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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 HW Appropriate hardware is enabled.
52 IA-64 IA-64 architecture is enabled.
53 IMA Integrity measurement architecture is enabled.
54 IOSCHED More than one I/O scheduler is enabled.
55 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
56 ISAPNP ISA PnP code is enabled.
57 ISDN Appropriate ISDN support is enabled.
58 JOY Appropriate joystick support is enabled.
59 KMEMTRACE kmemtrace is enabled.
60 LIBATA Libata driver is enabled
61 LP Printer support is enabled.
62 LOOP Loopback device support is enabled.
63 M68k M68k architecture is enabled.
64 These options have more detailed description inside of
65 Documentation/m68k/kernel-options.txt.
66 MCA MCA bus support is enabled.
67 MDA MDA console support is enabled.
68 MOUSE Appropriate mouse support is enabled.
69 MSI Message Signaled Interrupts (PCI).
70 MTD MTD (Memory Technology Device) support is enabled.
71 NET Appropriate network support is enabled.
72 NUMA NUMA support is enabled.
73 GENERIC_TIME The generic timeofday code is enabled.
74 NFS Appropriate NFS support is enabled.
75 OSS OSS sound support is enabled.
76 PV_OPS A paravirtualized kernel is enabled.
77 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
78 PARISC The PA-RISC architecture is enabled.
79 PCI PCI bus support is enabled.
80 PCIE PCI Express support is enabled.
81 PCMCIA The PCMCIA subsystem is enabled.
82 PNP Plug & Play support is enabled.
83 PPC PowerPC architecture is enabled.
84 PPT Parallel port support is enabled.
85 PS2 Appropriate PS/2 support is enabled.
86 RAM RAM disk support is enabled.
87 ROOTPLUG The example Root Plug LSM is enabled.
88 S390 S390 architecture is enabled.
89 SCSI Appropriate SCSI support is enabled.
90 A lot of drivers has their options described inside of
91 Documentation/scsi/.
92 SECURITY Different security models are enabled.
93 SELINUX SELinux support is enabled.
94 SERIAL Serial support is enabled.
95 SH SuperH architecture is enabled.
96 SMP The kernel is an SMP kernel.
97 SPARC Sparc architecture is enabled.
98 SWSUSP Software suspend (hibernation) is enabled.
99 SUSPEND System suspend states are enabled.
100 FTRACE Function tracing enabled.
101 TS Appropriate touchscreen support is enabled.
102 UMS USB Mass Storage support is enabled.
103 USB USB support is enabled.
104 USBHID USB Human Interface Device support is enabled.
105 V4L Video For Linux support is enabled.
106 VGA The VGA console has been enabled.
107 VT Virtual terminal support is enabled.
108 WDT Watchdog support is enabled.
109 XT IBM PC/XT MFM hard disk support is enabled.
110 X86-32 X86-32, aka i386 architecture is enabled.
111 X86-64 X86-64 architecture is enabled.
112 More X86-64 boot options can be found in
113 Documentation/x86/x86_64/boot-options.txt .
114 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
116 In addition, the following text indicates that the option:
118 BUGS= Relates to possible processor bugs on the said processor.
119 KNL Is a kernel start-up parameter.
120 BOOT Is a boot loader parameter.
122 Parameters denoted with BOOT are actually interpreted by the boot
123 loader, and have no meaning to the kernel directly.
124 Do not modify the syntax of boot loader parameters without extreme
125 need or coordination with <Documentation/x86/boot.txt>.
127 There are also arch-specific kernel-parameters not documented here.
128 See for example <Documentation/x86/x86_64/boot-options.txt>.
130 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
131 a trailing = on the name of any parameter states that that parameter will
132 be entered as an environment variable, whereas its absence indicates that
133 it will appear as a kernel argument readable via /proc/cmdline by programs
134 running once the system is up.
136 The number of kernel parameters is not limited, but the length of the
137 complete command line (parameters including spaces etc.) is limited to
138 a fixed number of characters. This limit depends on the architecture
139 and is between 256 and 4096 characters. It is defined in the file
140 ./include/asm/setup.h as COMMAND_LINE_SIZE.
143 acpi= [HW,ACPI,X86]
144 Advanced Configuration and Power Interface
145 Format: { force | off | ht | strict | noirq | rsdt }
146 force -- enable ACPI if default was off
147 off -- disable ACPI if default was on
148 noirq -- do not use ACPI for IRQ routing
149 ht -- run only enough ACPI to enable Hyper Threading
150 strict -- Be less tolerant of platforms that are not
151 strictly ACPI specification compliant.
152 rsdt -- prefer RSDT over (default) XSDT
154 See also Documentation/power/pm.txt, pci=noacpi
156 acpi_apic_instance= [ACPI, IOAPIC]
157 Format: <int>
158 2: use 2nd APIC table, if available
159 1,0: use 1st APIC table
160 default: 0
162 acpi_backlight= [HW,ACPI]
163 acpi_backlight=vendor
164 acpi_backlight=video
165 If set to vendor, prefer vendor specific driver
166 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
167 of the ACPI video.ko driver.
169 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
170 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
171 Format: <int>
172 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
173 debug output. Bits in debug_layer correspond to a
174 _COMPONENT in an ACPI source file, e.g.,
175 #define _COMPONENT ACPI_PCI_COMPONENT
176 Bits in debug_level correspond to a level in
177 ACPI_DEBUG_PRINT statements, e.g.,
178 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
179 The debug_level mask defaults to "info". See
180 Documentation/acpi/debug.txt for more information about
181 debug layers and levels.
183 Enable processor driver info messages:
184 acpi.debug_layer=0x20000000
185 Enable PCI/PCI interrupt routing info messages:
186 acpi.debug_layer=0x400000
187 Enable AML "Debug" output, i.e., stores to the Debug
188 object while interpreting AML:
189 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
190 Enable all messages related to ACPI hardware:
191 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
193 Some values produce so much output that the system is
194 unusable. The "log_buf_len" parameter may be useful
195 if you need to capture more output.
197 acpi_display_output= [HW,ACPI]
198 acpi_display_output=vendor
199 acpi_display_output=video
200 See above.
202 acpi_irq_balance [HW,ACPI]
203 ACPI will balance active IRQs
204 default in APIC mode
206 acpi_irq_nobalance [HW,ACPI]
207 ACPI will not move active IRQs (default)
208 default in PIC mode
210 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
211 Format: <irq>,<irq>...
213 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
214 use by PCI
215 Format: <irq>,<irq>...
217 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
219 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
220 Format: To spoof as Windows 98: ="Microsoft Windows"
222 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
223 acpi_osi="string1" # add string1 -- only one string
224 acpi_osi="!string2" # remove built-in string2
225 acpi_osi= # disable all strings
227 acpi_pm_good [X86]
228 Override the pmtimer bug detection: force the kernel
229 to assume that this machine's pmtimer latches its value
230 and always returns good values.
232 acpi.power_nocheck= [HW,ACPI]
233 Format: 1/0 enable/disable the check of power state.
234 On some bogus BIOS the _PSC object/_STA object of
235 power resource can't return the correct device power
236 state. In such case it is unneccessary to check its
237 power state again in power transition.
238 1 : disable the power state check
240 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
241 Format: { level | edge | high | low }
243 acpi_serialize [HW,ACPI] force serialization of AML methods
245 acpi_skip_timer_override [HW,ACPI]
246 Recognize and ignore IRQ0/pin2 Interrupt Override.
247 For broken nForce2 BIOS resulting in XT-PIC timer.
249 acpi_sleep= [HW,ACPI] Sleep options
250 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
251 old_ordering, s4_nonvs }
252 See Documentation/power/video.txt for information on
253 s3_bios and s3_mode.
254 s3_beep is for debugging; it makes the PC's speaker beep
255 as soon as the kernel's real-mode entry point is called.
256 s4_nohwsig prevents ACPI hardware signature from being
257 used during resume from hibernation.
258 old_ordering causes the ACPI 1.0 ordering of the _PTS
259 control method, with respect to putting devices into
260 low power states, to be enforced (the ACPI 2.0 ordering
261 of _PTS is used by default).
262 s4_nonvs prevents the kernel from saving/restoring the
263 ACPI NVS memory during hibernation.
265 acpi_use_timer_override [HW,ACPI]
266 Use timer override. For some broken Nvidia NF5 boards
267 that require a timer override, but don't have HPET
269 acpi_enforce_resources= [ACPI]
270 { strict | lax | no }
271 Check for resource conflicts between native drivers
272 and ACPI OperationRegions (SystemIO and SystemMemory
273 only). IO ports and memory declared in ACPI might be
274 used by the ACPI subsystem in arbitrary AML code and
275 can interfere with legacy drivers.
276 strict (default): access to resources claimed by ACPI
277 is denied; legacy drivers trying to access reserved
278 resources will fail to bind to device using them.
279 lax: access to resources claimed by ACPI is allowed;
280 legacy drivers trying to access reserved resources
281 will bind successfully but a warning message is logged.
282 no: ACPI OperationRegions are not marked as reserved,
283 no further checks are performed.
285 ad1848= [HW,OSS]
286 Format: <io>,<irq>,<dma>,<dma2>,<type>
288 add_efi_memmap [EFI; X86] Include EFI memory map in
289 kernel's map of available physical RAM.
291 advansys= [HW,SCSI]
292 See header of drivers/scsi/advansys.c.
294 advwdt= [HW,WDT] Advantech WDT
295 Format: <iostart>,<iostop>
297 aedsp16= [HW,OSS] Audio Excel DSP 16
298 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
299 See also header of sound/oss/aedsp16.c.
301 agp= [AGP]
302 { off | try_unsupported }
303 off: disable AGP support
304 try_unsupported: try to drive unsupported chipsets
305 (may crash computer or cause data corruption)
307 aha152x= [HW,SCSI]
308 See Documentation/scsi/aha152x.txt.
310 aha1542= [HW,SCSI]
311 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
313 aic7xxx= [HW,SCSI]
314 See Documentation/scsi/aic7xxx.txt.
316 aic79xx= [HW,SCSI]
317 See Documentation/scsi/aic79xx.txt.
319 amd_iommu= [HW,X86-84]
320 Pass parameters to the AMD IOMMU driver in the system.
321 Possible values are:
322 isolate - enable device isolation (each device, as far
323 as possible, will get its own protection
324 domain) [default]
325 share - put every device behind one IOMMU into the
326 same protection domain
327 fullflush - enable flushing of IO/TLB entries when
328 they are unmapped. Otherwise they are
329 flushed before they will be reused, which
330 is a lot of faster
332 amd_iommu_size= [HW,X86-64]
333 Define the size of the aperture for the AMD IOMMU
334 driver. Possible values are:
335 '32M', '64M' (default), '128M', '256M', '512M', '1G'
337 amijoy.map= [HW,JOY] Amiga joystick support
338 Map of devices attached to JOY0DAT and JOY1DAT
339 Format: <a>,<b>
340 See also Documentation/kernel/input/joystick.txt
342 analog.map= [HW,JOY] Analog joystick and gamepad support
343 Specifies type or capabilities of an analog joystick
344 connected to one of 16 gameports
345 Format: <type1>,<type2>,..<type16>
347 apc= [HW,SPARC]
348 Power management functions (SPARCstation-4/5 + deriv.)
349 Format: noidle
350 Disable APC CPU standby support. SPARCstation-Fox does
351 not play well with APC CPU idle - disable it if you have
352 APC and your system crashes randomly.
354 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
355 Change the output verbosity whilst booting
356 Format: { quiet (default) | verbose | debug }
357 Change the amount of debugging information output
358 when initialising the APIC and IO-APIC components.
