| blob | 4c12a290bee52a00186e4a4e4c4d726996320d8e |
1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 GCOV GCOV profiling is enabled.
52 HW Appropriate hardware is enabled.
53 IA-64 IA-64 architecture is enabled.
54 IMA Integrity measurement architecture is enabled.
55 IOSCHED More than one I/O scheduler is enabled.
56 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
57 ISAPNP ISA PnP code is enabled.
58 ISDN Appropriate ISDN support is enabled.
59 JOY Appropriate joystick support is enabled.
60 KVM Kernel Virtual Machine support is enabled.
61 LIBATA Libata driver is enabled
62 LP Printer support is enabled.
63 LOOP Loopback device support is enabled.
64 M68k M68k architecture is enabled.
65 These options have more detailed description inside of
66 Documentation/m68k/kernel-options.txt.
67 MCA MCA bus support is enabled.
68 MDA MDA console support is enabled.
69 MOUSE Appropriate mouse support is enabled.
70 MSI Message Signaled Interrupts (PCI).
71 MTD MTD (Memory Technology Device) support is enabled.
72 NET Appropriate network support is enabled.
73 NUMA NUMA support is enabled.
74 GENERIC_TIME The generic timeofday code is enabled.
75 NFS Appropriate NFS support is enabled.
76 OSS OSS sound support is enabled.
77 PV_OPS A paravirtualized kernel is enabled.
78 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
79 PARISC The PA-RISC architecture is enabled.
80 PCI PCI bus support is enabled.
81 PCIE PCI Express support is enabled.
82 PCMCIA The PCMCIA subsystem is enabled.
83 PNP Plug & Play support is enabled.
84 PPC PowerPC architecture is enabled.
85 PPT Parallel port support is enabled.
86 PS2 Appropriate PS/2 support is enabled.
87 RAM RAM disk support is enabled.
88 ROOTPLUG The example Root Plug LSM is enabled.
89 S390 S390 architecture is enabled.
90 SCSI Appropriate SCSI support is enabled.
91 A lot of drivers has their options described inside of
92 Documentation/scsi/.
93 SECURITY Different security models are enabled.
94 SELINUX SELinux support is enabled.
95 SERIAL Serial support is enabled.
96 SH SuperH architecture is enabled.
97 SMP The kernel is an SMP kernel.
98 SPARC Sparc architecture is enabled.
99 SWSUSP Software suspend (hibernation) is enabled.
100 SUSPEND System suspend states are enabled.
101 FTRACE Function tracing enabled.
102 TS Appropriate touchscreen support is enabled.
103 UMS USB Mass Storage support is enabled.
104 USB USB support is enabled.
105 USBHID USB Human Interface Device support is enabled.
106 V4L Video For Linux support is enabled.
107 VGA The VGA console has been enabled.
108 VT Virtual terminal support is enabled.
109 WDT Watchdog support is enabled.
110 XT IBM PC/XT MFM hard disk support is enabled.
111 X86-32 X86-32, aka i386 architecture is enabled.
112 X86-64 X86-64 architecture is enabled.
113 More X86-64 boot options can be found in
114 Documentation/x86/x86_64/boot-options.txt .
115 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
117 In addition, the following text indicates that the option:
119 BUGS= Relates to possible processor bugs on the said processor.
120 KNL Is a kernel start-up parameter.
121 BOOT Is a boot loader parameter.
123 Parameters denoted with BOOT are actually interpreted by the boot
124 loader, and have no meaning to the kernel directly.
125 Do not modify the syntax of boot loader parameters without extreme
126 need or coordination with <Documentation/x86/boot.txt>.
128 There are also arch-specific kernel-parameters not documented here.
129 See for example <Documentation/x86/x86_64/boot-options.txt>.
131 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
132 a trailing = on the name of any parameter states that that parameter will
133 be entered as an environment variable, whereas its absence indicates that
134 it will appear as a kernel argument readable via /proc/cmdline by programs
135 running once the system is up.
137 The number of kernel parameters is not limited, but the length of the
138 complete command line (parameters including spaces etc.) is limited to
139 a fixed number of characters. This limit depends on the architecture
140 and is between 256 and 4096 characters. It is defined in the file
141 ./include/asm/setup.h as COMMAND_LINE_SIZE.
144 acpi= [HW,ACPI,X86]
145 Advanced Configuration and Power Interface
146 Format: { force | off | ht | strict | noirq | rsdt }
147 force -- enable ACPI if default was off
148 off -- disable ACPI if default was on
149 noirq -- do not use ACPI for IRQ routing
150 ht -- run only enough ACPI to enable Hyper Threading
151 strict -- Be less tolerant of platforms that are not
152 strictly ACPI specification compliant.
153 rsdt -- prefer RSDT over (default) XSDT
155 See also Documentation/power/pm.txt, pci=noacpi
157 acpi_apic_instance= [ACPI, IOAPIC]
158 Format: <int>
159 2: use 2nd APIC table, if available
160 1,0: use 1st APIC table
161 default: 0
163 acpi_backlight= [HW,ACPI]
164 acpi_backlight=vendor
165 acpi_backlight=video
166 If set to vendor, prefer vendor specific driver
167 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
168 of the ACPI video.ko driver.
170 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
171 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
172 Format: <int>
173 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
174 debug output. Bits in debug_layer correspond to a
175 _COMPONENT in an ACPI source file, e.g.,
176 #define _COMPONENT ACPI_PCI_COMPONENT
177 Bits in debug_level correspond to a level in
178 ACPI_DEBUG_PRINT statements, e.g.,
179 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
180 The debug_level mask defaults to "info". See
181 Documentation/acpi/debug.txt for more information about
182 debug layers and levels.
184 Enable processor driver info messages:
185 acpi.debug_layer=0x20000000
186 Enable PCI/PCI interrupt routing info messages:
187 acpi.debug_layer=0x400000
188 Enable AML "Debug" output, i.e., stores to the Debug
189 object while interpreting AML:
190 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
191 Enable all messages related to ACPI hardware:
192 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
194 Some values produce so much output that the system is
195 unusable. The "log_buf_len" parameter may be useful
196 if you need to capture more output.
198 acpi_display_output= [HW,ACPI]
199 acpi_display_output=vendor
200 acpi_display_output=video
201 See above.
203 acpi_irq_balance [HW,ACPI]
204 ACPI will balance active IRQs
205 default in APIC mode
207 acpi_irq_nobalance [HW,ACPI]
208 ACPI will not move active IRQs (default)
209 default in PIC mode
211 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
212 Format: <irq>,<irq>...
214 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
215 use by PCI
216 Format: <irq>,<irq>...
218 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
220 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
221 Format: To spoof as Windows 98: ="Microsoft Windows"
223 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
224 acpi_osi="string1" # add string1 -- only one string
225 acpi_osi="!string2" # remove built-in string2
226 acpi_osi= # disable all strings
228 acpi_pm_good [X86]
229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
233 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
234 Format: { level | edge | high | low }
236 acpi_serialize [HW,ACPI] force serialization of AML methods
238 acpi_skip_timer_override [HW,ACPI]
239 Recognize and ignore IRQ0/pin2 Interrupt Override.
240 For broken nForce2 BIOS resulting in XT-PIC timer.
242 acpi_sleep= [HW,ACPI] Sleep options
243 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
244 old_ordering, s4_nonvs }
245 See Documentation/power/video.txt for information on
246 s3_bios and s3_mode.
247 s3_beep is for debugging; it makes the PC's speaker beep
248 as soon as the kernel's real-mode entry point is called.
249 s4_nohwsig prevents ACPI hardware signature from being
250 used during resume from hibernation.
251 old_ordering causes the ACPI 1.0 ordering of the _PTS
252 control method, with respect to putting devices into
253 low power states, to be enforced (the ACPI 2.0 ordering
254 of _PTS is used by default).
255 s4_nonvs prevents the kernel from saving/restoring the
256 ACPI NVS memory during hibernation.
258 acpi_use_timer_override [HW,ACPI]
259 Use timer override. For some broken Nvidia NF5 boards
260 that require a timer override, but don't have HPET
262 acpi_enforce_resources= [ACPI]
263 { strict | lax | no }
264 Check for resource conflicts between native drivers
265 and ACPI OperationRegions (SystemIO and SystemMemory
266 only). IO ports and memory declared in ACPI might be
267 used by the ACPI subsystem in arbitrary AML code and
268 can interfere with legacy drivers.
269 strict (default): access to resources claimed by ACPI
270 is denied; legacy drivers trying to access reserved
271 resources will fail to bind to device using them.
272 lax: access to resources claimed by ACPI is allowed;
273 legacy drivers trying to access reserved resources
274 will bind successfully but a warning message is logged.
275 no: ACPI OperationRegions are not marked as reserved,
276 no further checks are performed.
278 ad1848= [HW,OSS]
279 Format: <io>,<irq>,<dma>,<dma2>,<type>
281 add_efi_memmap [EFI; X86] Include EFI memory map in
282 kernel's map of available physical RAM.
284 advansys= [HW,SCSI]
285 See header of drivers/scsi/advansys.c.
287 advwdt= [HW,WDT] Advantech WDT
288 Format: <iostart>,<iostop>
290 aedsp16= [HW,OSS] Audio Excel DSP 16
291 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
292 See also header of sound/oss/aedsp16.c.
294 agp= [AGP]
295 { off | try_unsupported }
296 off: disable AGP support
297 try_unsupported: try to drive unsupported chipsets
298 (may crash computer or cause data corruption)
300 aha152x= [HW,SCSI]
301 See Documentation/scsi/aha152x.txt.
303 aha1542= [HW,SCSI]
304 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
306 aic7xxx= [HW,SCSI]
307 See Documentation/scsi/aic7xxx.txt.
309 aic79xx= [HW,SCSI]
310 See Documentation/scsi/aic79xx.txt.
312 amd_iommu= [HW,X86-84]
313 Pass parameters to the AMD IOMMU driver in the system.
314 Possible values are:
315 isolate - enable device isolation (each device, as far
316 as possible, will get its own protection
317 domain) [default]
318 share - put every device behind one IOMMU into the
319 same protection domain
320 fullflush - enable flushing of IO/TLB entries when
321 they are unmapped. Otherwise they are
322 flushed before they will be reused, which
323 is a lot of faster
325 amijoy.map= [HW,JOY] Amiga joystick support
326 Map of devices attached to JOY0DAT and JOY1DAT
327 Format: <a>,<b>
328 See also Documentation/kernel/input/joystick.txt
330 analog.map= [HW,JOY] Analog joystick and gamepad support
331 Specifies type or capabilities of an analog joystick
332 connected to one of 16 gameports
333 Format: <type1>,<type2>,..<type16>
335 apc= [HW,SPARC]
336 Power management functions (SPARCstation-4/5 + deriv.)
337 Format: noidle
338 Disable APC CPU standby support. SPARCstation-Fox does
339 not play well with APC CPU idle - disable it if you have
340 APC and your system crashes randomly.
342 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
343 Change the output verbosity whilst booting
344 Format: { quiet (default) | verbose | debug }
345 Change the amount of debugging information output
346 when initialising the APIC and IO-APIC components.
