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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.notimeout [HW] Ignore timeout condition signalled by conroller
882 i8042.reset [HW] Reset the controller during init and cleanup
883 i8042.unlock [HW] Unlock (ignore) the keylock
885 i810= [HW,DRM]
887 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
888 indicates that the driver is running on unsupported
889 hardware.
890 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
891 does not match list of supported models.
892 i8k.power_status
893 [HW] Report power status in /proc/i8k
894 (disabled by default)
895 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
896 capability is set.
898 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
899 See Documentation/mca.txt.
901 icn= [HW,ISDN]
902 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
904 ide-core.nodma= [HW] (E)IDE subsystem
905 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
906 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
907 .cdrom .chs .ignore_cable are additional options
908 See Documentation/ide/ide.txt.
910 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
911 Claim all unknown PCI IDE storage controllers.
913 idle= [X86]
914 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
915 Poll forces a polling idle loop that can slightly
916 improve the performance of waking up a idle CPU, but
917 will use a lot of power and make the system run hot.
918 Not recommended.
919 idle=mwait: On systems which support MONITOR/MWAIT but
920 the kernel chose to not use it because it doesn't save
921 as much power as a normal idle loop, use the
922 MONITOR/MWAIT idle loop anyways. Performance should be
923 the same as idle=poll.
924 idle=halt: Halt is forced to be used for CPU idle.
925 In such case C2/C3 won't be used again.
926 idle=nomwait: Disable mwait for CPU C-states
928 ignore_loglevel [KNL]
929 Ignore loglevel setting - this will print /all/
930 kernel messages to the console. Useful for debugging.
932 ihash_entries= [KNL]
933 Set number of hash buckets for inode cache.
935 ima_audit= [IMA]
936 Format: { "0" | "1" }
937 0 -- integrity auditing messages. (Default)
938 1 -- enable informational integrity auditing messages.
940 ima_hash= [IMA]
941 Format: { "sha1" | "md5" }
942 default: "sha1"
944 ima_tcb [IMA]
945 Load a policy which meets the needs of the Trusted
946 Computing Base. This means IMA will measure all
947 programs exec'd, files mmap'd for exec, and all files
948 opened for read by uid=0.
950 in2000= [HW,SCSI]
951 See header of drivers/scsi/in2000.c.
953 init= [KNL]
954 Format: <full_path>
955 Run specified binary instead of /sbin/init as init
956 process.
958 initcall_debug [KNL] Trace initcalls as they are executed. Useful
959 for working out where the kernel is dying during
960 startup.
962 initrd= [BOOT] Specify the location of the initial ramdisk
964 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
965 Format: <irq>
967 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
968 on
969 Enable intel iommu driver.
970 off
971 Disable intel iommu driver.
972 igfx_off [Default Off]
973 By default, gfx is mapped as normal device. If a gfx
974 device has a dedicated DMAR unit, the DMAR unit is
975 bypassed by not enabling DMAR with this option. In
976 this case, gfx device will use physical address for
977 DMA.
978 forcedac [x86_64]
979 With this option iommu will not optimize to look
980 for io virtual address below 32 bit forcing dual
981 address cycle on pci bus for cards supporting greater
982 than 32 bit addressing. The default is to look
983 for translation below 32 bit and if not available
984 then look in the higher range.
985 strict [Default Off]
986 With this option on every unmap_single operation will
987 result in a hardware IOTLB flush operation as opposed
988 to batching them for performance.
990 inttest= [IA64]
992 iomem= Disable strict checking of access to MMIO memory
993 strict regions from userspace.
994 relaxed
996 iommu= [x86]
997 off
998 force
999 noforce
1000 biomerge
1001 panic
1002 nopanic
1003 merge
1004 nomerge
1005 forcesac
1006 soft
1007 pt [x86, IA64]
1009 io7= [HW] IO7 for Marvel based alpha systems
1010 See comment before marvel_specify_io7 in
1011 arch/alpha/kernel/core_marvel.c.
1013 io_delay= [X86] I/O delay method
1014 0x80
1015 Standard port 0x80 based delay
1016 0xed
1017 Alternate port 0xed based delay (needed on some systems)
1018 udelay
1019 Simple two microseconds delay
1020 none
1021 No delay
1023 ip= [IP_PNP]
1024 See Documentation/filesystems/nfsroot.txt.
1026 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1027 See comment before ip2_setup() in
1028 drivers/char/ip2/ip2base.c.
1030 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1031 See header of drivers/scsi/ips.c.
1033 irqfixup [HW]
1034 When an interrupt is not handled search all handlers
1035 for it. Intended to get systems with badly broken
1036 firmware running.
1038 irqpoll [HW]
1039 When an interrupt is not handled search all handlers
1040 for it. Also check all handlers each timer
1041 interrupt. Intended to get systems with badly broken
1042 firmware running.
1044 isapnp= [ISAPNP]
1045 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1047 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1048 Format:
1049 <cpu number>,...,<cpu number>
1050 or
1051 <cpu number>-<cpu number>
1052 (must be a positive range in ascending order)
1053 or a mixture
1054 <cpu number>,...,<cpu number>-<cpu number>
1056 This option can be used to specify one or more CPUs
1057 to isolate from the general SMP balancing and scheduling
1058 algorithms. You can move a process onto or off an
1059 "isolated" CPU via the CPU affinity syscalls or cpuset.
1060 <cpu number> begins at 0 and the maximum value is
1061 "number of CPUs in system - 1".
1063 This option is the preferred way to isolate CPUs. The
1064 alternative -- manually setting the CPU mask of all
1065 tasks in the system -- can cause problems and
1066 suboptimal load balancer performance.
1068 iucv= [HW,NET]
1070 js= [HW,JOY] Analog joystick
1071 See Documentation/input/joystick.txt.
1073 keepinitrd [HW,ARM]
1075 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1076 specifies the amount of memory usable by the kernel
1077 for non-movable allocations. The requested amount is
1078 spread evenly throughout all nodes in the system. The
1079 remaining memory in each node is used for Movable
1080 pages. In the event, a node is too small to have both
1081 kernelcore and Movable pages, kernelcore pages will
1082 take priority and other nodes will have a larger number
1083 of kernelcore pages. The Movable zone is used for the
1084 allocation of pages that may be reclaimed or moved
1085 by the page migration subsystem. This means that
1086 HugeTLB pages may not be allocated from this zone.
1087 Note that allocations like PTEs-from-HighMem still
1088 use the HighMem zone if it exists, and the Normal
1089 zone if it does not.
1091 kgdboc= [HW] kgdb over consoles.
1092 Requires a tty driver that supports console polling.
1093 (only serial supported for now)
1094 Format: <serial_device>[,baud]
1096 kmac= [MIPS] korina ethernet MAC address.
1097 Configure the RouterBoard 532 series on-chip
1098 Ethernet adapter MAC address.
1100 kmemleak= [KNL] Boot-time kmemleak enable/disable
1101 Valid arguments: on, off
1102 Default: on
1104 kstack=N [X86] Print N words from the kernel stack
1105 in oops dumps.
1107 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1108 Default is 0 (don't ignore, but inject #GP)
1110 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1111 Default is 1 (enabled)
1113 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1114 Default is 0 (off)
1116 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1117 for all guests.
1118 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1120 kvm-intel.bypass_guest_pf=
1121 [KVM,Intel] Disables bypassing of guest page faults
1122 on Intel chips. Default is 1 (enabled)
1124 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1125 (virtualized MMU) support on capable Intel chips.
1126 Default is 1 (enabled)
1128 kvm-intel.emulate_invalid_guest_state=
1129 [KVM,Intel] Enable emulation of invalid guest states
1130 Default is 0 (disabled)
1132 kvm-intel.flexpriority=
1133 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1134 Default is 1 (enabled)
1136 kvm-intel.unrestricted_guest=
1137 [KVM,Intel] Disable unrestricted guest feature
1138 (virtualized real and unpaged mode) on capable
1139 Intel chips. Default is 1 (enabled)
1141 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1142 feature (tagged TLBs) on capable Intel chips.
