| blob | e4cbca58536c9f3ab4236f4db78eb22cacc993af |
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 IPV6 IPv6 support is enabled.
58 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
61 KVM Kernel Virtual Machine support is enabled.
62 LIBATA Libata driver is enabled
63 LP Printer support is enabled.
64 LOOP Loopback device support is enabled.
65 M68k M68k architecture is enabled.
66 These options have more detailed description inside of
67 Documentation/m68k/kernel-options.txt.
68 MCA MCA bus support is enabled.
69 MDA MDA console support is enabled.
70 MOUSE Appropriate mouse support is enabled.
71 MSI Message Signaled Interrupts (PCI).
72 MTD MTD (Memory Technology Device) support is enabled.
73 NET Appropriate network support is enabled.
74 NUMA NUMA support is enabled.
75 GENERIC_TIME The generic timeofday code is enabled.
76 NFS Appropriate NFS support is enabled.
77 OSS OSS sound support is enabled.
78 PV_OPS A paravirtualized kernel is enabled.
79 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
80 PARISC The PA-RISC architecture is enabled.
81 PCI PCI bus support is enabled.
82 PCIE PCI Express support is enabled.
83 PCMCIA The PCMCIA subsystem is enabled.
84 PNP Plug & Play support is enabled.
85 PPC PowerPC architecture is enabled.
86 PPT Parallel port support is enabled.
87 PS2 Appropriate PS/2 support is enabled.
88 RAM RAM disk support is enabled.
89 S390 S390 architecture is enabled.
90 SCSI Appropriate SCSI support is enabled.
91 A lot of drivers has their options described inside of
92 Documentation/scsi/.
93 SECURITY Different security models are enabled.
94 SELINUX SELinux support is enabled.
95 SERIAL Serial support is enabled.
96 SH SuperH architecture is enabled.
97 SMP The kernel is an SMP kernel.
98 SPARC Sparc architecture is enabled.
99 SWSUSP Software suspend (hibernation) is enabled.
100 SUSPEND System suspend states are enabled.
101 FTRACE Function tracing enabled.
102 TS Appropriate touchscreen support is enabled.
103 UMS USB Mass Storage support is enabled.
104 USB USB support is enabled.
105 USBHID USB Human Interface Device support is enabled.
106 V4L Video For Linux support is enabled.
107 VGA The VGA console has been enabled.
108 VT Virtual terminal support is enabled.
109 WDT Watchdog support is enabled.
110 XT IBM PC/XT MFM hard disk support is enabled.
111 X86-32 X86-32, aka i386 architecture is enabled.
112 X86-64 X86-64 architecture is enabled.
113 More X86-64 boot options can be found in
114 Documentation/x86/x86_64/boot-options.txt .
115 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
117 In addition, the following text indicates that the option:
119 BUGS= Relates to possible processor bugs on the said processor.
120 KNL Is a kernel start-up parameter.
121 BOOT Is a boot loader parameter.
123 Parameters denoted with BOOT are actually interpreted by the boot
124 loader, and have no meaning to the kernel directly.
125 Do not modify the syntax of boot loader parameters without extreme
126 need or coordination with <Documentation/x86/boot.txt>.
128 There are also arch-specific kernel-parameters not documented here.
129 See for example <Documentation/x86/x86_64/boot-options.txt>.
131 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
132 a trailing = on the name of any parameter states that that parameter will
133 be entered as an environment variable, whereas its absence indicates that
134 it will appear as a kernel argument readable via /proc/cmdline by programs
135 running once the system is up.
137 The number of kernel parameters is not limited, but the length of the
138 complete command line (parameters including spaces etc.) is limited to
139 a fixed number of characters. This limit depends on the architecture
140 and is between 256 and 4096 characters. It is defined in the file
141 ./include/asm/setup.h as COMMAND_LINE_SIZE.
144 acpi= [HW,ACPI,X86]
145 Advanced Configuration and Power Interface
146 Format: { force | off | ht | strict | noirq | rsdt }
147 force -- enable ACPI if default was off
148 off -- disable ACPI if default was on
149 noirq -- do not use ACPI for IRQ routing
150 ht -- run only enough ACPI to enable Hyper Threading
151 strict -- Be less tolerant of platforms that are not
152 strictly ACPI specification compliant.
153 rsdt -- prefer RSDT over (default) XSDT
155 See also Documentation/power/pm.txt, pci=noacpi
157 acpi_apic_instance= [ACPI, IOAPIC]
158 Format: <int>
159 2: use 2nd APIC table, if available
160 1,0: use 1st APIC table
161 default: 0
163 acpi_backlight= [HW,ACPI]
164 acpi_backlight=vendor
165 acpi_backlight=video
166 If set to vendor, prefer vendor specific driver
167 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
168 of the ACPI video.ko driver.
170 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
171 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
172 Format: <int>
173 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
174 debug output. Bits in debug_layer correspond to a
175 _COMPONENT in an ACPI source file, e.g.,
176 #define _COMPONENT ACPI_PCI_COMPONENT
177 Bits in debug_level correspond to a level in
178 ACPI_DEBUG_PRINT statements, e.g.,
179 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
180 The debug_level mask defaults to "info". See
181 Documentation/acpi/debug.txt for more information about
182 debug layers and levels.
184 Enable processor driver info messages:
185 acpi.debug_layer=0x20000000
186 Enable PCI/PCI interrupt routing info messages:
187 acpi.debug_layer=0x400000
188 Enable AML "Debug" output, i.e., stores to the Debug
189 object while interpreting AML:
190 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
191 Enable all messages related to ACPI hardware:
192 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
194 Some values produce so much output that the system is
195 unusable. The "log_buf_len" parameter may be useful
196 if you need to capture more output.
198 acpi_display_output= [HW,ACPI]
199 acpi_display_output=vendor
200 acpi_display_output=video
201 See above.
203 acpi_irq_balance [HW,ACPI]
204 ACPI will balance active IRQs
205 default in APIC mode
207 acpi_irq_nobalance [HW,ACPI]
208 ACPI will not move active IRQs (default)
209 default in PIC mode
211 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
212 Format: <irq>,<irq>...
214 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
215 use by PCI
216 Format: <irq>,<irq>...
218 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
220 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
221 Format: To spoof as Windows 98: ="Microsoft Windows"
223 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
224 acpi_osi="string1" # add string1 -- only one string
225 acpi_osi="!string2" # remove built-in string2
226 acpi_osi= # disable all strings
228 acpi_pm_good [X86]
229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
233 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
234 Format: { level | edge | high | low }
236 acpi_serialize [HW,ACPI] force serialization of AML methods
238 acpi_skip_timer_override [HW,ACPI]
239 Recognize and ignore IRQ0/pin2 Interrupt Override.
240 For broken nForce2 BIOS resulting in XT-PIC timer.
242 acpi_sleep= [HW,ACPI] Sleep options
243 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
244 old_ordering, s4_nonvs, sci_force_enable }
245 See Documentation/power/video.txt for information on
246 s3_bios and s3_mode.
247 s3_beep is for debugging; it makes the PC's speaker beep
248 as soon as the kernel's real-mode entry point is called.
249 s4_nohwsig prevents ACPI hardware signature from being
250 used during resume from hibernation.
251 old_ordering causes the ACPI 1.0 ordering of the _PTS
252 control method, with respect to putting devices into
253 low power states, to be enforced (the ACPI 2.0 ordering
254 of _PTS is used by default).
255 s4_nonvs prevents the kernel from saving/restoring the
256 ACPI NVS memory during hibernation.
257 sci_force_enable causes the kernel to set SCI_EN directly
258 on resume from S1/S3 (which is against the ACPI spec,
259 but some broken systems don't work without it).
261 acpi_use_timer_override [HW,ACPI]
262 Use timer override. For some broken Nvidia NF5 boards
263 that require a timer override, but don't have HPET
265 acpi_enforce_resources= [ACPI]
266 { strict | lax | no }
267 Check for resource conflicts between native drivers
268 and ACPI OperationRegions (SystemIO and SystemMemory
269 only). IO ports and memory declared in ACPI might be
270 used by the ACPI subsystem in arbitrary AML code and
271 can interfere with legacy drivers.
272 strict (default): access to resources claimed by ACPI
273 is denied; legacy drivers trying to access reserved
274 resources will fail to bind to device using them.
275 lax: access to resources claimed by ACPI is allowed;
276 legacy drivers trying to access reserved resources
277 will bind successfully but a warning message is logged.
278 no: ACPI OperationRegions are not marked as reserved,
279 no further checks are performed.
281 ad1848= [HW,OSS]
282 Format: <io>,<irq>,<dma>,<dma2>,<type>
284 add_efi_memmap [EFI; X86] Include EFI memory map in
285 kernel's map of available physical RAM.
287 advansys= [HW,SCSI]
288 See header of drivers/scsi/advansys.c.
290 advwdt= [HW,WDT] Advantech WDT
291 Format: <iostart>,<iostop>
293 aedsp16= [HW,OSS] Audio Excel DSP 16
294 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
295 See also header of sound/oss/aedsp16.c.
297 agp= [AGP]
298 { off | try_unsupported }
299 off: disable AGP support
300 try_unsupported: try to drive unsupported chipsets
301 (may crash computer or cause data corruption)
303 aha152x= [HW,SCSI]
304 See Documentation/scsi/aha152x.txt.
306 aha1542= [HW,SCSI]
307 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
309 aic7xxx= [HW,SCSI]
310 See Documentation/scsi/aic7xxx.txt.
312 aic79xx= [HW,SCSI]
313 See Documentation/scsi/aic79xx.txt.
315 alignment= [KNL,ARM]
316 Allow the default userspace alignment fault handler
317 behaviour to be specified. Bit 0 enables warnings,
318 bit 1 enables fixups, and bit 2 sends a segfault.
320 amd_iommu= [HW,X86-84]
321 Pass parameters to the AMD IOMMU driver in the system.
322 Possible values are:
323 isolate - enable device isolation (each device, as far
324 as possible, will get its own protection
325 domain) [default]
326 share - put every device behind one IOMMU into the
327 same protection domain
328 fullflush - enable flushing of IO/TLB entries when
329 they are unmapped. Otherwise they are
330 flushed before they will be reused, which
331 is a lot of faster
333 amijoy.map= [HW,JOY] Amiga joystick support
334 Map of devices attached to JOY0DAT and JOY1DAT
335 Format: <a>,<b>
336 See also Documentation/kernel/input/joystick.txt
338 analog.map= [HW,JOY] Analog joystick and gamepad support
339 Specifies type or capabilities of an analog joystick
340 connected to one of 16 gameports
341 Format: <type1>,<type2>,..<type16>
343 apc= [HW,SPARC]
344 Power management functions (SPARCstation-4/5 + deriv.)
345 Format: noidle
346 Disable APC CPU standby support. SPARCstation-Fox does
347 not play well with APC CPU idle - disable it if you have
348 APC and your system crashes randomly.
350 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
351 Change the output verbosity whilst booting
352 Format: { quiet (default) | verbose | debug }
353 Change the amount of debugging information output
354 when initialising the APIC and IO-APIC components.
356 autoconf= [IPV6]
357 See Documentation/networking/ipv6.txt.
359 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
360 Limit apic dumping. The parameter defines the maximal
361 number of local apics being dumped. Also it is possible
362 to set it to "all" by meaning -- no limit here.
363 Format: { 1 (default) | 2 | ... | all }.
364 The parameter valid if only apic=debug or
365 apic=verbose is specified.