348 apm= [APM] Advanced Power Management
349 See header of arch/x86/kernel/apm_32.c.
351 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
352 Format: <io>,<irq>,<nodeID>
354 ataflop= [HW,M68k]
356 atarimouse= [HW,MOUSE] Atari Mouse
358 atascsi= [HW,SCSI] Atari SCSI
360 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
361 EzKey and similar keyboards
363 atkbd.reset= [HW] Reset keyboard during initialization
365 atkbd.set= [HW] Select keyboard code set
366 Format: <int> (2 = AT (default), 3 = PS/2)
368 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
369 keyboards
371 atkbd.softraw= [HW] Choose between synthetic and real raw mode
372 Format: <bool> (0 = real, 1 = synthetic (default))
374 atkbd.softrepeat= [HW]
375 Use software keyboard repeat
377 autotest [IA64]
379 baycom_epp= [HW,AX25]
380 Format: <io>,<mode>
382 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
383 Format: <io>,<mode>
384 See header of drivers/net/hamradio/baycom_par.c.
386 baycom_ser_fdx= [HW,AX25]
387 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
388 Format: <io>,<irq>,<mode>[,<baud>]
389 See header of drivers/net/hamradio/baycom_ser_fdx.c.
391 baycom_ser_hdx= [HW,AX25]
392 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
393 Format: <io>,<irq>,<mode>
394 See header of drivers/net/hamradio/baycom_ser_hdx.c.
396 boot_delay= Milliseconds to delay each printk during boot.
397 Values larger than 10 seconds (10000) are changed to
398 no delay (0).
399 Format: integer
401 bootmem_debug [KNL] Enable bootmem allocator debug messages.
403 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
404 bttv.radio= Most important insmod options are available as
405 kernel args too.
406 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
407 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
409 BusLogic= [HW,SCSI]
410 See drivers/scsi/BusLogic.c, comment before function
411 BusLogic_ParseDriverOptions().
413 c101= [NET] Moxa C101 synchronous serial card
415 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
416 Sometimes CPU hardware bugs make them report the cache
417 size incorrectly. The kernel will attempt work arounds
418 to fix known problems, but for some CPUs it is not
419 possible to determine what the correct size should be.
420 This option provides an override for these situations.
422 capability.disable=
423 [SECURITY] Disable capabilities. This would normally
424 be used only if an alternative security model is to be
425 configured. Potentially dangerous and should only be
426 used if you are entirely sure of the consequences.
428 ccw_timeout_log [S390]
429 See Documentation/s390/CommonIO for details.
431 cgroup_disable= [KNL] Disable a particular controller
432 Format: {name of the controller(s) to disable}
433 {Currently supported controllers - "memory"}
435 checkreqprot [SELINUX] Set initial checkreqprot flag value.
436 Format: { "0" | "1" }
437 See security/selinux/Kconfig help text.
438 0 -- check protection applied by kernel (includes
439 any implied execute protection).
440 1 -- check protection requested by application.
441 Default value is set via a kernel config option.
442 Value can be changed at runtime via
443 /selinux/checkreqprot.
445 cio_ignore= [S390]
446 See Documentation/s390/CommonIO for details.
448 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
449 [Deprecated]
450 Forces specified clocksource (if available) to be used
451 when calculating gettimeofday(). If specified
452 clocksource is not available, it defaults to PIT.
453 Format: { pit | tsc | cyclone | pmtmr }
455 clocksource= [GENERIC_TIME] Override the default clocksource
456 Format: <string>
457 Override the default clocksource and use the clocksource
458 with the name specified.
459 Some clocksource names to choose from, depending on
460 the platform:
461 [all] jiffies (this is the base, fallback clocksource)
462 [ACPI] acpi_pm
463 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
464 pxa_timer,timer3,32k_counter,timer0_1
465 [AVR32] avr32
466 [X86-32] pit,hpet,tsc,vmi-timer;
467 scx200_hrt on Geode; cyclone on IBM x440
468 [MIPS] MIPS
469 [PARISC] cr16
470 [S390] tod
471 [SH] SuperH
472 [SPARC64] tick
473 [X86-64] hpet,tsc
475 clearcpuid=BITNUM [X86]
476 Disable CPUID feature X for the kernel. See
477 arch/x86/include/asm/cpufeature.h for the valid bit
478 numbers. Note the Linux specific bits are not necessarily
479 stable over kernel options, but the vendor specific
480 ones should be.
481 Also note that user programs calling CPUID directly
482 or using the feature without checking anything
483 will still see it. This just prevents it from
484 being used by the kernel or shown in /proc/cpuinfo.
485 Also note the kernel might malfunction if you disable
486 some critical bits.
488 cmo_free_hint= [PPC] Format: { yes | no }
489 Specify whether pages are marked as being inactive
490 when they are freed. This is used in CMO environments
491 to determine OS memory pressure for page stealing by
492 a hypervisor.
493 Default: yes
495 code_bytes [X86] How many bytes of object code to print
496 in an oops report.
497 Range: 0 - 8192
498 Default: 64
500 com20020= [HW,NET] ARCnet - COM20020 chipset
501 Format:
502 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
504 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
505 Format: <io>[,<irq>]
507 com90xx= [HW,NET]
508 ARCnet - COM90xx chipset (memory-mapped buffers)
509 Format: <io>[,<irq>[,<memstart>]]
511 condev= [HW,S390] console device
512 conmode=
514 console= [KNL] Output console device and options.
516 tty<n> Use the virtual console device <n>.
518 ttyS<n>[,options]
519 ttyUSB0[,options]
520 Use the specified serial port. The options are of
521 the form "bbbbpnf", where "bbbb" is the baud rate,
522 "p" is parity ("n", "o", or "e"), "n" is number of
523 bits, and "f" is flow control ("r" for RTS or
524 omit it). Default is "9600n8".
526 See Documentation/serial-console.txt for more
527 information. See
528 Documentation/networking/netconsole.txt for an
529 alternative.
531 uart[8250],io,<addr>[,options]
532 uart[8250],mmio,<addr>[,options]
533 Start an early, polled-mode console on the 8250/16550
534 UART at the specified I/O port or MMIO address,
535 switching to the matching ttyS device later. The
536 options are the same as for ttyS, above.
538 If the device connected to the port is not a TTY but a braille
539 device, prepend "brl," before the device type, for instance
540 console=brl,ttyS0
541 For now, only VisioBraille is supported.
543 consoleblank= [KNL] The console blank (screen saver) timeout in
544 seconds. Defaults to 10*60 = 10mins. A value of 0
545 disables the blank timer.
547 coredump_filter=
548 [KNL] Change the default value for
549 /proc/<pid>/coredump_filter.
550 See also Documentation/filesystems/proc.txt.
552 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
553 Format:
554 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
556 crashkernel=nn[KMG]@ss[KMG]
557 [KNL] Reserve a chunk of physical memory to
558 hold a kernel to switch to with kexec on panic.
560 crashkernel=range1:size1[,range2:size2,...][@offset]
561 [KNL] Same as above, but depends on the memory
562 in the running system. The syntax of range is
563 start-[end] where start and end are both
564 a memory unit (amount[KMG]). See also
565 Documentation/kdump/kdump.txt for a example.
567 cs89x0_dma= [HW,NET]
568 Format: <dma>
570 cs89x0_media= [HW,NET]
571 Format: { rj45 | aui | bnc }
573 dasd= [HW,NET]
574 See header of drivers/s390/block/dasd_devmap.c.
576 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
577 (one device per port)
578 Format: <port#>,<type>
579 See also Documentation/input/joystick-parport.txt
581 debug [KNL] Enable kernel debugging (events log level).
583 debug_locks_verbose=
584 [KNL] verbose self-tests
585 Format=<0|1>
586 Print debugging info while doing the locking API
587 self-tests.
588 We default to 0 (no extra messages), setting it to
589 1 will print _a lot_ more information - normally
590 only useful to kernel developers.
592 debug_objects [KNL] Enable object debugging
594 no_debug_objects
595 [KNL] Disable object debugging
597 debugpat [X86] Enable PAT debugging
599 decnet.addr= [HW,NET]
600 Format: <area>[,<node>]
601 See also Documentation/networking/decnet.txt.
603 default_hugepagesz=
604 [same as hugepagesz=] The size of the default
605 HugeTLB page size. This is the size represented by
606 the legacy /proc/ hugepages APIs, used for SHM, and
607 default size when mounting hugetlbfs filesystems.
608 Defaults to the default architecture's huge page size
609 if not specified.
611 dhash_entries= [KNL]
612 Set number of hash buckets for dentry cache.
614 digi= [HW,SERIAL]
615 IO parameters + enable/disable command.
617 digiepca= [HW,SERIAL]
618 See drivers/char/README.epca and
619 Documentation/serial/digiepca.txt.
621 disable_mtrr_cleanup [X86]
622 The kernel tries to adjust MTRR layout from continuous
623 to discrete, to make X server driver able to add WB
624 entry later. This parameter disables that.
626 disable_mtrr_trim [X86, Intel and AMD only]
627 By default the kernel will trim any uncacheable
628 memory out of your available memory pool based on
629 MTRR settings. This parameter disables that behavior,
630 possibly causing your machine to run very slowly.
632 disable_timer_pin_1 [X86]
633 Disable PIN 1 of APIC timer
634 Can be useful to work around chipset bugs.
636 dmasound= [HW,OSS] Sound subsystem buffers
638 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
639 this option disables the debugging code at boot.
641 dma_debug_entries=<number>
642 This option allows to tune the number of preallocated
643 entries for DMA-API debugging code. One entry is
644 required per DMA-API allocation. Use this if the
645 DMA-API debugging code disables itself because the
646 architectural default is too low.
648 dma_debug_driver=<driver_name>
649 With this option the DMA-API debugging driver
650 filter feature can be enabled at boot time. Just
651 pass the driver to filter for as the parameter.
652 The filter can be disabled or changed to another
653 driver later using sysfs.
655 dscc4.setup= [NET]
657 dtc3181e= [HW,SCSI]
659 dynamic_printk Enables pr_debug()/dev_dbg() calls if
660 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
661 These can also be switched on/off via
662 <debugfs>/dynamic_printk/modules
664 earlycon= [KNL] Output early console device and options.
665 uart[8250],io,<addr>[,options]
666 uart[8250],mmio,<addr>[,options]
667 Start an early, polled-mode console on the 8250/16550
668 UART at the specified I/O port or MMIO address.
669 The options are the same as for ttyS, above.
671 earlyprintk= [X86,SH,BLACKFIN]
672 earlyprintk=vga
673 earlyprintk=serial[,ttySn[,baudrate]]
674 earlyprintk=dbgp
676 Append ",keep" to not disable it when the real console
677 takes over.
679 Only vga or serial or usb debug port at a time.
681 Currently only ttyS0 and ttyS1 are supported.
683 Interaction with the standard serial driver is not
684 very good.
686 The VGA output is eventually overwritten by the real
687 console.
689 eata= [HW,SCSI]
691 edd= [EDD]
692 Format: {"off" | "on" | "skip[mbr]"}
694 eisa_irq_edge= [PARISC,HW]
695 See header of drivers/parisc/eisa.c.
697 elanfreq= [X86-32]
698 See comment before function elanfreq_setup() in
699 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
701 elevator= [IOSCHED]
702 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
703 See Documentation/block/as-iosched.txt and
704 Documentation/block/deadline-iosched.txt for details.
706 elfcorehdr= [IA64,PPC,SH,X86]
707 Specifies physical address of start of kernel core
708 image elf header. Generally kexec loader will
709 pass this option to capture kernel.