1143 Default is 1 (enabled)
1145 l2cr= [PPC]
1147 l3cr= [PPC]
1149 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1150 disabled it.
1152 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1153 in C2 power state.
1155 libata.dma= [LIBATA] DMA control
1156 libata.dma=0 Disable all PATA and SATA DMA
1157 libata.dma=1 PATA and SATA Disk DMA only
1158 libata.dma=2 ATAPI (CDROM) DMA only
1159 libata.dma=4 Compact Flash DMA only
1160 Combinations also work, so libata.dma=3 enables DMA
1161 for disks and CDROMs, but not CFs.
1163 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1164 libata.ignore_hpa=0 keep BIOS limits (default)
1165 libata.ignore_hpa=1 ignore limits, using full disk
1167 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1168 when set.
1169 Format: <int>
1171 libata.force= [LIBATA] Force configurations. The format is comma
1172 separated list of "[ID:]VAL" where ID is
1173 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1174 matching port, link or device. Basically, it matches
1175 the ATA ID string printed on console by libata. If
1176 the whole ID part is omitted, the last PORT and DEVICE
1177 values are used. If ID hasn't been specified yet, the
1178 configuration applies to all ports, links and devices.
1180 If only DEVICE is omitted, the parameter applies to
1181 the port and all links and devices behind it. DEVICE
1182 number of 0 either selects the first device or the
1183 first fan-out link behind PMP device. It does not
1184 select the host link. DEVICE number of 15 selects the
1185 host link and device attached to it.
1187 The VAL specifies the configuration to force. As long
1188 as there's no ambiguity shortcut notation is allowed.
1189 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1190 The following configurations can be forced.
1192 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1193 Any ID with matching PORT is used.
1195 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1197 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1198 udma[/][16,25,33,44,66,100,133] notation is also
1199 allowed.
1201 * [no]ncq: Turn on or off NCQ.
1203 * nohrst, nosrst, norst: suppress hard, soft
1204 and both resets.
1206 If there are multiple matching configurations changing
1207 the same attribute, the last one is used.
1209 lmb=debug [KNL] Enable lmb debug messages.
1211 load_ramdisk= [RAM] List of ramdisks to load from floppy
1212 See Documentation/blockdev/ramdisk.txt.
1214 lockd.nlm_grace_period=P [NFS] Assign grace period.
1215 Format: <integer>
1217 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1218 Format: <integer>
1220 lockd.nlm_timeout=T [NFS] Assign timeout value.
1221 Format: <integer>
1223 lockd.nlm_udpport=M [NFS] Assign UDP port.
1224 Format: <integer>
1226 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1227 Format: <irq>
1229 loglevel= All Kernel Messages with a loglevel smaller than the
1230 console loglevel will be printed to the console. It can
1231 also be changed with klogd or other programs. The
1232 loglevels are defined as follows:
1234 0 (KERN_EMERG) system is unusable
1235 1 (KERN_ALERT) action must be taken immediately
1236 2 (KERN_CRIT) critical conditions
1237 3 (KERN_ERR) error conditions
1238 4 (KERN_WARNING) warning conditions
1239 5 (KERN_NOTICE) normal but significant condition
1240 6 (KERN_INFO) informational
1241 7 (KERN_DEBUG) debug-level messages
1243 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1244 Format: { n | nk | nM }
1245 n must be a power of two. The default size
1246 is set in the kernel config file.
1248 logo.nologo [FB] Disables display of the built-in Linux logo.
1249 This may be used to provide more screen space for
1250 kernel log messages and is useful when debugging
1251 kernel boot problems.
1253 lp=0 [LP] Specify parallel ports to use, e.g,
1254 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1255 lp=reset first parallel port). 'lp=0' disables the
1256 lp=auto printer driver. 'lp=reset' (which can be
1257 specified in addition to the ports) causes
1258 attached printers to be reset. Using
1259 lp=port1,port2,... specifies the parallel ports
1260 to associate lp devices with, starting with
1261 lp0. A port specification may be 'none' to skip
1262 that lp device, or a parport name such as
1263 'parport0'. Specifying 'lp=auto' instead of a
1264 port specification list means that device IDs
1265 from each port should be examined, to see if
1266 an IEEE 1284-compliant printer is attached; if
1267 so, the driver will manage that printer.
1268 See also header of drivers/char/lp.c.
1270 lpj=n [KNL]
1271 Sets loops_per_jiffy to given constant, thus avoiding
1272 time-consuming boot-time autodetection (up to 250 ms per
1273 CPU). 0 enables autodetection (default). To determine
1274 the correct value for your kernel, boot with normal
1275 autodetection and see what value is printed. Note that
1276 on SMP systems the preset will be applied to all CPUs,
1277 which is likely to cause problems if your CPUs need
1278 significantly divergent settings. An incorrect value
1279 will cause delays in the kernel to be wrong, leading to
1280 unpredictable I/O errors and other breakage. Although
1281 unlikely, in the extreme case this might damage your
1282 hardware.
1284 ltpc= [NET]
1285 Format: <io>,<irq>,<dma>
1287 mac5380= [HW,SCSI] Format:
1288 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1290 machvec= [IA64] Force the use of a particular machine-vector
1291 (machvec) in a generic kernel.
1292 Example: machvec=hpzx1_swiotlb
1294 machtype= [Loongson] Share the same kernel image file between different
1295 yeeloong laptop.
1296 Example: machtype=lemote-yeeloong-2f-7inch
1298 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1299 than or equal to this physical address is ignored.
1301 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1302 should make use of. maxcpus=n : n >= 0 limits the
1303 kernel to using 'n' processors. n=0 is a special case,
1304 it is equivalent to "nosmp", which also disables
1305 the IO APIC.
1307 max_loop= [LOOP] Maximum number of loopback devices that can
1308 be mounted
1309 Format: <1-256>
1311 max_luns= [SCSI] Maximum number of LUNs to probe.
1312 Should be between 1 and 2^32-1.
1314 max_report_luns=
1315 [SCSI] Maximum number of LUNs received.
1316 Should be between 1 and 16384.
1318 mcatest= [IA-64]
1320 mce [X86-32] Machine Check Exception
1322 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1324 md= [HW] RAID subsystems devices and level
1325 See Documentation/md.txt.
1327 mdacon= [MDA]
1328 Format: <first>,<last>
1329 Specifies range of consoles to be captured by the MDA.
1331 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1332 Amount of memory to be used when the kernel is not able
1333 to see the whole system memory or for test.
1334 [X86-32] Use together with memmap= to avoid physical
1335 address space collisions. Without memmap= PCI devices
1336 could be placed at addresses belonging to unused RAM.
1338 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1339 memory.
1341 memchunk=nn[KMG]
1342 [KNL,SH] Allow user to override the default size for
1343 per-device physically contiguous DMA buffers.
1345 memmap=exactmap [KNL,X86] Enable setting of an exact
1346 E820 memory map, as specified by the user.
1347 Such memmap=exactmap lines can be constructed based on
1348 BIOS output or other requirements. See the memmap=nn@ss
1349 option description.
1351 memmap=nn[KMG]@ss[KMG]
1352 [KNL] Force usage of a specific region of memory
1353 Region of memory to be used, from ss to ss+nn.
1355 memmap=nn[KMG]#ss[KMG]
1356 [KNL,ACPI] Mark specific memory as ACPI data.
1357 Region of memory to be used, from ss to ss+nn.
1359 memmap=nn[KMG]$ss[KMG]
1360 [KNL,ACPI] Mark specific memory as reserved.
1361 Region of memory to be used, from ss to ss+nn.
1362 Example: Exclude memory from 0x18690000-0x1869ffff
1363 memmap=64K$0x18690000
1364 or
1365 memmap=0x10000$0x18690000
1367 memory_corruption_check=0/1 [X86]
1368 Some BIOSes seem to corrupt the first 64k of
1369 memory when doing things like suspend/resume.