366 Example: apic=debug show_lapic=all
368 apm= [APM] Advanced Power Management
369 See header of arch/x86/kernel/apm_32.c.
371 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
372 Format: <io>,<irq>,<nodeID>
374 ataflop= [HW,M68k]
376 atarimouse= [HW,MOUSE] Atari Mouse
378 atascsi= [HW,SCSI] Atari SCSI
380 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
381 EzKey and similar keyboards
383 atkbd.reset= [HW] Reset keyboard during initialization
385 atkbd.set= [HW] Select keyboard code set
386 Format: <int> (2 = AT (default), 3 = PS/2)
388 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
389 keyboards
391 atkbd.softraw= [HW] Choose between synthetic and real raw mode
392 Format: <bool> (0 = real, 1 = synthetic (default))
394 atkbd.softrepeat= [HW]
395 Use software keyboard repeat
397 autotest [IA64]
399 baycom_epp= [HW,AX25]
400 Format: <io>,<mode>
402 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
403 Format: <io>,<mode>
404 See header of drivers/net/hamradio/baycom_par.c.
406 baycom_ser_fdx= [HW,AX25]
407 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
408 Format: <io>,<irq>,<mode>[,<baud>]
409 See header of drivers/net/hamradio/baycom_ser_fdx.c.
411 baycom_ser_hdx= [HW,AX25]
412 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
413 Format: <io>,<irq>,<mode>
414 See header of drivers/net/hamradio/baycom_ser_hdx.c.
416 boot_delay= Milliseconds to delay each printk during boot.
417 Values larger than 10 seconds (10000) are changed to
418 no delay (0).
419 Format: integer
421 bootmem_debug [KNL] Enable bootmem allocator debug messages.
423 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
424 bttv.radio= Most important insmod options are available as
425 kernel args too.
426 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
427 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
429 BusLogic= [HW,SCSI]
430 See drivers/scsi/BusLogic.c, comment before function
431 BusLogic_ParseDriverOptions().
433 c101= [NET] Moxa C101 synchronous serial card
435 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
436 Sometimes CPU hardware bugs make them report the cache
437 size incorrectly. The kernel will attempt work arounds
438 to fix known problems, but for some CPUs it is not
439 possible to determine what the correct size should be.
440 This option provides an override for these situations.
442 capability.disable=
443 [SECURITY] Disable capabilities. This would normally
444 be used only if an alternative security model is to be
445 configured. Potentially dangerous and should only be
446 used if you are entirely sure of the consequences.
448 ccw_timeout_log [S390]
449 See Documentation/s390/CommonIO for details.
451 cgroup_disable= [KNL] Disable a particular controller
452 Format: {name of the controller(s) to disable}
453 {Currently supported controllers - "memory"}
455 checkreqprot [SELINUX] Set initial checkreqprot flag value.
456 Format: { "0" | "1" }
457 See security/selinux/Kconfig help text.
458 0 -- check protection applied by kernel (includes
459 any implied execute protection).
460 1 -- check protection requested by application.
461 Default value is set via a kernel config option.
462 Value can be changed at runtime via
463 /selinux/checkreqprot.
465 cio_ignore= [S390]
466 See Documentation/s390/CommonIO for details.
468 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
469 [Deprecated]
470 Forces specified clocksource (if available) to be used
471 when calculating gettimeofday(). If specified
472 clocksource is not available, it defaults to PIT.
473 Format: { pit | tsc | cyclone | pmtmr }
475 clocksource= [GENERIC_TIME] Override the default clocksource
476 Format: <string>
477 Override the default clocksource and use the clocksource
478 with the name specified.
479 Some clocksource names to choose from, depending on
480 the platform:
481 [all] jiffies (this is the base, fallback clocksource)
482 [ACPI] acpi_pm
483 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
484 pxa_timer,timer3,32k_counter,timer0_1
485 [AVR32] avr32
486 [X86-32] pit,hpet,tsc,vmi-timer;
487 scx200_hrt on Geode; cyclone on IBM x440
488 [MIPS] MIPS
489 [PARISC] cr16
490 [S390] tod
491 [SH] SuperH
492 [SPARC64] tick
493 [X86-64] hpet,tsc
495 clearcpuid=BITNUM [X86]
496 Disable CPUID feature X for the kernel. See
497 arch/x86/include/asm/cpufeature.h for the valid bit
498 numbers. Note the Linux specific bits are not necessarily
499 stable over kernel options, but the vendor specific
500 ones should be.
501 Also note that user programs calling CPUID directly
502 or using the feature without checking anything
503 will still see it. This just prevents it from
504 being used by the kernel or shown in /proc/cpuinfo.
505 Also note the kernel might malfunction if you disable
506 some critical bits.
508 cmo_free_hint= [PPC] Format: { yes | no }
509 Specify whether pages are marked as being inactive
510 when they are freed. This is used in CMO environments
511 to determine OS memory pressure for page stealing by
512 a hypervisor.
513 Default: yes
515 code_bytes [X86] How many bytes of object code to print
516 in an oops report.
517 Range: 0 - 8192
518 Default: 64
520 com20020= [HW,NET] ARCnet - COM20020 chipset
521 Format:
522 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
524 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
525 Format: <io>[,<irq>]
527 com90xx= [HW,NET]
528 ARCnet - COM90xx chipset (memory-mapped buffers)
529 Format: <io>[,<irq>[,<memstart>]]
531 condev= [HW,S390] console device
532 conmode=
534 console= [KNL] Output console device and options.
536 tty<n> Use the virtual console device <n>.
538 ttyS<n>[,options]
539 ttyUSB0[,options]
540 Use the specified serial port. The options are of
541 the form "bbbbpnf", where "bbbb" is the baud rate,
542 "p" is parity ("n", "o", or "e"), "n" is number of
543 bits, and "f" is flow control ("r" for RTS or
544 omit it). Default is "9600n8".
546 See Documentation/serial-console.txt for more
547 information. See
548 Documentation/networking/netconsole.txt for an
549 alternative.
551 uart[8250],io,<addr>[,options]
552 uart[8250],mmio,<addr>[,options]
553 Start an early, polled-mode console on the 8250/16550
554 UART at the specified I/O port or MMIO address,
555 switching to the matching ttyS device later. The
556 options are the same as for ttyS, above.
558 If the device connected to the port is not a TTY but a braille
559 device, prepend "brl," before the device type, for instance
560 console=brl,ttyS0
561 For now, only VisioBraille is supported.
563 consoleblank= [KNL] The console blank (screen saver) timeout in
564 seconds. Defaults to 10*60 = 10mins. A value of 0
565 disables the blank timer.
567 coredump_filter=
568 [KNL] Change the default value for
569 /proc/<pid>/coredump_filter.
570 See also Documentation/filesystems/proc.txt.
572 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
573 Format:
574 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
576 crashkernel=nn[KMG]@ss[KMG]
577 [KNL] Reserve a chunk of physical memory to
578 hold a kernel to switch to with kexec on panic.
580 crashkernel=range1:size1[,range2:size2,...][@offset]
581 [KNL] Same as above, but depends on the memory
582 in the running system. The syntax of range is
583 start-[end] where start and end are both
584 a memory unit (amount[KMG]). See also
585 Documentation/kdump/kdump.txt for a example.
587 cs89x0_dma= [HW,NET]
588 Format: <dma>
590 cs89x0_media= [HW,NET]
591 Format: { rj45 | aui | bnc }
593 dasd= [HW,NET]
594 See header of drivers/s390/block/dasd_devmap.c.
596 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
597 (one device per port)
598 Format: <port#>,<type>
599 See also Documentation/input/joystick-parport.txt
601 debug [KNL] Enable kernel debugging (events log level).
603 debug_locks_verbose=
604 [KNL] verbose self-tests
605 Format=<0|1>
606 Print debugging info while doing the locking API
607 self-tests.
608 We default to 0 (no extra messages), setting it to
609 1 will print _a lot_ more information - normally
610 only useful to kernel developers.
612 debug_objects [KNL] Enable object debugging
614 no_debug_objects
615 [KNL] Disable object debugging
617 debugpat [X86] Enable PAT debugging
619 decnet.addr= [HW,NET]
620 Format: <area>[,<node>]
621 See also Documentation/networking/decnet.txt.
623 default_hugepagesz=
624 [same as hugepagesz=] The size of the default
625 HugeTLB page size. This is the size represented by
626 the legacy /proc/ hugepages APIs, used for SHM, and
627 default size when mounting hugetlbfs filesystems.
628 Defaults to the default architecture's huge page size
629 if not specified.
631 dhash_entries= [KNL]
632 Set number of hash buckets for dentry cache.
634 digi= [HW,SERIAL]
635 IO parameters + enable/disable command.
637 digiepca= [HW,SERIAL]
638 See drivers/char/README.epca and
639 Documentation/serial/digiepca.txt.
641 disable= [IPV6]
642 See Documentation/networking/ipv6.txt.
644 disable_ipv6= [IPV6]
645 See Documentation/networking/ipv6.txt.
647 disable_mtrr_cleanup [X86]
648 The kernel tries to adjust MTRR layout from continuous
649 to discrete, to make X server driver able to add WB
650 entry later. This parameter disables that.
652 disable_mtrr_trim [X86, Intel and AMD only]
653 By default the kernel will trim any uncacheable
654 memory out of your available memory pool based on
655 MTRR settings. This parameter disables that behavior,
656 possibly causing your machine to run very slowly.
658 disable_timer_pin_1 [X86]
659 Disable PIN 1 of APIC timer
660 Can be useful to work around chipset bugs.
662 dmasound= [HW,OSS] Sound subsystem buffers
664 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
665 this option disables the debugging code at boot.
667 dma_debug_entries=<number>
668 This option allows to tune the number of preallocated
669 entries for DMA-API debugging code. One entry is
670 required per DMA-API allocation. Use this if the
671 DMA-API debugging code disables itself because the
672 architectural default is too low.
674 dma_debug_driver=<driver_name>
675 With this option the DMA-API debugging driver
676 filter feature can be enabled at boot time. Just
677 pass the driver to filter for as the parameter.
678 The filter can be disabled or changed to another
679 driver later using sysfs.
681 dscc4.setup= [NET]
683 dtc3181e= [HW,SCSI]
685 dynamic_printk Enables pr_debug()/dev_dbg() calls if
686 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
687 These can also be switched on/off via
688 <debugfs>/dynamic_printk/modules
690 earlycon= [KNL] Output early console device and options.
691 uart[8250],io,<addr>[,options]
692 uart[8250],mmio,<addr>[,options]
693 Start an early, polled-mode console on the 8250/16550
694 UART at the specified I/O port or MMIO address.
695 The options are the same as for ttyS, above.
697 earlyprintk= [X86,SH,BLACKFIN]
698 earlyprintk=vga
699 earlyprintk=serial[,ttySn[,baudrate]]
700 earlyprintk=ttySn[,baudrate]
701 earlyprintk=dbgp[debugController#]
703 Append ",keep" to not disable it when the real console
704 takes over.
706 Only vga or serial or usb debug port at a time.
708 Currently only ttyS0 and ttyS1 are supported.
710 Interaction with the standard serial driver is not
711 very good.
713 The VGA output is eventually overwritten by the real
714 console.
716 eata= [HW,SCSI]
718 edd= [EDD]
719 Format: {"off" | "on" | "skip[mbr]"}
721 eisa_irq_edge= [PARISC,HW]
722 See header of drivers/parisc/eisa.c.
724 elanfreq= [X86-32]
725 See comment before function elanfreq_setup() in
726 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
728 elevator= [IOSCHED]
729 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
730 See Documentation/block/as-iosched.txt and
731 Documentation/block/deadline-iosched.txt for details.
733 elfcorehdr= [IA64,PPC,SH,X86]
734 Specifies physical address of start of kernel core
735 image elf header. Generally kexec loader will
736 pass this option to capture kernel.