710 See Documentation/kdump/kdump.txt for details.
712 enable_mtrr_cleanup [X86]
713 The kernel tries to adjust MTRR layout from continuous
714 to discrete, to make X server driver able to add WB
715 entry later. This parameter enables that.
717 enable_timer_pin_1 [X86]
718 Enable PIN 1 of APIC timer
719 Can be useful to work around chipset bugs
720 (in particular on some ATI chipsets).
721 The kernel tries to set a reasonable default.
723 enforcing [SELINUX] Set initial enforcing status.
724 Format: {"0" | "1"}
725 See security/selinux/Kconfig help text.
726 0 -- permissive (log only, no denials).
727 1 -- enforcing (deny and log).
728 Default value is 0.
729 Value can be changed at runtime via /selinux/enforce.
731 ether= [HW,NET] Ethernet cards parameters
732 This option is obsoleted by the "netdev=" option, which
733 has equivalent usage. See its documentation for details.
735 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
736 Format: <io>[,<irq>]
738 failslab=
739 fail_page_alloc=
740 fail_make_request=[KNL]
741 General fault injection mechanism.
742 Format: <interval>,<probability>,<space>,<times>
743 See also /Documentation/fault-injection/.
745 fd_mcs= [HW,SCSI]
746 See header of drivers/scsi/fd_mcs.c.
748 fdomain= [HW,SCSI]
749 See header of drivers/scsi/fdomain.c.
751 floppy= [HW]
752 See Documentation/blockdev/floppy.txt.
754 force_pal_cache_flush
755 [IA-64] Avoid check_sal_cache_flush which may hang on
756 buggy SAL_CACHE_FLUSH implementations. Using this
757 parameter will force ia64_sal_cache_flush to call
758 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
760 ftrace=[tracer]
761 [FTRACE] will set and start the specified tracer
762 as early as possible in order to facilitate early
763 boot debugging.
765 ftrace_dump_on_oops
766 [FTRACE] will dump the trace buffers on oops.
768 ftrace_filter=[function-list]
769 [FTRACE] Limit the functions traced by the function
770 tracer at boot up. function-list is a comma separated
771 list of functions. This list can be changed at run
772 time by the set_ftrace_filter file in the debugfs
773 tracing directory.
775 ftrace_notrace=[function-list]
776 [FTRACE] Do not trace the functions specified in
777 function-list. This list can be changed at run time
778 by the set_ftrace_notrace file in the debugfs
779 tracing directory.
781 gamecon.map[2|3]=
782 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
783 support via parallel port (up to 5 devices per port)
784 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
785 See also Documentation/input/joystick-parport.txt
787 gamma= [HW,DRM]
789 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
790 Format: off | on
791 default: on
793 gcov_persist= [GCOV] When non-zero (default), profiling data for
794 kernel modules is saved and remains accessible via
795 debugfs, even when the module is unloaded/reloaded.
796 When zero, profiling data is discarded and associated
797 debugfs files are removed at module unload time.
799 gdth= [HW,SCSI]
800 See header of drivers/scsi/gdth.c.
802 gpt [EFI] Forces disk with valid GPT signature but
803 invalid Protective MBR to be treated as GPT.
805 gvp11= [HW,SCSI]
807 hashdist= [KNL,NUMA] Large hashes allocated during boot
808 are distributed across NUMA nodes. Defaults on
809 for 64bit NUMA, off otherwise.
810 Format: 0 | 1 (for off | on)
812 hcl= [IA-64] SGI's Hardware Graph compatibility layer
814 hd= [EIDE] (E)IDE hard drive subsystem geometry
815 Format: <cyl>,<head>,<sect>
817 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
818 size of <nn>. This works even on boxes that have no
819 highmem otherwise. This also works to reduce highmem
820 size on bigger boxes.
822 highres= [KNL] Enable/disable high resolution timer mode.
823 Valid parameters: "on", "off"
824 Default: "on"
826 hisax= [HW,ISDN]
827 See Documentation/isdn/README.HiSax.
829 hlt [BUGS=ARM,SH]
831 hpet= [X86-32,HPET] option to control HPET usage
832 Format: { enable (default) | disable | force |
833 verbose }
834 disable: disable HPET and use PIT instead
835 force: allow force enabled of undocumented chips (ICH4,
836 VIA, nVidia)
837 verbose: show contents of HPET registers during setup
839 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
840 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
841 On x86-64 and powerpc, this option can be specified
842 multiple times interleaved with hugepages= to reserve
843 huge pages of different sizes. Valid pages sizes on
844 x86-64 are 2M (when the CPU supports "pse") and 1G
845 (when the CPU supports the "pdpe1gb" cpuinfo flag)
846 Note that 1GB pages can only be allocated at boot time
847 using hugepages= and not freed afterwards.
849 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
850 terminal devices. Valid values: 0..8
851 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
852 If specified, z/VM IUCV HVC accepts connections
853 from listed z/VM user IDs only.
855 i2c_bus= [HW] Override the default board specific I2C bus speed
856 or register an additional I2C bus that is not
857 registered from board initialization code.
858 Format:
859 <bus_id>,<clkrate>
861 i8042.debug [HW] Toggle i8042 debug mode
862 i8042.direct [HW] Put keyboard port into non-translated mode
863 i8042.dumbkbd [HW] Pretend that controller can only read data from
864 keyboard and cannot control its state
865 (Don't attempt to blink the leds)
866 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
867 i8042.nokbd [HW] Don't check/create keyboard port
868 i8042.noloop [HW] Disable the AUX Loopback command while probing
869 for the AUX port
870 i8042.nomux [HW] Don't check presence of an active multiplexing
871 controller
872 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
873 controllers
874 i8042.panicblink=
875 [HW] Frequency with which keyboard LEDs should blink
876 when kernel panics (default is 0.5 sec)
877 i8042.reset [HW] Reset the controller during init and cleanup
878 i8042.unlock [HW] Unlock (ignore) the keylock
880 i810= [HW,DRM]
882 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
883 indicates that the driver is running on unsupported
884 hardware.
885 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
886 does not match list of supported models.
887 i8k.power_status
888 [HW] Report power status in /proc/i8k
889 (disabled by default)
890 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
891 capability is set.
893 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
894 See Documentation/mca.txt.
896 icn= [HW,ISDN]
897 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
899 ide-core.nodma= [HW] (E)IDE subsystem
900 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
901 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
902 .cdrom .chs .ignore_cable are additional options
903 See Documentation/ide/ide.txt.
905 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
906 Claim all unknown PCI IDE storage controllers.
908 idle= [X86]
909 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
910 Poll forces a polling idle loop that can slightly
911 improve the performance of waking up a idle CPU, but
912 will use a lot of power and make the system run hot.
913 Not recommended.
914 idle=mwait: On systems which support MONITOR/MWAIT but
915 the kernel chose to not use it because it doesn't save
916 as much power as a normal idle loop, use the
917 MONITOR/MWAIT idle loop anyways. Performance should be
918 the same as idle=poll.
919 idle=halt: Halt is forced to be used for CPU idle.
920 In such case C2/C3 won't be used again.
921 idle=nomwait: Disable mwait for CPU C-states
923 ignore_loglevel [KNL]
924 Ignore loglevel setting - this will print /all/
925 kernel messages to the console. Useful for debugging.
927 ihash_entries= [KNL]
928 Set number of hash buckets for inode cache.
930 ima_audit= [IMA]
931 Format: { "0" | "1" }
932 0 -- integrity auditing messages. (Default)
933 1 -- enable informational integrity auditing messages.
935 ima_hash= [IMA]
936 Formt: { "sha1" | "md5" }
937 default: "sha1"
939 ima_tcb [IMA]
940 Load a policy which meets the needs of the Trusted
941 Computing Base. This means IMA will measure all
942 programs exec'd, files mmap'd for exec, and all files
943 opened for read by uid=0.
945 in2000= [HW,SCSI]
946 See header of drivers/scsi/in2000.c.
948 init= [KNL]
949 Format: <full_path>
950 Run specified binary instead of /sbin/init as init
951 process.
953 initcall_debug [KNL] Trace initcalls as they are executed. Useful
954 for working out where the kernel is dying during
955 startup.
957 initrd= [BOOT] Specify the location of the initial ramdisk
959 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
960 Format: <irq>
962 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
963 on
964 Enable intel iommu driver.
965 off
966 Disable intel iommu driver.
967 igfx_off [Default Off]
968 By default, gfx is mapped as normal device. If a gfx
969 device has a dedicated DMAR unit, the DMAR unit is
970 bypassed by not enabling DMAR with this option. In
971 this case, gfx device will use physical address for
972 DMA.
973 forcedac [x86_64]
974 With this option iommu will not optimize to look
975 for io virtual address below 32 bit forcing dual
976 address cycle on pci bus for cards supporting greater
977 than 32 bit addressing. The default is to look
978 for translation below 32 bit and if not available
979 then look in the higher range.
980 strict [Default Off]
981 With this option on every unmap_single operation will
982 result in a hardware IOTLB flush operation as opposed
983 to batching them for performance.
985 inttest= [IA64]
987 iomem= Disable strict checking of access to MMIO memory
988 strict regions from userspace.
989 relaxed
991 iommu= [x86]
992 off
993 force
994 noforce
995 biomerge
996 panic
997 nopanic
998 merge
999 nomerge
1000 forcesac
1001 soft
1002 pt [x86, IA64]
1004 io7= [HW] IO7 for Marvel based alpha systems
1005 See comment before marvel_specify_io7 in
1006 arch/alpha/kernel/core_marvel.c.
1008 io_delay= [X86] I/O delay method
1009 0x80
1010 Standard port 0x80 based delay
1011 0xed
1012 Alternate port 0xed based delay (needed on some systems)
1013 udelay
1014 Simple two microseconds delay
1015 none
1016 No delay
1018 ip= [IP_PNP]
1019 See Documentation/filesystems/nfsroot.txt.
1021 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1022 See comment before ip2_setup() in
1023 drivers/char/ip2/ip2base.c.
1025 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1026 See header of drivers/scsi/ips.c.
1028 irqfixup [HW]
1029 When an interrupt is not handled search all handlers
1030 for it. Intended to get systems with badly broken
1031 firmware running.
1033 irqpoll [HW]
1034 When an interrupt is not handled search all handlers
1035 for it. Also check all handlers each timer
1036 interrupt. Intended to get systems with badly broken
1037 firmware running.
1039 isapnp= [ISAPNP]
1040 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1042 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1043 Format:
1044 <cpu number>,...,<cpu number>
1045 or
1046 <cpu number>-<cpu number>
1047 (must be a positive range in ascending order)
1048 or a mixture
1049 <cpu number>,...,<cpu number>-<cpu number>
1051 This option can be used to specify one or more CPUs
1052 to isolate from the general SMP balancing and scheduling
1053 algorithms. You can move a process onto or off an
1054 "isolated" CPU via the CPU affinity syscalls or cpuset.
1055 <cpu number> begins at 0 and the maximum value is
1056 "number of CPUs in system - 1".
1058 This option is the preferred way to isolate CPUs. The
1059 alternative -- manually setting the CPU mask of all
1060 tasks in the system -- can cause problems and
1061 suboptimal load balancer performance.
