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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 GCOV GCOV profiling is enabled.
52 HW Appropriate hardware is enabled.
53 IA-64 IA-64 architecture is enabled.
54 IMA Integrity measurement architecture is enabled.
55 IOSCHED More than one I/O scheduler is enabled.
56 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
57 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 TPM TPM drivers are enabled.
103 TS Appropriate touchscreen support is enabled.
104 UMS USB Mass Storage support is enabled.
105 USB USB support is enabled.
106 USBHID USB Human Interface Device support is enabled.
107 V4L Video For Linux support is enabled.
108 VGA The VGA console has been enabled.
109 VT Virtual terminal support is enabled.
110 WDT Watchdog support is enabled.
111 XT IBM PC/XT MFM hard disk support is enabled.
112 X86-32 X86-32, aka i386 architecture is enabled.
113 X86-64 X86-64 architecture is enabled.
114 More X86-64 boot options can be found in
115 Documentation/x86/x86_64/boot-options.txt .
116 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
118 In addition, the following text indicates that the option:
120 BUGS= Relates to possible processor bugs on the said processor.
121 KNL Is a kernel start-up parameter.
122 BOOT Is a boot loader parameter.
124 Parameters denoted with BOOT are actually interpreted by the boot
125 loader, and have no meaning to the kernel directly.
126 Do not modify the syntax of boot loader parameters without extreme
127 need or coordination with <Documentation/x86/boot.txt>.
129 There are also arch-specific kernel-parameters not documented here.
130 See for example <Documentation/x86/x86_64/boot-options.txt>.
132 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
133 a trailing = on the name of any parameter states that that parameter will
134 be entered as an environment variable, whereas its absence indicates that
135 it will appear as a kernel argument readable via /proc/cmdline by programs
136 running once the system is up.
138 The number of kernel parameters is not limited, but the length of the
139 complete command line (parameters including spaces etc.) is limited to
140 a fixed number of characters. This limit depends on the architecture
141 and is between 256 and 4096 characters. It is defined in the file
142 ./include/asm/setup.h as COMMAND_LINE_SIZE.
145 acpi= [HW,ACPI,X86]
146 Advanced Configuration and Power Interface
147 Format: { force | off | ht | strict | noirq | rsdt }
148 force -- enable ACPI if default was off
149 off -- disable ACPI if default was on
150 noirq -- do not use ACPI for IRQ routing
151 ht -- run only enough ACPI to enable Hyper Threading
152 strict -- Be less tolerant of platforms that are not
153 strictly ACPI specification compliant.
154 rsdt -- prefer RSDT over (default) XSDT
155 copy_dsdt -- copy DSDT to memory
157 See also Documentation/power/pm.txt, pci=noacpi
159 acpi_apic_instance= [ACPI, IOAPIC]
160 Format: <int>
161 2: use 2nd APIC table, if available
162 1,0: use 1st APIC table
163 default: 0
165 acpi_backlight= [HW,ACPI]
166 acpi_backlight=vendor
167 acpi_backlight=video
168 If set to vendor, prefer vendor specific driver
169 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
170 of the ACPI video.ko driver.
172 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
173 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
174 Format: <int>
175 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
176 debug output. Bits in debug_layer correspond to a
177 _COMPONENT in an ACPI source file, e.g.,
178 #define _COMPONENT ACPI_PCI_COMPONENT
179 Bits in debug_level correspond to a level in
180 ACPI_DEBUG_PRINT statements, e.g.,
181 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
182 The debug_level mask defaults to "info". See
183 Documentation/acpi/debug.txt for more information about
184 debug layers and levels.
186 Enable processor driver info messages:
187 acpi.debug_layer=0x20000000
188 Enable PCI/PCI interrupt routing info messages:
189 acpi.debug_layer=0x400000
190 Enable AML "Debug" output, i.e., stores to the Debug
191 object while interpreting AML:
192 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
193 Enable all messages related to ACPI hardware:
194 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
196 Some values produce so much output that the system is
197 unusable. The "log_buf_len" parameter may be useful
198 if you need to capture more output.
200 acpi_display_output= [HW,ACPI]
201 acpi_display_output=vendor
202 acpi_display_output=video
203 See above.
205 acpi_irq_balance [HW,ACPI]
206 ACPI will balance active IRQs
207 default in APIC mode
209 acpi_irq_nobalance [HW,ACPI]
210 ACPI will not move active IRQs (default)
211 default in PIC mode
213 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
214 Format: <irq>,<irq>...
216 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
217 use by PCI
218 Format: <irq>,<irq>...
220 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
222 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
223 Format: To spoof as Windows 98: ="Microsoft Windows"
225 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
226 acpi_osi="string1" # add string1 -- only one string
227 acpi_osi="!string2" # remove built-in string2
228 acpi_osi= # disable all strings
230 acpi_pm_good [X86]
231 Override the pmtimer bug detection: force the kernel
232 to assume that this machine's pmtimer latches its value
233 and always returns good values.
235 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
236 Format: { level | edge | high | low }
238 acpi_serialize [HW,ACPI] force serialization of AML methods
240 acpi_skip_timer_override [HW,ACPI]
241 Recognize and ignore IRQ0/pin2 Interrupt Override.
242 For broken nForce2 BIOS resulting in XT-PIC timer.
244 acpi_sleep= [HW,ACPI] Sleep options
245 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
246 old_ordering, s4_nonvs, sci_force_enable }
247 See Documentation/power/video.txt for information on
248 s3_bios and s3_mode.
249 s3_beep is for debugging; it makes the PC's speaker beep
250 as soon as the kernel's real-mode entry point is called.
251 s4_nohwsig prevents ACPI hardware signature from being
252 used during resume from hibernation.
253 old_ordering causes the ACPI 1.0 ordering of the _PTS
254 control method, with respect to putting devices into
255 low power states, to be enforced (the ACPI 2.0 ordering
256 of _PTS is used by default).
257 s4_nonvs prevents the kernel from saving/restoring the
258 ACPI NVS memory during hibernation.
259 sci_force_enable causes the kernel to set SCI_EN directly
260 on resume from S1/S3 (which is against the ACPI spec,
261 but some broken systems don't work without it).
263 acpi_use_timer_override [HW,ACPI]
264 Use timer override. For some broken Nvidia NF5 boards
265 that require a timer override, but don't have HPET
267 acpi_enforce_resources= [ACPI]
268 { strict | lax | no }
269 Check for resource conflicts between native drivers
270 and ACPI OperationRegions (SystemIO and SystemMemory
271 only). IO ports and memory declared in ACPI might be
272 used by the ACPI subsystem in arbitrary AML code and
273 can interfere with legacy drivers.
274 strict (default): access to resources claimed by ACPI
275 is denied; legacy drivers trying to access reserved
276 resources will fail to bind to device using them.
277 lax: access to resources claimed by ACPI is allowed;
278 legacy drivers trying to access reserved resources
279 will bind successfully but a warning message is logged.
280 no: ACPI OperationRegions are not marked as reserved,
281 no further checks are performed.
283 ad1848= [HW,OSS]
284 Format: <io>,<irq>,<dma>,<dma2>,<type>
286 add_efi_memmap [EFI; X86] Include EFI memory map in
287 kernel's map of available physical RAM.
289 advansys= [HW,SCSI]
290 See header of drivers/scsi/advansys.c.
292 advwdt= [HW,WDT] Advantech WDT
293 Format: <iostart>,<iostop>
295 aedsp16= [HW,OSS] Audio Excel DSP 16
296 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
297 See also header of sound/oss/aedsp16.c.
299 agp= [AGP]
300 { off | try_unsupported }
301 off: disable AGP support
302 try_unsupported: try to drive unsupported chipsets
303 (may crash computer or cause data corruption)
305 aha152x= [HW,SCSI]
306 See Documentation/scsi/aha152x.txt.
308 aha1542= [HW,SCSI]
309 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
311 aic7xxx= [HW,SCSI]
312 See Documentation/scsi/aic7xxx.txt.
314 aic79xx= [HW,SCSI]
315 See Documentation/scsi/aic79xx.txt.
317 alignment= [KNL,ARM]
318 Allow the default userspace alignment fault handler
319 behaviour to be specified. Bit 0 enables warnings,
320 bit 1 enables fixups, and bit 2 sends a segfault.
322 amd_iommu= [HW,X86-84]
323 Pass parameters to the AMD IOMMU driver in the system.
324 Possible values are:
325 fullflush - enable flushing of IO/TLB entries when
326 they are unmapped. Otherwise they are
327 flushed before they will be reused, which
328 is a lot of faster
329 off - do not initialize any AMD IOMMU found in
330 the system
332 amijoy.map= [HW,JOY] Amiga joystick support
333 Map of devices attached to JOY0DAT and JOY1DAT
334 Format: <a>,<b>
335 See also Documentation/kernel/input/joystick.txt
337 analog.map= [HW,JOY] Analog joystick and gamepad support
338 Specifies type or capabilities of an analog joystick
339 connected to one of 16 gameports
340 Format: <type1>,<type2>,..<type16>
342 apc= [HW,SPARC]
343 Power management functions (SPARCstation-4/5 + deriv.)
344 Format: noidle
345 Disable APC CPU standby support. SPARCstation-Fox does
346 not play well with APC CPU idle - disable it if you have
347 APC and your system crashes randomly.
349 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
350 Change the output verbosity whilst booting
351 Format: { quiet (default) | verbose | debug }
352 Change the amount of debugging information output
353 when initialising the APIC and IO-APIC components.
355 autoconf= [IPV6]
356 See Documentation/networking/ipv6.txt.
358 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
359 Limit apic dumping. The parameter defines the maximal
360 number of local apics being dumped. Also it is possible
361 to set it to "all" by meaning -- no limit here.
362 Format: { 1 (default) | 2 | ... | all }.
363 The parameter valid if only apic=debug or
364 apic=verbose is specified.
