect corruption and prevent the kernel
1372 from using the memory being corrupted.
1373 However, its intended as a diagnostic tool; if
1374 repeatable BIOS-originated corruption always
1375 affects the same memory, you can use memmap=
1376 to prevent the kernel from using that memory.
1378 memory_corruption_check_size=size [X86]
1379 By default it checks for corruption in the low
1380 64k, making this memory unavailable for normal
1381 use. Use this parameter to scan for
1382 corruption in more or less memory.
1384 memory_corruption_check_period=seconds [X86]
1385 By default it checks for corruption every 60
1386 seconds. Use this parameter to check at some
1387 other rate. 0 disables periodic checking.
1389 memtest= [KNL,X86] Enable memtest
1390 Format: <integer>
1391 default : 0 <disable>
1392 Specifies the number of memtest passes to be
1393 performed. Each pass selects another test
1394 pattern from a given set of patterns. Memtest
1395 fills the memory with this pattern, validates
1396 memory contents and reserves bad memory
1397 regions that are detected.
1399 meye.*= [HW] Set MotionEye Camera parameters
1400 See Documentation/video4linux/meye.txt.
1402 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1403 Multi-Function General Purpose Timers on AMD Geode
1404 platforms.
1406 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1407 the BIOS has incorrectly applied a workaround. TinyBIOS
1408 version 0.98 is known to be affected, 0.99 fixes the
1409 problem by letting the user disable the workaround.
1411 mga= [HW,DRM]
1413 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1414 physical address is ignored.
1416 mini2440= [ARM,HW,KNL]
1417 Format:[0..2][b][c][t]
1418 Default: "0tb"
1419 MINI2440 configuration specification:
1420 0 - The attached screen is the 3.5" TFT
1421 1 - The attached screen is the 7" TFT
1422 2 - The VGA Shield is attached (1024x768)
1423 Leaving out the screen size parameter will not load
1424 the TFT driver, and the framebuffer will be left
1425 unconfigured.
1426 b - Enable backlight. The TFT backlight pin will be
1427 linked to the kernel VESA blanking code and a GPIO
1428 LED. This parameter is not necessary when using the
1429 VGA shield.
1430 c - Enable the s3c camera interface.
1431 t - Reserved for enabling touchscreen support. The
1432 touchscreen support is not enabled in the mainstream
1433 kernel as of 2.6.30, a preliminary port can be found
1434 in the "bleeding edge" mini2440 support kernel at
1435 http://repo.or.cz/w/linux-2.6/mini2440.git
1437 mminit_loglevel=
1438 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1439 parameter allows control of the logging verbosity for
1440 the additional memory initialisation checks. A value
1441 of 0 disables mminit logging and a level of 4 will
1442 log everything. Information is printed at KERN_DEBUG
1443 so loglevel=8 may also need to be specified.
1445 mousedev.tap_time=
1446 [MOUSE] Maximum time between finger touching and
1447 leaving touchpad surface for touch to be considered
1448 a tap and be reported as a left button click (for
1449 touchpads working in absolute mode only).
1450 Format: <msecs>
1451 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1452 reporting absolute coordinates, such as tablets
1453 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1454 reporting absolute coordinates, such as tablets
1456 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1457 is similar to kernelcore except it specifies the
1458 amount of memory used for migratable allocations.
1459 If both kernelcore and movablecore is specified,
1460 then kernelcore will be at *least* the specified
1461 value but may be more. If movablecore on its own
1462 is specified, the administrator must be careful
1463 that the amount of memory usable for all allocations
1464 is not too small.
1466 mpu401= [HW,OSS]
1467 Format: <io>,<irq>
1469 MTD_Partition= [MTD]
1470 Format: <name>,<region-number>,<size>,<offset>
1472 MTD_Region= [MTD] Format:
1473 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1475 mtdparts= [MTD]
1476 See drivers/mtd/cmdlinepart.c.
1478 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1480 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1482 boundary - index of last SLC block on Flex-OneNAND.
1483 The remaining blocks are configured as MLC blocks.
1484 lock - Configure if Flex-OneNAND boundary should be locked.
1485 Once locked, the boundary cannot be changed.
1486 1 indicates lock status, 0 indicates unlock status.
1488 mtdset= [ARM]
1489 ARM/S3C2412 JIVE boot control
1491 See arch/arm/mach-s3c2412/mach-jive.c
1493 mtouchusb.raw_coordinates=
1494 [HW] Make the MicroTouch USB driver use raw coordinates
1495 ('y', default) or cooked coordinates ('n')
1497 mtrr_chunk_size=nn[KMG] [X86]
1498 used for mtrr cleanup. It is largest continuous chunk
1499 that could hold holes aka. UC entries.
1501 mtrr_gran_size=nn[KMG] [X86]
1502 Used for mtrr cleanup. It is granularity of mtrr block.
1503 Default is 1.
1504 Large value could prevent small alignment from
1505 using up MTRRs.
1507 mtrr_spare_reg_nr=n [X86]
1508 Format: <integer>
1509 Range: 0,7 : spare reg number
1510 Default : 1
1511 Used for mtrr cleanup. It is spare mtrr entries number.
1512 Set to 2 or more if your graphical card needs more.
1514 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1516 NCR_D700= [HW,SCSI]
1517 See header of drivers/scsi/NCR_D700.c.
1519 ncr5380= [HW,SCSI]
1521 ncr53c400= [HW,SCSI]
1523 ncr53c400a= [HW,SCSI]
1525 ncr53c406a= [HW,SCSI]
1527 ncr53c8xx= [HW,SCSI]
1529 netdev= [NET] Network devices parameters
1530 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1531 Note that mem_start is often overloaded to mean
1532 something different and driver-specific.