360 apm= [APM] Advanced Power Management
361 See header of arch/x86/kernel/apm_32.c.
363 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
364 Format: <io>,<irq>,<nodeID>
366 ataflop= [HW,M68k]
368 atarimouse= [HW,MOUSE] Atari Mouse
370 atascsi= [HW,SCSI] Atari SCSI
372 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
373 EzKey and similar keyboards
375 atkbd.reset= [HW] Reset keyboard during initialization
377 atkbd.set= [HW] Select keyboard code set
378 Format: <int> (2 = AT (default), 3 = PS/2)
380 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
381 keyboards
383 atkbd.softraw= [HW] Choose between synthetic and real raw mode
384 Format: <bool> (0 = real, 1 = synthetic (default))
386 atkbd.softrepeat= [HW]
387 Use software keyboard repeat
389 autotest [IA64]
391 baycom_epp= [HW,AX25]
392 Format: <io>,<mode>
394 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
395 Format: <io>,<mode>
396 See header of drivers/net/hamradio/baycom_par.c.
398 baycom_ser_fdx= [HW,AX25]
399 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
400 Format: <io>,<irq>,<mode>[,<baud>]
401 See header of drivers/net/hamradio/baycom_ser_fdx.c.
403 baycom_ser_hdx= [HW,AX25]
404 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
405 Format: <io>,<irq>,<mode>
406 See header of drivers/net/hamradio/baycom_ser_hdx.c.
408 boot_delay= Milliseconds to delay each printk during boot.
409 Values larger than 10 seconds (10000) are changed to
410 no delay (0).
411 Format: integer
413 bootmem_debug [KNL] Enable bootmem allocator debug messages.
415 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
416 bttv.radio= Most important insmod options are available as
417 kernel args too.
418 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
419 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
421 BusLogic= [HW,SCSI]
422 See drivers/scsi/BusLogic.c, comment before function
423 BusLogic_ParseDriverOptions().
425 c101= [NET] Moxa C101 synchronous serial card
427 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
428 Sometimes CPU hardware bugs make them report the cache
429 size incorrectly. The kernel will attempt work arounds
430 to fix known problems, but for some CPUs it is not
431 possible to determine what the correct size should be.
432 This option provides an override for these situations.
434 capability.disable=
435 [SECURITY] Disable capabilities. This would normally
436 be used only if an alternative security model is to be
437 configured. Potentially dangerous and should only be
438 used if you are entirely sure of the consequences.
440 ccw_timeout_log [S390]
441 See Documentation/s390/CommonIO for details.
443 cgroup_disable= [KNL] Disable a particular controller
444 Format: {name of the controller(s) to disable}
445 {Currently supported controllers - "memory"}
447 checkreqprot [SELINUX] Set initial checkreqprot flag value.
448 Format: { "0" | "1" }
449 See security/selinux/Kconfig help text.
450 0 -- check protection applied by kernel (includes
451 any implied execute protection).
452 1 -- check protection requested by application.
453 Default value is set via a kernel config option.
454 Value can be changed at runtime via
455 /selinux/checkreqprot.
457 cio_ignore= [S390]
458 See Documentation/s390/CommonIO for details.
460 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
461 [Deprecated]
462 Forces specified clocksource (if available) to be used
463 when calculating gettimeofday(). If specified
464 clocksource is not available, it defaults to PIT.
465 Format: { pit | tsc | cyclone | pmtmr }
467 clocksource= [GENERIC_TIME] Override the default clocksource
468 Format: <string>
469 Override the default clocksource and use the clocksource
470 with the name specified.
471 Some clocksource names to choose from, depending on
472 the platform:
473 [all] jiffies (this is the base, fallback clocksource)
474 [ACPI] acpi_pm
475 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
476 pxa_timer,timer3,32k_counter,timer0_1
477 [AVR32] avr32
478 [X86-32] pit,hpet,tsc,vmi-timer;
479 scx200_hrt on Geode; cyclone on IBM x440
480 [MIPS] MIPS
481 [PARISC] cr16
482 [S390] tod
483 [SH] SuperH
484 [SPARC64] tick
485 [X86-64] hpet,tsc
487 clearcpuid=BITNUM [X86]
488 Disable CPUID feature X for the kernel. See
489 arch/x86/include/asm/cpufeature.h for the valid bit
490 numbers. Note the Linux specific bits are not necessarily
491 stable over kernel options, but the vendor specific
492 ones should be.
493 Also note that user programs calling CPUID directly
494 or using the feature without checking anything
495 will still see it. This just prevents it from
496 being used by the kernel or shown in /proc/cpuinfo.
497 Also note the kernel might malfunction if you disable
498 some critical bits.
500 code_bytes [X86] How many bytes of object code to print
501 in an oops report.
502 Range: 0 - 8192
503 Default: 64
505 com20020= [HW,NET] ARCnet - COM20020 chipset
506 Format:
507 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
509 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
510 Format: <io>[,<irq>]
512 com90xx= [HW,NET]
513 ARCnet - COM90xx chipset (memory-mapped buffers)
514 Format: <io>[,<irq>[,<memstart>]]
516 condev= [HW,S390] console device
517 conmode=
519 console= [KNL] Output console device and options.
521 tty<n> Use the virtual console device <n>.
523 ttyS<n>[,options]
524 ttyUSB0[,options]
525 Use the specified serial port. The options are of
526 the form "bbbbpnf", where "bbbb" is the baud rate,
527 "p" is parity ("n", "o", or "e"), "n" is number of
528 bits, and "f" is flow control ("r" for RTS or
529 omit it). Default is "9600n8".
531 See Documentation/serial-console.txt for more
532 information. See
533 Documentation/networking/netconsole.txt for an
534 alternative.
536 uart[8250],io,<addr>[,options]
537 uart[8250],mmio,<addr>[,options]
538 Start an early, polled-mode console on the 8250/16550
539 UART at the specified I/O port or MMIO address,
540 switching to the matching ttyS device later. The
541 options are the same as for ttyS, above.
543 If the device connected to the port is not a TTY but a braille
544 device, prepend "brl," before the device type, for instance
545 console=brl,ttyS0
546 For now, only VisioBraille is supported.
548 coredump_filter=
549 [KNL] Change the default value for
550 /proc/<pid>/coredump_filter.
551 See also Documentation/filesystems/proc.txt.
553 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
554 Format:
555 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
557 crashkernel=nn[KMG]@ss[KMG]
558 [KNL] Reserve a chunk of physical memory to
559 hold a kernel to switch to with kexec on panic.
561 crashkernel=range1:size1[,range2:size2,...][@offset]
562 [KNL] Same as above, but depends on the memory
563 in the running system. The syntax of range is
564 start-[end] where start and end are both
565 a memory unit (amount[KMG]). See also
566 Documentation/kdump/kdump.txt for a example.
568 cs89x0_dma= [HW,NET]
569 Format: <dma>
571 cs89x0_media= [HW,NET]
572 Format: { rj45 | aui | bnc }
574 dasd= [HW,NET]
575 See header of drivers/s390/block/dasd_devmap.c.
577 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
578 (one device per port)
579 Format: <port#>,<type>
580 See also Documentation/input/joystick-parport.txt
582 debug [KNL] Enable kernel debugging (events log level).
584 debug_locks_verbose=
585 [KNL] verbose self-tests
586 Format=<0|1>
587 Print debugging info while doing the locking API
588 self-tests.
589 We default to 0 (no extra messages), setting it to
590 1 will print _a lot_ more information - normally
591 only useful to kernel developers.
593 debug_objects [KNL] Enable object debugging
595 no_debug_objects
596 [KNL] Disable object debugging
598 debugpat [X86] Enable PAT debugging
600 decnet.addr= [HW,NET]
601 Format: <area>[,<node>]
602 See also Documentation/networking/decnet.txt.
604 default_hugepagesz=
605 [same as hugepagesz=] The size of the default
606 HugeTLB page size. This is the size represented by
607 the legacy /proc/ hugepages APIs, used for SHM, and
608 default size when mounting hugetlbfs filesystems.
609 Defaults to the default architecture's huge page size
610 if not specified.
612 dhash_entries= [KNL]
613 Set number of hash buckets for dentry cache.
615 digi= [HW,SERIAL]
616 IO parameters + enable/disable command.
618 digiepca= [HW,SERIAL]
619 See drivers/char/README.epca and
620 Documentation/serial/digiepca.txt.
622 disable_mtrr_cleanup [X86]
623 The kernel tries to adjust MTRR layout from continuous
624 to discrete, to make X server driver able to add WB
625 entry later. This parameter disables that.
627 disable_mtrr_trim [X86, Intel and AMD only]
628 By default the kernel will trim any uncacheable
629 memory out of your available memory pool based on
630 MTRR settings. This parameter disables that behavior,
631 possibly causing your machine to run very slowly.
633 disable_timer_pin_1 [X86]
634 Disable PIN 1 of APIC timer
635 Can be useful to work around chipset bugs.
637 dmasound= [HW,OSS] Sound subsystem buffers
639 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
640 this option disables the debugging code at boot.
642 dma_debug_entries=<number>
643 This option allows to tune the number of preallocated
644 entries for DMA-API debugging code. One entry is
645 required per DMA-API allocation. Use this if the
646 DMA-API debugging code disables itself because the
647 architectural default is too low.
649 dscc4.setup= [NET]
651 dtc3181e= [HW,SCSI]
653 dynamic_printk Enables pr_debug()/dev_dbg() calls if
654 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
655 These can also be switched on/off via
656 <debugfs>/dynamic_printk/modules
658 earlycon= [KNL] Output early console device and options.