365 Example: apic=debug show_lapic=all
367 apm= [APM] Advanced Power Management
368 See header of arch/x86/kernel/apm_32.c.
370 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
371 Format: <io>,<irq>,<nodeID>
373 ataflop= [HW,M68k]
375 atarimouse= [HW,MOUSE] Atari Mouse
377 atascsi= [HW,SCSI] Atari SCSI
379 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
380 EzKey and similar keyboards
382 atkbd.reset= [HW] Reset keyboard during initialization
384 atkbd.set= [HW] Select keyboard code set
385 Format: <int> (2 = AT (default), 3 = PS/2)
387 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
388 keyboards
390 atkbd.softraw= [HW] Choose between synthetic and real raw mode
391 Format: <bool> (0 = real, 1 = synthetic (default))
393 atkbd.softrepeat= [HW]
394 Use software keyboard repeat
396 autotest [IA64]
398 baycom_epp= [HW,AX25]
399 Format: <io>,<mode>
401 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
402 Format: <io>,<mode>
403 See header of drivers/net/hamradio/baycom_par.c.
405 baycom_ser_fdx= [HW,AX25]
406 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
407 Format: <io>,<irq>,<mode>[,<baud>]
408 See header of drivers/net/hamradio/baycom_ser_fdx.c.
410 baycom_ser_hdx= [HW,AX25]
411 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
412 Format: <io>,<irq>,<mode>
413 See header of drivers/net/hamradio/baycom_ser_hdx.c.
415 boot_delay= Milliseconds to delay each printk during boot.
416 Values larger than 10 seconds (10000) are changed to
417 no delay (0).
418 Format: integer
420 bootmem_debug [KNL] Enable bootmem allocator debug messages.
422 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
423 bttv.radio= Most important insmod options are available as
424 kernel args too.
425 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
426 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
428 BusLogic= [HW,SCSI]
429 See drivers/scsi/BusLogic.c, comment before function
430 BusLogic_ParseDriverOptions().
432 c101= [NET] Moxa C101 synchronous serial card
434 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
435 Sometimes CPU hardware bugs make them report the cache
436 size incorrectly. The kernel will attempt work arounds
437 to fix known problems, but for some CPUs it is not
438 possible to determine what the correct size should be.
439 This option provides an override for these situations.
441 capability.disable=
442 [SECURITY] Disable capabilities. This would normally
443 be used only if an alternative security model is to be
444 configured. Potentially dangerous and should only be
445 used if you are entirely sure of the consequences.
447 ccw_timeout_log [S390]
448 See Documentation/s390/CommonIO for details.
450 cgroup_disable= [KNL] Disable a particular controller
451 Format: {name of the controller(s) to disable}
452 {Currently supported controllers - "memory"}
454 checkreqprot [SELINUX] Set initial checkreqprot flag value.
455 Format: { "0" | "1" }
456 See security/selinux/Kconfig help text.
457 0 -- check protection applied by kernel (includes
458 any implied execute protection).
459 1 -- check protection requested by application.
460 Default value is set via a kernel config option.
461 Value can be changed at runtime via
462 /selinux/checkreqprot.
464 cio_ignore= [S390]
465 See Documentation/s390/CommonIO for details.
467 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
468 [Deprecated]
469 Forces specified clocksource (if available) to be used
470 when calculating gettimeofday(). If specified
471 clocksource is not available, it defaults to PIT.
472 Format: { pit | tsc | cyclone | pmtmr }
474 clocksource= [GENERIC_TIME] Override the default clocksource
475 Format: <string>
476 Override the default clocksource and use the clocksource
477 with the name specified.
478 Some clocksource names to choose from, depending on
479 the platform:
480 [all] jiffies (this is the base, fallback clocksource)
481 [ACPI] acpi_pm
482 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
483 pxa_timer,timer3,32k_counter,timer0_1
484 [AVR32] avr32
485 [X86-32] pit,hpet,tsc,vmi-timer;
486 scx200_hrt on Geode; cyclone on IBM x440
487 [MIPS] MIPS
488 [PARISC] cr16
489 [S390] tod
490 [SH] SuperH
491 [SPARC64] tick
492 [X86-64] hpet,tsc
494 clearcpuid=BITNUM [X86]
495 Disable CPUID feature X for the kernel. See
496 arch/x86/include/asm/cpufeature.h for the valid bit
497 numbers. Note the Linux specific bits are not necessarily
498 stable over kernel options, but the vendor specific
499 ones should be.
500 Also note that user programs calling CPUID directly
501 or using the feature without checking anything
502 will still see it. This just prevents it from
503 being used by the kernel or shown in /proc/cpuinfo.
504 Also note the kernel might malfunction if you disable
505 some critical bits.
507 cmo_free_hint= [PPC] Format: { yes | no }
508 Specify whether pages are marked as being inactive
509 when they are freed. This is used in CMO environments
510 to determine OS memory pressure for page stealing by
511 a hypervisor.
512 Default: yes
514 code_bytes [X86] How many bytes of object code to print
515 in an oops report.
516 Range: 0 - 8192
517 Default: 64
519 com20020= [HW,NET] ARCnet - COM20020 chipset
520 Format:
521 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
523 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
524 Format: <io>[,<irq>]
526 com90xx= [HW,NET]
527 ARCnet - COM90xx chipset (memory-mapped buffers)
528 Format: <io>[,<irq>[,<memstart>]]
530 condev= [HW,S390] console device
531 conmode=
533 console= [KNL] Output console device and options.
535 tty<n> Use the virtual console device <n>.
537 ttyS<n>[,options]
538 ttyUSB0[,options]
539 Use the specified serial port. The options are of
540 the form "bbbbpnf", where "bbbb" is the baud rate,
541 "p" is parity ("n", "o", or "e"), "n" is number of
542 bits, and "f" is flow control ("r" for RTS or
543 omit it). Default is "9600n8".
545 See Documentation/serial-console.txt for more
546 information. See
547 Documentation/networking/netconsole.txt for an
548 alternative.
550 uart[8250],io,<addr>[,options]
551 uart[8250],mmio,<addr>[,options]
552 Start an early, polled-mode console on the 8250/16550
553 UART at the specified I/O port or MMIO address,
554 switching to the matching ttyS device later. The
555 options are the same as for ttyS, above.
557 If the device connected to the port is not a TTY but a braille
558 device, prepend "brl," before the device type, for instance
559 console=brl,ttyS0
560 For now, only VisioBraille is supported.
562 consoleblank= [KNL] The console blank (screen saver) timeout in
563 seconds. Defaults to 10*60 = 10mins. A value of 0
564 disables the blank timer.
566 coredump_filter=
567 [KNL] Change the default value for
568 /proc/<pid>/coredump_filter.
569 See also Documentation/filesystems/proc.txt.
571 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
572 Format:
573 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
575 crashkernel=nn[KMG]@ss[KMG]
576 [KNL] Reserve a chunk of physical memory to
577 hold a kernel to switch to with kexec on panic.
579 crashkernel=range1:size1[,range2:size2,...][@offset]
580 [KNL] Same as above, but depends on the memory
581 in the running system. The syntax of range is
582 start-[end] where start and end are both
583 a memory unit (amount[KMG]). See also
584 Documentation/kdump/kdump.txt for a example.
586 cs89x0_dma= [HW,NET]
587 Format: <dma>
589 cs89x0_media= [HW,NET]
590 Format: { rj45 | aui | bnc }
592 dasd= [HW,NET]
593 See header of drivers/s390/block/dasd_devmap.c.
595 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
596 (one device per port)
597 Format: <port#>,<type>
598 See also Documentation/input/joystick-parport.txt
600 debug [KNL] Enable kernel debugging (events log level).
602 debug_locks_verbose=
603 [KNL] verbose self-tests
604 Format=<0|1>
605 Print debugging info while doing the locking API
606 self-tests.
607 We default to 0 (no extra messages), setting it to
608 1 will print _a lot_ more information - normally
609 only useful to kernel developers.
611 debug_objects [KNL] Enable object debugging
613 no_debug_objects
614 [KNL] Disable object debugging
616 debugpat [X86] Enable PAT debugging
618 decnet.addr= [HW,NET]
619 Format: <area>[,<node>]
620 See also Documentation/networking/decnet.txt.
622 default_hugepagesz=
623 [same as hugepagesz=] The size of the default
624 HugeTLB page size. This is the size represented by
625 the legacy /proc/ hugepages APIs, used for SHM, and
626 default size when mounting hugetlbfs filesystems.
627 Defaults to the default architecture's huge page size
628 if not specified.
630 dhash_entries= [KNL]
631 Set number of hash buckets for dentry cache.
633 digi= [HW,SERIAL]
634 IO parameters + enable/disable command.
636 digiepca= [HW,SERIAL]
637 See drivers/char/README.epca and
638 Documentation/serial/digiepca.txt.
640 disable= [IPV6]
641 See Documentation/networking/ipv6.txt.
643 disable_ipv6= [IPV6]
644 See Documentation/networking/ipv6.txt.
646 disable_mtrr_cleanup [X86]
647 The kernel tries to adjust MTRR layout from continuous
648 to discrete, to make X server driver able to add WB
649 entry later. This parameter disables that.
651 disable_mtrr_trim [X86, Intel and AMD only]
652 By default the kernel will trim any uncacheable
653 memory out of your available memory pool based on
654 MTRR settings. This parameter disables that behavior,
655 possibly causing your machine to run very slowly.
657 disable_timer_pin_1 [X86]
658 Disable PIN 1 of APIC timer
659 Can be useful to work around chipset bugs.
661 dmasound= [HW,OSS] Sound subsystem buffers
663 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
664 this option disables the debugging code at boot.