1063 iucv= [HW,NET]
1065 js= [HW,JOY] Analog joystick
1066 See Documentation/input/joystick.txt.
1068 keepinitrd [HW,ARM]
1070 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1071 specifies the amount of memory usable by the kernel
1072 for non-movable allocations. The requested amount is
1073 spread evenly throughout all nodes in the system. The
1074 remaining memory in each node is used for Movable
1075 pages. In the event, a node is too small to have both
1076 kernelcore and Movable pages, kernelcore pages will
1077 take priority and other nodes will have a larger number
1078 of kernelcore pages. The Movable zone is used for the
1079 allocation of pages that may be reclaimed or moved
1080 by the page migration subsystem. This means that
1081 HugeTLB pages may not be allocated from this zone.
1082 Note that allocations like PTEs-from-HighMem still
1083 use the HighMem zone if it exists, and the Normal
1084 zone if it does not.
1086 kgdboc= [HW] kgdb over consoles.
1087 Requires a tty driver that supports console polling.
1088 (only serial supported for now)
1089 Format: <serial_device>[,baud]
1091 kmac= [MIPS] korina ethernet MAC address.
1092 Configure the RouterBoard 532 series on-chip
1093 Ethernet adapter MAC address.
1095 kmemleak= [KNL] Boot-time kmemleak enable/disable
1096 Valid arguments: on, off
1097 Default: on
1099 kstack=N [X86] Print N words from the kernel stack
1100 in oops dumps.
1102 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1103 Default is 0 (don't ignore, but inject #GP)
1105 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1106 Default is 1 (enabled)
1108 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1109 Default is 0 (off)
1111 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1112 for all guests.
1113 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1115 kvm-intel.bypass_guest_pf=
1116 [KVM,Intel] Disables bypassing of guest page faults
1117 on Intel chips. Default is 1 (enabled)
1119 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1120 (virtualized MMU) support on capable Intel chips.
1121 Default is 1 (enabled)
1123 kvm-intel.emulate_invalid_guest_state=
1124 [KVM,Intel] Enable emulation of invalid guest states
1125 Default is 0 (disabled)
1127 kvm-intel.flexpriority=
1128 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1129 Default is 1 (enabled)
1131 kvm-intel.unrestricted_guest=
1132 [KVM,Intel] Disable unrestricted guest feature
1133 (virtualized real and unpaged mode) on capable
1134 Intel chips. Default is 1 (enabled)
1136 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1137 feature (tagged TLBs) on capable Intel chips.
1138 Default is 1 (enabled)
1140 l2cr= [PPC]
1142 l3cr= [PPC]
1144 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1145 disabled it.
1147 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1148 in C2 power state.
1150 libata.dma= [LIBATA] DMA control
1151 libata.dma=0 Disable all PATA and SATA DMA
1152 libata.dma=1 PATA and SATA Disk DMA only
1153 libata.dma=2 ATAPI (CDROM) DMA only
1154 libata.dma=4 Compact Flash DMA only
1155 Combinations also work, so libata.dma=3 enables DMA
1156 for disks and CDROMs, but not CFs.
1158 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1159 libata.ignore_hpa=0 keep BIOS limits (default)
1160 libata.ignore_hpa=1 ignore limits, using full disk
1162 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1163 when set.
1164 Format: <int>
1166 libata.force= [LIBATA] Force configurations. The format is comma
1167 separated list of "[ID:]VAL" where ID is
1168 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1169 matching port, link or device. Basically, it matches
1170 the ATA ID string printed on console by libata. If
1171 the whole ID part is omitted, the last PORT and DEVICE
1172 values are used. If ID hasn't been specified yet, the
1173 configuration applies to all ports, links and devices.
1175 If only DEVICE is omitted, the parameter applies to
1176 the port and all links and devices behind it. DEVICE
1177 number of 0 either selects the first device or the
1178 first fan-out link behind PMP device. It does not
1179 select the host link. DEVICE number of 15 selects the
1180 host link and device attached to it.
1182 The VAL specifies the configuration to force. As long
1183 as there's no ambiguity shortcut notation is allowed.
1184 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1185 The following configurations can be forced.
1187 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1188 Any ID with matching PORT is used.
1190 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1192 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1193 udma[/][16,25,33,44,66,100,133] notation is also
1194 allowed.
1196 * [no]ncq: Turn on or off NCQ.
1198 * nohrst, nosrst, norst: suppress hard, soft
1199 and both resets.
1201 If there are multiple matching configurations changing
1202 the same attribute, the last one is used.
1204 lmb=debug [KNL] Enable lmb debug messages.
1206 load_ramdisk= [RAM] List of ramdisks to load from floppy
1207 See Documentation/blockdev/ramdisk.txt.
1209 lockd.nlm_grace_period=P [NFS] Assign grace period.
1210 Format: <integer>
1212 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1213 Format: <integer>
1215 lockd.nlm_timeout=T [NFS] Assign timeout value.
1216 Format: <integer>
1218 lockd.nlm_udpport=M [NFS] Assign UDP port.
1219 Format: <integer>
1221 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1222 Format: <irq>
1224 loglevel= All Kernel Messages with a loglevel smaller than the
1225 console loglevel will be printed to the console. It can
1226 also be changed with klogd or other programs. The
1227 loglevels are defined as follows:
1229 0 (KERN_EMERG) system is unusable
1230 1 (KERN_ALERT) action must be taken immediately
1231 2 (KERN_CRIT) critical conditions
1232 3 (KERN_ERR) error conditions
1233 4 (KERN_WARNING) warning conditions
1234 5 (KERN_NOTICE) normal but significant condition
1235 6 (KERN_INFO) informational
1236 7 (KERN_DEBUG) debug-level messages
1238 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1239 Format: { n | nk | nM }
1240 n must be a power of two. The default size
1241 is set in the kernel config file.
1243 logo.nologo [FB] Disables display of the built-in Linux logo.
1244 This may be used to provide more screen space for
1245 kernel log messages and is useful when debugging
1246 kernel boot problems.
1248 lp=0 [LP] Specify parallel ports to use, e.g,
1249 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1250 lp=reset first parallel port). 'lp=0' disables the
1251 lp=auto printer driver. 'lp=reset' (which can be
1252 specified in addition to the ports) causes
1253 attached printers to be reset. Using
1254 lp=port1,port2,... specifies the parallel ports
1255 to associate lp devices with, starting with
1256 lp0. A port specification may be 'none' to skip
1257 that lp device, or a parport name such as
1258 'parport0'. Specifying 'lp=auto' instead of a
1259 port specification list means that device IDs
1260 from each port should be examined, to see if
1261 an IEEE 1284-compliant printer is attached; if
1262 so, the driver will manage that printer.
1263 See also header of drivers/char/lp.c.
1265 lpj=n [KNL]
1266 Sets loops_per_jiffy to given constant, thus avoiding
1267 time-consuming boot-time autodetection (up to 250 ms per
1268 CPU). 0 enables autodetection (default). To determine
1269 the correct value for your kernel, boot with normal
1270 autodetection and see what value is printed. Note that
1271 on SMP systems the preset will be applied to all CPUs,
1272 which is likely to cause problems if your CPUs need
1273 significantly divergent settings. An incorrect value
1274 will cause delays in the kernel to be wrong, leading to
1275 unpredictable I/O errors and other breakage. Although
1276 unlikely, in the extreme case this might damage your
1277 hardware.
1279 ltpc= [NET]
1280 Format: <io>,<irq>,<dma>
1282 mac5380= [HW,SCSI] Format:
1283 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1285 machvec= [IA64] Force the use of a particular machine-vector
1286 (machvec) in a generic kernel.
1287 Example: machvec=hpzx1_swiotlb
1289 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1290 than or equal to this physical address is ignored.
1292 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1293 should make use of. maxcpus=n : n >= 0 limits the
1294 kernel to using 'n' processors. n=0 is a special case,
1295 it is equivalent to "nosmp", which also disables
1296 the IO APIC.
1298 max_loop= [LOOP] Maximum number of loopback devices that can
1299 be mounted
1300 Format: <1-256>
1302 max_luns= [SCSI] Maximum number of LUNs to probe.
1303 Should be between 1 and 2^32-1.
1305 max_report_luns=
1306 [SCSI] Maximum number of LUNs received.
1307 Should be between 1 and 16384.
1309 mcatest= [IA-64]
1311 mce [X86-32] Machine Check Exception
1313 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1315 md= [HW] RAID subsystems devices and level
1316 See Documentation/md.txt.
1318 mdacon= [MDA]
1319 Format: <first>,<last>
1320 Specifies range of consoles to be captured by the MDA.
1322 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1323 Amount of memory to be used when the kernel is not able
1324 to see the whole system memory or for test.
1325 [X86-32] Use together with memmap= to avoid physical
1326 address space collisions. Without memmap= PCI devices
1327 could be placed at addresses belonging to unused RAM.
1329 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1330 memory.
1332 memchunk=nn[KMG]
1333 [KNL,SH] Allow user to override the default size for
1334 per-device physically contiguous DMA buffers.
1336 memmap=exactmap [KNL,X86] Enable setting of an exact
1337 E820 memory map, as specified by the user.
1338 Such memmap=exactmap lines can be constructed based on
1339 BIOS output or other requirements. See the memmap=nn@ss
1340 option description.
1342 memmap=nn[KMG]@ss[KMG]
1343 [KNL] Force usage of a specific region of memory
1344 Region of memory to be used, from ss to ss+nn.
1346 memmap=nn[KMG]#ss[KMG]
1347 [KNL,ACPI] Mark specific memory as ACPI data.
1348 Region of memory to be used, from ss to ss+nn.
1350 memmap=nn[KMG]$ss[KMG]
1351 [KNL,ACPI] Mark specific memory as reserved.
1352 Region of memory to be used, from ss to ss+nn.
1353 Example: Exclude memory from 0x18690000-0x1869ffff
1354 memmap=64K$0x18690000
1355 or
1356 memmap=0x10000$0x18690000
1358 memory_corruption_check=0/1 [X86]
1359 Some BIOSes seem to corrupt the first 64k of
1360 memory when doing things like suspend/resume.
1361 Setting this option will scan the memory
1362 looking for corruption. Enabling this will
1363 both detect corruption and prevent the kernel
1364 from using the memory being corrupted.
1365 However, its intended as a diagnostic tool; if
1366 repeatable BIOS-originated corruption always
1367 affects the same memory, you can use memmap=
1368 to prevent the kernel from using that memory.
1370 memory_corruption_check_size=size [X86]
1371 By default it checks for corruption in the low
1372 64k, making this memory unavailable for normal
1373 use. Use this parameter to scan for
1374 corruption in more or less memory.
1376 memory_corruption_check_period=seconds [X86]
1377 By default it checks for corruption every 60
1378 seconds. Use this parameter to check at some
1379 other rate. 0 disables periodic checking.
1381 memtest= [KNL,X86] Enable memtest
1382 Format: <integer>
1383 default : 0 <disable>
1384 Specifies the number of memtest passes to be
1385 performed. Each pass selects another test
1386 pattern from a given set of patterns. Memtest
1387 fills the memory with this pattern, validates
1388 memory contents and reserves bad memory
1389 regions that are detected.