1533 This usage is only documented in each driver source
1534 file if at all.
1536 nf_conntrack.acct=
1537 [NETFILTER] Enable connection tracking flow accounting
1538 0 to disable accounting
1539 1 to enable accounting
1540 Default value depends on CONFIG_NF_CT_ACCT that is
1541 going to be removed in 2.6.29.
1543 nfsaddrs= [NFS]
1544 See Documentation/filesystems/nfsroot.txt.
1546 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1547 See Documentation/filesystems/nfsroot.txt.
1549 nfs.callback_tcpport=
1550 [NFS] set the TCP port on which the NFSv4 callback
1551 channel should listen.
1553 nfs.cache_getent=
1554 [NFS] sets the pathname to the program which is used
1555 to update the NFS client cache entries.
1557 nfs.cache_getent_timeout=
1558 [NFS] sets the timeout after which an attempt to
1559 update a cache entry is deemed to have failed.
1561 nfs.idmap_cache_timeout=
1562 [NFS] set the maximum lifetime for idmapper cache
1563 entries.
1565 nfs.enable_ino64=
1566 [NFS] enable 64-bit inode numbers.
1567 If zero, the NFS client will fake up a 32-bit inode
1568 number for the readdir() and stat() syscalls instead
1569 of returning the full 64-bit number.
1570 The default is to return 64-bit inode numbers.
1572 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1573 when a NMI is triggered.
1574 Format: [state][,regs][,debounce][,die]
1576 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1577 Format: [panic,][num]
1578 Valid num: 0,1,2
1579 0 - turn nmi_watchdog off
1580 1 - use the IO-APIC timer for the NMI watchdog
1581 2 - use the local APIC for the NMI watchdog using
1582 a performance counter. Note: This will use one
1583 performance counter and the local APIC's performance
1584 vector.
1585 When panic is specified, panic when an NMI watchdog
1586 timeout occurs.
1587 This is useful when you use a panic=... timeout and
1588 need the box quickly up again.
1589 Instead of 1 and 2 it is possible to use the following
1590 symbolic names: lapic and ioapic
1591 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1593 netpoll.carrier_timeout=
1594 [NET] Specifies amount of time (in seconds) that
1595 netpoll should wait for a carrier. By default netpoll
1596 waits 4 seconds.
1598 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1599 emulation library even if a 387 maths coprocessor
1600 is present.
1602 no_console_suspend
1603 [HW] Never suspend the console
1604 Disable suspending of consoles during suspend and
1605 hibernate operations. Once disabled, debugging
1606 messages can reach various consoles while the rest
1607 of the system is being put to sleep (ie, while
1608 debugging driver suspend/resume hooks). This may
1609 not work reliably with all consoles, but is known
1610 to work with serial and VGA consoles.
1612 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1613 caches in the slab allocator. Saves per-node memory,
1614 but will impact performance.
1616 noalign [KNL,ARM]
1618 noapic [SMP,APIC] Tells the kernel to not make use of any
1619 IOAPICs that may be present in the system.
1621 nobats [PPC] Do not use BATs for mapping kernel lowmem
1622 on "Classic" PPC cores.
1624 nocache [ARM]
1626 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1628 nodelayacct [KNL] Disable per-task delay accounting
1630 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1632 nodsp [SH] Disable hardware DSP at boot time.
1634 noefi [X86] Disable EFI runtime services support.
1636 noexec [IA-64]
1638 noexec [X86]
1639 On X86-32 available only on PAE configured kernels.
1640 noexec=on: enable non-executable mappings (default)
1641 noexec=off: disable non-executable mappings
1643 noexec32 [X86-64]
1644 This affects only 32-bit executables.
1645 noexec32=on: enable non-executable mappings (default)
1646 read doesn't imply executable mappings
1647 noexec32=off: disable non-executable mappings
1648 read implies executable mappings
1650 nofpu [SH] Disable hardware FPU at boot time.
1652 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1653 register save and restore. The kernel will only save
1654 legacy floating-point registers on task switch.
1656 noxsave [BUGS=X86] Disables x86 extended register state save
1657 and restore using xsave. The kernel will fallback to
1658 enabling legacy floating-point and sse state.
1660 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1661 wfi(ARM) instruction doesn't work correctly and not to
1662 use it. This is also useful when using JTAG debugger.
1664 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1665 instruction doesn't work correctly and not to
1666 use it.
1668 no_file_caps Tells the kernel not to honor file capabilities. The
1669 only way then for a file to be executed with privilege
1670 is to be setuid root or executed by root.
1672 nohalt [IA-64] Tells the kernel not to use the power saving
1673 function PAL_HALT_LIGHT when idle. This increases
1674 power-consumption. On the positive side, it reduces
1675 interrupt wake-up latency, which may improve performance
1676 in certain environments such as networked servers or
1677 real-time systems.
1679 nohz= [KNL] Boottime enable/disable dynamic ticks
1680 Valid arguments: on, off
1681 Default: on
1683 noiotrap [SH] Disables trapped I/O port accesses.
1685 noirqdebug [X86-32] Disables the code which attempts to detect and
1686 disable unhandled interrupt sources.
1688 no_timer_check [X86,APIC] Disables the code which tests for
1689 broken timer IRQ sources.
1691 noisapnp [ISAPNP] Disables ISA PnP code.
1693 noinitrd [RAM] Tells the kernel not to load any configured
1694 initial RAM disk.
1696 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1697 remapping.
1699 nointroute [IA-64]
1701 nojitter [IA64] Disables jitter checking for ITC timers.