666 dma_debug_entries=<number>
667 This option allows to tune the number of preallocated
668 entries for DMA-API debugging code. One entry is
669 required per DMA-API allocation. Use this if the
670 DMA-API debugging code disables itself because the
671 architectural default is too low.
673 dma_debug_driver=<driver_name>
674 With this option the DMA-API debugging driver
675 filter feature can be enabled at boot time. Just
676 pass the driver to filter for as the parameter.
677 The filter can be disabled or changed to another
678 driver later using sysfs.
680 dscc4.setup= [NET]
682 dtc3181e= [HW,SCSI]
684 dynamic_printk Enables pr_debug()/dev_dbg() calls if
685 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
686 These can also be switched on/off via
687 <debugfs>/dynamic_printk/modules
689 earlycon= [KNL] Output early console device and options.
690 uart[8250],io,<addr>[,options]
691 uart[8250],mmio,<addr>[,options]
692 Start an early, polled-mode console on the 8250/16550
693 UART at the specified I/O port or MMIO address.
694 The options are the same as for ttyS, above.
696 earlyprintk= [X86,SH,BLACKFIN]
697 earlyprintk=vga
698 earlyprintk=serial[,ttySn[,baudrate]]
699 earlyprintk=ttySn[,baudrate]
700 earlyprintk=dbgp[debugController#]
702 Append ",keep" to not disable it when the real console
703 takes over.
705 Only vga or serial or usb debug port at a time.
707 Currently only ttyS0 and ttyS1 are supported.
709 Interaction with the standard serial driver is not
710 very good.
712 The VGA output is eventually overwritten by the real
713 console.
715 eata= [HW,SCSI]
717 edd= [EDD]
718 Format: {"off" | "on" | "skip[mbr]"}
720 eisa_irq_edge= [PARISC,HW]
721 See header of drivers/parisc/eisa.c.
723 elanfreq= [X86-32]
724 See comment before function elanfreq_setup() in
725 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
727 elevator= [IOSCHED]
728 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
729 See Documentation/block/as-iosched.txt and
730 Documentation/block/deadline-iosched.txt for details.
732 elfcorehdr= [IA64,PPC,SH,X86]
733 Specifies physical address of start of kernel core
734 image elf header. Generally kexec loader will
735 pass this option to capture kernel.
736 See Documentation/kdump/kdump.txt for details.
738 enable_mtrr_cleanup [X86]
739 The kernel tries to adjust MTRR layout from continuous
740 to discrete, to make X server driver able to add WB
741 entry later. This parameter enables that.
743 enable_timer_pin_1 [X86]
744 Enable PIN 1 of APIC timer
745 Can be useful to work around chipset bugs
746 (in particular on some ATI chipsets).
747 The kernel tries to set a reasonable default.
749 enforcing [SELINUX] Set initial enforcing status.
750 Format: {"0" | "1"}
751 See security/selinux/Kconfig help text.
752 0 -- permissive (log only, no denials).
753 1 -- enforcing (deny and log).
754 Default value is 0.
755 Value can be changed at runtime via /selinux/enforce.
757 ether= [HW,NET] Ethernet cards parameters
758 This option is obsoleted by the "netdev=" option, which
759 has equivalent usage. See its documentation for details.
761 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
762 Format: <io>[,<irq>]
764 failslab=
765 fail_page_alloc=
766 fail_make_request=[KNL]
767 General fault injection mechanism.
768 Format: <interval>,<probability>,<space>,<times>
769 See also /Documentation/fault-injection/.
771 fd_mcs= [HW,SCSI]
772 See header of drivers/scsi/fd_mcs.c.
774 fdomain= [HW,SCSI]
775 See header of drivers/scsi/fdomain.c.
777 floppy= [HW]
778 See Documentation/blockdev/floppy.txt.
780 force_pal_cache_flush
781 [IA-64] Avoid check_sal_cache_flush which may hang on
782 buggy SAL_CACHE_FLUSH implementations. Using this
783 parameter will force ia64_sal_cache_flush to call
784 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
786 ftrace=[tracer]
787 [FTRACE] will set and start the specified tracer
788 as early as possible in order to facilitate early
789 boot debugging.
791 ftrace_dump_on_oops[=orig_cpu]
792 [FTRACE] will dump the trace buffers on oops.
793 If no parameter is passed, ftrace will dump
794 buffers of all CPUs, but if you pass orig_cpu, it will
795 dump only the buffer of the CPU that triggered the
796 oops.
798 ftrace_filter=[function-list]
799 [FTRACE] Limit the functions traced by the function
800 tracer at boot up. function-list is a comma separated
801 list of functions. This list can be changed at run
802 time by the set_ftrace_filter file in the debugfs
803 tracing directory.
805 ftrace_notrace=[function-list]
806 [FTRACE] Do not trace the functions specified in
807 function-list. This list can be changed at run time
808 by the set_ftrace_notrace file in the debugfs
809 tracing directory.
811 ftrace_graph_filter=[function-list]
812 [FTRACE] Limit the top level callers functions traced
813 by the function graph tracer at boot up.
814 function-list is a comma separated list of functions
815 that can be changed at run time by the
816 set_graph_function file in the debugfs tracing directory.
818 gamecon.map[2|3]=
819 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
820 support via parallel port (up to 5 devices per port)
821 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
822 See also Documentation/input/joystick-parport.txt
824 gamma= [HW,DRM]
826 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
827 Format: off | on
828 default: on
830 gcov_persist= [GCOV] When non-zero (default), profiling data for
831 kernel modules is saved and remains accessible via
832 debugfs, even when the module is unloaded/reloaded.
833 When zero, profiling data is discarded and associated
834 debugfs files are removed at module unload time.
836 gdth= [HW,SCSI]
837 See header of drivers/scsi/gdth.c.
839 gpt [EFI] Forces disk with valid GPT signature but
840 invalid Protective MBR to be treated as GPT.
842 gvp11= [HW,SCSI]
844 hashdist= [KNL,NUMA] Large hashes allocated during boot
845 are distributed across NUMA nodes. Defaults on
846 for 64bit NUMA, off otherwise.
847 Format: 0 | 1 (for off | on)
849 hcl= [IA-64] SGI's Hardware Graph compatibility layer
851 hd= [EIDE] (E)IDE hard drive subsystem geometry
852 Format: <cyl>,<head>,<sect>
854 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
855 size of <nn>. This works even on boxes that have no
856 highmem otherwise. This also works to reduce highmem
857 size on bigger boxes.
859 highres= [KNL] Enable/disable high resolution timer mode.
860 Valid parameters: "on", "off"
861 Default: "on"
863 hisax= [HW,ISDN]
864 See Documentation/isdn/README.HiSax.
866 hlt [BUGS=ARM,SH]
868 hpet= [X86-32,HPET] option to control HPET usage
869 Format: { enable (default) | disable | force |
870 verbose }
871 disable: disable HPET and use PIT instead
872 force: allow force enabled of undocumented chips (ICH4,
873 VIA, nVidia)
874 verbose: show contents of HPET registers during setup
876 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
877 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
878 On x86-64 and powerpc, this option can be specified
879 multiple times interleaved with hugepages= to reserve
880 huge pages of different sizes. Valid pages sizes on
881 x86-64 are 2M (when the CPU supports "pse") and 1G
882 (when the CPU supports the "pdpe1gb" cpuinfo flag)
883 Note that 1GB pages can only be allocated at boot time
884 using hugepages= and not freed afterwards.
886 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
887 terminal devices. Valid values: 0..8
888 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
889 If specified, z/VM IUCV HVC accepts connections
890 from listed z/VM user IDs only.
892 i2c_bus= [HW] Override the default board specific I2C bus speed
893 or register an additional I2C bus that is not
894 registered from board initialization code.
895 Format:
896 <bus_id>,<clkrate>
898 i8042.debug [HW] Toggle i8042 debug mode
899 i8042.direct [HW] Put keyboard port into non-translated mode
900 i8042.dumbkbd [HW] Pretend that controller can only read data from
901 keyboard and cannot control its state
902 (Don't attempt to blink the leds)
903 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
904 i8042.nokbd [HW] Don't check/create keyboard port
905 i8042.noloop [HW] Disable the AUX Loopback command while probing
906 for the AUX port
907 i8042.nomux [HW] Don't check presence of an active multiplexing
908 controller
909 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
910 controllers
911 i8042.panicblink=
912 [HW] Frequency with which keyboard LEDs should blink
913 when kernel panics (default is 0.5 sec)
914 i8042.reset [HW] Reset the controller during init and cleanup
915 i8042.unlock [HW] Unlock (ignore) the keylock
917 i810= [HW,DRM]
919 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
920 indicates that the driver is running on unsupported
921 hardware.
922 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
923 does not match list of supported models.
924 i8k.power_status
925 [HW] Report power status in /proc/i8k
926 (disabled by default)
927 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
928 capability is set.
930 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
931 See Documentation/mca.txt.
933 icn= [HW,ISDN]
934 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
936 ide-core.nodma= [HW] (E)IDE subsystem
937 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
938 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
939 .cdrom .chs .ignore_cable are additional options
940 See Documentation/ide/ide.txt.
942 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
943 Claim all unknown PCI IDE storage controllers.
945 idle= [X86]
946 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
947 Poll forces a polling idle loop that can slightly
948 improve the performance of waking up a idle CPU, but
949 will use a lot of power and make the system run hot.
950 Not recommended.
951 idle=mwait: On systems which support MONITOR/MWAIT but
952 the kernel chose to not use it because it doesn't save
953 as much power as a normal idle loop, use the
954 MONITOR/MWAIT idle loop anyways. Performance should be
955 the same as idle=poll.
956 idle=halt: Halt is forced to be used for CPU idle.
957 In such case C2/C3 won't be used again.
958 idle=nomwait: Disable mwait for CPU C-states
960 ignore_loglevel [KNL]
961 Ignore loglevel setting - this will print /all/
962 kernel messages to the console. Useful for debugging.