737 See Documentation/kdump/kdump.txt for details.
739 enable_mtrr_cleanup [X86]
740 The kernel tries to adjust MTRR layout from continuous
741 to discrete, to make X server driver able to add WB
742 entry later. This parameter enables that.
744 enable_timer_pin_1 [X86]
745 Enable PIN 1 of APIC timer
746 Can be useful to work around chipset bugs
747 (in particular on some ATI chipsets).
748 The kernel tries to set a reasonable default.
750 enforcing [SELINUX] Set initial enforcing status.
751 Format: {"0" | "1"}
752 See security/selinux/Kconfig help text.
753 0 -- permissive (log only, no denials).
754 1 -- enforcing (deny and log).
755 Default value is 0.
756 Value can be changed at runtime via /selinux/enforce.
758 ether= [HW,NET] Ethernet cards parameters
759 This option is obsoleted by the "netdev=" option, which
760 has equivalent usage. See its documentation for details.
762 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
763 Format: <io>[,<irq>]
765 failslab=
766 fail_page_alloc=
767 fail_make_request=[KNL]
768 General fault injection mechanism.
769 Format: <interval>,<probability>,<space>,<times>
770 See also /Documentation/fault-injection/.
772 fd_mcs= [HW,SCSI]
773 See header of drivers/scsi/fd_mcs.c.
775 fdomain= [HW,SCSI]
776 See header of drivers/scsi/fdomain.c.
778 floppy= [HW]
779 See Documentation/blockdev/floppy.txt.
781 force_pal_cache_flush
782 [IA-64] Avoid check_sal_cache_flush which may hang on
783 buggy SAL_CACHE_FLUSH implementations. Using this
784 parameter will force ia64_sal_cache_flush to call
785 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
787 ftrace=[tracer]
788 [FTRACE] will set and start the specified tracer
789 as early as possible in order to facilitate early
790 boot debugging.
792 ftrace_dump_on_oops
793 [FTRACE] will dump the trace buffers on oops.
795 ftrace_filter=[function-list]
796 [FTRACE] Limit the functions traced by the function
797 tracer at boot up. function-list is a comma separated
798 list of functions. This list can be changed at run
799 time by the set_ftrace_filter file in the debugfs
800 tracing directory.
802 ftrace_notrace=[function-list]
803 [FTRACE] Do not trace the functions specified in
804 function-list. This list can be changed at run time
805 by the set_ftrace_notrace file in the debugfs
806 tracing directory.
808 ftrace_graph_filter=[function-list]
809 [FTRACE] Limit the top level callers functions traced
810 by the function graph tracer at boot up.
811 function-list is a comma separated list of functions
812 that can be changed at run time by the
813 set_graph_function file in the debugfs tracing directory.
815 gamecon.map[2|3]=
816 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
817 support via parallel port (up to 5 devices per port)
818 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
819 See also Documentation/input/joystick-parport.txt
821 gamma= [HW,DRM]
823 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
824 Format: off | on
825 default: on
827 gcov_persist= [GCOV] When non-zero (default), profiling data for
828 kernel modules is saved and remains accessible via
829 debugfs, even when the module is unloaded/reloaded.
830 When zero, profiling data is discarded and associated
831 debugfs files are removed at module unload time.
833 gdth= [HW,SCSI]
834 See header of drivers/scsi/gdth.c.
836 gpt [EFI] Forces disk with valid GPT signature but
837 invalid Protective MBR to be treated as GPT.
839 gvp11= [HW,SCSI]
841 hashdist= [KNL,NUMA] Large hashes allocated during boot
842 are distributed across NUMA nodes. Defaults on
843 for 64bit NUMA, off otherwise.
844 Format: 0 | 1 (for off | on)
846 hcl= [IA-64] SGI's Hardware Graph compatibility layer
848 hd= [EIDE] (E)IDE hard drive subsystem geometry
849 Format: <cyl>,<head>,<sect>
851 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
852 size of <nn>. This works even on boxes that have no
853 highmem otherwise. This also works to reduce highmem
854 size on bigger boxes.
856 highres= [KNL] Enable/disable high resolution timer mode.
857 Valid parameters: "on", "off"
858 Default: "on"
860 hisax= [HW,ISDN]
861 See Documentation/isdn/README.HiSax.
863 hlt [BUGS=ARM,SH]
865 hpet= [X86-32,HPET] option to control HPET usage
866 Format: { enable (default) | disable | force |
867 verbose }
868 disable: disable HPET and use PIT instead
869 force: allow force enabled of undocumented chips (ICH4,
870 VIA, nVidia)
871 verbose: show contents of HPET registers during setup
873 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
874 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
875 On x86-64 and powerpc, this option can be specified
876 multiple times interleaved with hugepages= to reserve
877 huge pages of different sizes. Valid pages sizes on
878 x86-64 are 2M (when the CPU supports "pse") and 1G
879 (when the CPU supports the "pdpe1gb" cpuinfo flag)
880 Note that 1GB pages can only be allocated at boot time
881 using hugepages= and not freed afterwards.
883 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
884 terminal devices. Valid values: 0..8
885 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
886 If specified, z/VM IUCV HVC accepts connections
887 from listed z/VM user IDs only.
889 i2c_bus= [HW] Override the default board specific I2C bus speed
890 or register an additional I2C bus that is not
891 registered from board initialization code.
892 Format:
893 <bus_id>,<clkrate>
895 i8042.debug [HW] Toggle i8042 debug mode
896 i8042.direct [HW] Put keyboard port into non-translated mode
897 i8042.dumbkbd [HW] Pretend that controller can only read data from
898 keyboard and cannot control its state
899 (Don't attempt to blink the leds)
900 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
901 i8042.nokbd [HW] Don't check/create keyboard port
902 i8042.noloop [HW] Disable the AUX Loopback command while probing
903 for the AUX port
904 i8042.nomux [HW] Don't check presence of an active multiplexing
905 controller
906 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
907 controllers
908 i8042.panicblink=
909 [HW] Frequency with which keyboard LEDs should blink
910 when kernel panics (default is 0.5 sec)
911 i8042.reset [HW] Reset the controller during init and cleanup
912 i8042.unlock [HW] Unlock (ignore) the keylock
914 i810= [HW,DRM]
916 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
917 indicates that the driver is running on unsupported
918 hardware.
919 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
920 does not match list of supported models.
921 i8k.power_status
922 [HW] Report power status in /proc/i8k
923 (disabled by default)
924 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
925 capability is set.
927 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
928 See Documentation/mca.txt.
930 icn= [HW,ISDN]
931 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
933 ide-core.nodma= [HW] (E)IDE subsystem
934 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
935 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
936 .cdrom .chs .ignore_cable are additional options
937 See Documentation/ide/ide.txt.
939 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
940 Claim all unknown PCI IDE storage controllers.
942 idle= [X86]
943 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
944 Poll forces a polling idle loop that can slightly
945 improve the performance of waking up a idle CPU, but
946 will use a lot of power and make the system run hot.
947 Not recommended.
948 idle=mwait: On systems which support MONITOR/MWAIT but
949 the kernel chose to not use it because it doesn't save
950 as much power as a normal idle loop, use the
951 MONITOR/MWAIT idle loop anyways. Performance should be
952 the same as idle=poll.
953 idle=halt: Halt is forced to be used for CPU idle.
954 In such case C2/C3 won't be used again.
955 idle=nomwait: Disable mwait for CPU C-states
957 ignore_loglevel [KNL]
958 Ignore loglevel setting - this will print /all/
959 kernel messages to the console. Useful for debugging.
961 ihash_entries= [KNL]
962 Set number of hash buckets for inode cache.
964 ima_audit= [IMA]
965 Format: { "0" | "1" }
966 0 -- integrity auditing messages. (Default)
967 1 -- enable informational integrity auditing messages.
969 ima_hash= [IMA]
970 Format: { "sha1" | "md5" }
971 default: "sha1"
973 ima_tcb [IMA]
974 Load a policy which meets the needs of the Trusted
975 Computing Base. This means IMA will measure all
976 programs exec'd, files mmap'd for exec, and all files
977 opened for read by uid=0.
979 in2000= [HW,SCSI]
980 See header of drivers/scsi/in2000.c.
982 init= [KNL]
983 Format: <full_path>
984 Run specified binary instead of /sbin/init as init
985 process.
987 initcall_debug [KNL] Trace initcalls as they are executed. Useful
988 for working out where the kernel is dying during
989 startup.
991 initrd= [BOOT] Specify the location of the initial ramdisk
993 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
994 Format: <irq>
996 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
997 on
998 Enable intel iommu driver.
999 off
1000 Disable intel iommu driver.
1001 igfx_off [Default Off]
1002 By default, gfx is mapped as normal device. If a gfx
1003 device has a dedicated DMAR unit, the DMAR unit is
1004 bypassed by not enabling DMAR with this option. In
1005 this case, gfx device will use physical address for
1006 DMA.
1007 forcedac [x86_64]
1008 With this option iommu will not optimize to look
1009 for io virtual address below 32 bit forcing dual
1010 address cycle on pci bus for cards supporting greater
1011 than 32 bit addressing. The default is to look
1012 for translation below 32 bit and if not available
1013 then look in the higher range.
1014 strict [Default Off]
1015 With this option on every unmap_single operation will
1016 result in a hardware IOTLB flush operation as opposed
1017 to batching them for performance.
1019 inttest= [IA64]
1021 iomem= Disable strict checking of access to MMIO memory
1022 strict regions from userspace.
1023 relaxed
1025 iommu= [x86]
1026 off
1027 force
1028 noforce
1029 biomerge
1030 panic
1031 nopanic
1032 merge
1033 nomerge
1034 forcesac
1035 soft
1036 pt [x86, IA64]
1038 io7= [HW] IO7 for Marvel based alpha systems
1039 See comment before marvel_specify_io7 in
1040 arch/alpha/kernel/core_marvel.c.
1042 io_delay= [X86] I/O delay method
1043 0x80
1044 Standard port 0x80 based delay
1045 0xed
1046 Alternate port 0xed based delay (needed on some systems)
1047 udelay
1048 Simple two microseconds delay
1049 none
1050 No delay
1052 ip= [IP_PNP]
1053 See Documentation/filesystems/nfs/nfsroot.txt.
1055 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1056 See comment before ip2_setup() in
1057 drivers/char/ip2/ip2base.c.
1059 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1060 See header of drivers/scsi/ips.c.
1062 irqfixup [HW]
1063 When an interrupt is not handled search all handlers
1064 for it. Intended to get systems with badly broken
1065 firmware running.
1067 irqpoll [HW]
1068 When an interrupt is not handled search all handlers
1069 for it. Also check all handlers each timer
1070 interrupt. Intended to get systems with badly broken
1071 firmware running.
1073 isapnp= [ISAPNP]
1074 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1076 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1077 Format:
1078 <cpu number>,...,<cpu number>
1079 or
1080 <cpu number>-<cpu number>
1081 (must be a positive range in ascending order)
1082 or a mixture
1083 <cpu number>,...,<cpu number>-<cpu number>
1085 This option can be used to specify one or more CPUs
1086 to isolate from the general SMP balancing and scheduling
1087 algorithms. You can move a process onto or off an
1088 "isolated" CPU via the CPU affinity syscalls or cpuset.
1089 <cpu number> begins at 0 and the maximum value is
1090 "number of CPUs in system - 1".
1092 This option is the preferred way to isolate CPUs. The
1093 alternative -- manually setting the CPU mask of all
1094 tasks in the system -- can cause problems and
1095 suboptimal load balancer performance.