1703 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1705 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1707 noltlbs [PPC] Do not use large page/tlb entries for kernel
1708 lowmem mapping on PPC40x.
1710 nomca [IA-64] Disable machine check abort handling
1712 nomce [X86-32] Machine Check Exception
1714 nomfgpt [X86-32] Disable Multi-Function General Purpose
1715 Timer usage (for AMD Geode machines).
1717 norandmaps Don't use address space randomization. Equivalent to
1718 echo 0 > /proc/sys/kernel/randomize_va_space
1720 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1722 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1723 with UP alternatives
1725 noresidual [PPC] Don't use residual data on PReP machines.
1727 noresume [SWSUSP] Disables resume and restores original swap
1728 space.
1730 no-scroll [VGA] Disables scrollback.
1731 This is required for the Braillex ib80-piezo Braille
1732 reader made by F.H. Papenmeier (Germany).
1734 nosbagart [IA-64]
1736 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1738 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1739 and disable the IO APIC. legacy for "maxcpus=0".
1741 nosoftlockup [KNL] Disable the soft-lockup detector.
1743 noswapaccount [KNL] Disable accounting of swap in memory resource
1744 controller. (See Documentation/cgroups/memory.txt)
1746 nosync [HW,M68K] Disables sync negotiation for all devices.
1748 notsc [BUGS=X86-32] Disable Time Stamp Counter
1750 nousb [USB] Disable the USB subsystem
1752 nowb [ARM]
1754 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1756 nptcg= [IA64] Override max number of concurrent global TLB
1757 purges which is reported from either PAL_VM_SUMMARY or
1758 SAL PALO.
1760 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1762 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1763 one of ['zone', 'node', 'default'] can be specified
1764 This can be set from sysctl after boot.
1765 See Documentation/sysctl/vm.txt for details.
1767 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1768 See Documentation/debugging-via-ohci1394.txt for more
1769 info.
1771 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1772 Rather than timing out after 20 ms if an EC
1773 command is not properly ACKed, override the length
1774 of the timeout. We have interrupts disabled while
1775 waiting for the ACK, so if this is set too high
1776 interrupts *may* be lost!
1778 opl3= [HW,OSS]
1779 Format: <io>
1781 oprofile.timer= [HW]
1782 Use timer interrupt instead of performance counters
1784 oprofile.cpu_type= Force an oprofile cpu type
1785 This might be useful if you have an older oprofile
1786 userland or if you want common events.
1787 Format: { arch_perfmon }
1788 arch_perfmon: [X86] Force use of architectural
1789 perfmon on Intel CPUs instead of the
1790 CPU specific event set.
1792 osst= [HW,SCSI] SCSI Tape Driver
1793 Format: <buffer_size>,<write_threshold>
1794 See also Documentation/scsi/st.txt.
1796 panic= [KNL] Kernel behaviour on panic
1797 Format: <timeout>
1799 parkbd.port= [HW] Parallel port number the keyboard adapter is
1800 connected to, default is 0.
1801 Format: <parport#>
1802 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1803 0 for XT, 1 for AT (default is AT).
1804 Format: <mode>
1806 parport= [HW,PPT] Specify parallel ports. 0 disables.
1807 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1808 Use 'auto' to force the driver to use any
1809 IRQ/DMA settings detected (the default is to
1810 ignore detected IRQ/DMA settings because of
1811 possible conflicts). You can specify the base
1812 address, IRQ, and DMA settings; IRQ and DMA
1813 should be numbers, or 'auto' (for using detected
1814 settings on that particular port), or 'nofifo'
1815 (to avoid using a FIFO even if it is detected).
1816 Parallel ports are assigned in the order they
1817 are specified on the command line, starting
1818 with parport0.
1820 parport_init_mode= [HW,PPT]
1821 Configure VIA parallel port to operate in
1822 a specific mode. This is necessary on Pegasos
1823 computer where firmware has no options for setting
1824 up parallel port mode and sets it to spp.
1825 Currently this function knows 686a and 8231 chips.
1826 Format: [spp|ps2|epp|ecp|ecpepp]
1828 pas2= [HW,OSS] Format:
1829 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1831 pas16= [HW,SCSI]
1832 See header of drivers/scsi/pas16.c.
1834 pause_on_oops=
1835 Halt all CPUs after the first oops has been printed for
1836 the specified number of seconds. This is to be used if
1837 your oopses keep scrolling off the screen.
1839 pcbit= [HW,ISDN]
1841 pcd. [PARIDE]
1842 See header of drivers/block/paride/pcd.c.
1843 See also Documentation/blockdev/paride.txt.
1845 pci=option[,option...] [PCI] various PCI subsystem options:
1846 earlydump [X86] dump PCI config space before the kernel
1847 changes anything
1848 off [X86] don't probe for the PCI bus
1849 bios [X86-32] force use of PCI BIOS, don't access
1850 the hardware directly. Use this if your machine
1851 has a non-standard PCI host bridge.
1852 nobios [X86-32] disallow use of PCI BIOS, only direct
1853 hardware access methods are allowed. Use this
1854 if you experience crashes upon bootup and you
1855 suspect they are caused by the BIOS.
1856 conf1 [X86] Force use of PCI Configuration
1857 Mechanism 1.
1858 conf2 [X86] Force use of PCI Configuration
1859 Mechanism 2.
1860 noaer [PCIE] If the PCIEAER kernel config parameter is
1861 enabled, this kernel boot option can be used to
1862 disable the use of PCIE advanced error reporting.
1863 nodomains [PCI] Disable support for multiple PCI
1864 root domains (aka PCI segments, in ACPI-speak).