1370 Setting this option will scan the memory
1371 looking for corruption. Enabling this will
1372 both detect corruption and prevent the kernel
1373 from using the memory being corrupted.
1374 However, its intended as a diagnostic tool; if
1375 repeatable BIOS-originated corruption always
1376 affects the same memory, you can use memmap=
1377 to prevent the kernel from using that memory.
1379 memory_corruption_check_size=size [X86]
1380 By default it checks for corruption in the low
1381 64k, making this memory unavailable for normal
1382 use. Use this parameter to scan for
1383 corruption in more or less memory.
1385 memory_corruption_check_period=seconds [X86]
1386 By default it checks for corruption every 60
1387 seconds. Use this parameter to check at some
1388 other rate. 0 disables periodic checking.
1390 memtest= [KNL,X86] Enable memtest
1391 Format: <integer>
1392 default : 0 <disable>
1393 Specifies the number of memtest passes to be
1394 performed. Each pass selects another test
1395 pattern from a given set of patterns. Memtest
1396 fills the memory with this pattern, validates
1397 memory contents and reserves bad memory
1398 regions that are detected.
1400 meye.*= [HW] Set MotionEye Camera parameters
1401 See Documentation/video4linux/meye.txt.
1403 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1404 Multi-Function General Purpose Timers on AMD Geode
1405 platforms.
1407 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1408 the BIOS has incorrectly applied a workaround. TinyBIOS
1409 version 0.98 is known to be affected, 0.99 fixes the
1410 problem by letting the user disable the workaround.
1412 mga= [HW,DRM]
1414 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1415 physical address is ignored.
1417 mini2440= [ARM,HW,KNL]
1418 Format:[0..2][b][c][t]
1419 Default: "0tb"
1420 MINI2440 configuration specification:
1421 0 - The attached screen is the 3.5" TFT
1422 1 - The attached screen is the 7" TFT
1423 2 - The VGA Shield is attached (1024x768)
1424 Leaving out the screen size parameter will not load
1425 the TFT driver, and the framebuffer will be left
1426 unconfigured.
1427 b - Enable backlight. The TFT backlight pin will be
1428 linked to the kernel VESA blanking code and a GPIO
1429 LED. This parameter is not necessary when using the
1430 VGA shield.
1431 c - Enable the s3c camera interface.
1432 t - Reserved for enabling touchscreen support. The
1433 touchscreen support is not enabled in the mainstream
1434 kernel as of 2.6.30, a preliminary port can be found
1435 in the "bleeding edge" mini2440 support kernel at
1436 http://repo.or.cz/w/linux-2.6/mini2440.git
1438 mminit_loglevel=
1439 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1440 parameter allows control of the logging verbosity for
1441 the additional memory initialisation checks. A value
1442 of 0 disables mminit logging and a level of 4 will
1443 log everything. Information is printed at KERN_DEBUG
1444 so loglevel=8 may also need to be specified.
1446 mousedev.tap_time=
1447 [MOUSE] Maximum time between finger touching and
1448 leaving touchpad surface for touch to be considered
1449 a tap and be reported as a left button click (for
1450 touchpads working in absolute mode only).
1451 Format: <msecs>
1452 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1453 reporting absolute coordinates, such as tablets
1454 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1455 reporting absolute coordinates, such as tablets
1457 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1458 is similar to kernelcore except it specifies the
1459 amount of memory used for migratable allocations.
1460 If both kernelcore and movablecore is specified,
1461 then kernelcore will be at *least* the specified
1462 value but may be more. If movablecore on its own
1463 is specified, the administrator must be careful
1464 that the amount of memory usable for all allocations
1465 is not too small.
1467 mpu401= [HW,OSS]
1468 Format: <io>,<irq>
1470 MTD_Partition= [MTD]
1471 Format: <name>,<region-number>,<size>,<offset>
1473 MTD_Region= [MTD] Format:
1474 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1476 mtdparts= [MTD]
1477 See drivers/mtd/cmdlinepart.c.
1479 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1481 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1483 boundary - index of last SLC block on Flex-OneNAND.
1484 The remaining blocks are configured as MLC blocks.
1485 lock - Configure if Flex-OneNAND boundary should be locked.
1486 Once locked, the boundary cannot be changed.
1487 1 indicates lock status, 0 indicates unlock status.
1489 mtdset= [ARM]
1490 ARM/S3C2412 JIVE boot control
1492 See arch/arm/mach-s3c2412/mach-jive.c
1494 mtouchusb.raw_coordinates=
1495 [HW] Make the MicroTouch USB driver use raw coordinates
1496 ('y', default) or cooked coordinates ('n')
1498 mtrr_chunk_size=nn[KMG] [X86]
1499 used for mtrr cleanup. It is largest continuous chunk
1500 that could hold holes aka. UC entries.
1502 mtrr_gran_size=nn[KMG] [X86]
1503 Used for mtrr cleanup. It is granularity of mtrr block.
1504 Default is 1.
1505 Large value could prevent small alignment from
1506 using up MTRRs.
1508 mtrr_spare_reg_nr=n [X86]
1509 Format: <integer>
1510 Range: 0,7 : spare reg number
1511 Default : 1
1512 Used for mtrr cleanup. It is spare mtrr entries number.
1513 Set to 2 or more if your graphical card needs more.
1515 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1517 NCR_D700= [HW,SCSI]
1518 See header of drivers/scsi/NCR_D700.c.
1520 ncr5380= [HW,SCSI]
1522 ncr53c400= [HW,SCSI]
1524 ncr53c400a= [HW,SCSI]
1526 ncr53c406a= [HW,SCSI]
1528 ncr53c8xx= [HW,SCSI]
1530 netdev= [NET] Network devices parameters
1531 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1532 Note that mem_start is often overloaded to mean
1533 something different and driver-specific.
1534 This usage is only documented in each driver source
1535 file if at all.
1537 nf_conntrack.acct=
1538 [NETFILTER] Enable connection tracking flow accounting
1539 0 to disable accounting
1540 1 to enable accounting
1541 Default value depends on CONFIG_NF_CT_ACCT that is
1542 going to be removed in 2.6.29.
1544 nfsaddrs= [NFS]
1545 See Documentation/filesystems/nfsroot.txt.
1547 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1548 See Documentation/filesystems/nfsroot.txt.
1550 nfs.callback_tcpport=
1551 [NFS] set the TCP port on which the NFSv4 callback
1552 channel should listen.
1554 nfs.cache_getent=
1555 [NFS] sets the pathname to the program which is used
1556 to update the NFS client cache entries.
1558 nfs.cache_getent_timeout=
1559 [NFS] sets the timeout after which an attempt to
1560 update a cache entry is deemed to have failed.
1562 nfs.idmap_cache_timeout=
1563 [NFS] set the maximum lifetime for idmapper cache
1564 entries.
1566 nfs.enable_ino64=
1567 [NFS] enable 64-bit inode numbers.
1568 If zero, the NFS client will fake up a 32-bit inode
1569 number for the readdir() and stat() syscalls instead
1570 of returning the full 64-bit number.
1571 The default is to return 64-bit inode numbers.
1573 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1574 when a NMI is triggered.
1575 Format: [state][,regs][,debounce][,die]
1577 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1578 Format: [panic,][num]
1579 Valid num: 0,1,2
1580 0 - turn nmi_watchdog off
1581 1 - use the IO-APIC timer for the NMI watchdog
1582 2 - use the local APIC for the NMI watchdog using
1583 a performance counter. Note: This will use one
1584 performance counter and the local APIC's performance
1585 vector.
1586 When panic is specified, panic when an NMI watchdog
1587 timeout occurs.
1588 This is useful when you use a panic=... timeout and
1589 need the box quickly up again.