1097 iucv= [HW,NET]
1099 js= [HW,JOY] Analog joystick
1100 See Documentation/input/joystick.txt.
1102 keepinitrd [HW,ARM]
1104 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1105 specifies the amount of memory usable by the kernel
1106 for non-movable allocations. The requested amount is
1107 spread evenly throughout all nodes in the system. The
1108 remaining memory in each node is used for Movable
1109 pages. In the event, a node is too small to have both
1110 kernelcore and Movable pages, kernelcore pages will
1111 take priority and other nodes will have a larger number
1112 of kernelcore pages. The Movable zone is used for the
1113 allocation of pages that may be reclaimed or moved
1114 by the page migration subsystem. This means that
1115 HugeTLB pages may not be allocated from this zone.
1116 Note that allocations like PTEs-from-HighMem still
1117 use the HighMem zone if it exists, and the Normal
1118 zone if it does not.
1120 kgdboc= [HW] kgdb over consoles.
1121 Requires a tty driver that supports console polling.
1122 (only serial supported for now)
1123 Format: <serial_device>[,baud]
1125 kmac= [MIPS] korina ethernet MAC address.
1126 Configure the RouterBoard 532 series on-chip
1127 Ethernet adapter MAC address.
1129 kmemleak= [KNL] Boot-time kmemleak enable/disable
1130 Valid arguments: on, off
1131 Default: on
1133 kstack=N [X86] Print N words from the kernel stack
1134 in oops dumps.
1136 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1137 Default is 0 (don't ignore, but inject #GP)
1139 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1140 Default is 1 (enabled)
1142 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1143 Default is 0 (off)
1145 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1146 for all guests.
1147 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1149 kvm-intel.bypass_guest_pf=
1150 [KVM,Intel] Disables bypassing of guest page faults
1151 on Intel chips. Default is 1 (enabled)
1153 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1154 (virtualized MMU) support on capable Intel chips.
1155 Default is 1 (enabled)
1157 kvm-intel.emulate_invalid_guest_state=
1158 [KVM,Intel] Enable emulation of invalid guest states
1159 Default is 0 (disabled)
1161 kvm-intel.flexpriority=
1162 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1163 Default is 1 (enabled)
1165 kvm-intel.unrestricted_guest=
1166 [KVM,Intel] Disable unrestricted guest feature
1167 (virtualized real and unpaged mode) on capable
1168 Intel chips. Default is 1 (enabled)
1170 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1171 feature (tagged TLBs) on capable Intel chips.
1172 Default is 1 (enabled)
1174 l2cr= [PPC]
1176 l3cr= [PPC]
1178 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1179 disabled it.
1181 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1182 in C2 power state.
1184 libata.dma= [LIBATA] DMA control
1185 libata.dma=0 Disable all PATA and SATA DMA
1186 libata.dma=1 PATA and SATA Disk DMA only
1187 libata.dma=2 ATAPI (CDROM) DMA only
1188 libata.dma=4 Compact Flash DMA only
1189 Combinations also work, so libata.dma=3 enables DMA
1190 for disks and CDROMs, but not CFs.
1192 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1193 libata.ignore_hpa=0 keep BIOS limits (default)
1194 libata.ignore_hpa=1 ignore limits, using full disk
1196 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1197 when set.
1198 Format: <int>
1200 libata.force= [LIBATA] Force configurations. The format is comma
1201 separated list of "[ID:]VAL" where ID is
1202 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1203 matching port, link or device. Basically, it matches
1204 the ATA ID string printed on console by libata. If
1205 the whole ID part is omitted, the last PORT and DEVICE
1206 values are used. If ID hasn't been specified yet, the
1207 configuration applies to all ports, links and devices.
1209 If only DEVICE is omitted, the parameter applies to
1210 the port and all links and devices behind it. DEVICE
1211 number of 0 either selects the first device or the
1212 first fan-out link behind PMP device. It does not
1213 select the host link. DEVICE number of 15 selects the
1214 host link and device attached to it.
1216 The VAL specifies the configuration to force. As long
1217 as there's no ambiguity shortcut notation is allowed.
1218 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1219 The following configurations can be forced.
1221 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1222 Any ID with matching PORT is used.
1224 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1226 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1227 udma[/][16,25,33,44,66,100,133] notation is also
1228 allowed.
1230 * [no]ncq: Turn on or off NCQ.
1232 * nohrst, nosrst, norst: suppress hard, soft
1233 and both resets.
1235 If there are multiple matching configurations changing
1236 the same attribute, the last one is used.
1238 lmb=debug [KNL] Enable lmb debug messages.
1240 load_ramdisk= [RAM] List of ramdisks to load from floppy
1241 See Documentation/blockdev/ramdisk.txt.
1243 lockd.nlm_grace_period=P [NFS] Assign grace period.
1244 Format: <integer>
1246 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1247 Format: <integer>
1249 lockd.nlm_timeout=T [NFS] Assign timeout value.
1250 Format: <integer>
1252 lockd.nlm_udpport=M [NFS] Assign UDP port.
1253 Format: <integer>
1255 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1256 Format: <irq>
1258 loglevel= All Kernel Messages with a loglevel smaller than the
1259 console loglevel will be printed to the console. It can
1260 also be changed with klogd or other programs. The
1261 loglevels are defined as follows:
1263 0 (KERN_EMERG) system is unusable
1264 1 (KERN_ALERT) action must be taken immediately
1265 2 (KERN_CRIT) critical conditions
1266 3 (KERN_ERR) error conditions
1267 4 (KERN_WARNING) warning conditions
1268 5 (KERN_NOTICE) normal but significant condition
1269 6 (KERN_INFO) informational
1270 7 (KERN_DEBUG) debug-level messages
1272 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1273 Format: { n | nk | nM }
1274 n must be a power of two. The default size
1275 is set in the kernel config file.
1277 logo.nologo [FB] Disables display of the built-in Linux logo.
1278 This may be used to provide more screen space for
1279 kernel log messages and is useful when debugging
1280 kernel boot problems.
1282 lp=0 [LP] Specify parallel ports to use, e.g,
1283 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1284 lp=reset first parallel port). 'lp=0' disables the
1285 lp=auto printer driver. 'lp=reset' (which can be
1286 specified in addition to the ports) causes
1287 attached printers to be reset. Using
1288 lp=port1,port2,... specifies the parallel ports
1289 to associate lp devices with, starting with
1290 lp0. A port specification may be 'none' to skip
1291 that lp device, or a parport name such as
1292 'parport0'. Specifying 'lp=auto' instead of a
1293 port specification list means that device IDs
1294 from each port should be examined, to see if
1295 an IEEE 1284-compliant printer is attached; if
1296 so, the driver will manage that printer.
1297 See also header of drivers/char/lp.c.
1299 lpj=n [KNL]
1300 Sets loops_per_jiffy to given constant, thus avoiding
1301 time-consuming boot-time autodetection (up to 250 ms per
1302 CPU). 0 enables autodetection (default). To determine
1303 the correct value for your kernel, boot with normal
1304 autodetection and see what value is printed. Note that
1305 on SMP systems the preset will be applied to all CPUs,
1306 which is likely to cause problems if your CPUs need
1307 significantly divergent settings. An incorrect value
1308 will cause delays in the kernel to be wrong, leading to
1309 unpredictable I/O errors and other breakage. Although
1310 unlikely, in the extreme case this might damage your
1311 hardware.
1313 ltpc= [NET]
1314 Format: <io>,<irq>,<dma>
1316 mac5380= [HW,SCSI] Format:
1317 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1319 machvec= [IA64] Force the use of a particular machine-vector
1320 (machvec) in a generic kernel.
1321 Example: machvec=hpzx1_swiotlb
1323 machtype= [Loongson] Share the same kernel image file between different
1324 yeeloong laptop.
1325 Example: machtype=lemote-yeeloong-2f-7inch
1327 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1328 than or equal to this physical address is ignored.
1330 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1331 should make use of. maxcpus=n : n >= 0 limits the
1332 kernel to using 'n' processors. n=0 is a special case,
1333 it is equivalent to "nosmp", which also disables
1334 the IO APIC.
1336 max_loop= [LOOP] Maximum number of loopback devices that can
1337 be mounted
1338 Format: <1-256>
1340 max_luns= [SCSI] Maximum number of LUNs to probe.
1341 Should be between 1 and 2^32-1.
1343 max_report_luns=
1344 [SCSI] Maximum number of LUNs received.
1345 Should be between 1 and 16384.
1347 mcatest= [IA-64]
1349 mce [X86-32] Machine Check Exception
1351 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1353 md= [HW] RAID subsystems devices and level
1354 See Documentation/md.txt.
1356 mdacon= [MDA]
1357 Format: <first>,<last>
1358 Specifies range of consoles to be captured by the MDA.
1360 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1361 Amount of memory to be used when the kernel is not able
1362 to see the whole system memory or for test.
1363 [X86-32] Use together with memmap= to avoid physical
1364 address space collisions. Without memmap= PCI devices
1365 could be placed at addresses belonging to unused RAM.
1367 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1368 memory.
1370 memchunk=nn[KMG]
1371 [KNL,SH] Allow user to override the default size for
1372 per-device physically contiguous DMA buffers.
1374 memmap=exactmap [KNL,X86] Enable setting of an exact
1375 E820 memory map, as specified by the user.
1376 Such memmap=exactmap lines can be constructed based on
1377 BIOS output or other requirements. See the memmap=nn@ss
1378 option description.
1380 memmap=nn[KMG]@ss[KMG]
1381 [KNL] Force usage of a specific region of memory
1382 Region of memory to be used, from ss to ss+nn.
1384 memmap=nn[KMG]#ss[KMG]
1385 [KNL,ACPI] Mark specific memory as ACPI data.
1386 Region of memory to be used, from ss to ss+nn.
1388 memmap=nn[KMG]$ss[KMG]
1389 [KNL,ACPI] Mark specific memory as reserved.
1390 Region of memory to be used, from ss to ss+nn.
1391 Example: Exclude memory from 0x18690000-0x1869ffff
1392 memmap=64K$0x18690000
1393 or
1394 memmap=0x10000$0x18690000
1396 memory_corruption_check=0/1 [X86]
1397 Some BIOSes seem to corrupt the first 64k of
1398 memory when doing things like suspend/resume.
1399 Setting this option will scan the memory
1400 looking for corruption. Enabling this will
1401 both detect corruption and prevent the kernel
1402 from using the memory being corrupted.
1403 However, its intended as a diagnostic tool; if
1404 repeatable BIOS-originated corruption always
1405 affects the same memory, you can use memmap=
1406 to prevent the kernel from using that memory.
1408 memory_corruption_check_size=size [X86]
1409 By default it checks for corruption in the low
1410 64k, making this memory unavailable for normal
1411 use. Use this parameter to scan for
1412 corruption in more or less memory.
1414 memory_corruption_check_period=seconds [X86]
1415 By default it checks for corruption every 60
1416 seconds. Use this parameter to check at some
1417 other rate. 0 disables periodic checking.
1419 memtest= [KNL,X86] Enable memtest
1420 Format: <integer>
1421 default : 0 <disable>
1422 Specifies the number of memtest passes to be
1423 performed. Each pass selects another test
1424 pattern from a given set of patterns. Memtest
1425 fills the memory with this pattern, validates
1426 memory contents and reserves bad memory
1427 regions that are detected.
1429 meye.*= [HW] Set MotionEye Camera parameters
1430 See Documentation/video4linux/meye.txt.
1432 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1433 Multi-Function General Purpose Timers on AMD Geode
1434 platforms.
1436 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1437 the BIOS has incorrectly applied a workaround. TinyBIOS
1438 version 0.98 is known to be affected, 0.99 fixes the
1439 problem by letting the user disable the workaround.
1441 mga= [HW,DRM]
1443 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1444 physical address is ignored.