1865 nommconf [X86] Disable use of MMCONFIG for PCI
1866 Configuration
1867 check_enable_amd_mmconf [X86] check for and enable
1868 properly configured MMIO access to PCI
1869 config space on AMD family 10h CPU
1870 nomsi [MSI] If the PCI_MSI kernel config parameter is
1871 enabled, this kernel boot option can be used to
1872 disable the use of MSI interrupts system-wide.
1873 noioapicquirk [APIC] Disable all boot interrupt quirks.
1874 Safety option to keep boot IRQs enabled. This
1875 should never be necessary.
1876 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1877 primary IO-APIC for bridges that cannot disable
1878 boot IRQs. This fixes a source of spurious IRQs
1879 when the system masks IRQs.
1880 noioapicreroute [APIC] Disable workaround that uses the
1881 boot IRQ equivalent of an IRQ that connects to
1882 a chipset where boot IRQs cannot be disabled.
1883 The opposite of ioapicreroute.
1884 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1885 routing table. These calls are known to be buggy
1886 on several machines and they hang the machine
1887 when used, but on other computers it's the only
1888 way to get the interrupt routing table. Try
1889 this option if the kernel is unable to allocate
1890 IRQs or discover secondary PCI buses on your
1891 motherboard.
1892 rom [X86] Assign address space to expansion ROMs.
1893 Use with caution as certain devices share
1894 address decoders between ROMs and other
1895 resources.
1896 norom [X86] Do not assign address space to
1897 expansion ROMs that do not already have
1898 BIOS assigned address ranges.
1899 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1900 assigned automatically to PCI devices. You can
1901 make the kernel exclude IRQs of your ISA cards
1902 this way.
1903 pirqaddr=0xAAAAA [X86] Specify the physical address
1904 of the PIRQ table (normally generated
1905 by the BIOS) if it is outside the
1906 F0000h-100000h range.
1907 lastbus=N [X86] Scan all buses thru bus #N. Can be
1908 useful if the kernel is unable to find your
1909 secondary buses and you want to tell it
1910 explicitly which ones they are.
1911 assign-busses [X86] Always assign all PCI bus
1912 numbers ourselves, overriding
1913 whatever the firmware may have done.
1914 usepirqmask [X86] Honor the possible IRQ mask stored
1915 in the BIOS $PIR table. This is needed on
1916 some systems with broken BIOSes, notably
1917 some HP Pavilion N5400 and Omnibook XE3
1918 notebooks. This will have no effect if ACPI
1919 IRQ routing is enabled.
1920 noacpi [X86] Do not use ACPI for IRQ routing
1921 or for PCI scanning.
1922 use_crs [X86] Use _CRS for PCI resource
1923 allocation.
1924 routeirq Do IRQ routing for all PCI devices.
1925 This is normally done in pci_enable_device(),
1926 so this option is a temporary workaround
1927 for broken drivers that don't call it.
1928 skip_isa_align [X86] do not align io start addr, so can
1929 handle more pci cards
1930 firmware [ARM] Do not re-enumerate the bus but instead
1931 just use the configuration from the
1932 bootloader. This is currently used on
1933 IXP2000 systems where the bus has to be
1934 configured a certain way for adjunct CPUs.
1935 noearly [X86] Don't do any early type 1 scanning.
1936 This might help on some broken boards which
1937 machine check when some devices' config space
1938 is read. But various workarounds are disabled
1939 and some IOMMU drivers will not work.
1940 bfsort Sort PCI devices into breadth-first order.
1941 This sorting is done to get a device
1942 order compatible with older (<= 2.4) kernels.
1943 nobfsort Don't sort PCI devices into breadth-first order.
1944 cbiosize=nn[KMG] The fixed amount of bus space which is
1945 reserved for the CardBus bridge's IO window.
1946 The default value is 256 bytes.
1947 cbmemsize=nn[KMG] The fixed amount of bus space which is
1948 reserved for the CardBus bridge's memory
1949 window. The default value is 64 megabytes.
1950 resource_alignment=
1951 Format:
1952 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1953 Specifies alignment and device to reassign
1954 aligned memory resources.
1955 If <order of align> is not specified,
1956 PAGE_SIZE is used as alignment.
1957 PCI-PCI bridge can be specified, if resource
1958 windows need to be expanded.
1959 ecrc= Enable/disable PCIe ECRC (transaction layer
1960 end-to-end CRC checking).
1961 bios: Use BIOS/firmware settings. This is the
1962 the default.
1963 off: Turn ECRC off
1964 on: Turn ECRC on.
1966 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1967 Management.
1968 off Disable ASPM.
1969 force Enable ASPM even on devices that claim not to support it.
1970 WARNING: Forcing ASPM on may cause system lockups.
1972 pcmv= [HW,PCMCIA] BadgePAD 4
1974 pd. [PARIDE]
1975 See Documentation/blockdev/paride.txt.
1977 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1978 boot time.
1979 Format: { 0 | 1 }
1980 See arch/parisc/kernel/pdc_chassis.c
1982 percpu_alloc= Select which percpu first chunk allocator to use.
1983 Currently supported values are "embed" and "page".
1984 Archs may support subset or none of the selections.
1985 See comments in mm/percpu.c for details on each
1986 allocator. This parameter is primarily for debugging
1987 and performance comparison.
1989 pf. [PARIDE]
1990 See Documentation/blockdev/paride.txt.
1992 pg. [PARIDE]
1993 See Documentation/blockdev/paride.txt.
1995 pirq= [SMP,APIC] Manual mp-table setup
1996 See Documentation/x86/i386/IO-APIC.txt.
1998 plip= [PPT,NET] Parallel port network link
1999 Format: { parport<nr> | timid | 0 }
2000 See also Documentation/parport.txt.
2002 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2003 Override pmtimer IOPort with a hex value.