659 uart[8250],io,<addr>[,options]
660 uart[8250],mmio,<addr>[,options]
661 Start an early, polled-mode console on the 8250/16550
662 UART at the specified I/O port or MMIO address.
663 The options are the same as for ttyS, above.
665 earlyprintk= [X86,SH,BLACKFIN]
666 earlyprintk=vga
667 earlyprintk=serial[,ttySn[,baudrate]]
668 earlyprintk=dbgp
670 Append ",keep" to not disable it when the real console
671 takes over.
673 Only vga or serial or usb debug port at a time.
675 Currently only ttyS0 and ttyS1 are supported.
677 Interaction with the standard serial driver is not
678 very good.
680 The VGA output is eventually overwritten by the real
681 console.
683 eata= [HW,SCSI]
685 edd= [EDD]
686 Format: {"off" | "on" | "skip[mbr]"}
688 eisa_irq_edge= [PARISC,HW]
689 See header of drivers/parisc/eisa.c.
691 elanfreq= [X86-32]
692 See comment before function elanfreq_setup() in
693 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
695 elevator= [IOSCHED]
696 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
697 See Documentation/block/as-iosched.txt and
698 Documentation/block/deadline-iosched.txt for details.
700 elfcorehdr= [IA64,PPC,SH,X86]
701 Specifies physical address of start of kernel core
702 image elf header. Generally kexec loader will
703 pass this option to capture kernel.
704 See Documentation/kdump/kdump.txt for details.
706 enable_mtrr_cleanup [X86]
707 The kernel tries to adjust MTRR layout from continuous
708 to discrete, to make X server driver able to add WB
709 entry later. This parameter enables that.
711 enable_timer_pin_1 [X86]
712 Enable PIN 1 of APIC timer
713 Can be useful to work around chipset bugs
714 (in particular on some ATI chipsets).
715 The kernel tries to set a reasonable default.
717 enforcing [SELINUX] Set initial enforcing status.
718 Format: {"0" | "1"}
719 See security/selinux/Kconfig help text.
720 0 -- permissive (log only, no denials).
721 1 -- enforcing (deny and log).
722 Default value is 0.
723 Value can be changed at runtime via /selinux/enforce.
725 ether= [HW,NET] Ethernet cards parameters
726 This option is obsoleted by the "netdev=" option, which
727 has equivalent usage. See its documentation for details.
729 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
730 Format: <io>[,<irq>]
732 failslab=
733 fail_page_alloc=
734 fail_make_request=[KNL]
735 General fault injection mechanism.
736 Format: <interval>,<probability>,<space>,<times>
737 See also /Documentation/fault-injection/.
739 fd_mcs= [HW,SCSI]
740 See header of drivers/scsi/fd_mcs.c.
742 fdomain= [HW,SCSI]
743 See header of drivers/scsi/fdomain.c.
745 floppy= [HW]
746 See Documentation/blockdev/floppy.txt.
748 force_pal_cache_flush
749 [IA-64] Avoid check_sal_cache_flush which may hang on
750 buggy SAL_CACHE_FLUSH implementations. Using this
751 parameter will force ia64_sal_cache_flush to call
752 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
754 ftrace=[tracer]
755 [ftrace] will set and start the specified tracer
756 as early as possible in order to facilitate early
757 boot debugging.
759 ftrace_dump_on_oops
760 [ftrace] will dump the trace buffers on oops.
762 gamecon.map[2|3]=
763 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
764 support via parallel port (up to 5 devices per port)
765 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
766 See also Documentation/input/joystick-parport.txt
768 gamma= [HW,DRM]
770 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
771 Format: off | on
772 default: on
774 gdth= [HW,SCSI]
775 See header of drivers/scsi/gdth.c.
777 gpt [EFI] Forces disk with valid GPT signature but
778 invalid Protective MBR to be treated as GPT.
780 gvp11= [HW,SCSI]
782 hashdist= [KNL,NUMA] Large hashes allocated during boot
783 are distributed across NUMA nodes. Defaults on
784 for 64bit NUMA, off otherwise.
785 Format: 0 | 1 (for off | on)
787 hcl= [IA-64] SGI's Hardware Graph compatibility layer
789 hd= [EIDE] (E)IDE hard drive subsystem geometry
790 Format: <cyl>,<head>,<sect>
792 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
793 size of <nn>. This works even on boxes that have no
794 highmem otherwise. This also works to reduce highmem
795 size on bigger boxes.
797 highres= [KNL] Enable/disable high resolution timer mode.
798 Valid parameters: "on", "off"
799 Default: "on"
801 hisax= [HW,ISDN]
802 See Documentation/isdn/README.HiSax.
804 hlt [BUGS=ARM,SH]
806 hpet= [X86-32,HPET] option to control HPET usage
807 Format: { enable (default) | disable | force |
808 verbose }
809 disable: disable HPET and use PIT instead
810 force: allow force enabled of undocumented chips (ICH4,
811 VIA, nVidia)
812 verbose: show contents of HPET registers during setup
814 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
815 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
816 On x86-64 and powerpc, this option can be specified
817 multiple times interleaved with hugepages= to reserve
818 huge pages of different sizes. Valid pages sizes on
819 x86-64 are 2M (when the CPU supports "pse") and 1G
820 (when the CPU supports the "pdpe1gb" cpuinfo flag)
821 Note that 1GB pages can only be allocated at boot time
822 using hugepages= and not freed afterwards.
824 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
825 terminal devices. Valid values: 0..8
826 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
827 If specified, z/VM IUCV HVC accepts connections
828 from listed z/VM user IDs only.
830 i2c_bus= [HW] Override the default board specific I2C bus speed
831 or register an additional I2C bus that is not
832 registered from board initialization code.
833 Format:
834 <bus_id>,<clkrate>
836 i8042.debug [HW] Toggle i8042 debug mode
837 i8042.direct [HW] Put keyboard port into non-translated mode
838 i8042.dumbkbd [HW] Pretend that controller can only read data from
839 keyboard and cannot control its state
840 (Don't attempt to blink the leds)
841 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
842 i8042.nokbd [HW] Don't check/create keyboard port
843 i8042.noloop [HW] Disable the AUX Loopback command while probing
844 for the AUX port
845 i8042.nomux [HW] Don't check presence of an active multiplexing
846 controller
847 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
848 controllers
849 i8042.panicblink=
850 [HW] Frequency with which keyboard LEDs should blink
851 when kernel panics (default is 0.5 sec)
852 i8042.reset [HW] Reset the controller during init and cleanup
853 i8042.unlock [HW] Unlock (ignore) the keylock
855 i810= [HW,DRM]
857 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
858 indicates that the driver is running on unsupported
859 hardware.
860 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
861 does not match list of supported models.
862 i8k.power_status
863 [HW] Report power status in /proc/i8k
864 (disabled by default)
865 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
866 capability is set.
868 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
869 See Documentation/mca.txt.
871 icn= [HW,ISDN]
872 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
874 ide-core.nodma= [HW] (E)IDE subsystem
875 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
876 .vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom
877 .chs .ignore_cable are additional options
878 See Documentation/ide/ide.txt.
880 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
881 See Documentation/ide/ide.txt.
883 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
884 Claim all unknown PCI IDE storage controllers.
886 idle= [X86]
887 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
888 Poll forces a polling idle loop that can slightly
889 improve the performance of waking up a idle CPU, but
890 will use a lot of power and make the system run hot.
891 Not recommended.
892 idle=mwait: On systems which support MONITOR/MWAIT but
893 the kernel chose to not use it because it doesn't save
894 as much power as a normal idle loop, use the
895 MONITOR/MWAIT idle loop anyways. Performance should be
896 the same as idle=poll.
897 idle=halt: Halt is forced to be used for CPU idle.
898 In such case C2/C3 won't be used again.
899 idle=nomwait: Disable mwait for CPU C-states
901 ignore_loglevel [KNL]
902 Ignore loglevel setting - this will print /all/
903 kernel messages to the console. Useful for debugging.
905 ihash_entries= [KNL]
906 Set number of hash buckets for inode cache.
908 ima_audit= [IMA]
909 Format: { "0" | "1" }
910 0 -- integrity auditing messages. (Default)
911 1 -- enable informational integrity auditing messages.
913 ima_hash= [IMA]
914 Formt: { "sha1" | "md5" }
915 default: "sha1"
917 in2000= [HW,SCSI]
918 See header of drivers/scsi/in2000.c.
920 init= [KNL]
921 Format: <full_path>
922 Run specified binary instead of /sbin/init as init
923 process.
925 initcall_debug [KNL] Trace initcalls as they are executed. Useful
926 for working out where the kernel is dying during
927 startup.
929 initrd= [BOOT] Specify the location of the initial ramdisk
931 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
932 Format: <irq>
934 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
935 on
936 Enable intel iommu driver.
937 off
938 Disable intel iommu driver.
939 igfx_off [Default Off]
940 By default, gfx is mapped as normal device. If a gfx
941 device has a dedicated DMAR unit, the DMAR unit is
942 bypassed by not enabling DMAR with this option. In
943 this case, gfx device will use physical address for
944 DMA.
945 forcedac [x86_64]
946 With this option iommu will not optimize to look
947 for io virtual address below 32 bit forcing dual
948 address cycle on pci bus for cards supporting greater
949 than 32 bit addressing. The default is to look
950 for translation below 32 bit and if not available
951 then look in the higher range.
952 strict [Default Off]
953 With this option on every unmap_single operation will
954 result in a hardware IOTLB flush operation as opposed
955 to batching them for performance.
957 inttest= [IA64]
959 iomem= Disable strict checking of access to MMIO memory
960 strict regions from userspace.
961 relaxed
963 iommu= [x86]
964 off
965 force
966 noforce
967 biomerge
968 panic
969 nopanic
970 merge
971 nomerge
972 forcesac
973 soft
975 io7= [HW] IO7 for Marvel based alpha systems
976 See comment before marvel_specify_io7 in
977 arch/alpha/kernel/core_marvel.c.
979 io_delay= [X86] I/O delay method
980 0x80
981 Standard port 0x80 based delay
982 0xed
983 Alternate port 0xed based delay (needed on some systems)
984 udelay
985 Simple two microseconds delay
986 none
987 No delay
989 ip= [IP_PNP]
990 See Documentation/filesystems/nfsroot.txt.
992 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
993 See comment before ip2_setup() in
994 drivers/char/ip2/ip2base.c.
996 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
997 See header of drivers/scsi/ips.c.
999 irqfixup [HW]
1000 When an interrupt is not handled search all handlers
1001 for it. Intended to get systems with badly broken
1002 firmware running.