964 ihash_entries= [KNL]
965 Set number of hash buckets for inode cache.
967 ima_audit= [IMA]
968 Format: { "0" | "1" }
969 0 -- integrity auditing messages. (Default)
970 1 -- enable informational integrity auditing messages.
972 ima_hash= [IMA]
973 Format: { "sha1" | "md5" }
974 default: "sha1"
976 ima_tcb [IMA]
977 Load a policy which meets the needs of the Trusted
978 Computing Base. This means IMA will measure all
979 programs exec'd, files mmap'd for exec, and all files
980 opened for read by uid=0.
982 in2000= [HW,SCSI]
983 See header of drivers/scsi/in2000.c.
985 init= [KNL]
986 Format: <full_path>
987 Run specified binary instead of /sbin/init as init
988 process.
990 initcall_debug [KNL] Trace initcalls as they are executed. Useful
991 for working out where the kernel is dying during
992 startup.
994 initrd= [BOOT] Specify the location of the initial ramdisk
996 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
997 Format: <irq>
999 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1000 on
1001 Enable intel iommu driver.
1002 off
1003 Disable intel iommu driver.
1004 igfx_off [Default Off]
1005 By default, gfx is mapped as normal device. If a gfx
1006 device has a dedicated DMAR unit, the DMAR unit is
1007 bypassed by not enabling DMAR with this option. In
1008 this case, gfx device will use physical address for
1009 DMA.
1010 forcedac [x86_64]
1011 With this option iommu will not optimize to look
1012 for io virtual address below 32 bit forcing dual
1013 address cycle on pci bus for cards supporting greater
1014 than 32 bit addressing. The default is to look
1015 for translation below 32 bit and if not available
1016 then look in the higher range.
1017 strict [Default Off]
1018 With this option on every unmap_single operation will
1019 result in a hardware IOTLB flush operation as opposed
1020 to batching them for performance.
1022 inttest= [IA64]
1024 iomem= Disable strict checking of access to MMIO memory
1025 strict regions from userspace.
1026 relaxed
1028 iommu= [x86]
1029 off
1030 force
1031 noforce
1032 biomerge
1033 panic
1034 nopanic
1035 merge
1036 nomerge
1037 forcesac
1038 soft
1039 pt [x86, IA64]
1041 io7= [HW] IO7 for Marvel based alpha systems
1042 See comment before marvel_specify_io7 in
1043 arch/alpha/kernel/core_marvel.c.
1045 io_delay= [X86] I/O delay method
1046 0x80
1047 Standard port 0x80 based delay
1048 0xed
1049 Alternate port 0xed based delay (needed on some systems)
1050 udelay
1051 Simple two microseconds delay
1052 none
1053 No delay
1055 ip= [IP_PNP]
1056 See Documentation/filesystems/nfs/nfsroot.txt.
1058 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1059 See comment before ip2_setup() in
1060 drivers/char/ip2/ip2base.c.
1062 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1063 See header of drivers/scsi/ips.c.
1065 irqfixup [HW]
1066 When an interrupt is not handled search all handlers
1067 for it. Intended to get systems with badly broken
1068 firmware running.
1070 irqpoll [HW]
1071 When an interrupt is not handled search all handlers
1072 for it. Also check all handlers each timer
1073 interrupt. Intended to get systems with badly broken
1074 firmware running.
1076 isapnp= [ISAPNP]
1077 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1079 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1080 Format:
1081 <cpu number>,...,<cpu number>
1082 or
1083 <cpu number>-<cpu number>
1084 (must be a positive range in ascending order)
1085 or a mixture
1086 <cpu number>,...,<cpu number>-<cpu number>
1088 This option can be used to specify one or more CPUs
1089 to isolate from the general SMP balancing and scheduling
1090 algorithms. You can move a process onto or off an
1091 "isolated" CPU via the CPU affinity syscalls or cpuset.
1092 <cpu number> begins at 0 and the maximum value is
1093 "number of CPUs in system - 1".
1095 This option is the preferred way to isolate CPUs. The
1096 alternative -- manually setting the CPU mask of all
1097 tasks in the system -- can cause problems and
1098 suboptimal load balancer performance.
1100 iucv= [HW,NET]
1102 js= [HW,JOY] Analog joystick
1103 See Documentation/input/joystick.txt.
1105 keepinitrd [HW,ARM]
1107 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1108 specifies the amount of memory usable by the kernel
1109 for non-movable allocations. The requested amount is
1110 spread evenly throughout all nodes in the system. The
1111 remaining memory in each node is used for Movable
1112 pages. In the event, a node is too small to have both
1113 kernelcore and Movable pages, kernelcore pages will
1114 take priority and other nodes will have a larger number
1115 of kernelcore pages. The Movable zone is used for the
1116 allocation of pages that may be reclaimed or moved
1117 by the page migration subsystem. This means that
1118 HugeTLB pages may not be allocated from this zone.
1119 Note that allocations like PTEs-from-HighMem still
1120 use the HighMem zone if it exists, and the Normal
1121 zone if it does not.
1123 kgdboc= [HW] kgdb over consoles.
1124 Requires a tty driver that supports console polling.
1125 (only serial supported for now)
1126 Format: <serial_device>[,baud]
1128 kmac= [MIPS] korina ethernet MAC address.
1129 Configure the RouterBoard 532 series on-chip
1130 Ethernet adapter MAC address.
1132 kmemleak= [KNL] Boot-time kmemleak enable/disable
1133 Valid arguments: on, off
1134 Default: on
1136 kstack=N [X86] Print N words from the kernel stack
1137 in oops dumps.
1139 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1140 Default is 0 (don't ignore, but inject #GP)
1142 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1143 Default is 1 (enabled)
1145 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1146 Default is 0 (off)
1148 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1149 for all guests.
1150 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1152 kvm-intel.bypass_guest_pf=
1153 [KVM,Intel] Disables bypassing of guest page faults
1154 on Intel chips. Default is 1 (enabled)
1156 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1157 (virtualized MMU) support on capable Intel chips.
1158 Default is 1 (enabled)
1160 kvm-intel.emulate_invalid_guest_state=
1161 [KVM,Intel] Enable emulation of invalid guest states
1162 Default is 0 (disabled)
1164 kvm-intel.flexpriority=
1165 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1166 Default is 1 (enabled)
1168 kvm-intel.unrestricted_guest=
1169 [KVM,Intel] Disable unrestricted guest feature
1170 (virtualized real and unpaged mode) on capable
1171 Intel chips. Default is 1 (enabled)
1173 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1174 feature (tagged TLBs) on capable Intel chips.
1175 Default is 1 (enabled)
1177 l2cr= [PPC]
1179 l3cr= [PPC]
1181 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1182 disabled it.
1184 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1185 in C2 power state.
1187 libata.dma= [LIBATA] DMA control
1188 libata.dma=0 Disable all PATA and SATA DMA
1189 libata.dma=1 PATA and SATA Disk DMA only
1190 libata.dma=2 ATAPI (CDROM) DMA only
1191 libata.dma=4 Compact Flash DMA only
1192 Combinations also work, so libata.dma=3 enables DMA
1193 for disks and CDROMs, but not CFs.
1195 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1196 libata.ignore_hpa=0 keep BIOS limits (default)
1197 libata.ignore_hpa=1 ignore limits, using full disk
1199 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1200 when set.
1201 Format: <int>
1203 libata.force= [LIBATA] Force configurations. The format is comma
1204 separated list of "[ID:]VAL" where ID is
1205 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1206 matching port, link or device. Basically, it matches
1207 the ATA ID string printed on console by libata. If
1208 the whole ID part is omitted, the last PORT and DEVICE
1209 values are used. If ID hasn't been specified yet, the
1210 configuration applies to all ports, links and devices.
1212 If only DEVICE is omitted, the parameter applies to
1213 the port and all links and devices behind it. DEVICE
1214 number of 0 either selects the first device or the
1215 first fan-out link behind PMP device. It does not
1216 select the host link. DEVICE number of 15 selects the
1217 host link and device attached to it.
1219 The VAL specifies the configuration to force. As long
1220 as there's no ambiguity shortcut notation is allowed.
1221 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1222 The following configurations can be forced.
1224 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1225 Any ID with matching PORT is used.
1227 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1229 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1230 udma[/][16,25,33,44,66,100,133] notation is also
1231 allowed.
1233 * [no]ncq: Turn on or off NCQ.
1235 * nohrst, nosrst, norst: suppress hard, soft
1236 and both resets.
1238 If there are multiple matching configurations changing
1239 the same attribute, the last one is used.
1241 lmb=debug [KNL] Enable lmb debug messages.
1243 load_ramdisk= [RAM] List of ramdisks to load from floppy
1244 See Documentation/blockdev/ramdisk.txt.
1246 lockd.nlm_grace_period=P [NFS] Assign grace period.
1247 Format: <integer>
1249 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1250 Format: <integer>
1252 lockd.nlm_timeout=T [NFS] Assign timeout value.
1253 Format: <integer>
1255 lockd.nlm_udpport=M [NFS] Assign UDP port.
1256 Format: <integer>
1258 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1259 Format: <irq>
1261 loglevel= All Kernel Messages with a loglevel smaller than the
1262 console loglevel will be printed to the console. It can
1263 also be changed with klogd or other programs. The
1264 loglevels are defined as follows:
1266 0 (KERN_EMERG) system is unusable
1267 1 (KERN_ALERT) action must be taken immediately
1268 2 (KERN_CRIT) critical conditions
1269 3 (KERN_ERR) error conditions
1270 4 (KERN_WARNING) warning conditions
1271 5 (KERN_NOTICE) normal but significant condition
1272 6 (KERN_INFO) informational
1273 7 (KERN_DEBUG) debug-level messages
1275 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1276 Format: { n | nk | nM }
1277 n must be a power of two. The default size
1278 is set in the kernel config file.