2004 e.g. pmtmr=0x508
2006 pnp.debug [PNP]
2007 Enable PNP debug messages. This depends on the
2008 CONFIG_PNP_DEBUG_MESSAGES option.
2010 pnpacpi= [ACPI]
2011 { off }
2013 pnpbios= [ISAPNP]
2014 { on | off | curr | res | no-curr | no-res }
2016 pnp_reserve_irq=
2017 [ISAPNP] Exclude IRQs for the autoconfiguration
2019 pnp_reserve_dma=
2020 [ISAPNP] Exclude DMAs for the autoconfiguration
2022 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2023 Ranges are in pairs (I/O port base and size).
2025 pnp_reserve_mem=
2026 [ISAPNP] Exclude memory regions for the
2027 autoconfiguration.
2028 Ranges are in pairs (memory base and size).
2030 ports= [IP_VS_FTP] IPVS ftp helper module
2031 Default is 21.
2032 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2033 may be specified.
2034 Format: <port>,<port>....
2036 print-fatal-signals=
2037 [KNL] debug: print fatal signals
2038 print-fatal-signals=1: print segfault info to
2039 the kernel console.
2040 default: off.
2042 printk.time= Show timing data prefixed to each printk message line
2043 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2045 processor.max_cstate= [HW,ACPI]
2046 Limit processor to maximum C-state
2047 max_cstate=9 overrides any DMI blacklist limit.
2049 processor.nocst [HW,ACPI]
2050 Ignore the _CST method to determine C-states,
2051 instead using the legacy FADT method
2053 profile= [KNL] Enable kernel profiling via /proc/profile
2054 Format: [schedule,]<number>
2055 Param: "schedule" - profile schedule points.
2056 Param: <number> - step/bucket size as a power of 2 for
2057 statistical time based profiling.
2058 Param: "sleep" - profile D-state sleeping (millisecs).
2059 Requires CONFIG_SCHEDSTATS
2060 Param: "kvm" - profile VM exits.
2062 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2063 before loading.
2064 See Documentation/blockdev/ramdisk.txt.
2066 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2067 probe for; one of (bare|imps|exps|lifebook|any).
2068 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2069 per second.
2070 psmouse.resetafter= [HW,MOUSE]
2071 Try to reset the device after so many bad packets
2072 (0 = never).
2073 psmouse.resolution=
2074 [HW,MOUSE] Set desired mouse resolution, in dpi.
2075 psmouse.smartscroll=
2076 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2077 0 = disabled, 1 = enabled (default).
2079 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2080 Format:
2081 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2083 pt. [PARIDE]
2084 See Documentation/blockdev/paride.txt.
2086 pty.legacy_count=
2087 [KNL] Number of legacy pty's. Overwrites compiled-in
2088 default number.
2090 quiet [KNL] Disable most log messages
2092 r128= [HW,DRM]
2094 raid= [HW,RAID]
2095 See Documentation/md.txt.
2097 ramdisk_blocksize= [RAM]
2098 See Documentation/blockdev/ramdisk.txt.
2100 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2101 See Documentation/blockdev/ramdisk.txt.
2103 rcupdate.blimit= [KNL,BOOT]
2104 Set maximum number of finished RCU callbacks to process
2105 in one batch.
2107 rcupdate.qhimark= [KNL,BOOT]
2108 Set threshold of queued
2109 RCU callbacks over which batch limiting is disabled.
2111 rcupdate.qlowmark= [KNL,BOOT]
2112 Set threshold of queued RCU callbacks below which
2113 batch limiting is re-enabled.
2115 rdinit= [KNL]
2116 Format: <full_path>
2117 Run specified binary instead of /init from the ramdisk,
2118 used for early userspace startup. See initrd.
2120 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2121 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2122 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2124 relax_domain_level=
2125 [KNL, SMP] Set scheduler's default relax_domain_level.
2126 See Documentation/cgroups/cpusets.txt.
2128 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2130 reservetop= [X86-32]
2131 Format: nn[KMG]
2132 Reserves a hole at the top of the kernel virtual
2133 address space.
2135 reset_devices [KNL] Force drivers to reset the underlying device
2136 during initialization.
2138 resume= [SWSUSP]
2139 Specify the partition device for software suspend
2141 resume_offset= [SWSUSP]
2142 Specify the offset from the beginning of the partition
2143 given by "resume=" at which the swap header is located,
2144 in <PAGE_SIZE> units (needed only for swap files).
2145 See Documentation/power/swsusp-and-swap-files.txt
2147 retain_initrd [RAM] Keep initrd memory after extraction
2149 rhash_entries= [KNL,NET]
2150 Set number of hash buckets for route cache
2152 riscom8= [HW,SERIAL]
2153 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2155 ro [KNL] Mount root device read-only on boot
2157 root= [KNL] Root filesystem
2159 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2160 mount the root filesystem
2162 rootflags= [KNL] Set root filesystem mount option string
2164 rootfstype= [KNL] Set root filesystem type
2166 rootwait [KNL] Wait (indefinitely) for root device to show up.
2167 Useful for devices that are detected asynchronously
2168 (e.g. USB and MMC devices).