1391 meye.*= [HW] Set MotionEye Camera parameters
1392 See Documentation/video4linux/meye.txt.
1394 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1395 Multi-Function General Purpose Timers on AMD Geode
1396 platforms.
1398 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1399 the BIOS has incorrectly applied a workaround. TinyBIOS
1400 version 0.98 is known to be affected, 0.99 fixes the
1401 problem by letting the user disable the workaround.
1403 mga= [HW,DRM]
1405 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1406 physical address is ignored.
1408 mini2440= [ARM,HW,KNL]
1409 Format:[0..2][b][c][t]
1410 Default: "0tb"
1411 MINI2440 configuration specification:
1412 0 - The attached screen is the 3.5" TFT
1413 1 - The attached screen is the 7" TFT
1414 2 - The VGA Shield is attached (1024x768)
1415 Leaving out the screen size parameter will not load
1416 the TFT driver, and the framebuffer will be left
1417 unconfigured.
1418 b - Enable backlight. The TFT backlight pin will be
1419 linked to the kernel VESA blanking code and a GPIO
1420 LED. This parameter is not necessary when using the
1421 VGA shield.
1422 c - Enable the s3c camera interface.
1423 t - Reserved for enabling touchscreen support. The
1424 touchscreen support is not enabled in the mainstream
1425 kernel as of 2.6.30, a preliminary port can be found
1426 in the "bleeding edge" mini2440 support kernel at
1427 http://repo.or.cz/w/linux-2.6/mini2440.git
1429 mminit_loglevel=
1430 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1431 parameter allows control of the logging verbosity for
1432 the additional memory initialisation checks. A value
1433 of 0 disables mminit logging and a level of 4 will
1434 log everything. Information is printed at KERN_DEBUG
1435 so loglevel=8 may also need to be specified.
1437 mousedev.tap_time=
1438 [MOUSE] Maximum time between finger touching and
1439 leaving touchpad surface for touch to be considered
1440 a tap and be reported as a left button click (for
1441 touchpads working in absolute mode only).
1442 Format: <msecs>
1443 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1444 reporting absolute coordinates, such as tablets
1445 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1446 reporting absolute coordinates, such as tablets
1448 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1449 is similar to kernelcore except it specifies the
1450 amount of memory used for migratable allocations.
1451 If both kernelcore and movablecore is specified,
1452 then kernelcore will be at *least* the specified
1453 value but may be more. If movablecore on its own
1454 is specified, the administrator must be careful
1455 that the amount of memory usable for all allocations
1456 is not too small.
1458 mpu401= [HW,OSS]
1459 Format: <io>,<irq>
1461 MTD_Partition= [MTD]
1462 Format: <name>,<region-number>,<size>,<offset>
1464 MTD_Region= [MTD] Format:
1465 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1467 mtdparts= [MTD]
1468 See drivers/mtd/cmdlinepart.c.
1470 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1472 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1474 boundary - index of last SLC block on Flex-OneNAND.
1475 The remaining blocks are configured as MLC blocks.
1476 lock - Configure if Flex-OneNAND boundary should be locked.
1477 Once locked, the boundary cannot be changed.
1478 1 indicates lock status, 0 indicates unlock status.
1480 mtdset= [ARM]
1481 ARM/S3C2412 JIVE boot control
1483 See arch/arm/mach-s3c2412/mach-jive.c
1485 mtouchusb.raw_coordinates=
1486 [HW] Make the MicroTouch USB driver use raw coordinates
1487 ('y', default) or cooked coordinates ('n')
1489 mtrr_chunk_size=nn[KMG] [X86]
1490 used for mtrr cleanup. It is largest continuous chunk
1491 that could hold holes aka. UC entries.
1493 mtrr_gran_size=nn[KMG] [X86]
1494 Used for mtrr cleanup. It is granularity of mtrr block.
1495 Default is 1.
1496 Large value could prevent small alignment from
1497 using up MTRRs.
1499 mtrr_spare_reg_nr=n [X86]
1500 Format: <integer>
1501 Range: 0,7 : spare reg number
1502 Default : 1
1503 Used for mtrr cleanup. It is spare mtrr entries number.
1504 Set to 2 or more if your graphical card needs more.
1506 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1508 NCR_D700= [HW,SCSI]
1509 See header of drivers/scsi/NCR_D700.c.
1511 ncr5380= [HW,SCSI]
1513 ncr53c400= [HW,SCSI]
1515 ncr53c400a= [HW,SCSI]
1517 ncr53c406a= [HW,SCSI]
1519 ncr53c8xx= [HW,SCSI]
1521 netdev= [NET] Network devices parameters
1522 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1523 Note that mem_start is often overloaded to mean
1524 something different and driver-specific.
1525 This usage is only documented in each driver source
1526 file if at all.
1528 nf_conntrack.acct=
1529 [NETFILTER] Enable connection tracking flow accounting
1530 0 to disable accounting
1531 1 to enable accounting
1532 Default value depends on CONFIG_NF_CT_ACCT that is
1533 going to be removed in 2.6.29.
1535 nfsaddrs= [NFS]
1536 See Documentation/filesystems/nfsroot.txt.
1538 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1539 See Documentation/filesystems/nfsroot.txt.
1541 nfs.callback_tcpport=
1542 [NFS] set the TCP port on which the NFSv4 callback
1543 channel should listen.
1545 nfs.cache_getent=
1546 [NFS] sets the pathname to the program which is used
1547 to update the NFS client cache entries.
1549 nfs.cache_getent_timeout=
1550 [NFS] sets the timeout after which an attempt to
1551 update a cache entry is deemed to have failed.
1553 nfs.idmap_cache_timeout=
1554 [NFS] set the maximum lifetime for idmapper cache
1555 entries.
1557 nfs.enable_ino64=
1558 [NFS] enable 64-bit inode numbers.
1559 If zero, the NFS client will fake up a 32-bit inode
1560 number for the readdir() and stat() syscalls instead
1561 of returning the full 64-bit number.
1562 The default is to return 64-bit inode numbers.
1564 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1565 when a NMI is triggered.
1566 Format: [state][,regs][,debounce][,die]
1568 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1569 Format: [panic,][num]
1570 Valid num: 0,1,2
1571 0 - turn nmi_watchdog off
1572 1 - use the IO-APIC timer for the NMI watchdog
1573 2 - use the local APIC for the NMI watchdog using
1574 a performance counter. Note: This will use one
1575 performance counter and the local APIC's performance
1576 vector.
1577 When panic is specified, panic when an NMI watchdog
1578 timeout occurs.
1579 This is useful when you use a panic=... timeout and
1580 need the box quickly up again.
1581 Instead of 1 and 2 it is possible to use the following
1582 symbolic names: lapic and ioapic
1583 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1585 netpoll.carrier_timeout=
1586 [NET] Specifies amount of time (in seconds) that
1587 netpoll should wait for a carrier. By default netpoll
1588 waits 4 seconds.
1590 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1591 emulation library even if a 387 maths coprocessor
1592 is present.
1594 no_console_suspend
1595 [HW] Never suspend the console
1596 Disable suspending of consoles during suspend and
1597 hibernate operations. Once disabled, debugging
1598 messages can reach various consoles while the rest
1599 of the system is being put to sleep (ie, while
1600 debugging driver suspend/resume hooks). This may
1601 not work reliably with all consoles, but is known
1602 to work with serial and VGA consoles.
1604 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1605 caches in the slab allocator. Saves per-node memory,
1606 but will impact performance.
1608 noalign [KNL,ARM]
1610 noapic [SMP,APIC] Tells the kernel to not make use of any
1611 IOAPICs that may be present in the system.
1613 nobats [PPC] Do not use BATs for mapping kernel lowmem
1614 on "Classic" PPC cores.
1616 nocache [ARM]
1618 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1620 nodelayacct [KNL] Disable per-task delay accounting
1622 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1624 nodsp [SH] Disable hardware DSP at boot time.
1626 noefi [X86] Disable EFI runtime services support.
1628 noexec [IA-64]
1630 noexec [X86]
1631 On X86-32 available only on PAE configured kernels.
1632 noexec=on: enable non-executable mappings (default)
1633 noexec=off: disable non-executable mappings
1635 noexec32 [X86-64]
1636 This affects only 32-bit executables.
1637 noexec32=on: enable non-executable mappings (default)
1638 read doesn't imply executable mappings
1639 noexec32=off: disable non-executable mappings
1640 read implies executable mappings
1642 nofpu [SH] Disable hardware FPU at boot time.
1644 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1645 register save and restore. The kernel will only save
1646 legacy floating-point registers on task switch.
1648 noxsave [BUGS=X86] Disables x86 extended register state save
1649 and restore using xsave. The kernel will fallback to
1650 enabling legacy floating-point and sse state.
1652 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1653 wfi(ARM) instruction doesn't work correctly and not to
1654 use it. This is also useful when using JTAG debugger.
1656 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1657 instruction doesn't work correctly and not to
1658 use it.
1660 no_file_caps Tells the kernel not to honor file capabilities. The
1661 only way then for a file to be executed with privilege
1662 is to be setuid root or executed by root.
1664 nohalt [IA-64] Tells the kernel not to use the power saving
1665 function PAL_HALT_LIGHT when idle. This increases
1666 power-consumption. On the positive side, it reduces
1667 interrupt wake-up latency, which may improve performance
1668 in certain environments such as networked servers or
1669 real-time systems.
1671 nohz= [KNL] Boottime enable/disable dynamic ticks
1672 Valid arguments: on, off
1673 Default: on
1675 noiotrap [SH] Disables trapped I/O port accesses.
1677 noirqdebug [X86-32] Disables the code which attempts to detect and
1678 disable unhandled interrupt sources.
1680 no_timer_check [X86,APIC] Disables the code which tests for
1681 broken timer IRQ sources.
1683 noisapnp [ISAPNP] Disables ISA PnP code.
1685 noinitrd [RAM] Tells the kernel not to load any configured
1686 initial RAM disk.
1688 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1689 remapping.
1691 nointroute [IA-64]
1693 nojitter [IA64] Disables jitter checking for ITC timers.
1695 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1697 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1699 noltlbs [PPC] Do not use large page/tlb entries for kernel
1700 lowmem mapping on PPC40x.
1702 nomca [IA-64] Disable machine check abort handling
1704 nomce [X86-32] Machine Check Exception
1706 nomfgpt [X86-32] Disable Multi-Function General Purpose
1707 Timer usage (for AMD Geode machines).
1709 norandmaps Don't use address space randomization. Equivalent to
1710 echo 0 > /proc/sys/kernel/randomize_va_space
1712 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1714 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1715 with UP alternatives
1717 noresidual [PPC] Don't use residual data on PReP machines.
1719 noresume [SWSUSP] Disables resume and restores original swap
1720 space.
1722 no-scroll [VGA] Disables scrollback.
1723 This is required for the Braillex ib80-piezo Braille
1724 reader made by F.H. Papenmeier (Germany).
1726 nosbagart [IA-64]
1728 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1730 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1731 and disable the IO APIC. legacy for "maxcpus=0".
1733 nosoftlockup [KNL] Disable the soft-lockup detector.
1735 noswapaccount [KNL] Disable accounting of swap in memory resource
1736 controller. (See Documentation/cgroups/memory.txt)
1738 nosync [HW,M68K] Disables sync negotiation for all devices.