1590 Instead of 1 and 2 it is possible to use the following
1591 symbolic names: lapic and ioapic
1592 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1594 netpoll.carrier_timeout=
1595 [NET] Specifies amount of time (in seconds) that
1596 netpoll should wait for a carrier. By default netpoll
1597 waits 4 seconds.
1599 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1600 emulation library even if a 387 maths coprocessor
1601 is present.
1603 no_console_suspend
1604 [HW] Never suspend the console
1605 Disable suspending of consoles during suspend and
1606 hibernate operations. Once disabled, debugging
1607 messages can reach various consoles while the rest
1608 of the system is being put to sleep (ie, while
1609 debugging driver suspend/resume hooks). This may
1610 not work reliably with all consoles, but is known
1611 to work with serial and VGA consoles.
1613 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1614 caches in the slab allocator. Saves per-node memory,
1615 but will impact performance.
1617 noalign [KNL,ARM]
1619 noapic [SMP,APIC] Tells the kernel to not make use of any
1620 IOAPICs that may be present in the system.
1622 nobats [PPC] Do not use BATs for mapping kernel lowmem
1623 on "Classic" PPC cores.
1625 nocache [ARM]
1627 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1629 nodelayacct [KNL] Disable per-task delay accounting
1631 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1633 nodsp [SH] Disable hardware DSP at boot time.
1635 noefi [X86] Disable EFI runtime services support.
1637 noexec [IA-64]
1639 noexec [X86]
1640 On X86-32 available only on PAE configured kernels.
1641 noexec=on: enable non-executable mappings (default)
1642 noexec=off: disable non-executable mappings
1644 noexec32 [X86-64]
1645 This affects only 32-bit executables.
1646 noexec32=on: enable non-executable mappings (default)
1647 read doesn't imply executable mappings
1648 noexec32=off: disable non-executable mappings
1649 read implies executable mappings
1651 nofpu [SH] Disable hardware FPU at boot time.
1653 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1654 register save and restore. The kernel will only save
1655 legacy floating-point registers on task switch.
1657 noxsave [BUGS=X86] Disables x86 extended register state save
1658 and restore using xsave. The kernel will fallback to
1659 enabling legacy floating-point and sse state.
1661 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1662 wfi(ARM) instruction doesn't work correctly and not to
1663 use it. This is also useful when using JTAG debugger.
1665 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1666 instruction doesn't work correctly and not to
1667 use it.
1669 no_file_caps Tells the kernel not to honor file capabilities. The
1670 only way then for a file to be executed with privilege
1671 is to be setuid root or executed by root.
1673 nohalt [IA-64] Tells the kernel not to use the power saving
1674 function PAL_HALT_LIGHT when idle. This increases
1675 power-consumption. On the positive side, it reduces
1676 interrupt wake-up latency, which may improve performance
1677 in certain environments such as networked servers or
1678 real-time systems.
1680 nohz= [KNL] Boottime enable/disable dynamic ticks
1681 Valid arguments: on, off
1682 Default: on
1684 noiotrap [SH] Disables trapped I/O port accesses.
1686 noirqdebug [X86-32] Disables the code which attempts to detect and
1687 disable unhandled interrupt sources.
1689 no_timer_check [X86,APIC] Disables the code which tests for
1690 broken timer IRQ sources.
1692 noisapnp [ISAPNP] Disables ISA PnP code.
1694 noinitrd [RAM] Tells the kernel not to load any configured
1695 initial RAM disk.
1697 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1698 remapping.
1700 nointroute [IA-64]
1702 nojitter [IA64] Disables jitter checking for ITC timers.
1704 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1706 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1708 noltlbs [PPC] Do not use large page/tlb entries for kernel
1709 lowmem mapping on PPC40x.
1711 nomca [IA-64] Disable machine check abort handling
1713 nomce [X86-32] Machine Check Exception
1715 nomfgpt [X86-32] Disable Multi-Function General Purpose
1716 Timer usage (for AMD Geode machines).
1718 norandmaps Don't use address space randomization. Equivalent to
1719 echo 0 > /proc/sys/kernel/randomize_va_space
1721 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1723 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1724 with UP alternatives
1726 noresidual [PPC] Don't use residual data on PReP machines.
1728 nordrand [X86] Disable the direct use of the RDRAND
1729 instruction even if it is supported by the
1730 processor. RDRAND is still available to user
1731 space applications.
1733 noresume [SWSUSP] Disables resume and restores original swap
1734 space.
1736 no-scroll [VGA] Disables scrollback.
1737 This is required for the Braillex ib80-piezo Braille
1738 reader made by F.H. Papenmeier (Germany).
1740 nosbagart [IA-64]
1742 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1744 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1745 and disable the IO APIC. legacy for "maxcpus=0".
1747 nosoftlockup [KNL] Disable the soft-lockup detector.
1749 noswapaccount [KNL] Disable accounting of swap in memory resource
1750 controller. (See Documentation/cgroups/memory.txt)
1752 nosync [HW,M68K] Disables sync negotiation for all devices.
1754 notsc [BUGS=X86-32] Disable Time Stamp Counter
1756 nousb [USB] Disable the USB subsystem
1758 nowb [ARM]
1760 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1762 nptcg= [IA64] Override max number of concurrent global TLB
1763 purges which is reported from either PAL_VM_SUMMARY or
1764 SAL PALO.
1766 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1768 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1769 one of ['zone', 'node', 'default'] can be specified
1770 This can be set from sysctl after boot.
1771 See Documentation/sysctl/vm.txt for details.
1773 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1774 See Documentation/debugging-via-ohci1394.txt for more
1775 info.
1777 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1778 Rather than timing out after 20 ms if an EC
1779 command is not properly ACKed, override the length
1780 of the timeout. We have interrupts disabled while
1781 waiting for the ACK, so if this is set too high
1782 interrupts *may* be lost!
1784 opl3= [HW,OSS]
1785 Format: <io>
1787 oprofile.timer= [HW]
1788 Use timer interrupt instead of performance counters
1790 oprofile.cpu_type= Force an oprofile cpu type
1791 This might be useful if you have an older oprofile
1792 userland or if you want common events.
1793 Format: { arch_perfmon }
1794 arch_perfmon: [X86] Force use of architectural
1795 perfmon on Intel CPUs instead of the
1796 CPU specific event set.
1798 osst= [HW,SCSI] SCSI Tape Driver
1799 Format: <buffer_size>,<write_threshold>
1800 See also Documentation/scsi/st.txt.
1802 panic= [KNL] Kernel behaviour on panic
1803 Format: <timeout>
1805 parkbd.port= [HW] Parallel port number the keyboard adapter is
1806 connected to, default is 0.
1807 Format: <parport#>
1808 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1809 0 for XT, 1 for AT (default is AT).
1810 Format: <mode>
1812 parport= [HW,PPT] Specify parallel ports. 0 disables.
1813 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1814 Use 'auto' to force the driver to use any
1815 IRQ/DMA settings detected (the default is to
1816 ignore detected IRQ/DMA settings because of
1817 possible conflicts). You can specify the base
1818 address, IRQ, and DMA settings; IRQ and DMA
1819 should be numbers, or 'auto' (for using detected
1820 settings on that particular port), or 'nofifo'
1821 (to avoid using a FIFO even if it is detected).
1822 Parallel ports are assigned in the order they
1823 are specified on the command line, starting
1824 with parport0.
1826 parport_init_mode= [HW,PPT]
1827 Configure VIA parallel port to operate in
1828 a specific mode. This is necessary on Pegasos
1829 computer where firmware has no options for setting
1830 up parallel port mode and sets it to spp.
1831 Currently this function knows 686a and 8231 chips.
1832 Format: [spp|ps2|epp|ecp|ecpepp]
1834 pas2= [HW,OSS] Format:
1835 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1837 pas16= [HW,SCSI]
1838 See header of drivers/scsi/pas16.c.
1840 pause_on_oops=
1841 Halt all CPUs after the first oops has been printed for
1842 the specified number of seconds. This is to be used if
1843 your oopses keep scrolling off the screen.