1446 mini2440= [ARM,HW,KNL]
1447 Format:[0..2][b][c][t]
1448 Default: "0tb"
1449 MINI2440 configuration specification:
1450 0 - The attached screen is the 3.5" TFT
1451 1 - The attached screen is the 7" TFT
1452 2 - The VGA Shield is attached (1024x768)
1453 Leaving out the screen size parameter will not load
1454 the TFT driver, and the framebuffer will be left
1455 unconfigured.
1456 b - Enable backlight. The TFT backlight pin will be
1457 linked to the kernel VESA blanking code and a GPIO
1458 LED. This parameter is not necessary when using the
1459 VGA shield.
1460 c - Enable the s3c camera interface.
1461 t - Reserved for enabling touchscreen support. The
1462 touchscreen support is not enabled in the mainstream
1463 kernel as of 2.6.30, a preliminary port can be found
1464 in the "bleeding edge" mini2440 support kernel at
1465 http://repo.or.cz/w/linux-2.6/mini2440.git
1467 mminit_loglevel=
1468 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1469 parameter allows control of the logging verbosity for
1470 the additional memory initialisation checks. A value
1471 of 0 disables mminit logging and a level of 4 will
1472 log everything. Information is printed at KERN_DEBUG
1473 so loglevel=8 may also need to be specified.
1475 mousedev.tap_time=
1476 [MOUSE] Maximum time between finger touching and
1477 leaving touchpad surface for touch to be considered
1478 a tap and be reported as a left button click (for
1479 touchpads working in absolute mode only).
1480 Format: <msecs>
1481 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1482 reporting absolute coordinates, such as tablets
1483 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1484 reporting absolute coordinates, such as tablets
1486 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1487 is similar to kernelcore except it specifies the
1488 amount of memory used for migratable allocations.
1489 If both kernelcore and movablecore is specified,
1490 then kernelcore will be at *least* the specified
1491 value but may be more. If movablecore on its own
1492 is specified, the administrator must be careful
1493 that the amount of memory usable for all allocations
1494 is not too small.
1496 mpu401= [HW,OSS]
1497 Format: <io>,<irq>
1499 MTD_Partition= [MTD]
1500 Format: <name>,<region-number>,<size>,<offset>
1502 MTD_Region= [MTD] Format:
1503 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1505 mtdparts= [MTD]
1506 See drivers/mtd/cmdlinepart.c.
1508 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1510 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1512 boundary - index of last SLC block on Flex-OneNAND.
1513 The remaining blocks are configured as MLC blocks.
1514 lock - Configure if Flex-OneNAND boundary should be locked.
1515 Once locked, the boundary cannot be changed.
1516 1 indicates lock status, 0 indicates unlock status.
1518 mtdset= [ARM]
1519 ARM/S3C2412 JIVE boot control
1521 See arch/arm/mach-s3c2412/mach-jive.c
1523 mtouchusb.raw_coordinates=
1524 [HW] Make the MicroTouch USB driver use raw coordinates
1525 ('y', default) or cooked coordinates ('n')
1527 mtrr_chunk_size=nn[KMG] [X86]
1528 used for mtrr cleanup. It is largest continuous chunk
1529 that could hold holes aka. UC entries.
1531 mtrr_gran_size=nn[KMG] [X86]
1532 Used for mtrr cleanup. It is granularity of mtrr block.
1533 Default is 1.
1534 Large value could prevent small alignment from
1535 using up MTRRs.
1537 mtrr_spare_reg_nr=n [X86]
1538 Format: <integer>
1539 Range: 0,7 : spare reg number
1540 Default : 1
1541 Used for mtrr cleanup. It is spare mtrr entries number.
1542 Set to 2 or more if your graphical card needs more.
1544 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1546 NCR_D700= [HW,SCSI]
1547 See header of drivers/scsi/NCR_D700.c.
1549 ncr5380= [HW,SCSI]
1551 ncr53c400= [HW,SCSI]
1553 ncr53c400a= [HW,SCSI]
1555 ncr53c406a= [HW,SCSI]
1557 ncr53c8xx= [HW,SCSI]
1559 netdev= [NET] Network devices parameters
1560 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1561 Note that mem_start is often overloaded to mean
1562 something different and driver-specific.
1563 This usage is only documented in each driver source
1564 file if at all.
1566 nf_conntrack.acct=
1567 [NETFILTER] Enable connection tracking flow accounting
1568 0 to disable accounting
1569 1 to enable accounting
1570 Default value depends on CONFIG_NF_CT_ACCT that is
1571 going to be removed in 2.6.29.
1573 nfsaddrs= [NFS]
1574 See Documentation/filesystems/nfs/nfsroot.txt.
1576 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1577 See Documentation/filesystems/nfs/nfsroot.txt.
1579 nfs.callback_tcpport=
1580 [NFS] set the TCP port on which the NFSv4 callback
1581 channel should listen.
1583 nfs.cache_getent=
1584 [NFS] sets the pathname to the program which is used
1585 to update the NFS client cache entries.
1587 nfs.cache_getent_timeout=
1588 [NFS] sets the timeout after which an attempt to
1589 update a cache entry is deemed to have failed.
1591 nfs.idmap_cache_timeout=
1592 [NFS] set the maximum lifetime for idmapper cache
1593 entries.
1595 nfs.enable_ino64=
1596 [NFS] enable 64-bit inode numbers.
1597 If zero, the NFS client will fake up a 32-bit inode
1598 number for the readdir() and stat() syscalls instead
1599 of returning the full 64-bit number.
1600 The default is to return 64-bit inode numbers.
1602 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1603 when a NMI is triggered.
1604 Format: [state][,regs][,debounce][,die]
1606 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1607 Format: [panic,][num]
1608 Valid num: 0,1,2
1609 0 - turn nmi_watchdog off
1610 1 - use the IO-APIC timer for the NMI watchdog
1611 2 - use the local APIC for the NMI watchdog using
1612 a performance counter. Note: This will use one
1613 performance counter and the local APIC's performance
1614 vector.
1615 When panic is specified, panic when an NMI watchdog
1616 timeout occurs.
1617 This is useful when you use a panic=... timeout and
1618 need the box quickly up again.
1619 Instead of 1 and 2 it is possible to use the following
1620 symbolic names: lapic and ioapic
1621 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1623 netpoll.carrier_timeout=
1624 [NET] Specifies amount of time (in seconds) that
1625 netpoll should wait for a carrier. By default netpoll
1626 waits 4 seconds.
1628 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1629 emulation library even if a 387 maths coprocessor
1630 is present.
1632 no_console_suspend
1633 [HW] Never suspend the console
1634 Disable suspending of consoles during suspend and
1635 hibernate operations. Once disabled, debugging
1636 messages can reach various consoles while the rest
1637 of the system is being put to sleep (ie, while
1638 debugging driver suspend/resume hooks). This may
1639 not work reliably with all consoles, but is known
1640 to work with serial and VGA consoles.
1642 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1643 caches in the slab allocator. Saves per-node memory,
1644 but will impact performance.
1646 noalign [KNL,ARM]
1648 noapic [SMP,APIC] Tells the kernel to not make use of any
1649 IOAPICs that may be present in the system.
1651 nobats [PPC] Do not use BATs for mapping kernel lowmem
1652 on "Classic" PPC cores.
1654 nocache [ARM]
1656 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1658 nodelayacct [KNL] Disable per-task delay accounting
1660 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1662 nodsp [SH] Disable hardware DSP at boot time.
1664 noefi [X86] Disable EFI runtime services support.
1666 noexec [IA-64]
1668 noexec [X86]
1669 On X86-32 available only on PAE configured kernels.
1670 noexec=on: enable non-executable mappings (default)
1671 noexec=off: disable non-executable mappings
1673 noexec32 [X86-64]
1674 This affects only 32-bit executables.
1675 noexec32=on: enable non-executable mappings (default)
1676 read doesn't imply executable mappings
1677 noexec32=off: disable non-executable mappings
1678 read implies executable mappings
1680 nofpu [SH] Disable hardware FPU at boot time.
1682 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1683 register save and restore. The kernel will only save
1684 legacy floating-point registers on task switch.
1686 noxsave [BUGS=X86] Disables x86 extended register state save
1687 and restore using xsave. The kernel will fallback to
1688 enabling legacy floating-point and sse state.
1690 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1691 wfi(ARM) instruction doesn't work correctly and not to
1692 use it. This is also useful when using JTAG debugger.
1694 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1695 instruction doesn't work correctly and not to
1696 use it.
1698 no_file_caps Tells the kernel not to honor file capabilities. The
1699 only way then for a file to be executed with privilege
1700 is to be setuid root or executed by root.
1702 nohalt [IA-64] Tells the kernel not to use the power saving
1703 function PAL_HALT_LIGHT when idle. This increases
1704 power-consumption. On the positive side, it reduces
1705 interrupt wake-up latency, which may improve performance
1706 in certain environments such as networked servers or
1707 real-time systems.
1709 nohz= [KNL] Boottime enable/disable dynamic ticks
1710 Valid arguments: on, off
1711 Default: on
1713 noiotrap [SH] Disables trapped I/O port accesses.
1715 noirqdebug [X86-32] Disables the code which attempts to detect and
1716 disable unhandled interrupt sources.
1718 no_timer_check [X86,APIC] Disables the code which tests for
1719 broken timer IRQ sources.
1721 noisapnp [ISAPNP] Disables ISA PnP code.
1723 noinitrd [RAM] Tells the kernel not to load any configured
1724 initial RAM disk.
1726 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1727 remapping.
1729 nointroute [IA-64]
1731 nojitter [IA64] Disables jitter checking for ITC timers.
1733 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1735 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1737 noltlbs [PPC] Do not use large page/tlb entries for kernel
1738 lowmem mapping on PPC40x.
1740 nomca [IA-64] Disable machine check abort handling
1742 nomce [X86-32] Machine Check Exception
1744 nomfgpt [X86-32] Disable Multi-Function General Purpose
1745 Timer usage (for AMD Geode machines).
1747 nopat [X86] Disable PAT (page attribute table extension of
1748 pagetables) support.
1750 norandmaps Don't use address space randomization. Equivalent to
1751 echo 0 > /proc/sys/kernel/randomize_va_space
1753 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1755 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1756 with UP alternatives
1758 noresidual [PPC] Don't use residual data on PReP machines.
1760 noresume [SWSUSP] Disables resume and restores original swap
1761 space.
1763 no-scroll [VGA] Disables scrollback.
1764 This is required for the Braillex ib80-piezo Braille
1765 reader made by F.H. Papenmeier (Germany).
1767 nosbagart [IA-64]
1769 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1771 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1772 and disable the IO APIC. legacy for "maxcpus=0".
1774 nosoftlockup [KNL] Disable the soft-lockup detector.
1776 noswapaccount [KNL] Disable accounting of swap in memory resource
1777 controller. (See Documentation/cgroups/memory.txt)
1779 nosync [HW,M68K] Disables sync negotiation for all devices.
1781 notsc [BUGS=X86-32] Disable Time Stamp Counter
1783 nousb [USB] Disable the USB subsystem
1785 nowb [ARM]
1787 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1789 nptcg= [IA64] Override max number of concurrent global TLB
1790 purges which is reported from either PAL_VM_SUMMARY or
1791 SAL PALO.
1793 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1794 could support. nr_cpus=n : n >= 1 limits the kernel to
1795 supporting 'n' processors. Later in runtime you can not
1796 use hotplug cpu feature to put more cpu back to online.
1797 just like you compile the kernel NR_CPUS=n
1799 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1801 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1802 one of ['zone', 'node', 'default'] can be specified
1803 This can be set from sysctl after boot.
1804 See Documentation/sysctl/vm.txt for details.
1806 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1807 See Documentation/debugging-via-ohci1394.txt for more
1808 info.