1740 notsc [BUGS=X86-32] Disable Time Stamp Counter
1742 nousb [USB] Disable the USB subsystem
1744 nowb [ARM]
1746 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1748 nptcg= [IA64] Override max number of concurrent global TLB
1749 purges which is reported from either PAL_VM_SUMMARY or
1750 SAL PALO.
1752 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1754 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1755 one of ['zone', 'node', 'default'] can be specified
1756 This can be set from sysctl after boot.
1757 See Documentation/sysctl/vm.txt for details.
1759 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1760 See Documentation/debugging-via-ohci1394.txt for more
1761 info.
1763 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1764 Rather than timing out after 20 ms if an EC
1765 command is not properly ACKed, override the length
1766 of the timeout. We have interrupts disabled while
1767 waiting for the ACK, so if this is set too high
1768 interrupts *may* be lost!
1770 opl3= [HW,OSS]
1771 Format: <io>
1773 oprofile.timer= [HW]
1774 Use timer interrupt instead of performance counters
1776 oprofile.cpu_type= Force an oprofile cpu type
1777 This might be useful if you have an older oprofile
1778 userland or if you want common events.
1779 Format: { arch_perfmon }
1780 arch_perfmon: [X86] Force use of architectural
1781 perfmon on Intel CPUs instead of the
1782 CPU specific event set.
1784 osst= [HW,SCSI] SCSI Tape Driver
1785 Format: <buffer_size>,<write_threshold>
1786 See also Documentation/scsi/st.txt.
1788 panic= [KNL] Kernel behaviour on panic
1789 Format: <timeout>
1791 parkbd.port= [HW] Parallel port number the keyboard adapter is
1792 connected to, default is 0.
1793 Format: <parport#>
1794 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1795 0 for XT, 1 for AT (default is AT).
1796 Format: <mode>
1798 parport= [HW,PPT] Specify parallel ports. 0 disables.
1799 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1800 Use 'auto' to force the driver to use any
1801 IRQ/DMA settings detected (the default is to
1802 ignore detected IRQ/DMA settings because of
1803 possible conflicts). You can specify the base
1804 address, IRQ, and DMA settings; IRQ and DMA
1805 should be numbers, or 'auto' (for using detected
1806 settings on that particular port), or 'nofifo'
1807 (to avoid using a FIFO even if it is detected).
1808 Parallel ports are assigned in the order they
1809 are specified on the command line, starting
1810 with parport0.
1812 parport_init_mode= [HW,PPT]
1813 Configure VIA parallel port to operate in
1814 a specific mode. This is necessary on Pegasos
1815 computer where firmware has no options for setting
1816 up parallel port mode and sets it to spp.
1817 Currently this function knows 686a and 8231 chips.
1818 Format: [spp|ps2|epp|ecp|ecpepp]
1820 pas2= [HW,OSS] Format:
1821 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1823 pas16= [HW,SCSI]
1824 See header of drivers/scsi/pas16.c.
1826 pause_on_oops=
1827 Halt all CPUs after the first oops has been printed for
1828 the specified number of seconds. This is to be used if
1829 your oopses keep scrolling off the screen.
1831 pcbit= [HW,ISDN]
1833 pcd. [PARIDE]
1834 See header of drivers/block/paride/pcd.c.
1835 See also Documentation/blockdev/paride.txt.
1837 pci=option[,option...] [PCI] various PCI subsystem options:
1838 earlydump [X86] dump PCI config space before the kernel
1839 changes anything
1840 off [X86] don't probe for the PCI bus
1841 bios [X86-32] force use of PCI BIOS, don't access
1842 the hardware directly. Use this if your machine
1843 has a non-standard PCI host bridge.
1844 nobios [X86-32] disallow use of PCI BIOS, only direct
1845 hardware access methods are allowed. Use this
1846 if you experience crashes upon bootup and you
1847 suspect they are caused by the BIOS.
1848 conf1 [X86] Force use of PCI Configuration
1849 Mechanism 1.
1850 conf2 [X86] Force use of PCI Configuration
1851 Mechanism 2.
1852 noaer [PCIE] If the PCIEAER kernel config parameter is
1853 enabled, this kernel boot option can be used to
1854 disable the use of PCIE advanced error reporting.
1855 nodomains [PCI] Disable support for multiple PCI
1856 root domains (aka PCI segments, in ACPI-speak).
1857 nommconf [X86] Disable use of MMCONFIG for PCI
1858 Configuration
1859 check_enable_amd_mmconf [X86] check for and enable
1860 properly configured MMIO access to PCI
1861 config space on AMD family 10h CPU
1862 nomsi [MSI] If the PCI_MSI kernel config parameter is
1863 enabled, this kernel boot option can be used to
1864 disable the use of MSI interrupts system-wide.
1865 noioapicquirk [APIC] Disable all boot interrupt quirks.
1866 Safety option to keep boot IRQs enabled. This
1867 should never be necessary.
1868 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1869 primary IO-APIC for bridges that cannot disable
1870 boot IRQs. This fixes a source of spurious IRQs
1871 when the system masks IRQs.
1872 noioapicreroute [APIC] Disable workaround that uses the
1873 boot IRQ equivalent of an IRQ that connects to
1874 a chipset where boot IRQs cannot be disabled.
1875 The opposite of ioapicreroute.
1876 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1877 routing table. These calls are known to be buggy
1878 on several machines and they hang the machine
1879 when used, but on other computers it's the only
1880 way to get the interrupt routing table. Try
1881 this option if the kernel is unable to allocate
1882 IRQs or discover secondary PCI buses on your
1883 motherboard.
1884 rom [X86] Assign address space to expansion ROMs.
1885 Use with caution as certain devices share
1886 address decoders between ROMs and other
1887 resources.
1888 norom [X86] Do not assign address space to
1889 expansion ROMs that do not already have
1890 BIOS assigned address ranges.
1891 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1892 assigned automatically to PCI devices. You can
1893 make the kernel exclude IRQs of your ISA cards
1894 this way.
1895 pirqaddr=0xAAAAA [X86] Specify the physical address
1896 of the PIRQ table (normally generated
1897 by the BIOS) if it is outside the
1898 F0000h-100000h range.
1899 lastbus=N [X86] Scan all buses thru bus #N. Can be
1900 useful if the kernel is unable to find your
1901 secondary buses and you want to tell it
1902 explicitly which ones they are.
1903 assign-busses [X86] Always assign all PCI bus
1904 numbers ourselves, overriding
1905 whatever the firmware may have done.
1906 usepirqmask [X86] Honor the possible IRQ mask stored
1907 in the BIOS $PIR table. This is needed on
1908 some systems with broken BIOSes, notably
1909 some HP Pavilion N5400 and Omnibook XE3
1910 notebooks. This will have no effect if ACPI
1911 IRQ routing is enabled.
1912 noacpi [X86] Do not use ACPI for IRQ routing
1913 or for PCI scanning.
1914 use_crs [X86] Use _CRS for PCI resource
1915 allocation.
1916 routeirq Do IRQ routing for all PCI devices.
1917 This is normally done in pci_enable_device(),
1918 so this option is a temporary workaround
1919 for broken drivers that don't call it.
1920 skip_isa_align [X86] do not align io start addr, so can
1921 handle more pci cards
1922 firmware [ARM] Do not re-enumerate the bus but instead
1923 just use the configuration from the
1924 bootloader. This is currently used on
1925 IXP2000 systems where the bus has to be
1926 configured a certain way for adjunct CPUs.
1927 noearly [X86] Don't do any early type 1 scanning.
1928 This might help on some broken boards which
1929 machine check when some devices' config space
1930 is read. But various workarounds are disabled
1931 and some IOMMU drivers will not work.
1932 bfsort Sort PCI devices into breadth-first order.
1933 This sorting is done to get a device
1934 order compatible with older (<= 2.4) kernels.
1935 nobfsort Don't sort PCI devices into breadth-first order.
1936 cbiosize=nn[KMG] The fixed amount of bus space which is
1937 reserved for the CardBus bridge's IO window.
1938 The default value is 256 bytes.
1939 cbmemsize=nn[KMG] The fixed amount of bus space which is
1940 reserved for the CardBus bridge's memory
1941 window. The default value is 64 megabytes.
1942 resource_alignment=
1943 Format:
1944 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1945 Specifies alignment and device to reassign
1946 aligned memory resources.
1947 If <order of align> is not specified,
1948 PAGE_SIZE is used as alignment.
1949 PCI-PCI bridge can be specified, if resource
1950 windows need to be expanded.
1951 ecrc= Enable/disable PCIe ECRC (transaction layer
1952 end-to-end CRC checking).
1953 bios: Use BIOS/firmware settings. This is the
1954 the default.
1955 off: Turn ECRC off
1956 on: Turn ECRC on.
1958 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1959 Management.
1960 off Disable ASPM.
1961 force Enable ASPM even on devices that claim not to support it.
1962 WARNING: Forcing ASPM on may cause system lockups.
1964 pcmv= [HW,PCMCIA] BadgePAD 4
1966 pd. [PARIDE]
1967 See Documentation/blockdev/paride.txt.
1969 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1970 boot time.
1971 Format: { 0 | 1 }
1972 See arch/parisc/kernel/pdc_chassis.c
1974 percpu_alloc= Select which percpu first chunk allocator to use.
1975 Currently supported values are "embed" and "page".
1976 Archs may support subset or none of the selections.
1977 See comments in mm/percpu.c for details on each
1978 allocator. This parameter is primarily for debugging
1979 and performance comparison.
1981 pf. [PARIDE]
1982 See Documentation/blockdev/paride.txt.
1984 pg. [PARIDE]
1985 See Documentation/blockdev/paride.txt.
1987 pirq= [SMP,APIC] Manual mp-table setup
1988 See Documentation/x86/i386/IO-APIC.txt.
1990 plip= [PPT,NET] Parallel port network link
1991 Format: { parport<nr> | timid | 0 }
1992 See also Documentation/parport.txt.
1994 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1995 Override pmtimer IOPort with a hex value.
1996 e.g. pmtmr=0x508
1998 pnp.debug [PNP]
1999 Enable PNP debug messages. This depends on the
2000 CONFIG_PNP_DEBUG_MESSAGES option.
2002 pnpacpi= [ACPI]
2003 { off }
2005 pnpbios= [ISAPNP]
2006 { on | off | curr | res | no-curr | no-res }
2008 pnp_reserve_irq=
2009 [ISAPNP] Exclude IRQs for the autoconfiguration
2011 pnp_reserve_dma=
2012 [ISAPNP] Exclude DMAs for the autoconfiguration
2014 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2015 Ranges are in pairs (I/O port base and size).
2017 pnp_reserve_mem=
2018 [ISAPNP] Exclude memory regions for the
2019 autoconfiguration.
2020 Ranges are in pairs (memory base and size).
2022 ports= [IP_VS_FTP] IPVS ftp helper module
2023 Default is 21.
2024 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2025 may be specified.
2026 Format: <port>,<port>....
2028 print-fatal-signals=
2029 [KNL] debug: print fatal signals
2030 print-fatal-signals=1: print segfault info to
2031 the kernel console.
2032 default: off.
2034 printk.time= Show timing data prefixed to each printk message line
2035 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2037 processor.max_cstate= [HW,ACPI]
2038 Limit processor to maximum C-state
2039 max_cstate=9 overrides any DMI blacklist limit.