1845 pcbit= [HW,ISDN]
1847 pcd. [PARIDE]
1848 See header of drivers/block/paride/pcd.c.
1849 See also Documentation/blockdev/paride.txt.
1851 pci=option[,option...] [PCI] various PCI subsystem options:
1852 earlydump [X86] dump PCI config space before the kernel
1853 changes anything
1854 off [X86] don't probe for the PCI bus
1855 bios [X86-32] force use of PCI BIOS, don't access
1856 the hardware directly. Use this if your machine
1857 has a non-standard PCI host bridge.
1858 nobios [X86-32] disallow use of PCI BIOS, only direct
1859 hardware access methods are allowed. Use this
1860 if you experience crashes upon bootup and you
1861 suspect they are caused by the BIOS.
1862 conf1 [X86] Force use of PCI Configuration
1863 Mechanism 1.
1864 conf2 [X86] Force use of PCI Configuration
1865 Mechanism 2.
1866 noaer [PCIE] If the PCIEAER kernel config parameter is
1867 enabled, this kernel boot option can be used to
1868 disable the use of PCIE advanced error reporting.
1869 nodomains [PCI] Disable support for multiple PCI
1870 root domains (aka PCI segments, in ACPI-speak).
1871 nommconf [X86] Disable use of MMCONFIG for PCI
1872 Configuration
1873 check_enable_amd_mmconf [X86] check for and enable
1874 properly configured MMIO access to PCI
1875 config space on AMD family 10h CPU
1876 nomsi [MSI] If the PCI_MSI kernel config parameter is
1877 enabled, this kernel boot option can be used to
1878 disable the use of MSI interrupts system-wide.
1879 noioapicquirk [APIC] Disable all boot interrupt quirks.
1880 Safety option to keep boot IRQs enabled. This
1881 should never be necessary.
1882 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1883 primary IO-APIC for bridges that cannot disable
1884 boot IRQs. This fixes a source of spurious IRQs
1885 when the system masks IRQs.
1886 noioapicreroute [APIC] Disable workaround that uses the
1887 boot IRQ equivalent of an IRQ that connects to
1888 a chipset where boot IRQs cannot be disabled.
1889 The opposite of ioapicreroute.
1890 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1891 routing table. These calls are known to be buggy
1892 on several machines and they hang the machine
1893 when used, but on other computers it's the only
1894 way to get the interrupt routing table. Try
1895 this option if the kernel is unable to allocate
1896 IRQs or discover secondary PCI buses on your
1897 motherboard.
1898 rom [X86] Assign address space to expansion ROMs.
1899 Use with caution as certain devices share
1900 address decoders between ROMs and other
1901 resources.
1902 norom [X86] Do not assign address space to
1903 expansion ROMs that do not already have
1904 BIOS assigned address ranges.
1905 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1906 assigned automatically to PCI devices. You can
1907 make the kernel exclude IRQs of your ISA cards
1908 this way.
1909 pirqaddr=0xAAAAA [X86] Specify the physical address
1910 of the PIRQ table (normally generated
1911 by the BIOS) if it is outside the
1912 F0000h-100000h range.
1913 lastbus=N [X86] Scan all buses thru bus #N. Can be
1914 useful if the kernel is unable to find your
1915 secondary buses and you want to tell it
1916 explicitly which ones they are.
1917 assign-busses [X86] Always assign all PCI bus
1918 numbers ourselves, overriding
1919 whatever the firmware may have done.
1920 usepirqmask [X86] Honor the possible IRQ mask stored
1921 in the BIOS $PIR table. This is needed on
1922 some systems with broken BIOSes, notably
1923 some HP Pavilion N5400 and Omnibook XE3
1924 notebooks. This will have no effect if ACPI
1925 IRQ routing is enabled.
1926 noacpi [X86] Do not use ACPI for IRQ routing
1927 or for PCI scanning.
1928 use_crs [X86] Use _CRS for PCI resource
1929 allocation.
1930 routeirq Do IRQ routing for all PCI devices.
1931 This is normally done in pci_enable_device(),
1932 so this option is a temporary workaround
1933 for broken drivers that don't call it.
1934 skip_isa_align [X86] do not align io start addr, so can
1935 handle more pci cards
1936 firmware [ARM] Do not re-enumerate the bus but instead
1937 just use the configuration from the
1938 bootloader. This is currently used on
1939 IXP2000 systems where the bus has to be
1940 configured a certain way for adjunct CPUs.
1941 noearly [X86] Don't do any early type 1 scanning.
1942 This might help on some broken boards which
1943 machine check when some devices' config space
1944 is read. But various workarounds are disabled
1945 and some IOMMU drivers will not work.
1946 bfsort Sort PCI devices into breadth-first order.
1947 This sorting is done to get a device
1948 order compatible with older (<= 2.4) kernels.
1949 nobfsort Don't sort PCI devices into breadth-first order.
1950 cbiosize=nn[KMG] The fixed amount of bus space which is
1951 reserved for the CardBus bridge's IO window.
1952 The default value is 256 bytes.
1953 cbmemsize=nn[KMG] The fixed amount of bus space which is
1954 reserved for the CardBus bridge's memory
1955 window. The default value is 64 megabytes.
1956 resource_alignment=
1957 Format:
1958 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1959 Specifies alignment and device to reassign
1960 aligned memory resources.
1961 If <order of align> is not specified,
1962 PAGE_SIZE is used as alignment.
1963 PCI-PCI bridge can be specified, if resource
1964 windows need to be expanded.
1965 ecrc= Enable/disable PCIe ECRC (transaction layer
1966 end-to-end CRC checking).
1967 bios: Use BIOS/firmware settings. This is the
1968 the default.
1969 off: Turn ECRC off
1970 on: Turn ECRC on.
1972 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1973 Management.
1974 off Disable ASPM.
1975 force Enable ASPM even on devices that claim not to support it.
1976 WARNING: Forcing ASPM on may cause system lockups.
1978 pcmv= [HW,PCMCIA] BadgePAD 4
1980 pd. [PARIDE]
1981 See Documentation/blockdev/paride.txt.
1983 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1984 boot time.
1985 Format: { 0 | 1 }
1986 See arch/parisc/kernel/pdc_chassis.c
1988 percpu_alloc= Select which percpu first chunk allocator to use.
1989 Currently supported values are "embed" and "page".
1990 Archs may support subset or none of the selections.
1991 See comments in mm/percpu.c for details on each
1992 allocator. This parameter is primarily for debugging
1993 and performance comparison.
1995 pf. [PARIDE]
1996 See Documentation/blockdev/paride.txt.
1998 pg. [PARIDE]
1999 See Documentation/blockdev/paride.txt.
2001 pirq= [SMP,APIC] Manual mp-table setup
2002 See Documentation/x86/i386/IO-APIC.txt.
2004 plip= [PPT,NET] Parallel port network link
2005 Format: { parport<nr> | timid | 0 }
2006 See also Documentation/parport.txt.
2008 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2009 Override pmtimer IOPort with a hex value.
2010 e.g. pmtmr=0x508
2012 pnp.debug [PNP]
2013 Enable PNP debug messages. This depends on the
2014 CONFIG_PNP_DEBUG_MESSAGES option.
2016 pnpacpi= [ACPI]
2017 { off }
2019 pnpbios= [ISAPNP]
2020 { on | off | curr | res | no-curr | no-res }
2022 pnp_reserve_irq=
2023 [ISAPNP] Exclude IRQs for the autoconfiguration
2025 pnp_reserve_dma=
2026 [ISAPNP] Exclude DMAs for the autoconfiguration
2028 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2029 Ranges are in pairs (I/O port base and size).
2031 pnp_reserve_mem=
2032 [ISAPNP] Exclude memory regions for the
2033 autoconfiguration.