1810 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1811 Rather than timing out after 20 ms if an EC
1812 command is not properly ACKed, override the length
1813 of the timeout. We have interrupts disabled while
1814 waiting for the ACK, so if this is set too high
1815 interrupts *may* be lost!
1817 omap_mux= [OMAP] Override bootloader pin multiplexing.
1818 Format: <mux_mode0.mode_name=value>...
1819 For example, to override I2C bus2:
1820 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1822 opl3= [HW,OSS]
1823 Format: <io>
1825 oprofile.timer= [HW]
1826 Use timer interrupt instead of performance counters
1828 oprofile.cpu_type= Force an oprofile cpu type
1829 This might be useful if you have an older oprofile
1830 userland or if you want common events.
1831 Format: { arch_perfmon }
1832 arch_perfmon: [X86] Force use of architectural
1833 perfmon on Intel CPUs instead of the
1834 CPU specific event set.
1836 osst= [HW,SCSI] SCSI Tape Driver
1837 Format: <buffer_size>,<write_threshold>
1838 See also Documentation/scsi/st.txt.
1840 panic= [KNL] Kernel behaviour on panic
1841 Format: <timeout>
1843 parkbd.port= [HW] Parallel port number the keyboard adapter is
1844 connected to, default is 0.
1845 Format: <parport#>
1846 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1847 0 for XT, 1 for AT (default is AT).
1848 Format: <mode>
1850 parport= [HW,PPT] Specify parallel ports. 0 disables.
1851 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1852 Use 'auto' to force the driver to use any
1853 IRQ/DMA settings detected (the default is to
1854 ignore detected IRQ/DMA settings because of
1855 possible conflicts). You can specify the base
1856 address, IRQ, and DMA settings; IRQ and DMA
1857 should be numbers, or 'auto' (for using detected
1858 settings on that particular port), or 'nofifo'
1859 (to avoid using a FIFO even if it is detected).
1860 Parallel ports are assigned in the order they
1861 are specified on the command line, starting
1862 with parport0.
1864 parport_init_mode= [HW,PPT]
1865 Configure VIA parallel port to operate in
1866 a specific mode. This is necessary on Pegasos
1867 computer where firmware has no options for setting
1868 up parallel port mode and sets it to spp.
1869 Currently this function knows 686a and 8231 chips.
1870 Format: [spp|ps2|epp|ecp|ecpepp]
1872 pas2= [HW,OSS] Format:
1873 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1875 pas16= [HW,SCSI]
1876 See header of drivers/scsi/pas16.c.
1878 pause_on_oops=
1879 Halt all CPUs after the first oops has been printed for
1880 the specified number of seconds. This is to be used if
1881 your oopses keep scrolling off the screen.
1883 pcbit= [HW,ISDN]
1885 pcd. [PARIDE]
1886 See header of drivers/block/paride/pcd.c.
1887 See also Documentation/blockdev/paride.txt.
1889 pci=option[,option...] [PCI] various PCI subsystem options:
1890 earlydump [X86] dump PCI config space before the kernel
1891 changes anything
1892 off [X86] don't probe for the PCI bus
1893 bios [X86-32] force use of PCI BIOS, don't access
1894 the hardware directly. Use this if your machine
1895 has a non-standard PCI host bridge.
1896 nobios [X86-32] disallow use of PCI BIOS, only direct
1897 hardware access methods are allowed. Use this
1898 if you experience crashes upon bootup and you
1899 suspect they are caused by the BIOS.
1900 conf1 [X86] Force use of PCI Configuration
1901 Mechanism 1.
1902 conf2 [X86] Force use of PCI Configuration
1903 Mechanism 2.
1904 noaer [PCIE] If the PCIEAER kernel config parameter is
1905 enabled, this kernel boot option can be used to
1906 disable the use of PCIE advanced error reporting.
1907 nodomains [PCI] Disable support for multiple PCI
1908 root domains (aka PCI segments, in ACPI-speak).
1909 nommconf [X86] Disable use of MMCONFIG for PCI
1910 Configuration
1911 check_enable_amd_mmconf [X86] check for and enable
1912 properly configured MMIO access to PCI
1913 config space on AMD family 10h CPU
1914 nomsi [MSI] If the PCI_MSI kernel config parameter is
1915 enabled, this kernel boot option can be used to
1916 disable the use of MSI interrupts system-wide.
1917 noioapicquirk [APIC] Disable all boot interrupt quirks.
1918 Safety option to keep boot IRQs enabled. This
1919 should never be necessary.
1920 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1921 primary IO-APIC for bridges that cannot disable
1922 boot IRQs. This fixes a source of spurious IRQs
1923 when the system masks IRQs.
1924 noioapicreroute [APIC] Disable workaround that uses the
1925 boot IRQ equivalent of an IRQ that connects to
1926 a chipset where boot IRQs cannot be disabled.
1927 The opposite of ioapicreroute.
1928 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1929 routing table. These calls are known to be buggy
1930 on several machines and they hang the machine
1931 when used, but on other computers it's the only
1932 way to get the interrupt routing table. Try
1933 this option if the kernel is unable to allocate
1934 IRQs or discover secondary PCI buses on your
1935 motherboard.
1936 rom [X86] Assign address space to expansion ROMs.
1937 Use with caution as certain devices share
1938 address decoders between ROMs and other
1939 resources.
1940 norom [X86] Do not assign address space to
1941 expansion ROMs that do not already have
1942 BIOS assigned address ranges.
1943 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1944 assigned automatically to PCI devices. You can
1945 make the kernel exclude IRQs of your ISA cards
1946 this way.
1947 pirqaddr=0xAAAAA [X86] Specify the physical address
1948 of the PIRQ table (normally generated
1949 by the BIOS) if it is outside the
1950 F0000h-100000h range.
1951 lastbus=N [X86] Scan all buses thru bus #N. Can be
1952 useful if the kernel is unable to find your
1953 secondary buses and you want to tell it
1954 explicitly which ones they are.
1955 assign-busses [X86] Always assign all PCI bus
1956 numbers ourselves, overriding
1957 whatever the firmware may have done.
1958 usepirqmask [X86] Honor the possible IRQ mask stored
1959 in the BIOS $PIR table. This is needed on
1960 some systems with broken BIOSes, notably
1961 some HP Pavilion N5400 and Omnibook XE3
1962 notebooks. This will have no effect if ACPI
1963 IRQ routing is enabled.
1964 noacpi [X86] Do not use ACPI for IRQ routing
1965 or for PCI scanning.
1966 use_crs [X86] Use PCI host bridge window information
1967 from ACPI. On BIOSes from 2008 or later, this
1968 is enabled by default. If you need to use this,
1969 please report a bug.
1970 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1971 If you need to use this, please report a bug.
1972 routeirq Do IRQ routing for all PCI devices.
1973 This is normally done in pci_enable_device(),
1974 so this option is a temporary workaround
1975 for broken drivers that don't call it.
1976 skip_isa_align [X86] do not align io start addr, so can
1977 handle more pci cards
1978 firmware [ARM] Do not re-enumerate the bus but instead
1979 just use the configuration from the
1980 bootloader. This is currently used on
1981 IXP2000 systems where the bus has to be
1982 configured a certain way for adjunct CPUs.
1983 noearly [X86] Don't do any early type 1 scanning.
1984 This might help on some broken boards which
1985 machine check when some devices' config space
1986 is read. But various workarounds are disabled
1987 and some IOMMU drivers will not work.
1988 bfsort Sort PCI devices into breadth-first order.
1989 This sorting is done to get a device
1990 order compatible with older (<= 2.4) kernels.
1991 nobfsort Don't sort PCI devices into breadth-first order.
1992 cbiosize=nn[KMG] The fixed amount of bus space which is
1993 reserved for the CardBus bridge's IO window.
1994 The default value is 256 bytes.
1995 cbmemsize=nn[KMG] The fixed amount of bus space which is
1996 reserved for the CardBus bridge's memory
1997 window. The default value is 64 megabytes.
1998 resource_alignment=
1999 Format:
2000 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2001 Specifies alignment and device to reassign
2002 aligned memory resources.
2003 If <order of align> is not specified,
2004 PAGE_SIZE is used as alignment.
2005 PCI-PCI bridge can be specified, if resource
2006 windows need to be expanded.
2007 ecrc= Enable/disable PCIe ECRC (transaction layer
2008 end-to-end CRC checking).
2009 bios: Use BIOS/firmware settings. This is the
2010 the default.
2011 off: Turn ECRC off
2012 on: Turn ECRC on.
2014 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2015 Management.
2016 off Disable ASPM.
2017 force Enable ASPM even on devices that claim not to support it.
2018 WARNING: Forcing ASPM on may cause system lockups.
2020 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2021 off Do not use native PCIe PME signaling.
2022 force Use native PCIe PME signaling even if the BIOS refuses
2023 to allow the kernel to control the relevant PCIe config
2024 registers.
2025 nomsi Do not use MSI for native PCIe PME signaling (this makes
2026 all PCIe root ports use INTx for everything).
2028 pcmv= [HW,PCMCIA] BadgePAD 4
2030 pd. [PARIDE]
2031 See Documentation/blockdev/paride.txt.
2033 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2034 boot time.
2035 Format: { 0 | 1 }
2036 See arch/parisc/kernel/pdc_chassis.c
2038 percpu_alloc= Select which percpu first chunk allocator to use.
2039 Currently supported values are "embed" and "page".
2040 Archs may support subset or none of the selections.
2041 See comments in mm/percpu.c for details on each
2042 allocator. This parameter is primarily for debugging
2043 and performance comparison.
2045 pf. [PARIDE]
2046 See Documentation/blockdev/paride.txt.
2048 pg. [PARIDE]
2049 See Documentation/blockdev/paride.txt.
2051 pirq= [SMP,APIC] Manual mp-table setup
2052 See Documentation/x86/i386/IO-APIC.txt.
2054 plip= [PPT,NET] Parallel port network link
2055 Format: { parport<nr> | timid | 0 }
2056 See also Documentation/parport.txt.
2058 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2059 Override pmtimer IOPort with a hex value.
2060 e.g. pmtmr=0x508
2062 pnp.debug [PNP]
2063 Enable PNP debug messages. This depends on the
2064 CONFIG_PNP_DEBUG_MESSAGES option.
2066 pnpacpi= [ACPI]
2067 { off }
2069 pnpbios= [ISAPNP]
2070 { on | off | curr | res | no-curr | no-res }
2072 pnp_reserve_irq=
2073 [ISAPNP] Exclude IRQs for the autoconfiguration
2075 pnp_reserve_dma=
2076 [ISAPNP] Exclude DMAs for the autoconfiguration
2078 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2079 Ranges are in pairs (I/O port base and size).
2081 pnp_reserve_mem=
2082 [ISAPNP] Exclude memory regions for the
2083 autoconfiguration.
2084 Ranges are in pairs (memory base and size).
2086 ports= [IP_VS_FTP] IPVS ftp helper module
2087 Default is 21.
2088 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2089 may be specified.
2090 Format: <port>,<port>....
2092 print-fatal-signals=
2093 [KNL] debug: print fatal signals
2095 If enabled, warn about various signal handling
2096 related application anomalies: too many signals,
2097 too many POSIX.1 timers, fatal signals causing a
2098 coredump - etc.
2100 If you hit the warning due to signal overflow,
2101 you might want to try "ulimit -i unlimited".
2103 default: off.
2105 printk.time= Show timing data prefixed to each printk message line
2106 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2108 processor.max_cstate= [HW,ACPI]
2109 Limit processor to maximum C-state
2110 max_cstate=9 overrides any DMI blacklist limit.