1004 irqpoll [HW]
1005 When an interrupt is not handled search all handlers
1006 for it. Also check all handlers each timer
1007 interrupt. Intended to get systems with badly broken
1008 firmware running.
1010 isapnp= [ISAPNP]
1011 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1013 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1014 Format:
1015 <cpu number>,...,<cpu number>
1016 or
1017 <cpu number>-<cpu number>
1018 (must be a positive range in ascending order)
1019 or a mixture
1020 <cpu number>,...,<cpu number>-<cpu number>
1022 This option can be used to specify one or more CPUs
1023 to isolate from the general SMP balancing and scheduling
1024 algorithms. You can move a process onto or off an
1025 "isolated" CPU via the CPU affinity syscalls or cpuset.
1026 <cpu number> begins at 0 and the maximum value is
1027 "number of CPUs in system - 1".
1029 This option is the preferred way to isolate CPUs. The
1030 alternative -- manually setting the CPU mask of all
1031 tasks in the system -- can cause problems and
1032 suboptimal load balancer performance.
1034 iucv= [HW,NET]
1036 js= [HW,JOY] Analog joystick
1037 See Documentation/input/joystick.txt.
1039 keepinitrd [HW,ARM]
1041 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1042 specifies the amount of memory usable by the kernel
1043 for non-movable allocations. The requested amount is
1044 spread evenly throughout all nodes in the system. The
1045 remaining memory in each node is used for Movable
1046 pages. In the event, a node is too small to have both
1047 kernelcore and Movable pages, kernelcore pages will
1048 take priority and other nodes will have a larger number
1049 of kernelcore pages. The Movable zone is used for the
1050 allocation of pages that may be reclaimed or moved
1051 by the page migration subsystem. This means that
1052 HugeTLB pages may not be allocated from this zone.
1053 Note that allocations like PTEs-from-HighMem still
1054 use the HighMem zone if it exists, and the Normal
1055 zone if it does not.
1057 kmemtrace.enable= [KNL,KMEMTRACE] Format: { yes | no }
1058 Controls whether kmemtrace is enabled
1059 at boot-time.
1061 kmemtrace.subbufs=n [KNL,KMEMTRACE] Overrides the number of
1062 subbufs kmemtrace's relay channel has. Set this
1063 higher than default (KMEMTRACE_N_SUBBUFS in code) if
1064 you experience buffer overruns.
1066 kgdboc= [HW] kgdb over consoles.
1067 Requires a tty driver that supports console polling.
1068 (only serial suported for now)
1069 Format: <serial_device>[,baud]
1071 kmac= [MIPS] korina ethernet MAC address.
1072 Configure the RouterBoard 532 series on-chip
1073 Ethernet adapter MAC address.
1075 kstack=N [X86] Print N words from the kernel stack
1076 in oops dumps.
1078 l2cr= [PPC]
1080 l3cr= [PPC]
1082 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1083 disabled it.
1085 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1086 in C2 power state.
1088 libata.dma= [LIBATA] DMA control
1089 libata.dma=0 Disable all PATA and SATA DMA
1090 libata.dma=1 PATA and SATA Disk DMA only
1091 libata.dma=2 ATAPI (CDROM) DMA only
1092 libata.dma=4 Compact Flash DMA only
1093 Combinations also work, so libata.dma=3 enables DMA
1094 for disks and CDROMs, but not CFs.
1096 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1097 when set.
1098 Format: <int>
1100 libata.force= [LIBATA] Force configurations. The format is comma
1101 separated list of "[ID:]VAL" where ID is
1102 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1103 matching port, link or device. Basically, it matches
1104 the ATA ID string printed on console by libata. If
1105 the whole ID part is omitted, the last PORT and DEVICE
1106 values are used. If ID hasn't been specified yet, the
1107 configuration applies to all ports, links and devices.
1109 If only DEVICE is omitted, the parameter applies to
1110 the port and all links and devices behind it. DEVICE
1111 number of 0 either selects the first device or the
1112 first fan-out link behind PMP device. It does not
1113 select the host link. DEVICE number of 15 selects the
1114 host link and device attached to it.
1116 The VAL specifies the configuration to force. As long
1117 as there's no ambiguity shortcut notation is allowed.
1118 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1119 The following configurations can be forced.
1121 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1122 Any ID with matching PORT is used.
1124 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1126 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1127 udma[/][16,25,33,44,66,100,133] notation is also
1128 allowed.
1130 * [no]ncq: Turn on or off NCQ.
1132 * nohrst, nosrst, norst: suppress hard, soft
1133 and both resets.
1135 If there are multiple matching configurations changing
1136 the same attribute, the last one is used.
1138 lmb=debug [KNL] Enable lmb debug messages.
1140 load_ramdisk= [RAM] List of ramdisks to load from floppy
1141 See Documentation/blockdev/ramdisk.txt.
1143 lockd.nlm_grace_period=P [NFS] Assign grace period.
1144 Format: <integer>
1146 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1147 Format: <integer>
1149 lockd.nlm_timeout=T [NFS] Assign timeout value.
1150 Format: <integer>
1152 lockd.nlm_udpport=M [NFS] Assign UDP port.
1153 Format: <integer>
1155 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1156 Format: <irq>
1158 loglevel= All Kernel Messages with a loglevel smaller than the
1159 console loglevel will be printed to the console. It can
1160 also be changed with klogd or other programs. The
1161 loglevels are defined as follows:
1163 0 (KERN_EMERG) system is unusable
1164 1 (KERN_ALERT) action must be taken immediately
1165 2 (KERN_CRIT) critical conditions
1166 3 (KERN_ERR) error conditions
1167 4 (KERN_WARNING) warning conditions
1168 5 (KERN_NOTICE) normal but significant condition
1169 6 (KERN_INFO) informational
1170 7 (KERN_DEBUG) debug-level messages
1172 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1173 Format: { n | nk | nM }
1174 n must be a power of two. The default size
1175 is set in the kernel config file.
1177 logo.nologo [FB] Disables display of the built-in Linux logo.
1178 This may be used to provide more screen space for
1179 kernel log messages and is useful when debugging
1180 kernel boot problems.
1182 lp=0 [LP] Specify parallel ports to use, e.g,
1183 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1184 lp=reset first parallel port). 'lp=0' disables the
1185 lp=auto printer driver. 'lp=reset' (which can be
1186 specified in addition to the ports) causes
1187 attached printers to be reset. Using
1188 lp=port1,port2,... specifies the parallel ports
1189 to associate lp devices with, starting with
1190 lp0. A port specification may be 'none' to skip
1191 that lp device, or a parport name such as
1192 'parport0'. Specifying 'lp=auto' instead of a
1193 port specification list means that device IDs
1194 from each port should be examined, to see if
1195 an IEEE 1284-compliant printer is attached; if
1196 so, the driver will manage that printer.
1197 See also header of drivers/char/lp.c.
1199 lpj=n [KNL]
1200 Sets loops_per_jiffy to given constant, thus avoiding
1201 time-consuming boot-time autodetection (up to 250 ms per
1202 CPU). 0 enables autodetection (default). To determine
1203 the correct value for your kernel, boot with normal
1204 autodetection and see what value is printed. Note that
1205 on SMP systems the preset will be applied to all CPUs,
1206 which is likely to cause problems if your CPUs need
1207 significantly divergent settings. An incorrect value
1208 will cause delays in the kernel to be wrong, leading to
1209 unpredictable I/O errors and other breakage. Although
1210 unlikely, in the extreme case this might damage your
1211 hardware.
1213 ltpc= [NET]
1214 Format: <io>,<irq>,<dma>
1216 mac5380= [HW,SCSI] Format:
1217 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1219 machvec= [IA64] Force the use of a particular machine-vector
1220 (machvec) in a generic kernel.
1221 Example: machvec=hpzx1_swiotlb
1223 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1224 than or equal to this physical address is ignored.
1226 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1227 should make use of. maxcpus=n : n >= 0 limits the
1228 kernel to using 'n' processors. n=0 is a special case,
1229 it is equivalent to "nosmp", which also disables
1230 the IO APIC.
1232 max_loop= [LOOP] Maximum number of loopback devices that can
1233 be mounted
1234 Format: <1-256>
1236 max_luns= [SCSI] Maximum number of LUNs to probe.
1237 Should be between 1 and 2^32-1.
1239 max_report_luns=
1240 [SCSI] Maximum number of LUNs received.
1241 Should be between 1 and 16384.
1243 mcatest= [IA-64]
1245 mce [X86-32] Machine Check Exception
1247 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1249 md= [HW] RAID subsystems devices and level
1250 See Documentation/md.txt.
1252 mdacon= [MDA]
1253 Format: <first>,<last>
1254 Specifies range of consoles to be captured by the MDA.
1256 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1257 Amount of memory to be used when the kernel is not able
1258 to see the whole system memory or for test.
1259 [X86-32] Use together with memmap= to avoid physical
1260 address space collisions. Without memmap= PCI devices
1261 could be placed at addresses belonging to unused RAM.
1263 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1264 memory.
1266 memchunk=nn[KMG]
1267 [KNL,SH] Allow user to override the default size for
1268 per-device physically contiguous DMA buffers.
1270 memmap=exactmap [KNL,X86] Enable setting of an exact
1271 E820 memory map, as specified by the user.
1272 Such memmap=exactmap lines can be constructed based on
1273 BIOS output or other requirements. See the memmap=nn@ss
1274 option description.
1276 memmap=nn[KMG]@ss[KMG]
1277 [KNL] Force usage of a specific region of memory
1278 Region of memory to be used, from ss to ss+nn.
1280 memmap=nn[KMG]#ss[KMG]
1281 [KNL,ACPI] Mark specific memory as ACPI data.
1282 Region of memory to be used, from ss to ss+nn.
1284 memmap=nn[KMG]$ss[KMG]
1285 [KNL,ACPI] Mark specific memory as reserved.
1286 Region of memory to be used, from ss to ss+nn.
1287 Example: Exclude memory from 0x18690000-0x1869ffff
1288 memmap=64K$0x18690000
1289 or
1290 memmap=0x10000$0x18690000
1292 memory_corruption_check=0/1 [X86]
1293 Some BIOSes seem to corrupt the first 64k of
1294 memory when doing things like suspend/resume.
1295 Setting this option will scan the memory
1296 looking for corruption. Enabling this will
1297 both detect corruption and prevent the kernel
1298 from using the memory being corrupted.
1299 However, its intended as a diagnostic tool; if
1300 repeatable BIOS-originated corruption always
1301 affects the same memory, you can use memmap=
1302 to prevent the kernel from using that memory.
1304 memory_corruption_check_size=size [X86]
1305 By default it checks for corruption in the low
1306 64k, making this memory unavailable for normal
1307 use. Use this parameter to scan for
1308 corruption in more or less memory.