1280 logo.nologo [FB] Disables display of the built-in Linux logo.
1281 This may be used to provide more screen space for
1282 kernel log messages and is useful when debugging
1283 kernel boot problems.
1285 lp=0 [LP] Specify parallel ports to use, e.g,
1286 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1287 lp=reset first parallel port). 'lp=0' disables the
1288 lp=auto printer driver. 'lp=reset' (which can be
1289 specified in addition to the ports) causes
1290 attached printers to be reset. Using
1291 lp=port1,port2,... specifies the parallel ports
1292 to associate lp devices with, starting with
1293 lp0. A port specification may be 'none' to skip
1294 that lp device, or a parport name such as
1295 'parport0'. Specifying 'lp=auto' instead of a
1296 port specification list means that device IDs
1297 from each port should be examined, to see if
1298 an IEEE 1284-compliant printer is attached; if
1299 so, the driver will manage that printer.
1300 See also header of drivers/char/lp.c.
1302 lpj=n [KNL]
1303 Sets loops_per_jiffy to given constant, thus avoiding
1304 time-consuming boot-time autodetection (up to 250 ms per
1305 CPU). 0 enables autodetection (default). To determine
1306 the correct value for your kernel, boot with normal
1307 autodetection and see what value is printed. Note that
1308 on SMP systems the preset will be applied to all CPUs,
1309 which is likely to cause problems if your CPUs need
1310 significantly divergent settings. An incorrect value
1311 will cause delays in the kernel to be wrong, leading to
1312 unpredictable I/O errors and other breakage. Although
1313 unlikely, in the extreme case this might damage your
1314 hardware.
1316 ltpc= [NET]
1317 Format: <io>,<irq>,<dma>
1319 mac5380= [HW,SCSI] Format:
1320 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1322 machvec= [IA64] Force the use of a particular machine-vector
1323 (machvec) in a generic kernel.
1324 Example: machvec=hpzx1_swiotlb
1326 machtype= [Loongson] Share the same kernel image file between different
1327 yeeloong laptop.
1328 Example: machtype=lemote-yeeloong-2f-7inch
1330 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1331 than or equal to this physical address is ignored.
1333 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1334 should make use of. maxcpus=n : n >= 0 limits the
1335 kernel to using 'n' processors. n=0 is a special case,
1336 it is equivalent to "nosmp", which also disables
1337 the IO APIC.
1339 max_loop= [LOOP] Maximum number of loopback devices that can
1340 be mounted
1341 Format: <1-256>
1343 max_luns= [SCSI] Maximum number of LUNs to probe.
1344 Should be between 1 and 2^32-1.
1346 max_report_luns=
1347 [SCSI] Maximum number of LUNs received.
1348 Should be between 1 and 16384.
1350 mcatest= [IA-64]
1352 mce [X86-32] Machine Check Exception
1354 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1356 md= [HW] RAID subsystems devices and level
1357 See Documentation/md.txt.
1359 mdacon= [MDA]
1360 Format: <first>,<last>
1361 Specifies range of consoles to be captured by the MDA.
1363 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1364 Amount of memory to be used when the kernel is not able
1365 to see the whole system memory or for test.
1366 [X86-32] Use together with memmap= to avoid physical
1367 address space collisions. Without memmap= PCI devices
1368 could be placed at addresses belonging to unused RAM.
1370 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1371 memory.
1373 memchunk=nn[KMG]
1374 [KNL,SH] Allow user to override the default size for
1375 per-device physically contiguous DMA buffers.
1377 memmap=exactmap [KNL,X86] Enable setting of an exact
1378 E820 memory map, as specified by the user.
1379 Such memmap=exactmap lines can be constructed based on
1380 BIOS output or other requirements. See the memmap=nn@ss
1381 option description.
1383 memmap=nn[KMG]@ss[KMG]
1384 [KNL] Force usage of a specific region of memory
1385 Region of memory to be used, from ss to ss+nn.
1387 memmap=nn[KMG]#ss[KMG]
1388 [KNL,ACPI] Mark specific memory as ACPI data.
1389 Region of memory to be used, from ss to ss+nn.
1391 memmap=nn[KMG]$ss[KMG]
1392 [KNL,ACPI] Mark specific memory as reserved.
1393 Region of memory to be used, from ss to ss+nn.
1394 Example: Exclude memory from 0x18690000-0x1869ffff
1395 memmap=64K$0x18690000
1396 or
1397 memmap=0x10000$0x18690000
1399 memory_corruption_check=0/1 [X86]
1400 Some BIOSes seem to corrupt the first 64k of
1401 memory when doing things like suspend/resume.
1402 Setting this option will scan the memory
1403 looking for corruption. Enabling this will
1404 both detect corruption and prevent the kernel
1405 from using the memory being corrupted.
1406 However, its intended as a diagnostic tool; if
1407 repeatable BIOS-originated corruption always
1408 affects the same memory, you can use memmap=
1409 to prevent the kernel from using that memory.
1411 memory_corruption_check_size=size [X86]
1412 By default it checks for corruption in the low
1413 64k, making this memory unavailable for normal
1414 use. Use this parameter to scan for
1415 corruption in more or less memory.
1417 memory_corruption_check_period=seconds [X86]
1418 By default it checks for corruption every 60
1419 seconds. Use this parameter to check at some
1420 other rate. 0 disables periodic checking.
1422 memtest= [KNL,X86] Enable memtest
1423 Format: <integer>
1424 default : 0 <disable>
1425 Specifies the number of memtest passes to be
1426 performed. Each pass selects another test
1427 pattern from a given set of patterns. Memtest
1428 fills the memory with this pattern, validates
1429 memory contents and reserves bad memory
1430 regions that are detected.
1432 meye.*= [HW] Set MotionEye Camera parameters
1433 See Documentation/video4linux/meye.txt.
1435 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1436 Multi-Function General Purpose Timers on AMD Geode
1437 platforms.
1439 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1440 the BIOS has incorrectly applied a workaround. TinyBIOS
1441 version 0.98 is known to be affected, 0.99 fixes the
1442 problem by letting the user disable the workaround.
1444 mga= [HW,DRM]
1446 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1447 physical address is ignored.
1449 mini2440= [ARM,HW,KNL]
1450 Format:[0..2][b][c][t]
1451 Default: "0tb"
1452 MINI2440 configuration specification:
1453 0 - The attached screen is the 3.5" TFT
1454 1 - The attached screen is the 7" TFT
1455 2 - The VGA Shield is attached (1024x768)
1456 Leaving out the screen size parameter will not load
1457 the TFT driver, and the framebuffer will be left
1458 unconfigured.
1459 b - Enable backlight. The TFT backlight pin will be
1460 linked to the kernel VESA blanking code and a GPIO
1461 LED. This parameter is not necessary when using the
1462 VGA shield.
1463 c - Enable the s3c camera interface.
1464 t - Reserved for enabling touchscreen support. The
1465 touchscreen support is not enabled in the mainstream
1466 kernel as of 2.6.30, a preliminary port can be found
1467 in the "bleeding edge" mini2440 support kernel at
1468 http://repo.or.cz/w/linux-2.6/mini2440.git
1470 mminit_loglevel=
1471 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1472 parameter allows control of the logging verbosity for
1473 the additional memory initialisation checks. A value
1474 of 0 disables mminit logging and a level of 4 will
1475 log everything. Information is printed at KERN_DEBUG
1476 so loglevel=8 may also need to be specified.
1478 mousedev.tap_time=
1479 [MOUSE] Maximum time between finger touching and
1480 leaving touchpad surface for touch to be considered
1481 a tap and be reported as a left button click (for
1482 touchpads working in absolute mode only).
1483 Format: <msecs>
1484 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1485 reporting absolute coordinates, such as tablets
1486 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1487 reporting absolute coordinates, such as tablets
1489 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1490 is similar to kernelcore except it specifies the
1491 amount of memory used for migratable allocations.
1492 If both kernelcore and movablecore is specified,
1493 then kernelcore will be at *least* the specified
1494 value but may be more. If movablecore on its own
1495 is specified, the administrator must be careful
1496 that the amount of memory usable for all allocations
1497 is not too small.
1499 mpu401= [HW,OSS]
1500 Format: <io>,<irq>
1502 MTD_Partition= [MTD]
1503 Format: <name>,<region-number>,<size>,<offset>
1505 MTD_Region= [MTD] Format:
1506 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1508 mtdparts= [MTD]
1509 See drivers/mtd/cmdlinepart.c.
1511 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1513 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1515 boundary - index of last SLC block on Flex-OneNAND.
1516 The remaining blocks are configured as MLC blocks.
1517 lock - Configure if Flex-OneNAND boundary should be locked.
1518 Once locked, the boundary cannot be changed.
1519 1 indicates lock status, 0 indicates unlock status.
1521 mtdset= [ARM]
1522 ARM/S3C2412 JIVE boot control
1524 See arch/arm/mach-s3c2412/mach-jive.c
1526 mtouchusb.raw_coordinates=
1527 [HW] Make the MicroTouch USB driver use raw coordinates
1528 ('y', default) or cooked coordinates ('n')
1530 mtrr_chunk_size=nn[KMG] [X86]
1531 used for mtrr cleanup. It is largest continuous chunk
1532 that could hold holes aka. UC entries.
1534 mtrr_gran_size=nn[KMG] [X86]
1535 Used for mtrr cleanup. It is granularity of mtrr block.
1536 Default is 1.
1537 Large value could prevent small alignment from
1538 using up MTRRs.