2034 Ranges are in pairs (memory base and size).
2036 ports= [IP_VS_FTP] IPVS ftp helper module
2037 Default is 21.
2038 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2039 may be specified.
2040 Format: <port>,<port>....
2042 print-fatal-signals=
2043 [KNL] debug: print fatal signals
2044 print-fatal-signals=1: print segfault info to
2045 the kernel console.
2046 default: off.
2048 printk.time= Show timing data prefixed to each printk message line
2049 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2051 processor.max_cstate= [HW,ACPI]
2052 Limit processor to maximum C-state
2053 max_cstate=9 overrides any DMI blacklist limit.
2055 processor.nocst [HW,ACPI]
2056 Ignore the _CST method to determine C-states,
2057 instead using the legacy FADT method
2059 profile= [KNL] Enable kernel profiling via /proc/profile
2060 Format: [schedule,]<number>
2061 Param: "schedule" - profile schedule points.
2062 Param: <number> - step/bucket size as a power of 2 for
2063 statistical time based profiling.
2064 Param: "sleep" - profile D-state sleeping (millisecs).
2065 Requires CONFIG_SCHEDSTATS
2066 Param: "kvm" - profile VM exits.
2068 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2069 before loading.
2070 See Documentation/blockdev/ramdisk.txt.
2072 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2073 probe for; one of (bare|imps|exps|lifebook|any).
2074 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2075 per second.
2076 psmouse.resetafter= [HW,MOUSE]
2077 Try to reset the device after so many bad packets
2078 (0 = never).
2079 psmouse.resolution=
2080 [HW,MOUSE] Set desired mouse resolution, in dpi.
2081 psmouse.smartscroll=
2082 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2083 0 = disabled, 1 = enabled (default).
2085 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2086 Format:
2087 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2089 pt. [PARIDE]
2090 See Documentation/blockdev/paride.txt.
2092 pty.legacy_count=
2093 [KNL] Number of legacy pty's. Overwrites compiled-in
2094 default number.
2096 quiet [KNL] Disable most log messages
2098 r128= [HW,DRM]
2100 raid= [HW,RAID]
2101 See Documentation/md.txt.
2103 ramdisk_blocksize= [RAM]
2104 See Documentation/blockdev/ramdisk.txt.
2106 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2107 See Documentation/blockdev/ramdisk.txt.
2109 rcupdate.blimit= [KNL,BOOT]
2110 Set maximum number of finished RCU callbacks to process
2111 in one batch.
2113 rcupdate.qhimark= [KNL,BOOT]
2114 Set threshold of queued
2115 RCU callbacks over which batch limiting is disabled.
2117 rcupdate.qlowmark= [KNL,BOOT]
2118 Set threshold of queued RCU callbacks below which
2119 batch limiting is re-enabled.
2121 rdinit= [KNL]
2122 Format: <full_path>
2123 Run specified binary instead of /init from the ramdisk,
2124 used for early userspace startup. See initrd.
2126 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2127 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2128 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2130 relax_domain_level=
2131 [KNL, SMP] Set scheduler's default relax_domain_level.
2132 See Documentation/cgroups/cpusets.txt.
2134 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2136 reservetop= [X86-32]
2137 Format: nn[KMG]
2138 Reserves a hole at the top of the kernel virtual
2139 address space.
2141 reset_devices [KNL] Force drivers to reset the underlying device
2142 during initialization.
2144 resume= [SWSUSP]
2145 Specify the partition device for software suspend
2147 resume_offset= [SWSUSP]
2148 Specify the offset from the beginning of the partition
2149 given by "resume=" at which the swap header is located,
2150 in <PAGE_SIZE> units (needed only for swap files).
2151 See Documentation/power/swsusp-and-swap-files.txt
2153 retain_initrd [RAM] Keep initrd memory after extraction
2155 rhash_entries= [KNL,NET]
2156 Set number of hash buckets for route cache
2158 riscom8= [HW,SERIAL]
2159 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2161 ro [KNL] Mount root device read-only on boot
2163 root= [KNL] Root filesystem
2165 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2166 mount the root filesystem
2168 rootflags= [KNL] Set root filesystem mount option string
2170 rootfstype= [KNL] Set root filesystem type
2172 rootwait [KNL] Wait (indefinitely) for root device to show up.
2173 Useful for devices that are detected asynchronously
2174 (e.g. USB and MMC devices).
2176 root_plug.vendor_id=
2177 [ROOTPLUG] Override the default vendor ID
2179 root_plug.product_id=
2180 [ROOTPLUG] Override the default product ID
2182 root_plug.debug=
2183 [ROOTPLUG] Enable debugging output
2185 rw [KNL] Mount root device read-write on boot
2187 S [KNL] Run init in single mode
2189 sa1100ir [NET]
2190 See drivers/net/irda/sa1100_ir.c.
2192 sbni= [NET] Granch SBNI12 leased line adapter
2194 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2195 Format: <io>[,<timeout>[,<isapnp>]]
2197 scsi_debug_*= [SCSI]
2198 See drivers/scsi/scsi_debug.c.
2200 scsi_default_dev_flags=
2201 [SCSI] SCSI default device flags
2202 Format: <integer>
2204 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2205 Format: <vendor>:<model>:<flags>
2206 (flags are integer value)
2208 scsi_logging_level= [SCSI] a bit mask of logging levels
2209 See drivers/scsi/scsi_logging.h for bits. Also
2210 settable via sysctl at dev.scsi.logging_level
2211 (/proc/sys/dev/scsi/logging_level).
2212 There is also a nice 'scsi_logging_level' script in the
2213 S390-tools package, available for download at
2214 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2216 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2217 discovered. async scans them in kernel threads,
2218 allowing boot to proceed. none ignores them, expecting
2219 user space to do the scan.
2221 security= [SECURITY] Choose a security module to enable at boot.
2222 If this boot parameter is not specified, only the first
2223 security module asking for security registration will be
2224 loaded. An invalid security module name will be treated
2225 as if no module has been chosen.
2227 selinux= [SELINUX] Disable or enable SELinux at boot time.
2228 Format: { "0" | "1" }
2229 See security/selinux/Kconfig help text.
2230 0 -- disable.
2231 1 -- enable.
2232 Default value is set via kernel config option.
2233 If enabled at boot time, /selinux/disable can be used
2234 later to disable prior to initial policy load.
2236 serialnumber [BUGS=X86-32]
2238 shapers= [NET]
2239 Maximal number of shapers.
2241 show_msr= [x86] show boot-time MSR settings
2242 Format: { <integer> }
2243 Show boot-time (BIOS-initialized) MSR settings.
2244 The parameter means the number of CPUs to show,
2245 for example 1 means boot CPU only.
2247 sim710= [SCSI,HW]
2248 See header of drivers/scsi/sim710.c.
2250 simeth= [IA-64]
2251 simscsi=
2253 slram= [HW,MTD]
2255 slub_debug[=options[,slabs]] [MM, SLUB]
2256 Enabling slub_debug allows one to determine the
2257 culprit if slab objects become corrupted. Enabling
2258 slub_debug can create guard zones around objects and
2259 may poison objects when not in use. Also tracks the
2260 last alloc / free. For more information see
2261 Documentation/vm/slub.txt.
2263 slub_max_order= [MM, SLUB]
2264 Determines the maximum allowed order for slabs.
2265 A high setting may cause OOMs due to memory
2266 fragmentation. For more information see
2267 Documentation/vm/slub.txt.
2269 slub_min_objects= [MM, SLUB]
2270 The minimum number of objects per slab. SLUB will
2271 increase the slab order up to slub_max_order to
2272 generate a sufficiently large slab able to contain
2273 the number of objects indicated. The higher the number
2274 of objects the smaller the overhead of tracking slabs
2275 and the less frequently locks need to be acquired.
2276 For more information see Documentation/vm/slub.txt.
2278 slub_min_order= [MM, SLUB]
2279 Determines the mininum page order for slabs. Must be
2280 lower than slub_max_order.