1310 memory_corruption_check_period=seconds [X86]
1311 By default it checks for corruption every 60
1312 seconds. Use this parameter to check at some
1313 other rate. 0 disables periodic checking.
1315 memtest= [KNL,X86] Enable memtest
1316 Format: <integer>
1317 default : 0 <disable>
1318 Specifies the number of memtest passes to be
1319 performed. Each pass selects another test
1320 pattern from a given set of patterns. Memtest
1321 fills the memory with this pattern, validates
1322 memory contents and reserves bad memory
1323 regions that are detected.
1325 meye.*= [HW] Set MotionEye Camera parameters
1326 See Documentation/video4linux/meye.txt.
1328 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1329 Multi-Function General Purpose Timers on AMD Geode
1330 platforms.
1332 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1333 the BIOS has incorrectly applied a workaround. TinyBIOS
1334 version 0.98 is known to be affected, 0.99 fixes the
1335 problem by letting the user disable the workaround.
1337 mga= [HW,DRM]
1339 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1340 physical address is ignored.
1342 mminit_loglevel=
1343 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1344 parameter allows control of the logging verbosity for
1345 the additional memory initialisation checks. A value
1346 of 0 disables mminit logging and a level of 4 will
1347 log everything. Information is printed at KERN_DEBUG
1348 so loglevel=8 may also need to be specified.
1350 mousedev.tap_time=
1351 [MOUSE] Maximum time between finger touching and
1352 leaving touchpad surface for touch to be considered
1353 a tap and be reported as a left button click (for
1354 touchpads working in absolute mode only).
1355 Format: <msecs>
1356 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1357 reporting absolute coordinates, such as tablets
1358 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1359 reporting absolute coordinates, such as tablets
1361 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1362 is similar to kernelcore except it specifies the
1363 amount of memory used for migratable allocations.
1364 If both kernelcore and movablecore is specified,
1365 then kernelcore will be at *least* the specified
1366 value but may be more. If movablecore on its own
1367 is specified, the administrator must be careful
1368 that the amount of memory usable for all allocations
1369 is not too small.
1371 mpu401= [HW,OSS]
1372 Format: <io>,<irq>
1374 MTD_Partition= [MTD]
1375 Format: <name>,<region-number>,<size>,<offset>
1377 MTD_Region= [MTD] Format:
1378 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1380 mtdparts= [MTD]
1381 See drivers/mtd/cmdlinepart.c.
1383 mtdset= [ARM]
1384 ARM/S3C2412 JIVE boot control
1386 See arch/arm/mach-s3c2412/mach-jive.c
1388 mtouchusb.raw_coordinates=
1389 [HW] Make the MicroTouch USB driver use raw coordinates
1390 ('y', default) or cooked coordinates ('n')
1392 mtrr_chunk_size=nn[KMG] [X86]
1393 used for mtrr cleanup. It is largest continous chunk
1394 that could hold holes aka. UC entries.
1396 mtrr_gran_size=nn[KMG] [X86]
1397 Used for mtrr cleanup. It is granularity of mtrr block.
1398 Default is 1.
1399 Large value could prevent small alignment from
1400 using up MTRRs.
1402 mtrr_spare_reg_nr=n [X86]
1403 Format: <integer>
1404 Range: 0,7 : spare reg number
1405 Default : 1
1406 Used for mtrr cleanup. It is spare mtrr entries number.
1407 Set to 2 or more if your graphical card needs more.
1409 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1411 NCR_D700= [HW,SCSI]
1412 See header of drivers/scsi/NCR_D700.c.
1414 ncr5380= [HW,SCSI]
1416 ncr53c400= [HW,SCSI]
1418 ncr53c400a= [HW,SCSI]
1420 ncr53c406a= [HW,SCSI]
1422 ncr53c8xx= [HW,SCSI]
1424 netdev= [NET] Network devices parameters
1425 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1426 Note that mem_start is often overloaded to mean
1427 something different and driver-specific.
1428 This usage is only documented in each driver source
1429 file if at all.
1431 nf_conntrack.acct=
1432 [NETFILTER] Enable connection tracking flow accounting
1433 0 to disable accounting
1434 1 to enable accounting
1435 Default value depends on CONFIG_NF_CT_ACCT that is
1436 going to be removed in 2.6.29.
1438 nfsaddrs= [NFS]
1439 See Documentation/filesystems/nfsroot.txt.
1441 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1442 See Documentation/filesystems/nfsroot.txt.
1444 nfs.callback_tcpport=
1445 [NFS] set the TCP port on which the NFSv4 callback
1446 channel should listen.
1448 nfs.idmap_cache_timeout=
1449 [NFS] set the maximum lifetime for idmapper cache
1450 entries.
1452 nfs.enable_ino64=
1453 [NFS] enable 64-bit inode numbers.
1454 If zero, the NFS client will fake up a 32-bit inode
1455 number for the readdir() and stat() syscalls instead
1456 of returning the full 64-bit number.
1457 The default is to return 64-bit inode numbers.
1459 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1460 when a NMI is triggered.
1461 Format: [state][,regs][,debounce][,die]
1463 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1464 Format: [panic,][num]
1465 Valid num: 0,1,2
1466 0 - turn nmi_watchdog off
1467 1 - use the IO-APIC timer for the NMI watchdog
1468 2 - use the local APIC for the NMI watchdog using
1469 a performance counter. Note: This will use one
1470 performance counter and the local APIC's performance
1471 vector.
1472 When panic is specified, panic when an NMI watchdog
1473 timeout occurs.
1474 This is useful when you use a panic=... timeout and
1475 need the box quickly up again.
1476 Instead of 1 and 2 it is possible to use the following
1477 symbolic names: lapic and ioapic
1478 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1480 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1481 emulation library even if a 387 maths coprocessor
1482 is present.
1484 no_console_suspend
1485 [HW] Never suspend the console
1486 Disable suspending of consoles during suspend and
1487 hibernate operations. Once disabled, debugging
1488 messages can reach various consoles while the rest
1489 of the system is being put to sleep (ie, while
1490 debugging driver suspend/resume hooks). This may
1491 not work reliably with all consoles, but is known
1492 to work with serial and VGA consoles.
1494 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1495 caches in the slab allocator. Saves per-node memory,
1496 but will impact performance.
1498 noalign [KNL,ARM]
1500 noapic [SMP,APIC] Tells the kernel to not make use of any
1501 IOAPICs that may be present in the system.
1503 nobats [PPC] Do not use BATs for mapping kernel lowmem
1504 on "Classic" PPC cores.
1506 nocache [ARM]
1508 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1510 nodelayacct [KNL] Disable per-task delay accounting
1512 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1514 nodsp [SH] Disable hardware DSP at boot time.
1516 noefi [X86] Disable EFI runtime services support.
1518 noexec [IA-64]
1520 noexec [X86]
1521 On X86-32 available only on PAE configured kernels.
1522 noexec=on: enable non-executable mappings (default)
1523 noexec=off: disable non-executable mappings
1525 noexec32 [X86-64]
1526 This affects only 32-bit executables.
1527 noexec32=on: enable non-executable mappings (default)
1528 read doesn't imply executable mappings
1529 noexec32=off: disable non-executable mappings
1530 read implies executable mappings
1532 nofpu [SH] Disable hardware FPU at boot time.
1534 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1535 register save and restore. The kernel will only save
1536 legacy floating-point registers on task switch.
1538 noxsave [BUGS=X86] Disables x86 extended register state save
1539 and restore using xsave. The kernel will fallback to
1540 enabling legacy floating-point and sse state.
1542 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1543 wfi(ARM) instruction doesn't work correctly and not to
1544 use it. This is also useful when using JTAG debugger.
1546 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1547 instruction doesn't work correctly and not to
1548 use it.
1550 no_file_caps Tells the kernel not to honor file capabilities. The
1551 only way then for a file to be executed with privilege
1552 is to be setuid root or executed by root.
1554 nohalt [IA-64] Tells the kernel not to use the power saving
1555 function PAL_HALT_LIGHT when idle. This increases
1556 power-consumption. On the positive side, it reduces
1557 interrupt wake-up latency, which may improve performance
1558 in certain environments such as networked servers or
1559 real-time systems.
1561 nohz= [KNL] Boottime enable/disable dynamic ticks
1562 Valid arguments: on, off
1563 Default: on
1565 noiotrap [SH] Disables trapped I/O port accesses.
1567 noirqdebug [X86-32] Disables the code which attempts to detect and
1568 disable unhandled interrupt sources.
1570 no_timer_check [X86,APIC] Disables the code which tests for
1571 broken timer IRQ sources.
1573 noisapnp [ISAPNP] Disables ISA PnP code.
1575 noinitrd [RAM] Tells the kernel not to load any configured
1576 initial RAM disk.
1578 nointroute [IA-64]
1580 nojitter [IA64] Disables jitter checking for ITC timers.
1582 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1584 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1586 noltlbs [PPC] Do not use large page/tlb entries for kernel
1587 lowmem mapping on PPC40x.
1589 nomca [IA-64] Disable machine check abort handling
1591 nomce [X86-32] Machine Check Exception
1593 nomfgpt [X86-32] Disable Multi-Function General Purpose
1594 Timer usage (for AMD Geode machines).
1596 norandmaps Don't use address space randomization. Equivalent to
1597 echo 0 > /proc/sys/kernel/randomize_va_space
1599 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1601 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1602 with UP alternatives
1604 noresidual [PPC] Don't use residual data on PReP machines.
1606 noresume [SWSUSP] Disables resume and restores original swap
1607 space.
1609 no-scroll [VGA] Disables scrollback.
1610 This is required for the Braillex ib80-piezo Braille
1611 reader made by F.H. Papenmeier (Germany).
1613 nosbagart [IA-64]
1615 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1617 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1618 and disable the IO APIC. legacy for "maxcpus=0".
1620 nosoftlockup [KNL] Disable the soft-lockup detector.
1622 noswapaccount [KNL] Disable accounting of swap in memory resource
1623 controller. (See Documentation/cgroups/memory.txt)
1625 nosync [HW,M68K] Disables sync negotiation for all devices.
1627 notsc [BUGS=X86-32] Disable Time Stamp Counter
1629 nousb [USB] Disable the USB subsystem
1631 nowb [ARM]
1633 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1635 nptcg= [IA64] Override max number of concurrent global TLB
1636 purges which is reported from either PAL_VM_SUMMARY or
1637 SAL PALO.
1639 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1641 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1642 one of ['zone', 'node', 'default'] can be specified
1643 This can be set from sysctl after boot.
1644 See Documentation/sysctl/vm.txt for details.
1646 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1647 See Documentation/debugging-via-ohci1394.txt for more
1648 info.