2112 processor.nocst [HW,ACPI]
2113 Ignore the _CST method to determine C-states,
2114 instead using the legacy FADT method
2116 profile= [KNL] Enable kernel profiling via /proc/profile
2117 Format: [schedule,]<number>
2118 Param: "schedule" - profile schedule points.
2119 Param: <number> - step/bucket size as a power of 2 for
2120 statistical time based profiling.
2121 Param: "sleep" - profile D-state sleeping (millisecs).
2122 Requires CONFIG_SCHEDSTATS
2123 Param: "kvm" - profile VM exits.
2125 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2126 before loading.
2127 See Documentation/blockdev/ramdisk.txt.
2129 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2130 probe for; one of (bare|imps|exps|lifebook|any).
2131 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2132 per second.
2133 psmouse.resetafter= [HW,MOUSE]
2134 Try to reset the device after so many bad packets
2135 (0 = never).
2136 psmouse.resolution=
2137 [HW,MOUSE] Set desired mouse resolution, in dpi.
2138 psmouse.smartscroll=
2139 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2140 0 = disabled, 1 = enabled (default).
2142 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2143 Format:
2144 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2146 pt. [PARIDE]
2147 See Documentation/blockdev/paride.txt.
2149 pty.legacy_count=
2150 [KNL] Number of legacy pty's. Overwrites compiled-in
2151 default number.
2153 quiet [KNL] Disable most log messages
2155 r128= [HW,DRM]
2157 raid= [HW,RAID]
2158 See Documentation/md.txt.
2160 ramdisk_blocksize= [RAM]
2161 See Documentation/blockdev/ramdisk.txt.
2163 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2164 See Documentation/blockdev/ramdisk.txt.
2166 rcupdate.blimit= [KNL,BOOT]
2167 Set maximum number of finished RCU callbacks to process
2168 in one batch.
2170 rcupdate.qhimark= [KNL,BOOT]
2171 Set threshold of queued
2172 RCU callbacks over which batch limiting is disabled.
2174 rcupdate.qlowmark= [KNL,BOOT]
2175 Set threshold of queued RCU callbacks below which
2176 batch limiting is re-enabled.
2178 rdinit= [KNL]
2179 Format: <full_path>
2180 Run specified binary instead of /init from the ramdisk,
2181 used for early userspace startup. See initrd.
2183 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2184 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2185 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2187 relax_domain_level=
2188 [KNL, SMP] Set scheduler's default relax_domain_level.
2189 See Documentation/cgroups/cpusets.txt.
2191 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2193 reservetop= [X86-32]
2194 Format: nn[KMG]
2195 Reserves a hole at the top of the kernel virtual
2196 address space.
2198 reset_devices [KNL] Force drivers to reset the underlying device
2199 during initialization.
2201 resume= [SWSUSP]
2202 Specify the partition device for software suspend
2204 resume_offset= [SWSUSP]
2205 Specify the offset from the beginning of the partition
2206 given by "resume=" at which the swap header is located,
2207 in <PAGE_SIZE> units (needed only for swap files).
2208 See Documentation/power/swsusp-and-swap-files.txt
2210 retain_initrd [RAM] Keep initrd memory after extraction
2212 rhash_entries= [KNL,NET]
2213 Set number of hash buckets for route cache
2215 riscom8= [HW,SERIAL]
2216 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2218 ro [KNL] Mount root device read-only on boot
2220 root= [KNL] Root filesystem
2222 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2223 mount the root filesystem
2225 rootflags= [KNL] Set root filesystem mount option string
2227 rootfstype= [KNL] Set root filesystem type
2229 rootwait [KNL] Wait (indefinitely) for root device to show up.
2230 Useful for devices that are detected asynchronously
2231 (e.g. USB and MMC devices).
2233 rw [KNL] Mount root device read-write on boot
2235 S [KNL] Run init in single mode
2237 sa1100ir [NET]
2238 See drivers/net/irda/sa1100_ir.c.
2240 sbni= [NET] Granch SBNI12 leased line adapter
2242 sched_debug [KNL] Enables verbose scheduler debug messages.
2244 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2245 Format: <io>[,<timeout>[,<isapnp>]]
2247 scsi_debug_*= [SCSI]
2248 See drivers/scsi/scsi_debug.c.
2250 scsi_default_dev_flags=
2251 [SCSI] SCSI default device flags
2252 Format: <integer>
2254 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2255 Format: <vendor>:<model>:<flags>
2256 (flags are integer value)
2258 scsi_logging_level= [SCSI] a bit mask of logging levels
2259 See drivers/scsi/scsi_logging.h for bits. Also
2260 settable via sysctl at dev.scsi.logging_level
2261 (/proc/sys/dev/scsi/logging_level).
2262 There is also a nice 'scsi_logging_level' script in the
2263 S390-tools package, available for download at
2264 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2266 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2267 discovered. async scans them in kernel threads,
2268 allowing boot to proceed. none ignores them, expecting
2269 user space to do the scan.
2271 security= [SECURITY] Choose a security module to enable at boot.
2272 If this boot parameter is not specified, only the first
2273 security module asking for security registration will be
2274 loaded. An invalid security module name will be treated
2275 as if no module has been chosen.
2277 selinux= [SELINUX] Disable or enable SELinux at boot time.
2278 Format: { "0" | "1" }
2279 See security/selinux/Kconfig help text.
2280 0 -- disable.
2281 1 -- enable.
2282 Default value is set via kernel config option.
2283 If enabled at boot time, /selinux/disable can be used
2284 later to disable prior to initial policy load.
2286 serialnumber [BUGS=X86-32]
2288 shapers= [NET]
2289 Maximal number of shapers.
2291 show_msr= [x86] show boot-time MSR settings
2292 Format: { <integer> }
2293 Show boot-time (BIOS-initialized) MSR settings.
2294 The parameter means the number of CPUs to show,
2295 for example 1 means boot CPU only.
2297 sim710= [SCSI,HW]
2298 See header of drivers/scsi/sim710.c.
2300 simeth= [IA-64]
2301 simscsi=
2303 slram= [HW,MTD]
2305 slub_debug[=options[,slabs]] [MM, SLUB]
2306 Enabling slub_debug allows one to determine the
2307 culprit if slab objects become corrupted. Enabling
2308 slub_debug can create guard zones around objects and
2309 may poison objects when not in use. Also tracks the
2310 last alloc / free. For more information see
2311 Documentation/vm/slub.txt.
2313 slub_max_order= [MM, SLUB]
2314 Determines the maximum allowed order for slabs.
2315 A high setting may cause OOMs due to memory
2316 fragmentation. For more information see
2317 Documentation/vm/slub.txt.
2319 slub_min_objects= [MM, SLUB]
2320 The minimum number of objects per slab. SLUB will
2321 increase the slab order up to slub_max_order to
2322 generate a sufficiently large slab able to contain
2323 the number of objects indicated. The higher the number
2324 of objects the smaller the overhead of tracking slabs
2325 and the less frequently locks need to be acquired.
2326 For more information see Documentation/vm/slub.txt.
2328 slub_min_order= [MM, SLUB]
2329 Determines the mininum page order for slabs. Must be
2330 lower than slub_max_order.
2331 For more information see Documentation/vm/slub.txt.
2333 slub_nomerge [MM, SLUB]
2334 Disable merging of slabs with similar size. May be
2335 necessary if there is some reason to distinguish
2336 allocs to different slabs. Debug options disable
2337 merging on their own.
2338 For more information see Documentation/vm/slub.txt.
2340 smart2= [HW]
2341 Format: <io1>[,<io2>[,...,<io8>]]
2343 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2344 attempt to substitute SMP alternatives once at boot.
2346 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2347 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2348 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2349 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2350 smsc-ircc2.ircc_irq= [HW] IRQ line
2351 smsc-ircc2.ircc_dma= [HW] DMA channel
2352 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2353 0: Toshiba Satellite 1800 (GP data pin select)
2354 1: Fast pin select (default)
2355 2: ATC IRMode
2357 snd-ad1816a= [HW,ALSA]
2359 snd-ad1848= [HW,ALSA]
2361 snd-ali5451= [HW,ALSA]
2363 snd-als100= [HW,ALSA]
2365 snd-als4000= [HW,ALSA]
2367 snd-azt2320= [HW,ALSA]
2369 snd-cmi8330= [HW,ALSA]
2371 snd-cmipci= [HW,ALSA]
2373 snd-cs4231= [HW,ALSA]
2375 snd-cs4232= [HW,ALSA]
2377 snd-cs4236= [HW,ALSA]
2379 snd-cs4281= [HW,ALSA]
2381 snd-cs46xx= [HW,ALSA]
2383 snd-dt019x= [HW,ALSA]
2385 snd-dummy= [HW,ALSA]
2387 snd-emu10k1= [HW,ALSA]
2389 snd-ens1370= [HW,ALSA]
2391 snd-ens1371= [HW,ALSA]
2393 snd-es968= [HW,ALSA]
2395 snd-es1688= [HW,ALSA]
2397 snd-es18xx= [HW,ALSA]
2399 snd-es1938= [HW,ALSA]
2401 snd-es1968= [HW,ALSA]
2403 snd-fm801= [HW,ALSA]
2405 snd-gusclassic= [HW,ALSA]
2407 snd-gusextreme= [HW,ALSA]
2409 snd-gusmax= [HW,ALSA]
2411 snd-hdsp= [HW,ALSA]
2413 snd-ice1712= [HW,ALSA]
2415 snd-intel8x0= [HW,ALSA]
2417 snd-interwave= [HW,ALSA]
2419 snd-interwave-stb=
2420 [HW,ALSA]
2422 snd-korg1212= [HW,ALSA]
2424 snd-maestro3= [HW,ALSA]
2426 snd-mpu401= [HW,ALSA]
2428 snd-mtpav= [HW,ALSA]
2430 snd-nm256= [HW,ALSA]
2432 snd-opl3sa2= [HW,ALSA]
2434 snd-opti92x-ad1848=
2435 [HW,ALSA]
2437 snd-opti92x-cs4231=
2438 [HW,ALSA]
2440 snd-opti93x= [HW,ALSA]
2442 snd-pmac= [HW,ALSA]
2444 snd-rme32= [HW,ALSA]
2446 snd-rme96= [HW,ALSA]
2448 snd-rme9652= [HW,ALSA]
2450 snd-sb8= [HW,ALSA]
2452 snd-sb16= [HW,ALSA]
2454 snd-sbawe= [HW,ALSA]
2456 snd-serial= [HW,ALSA]
2458 snd-sgalaxy= [HW,ALSA]
2460 snd-sonicvibes= [HW,ALSA]
2462 snd-sun-amd7930=
2463 [HW,ALSA]
2465 snd-sun-cs4231= [HW,ALSA]
2467 snd-trident= [HW,ALSA]
2469 snd-usb-audio= [HW,ALSA,USB]
2471 snd-via82xx= [HW,ALSA]
2473 snd-virmidi= [HW,ALSA]
2475 snd-wavefront= [HW,ALSA]
2477 snd-ymfpci= [HW,ALSA]
2479 softlockup_panic=
2480 [KNL] Should the soft-lockup detector generate panics.
2482 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2483 See Documentation/sonypi.txt
2485 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2486 See Documentation/serial/specialix.txt.
2488 spia_io_base= [HW,MTD]
2489 spia_fio_base=
2490 spia_pedr=
2491 spia_peddr=
2493 sscape= [HW,OSS]
2494 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2496 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2497 See Documentation/scsi/st.txt.
2499 stacktrace [FTRACE]
2500 Enabled the stack tracer on boot up.
2502 sti= [PARISC,HW]
2503 Format: <num>
2504 Set the STI (builtin display/keyboard on the HP-PARISC
2505 machines) console (graphic card) which should be used
2506 as the initial boot-console.