2170 root_plug.vendor_id=
2171 [ROOTPLUG] Override the default vendor ID
2173 root_plug.product_id=
2174 [ROOTPLUG] Override the default product ID
2176 root_plug.debug=
2177 [ROOTPLUG] Enable debugging output
2179 rw [KNL] Mount root device read-write on boot
2181 S [KNL] Run init in single mode
2183 sa1100ir [NET]
2184 See drivers/net/irda/sa1100_ir.c.
2186 sbni= [NET] Granch SBNI12 leased line adapter
2188 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2189 Format: <io>[,<timeout>[,<isapnp>]]
2191 scsi_debug_*= [SCSI]
2192 See drivers/scsi/scsi_debug.c.
2194 scsi_default_dev_flags=
2195 [SCSI] SCSI default device flags
2196 Format: <integer>
2198 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2199 Format: <vendor>:<model>:<flags>
2200 (flags are integer value)
2202 scsi_logging_level= [SCSI] a bit mask of logging levels
2203 See drivers/scsi/scsi_logging.h for bits. Also
2204 settable via sysctl at dev.scsi.logging_level
2205 (/proc/sys/dev/scsi/logging_level).
2206 There is also a nice 'scsi_logging_level' script in the
2207 S390-tools package, available for download at
2208 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2210 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2211 discovered. async scans them in kernel threads,
2212 allowing boot to proceed. none ignores them, expecting
2213 user space to do the scan.
2215 security= [SECURITY] Choose a security module to enable at boot.
2216 If this boot parameter is not specified, only the first
2217 security module asking for security registration will be
2218 loaded. An invalid security module name will be treated
2219 as if no module has been chosen.
2221 selinux= [SELINUX] Disable or enable SELinux at boot time.
2222 Format: { "0" | "1" }
2223 See security/selinux/Kconfig help text.
2224 0 -- disable.
2225 1 -- enable.
2226 Default value is set via kernel config option.
2227 If enabled at boot time, /selinux/disable can be used
2228 later to disable prior to initial policy load.
2230 serialnumber [BUGS=X86-32]
2232 shapers= [NET]
2233 Maximal number of shapers.
2235 show_msr= [x86] show boot-time MSR settings
2236 Format: { <integer> }
2237 Show boot-time (BIOS-initialized) MSR settings.
2238 The parameter means the number of CPUs to show,
2239 for example 1 means boot CPU only.
2241 sim710= [SCSI,HW]
2242 See header of drivers/scsi/sim710.c.
2244 simeth= [IA-64]
2245 simscsi=
2247 slram= [HW,MTD]
2249 slub_debug[=options[,slabs]] [MM, SLUB]
2250 Enabling slub_debug allows one to determine the
2251 culprit if slab objects become corrupted. Enabling
2252 slub_debug can create guard zones around objects and
2253 may poison objects when not in use. Also tracks the
2254 last alloc / free. For more information see
2255 Documentation/vm/slub.txt.
2257 slub_max_order= [MM, SLUB]
2258 Determines the maximum allowed order for slabs.
2259 A high setting may cause OOMs due to memory
2260 fragmentation. For more information see
2261 Documentation/vm/slub.txt.
2263 slub_min_objects= [MM, SLUB]
2264 The minimum number of objects per slab. SLUB will
2265 increase the slab order up to slub_max_order to
2266 generate a sufficiently large slab able to contain
2267 the number of objects indicated. The higher the number
2268 of objects the smaller the overhead of tracking slabs
2269 and the less frequently locks need to be acquired.
2270 For more information see Documentation/vm/slub.txt.
2272 slub_min_order= [MM, SLUB]
2273 Determines the mininum page order for slabs. Must be
2274 lower than slub_max_order.
2275 For more information see Documentation/vm/slub.txt.
2277 slub_nomerge [MM, SLUB]
2278 Disable merging of slabs with similar size. May be
2279 necessary if there is some reason to distinguish
2280 allocs to different slabs. Debug options disable
2281 merging on their own.
2282 For more information see Documentation/vm/slub.txt.
2284 smart2= [HW]
2285 Format: <io1>[,<io2>[,...,<io8>]]
2287 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2288 attempt to substitute SMP alternatives once at boot.
2290 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2291 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2292 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2293 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2294 smsc-ircc2.ircc_irq= [HW] IRQ line
2295 smsc-ircc2.ircc_dma= [HW] DMA channel
2296 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2297 0: Toshiba Satellite 1800 (GP data pin select)
2298 1: Fast pin select (default)
2299 2: ATC IRMode
2301 snd-ad1816a= [HW,ALSA]
2303 snd-ad1848= [HW,ALSA]
2305 snd-ali5451= [HW,ALSA]
2307 snd-als100= [HW,ALSA]
2309 snd-als4000= [HW,ALSA]
2311 snd-azt2320= [HW,ALSA]
2313 snd-cmi8330= [HW,ALSA]
2315 snd-cmipci= [HW,ALSA]
2317 snd-cs4231= [HW,ALSA]
2319 snd-cs4232= [HW,ALSA]
2321 snd-cs4236= [HW,ALSA]
2323 snd-cs4281= [HW,ALSA]
2325 snd-cs46xx= [HW,ALSA]