1650 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1651 Rather than timing out after 20 ms if an EC
1652 command is not properly ACKed, override the length
1653 of the timeout. We have interrupts disabled while
1654 waiting for the ACK, so if this is set too high
1655 interrupts *may* be lost!
1657 opl3= [HW,OSS]
1658 Format: <io>
1660 oprofile.timer= [HW]
1661 Use timer interrupt instead of performance counters
1663 osst= [HW,SCSI] SCSI Tape Driver
1664 Format: <buffer_size>,<write_threshold>
1665 See also Documentation/scsi/st.txt.
1667 panic= [KNL] Kernel behaviour on panic
1668 Format: <timeout>
1670 parkbd.port= [HW] Parallel port number the keyboard adapter is
1671 connected to, default is 0.
1672 Format: <parport#>
1673 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1674 0 for XT, 1 for AT (default is AT).
1675 Format: <mode>
1677 parport= [HW,PPT] Specify parallel ports. 0 disables.
1678 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1679 Use 'auto' to force the driver to use any
1680 IRQ/DMA settings detected (the default is to
1681 ignore detected IRQ/DMA settings because of
1682 possible conflicts). You can specify the base
1683 address, IRQ, and DMA settings; IRQ and DMA
1684 should be numbers, or 'auto' (for using detected
1685 settings on that particular port), or 'nofifo'
1686 (to avoid using a FIFO even if it is detected).
1687 Parallel ports are assigned in the order they
1688 are specified on the command line, starting
1689 with parport0.
1691 parport_init_mode= [HW,PPT]
1692 Configure VIA parallel port to operate in
1693 a specific mode. This is necessary on Pegasos
1694 computer where firmware has no options for setting
1695 up parallel port mode and sets it to spp.
1696 Currently this function knows 686a and 8231 chips.
1697 Format: [spp|ps2|epp|ecp|ecpepp]
1699 pas2= [HW,OSS] Format:
1700 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1702 pas16= [HW,SCSI]
1703 See header of drivers/scsi/pas16.c.
1705 pause_on_oops=
1706 Halt all CPUs after the first oops has been printed for
1707 the specified number of seconds. This is to be used if
1708 your oopses keep scrolling off the screen.
1710 pcbit= [HW,ISDN]
1712 pcd. [PARIDE]
1713 See header of drivers/block/paride/pcd.c.
1714 See also Documentation/blockdev/paride.txt.
1716 pci=option[,option...] [PCI] various PCI subsystem options:
1717 earlydump [X86] dump PCI config space before the kernel
1718 changes anything
1719 off [X86] don't probe for the PCI bus
1720 bios [X86-32] force use of PCI BIOS, don't access
1721 the hardware directly. Use this if your machine
1722 has a non-standard PCI host bridge.
1723 nobios [X86-32] disallow use of PCI BIOS, only direct
1724 hardware access methods are allowed. Use this
1725 if you experience crashes upon bootup and you
1726 suspect they are caused by the BIOS.
1727 conf1 [X86] Force use of PCI Configuration
1728 Mechanism 1.
1729 conf2 [X86] Force use of PCI Configuration
1730 Mechanism 2.
1731 noaer [PCIE] If the PCIEAER kernel config parameter is
1732 enabled, this kernel boot option can be used to
1733 disable the use of PCIE advanced error reporting.
1734 nodomains [PCI] Disable support for multiple PCI
1735 root domains (aka PCI segments, in ACPI-speak).
1736 nommconf [X86] Disable use of MMCONFIG for PCI
1737 Configuration
1738 check_enable_amd_mmconf [X86] check for and enable
1739 properly configured MMIO access to PCI
1740 config space on AMD family 10h CPU
1741 nomsi [MSI] If the PCI_MSI kernel config parameter is
1742 enabled, this kernel boot option can be used to
1743 disable the use of MSI interrupts system-wide.
1744 noioapicquirk [APIC] Disable all boot interrupt quirks.
1745 Safety option to keep boot IRQs enabled. This
1746 should never be necessary.
1747 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1748 primary IO-APIC for bridges that cannot disable
1749 boot IRQs. This fixes a source of spurious IRQs
1750 when the system masks IRQs.
1751 noioapicreroute [APIC] Disable workaround that uses the
1752 boot IRQ equivalent of an IRQ that connects to
1753 a chipset where boot IRQs cannot be disabled.
1754 The opposite of ioapicreroute.
1755 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1756 routing table. These calls are known to be buggy
1757 on several machines and they hang the machine
1758 when used, but on other computers it's the only
1759 way to get the interrupt routing table. Try
1760 this option if the kernel is unable to allocate
1761 IRQs or discover secondary PCI buses on your
1762 motherboard.
1763 rom [X86] Assign address space to expansion ROMs.
1764 Use with caution as certain devices share
1765 address decoders between ROMs and other
1766 resources.
1767 norom [X86] Do not assign address space to
1768 expansion ROMs that do not already have
1769 BIOS assigned address ranges.
1770 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1771 assigned automatically to PCI devices. You can
1772 make the kernel exclude IRQs of your ISA cards
1773 this way.
1774 pirqaddr=0xAAAAA [X86] Specify the physical address
1775 of the PIRQ table (normally generated
1776 by the BIOS) if it is outside the
1777 F0000h-100000h range.
1778 lastbus=N [X86] Scan all buses thru bus #N. Can be
1779 useful if the kernel is unable to find your
1780 secondary buses and you want to tell it
1781 explicitly which ones they are.
1782 assign-busses [X86] Always assign all PCI bus
1783 numbers ourselves, overriding
1784 whatever the firmware may have done.
1785 usepirqmask [X86] Honor the possible IRQ mask stored
1786 in the BIOS $PIR table. This is needed on
1787 some systems with broken BIOSes, notably
1788 some HP Pavilion N5400 and Omnibook XE3
1789 notebooks. This will have no effect if ACPI
1790 IRQ routing is enabled.
1791 noacpi [X86] Do not use ACPI for IRQ routing
1792 or for PCI scanning.
1793 nocrs [X86] Don't use _CRS for PCI resource
1794 allocation.
1795 routeirq Do IRQ routing for all PCI devices.
1796 This is normally done in pci_enable_device(),
1797 so this option is a temporary workaround
1798 for broken drivers that don't call it.
1799 skip_isa_align [X86] do not align io start addr, so can
1800 handle more pci cards
1801 firmware [ARM] Do not re-enumerate the bus but instead
1802 just use the configuration from the
1803 bootloader. This is currently used on
1804 IXP2000 systems where the bus has to be
1805 configured a certain way for adjunct CPUs.
1806 noearly [X86] Don't do any early type 1 scanning.
1807 This might help on some broken boards which
1808 machine check when some devices' config space
1809 is read. But various workarounds are disabled
1810 and some IOMMU drivers will not work.
1811 bfsort Sort PCI devices into breadth-first order.
1812 This sorting is done to get a device
1813 order compatible with older (<= 2.4) kernels.
1814 nobfsort Don't sort PCI devices into breadth-first order.
1815 cbiosize=nn[KMG] The fixed amount of bus space which is
1816 reserved for the CardBus bridge's IO window.
1817 The default value is 256 bytes.
1818 cbmemsize=nn[KMG] The fixed amount of bus space which is
1819 reserved for the CardBus bridge's memory
1820 window. The default value is 64 megabytes.
1821 resource_alignment=
1822 Format:
1823 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1824 Specifies alignment and device to reassign
1825 aligned memory resources.
1826 If <order of align> is not specified,
1827 PAGE_SIZE is used as alignment.
1828 PCI-PCI bridge can be specified, if resource
1829 windows need to be expanded.
1830 ecrc= Enable/disable PCIe ECRC (transaction layer
1831 end-to-end CRC checking).
1832 bios: Use BIOS/firmware settings. This is the
1833 the default.
1834 off: Turn ECRC off
1835 on: Turn ECRC on.
1837 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1838 Management.
1839 off Disable ASPM.
1840 force Enable ASPM even on devices that claim not to support it.
1841 WARNING: Forcing ASPM on may cause system lockups.
1843 pcmv= [HW,PCMCIA] BadgePAD 4
1845 pd. [PARIDE]
1846 See Documentation/blockdev/paride.txt.
1848 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1849 boot time.
1850 Format: { 0 | 1 }
1851 See arch/parisc/kernel/pdc_chassis.c
1853 pf. [PARIDE]
1854 See Documentation/blockdev/paride.txt.
1856 pg. [PARIDE]
1857 See Documentation/blockdev/paride.txt.
1859 pirq= [SMP,APIC] Manual mp-table setup
1860 See Documentation/x86/i386/IO-APIC.txt.
1862 plip= [PPT,NET] Parallel port network link
1863 Format: { parport<nr> | timid | 0 }
1864 See also Documentation/parport.txt.
1866 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1867 Override pmtimer IOPort with a hex value.
1868 e.g. pmtmr=0x508
1870 pnp.debug [PNP]
1871 Enable PNP debug messages. This depends on the
1872 CONFIG_PNP_DEBUG_MESSAGES option.
1874 pnpacpi= [ACPI]
1875 { off }
1877 pnpbios= [ISAPNP]
1878 { on | off | curr | res | no-curr | no-res }
1880 pnp_reserve_irq=
1881 [ISAPNP] Exclude IRQs for the autoconfiguration
1883 pnp_reserve_dma=
1884 [ISAPNP] Exclude DMAs for the autoconfiguration
1886 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1887 Ranges are in pairs (I/O port base and size).
1889 pnp_reserve_mem=
1890 [ISAPNP] Exclude memory regions for the
1891 autoconfiguration.
1892 Ranges are in pairs (memory base and size).
1894 ports= [IP_VS_FTP] IPVS ftp helper module
1895 Default is 21.
1896 Up to 8 (IP_VS_APP_MAX_PORTS) ports
1897 may be specified.
1898 Format: <port>,<port>....
1900 print-fatal-signals=
1901 [KNL] debug: print fatal signals
1902 print-fatal-signals=1: print segfault info to
1903 the kernel console.
1904 default: off.
1906 printk.time= Show timing data prefixed to each printk message line
1907 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1909 processor.max_cstate= [HW,ACPI]
1910 Limit processor to maximum C-state
1911 max_cstate=9 overrides any DMI blacklist limit.
1913 processor.nocst [HW,ACPI]
1914 Ignore the _CST method to determine C-states,
1915 instead using the legacy FADT method
1917 profile= [KNL] Enable kernel profiling via /proc/profile
1918 Format: [schedule,]<number>
1919 Param: "schedule" - profile schedule points.
1920 Param: <number> - step/bucket size as a power of 2 for
1921 statistical time based profiling.