2041 processor.nocst [HW,ACPI]
2042 Ignore the _CST method to determine C-states,
2043 instead using the legacy FADT method
2045 profile= [KNL] Enable kernel profiling via /proc/profile
2046 Format: [schedule,]<number>
2047 Param: "schedule" - profile schedule points.
2048 Param: <number> - step/bucket size as a power of 2 for
2049 statistical time based profiling.
2050 Param: "sleep" - profile D-state sleeping (millisecs).
2051 Requires CONFIG_SCHEDSTATS
2052 Param: "kvm" - profile VM exits.
2054 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2055 before loading.
2056 See Documentation/blockdev/ramdisk.txt.
2058 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2059 probe for; one of (bare|imps|exps|lifebook|any).
2060 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2061 per second.
2062 psmouse.resetafter= [HW,MOUSE]
2063 Try to reset the device after so many bad packets
2064 (0 = never).
2065 psmouse.resolution=
2066 [HW,MOUSE] Set desired mouse resolution, in dpi.
2067 psmouse.smartscroll=
2068 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2069 0 = disabled, 1 = enabled (default).
2071 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2072 Format:
2073 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2075 pt. [PARIDE]
2076 See Documentation/blockdev/paride.txt.
2078 pty.legacy_count=
2079 [KNL] Number of legacy pty's. Overwrites compiled-in
2080 default number.
2082 quiet [KNL] Disable most log messages
2084 r128= [HW,DRM]
2086 raid= [HW,RAID]
2087 See Documentation/md.txt.
2089 ramdisk_blocksize= [RAM]
2090 See Documentation/blockdev/ramdisk.txt.
2092 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2093 See Documentation/blockdev/ramdisk.txt.
2095 rcupdate.blimit= [KNL,BOOT]
2096 Set maximum number of finished RCU callbacks to process
2097 in one batch.
2099 rcupdate.qhimark= [KNL,BOOT]
2100 Set threshold of queued
2101 RCU callbacks over which batch limiting is disabled.
2103 rcupdate.qlowmark= [KNL,BOOT]
2104 Set threshold of queued RCU callbacks below which
2105 batch limiting is re-enabled.
2107 rdinit= [KNL]
2108 Format: <full_path>
2109 Run specified binary instead of /init from the ramdisk,
2110 used for early userspace startup. See initrd.
2112 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2113 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2114 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2116 relax_domain_level=
2117 [KNL, SMP] Set scheduler's default relax_domain_level.
2118 See Documentation/cgroups/cpusets.txt.
2120 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2122 reservetop= [X86-32]
2123 Format: nn[KMG]
2124 Reserves a hole at the top of the kernel virtual
2125 address space.
2127 reset_devices [KNL] Force drivers to reset the underlying device
2128 during initialization.
2130 resume= [SWSUSP]
2131 Specify the partition device for software suspend
2133 resume_offset= [SWSUSP]
2134 Specify the offset from the beginning of the partition
2135 given by "resume=" at which the swap header is located,
2136 in <PAGE_SIZE> units (needed only for swap files).
2137 See Documentation/power/swsusp-and-swap-files.txt
2139 retain_initrd [RAM] Keep initrd memory after extraction
2141 rhash_entries= [KNL,NET]
2142 Set number of hash buckets for route cache
2144 riscom8= [HW,SERIAL]
2145 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2147 ro [KNL] Mount root device read-only on boot
2149 root= [KNL] Root filesystem
2151 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2152 mount the root filesystem
2154 rootflags= [KNL] Set root filesystem mount option string
2156 rootfstype= [KNL] Set root filesystem type
2158 rootwait [KNL] Wait (indefinitely) for root device to show up.
2159 Useful for devices that are detected asynchronously
2160 (e.g. USB and MMC devices).
2162 root_plug.vendor_id=
2163 [ROOTPLUG] Override the default vendor ID
2165 root_plug.product_id=
2166 [ROOTPLUG] Override the default product ID
2168 root_plug.debug=
2169 [ROOTPLUG] Enable debugging output
2171 rw [KNL] Mount root device read-write on boot
2173 S [KNL] Run init in single mode
2175 sa1100ir [NET]
2176 See drivers/net/irda/sa1100_ir.c.
2178 sbni= [NET] Granch SBNI12 leased line adapter
2180 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2181 Format: <io>[,<timeout>[,<isapnp>]]
2183 scsi_debug_*= [SCSI]
2184 See drivers/scsi/scsi_debug.c.
2186 scsi_default_dev_flags=
2187 [SCSI] SCSI default device flags
2188 Format: <integer>
2190 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2191 Format: <vendor>:<model>:<flags>
2192 (flags are integer value)
2194 scsi_logging_level= [SCSI] a bit mask of logging levels
2195 See drivers/scsi/scsi_logging.h for bits. Also
2196 settable via sysctl at dev.scsi.logging_level
2197 (/proc/sys/dev/scsi/logging_level).
2198 There is also a nice 'scsi_logging_level' script in the
2199 S390-tools package, available for download at
2200 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2202 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2203 discovered. async scans them in kernel threads,
2204 allowing boot to proceed. none ignores them, expecting
2205 user space to do the scan.
2207 security= [SECURITY] Choose a security module to enable at boot.
2208 If this boot parameter is not specified, only the first
2209 security module asking for security registration will be
2210 loaded. An invalid security module name will be treated
2211 as if no module has been chosen.
2213 selinux= [SELINUX] Disable or enable SELinux at boot time.
2214 Format: { "0" | "1" }
2215 See security/selinux/Kconfig help text.
2216 0 -- disable.
2217 1 -- enable.
2218 Default value is set via kernel config option.
2219 If enabled at boot time, /selinux/disable can be used
2220 later to disable prior to initial policy load.
2222 serialnumber [BUGS=X86-32]
2224 shapers= [NET]
2225 Maximal number of shapers.
2227 show_msr= [x86] show boot-time MSR settings
2228 Format: { <integer> }
2229 Show boot-time (BIOS-initialized) MSR settings.
2230 The parameter means the number of CPUs to show,
2231 for example 1 means boot CPU only.
2233 sim710= [SCSI,HW]
2234 See header of drivers/scsi/sim710.c.
2236 simeth= [IA-64]
2237 simscsi=
2239 slram= [HW,MTD]
2241 slub_debug[=options[,slabs]] [MM, SLUB]
2242 Enabling slub_debug allows one to determine the
2243 culprit if slab objects become corrupted. Enabling
2244 slub_debug can create guard zones around objects and
2245 may poison objects when not in use. Also tracks the
2246 last alloc / free. For more information see
2247 Documentation/vm/slub.txt.
2249 slub_max_order= [MM, SLUB]
2250 Determines the maximum allowed order for slabs.
2251 A high setting may cause OOMs due to memory
2252 fragmentation. For more information see
2253 Documentation/vm/slub.txt.
2255 slub_min_objects= [MM, SLUB]
2256 The minimum number of objects per slab. SLUB will
2257 increase the slab order up to slub_max_order to
2258 generate a sufficiently large slab able to contain
2259 the number of objects indicated. The higher the number
2260 of objects the smaller the overhead of tracking slabs
2261 and the less frequently locks need to be acquired.
2262 For more information see Documentation/vm/slub.txt.
2264 slub_min_order= [MM, SLUB]
2265 Determines the mininum page order for slabs. Must be
2266 lower than slub_max_order.
2267 For more information see Documentation/vm/slub.txt.
2269 slub_nomerge [MM, SLUB]
2270 Disable merging of slabs with similar size. May be
2271 necessary if there is some reason to distinguish
2272 allocs to different slabs. Debug options disable
2273 merging on their own.
2274 For more information see Documentation/vm/slub.txt.
2276 smart2= [HW]
2277 Format: <io1>[,<io2>[,...,<io8>]]
2279 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2280 attempt to substitute SMP alternatives once at boot.
2282 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2283 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2284 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2285 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2286 smsc-ircc2.ircc_irq= [HW] IRQ line
2287 smsc-ircc2.ircc_dma= [HW] DMA channel
2288 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2289 0: Toshiba Satellite 1800 (GP data pin select)
2290 1: Fast pin select (default)
2291 2: ATC IRMode
2293 snd-ad1816a= [HW,ALSA]
2295 snd-ad1848= [HW,ALSA]
2297 snd-ali5451= [HW,ALSA]
2299 snd-als100= [HW,ALSA]
2301 snd-als4000= [HW,ALSA]
2303 snd-azt2320= [HW,ALSA]
2305 snd-cmi8330= [HW,ALSA]
2307 snd-cmipci= [HW,ALSA]
2309 snd-cs4231= [HW,ALSA]
2311 snd-cs4232= [HW,ALSA]
2313 snd-cs4236= [HW,ALSA]
2315 snd-cs4281= [HW,ALSA]
2317 snd-cs46xx= [HW,ALSA]
2319 snd-dt019x= [HW,ALSA]
2321 snd-dummy= [HW,ALSA]
2323 snd-emu10k1= [HW,ALSA]
2325 snd-ens1370= [HW,ALSA]
2327 snd-ens1371= [HW,ALSA]
2329 snd-es968= [HW,ALSA]
2331 snd-es1688= [HW,ALSA]
2333 snd-es18xx= [HW,ALSA]
2335 snd-es1938= [HW,ALSA]
2337 snd-es1968= [HW,ALSA]
2339 snd-fm801= [HW,ALSA]
2341 snd-gusclassic= [HW,ALSA]
2343 snd-gusextreme= [HW,ALSA]
2345 snd-gusmax= [HW,ALSA]
2347 snd-hdsp= [HW,ALSA]
2349 snd-ice1712= [HW,ALSA]
2351 snd-intel8x0= [HW,ALSA]
2353 snd-interwave= [HW,ALSA]
2355 snd-interwave-stb=
2356 [HW,ALSA]
2358 snd-korg1212= [HW,ALSA]
2360 snd-maestro3= [HW,ALSA]
2362 snd-mpu401= [HW,ALSA]
2364 snd-mtpav= [HW,ALSA]
2366 snd-nm256= [HW,ALSA]
2368 snd-opl3sa2= [HW,ALSA]
2370 snd-opti92x-ad1848=
2371 [HW,ALSA]
2373 snd-opti92x-cs4231=
2374 [HW,ALSA]
2376 snd-opti93x= [HW,ALSA]
2378 snd-pmac= [HW,ALSA]
2380 snd-rme32= [HW,ALSA]
2382 snd-rme96= [HW,ALSA]
2384 snd-rme9652= [HW,ALSA]
2386 snd-sb8= [HW,ALSA]
2388 snd-sb16= [HW,ALSA]
2390 snd-sbawe= [HW,ALSA]
2392 snd-serial= [HW,ALSA]
2394 snd-sgalaxy= [HW,ALSA]
2396 snd-sonicvibes= [HW,ALSA]
2398 snd-sun-amd7930=
2399 [HW,ALSA]
2401 snd-sun-cs4231= [HW,ALSA]
2403 snd-trident= [HW,ALSA]
2405 snd-usb-audio= [HW,ALSA,USB]
2407 snd-via82xx= [HW,ALSA]
2409 snd-virmidi= [HW,ALSA]
2411 snd-wavefront= [HW,ALSA]
2413 snd-ymfpci= [HW,ALSA]
2415 softlockup_panic=
2416 [KNL] Should the soft-lockup detector generate panics.