2281 For more information see Documentation/vm/slub.txt.
2283 slub_nomerge [MM, SLUB]
2284 Disable merging of slabs with similar size. May be
2285 necessary if there is some reason to distinguish
2286 allocs to different slabs. Debug options disable
2287 merging on their own.
2288 For more information see Documentation/vm/slub.txt.
2290 smart2= [HW]
2291 Format: <io1>[,<io2>[,...,<io8>]]
2293 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2294 attempt to substitute SMP alternatives once at boot.
2296 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2297 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2298 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2299 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2300 smsc-ircc2.ircc_irq= [HW] IRQ line
2301 smsc-ircc2.ircc_dma= [HW] DMA channel
2302 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2303 0: Toshiba Satellite 1800 (GP data pin select)
2304 1: Fast pin select (default)
2305 2: ATC IRMode
2307 snd-ad1816a= [HW,ALSA]
2309 snd-ad1848= [HW,ALSA]
2311 snd-ali5451= [HW,ALSA]
2313 snd-als100= [HW,ALSA]
2315 snd-als4000= [HW,ALSA]
2317 snd-azt2320= [HW,ALSA]
2319 snd-cmi8330= [HW,ALSA]
2321 snd-cmipci= [HW,ALSA]
2323 snd-cs4231= [HW,ALSA]
2325 snd-cs4232= [HW,ALSA]
2327 snd-cs4236= [HW,ALSA]
2329 snd-cs4281= [HW,ALSA]
2331 snd-cs46xx= [HW,ALSA]
2333 snd-dt019x= [HW,ALSA]
2335 snd-dummy= [HW,ALSA]
2337 snd-emu10k1= [HW,ALSA]
2339 snd-ens1370= [HW,ALSA]
2341 snd-ens1371= [HW,ALSA]
2343 snd-es968= [HW,ALSA]
2345 snd-es1688= [HW,ALSA]
2347 snd-es18xx= [HW,ALSA]
2349 snd-es1938= [HW,ALSA]
2351 snd-es1968= [HW,ALSA]
2353 snd-fm801= [HW,ALSA]
2355 snd-gusclassic= [HW,ALSA]
2357 snd-gusextreme= [HW,ALSA]
2359 snd-gusmax= [HW,ALSA]
2361 snd-hdsp= [HW,ALSA]
2363 snd-ice1712= [HW,ALSA]
2365 snd-intel8x0= [HW,ALSA]
2367 snd-interwave= [HW,ALSA]
2369 snd-interwave-stb=
2370 [HW,ALSA]
2372 snd-korg1212= [HW,ALSA]
2374 snd-maestro3= [HW,ALSA]
2376 snd-mpu401= [HW,ALSA]
2378 snd-mtpav= [HW,ALSA]
2380 snd-nm256= [HW,ALSA]
2382 snd-opl3sa2= [HW,ALSA]
2384 snd-opti92x-ad1848=
2385 [HW,ALSA]
2387 snd-opti92x-cs4231=
2388 [HW,ALSA]
2390 snd-opti93x= [HW,ALSA]
2392 snd-pmac= [HW,ALSA]
2394 snd-rme32= [HW,ALSA]
2396 snd-rme96= [HW,ALSA]
2398 snd-rme9652= [HW,ALSA]
2400 snd-sb8= [HW,ALSA]
2402 snd-sb16= [HW,ALSA]
2404 snd-sbawe= [HW,ALSA]
2406 snd-serial= [HW,ALSA]
2408 snd-sgalaxy= [HW,ALSA]
2410 snd-sonicvibes= [HW,ALSA]
2412 snd-sun-amd7930=
2413 [HW,ALSA]
2415 snd-sun-cs4231= [HW,ALSA]
2417 snd-trident= [HW,ALSA]
2419 snd-usb-audio= [HW,ALSA,USB]
2421 snd-via82xx= [HW,ALSA]
2423 snd-virmidi= [HW,ALSA]
2425 snd-wavefront= [HW,ALSA]
2427 snd-ymfpci= [HW,ALSA]
2429 softlockup_panic=
2430 [KNL] Should the soft-lockup detector generate panics.
2432 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2433 See Documentation/sonypi.txt
2435 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2436 See Documentation/serial/specialix.txt.
2438 spia_io_base= [HW,MTD]
2439 spia_fio_base=
2440 spia_pedr=
2441 spia_peddr=
2443 sscape= [HW,OSS]
2444 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2446 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2447 See Documentation/scsi/st.txt.
2449 stacktrace [FTRACE]
2450 Enabled the stack tracer on boot up.
2452 sti= [PARISC,HW]
2453 Format: <num>
2454 Set the STI (builtin display/keyboard on the HP-PARISC
2455 machines) console (graphic card) which should be used
2456 as the initial boot-console.
2457 See also comment in drivers/video/console/sticore.c.
2459 sti_font= [HW]
2460 See comment in drivers/video/console/sticore.c.
2462 stifb= [HW]
2463 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2465 sunrpc.min_resvport=
2466 sunrpc.max_resvport=
2467 [NFS,SUNRPC]
2468 SunRPC servers often require that client requests
2469 originate from a privileged port (i.e. a port in the
2470 range 0 < portnr < 1024).
2471 An administrator who wishes to reserve some of these
2472 ports for other uses may adjust the range that the
2473 kernel's sunrpc client considers to be privileged
2474 using these two parameters to set the minimum and
2475 maximum port values.
2477 sunrpc.pool_mode=
2478 [NFS]
2479 Control how the NFS server code allocates CPUs to
2480 service thread pools. Depending on how many NICs
2481 you have and where their interrupts are bound, this
2482 option will affect which CPUs will do NFS serving.
2483 Note: this parameter cannot be changed while the
2484 NFS server is running.
2486 auto the server chooses an appropriate mode
2487 automatically using heuristics
2488 global a single global pool contains all CPUs
2489 percpu one pool for each CPU
2490 pernode one pool for each NUMA node (equivalent
2491 to global on non-NUMA machines)
2493 sunrpc.tcp_slot_table_entries=
2494 sunrpc.udp_slot_table_entries=
2495 [NFS,SUNRPC]
2496 Sets the upper limit on the number of simultaneous
2497 RPC calls that can be sent from the client to a
2498 server. Increasing these values may allow you to
2499 improve throughput, but will also increase the
2500 amount of memory reserved for use by the client.
2502 swiotlb= [IA-64] Number of I/O TLB slabs
2504 switches= [HW,M68k]
2506 sym53c416= [HW,SCSI]
2507 See header of drivers/scsi/sym53c416.c.
2509 sysrq_always_enabled
2510 [KNL]
2511 Ignore sysrq setting - this boot parameter will
2512 neutralize any effect of /proc/sys/kernel/sysrq.
2513 Useful for debugging.
2515 t128= [HW,SCSI]
2516 See header of drivers/scsi/t128.c.
2518 tdfx= [HW,DRM]
2520 test_suspend= [SUSPEND]
2521 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2522 standby suspend) as the system sleep state to briefly
2523 enter during system startup. The system is woken from
2524 this state using a wakeup-capable RTC alarm.
2526 thash_entries= [KNL,NET]
2527 Set number of hash buckets for TCP connection
2529 thermal.act= [HW,ACPI]
2530 -1: disable all active trip points in all thermal zones
2531 <degrees C>: override all lowest active trip points
2533 thermal.crt= [HW,ACPI]
2534 -1: disable all critical trip points in all thermal zones
2535 <degrees C>: override all critical trip points
2537 thermal.nocrt= [HW,ACPI]
2538 Set to disable actions on ACPI thermal zone
2539 critical and hot trip points.
2541 thermal.off= [HW,ACPI]
2542 1: disable ACPI thermal control
2544 thermal.psv= [HW,ACPI]
2545 -1: disable all passive trip points
2546 <degrees C>: override all passive trip points to this
2547 value
2549 thermal.tzp= [HW,ACPI]
2550 Specify global default ACPI thermal zone polling rate
2551 <deci-seconds>: poll all this frequency
2552 0: no polling (default)
2554 tmscsim= [HW,SCSI]
2555 See comment before function dc390_setup() in
2556 drivers/scsi/tmscsim.c.