1540 mtrr_spare_reg_nr=n [X86]
1541 Format: <integer>
1542 Range: 0,7 : spare reg number
1543 Default : 1
1544 Used for mtrr cleanup. It is spare mtrr entries number.
1545 Set to 2 or more if your graphical card needs more.
1547 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1549 NCR_D700= [HW,SCSI]
1550 See header of drivers/scsi/NCR_D700.c.
1552 ncr5380= [HW,SCSI]
1554 ncr53c400= [HW,SCSI]
1556 ncr53c400a= [HW,SCSI]
1558 ncr53c406a= [HW,SCSI]
1560 ncr53c8xx= [HW,SCSI]
1562 netdev= [NET] Network devices parameters
1563 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1564 Note that mem_start is often overloaded to mean
1565 something different and driver-specific.
1566 This usage is only documented in each driver source
1567 file if at all.
1569 nf_conntrack.acct=
1570 [NETFILTER] Enable connection tracking flow accounting
1571 0 to disable accounting
1572 1 to enable accounting
1573 Default value depends on CONFIG_NF_CT_ACCT that is
1574 going to be removed in 2.6.29.
1576 nfsaddrs= [NFS]
1577 See Documentation/filesystems/nfs/nfsroot.txt.
1579 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1580 See Documentation/filesystems/nfs/nfsroot.txt.
1582 nfs.callback_tcpport=
1583 [NFS] set the TCP port on which the NFSv4 callback
1584 channel should listen.
1586 nfs.cache_getent=
1587 [NFS] sets the pathname to the program which is used
1588 to update the NFS client cache entries.
1590 nfs.cache_getent_timeout=
1591 [NFS] sets the timeout after which an attempt to
1592 update a cache entry is deemed to have failed.
1594 nfs.idmap_cache_timeout=
1595 [NFS] set the maximum lifetime for idmapper cache
1596 entries.
1598 nfs.enable_ino64=
1599 [NFS] enable 64-bit inode numbers.
1600 If zero, the NFS client will fake up a 32-bit inode
1601 number for the readdir() and stat() syscalls instead
1602 of returning the full 64-bit number.
1603 The default is to return 64-bit inode numbers.
1605 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1606 when a NMI is triggered.
1607 Format: [state][,regs][,debounce][,die]
1609 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1610 Format: [panic,][num]
1611 Valid num: 0,1,2
1612 0 - turn nmi_watchdog off
1613 1 - use the IO-APIC timer for the NMI watchdog
1614 2 - use the local APIC for the NMI watchdog using
1615 a performance counter. Note: This will use one
1616 performance counter and the local APIC's performance
1617 vector.
1618 When panic is specified, panic when an NMI watchdog
1619 timeout occurs.
1620 This is useful when you use a panic=... timeout and
1621 need the box quickly up again.
1622 Instead of 1 and 2 it is possible to use the following
1623 symbolic names: lapic and ioapic
1624 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1626 netpoll.carrier_timeout=
1627 [NET] Specifies amount of time (in seconds) that
1628 netpoll should wait for a carrier. By default netpoll
1629 waits 4 seconds.
1631 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1632 emulation library even if a 387 maths coprocessor
1633 is present.
1635 no_console_suspend
1636 [HW] Never suspend the console
1637 Disable suspending of consoles during suspend and
1638 hibernate operations. Once disabled, debugging
1639 messages can reach various consoles while the rest
1640 of the system is being put to sleep (ie, while
1641 debugging driver suspend/resume hooks). This may
1642 not work reliably with all consoles, but is known
1643 to work with serial and VGA consoles.
1645 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1646 caches in the slab allocator. Saves per-node memory,
1647 but will impact performance.
1649 noalign [KNL,ARM]
1651 noapic [SMP,APIC] Tells the kernel to not make use of any
1652 IOAPICs that may be present in the system.
1654 nobats [PPC] Do not use BATs for mapping kernel lowmem
1655 on "Classic" PPC cores.
1657 nocache [ARM]
1659 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1661 nodelayacct [KNL] Disable per-task delay accounting
1663 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1665 nodsp [SH] Disable hardware DSP at boot time.
1667 noefi [X86] Disable EFI runtime services support.
1669 noexec [IA-64]
1671 noexec [X86]
1672 On X86-32 available only on PAE configured kernels.
1673 noexec=on: enable non-executable mappings (default)
1674 noexec=off: disable non-executable mappings
1676 noexec32 [X86-64]
1677 This affects only 32-bit executables.
1678 noexec32=on: enable non-executable mappings (default)
1679 read doesn't imply executable mappings
1680 noexec32=off: disable non-executable mappings
1681 read implies executable mappings
1683 nofpu [SH] Disable hardware FPU at boot time.
1685 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1686 register save and restore. The kernel will only save
1687 legacy floating-point registers on task switch.
1689 noxsave [BUGS=X86] Disables x86 extended register state save
1690 and restore using xsave. The kernel will fallback to
1691 enabling legacy floating-point and sse state.
1693 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1694 wfi(ARM) instruction doesn't work correctly and not to
1695 use it. This is also useful when using JTAG debugger.
1697 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1698 instruction doesn't work correctly and not to
1699 use it.
1701 no_file_caps Tells the kernel not to honor file capabilities. The
1702 only way then for a file to be executed with privilege
1703 is to be setuid root or executed by root.
1705 nohalt [IA-64] Tells the kernel not to use the power saving
1706 function PAL_HALT_LIGHT when idle. This increases
1707 power-consumption. On the positive side, it reduces
1708 interrupt wake-up latency, which may improve performance
1709 in certain environments such as networked servers or
1710 real-time systems.
1712 nohz= [KNL] Boottime enable/disable dynamic ticks
1713 Valid arguments: on, off
1714 Default: on
1716 noiotrap [SH] Disables trapped I/O port accesses.
1718 noirqdebug [X86-32] Disables the code which attempts to detect and
1719 disable unhandled interrupt sources.
1721 no_timer_check [X86,APIC] Disables the code which tests for
1722 broken timer IRQ sources.
1724 noisapnp [ISAPNP] Disables ISA PnP code.
1726 noinitrd [RAM] Tells the kernel not to load any configured
1727 initial RAM disk.
1729 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1730 remapping.
1732 nointroute [IA-64]
1734 nojitter [IA64] Disables jitter checking for ITC timers.
1736 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1738 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1740 noltlbs [PPC] Do not use large page/tlb entries for kernel
1741 lowmem mapping on PPC40x.
1743 nomca [IA-64] Disable machine check abort handling
1745 nomce [X86-32] Machine Check Exception
1747 nomfgpt [X86-32] Disable Multi-Function General Purpose
1748 Timer usage (for AMD Geode machines).
1750 nopat [X86] Disable PAT (page attribute table extension of
1751 pagetables) support.
1753 norandmaps Don't use address space randomization. Equivalent to
1754 echo 0 > /proc/sys/kernel/randomize_va_space
1756 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1758 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1759 with UP alternatives
1761 noresidual [PPC] Don't use residual data on PReP machines.
1763 noresume [SWSUSP] Disables resume and restores original swap
1764 space.
1766 no-scroll [VGA] Disables scrollback.
1767 This is required for the Braillex ib80-piezo Braille
1768 reader made by F.H. Papenmeier (Germany).
1770 nosbagart [IA-64]
1772 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1774 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1775 and disable the IO APIC. legacy for "maxcpus=0".
1777 nosoftlockup [KNL] Disable the soft-lockup detector.
1779 noswapaccount [KNL] Disable accounting of swap in memory resource
1780 controller. (See Documentation/cgroups/memory.txt)
1782 nosync [HW,M68K] Disables sync negotiation for all devices.
1784 notsc [BUGS=X86-32] Disable Time Stamp Counter
1786 nousb [USB] Disable the USB subsystem
1788 nowb [ARM]
1790 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1792 nptcg= [IA64] Override max number of concurrent global TLB
1793 purges which is reported from either PAL_VM_SUMMARY or
1794 SAL PALO.
1796 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1797 could support. nr_cpus=n : n >= 1 limits the kernel to
1798 supporting 'n' processors. Later in runtime you can not
1799 use hotplug cpu feature to put more cpu back to online.
1800 just like you compile the kernel NR_CPUS=n
1802 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1804 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1805 one of ['zone', 'node', 'default'] can be specified
1806 This can be set from sysctl after boot.
1807 See Documentation/sysctl/vm.txt for details.
1809 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1810 See Documentation/debugging-via-ohci1394.txt for more
1811 info.
1813 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1814 Rather than timing out after 20 ms if an EC
1815 command is not properly ACKed, override the length
1816 of the timeout. We have interrupts disabled while
1817 waiting for the ACK, so if this is set too high
1818 interrupts *may* be lost!
1820 omap_mux= [OMAP] Override bootloader pin multiplexing.
1821 Format: <mux_mode0.mode_name=value>...
1822 For example, to override I2C bus2:
1823 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1825 opl3= [HW,OSS]
1826 Format: <io>
1828 oprofile.timer= [HW]
1829 Use timer interrupt instead of performance counters
1831 oprofile.cpu_type= Force an oprofile cpu type
1832 This might be useful if you have an older oprofile
1833 userland or if you want common events.
1834 Format: { arch_perfmon }
1835 arch_perfmon: [X86] Force use of architectural
1836 perfmon on Intel CPUs instead of the
1837 CPU specific event set.
1839 osst= [HW,SCSI] SCSI Tape Driver
1840 Format: <buffer_size>,<write_threshold>
1841 See also Documentation/scsi/st.txt.
1843 panic= [KNL] Kernel behaviour on panic
1844 Format: <timeout>
1846 parkbd.port= [HW] Parallel port number the keyboard adapter is
1847 connected to, default is 0.
1848 Format: <parport#>
1849 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1850 0 for XT, 1 for AT (default is AT).
1851 Format: <mode>
1853 parport= [HW,PPT] Specify parallel ports. 0 disables.
1854 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1855 Use 'auto' to force the driver to use any
1856 IRQ/DMA settings detected (the default is to
1857 ignore detected IRQ/DMA settings because of
1858 possible conflicts). You can specify the base
1859 address, IRQ, and DMA settings; IRQ and DMA
1860 should be numbers, or 'auto' (for using detected
1861 settings on that particular port), or 'nofifo'
1862 (to avoid using a FIFO even if it is detected).