2418 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2419 See Documentation/sonypi.txt
2421 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2422 See Documentation/serial/specialix.txt.
2424 spia_io_base= [HW,MTD]
2425 spia_fio_base=
2426 spia_pedr=
2427 spia_peddr=
2429 sscape= [HW,OSS]
2430 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2432 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2433 See Documentation/scsi/st.txt.
2435 stacktrace [FTRACE]
2436 Enabled the stack tracer on boot up.
2438 sti= [PARISC,HW]
2439 Format: <num>
2440 Set the STI (builtin display/keyboard on the HP-PARISC
2441 machines) console (graphic card) which should be used
2442 as the initial boot-console.
2443 See also comment in drivers/video/console/sticore.c.
2445 sti_font= [HW]
2446 See comment in drivers/video/console/sticore.c.
2448 stifb= [HW]
2449 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2451 sunrpc.min_resvport=
2452 sunrpc.max_resvport=
2453 [NFS,SUNRPC]
2454 SunRPC servers often require that client requests
2455 originate from a privileged port (i.e. a port in the
2456 range 0 < portnr < 1024).
2457 An administrator who wishes to reserve some of these
2458 ports for other uses may adjust the range that the
2459 kernel's sunrpc client considers to be privileged
2460 using these two parameters to set the minimum and
2461 maximum port values.
2463 sunrpc.pool_mode=
2464 [NFS]
2465 Control how the NFS server code allocates CPUs to
2466 service thread pools. Depending on how many NICs
2467 you have and where their interrupts are bound, this
2468 option will affect which CPUs will do NFS serving.
2469 Note: this parameter cannot be changed while the
2470 NFS server is running.
2472 auto the server chooses an appropriate mode
2473 automatically using heuristics
2474 global a single global pool contains all CPUs
2475 percpu one pool for each CPU
2476 pernode one pool for each NUMA node (equivalent
2477 to global on non-NUMA machines)
2479 sunrpc.tcp_slot_table_entries=
2480 sunrpc.udp_slot_table_entries=
2481 [NFS,SUNRPC]
2482 Sets the upper limit on the number of simultaneous
2483 RPC calls that can be sent from the client to a
2484 server. Increasing these values may allow you to
2485 improve throughput, but will also increase the
2486 amount of memory reserved for use by the client.
2488 swiotlb= [IA-64] Number of I/O TLB slabs
2490 switches= [HW,M68k]
2492 sym53c416= [HW,SCSI]
2493 See header of drivers/scsi/sym53c416.c.
2495 sysrq_always_enabled
2496 [KNL]
2497 Ignore sysrq setting - this boot parameter will
2498 neutralize any effect of /proc/sys/kernel/sysrq.
2499 Useful for debugging.
2501 t128= [HW,SCSI]
2502 See header of drivers/scsi/t128.c.
2504 tdfx= [HW,DRM]
2506 test_suspend= [SUSPEND]
2507 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2508 standby suspend) as the system sleep state to briefly
2509 enter during system startup. The system is woken from
2510 this state using a wakeup-capable RTC alarm.
2512 thash_entries= [KNL,NET]
2513 Set number of hash buckets for TCP connection
2515 thermal.act= [HW,ACPI]
2516 -1: disable all active trip points in all thermal zones
2517 <degrees C>: override all lowest active trip points
2519 thermal.crt= [HW,ACPI]
2520 -1: disable all critical trip points in all thermal zones
2521 <degrees C>: override all critical trip points
2523 thermal.nocrt= [HW,ACPI]
2524 Set to disable actions on ACPI thermal zone
2525 critical and hot trip points.
2527 thermal.off= [HW,ACPI]
2528 1: disable ACPI thermal control
2530 thermal.psv= [HW,ACPI]
2531 -1: disable all passive trip points
2532 <degrees C>: override all passive trip points to this
2533 value
2535 thermal.tzp= [HW,ACPI]
2536 Specify global default ACPI thermal zone polling rate
2537 <deci-seconds>: poll all this frequency
2538 0: no polling (default)
2540 tmscsim= [HW,SCSI]
2541 See comment before function dc390_setup() in
2542 drivers/scsi/tmscsim.c.
2544 topology= [S390]
2545 Format: {off | on}
2546 Specify if the kernel should make use of the cpu
2547 topology informations if the hardware supports these.
2548 The scheduler will make use of these informations and
2549 e.g. base its process migration decisions on it.
2550 Default is off.
2552 tp720= [HW,PS2]
2554 trace_buf_size=nn[KMG]
2555 [FTRACE] will set tracing buffer size.
2557 trace_event=[event-list]
2558 [FTRACE] Set and start specified trace events in order
2559 to facilitate early boot debugging.
2560 See also Documentation/trace/events.txt
2562 trix= [HW,OSS] MediaTrix AudioTrix Pro
2563 Format:
2564 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2566 tsc= Disable clocksource-must-verify flag for TSC.
2567 Format: <string>
2568 [x86] reliable: mark tsc clocksource as reliable, this
2569 disables clocksource verification at runtime.
2570 Used to enable high-resolution timer mode on older
2571 hardware, and in virtualized environment.
2573 turbografx.map[2|3]= [HW,JOY]
2574 TurboGraFX parallel port interface
2575 Format:
2576 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2577 See also Documentation/input/joystick-parport.txt
2579 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2580 See header of drivers/scsi/u14-34f.c.
2582 uart401= [HW,OSS]
2583 Format: <io>,<irq>
2585 uart6850= [HW,OSS]
2586 Format: <io>,<irq>
2588 uhci-hcd.ignore_oc=
2589 [USB] Ignore overcurrent events (default N).
2590 Some badly-designed motherboards generate lots of
2591 bogus events, for ports that aren't wired to
2592 anything. Set this parameter to avoid log spamming.
2593 Note that genuine overcurrent events won't be
2594 reported either.
2596 unknown_nmi_panic
2597 [X86]
2598 Set unknown_nmi_panic=1 early on boot.
2600 usbcore.autosuspend=
2601 [USB] The autosuspend time delay (in seconds) used
2602 for newly-detected USB devices (default 2). This
2603 is the time required before an idle device will be
2604 autosuspended. Devices for which the delay is set
2605 to a negative value won't be autosuspended at all.
2607 usbcore.usbfs_snoop=
2608 [USB] Set to log all usbfs traffic (default 0 = off).
2610 usbcore.blinkenlights=
2611 [USB] Set to cycle leds on hubs (default 0 = off).
2613 usbcore.old_scheme_first=
2614 [USB] Start with the old device initialization
2615 scheme (default 0 = off).
2617 usbcore.use_both_schemes=
2618 [USB] Try the other device initialization scheme
2619 if the first one fails (default 1 = enabled).
2621 usbcore.initial_descriptor_timeout=
2622 [USB] Specifies timeout for the initial 64-byte
2623 USB_REQ_GET_DESCRIPTOR request in milliseconds
2624 (default 5000 = 5.0 seconds).
2626 usbhid.mousepoll=
2627 [USBHID] The interval which mice are to be polled at.
2629 usb-storage.delay_use=
2630 [UMS] The delay in seconds before a new device is
2631 scanned for Logical Units (default 5).
2633 usb-storage.quirks=
2634 [UMS] A list of quirks entries to supplement or
2635 override the built-in unusual_devs list. List
2636 entries are separated by commas. Each entry has
2637 the form VID:PID:Flags where VID and PID are Vendor
2638 and Product ID values (4-digit hex numbers) and
2639 Flags is a set of characters, each corresponding
2640 to a common usb-storage quirk flag as follows:
2641 a = SANE_SENSE (collect more than 18 bytes
2642 of sense data);
2643 c = FIX_CAPACITY (decrease the reported
2644 device capacity by one sector);
2645 h = CAPACITY_HEURISTICS (decrease the
2646 reported device capacity by one
2647 sector if the number is odd);
2648 i = IGNORE_DEVICE (don't bind to this
2649 device);
2650 l = NOT_LOCKABLE (don't try to lock and
2651 unlock ejectable media);
2652 m = MAX_SECTORS_64 (don't transfer more
2653 than 64 sectors = 32 KB at a time);
2654 o = CAPACITY_OK (accept the capacity
2655 reported by the device);
2656 r = IGNORE_RESIDUE (the device reports
2657 bogus residue values);
2658 s = SINGLE_LUN (the device has only one
2659 Logical Unit);
2660 w = NO_WP_DETECT (don't test whether the
2661 medium is write-protected).
2662 Example: quirks=0419:aaf5:rl,0421:0433:rc
2664 vdso= [X86,SH]
2665 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2666 vdso=1: enable VDSO (default)
2667 vdso=0: disable VDSO mapping
2669 vdso32= [X86]
2670 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2671 vdso32=1: enable 32-bit VDSO (default)
2672 vdso32=0: disable 32-bit VDSO mapping
2674 vector= [IA-64,SMP]
2675 vector=percpu: enable percpu vector domain
2677 video= [FB] Frame buffer configuration
2678 See Documentation/fb/modedb.txt.
2680 vga= [BOOT,X86-32] Select a particular video mode
2681 See Documentation/x86/boot.txt and
2682 Documentation/svga.txt.
2683 Use vga=ask for menu.
2684 This is actually a boot loader parameter; the value is
2685 passed to the kernel using a special protocol.
2687 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2688 size of <nn>. This can be used to increase the
2689 minimum size (128MB on x86). It can also be used to
2690 decrease the size and leave more room for directly
2691 mapped kernel RAM.
2693 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2694 Format: <command>
2696 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2697 Format: <command>
2699 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2700 Format: <command>
2702 vt.default_blu= [VT]
2703 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2704 Change the default blue palette of the console.
2705 This is a 16-member array composed of values
2706 ranging from 0-255.
2708 vt.default_grn= [VT]
2709 Format: <green0>,<green1>,<green2>,...,<green15>
2710 Change the default green palette of the console.
2711 This is a 16-member array composed of values
2712 ranging from 0-255.
2714 vt.default_red= [VT]
2715 Format: <red0>,<red1>,<red2>,...,<red15>
2716 Change the default red palette of the console.
2717 This is a 16-member array composed of values
2718 ranging from 0-255.
2720 vt.default_utf8=
2721 [VT]
2722 Format=<0|1>
2723 Set system-wide default UTF-8 mode for all tty's.
2724 Default is 1, i.e. UTF-8 mode is enabled for all
2725 newly opened terminals.
2727 waveartist= [HW,OSS]
2728 Format: <io>,<irq>,<dma>,<dma2>
2730 wd33c93= [HW,SCSI]
2731 See header of drivers/scsi/wd33c93.c.
2733 wd7000= [HW,SCSI]
2734 See header of drivers/scsi/wd7000.c.
2736 wdt= [WDT] Watchdog
2737 See Documentation/watchdog/wdt.txt.
2739 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2740 default x2apic cluster mode on platforms
2741 supporting x2apic.
2743 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2744 xd_geo= See header of drivers/block/xd.c.
2746 xirc2ps_cs= [NET,PCMCIA]
2747 Format:
2748 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2750 ______________________________________________________________________
2752 TODO:
2754 Add documentation for ALSA options.
2755 Add more DRM drivers.