1922 Param: "sleep" - profile D-state sleeping (millisecs).
1923 Requires CONFIG_SCHEDSTATS
1924 Param: "kvm" - profile VM exits.
1926 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1927 before loading.
1928 See Documentation/blockdev/ramdisk.txt.
1930 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1931 probe for; one of (bare|imps|exps|lifebook|any).
1932 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1933 per second.
1934 psmouse.resetafter= [HW,MOUSE]
1935 Try to reset the device after so many bad packets
1936 (0 = never).
1937 psmouse.resolution=
1938 [HW,MOUSE] Set desired mouse resolution, in dpi.
1939 psmouse.smartscroll=
1940 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1941 0 = disabled, 1 = enabled (default).
1943 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1944 Format:
1945 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1947 pt. [PARIDE]
1948 See Documentation/blockdev/paride.txt.
1950 pty.legacy_count=
1951 [KNL] Number of legacy pty's. Overwrites compiled-in
1952 default number.
1954 quiet [KNL] Disable most log messages
1956 r128= [HW,DRM]
1958 raid= [HW,RAID]
1959 See Documentation/md.txt.
1961 ramdisk_blocksize= [RAM]
1962 See Documentation/blockdev/ramdisk.txt.
1964 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1965 See Documentation/blockdev/ramdisk.txt.
1967 rcupdate.blimit= [KNL,BOOT]
1968 Set maximum number of finished RCU callbacks to process
1969 in one batch.
1971 rcupdate.qhimark= [KNL,BOOT]
1972 Set threshold of queued
1973 RCU callbacks over which batch limiting is disabled.
1975 rcupdate.qlowmark= [KNL,BOOT]
1976 Set threshold of queued RCU callbacks below which
1977 batch limiting is re-enabled.
1979 rdinit= [KNL]
1980 Format: <full_path>
1981 Run specified binary instead of /init from the ramdisk,
1982 used for early userspace startup. See initrd.
1984 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1985 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1986 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1988 relax_domain_level=
1989 [KNL, SMP] Set scheduler's default relax_domain_level.
1990 See Documentation/cgroups/cpusets.txt.
1992 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1994 reservetop= [X86-32]
1995 Format: nn[KMG]
1996 Reserves a hole at the top of the kernel virtual
1997 address space.
1999 reset_devices [KNL] Force drivers to reset the underlying device
2000 during initialization.
2002 resume= [SWSUSP]
2003 Specify the partition device for software suspend
2005 resume_offset= [SWSUSP]
2006 Specify the offset from the beginning of the partition
2007 given by "resume=" at which the swap header is located,
2008 in <PAGE_SIZE> units (needed only for swap files).
2009 See Documentation/power/swsusp-and-swap-files.txt
2011 retain_initrd [RAM] Keep initrd memory after extraction
2013 rhash_entries= [KNL,NET]
2014 Set number of hash buckets for route cache
2016 riscom8= [HW,SERIAL]
2017 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2019 ro [KNL] Mount root device read-only on boot
2021 root= [KNL] Root filesystem
2023 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2024 mount the root filesystem
2026 rootflags= [KNL] Set root filesystem mount option string
2028 rootfstype= [KNL] Set root filesystem type
2030 rootwait [KNL] Wait (indefinitely) for root device to show up.
2031 Useful for devices that are detected asynchronously
2032 (e.g. USB and MMC devices).
2034 root_plug.vendor_id=
2035 [ROOTPLUG] Override the default vendor ID
2037 root_plug.product_id=
2038 [ROOTPLUG] Override the default product ID
2040 root_plug.debug=
2041 [ROOTPLUG] Enable debugging output
2043 rw [KNL] Mount root device read-write on boot
2045 S [KNL] Run init in single mode
2047 sa1100ir [NET]
2048 See drivers/net/irda/sa1100_ir.c.
2050 sbni= [NET] Granch SBNI12 leased line adapter
2052 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2053 Format: <io>[,<timeout>[,<isapnp>]]
2055 scsi_debug_*= [SCSI]
2056 See drivers/scsi/scsi_debug.c.
2058 scsi_default_dev_flags=
2059 [SCSI] SCSI default device flags
2060 Format: <integer>
2062 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2063 Format: <vendor>:<model>:<flags>
2064 (flags are integer value)
2066 scsi_logging_level= [SCSI] a bit mask of logging levels
2067 See drivers/scsi/scsi_logging.h for bits. Also
2068 settable via sysctl at dev.scsi.logging_level
2069 (/proc/sys/dev/scsi/logging_level).
2070 There is also a nice 'scsi_logging_level' script in the
2071 S390-tools package, available for download at
2072 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2074 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2075 discovered. async scans them in kernel threads,
2076 allowing boot to proceed. none ignores them, expecting
2077 user space to do the scan.
2079 security= [SECURITY] Choose a security module to enable at boot.
2080 If this boot parameter is not specified, only the first
2081 security module asking for security registration will be
2082 loaded. An invalid security module name will be treated
2083 as if no module has been chosen.
2085 selinux= [SELINUX] Disable or enable SELinux at boot time.
2086 Format: { "0" | "1" }
2087 See security/selinux/Kconfig help text.
2088 0 -- disable.
2089 1 -- enable.
2090 Default value is set via kernel config option.
2091 If enabled at boot time, /selinux/disable can be used
2092 later to disable prior to initial policy load.
2094 serialnumber [BUGS=X86-32]
2096 shapers= [NET]
2097 Maximal number of shapers.
2099 show_msr= [x86] show boot-time MSR settings
2100 Format: { <integer> }
2101 Show boot-time (BIOS-initialized) MSR settings.
2102 The parameter means the number of CPUs to show,
2103 for example 1 means boot CPU only.
2105 sim710= [SCSI,HW]
2106 See header of drivers/scsi/sim710.c.
2108 simeth= [IA-64]
2109 simscsi=
2111 slram= [HW,MTD]
2113 slub_debug[=options[,slabs]] [MM, SLUB]
2114 Enabling slub_debug allows one to determine the
2115 culprit if slab objects become corrupted. Enabling
2116 slub_debug can create guard zones around objects and
2117 may poison objects when not in use. Also tracks the
2118 last alloc / free. For more information see
2119 Documentation/vm/slub.txt.
2121 slub_max_order= [MM, SLUB]
2122 Determines the maximum allowed order for slabs.
2123 A high setting may cause OOMs due to memory
2124 fragmentation. For more information see
2125 Documentation/vm/slub.txt.
2127 slub_min_objects= [MM, SLUB]
2128 The minimum number of objects per slab. SLUB will
2129 increase the slab order up to slub_max_order to
2130 generate a sufficiently large slab able to contain
2131 the number of objects indicated. The higher the number
2132 of objects the smaller the overhead of tracking slabs
2133 and the less frequently locks need to be acquired.
2134 For more information see Documentation/vm/slub.txt.
2136 slub_min_order= [MM, SLUB]
2137 Determines the mininum page order for slabs. Must be
2138 lower than slub_max_order.
2139 For more information see Documentation/vm/slub.txt.
2141 slub_nomerge [MM, SLUB]
2142 Disable merging of slabs with similar size. May be
2143 necessary if there is some reason to distinguish
2144 allocs to different slabs. Debug options disable
2145 merging on their own.
2146 For more information see Documentation/vm/slub.txt.
2148 smart2= [HW]
2149 Format: <io1>[,<io2>[,...,<io8>]]
2151 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2152 attempt to substitute SMP alternatives once at boot.
2154 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2155 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2156 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2157 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2158 smsc-ircc2.ircc_irq= [HW] IRQ line
2159 smsc-ircc2.ircc_dma= [HW] DMA channel
2160 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2161 0: Toshiba Satellite 1800 (GP data pin select)
2162 1: Fast pin select (default)
2163 2: ATC IRMode
2165 snd-ad1816a= [HW,ALSA]
2167 snd-ad1848= [HW,ALSA]
2169 snd-ali5451= [HW,ALSA]
2171 snd-als100= [HW,ALSA]
2173 snd-als4000= [HW,ALSA]
2175 snd-azt2320= [HW,ALSA]
2177 snd-cmi8330= [HW,ALSA]
2179 snd-cmipci= [HW,ALSA]
2181 snd-cs4231= [HW,ALSA]
2183 snd-cs4232= [HW,ALSA]
2185 snd-cs4236= [HW,ALSA]
2187 snd-cs4281= [HW,ALSA]
2189 snd-cs46xx= [HW,ALSA]
2191 snd-dt019x= [HW,ALSA]
2193 snd-dummy= [HW,ALSA]
2195 snd-emu10k1= [HW,ALSA]
2197 snd-ens1370= [HW,ALSA]
2199 snd-ens1371= [HW,ALSA]
2201 snd-es968= [HW,ALSA]
2203 snd-es1688= [HW,ALSA]
2205 snd-es18xx= [HW,ALSA]
2207 snd-es1938= [HW,ALSA]
2209 snd-es1968= [HW,ALSA]
2211 snd-fm801= [HW,ALSA]
2213 snd-gusclassic= [HW,ALSA]
2215 snd-gusextreme= [HW,ALSA]
2217 snd-gusmax= [HW,ALSA]
2219 snd-hdsp= [HW,ALSA]
2221 snd-ice1712= [HW,ALSA]
2223 snd-intel8x0= [HW,ALSA]
2225 snd-interwave= [HW,ALSA]
2227 snd-interwave-stb=
2228 [HW,ALSA]
2230 snd-korg1212= [HW,ALSA]
2232 snd-maestro3= [HW,ALSA]
2234 snd-mpu401= [HW,ALSA]
2236 snd-mtpav= [HW,ALSA]
2238 snd-nm256= [HW,ALSA]
2240 snd-opl3sa2= [HW,ALSA]
2242 snd-opti92x-ad1848=
2243 [HW,ALSA]
2245 snd-opti92x-cs4231=
2246 [HW,ALSA]
2248 snd-opti93x= [HW,ALSA]
2250 snd-pmac= [HW,ALSA]
2252 snd-rme32= [HW,ALSA]
2254 snd-rme96= [HW,ALSA]
2256 snd-rme9652= [HW,ALSA]
2258 snd-sb8= [HW,ALSA]
2260 snd-sb16= [HW,ALSA]
2262 snd-sbawe= [HW,ALSA]
2264 snd-serial= [HW,ALSA]
2266 snd-sgalaxy= [HW,ALSA]
2268 snd-sonicvibes= [HW,ALSA]
2270 snd-sun-amd7930=
2271 [HW,ALSA]
2273 snd-sun-cs4231= [HW,ALSA]
2275 snd-trident= [HW,ALSA]
2277 snd-usb-audio= [HW,ALSA,USB]
2279 snd-via82xx= [HW,ALSA]
2281 snd-virmidi= [HW,ALSA]
2283 snd-wavefront= [HW,ALSA]
2285 snd-ymfpci= [HW,ALSA]
2287 softlockup_panic=
2288 [KNL] Should the soft-lockup detector generate panics.