1863 Parallel ports are assigned in the order they
1864 are specified on the command line, starting
1865 with parport0.
1867 parport_init_mode= [HW,PPT]
1868 Configure VIA parallel port to operate in
1869 a specific mode. This is necessary on Pegasos
1870 computer where firmware has no options for setting
1871 up parallel port mode and sets it to spp.
1872 Currently this function knows 686a and 8231 chips.
1873 Format: [spp|ps2|epp|ecp|ecpepp]
1875 pas2= [HW,OSS] Format:
1876 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1878 pas16= [HW,SCSI]
1879 See header of drivers/scsi/pas16.c.
1881 pause_on_oops=
1882 Halt all CPUs after the first oops has been printed for
1883 the specified number of seconds. This is to be used if
1884 your oopses keep scrolling off the screen.
1886 pcbit= [HW,ISDN]
1888 pcd. [PARIDE]
1889 See header of drivers/block/paride/pcd.c.
1890 See also Documentation/blockdev/paride.txt.
1892 pci=option[,option...] [PCI] various PCI subsystem options:
1893 earlydump [X86] dump PCI config space before the kernel
1894 changes anything
1895 off [X86] don't probe for the PCI bus
1896 bios [X86-32] force use of PCI BIOS, don't access
1897 the hardware directly. Use this if your machine
1898 has a non-standard PCI host bridge.
1899 nobios [X86-32] disallow use of PCI BIOS, only direct
1900 hardware access methods are allowed. Use this
1901 if you experience crashes upon bootup and you
1902 suspect they are caused by the BIOS.
1903 conf1 [X86] Force use of PCI Configuration
1904 Mechanism 1.
1905 conf2 [X86] Force use of PCI Configuration
1906 Mechanism 2.
1907 noaer [PCIE] If the PCIEAER kernel config parameter is
1908 enabled, this kernel boot option can be used to
1909 disable the use of PCIE advanced error reporting.
1910 nodomains [PCI] Disable support for multiple PCI
1911 root domains (aka PCI segments, in ACPI-speak).
1912 nommconf [X86] Disable use of MMCONFIG for PCI
1913 Configuration
1914 check_enable_amd_mmconf [X86] check for and enable
1915 properly configured MMIO access to PCI
1916 config space on AMD family 10h CPU
1917 nomsi [MSI] If the PCI_MSI kernel config parameter is
1918 enabled, this kernel boot option can be used to
1919 disable the use of MSI interrupts system-wide.
1920 noioapicquirk [APIC] Disable all boot interrupt quirks.
1921 Safety option to keep boot IRQs enabled. This
1922 should never be necessary.
1923 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1924 primary IO-APIC for bridges that cannot disable
1925 boot IRQs. This fixes a source of spurious IRQs
1926 when the system masks IRQs.
1927 noioapicreroute [APIC] Disable workaround that uses the
1928 boot IRQ equivalent of an IRQ that connects to
1929 a chipset where boot IRQs cannot be disabled.
1930 The opposite of ioapicreroute.
1931 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1932 routing table. These calls are known to be buggy
1933 on several machines and they hang the machine
1934 when used, but on other computers it's the only
1935 way to get the interrupt routing table. Try
1936 this option if the kernel is unable to allocate
1937 IRQs or discover secondary PCI buses on your
1938 motherboard.
1939 rom [X86] Assign address space to expansion ROMs.
1940 Use with caution as certain devices share
1941 address decoders between ROMs and other
1942 resources.
1943 norom [X86] Do not assign address space to
1944 expansion ROMs that do not already have
1945 BIOS assigned address ranges.
1946 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1947 assigned automatically to PCI devices. You can
1948 make the kernel exclude IRQs of your ISA cards
1949 this way.
1950 pirqaddr=0xAAAAA [X86] Specify the physical address
1951 of the PIRQ table (normally generated
1952 by the BIOS) if it is outside the
1953 F0000h-100000h range.
1954 lastbus=N [X86] Scan all buses thru bus #N. Can be
1955 useful if the kernel is unable to find your
1956 secondary buses and you want to tell it
1957 explicitly which ones they are.
1958 assign-busses [X86] Always assign all PCI bus
1959 numbers ourselves, overriding
1960 whatever the firmware may have done.
1961 usepirqmask [X86] Honor the possible IRQ mask stored
1962 in the BIOS $PIR table. This is needed on
1963 some systems with broken BIOSes, notably
1964 some HP Pavilion N5400 and Omnibook XE3
1965 notebooks. This will have no effect if ACPI
1966 IRQ routing is enabled.
1967 noacpi [X86] Do not use ACPI for IRQ routing
1968 or for PCI scanning.
1969 use_crs [X86] Use PCI host bridge window information
1970 from ACPI. On BIOSes from 2008 or later, this
1971 is enabled by default. If you need to use this,
1972 please report a bug.
1973 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1974 If you need to use this, please report a bug.
1975 routeirq Do IRQ routing for all PCI devices.
1976 This is normally done in pci_enable_device(),
1977 so this option is a temporary workaround
1978 for broken drivers that don't call it.
1979 skip_isa_align [X86] do not align io start addr, so can
1980 handle more pci cards
1981 firmware [ARM] Do not re-enumerate the bus but instead
1982 just use the configuration from the
1983 bootloader. This is currently used on
1984 IXP2000 systems where the bus has to be
1985 configured a certain way for adjunct CPUs.
1986 noearly [X86] Don't do any early type 1 scanning.
1987 This might help on some broken boards which
1988 machine check when some devices' config space
1989 is read. But various workarounds are disabled
1990 and some IOMMU drivers will not work.
1991 bfsort Sort PCI devices into breadth-first order.
1992 This sorting is done to get a device
1993 order compatible with older (<= 2.4) kernels.
1994 nobfsort Don't sort PCI devices into breadth-first order.
1995 cbiosize=nn[KMG] The fixed amount of bus space which is
1996 reserved for the CardBus bridge's IO window.
1997 The default value is 256 bytes.
1998 cbmemsize=nn[KMG] The fixed amount of bus space which is
1999 reserved for the CardBus bridge's memory
2000 window. The default value is 64 megabytes.
2001 resource_alignment=
2002 Format:
2003 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2004 Specifies alignment and device to reassign
2005 aligned memory resources.
2006 If <order of align> is not specified,
2007 PAGE_SIZE is used as alignment.
2008 PCI-PCI bridge can be specified, if resource
2009 windows need to be expanded.
2010 ecrc= Enable/disable PCIe ECRC (transaction layer
2011 end-to-end CRC checking).
2012 bios: Use BIOS/firmware settings. This is the
2013 the default.
2014 off: Turn ECRC off
2015 on: Turn ECRC on.
2017 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2018 Management.
2019 off Disable ASPM.
2020 force Enable ASPM even on devices that claim not to support it.
2021 WARNING: Forcing ASPM on may cause system lockups.
2023 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2024 off Do not use native PCIe PME signaling.
2025 force Use native PCIe PME signaling even if the BIOS refuses
2026 to allow the kernel to control the relevant PCIe config
2027 registers.
2028 nomsi Do not use MSI for native PCIe PME signaling (this makes
2029 all PCIe root ports use INTx for everything).
2031 pcmv= [HW,PCMCIA] BadgePAD 4
2033 pd. [PARIDE]
2034 See Documentation/blockdev/paride.txt.
2036 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2037 boot time.
2038 Format: { 0 | 1 }
2039 See arch/parisc/kernel/pdc_chassis.c
2041 percpu_alloc= Select which percpu first chunk allocator to use.
2042 Currently supported values are "embed" and "page".
2043 Archs may support subset or none of the selections.
2044 See comments in mm/percpu.c for details on each
2045 allocator. This parameter is primarily for debugging
2046 and performance comparison.
2048 pf. [PARIDE]
2049 See Documentation/blockdev/paride.txt.
2051 pg. [PARIDE]
2052 See Documentation/blockdev/paride.txt.
2054 pirq= [SMP,APIC] Manual mp-table setup
2055 See Documentation/x86/i386/IO-APIC.txt.
2057 plip= [PPT,NET] Parallel port network link
2058 Format: { parport<nr> | timid | 0 }
2059 See also Documentation/parport.txt.
2061 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2062 Override pmtimer IOPort with a hex value.
2063 e.g. pmtmr=0x508
2065 pnp.debug [PNP]
2066 Enable PNP debug messages. This depends on the
2067 CONFIG_PNP_DEBUG_MESSAGES option.
2069 pnpacpi= [ACPI]
2070 { off }
2072 pnpbios= [ISAPNP]
2073 { on | off | curr | res | no-curr | no-res }
2075 pnp_reserve_irq=
2076 [ISAPNP] Exclude IRQs for the autoconfiguration
2078 pnp_reserve_dma=
2079 [ISAPNP] Exclude DMAs for the autoconfiguration
2081 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2082 Ranges are in pairs (I/O port base and size).
2084 pnp_reserve_mem=
2085 [ISAPNP] Exclude memory regions for the
2086 autoconfiguration.
2087 Ranges are in pairs (memory base and size).
2089 ports= [IP_VS_FTP] IPVS ftp helper module
2090 Default is 21.
2091 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2092 may be specified.
2093 Format: <port>,<port>....
2095 print-fatal-signals=
2096 [KNL] debug: print fatal signals
2098 If enabled, warn about various signal handling
2099 related application anomalies: too many signals,
2100 too many POSIX.1 timers, fatal signals causing a
2101 coredump - etc.
2103 If you hit the warning due to signal overflow,
2104 you might want to try "ulimit -i unlimited".
2106 default: off.