2558 topology= [S390]
2559 Format: {off | on}
2560 Specify if the kernel should make use of the cpu
2561 topology informations if the hardware supports these.
2562 The scheduler will make use of these informations and
2563 e.g. base its process migration decisions on it.
2564 Default is off.
2566 tp720= [HW,PS2]
2568 trace_buf_size=nn[KMG]
2569 [FTRACE] will set tracing buffer size.
2571 trace_event=[event-list]
2572 [FTRACE] Set and start specified trace events in order
2573 to facilitate early boot debugging.
2574 See also Documentation/trace/events.txt
2576 trix= [HW,OSS] MediaTrix AudioTrix Pro
2577 Format:
2578 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2580 tsc= Disable clocksource-must-verify flag for TSC.
2581 Format: <string>
2582 [x86] reliable: mark tsc clocksource as reliable, this
2583 disables clocksource verification at runtime.
2584 Used to enable high-resolution timer mode on older
2585 hardware, and in virtualized environment.
2586 [x86] noirqtime: Do not use TSC to do irq accounting.
2587 Used to run time disable IRQ_TIME_ACCOUNTING on any
2588 platforms where RDTSC is slow and this accounting
2589 can add overhead.
2591 turbografx.map[2|3]= [HW,JOY]
2592 TurboGraFX parallel port interface
2593 Format:
2594 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2595 See also Documentation/input/joystick-parport.txt
2597 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2598 See header of drivers/scsi/u14-34f.c.
2600 uart401= [HW,OSS]
2601 Format: <io>,<irq>
2603 uart6850= [HW,OSS]
2604 Format: <io>,<irq>
2606 uhci-hcd.ignore_oc=
2607 [USB] Ignore overcurrent events (default N).
2608 Some badly-designed motherboards generate lots of
2609 bogus events, for ports that aren't wired to
2610 anything. Set this parameter to avoid log spamming.
2611 Note that genuine overcurrent events won't be
2612 reported either.
2614 unknown_nmi_panic
2615 [X86]
2616 Set unknown_nmi_panic=1 early on boot.
2618 usbcore.autosuspend=
2619 [USB] The autosuspend time delay (in seconds) used
2620 for newly-detected USB devices (default 2). This
2621 is the time required before an idle device will be
2622 autosuspended. Devices for which the delay is set
2623 to a negative value won't be autosuspended at all.
2625 usbcore.usbfs_snoop=
2626 [USB] Set to log all usbfs traffic (default 0 = off).
2628 usbcore.blinkenlights=
2629 [USB] Set to cycle leds on hubs (default 0 = off).
2631 usbcore.old_scheme_first=
2632 [USB] Start with the old device initialization
2633 scheme (default 0 = off).
2635 usbcore.use_both_schemes=
2636 [USB] Try the other device initialization scheme
2637 if the first one fails (default 1 = enabled).
2639 usbcore.initial_descriptor_timeout=
2640 [USB] Specifies timeout for the initial 64-byte
2641 USB_REQ_GET_DESCRIPTOR request in milliseconds
2642 (default 5000 = 5.0 seconds).
2644 usbhid.mousepoll=
2645 [USBHID] The interval which mice are to be polled at.
2647 usb-storage.delay_use=
2648 [UMS] The delay in seconds before a new device is
2649 scanned for Logical Units (default 5).
2651 usb-storage.quirks=
2652 [UMS] A list of quirks entries to supplement or
2653 override the built-in unusual_devs list. List
2654 entries are separated by commas. Each entry has
2655 the form VID:PID:Flags where VID and PID are Vendor
2656 and Product ID values (4-digit hex numbers) and
2657 Flags is a set of characters, each corresponding
2658 to a common usb-storage quirk flag as follows:
2659 a = SANE_SENSE (collect more than 18 bytes
2660 of sense data);
2661 b = BAD_SENSE (don't collect more than 18
2662 bytes of sense data);
2663 c = FIX_CAPACITY (decrease the reported
2664 device capacity by one sector);
2665 h = CAPACITY_HEURISTICS (decrease the
2666 reported device capacity by one
2667 sector if the number is odd);
2668 i = IGNORE_DEVICE (don't bind to this
2669 device);
2670 l = NOT_LOCKABLE (don't try to lock and
2671 unlock ejectable media);
2672 m = MAX_SECTORS_64 (don't transfer more
2673 than 64 sectors = 32 KB at a time);
2674 o = CAPACITY_OK (accept the capacity
2675 reported by the device);
2676 r = IGNORE_RESIDUE (the device reports
2677 bogus residue values);
2678 s = SINGLE_LUN (the device has only one
2679 Logical Unit);
2680 w = NO_WP_DETECT (don't test whether the
2681 medium is write-protected).
2682 Example: quirks=0419:aaf5:rl,0421:0433:rc
2684 userpte=
2685 [X86] Flags controlling user PTE allocations.
2687 nohigh = do not allocate PTE pages in
2688 HIGHMEM regardless of setting
2689 of CONFIG_HIGHPTE.
2691 vdso= [X86,SH]
2692 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2693 vdso=1: enable VDSO (default)
2694 vdso=0: disable VDSO mapping
2696 vdso32= [X86]
2697 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2698 vdso32=1: enable 32-bit VDSO (default)
2699 vdso32=0: disable 32-bit VDSO mapping
2701 vector= [IA-64,SMP]
2702 vector=percpu: enable percpu vector domain
2704 video= [FB] Frame buffer configuration
2705 See Documentation/fb/modedb.txt.
2707 vga= [BOOT,X86-32] Select a particular video mode
2708 See Documentation/x86/boot.txt and
2709 Documentation/svga.txt.
2710 Use vga=ask for menu.
2711 This is actually a boot loader parameter; the value is
2712 passed to the kernel using a special protocol.
2714 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2715 size of <nn>. This can be used to increase the
2716 minimum size (128MB on x86). It can also be used to
2717 decrease the size and leave more room for directly
2718 mapped kernel RAM.
2720 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2721 Format: <command>
2723 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2724 Format: <command>
2726 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2727 Format: <command>
2729 vt.default_blu= [VT]
2730 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2731 Change the default blue palette of the console.
2732 This is a 16-member array composed of values
2733 ranging from 0-255.
2735 vt.default_grn= [VT]
2736 Format: <green0>,<green1>,<green2>,...,<green15>
2737 Change the default green palette of the console.
2738 This is a 16-member array composed of values
2739 ranging from 0-255.
2741 vt.default_red= [VT]
2742 Format: <red0>,<red1>,<red2>,...,<red15>
2743 Change the default red palette of the console.
2744 This is a 16-member array composed of values
2745 ranging from 0-255.
2747 vt.default_utf8=
2748 [VT]
2749 Format=<0|1>
2750 Set system-wide default UTF-8 mode for all tty's.
2751 Default is 1, i.e. UTF-8 mode is enabled for all
2752 newly opened terminals.
2754 waveartist= [HW,OSS]
2755 Format: <io>,<irq>,<dma>,<dma2>
2757 wd33c93= [HW,SCSI]
2758 See header of drivers/scsi/wd33c93.c.
2760 wd7000= [HW,SCSI]
2761 See header of drivers/scsi/wd7000.c.
2763 wdt= [WDT] Watchdog
2764 See Documentation/watchdog/wdt.txt.
2766 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2767 default x2apic cluster mode on platforms
2768 supporting x2apic.
2770 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2771 xd_geo= See header of drivers/block/xd.c.
2773 xirc2ps_cs= [NET,PCMCIA]
2774 Format:
2775 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2777 ______________________________________________________________________
2779 TODO:
2781 Add documentation for ALSA options.
2782 Add more DRM drivers.