2290 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2291 See Documentation/sonypi.txt
2293 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2294 See Documentation/serial/specialix.txt.
2296 spia_io_base= [HW,MTD]
2297 spia_fio_base=
2298 spia_pedr=
2299 spia_peddr=
2301 sscape= [HW,OSS]
2302 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2304 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2305 See Documentation/scsi/st.txt.
2307 stacktrace [FTRACE]
2308 Enabled the stack tracer on boot up.
2310 sti= [PARISC,HW]
2311 Format: <num>
2312 Set the STI (builtin display/keyboard on the HP-PARISC
2313 machines) console (graphic card) which should be used
2314 as the initial boot-console.
2315 See also comment in drivers/video/console/sticore.c.
2317 sti_font= [HW]
2318 See comment in drivers/video/console/sticore.c.
2320 stifb= [HW]
2321 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2323 sunrpc.pool_mode=
2324 [NFS]
2325 Control how the NFS server code allocates CPUs to
2326 service thread pools. Depending on how many NICs
2327 you have and where their interrupts are bound, this
2328 option will affect which CPUs will do NFS serving.
2329 Note: this parameter cannot be changed while the
2330 NFS server is running.
2332 auto the server chooses an appropriate mode
2333 automatically using heuristics
2334 global a single global pool contains all CPUs
2335 percpu one pool for each CPU
2336 pernode one pool for each NUMA node (equivalent
2337 to global on non-NUMA machines)
2339 swiotlb= [IA-64] Number of I/O TLB slabs
2341 switches= [HW,M68k]
2343 sym53c416= [HW,SCSI]
2344 See header of drivers/scsi/sym53c416.c.
2346 sysrq_always_enabled
2347 [KNL]
2348 Ignore sysrq setting - this boot parameter will
2349 neutralize any effect of /proc/sys/kernel/sysrq.
2350 Useful for debugging.
2352 t128= [HW,SCSI]
2353 See header of drivers/scsi/t128.c.
2355 tdfx= [HW,DRM]
2357 test_suspend= [SUSPEND]
2358 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2359 standby suspend) as the system sleep state to briefly
2360 enter during system startup. The system is woken from
2361 this state using a wakeup-capable RTC alarm.
2363 thash_entries= [KNL,NET]
2364 Set number of hash buckets for TCP connection
2366 thermal.act= [HW,ACPI]
2367 -1: disable all active trip points in all thermal zones
2368 <degrees C>: override all lowest active trip points
2370 thermal.crt= [HW,ACPI]
2371 -1: disable all critical trip points in all thermal zones
2372 <degrees C>: override all critical trip points
2374 thermal.nocrt= [HW,ACPI]
2375 Set to disable actions on ACPI thermal zone
2376 critical and hot trip points.
2378 thermal.off= [HW,ACPI]
2379 1: disable ACPI thermal control
2381 thermal.psv= [HW,ACPI]
2382 -1: disable all passive trip points
2383 <degrees C>: override all passive trip points to this
2384 value
2386 thermal.tzp= [HW,ACPI]
2387 Specify global default ACPI thermal zone polling rate
2388 <deci-seconds>: poll all this frequency
2389 0: no polling (default)
2391 tmscsim= [HW,SCSI]
2392 See comment before function dc390_setup() in
2393 drivers/scsi/tmscsim.c.
2395 topology= [S390]
2396 Format: {off | on}
2397 Specify if the kernel should make use of the cpu
2398 topology informations if the hardware supports these.
2399 The scheduler will make use of these informations and
2400 e.g. base its process migration decisions on it.
2401 Default is off.
2403 tp720= [HW,PS2]
2405 trace_buf_size=nn[KMG] [ftrace] will set tracing buffer size.
2407 trix= [HW,OSS] MediaTrix AudioTrix Pro
2408 Format:
2409 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2411 tsc= Disable clocksource-must-verify flag for TSC.
2412 Format: <string>
2413 [x86] reliable: mark tsc clocksource as reliable, this
2414 disables clocksource verification at runtime.
2415 Used to enable high-resolution timer mode on older
2416 hardware, and in virtualized environment.
2418 turbografx.map[2|3]= [HW,JOY]
2419 TurboGraFX parallel port interface
2420 Format:
2421 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2422 See also Documentation/input/joystick-parport.txt
2424 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2425 See header of drivers/scsi/u14-34f.c.
2427 uart401= [HW,OSS]
2428 Format: <io>,<irq>
2430 uart6850= [HW,OSS]
2431 Format: <io>,<irq>
2433 uhci-hcd.ignore_oc=
2434 [USB] Ignore overcurrent events (default N).
2435 Some badly-designed motherboards generate lots of
2436 bogus events, for ports that aren't wired to
2437 anything. Set this parameter to avoid log spamming.
2438 Note that genuine overcurrent events won't be
2439 reported either.
2441 unknown_nmi_panic
2442 [X86]
2443 Set unknown_nmi_panic=1 early on boot.
2445 usbcore.autosuspend=
2446 [USB] The autosuspend time delay (in seconds) used
2447 for newly-detected USB devices (default 2). This
2448 is the time required before an idle device will be
2449 autosuspended. Devices for which the delay is set
2450 to a negative value won't be autosuspended at all.
2452 usbcore.usbfs_snoop=
2453 [USB] Set to log all usbfs traffic (default 0 = off).
2455 usbcore.blinkenlights=
2456 [USB] Set to cycle leds on hubs (default 0 = off).
2458 usbcore.old_scheme_first=
2459 [USB] Start with the old device initialization
2460 scheme (default 0 = off).
2462 usbcore.use_both_schemes=
2463 [USB] Try the other device initialization scheme
2464 if the first one fails (default 1 = enabled).
2466 usbcore.initial_descriptor_timeout=
2467 [USB] Specifies timeout for the initial 64-byte
2468 USB_REQ_GET_DESCRIPTOR request in milliseconds
2469 (default 5000 = 5.0 seconds).
2471 usbhid.mousepoll=
2472 [USBHID] The interval which mice are to be polled at.
2474 usb-storage.delay_use=
2475 [UMS] The delay in seconds before a new device is
2476 scanned for Logical Units (default 5).
2478 usb-storage.quirks=
2479 [UMS] A list of quirks entries to supplement or
2480 override the built-in unusual_devs list. List
2481 entries are separated by commas. Each entry has
2482 the form VID:PID:Flags where VID and PID are Vendor
2483 and Product ID values (4-digit hex numbers) and
2484 Flags is a set of characters, each corresponding
2485 to a common usb-storage quirk flag as follows:
2486 a = SANE_SENSE (collect more than 18 bytes
2487 of sense data);
2488 c = FIX_CAPACITY (decrease the reported
2489 device capacity by one sector);
2490 h = CAPACITY_HEURISTICS (decrease the
2491 reported device capacity by one
2492 sector if the number is odd);
2493 i = IGNORE_DEVICE (don't bind to this
2494 device);
2495 l = NOT_LOCKABLE (don't try to lock and
2496 unlock ejectable media);
2497 m = MAX_SECTORS_64 (don't transfer more
2498 than 64 sectors = 32 KB at a time);
2499 o = CAPACITY_OK (accept the capacity
2500 reported by the device);
2501 r = IGNORE_RESIDUE (the device reports
2502 bogus residue values);
2503 s = SINGLE_LUN (the device has only one
2504 Logical Unit);
2505 w = NO_WP_DETECT (don't test whether the
2506 medium is write-protected).
2507 Example: quirks=0419:aaf5:rl,0421:0433:rc
2509 vdso= [X86,SH]
2510 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2511 vdso=1: enable VDSO (default)
2512 vdso=0: disable VDSO mapping
2514 vdso32= [X86]
2515 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2516 vdso32=1: enable 32-bit VDSO (default)
2517 vdso32=0: disable 32-bit VDSO mapping
2519 vector= [IA-64,SMP]
2520 vector=percpu: enable percpu vector domain
2522 video= [FB] Frame buffer configuration
2523 See Documentation/fb/modedb.txt.
2525 vga= [BOOT,X86-32] Select a particular video mode
2526 See Documentation/x86/boot.txt and
2527 Documentation/svga.txt.
2528 Use vga=ask for menu.
2529 This is actually a boot loader parameter; the value is
2530 passed to the kernel using a special protocol.
2532 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2533 size of <nn>. This can be used to increase the
2534 minimum size (128MB on x86). It can also be used to
2535 decrease the size and leave more room for directly
2536 mapped kernel RAM.
2538 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2539 Format: <command>
2541 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2542 Format: <command>
2544 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2545 Format: <command>
2547 vt.default_blu= [VT]
2548 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2549 Change the default blue palette of the console.
2550 This is a 16-member array composed of values
2551 ranging from 0-255.
2553 vt.default_grn= [VT]
2554 Format: <green0>,<green1>,<green2>,...,<green15>
2555 Change the default green palette of the console.
2556 This is a 16-member array composed of values
2557 ranging from 0-255.
2559 vt.default_red= [VT]
2560 Format: <red0>,<red1>,<red2>,...,<red15>
2561 Change the default red palette of the console.
2562 This is a 16-member array composed of values
2563 ranging from 0-255.
2565 vt.default_utf8=
2566 [VT]
2567 Format=<0|1>
2568 Set system-wide default UTF-8 mode for all tty's.
2569 Default is 1, i.e. UTF-8 mode is enabled for all
2570 newly opened terminals.
2572 waveartist= [HW,OSS]
2573 Format: <io>,<irq>,<dma>,<dma2>
2575 wd33c93= [HW,SCSI]
2576 See header of drivers/scsi/wd33c93.c.
2578 wd7000= [HW,SCSI]
2579 See header of drivers/scsi/wd7000.c.
2581 wdt= [WDT] Watchdog
2582 See Documentation/watchdog/wdt.txt.
2584 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2585 default x2apic cluster mode on platforms
2586 supporting x2apic.
2588 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2589 xd_geo= See header of drivers/block/xd.c.
2591 xirc2ps_cs= [NET,PCMCIA]
2592 Format:
2593 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2595 ______________________________________________________________________
2597 TODO:
2599 Add documentation for ALSA options.
2600 Add more DRM drivers.