2327 snd-dt019x= [HW,ALSA]
2329 snd-dummy= [HW,ALSA]
2331 snd-emu10k1= [HW,ALSA]
2333 snd-ens1370= [HW,ALSA]
2335 snd-ens1371= [HW,ALSA]
2337 snd-es968= [HW,ALSA]
2339 snd-es1688= [HW,ALSA]
2341 snd-es18xx= [HW,ALSA]
2343 snd-es1938= [HW,ALSA]
2345 snd-es1968= [HW,ALSA]
2347 snd-fm801= [HW,ALSA]
2349 snd-gusclassic= [HW,ALSA]
2351 snd-gusextreme= [HW,ALSA]
2353 snd-gusmax= [HW,ALSA]
2355 snd-hdsp= [HW,ALSA]
2357 snd-ice1712= [HW,ALSA]
2359 snd-intel8x0= [HW,ALSA]
2361 snd-interwave= [HW,ALSA]
2363 snd-interwave-stb=
2364 [HW,ALSA]
2366 snd-korg1212= [HW,ALSA]
2368 snd-maestro3= [HW,ALSA]
2370 snd-mpu401= [HW,ALSA]
2372 snd-mtpav= [HW,ALSA]
2374 snd-nm256= [HW,ALSA]
2376 snd-opl3sa2= [HW,ALSA]
2378 snd-opti92x-ad1848=
2379 [HW,ALSA]
2381 snd-opti92x-cs4231=
2382 [HW,ALSA]
2384 snd-opti93x= [HW,ALSA]
2386 snd-pmac= [HW,ALSA]
2388 snd-rme32= [HW,ALSA]
2390 snd-rme96= [HW,ALSA]
2392 snd-rme9652= [HW,ALSA]
2394 snd-sb8= [HW,ALSA]
2396 snd-sb16= [HW,ALSA]
2398 snd-sbawe= [HW,ALSA]
2400 snd-serial= [HW,ALSA]
2402 snd-sgalaxy= [HW,ALSA]
2404 snd-sonicvibes= [HW,ALSA]
2406 snd-sun-amd7930=
2407 [HW,ALSA]
2409 snd-sun-cs4231= [HW,ALSA]
2411 snd-trident= [HW,ALSA]
2413 snd-usb-audio= [HW,ALSA,USB]
2415 snd-via82xx= [HW,ALSA]
2417 snd-virmidi= [HW,ALSA]
2419 snd-wavefront= [HW,ALSA]
2421 snd-ymfpci= [HW,ALSA]
2423 softlockup_panic=
2424 [KNL] Should the soft-lockup detector generate panics.
2426 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2427 See Documentation/sonypi.txt
2429 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2430 See Documentation/serial/specialix.txt.
2432 spia_io_base= [HW,MTD]
2433 spia_fio_base=
2434 spia_pedr=
2435 spia_peddr=
2437 sscape= [HW,OSS]
2438 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2440 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2441 See Documentation/scsi/st.txt.
2443 stacktrace [FTRACE]
2444 Enabled the stack tracer on boot up.
2446 sti= [PARISC,HW]
2447 Format: <num>
2448 Set the STI (builtin display/keyboard on the HP-PARISC
2449 machines) console (graphic card) which should be used
2450 as the initial boot-console.
2451 See also comment in drivers/video/console/sticore.c.
2453 sti_font= [HW]
2454 See comment in drivers/video/console/sticore.c.
2456 stifb= [HW]
2457 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2459 sunrpc.min_resvport=
2460 sunrpc.max_resvport=
2461 [NFS,SUNRPC]
2462 SunRPC servers often require that client requests
2463 originate from a privileged port (i.e. a port in the
2464 range 0 < portnr < 1024).
2465 An administrator who wishes to reserve some of these
2466 ports for other uses may adjust the range that the
2467 kernel's sunrpc client considers to be privileged
2468 using these two parameters to set the minimum and
2469 maximum port values.
2471 sunrpc.pool_mode=
2472 [NFS]
2473 Control how the NFS server code allocates CPUs to
2474 service thread pools. Depending on how many NICs
2475 you have and where their interrupts are bound, this
2476 option will affect which CPUs will do NFS serving.
2477 Note: this parameter cannot be changed while the
2478 NFS server is running.
2480 auto the server chooses an appropriate mode
2481 automatically using heuristics
2482 global a single global pool contains all CPUs
2483 percpu one pool for each CPU
2484 pernode one pool for each NUMA node (equivalent
2485 to global on non-NUMA machines)
2487 sunrpc.tcp_slot_table_entries=
2488 sunrpc.udp_slot_table_entries=
2489 [NFS,SUNRPC]
2490 Sets the upper limit on the number of simultaneous
2491 RPC calls that can be sent from the client to a
2492 server. Increasing these values may allow you to
2493 improve throughput, but will also increase the
2494 amount of memory reserved for use by the client.
2496 swiotlb= [IA-64] Number of I/O TLB slabs
2498 switches= [HW,M68k]
2500 sym53c416= [HW,SCSI]
2501 See header of drivers/scsi/sym53c416.c.
2503 sysrq_always_enabled
2504 [KNL]
2505 Ignore sysrq setting - this boot parameter will
2506 neutralize any effect of /proc/sys/kernel/sysrq.
2507 Useful for debugging.
2509 t128= [HW,SCSI]
2510 See header of drivers/scsi/t128.c.
2512 tdfx= [HW,DRM]
2514 test_suspend= [SUSPEND]
2515 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2516 standby suspend) as the system sleep state to briefly
2517 enter during system startup. The system is woken from
2518 this state using a wakeup-capable RTC alarm.
2520 thash_entries= [KNL,NET]
2521 Set number of hash buckets for TCP connection
2523 thermal.act= [HW,ACPI]
2524 -1: disable all active trip points in all thermal zones
2525 <degrees C>: override all lowest active trip points
2527 thermal.crt= [HW,ACPI]
2528 -1: disable all critical trip points in all thermal zones
2529 <degrees C>: override all critical trip points
2531 thermal.nocrt= [HW,ACPI]
2532 Set to disable actions on ACPI thermal zone
2533 critical and hot trip points.