2507 See also comment in drivers/video/console/sticore.c.
2509 sti_font= [HW]
2510 See comment in drivers/video/console/sticore.c.
2512 stifb= [HW]
2513 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2515 sunrpc.min_resvport=
2516 sunrpc.max_resvport=
2517 [NFS,SUNRPC]
2518 SunRPC servers often require that client requests
2519 originate from a privileged port (i.e. a port in the
2520 range 0 < portnr < 1024).
2521 An administrator who wishes to reserve some of these
2522 ports for other uses may adjust the range that the
2523 kernel's sunrpc client considers to be privileged
2524 using these two parameters to set the minimum and
2525 maximum port values.
2527 sunrpc.pool_mode=
2528 [NFS]
2529 Control how the NFS server code allocates CPUs to
2530 service thread pools. Depending on how many NICs
2531 you have and where their interrupts are bound, this
2532 option will affect which CPUs will do NFS serving.
2533 Note: this parameter cannot be changed while the
2534 NFS server is running.
2536 auto the server chooses an appropriate mode
2537 automatically using heuristics
2538 global a single global pool contains all CPUs
2539 percpu one pool for each CPU
2540 pernode one pool for each NUMA node (equivalent
2541 to global on non-NUMA machines)
2543 sunrpc.tcp_slot_table_entries=
2544 sunrpc.udp_slot_table_entries=
2545 [NFS,SUNRPC]
2546 Sets the upper limit on the number of simultaneous
2547 RPC calls that can be sent from the client to a
2548 server. Increasing these values may allow you to
2549 improve throughput, but will also increase the
2550 amount of memory reserved for use by the client.
2552 swiotlb= [IA-64] Number of I/O TLB slabs
2554 switches= [HW,M68k]
2556 sym53c416= [HW,SCSI]
2557 See header of drivers/scsi/sym53c416.c.
2559 sysrq_always_enabled
2560 [KNL]
2561 Ignore sysrq setting - this boot parameter will
2562 neutralize any effect of /proc/sys/kernel/sysrq.
2563 Useful for debugging.
2565 t128= [HW,SCSI]
2566 See header of drivers/scsi/t128.c.
2568 tdfx= [HW,DRM]
2570 test_suspend= [SUSPEND]
2571 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2572 standby suspend) as the system sleep state to briefly
2573 enter during system startup. The system is woken from
2574 this state using a wakeup-capable RTC alarm.
2576 thash_entries= [KNL,NET]
2577 Set number of hash buckets for TCP connection
2579 thermal.act= [HW,ACPI]
2580 -1: disable all active trip points in all thermal zones
2581 <degrees C>: override all lowest active trip points
2583 thermal.crt= [HW,ACPI]
2584 -1: disable all critical trip points in all thermal zones
2585 <degrees C>: override all critical trip points
2587 thermal.nocrt= [HW,ACPI]
2588 Set to disable actions on ACPI thermal zone
2589 critical and hot trip points.
2591 thermal.off= [HW,ACPI]
2592 1: disable ACPI thermal control
2594 thermal.psv= [HW,ACPI]
2595 -1: disable all passive trip points
2596 <degrees C>: override all passive trip points to this
2597 value
2599 thermal.tzp= [HW,ACPI]
2600 Specify global default ACPI thermal zone polling rate
2601 <deci-seconds>: poll all this frequency
2602 0: no polling (default)
2604 tmscsim= [HW,SCSI]
2605 See comment before function dc390_setup() in
2606 drivers/scsi/tmscsim.c.
2608 topology= [S390]
2609 Format: {off | on}
2610 Specify if the kernel should make use of the cpu
2611 topology informations if the hardware supports these.
2612 The scheduler will make use of these informations and
2613 e.g. base its process migration decisions on it.
2614 Default is off.
2616 tp720= [HW,PS2]
2618 trace_buf_size=nn[KMG]
2619 [FTRACE] will set tracing buffer size.
2621 trace_event=[event-list]
2622 [FTRACE] Set and start specified trace events in order
2623 to facilitate early boot debugging.
2624 See also Documentation/trace/events.txt
2626 trix= [HW,OSS] MediaTrix AudioTrix Pro
2627 Format:
2628 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2630 tsc= Disable clocksource-must-verify flag for TSC.
2631 Format: <string>
2632 [x86] reliable: mark tsc clocksource as reliable, this
2633 disables clocksource verification at runtime.
2634 Used to enable high-resolution timer mode on older
2635 hardware, and in virtualized environment.
2637 turbografx.map[2|3]= [HW,JOY]
2638 TurboGraFX parallel port interface
2639 Format:
2640 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2641 See also Documentation/input/joystick-parport.txt
2643 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2644 See header of drivers/scsi/u14-34f.c.
2646 uart401= [HW,OSS]
2647 Format: <io>,<irq>
2649 uart6850= [HW,OSS]
2650 Format: <io>,<irq>
2652 uhash_entries= [KNL,NET]
2653 Set number of hash buckets for UDP/UDP-Lite connections
2655 uhci-hcd.ignore_oc=
2656 [USB] Ignore overcurrent events (default N).
2657 Some badly-designed motherboards generate lots of
2658 bogus events, for ports that aren't wired to
2659 anything. Set this parameter to avoid log spamming.
2660 Note that genuine overcurrent events won't be
2661 reported either.
2663 unknown_nmi_panic
2664 [X86]
2665 Set unknown_nmi_panic=1 early on boot.
2667 usbcore.autosuspend=
2668 [USB] The autosuspend time delay (in seconds) used
2669 for newly-detected USB devices (default 2). This
2670 is the time required before an idle device will be
2671 autosuspended. Devices for which the delay is set
2672 to a negative value won't be autosuspended at all.
2674 usbcore.usbfs_snoop=
2675 [USB] Set to log all usbfs traffic (default 0 = off).
2677 usbcore.blinkenlights=
2678 [USB] Set to cycle leds on hubs (default 0 = off).
2680 usbcore.old_scheme_first=
2681 [USB] Start with the old device initialization
2682 scheme (default 0 = off).
2684 usbcore.use_both_schemes=
2685 [USB] Try the other device initialization scheme
2686 if the first one fails (default 1 = enabled).
2688 usbcore.initial_descriptor_timeout=
2689 [USB] Specifies timeout for the initial 64-byte
2690 USB_REQ_GET_DESCRIPTOR request in milliseconds
2691 (default 5000 = 5.0 seconds).
2693 usbhid.mousepoll=
2694 [USBHID] The interval which mice are to be polled at.
2696 usb-storage.delay_use=
2697 [UMS] The delay in seconds before a new device is
2698 scanned for Logical Units (default 5).
2700 usb-storage.quirks=
2701 [UMS] A list of quirks entries to supplement or
2702 override the built-in unusual_devs list. List
2703 entries are separated by commas. Each entry has
2704 the form VID:PID:Flags where VID and PID are Vendor
2705 and Product ID values (4-digit hex numbers) and
2706 Flags is a set of characters, each corresponding
2707 to a common usb-storage quirk flag as follows:
2708 a = SANE_SENSE (collect more than 18 bytes
2709 of sense data);
2710 b = BAD_SENSE (don't collect more than 18
2711 bytes of sense data);
2712 c = FIX_CAPACITY (decrease the reported
2713 device capacity by one sector);
2714 h = CAPACITY_HEURISTICS (decrease the
2715 reported device capacity by one
2716 sector if the number is odd);
2717 i = IGNORE_DEVICE (don't bind to this
2718 device);
2719 l = NOT_LOCKABLE (don't try to lock and
2720 unlock ejectable media);
2721 m = MAX_SECTORS_64 (don't transfer more
2722 than 64 sectors = 32 KB at a time);
2723 o = CAPACITY_OK (accept the capacity
2724 reported by the device);
2725 r = IGNORE_RESIDUE (the device reports
2726 bogus residue values);
2727 s = SINGLE_LUN (the device has only one
2728 Logical Unit);
2729 w = NO_WP_DETECT (don't test whether the
2730 medium is write-protected).
2731 Example: quirks=0419:aaf5:rl,0421:0433:rc
2733 userpte=
2734 [X86] Flags controlling user PTE allocations.
2736 nohigh = do not allocate PTE pages in
2737 HIGHMEM regardless of setting
2738 of CONFIG_HIGHPTE.
2740 vdso= [X86,SH]
2741 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2742 vdso=1: enable VDSO (default)
2743 vdso=0: disable VDSO mapping
2745 vdso32= [X86]
2746 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2747 vdso32=1: enable 32-bit VDSO (default)
2748 vdso32=0: disable 32-bit VDSO mapping
2750 vector= [IA-64,SMP]
2751 vector=percpu: enable percpu vector domain
2753 video= [FB] Frame buffer configuration
2754 See Documentation/fb/modedb.txt.
2756 vga= [BOOT,X86-32] Select a particular video mode
2757 See Documentation/x86/boot.txt and
2758 Documentation/svga.txt.
2759 Use vga=ask for menu.
2760 This is actually a boot loader parameter; the value is
2761 passed to the kernel using a special protocol.
2763 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2764 size of <nn>. This can be used to increase the
2765 minimum size (128MB on x86). It can also be used to
2766 decrease the size and leave more room for directly
2767 mapped kernel RAM.
2769 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2770 Format: <command>
2772 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2773 Format: <command>
2775 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2776 Format: <command>
2778 vt.cur_default= [VT] Default cursor shape.
2779 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2780 the parameters of the <Esc>[?A;B;Cc escape sequence;
2781 see VGA-softcursor.txt. Default: 2 = underline.
2783 vt.default_blu= [VT]
2784 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2785 Change the default blue palette of the console.
2786 This is a 16-member array composed of values
2787 ranging from 0-255.
2789 vt.default_grn= [VT]
2790 Format: <green0>,<green1>,<green2>,...,<green15>
2791 Change the default green palette of the console.
2792 This is a 16-member array composed of values
2793 ranging from 0-255.
2795 vt.default_red= [VT]
2796 Format: <red0>,<red1>,<red2>,...,<red15>
2797 Change the default red palette of the console.
2798 This is a 16-member array composed of values
2799 ranging from 0-255.
2801 vt.default_utf8=
2802 [VT]
2803 Format=<0|1>
2804 Set system-wide default UTF-8 mode for all tty's.
2805 Default is 1, i.e. UTF-8 mode is enabled for all
2806 newly opened terminals.
2808 vt.global_cursor_default=
2809 [VT]
2810 Format=<-1|0|1>
2811 Set system-wide default for whether a cursor
2812 is shown on new VTs. Default is -1,
2813 i.e. cursors will be created by default unless
2814 overridden by individual drivers. 0 will hide
2815 cursors, 1 will display them.
2817 waveartist= [HW,OSS]
2818 Format: <io>,<irq>,<dma>,<dma2>
2820 wd33c93= [HW,SCSI]
2821 See header of drivers/scsi/wd33c93.c.
2823 wd7000= [HW,SCSI]
2824 See header of drivers/scsi/wd7000.c.
2826 wdt= [WDT] Watchdog
2827 See Documentation/watchdog/wdt.txt.
2829 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2830 default x2apic cluster mode on platforms
2831 supporting x2apic.
2833 x86_mrst_timer= [X86-32,APBT]
2834 Choose timer option for x86 Moorestown MID platform.
2835 Two valid options are apbt timer only and lapic timer
2836 plus one apbt timer for broadcast timer.
2837 x86_mrst_timer=apbt_only | lapic_and_apbt
2839 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2840 xd_geo= See header of drivers/block/xd.c.
2842 xirc2ps_cs= [NET,PCMCIA]
2843 Format:
2844 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2846 ______________________________________________________________________
2848 TODO:
2850 Add documentation for ALSA options.
2851 Add more DRM drivers.