2535 thermal.off= [HW,ACPI]
2536 1: disable ACPI thermal control
2538 thermal.psv= [HW,ACPI]
2539 -1: disable all passive trip points
2540 <degrees C>: override all passive trip points to this
2541 value
2543 thermal.tzp= [HW,ACPI]
2544 Specify global default ACPI thermal zone polling rate
2545 <deci-seconds>: poll all this frequency
2546 0: no polling (default)
2548 tmscsim= [HW,SCSI]
2549 See comment before function dc390_setup() in
2550 drivers/scsi/tmscsim.c.
2552 topology= [S390]
2553 Format: {off | on}
2554 Specify if the kernel should make use of the cpu
2555 topology informations if the hardware supports these.
2556 The scheduler will make use of these informations and
2557 e.g. base its process migration decisions on it.
2558 Default is off.
2560 tp720= [HW,PS2]
2562 trace_buf_size=nn[KMG]
2563 [FTRACE] will set tracing buffer size.
2565 trace_event=[event-list]
2566 [FTRACE] Set and start specified trace events in order
2567 to facilitate early boot debugging.
2568 See also Documentation/trace/events.txt
2570 trix= [HW,OSS] MediaTrix AudioTrix Pro
2571 Format:
2572 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2574 tsc= Disable clocksource-must-verify flag for TSC.
2575 Format: <string>
2576 [x86] reliable: mark tsc clocksource as reliable, this
2577 disables clocksource verification at runtime.
2578 Used to enable high-resolution timer mode on older
2579 hardware, and in virtualized environment.
2581 turbografx.map[2|3]= [HW,JOY]
2582 TurboGraFX parallel port interface
2583 Format:
2584 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2585 See also Documentation/input/joystick-parport.txt
2587 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2588 See header of drivers/scsi/u14-34f.c.
2590 uart401= [HW,OSS]
2591 Format: <io>,<irq>
2593 uart6850= [HW,OSS]
2594 Format: <io>,<irq>
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 b = BAD_SENSE (don't collect more than 18
2652 bytes of sense data);
2653 c = FIX_CAPACITY (decrease the reported
2654 device capacity by one sector);
2655 h = CAPACITY_HEURISTICS (decrease the
2656 reported device capacity by one
2657 sector if the number is odd);
2658 i = IGNORE_DEVICE (don't bind to this
2659 device);
2660 l = NOT_LOCKABLE (don't try to lock and
2661 unlock ejectable media);
2662 m = MAX_SECTORS_64 (don't transfer more
2663 than 64 sectors = 32 KB at a time);
2664 o = CAPACITY_OK (accept the capacity
2665 reported by the device);
2666 r = IGNORE_RESIDUE (the device reports
2667 bogus residue values);
2668 s = SINGLE_LUN (the device has only one
2669 Logical Unit);
2670 w = NO_WP_DETECT (don't test whether the
2671 medium is write-protected).
2672 Example: quirks=0419:aaf5:rl,0421:0433:rc
2674 userpte=
2675 [X86] Flags controlling user PTE allocations.
2677 nohigh = do not allocate PTE pages in
2678 HIGHMEM regardless of setting
2679 of CONFIG_HIGHPTE.
2681 vdso= [X86,SH]
2682 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2683 vdso=1: enable VDSO (default)
2684 vdso=0: disable VDSO mapping
2686 vdso32= [X86]
2687 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2688 vdso32=1: enable 32-bit VDSO (default)
2689 vdso32=0: disable 32-bit VDSO mapping
2691 vector= [IA-64,SMP]
2692 vector=percpu: enable percpu vector domain
2694 video= [FB] Frame buffer configuration
2695 See Documentation/fb/modedb.txt.
2697 vga= [BOOT,X86-32] Select a particular video mode
2698 See Documentation/x86/boot.txt and
2699 Documentation/svga.txt.
2700 Use vga=ask for menu.
2701 This is actually a boot loader parameter; the value is
2702 passed to the kernel using a special protocol.
2704 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2705 size of <nn>. This can be used to increase the
2706 minimum size (128MB on x86). It can also be used to
2707 decrease the size and leave more room for directly
2708 mapped kernel RAM.
2710 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2711 Format: <command>
2713 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2714 Format: <command>
2716 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2717 Format: <command>
2719 vt.default_blu= [VT]
2720 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2721 Change the default blue palette of the console.
2722 This is a 16-member array composed of values
2723 ranging from 0-255.
2725 vt.default_grn= [VT]
2726 Format: <green0>,<green1>,<green2>,...,<green15>
2727 Change the default green palette of the console.
2728 This is a 16-member array composed of values
2729 ranging from 0-255.
2731 vt.default_red= [VT]
2732 Format: <red0>,<red1>,<red2>,...,<red15>
2733 Change the default red palette of the console.
2734 This is a 16-member array composed of values
2735 ranging from 0-255.
2737 vt.default_utf8=
2738 [VT]
2739 Format=<0|1>
2740 Set system-wide default UTF-8 mode for all tty's.
2741 Default is 1, i.e. UTF-8 mode is enabled for all
2742 newly opened terminals.
2744 waveartist= [HW,OSS]
2745 Format: <io>,<irq>,<dma>,<dma2>
2747 wd33c93= [HW,SCSI]
2748 See header of drivers/scsi/wd33c93.c.
2750 wd7000= [HW,SCSI]
2751 See header of drivers/scsi/wd7000.c.
2753 wdt= [WDT] Watchdog
2754 See Documentation/watchdog/wdt.txt.
2756 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2757 default x2apic cluster mode on platforms
2758 supporting x2apic.
2760 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2761 xd_geo= See header of drivers/block/xd.c.
2763 xirc2ps_cs= [NET,PCMCIA]
2764 Format:
2765 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2767 ______________________________________________________________________
2769 TODO:
2771 Add documentation for ALSA options.
2772 Add more DRM drivers.