2108 printk.time= Show timing data prefixed to each printk message line
2109 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2111 processor.max_cstate= [HW,ACPI]
2112 Limit processor to maximum C-state
2113 max_cstate=9 overrides any DMI blacklist limit.
2115 processor.nocst [HW,ACPI]
2116 Ignore the _CST method to determine C-states,
2117 instead using the legacy FADT method
2119 profile= [KNL] Enable kernel profiling via /proc/profile
2120 Format: [schedule,]<number>
2121 Param: "schedule" - profile schedule points.
2122 Param: <number> - step/bucket size as a power of 2 for
2123 statistical time based profiling.
2124 Param: "sleep" - profile D-state sleeping (millisecs).
2125 Requires CONFIG_SCHEDSTATS
2126 Param: "kvm" - profile VM exits.
2128 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2129 before loading.
2130 See Documentation/blockdev/ramdisk.txt.
2132 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2133 probe for; one of (bare|imps|exps|lifebook|any).
2134 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2135 per second.
2136 psmouse.resetafter= [HW,MOUSE]
2137 Try to reset the device after so many bad packets
2138 (0 = never).
2139 psmouse.resolution=
2140 [HW,MOUSE] Set desired mouse resolution, in dpi.
2141 psmouse.smartscroll=
2142 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2143 0 = disabled, 1 = enabled (default).
2145 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2146 Format:
2147 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2149 pt. [PARIDE]
2150 See Documentation/blockdev/paride.txt.
2152 pty.legacy_count=
2153 [KNL] Number of legacy pty's. Overwrites compiled-in
2154 default number.
2156 quiet [KNL] Disable most log messages
2158 r128= [HW,DRM]
2160 raid= [HW,RAID]
2161 See Documentation/md.txt.
2163 ramdisk_blocksize= [RAM]
2164 See Documentation/blockdev/ramdisk.txt.
2166 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2167 See Documentation/blockdev/ramdisk.txt.
2169 rcupdate.blimit= [KNL,BOOT]
2170 Set maximum number of finished RCU callbacks to process
2171 in one batch.
2173 rcupdate.qhimark= [KNL,BOOT]
2174 Set threshold of queued
2175 RCU callbacks over which batch limiting is disabled.
2177 rcupdate.qlowmark= [KNL,BOOT]
2178 Set threshold of queued RCU callbacks below which
2179 batch limiting is re-enabled.
2181 rdinit= [KNL]
2182 Format: <full_path>
2183 Run specified binary instead of /init from the ramdisk,
2184 used for early userspace startup. See initrd.
2186 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2187 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2188 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2190 relax_domain_level=
2191 [KNL, SMP] Set scheduler's default relax_domain_level.
2192 See Documentation/cgroups/cpusets.txt.
2194 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2196 reservetop= [X86-32]
2197 Format: nn[KMG]
2198 Reserves a hole at the top of the kernel virtual
2199 address space.
2201 reset_devices [KNL] Force drivers to reset the underlying device
2202 during initialization.
2204 resume= [SWSUSP]
2205 Specify the partition device for software suspend
2207 resume_offset= [SWSUSP]
2208 Specify the offset from the beginning of the partition
2209 given by "resume=" at which the swap header is located,
2210 in <PAGE_SIZE> units (needed only for swap files).
2211 See Documentation/power/swsusp-and-swap-files.txt
2213 retain_initrd [RAM] Keep initrd memory after extraction
2215 rhash_entries= [KNL,NET]
2216 Set number of hash buckets for route cache
2218 riscom8= [HW,SERIAL]
2219 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2221 ro [KNL] Mount root device read-only on boot
2223 root= [KNL] Root filesystem
2225 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2226 mount the root filesystem
2228 rootflags= [KNL] Set root filesystem mount option string
2230 rootfstype= [KNL] Set root filesystem type
2232 rootwait [KNL] Wait (indefinitely) for root device to show up.
2233 Useful for devices that are detected asynchronously
2234 (e.g. USB and MMC devices).
2236 rw [KNL] Mount root device read-write on boot
2238 S [KNL] Run init in single mode
2240 sa1100ir [NET]
2241 See drivers/net/irda/sa1100_ir.c.
2243 sbni= [NET] Granch SBNI12 leased line adapter
2245 sched_debug [KNL] Enables verbose scheduler debug messages.
2247 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2248 Format: <io>[,<timeout>[,<isapnp>]]
2250 scsi_debug_*= [SCSI]
2251 See drivers/scsi/scsi_debug.c.
2253 scsi_default_dev_flags=
2254 [SCSI] SCSI default device flags
2255 Format: <integer>
2257 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2258 Format: <vendor>:<model>:<flags>
2259 (flags are integer value)
2261 scsi_logging_level= [SCSI] a bit mask of logging levels
2262 See drivers/scsi/scsi_logging.h for bits. Also
2263 settable via sysctl at dev.scsi.logging_level
2264 (/proc/sys/dev/scsi/logging_level).
2265 There is also a nice 'scsi_logging_level' script in the
2266 S390-tools package, available for download at
2267 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2269 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2270 discovered. async scans them in kernel threads,
2271 allowing boot to proceed. none ignores them, expecting
2272 user space to do the scan.
2274 security= [SECURITY] Choose a security module to enable at boot.
2275 If this boot parameter is not specified, only the first
2276 security module asking for security registration will be
2277 loaded. An invalid security module name will be treated
2278 as if no module has been chosen.
2280 selinux= [SELINUX] Disable or enable SELinux at boot time.
2281 Format: { "0" | "1" }
2282 See security/selinux/Kconfig help text.
2283 0 -- disable.
2284 1 -- enable.
2285 Default value is set via kernel config option.
2286 If enabled at boot time, /selinux/disable can be used
2287 later to disable prior to initial policy load.
2289 serialnumber [BUGS=X86-32]
2291 shapers= [NET]
2292 Maximal number of shapers.
2294 show_msr= [x86] show boot-time MSR settings
2295 Format: { <integer> }
2296 Show boot-time (BIOS-initialized) MSR settings.
2297 The parameter means the number of CPUs to show,
2298 for example 1 means boot CPU only.
2300 sim710= [SCSI,HW]
2301 See header of drivers/scsi/sim710.c.
2303 simeth= [IA-64]
2304 simscsi=
2306 slram= [HW,MTD]
2308 slub_debug[=options[,slabs]] [MM, SLUB]
2309 Enabling slub_debug allows one to determine the
2310 culprit if slab objects become corrupted. Enabling
2311 slub_debug can create guard zones around objects and
2312 may poison objects when not in use. Also tracks the
2313 last alloc / free. For more information see
2314 Documentation/vm/slub.txt.
2316 slub_max_order= [MM, SLUB]
2317 Determines the maximum allowed order for slabs.
2318 A high setting may cause OOMs due to memory
2319 fragmentation. For more information see
2320 Documentation/vm/slub.txt.
2322 slub_min_objects= [MM, SLUB]
2323 The minimum number of objects per slab. SLUB will
2324 increase the slab order up to slub_max_order to
2325 generate a sufficiently large slab able to contain
2326 the number of objects indicated. The higher the number
2327 of objects the smaller the overhead of tracking slabs
2328 and the less frequently locks need to be acquired.
2329 For more information see Documentation/vm/slub.txt.
2331 slub_min_order= [MM, SLUB]
2332 Determines the mininum page order for slabs. Must be
2333 lower than slub_max_order.
2334 For more information see Documentation/vm/slub.txt.
2336 slub_nomerge [MM, SLUB]
2337 Disable merging of slabs with similar size. May be
2338 necessary if there is some reason to distinguish
2339 allocs to different slabs. Debug options disable
2340 merging on their own.
2341 For more information see Documentation/vm/slub.txt.
2343 smart2= [HW]
2344 Format: <io1>[,<io2>[,...,<io8>]]
2346 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2347 attempt to substitute SMP alternatives once at boot.
2349 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2350 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2351 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2352 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2353 smsc-ircc2.ircc_irq= [HW] IRQ line
2354 smsc-ircc2.ircc_dma= [HW] DMA channel
2355 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2356 0: Toshiba Satellite 1800 (GP data pin select)
2357 1: Fast pin select (default)
2358 2: ATC IRMode
2360 snd-ad1816a= [HW,ALSA]
2362 snd-ad1848= [HW,ALSA]
2364 snd-ali5451= [HW,ALSA]
2366 snd-als100= [HW,ALSA]
2368 snd-als4000= [HW,ALSA]
2370 snd-azt2320= [HW,ALSA]
2372 snd-cmi8330= [HW,ALSA]
2374 snd-cmipci= [HW,ALSA]
2376 snd-cs4231= [HW,ALSA]
2378 snd-cs4232= [HW,ALSA]
2380 snd-cs4236= [HW,ALSA]
2382 snd-cs4281= [HW,ALSA]
2384 snd-cs46xx= [HW,ALSA]
2386 snd-dt019x= [HW,ALSA]
2388 snd-dummy= [HW,ALSA]
2390 snd-emu10k1= [HW,ALSA]
2392 snd-ens1370= [HW,ALSA]
2394 snd-ens1371= [HW,ALSA]
2396 snd-es968= [HW,ALSA]
2398 snd-es1688= [HW,ALSA]
2400 snd-es18xx= [HW,ALSA]
2402 snd-es1938= [HW,ALSA]
2404 snd-es1968= [HW,ALSA]
2406 snd-fm801= [HW,ALSA]
2408 snd-gusclassic= [HW,ALSA]
2410 snd-gusextreme= [HW,ALSA]
2412 snd-gusmax= [HW,ALSA]
2414 snd-hdsp= [HW,ALSA]
2416 snd-ice1712= [HW,ALSA]
2418 snd-intel8x0= [HW,ALSA]
2420 snd-interwave= [HW,ALSA]
2422 snd-interwave-stb=
2423 [HW,ALSA]
2425 snd-korg1212= [HW,ALSA]
2427 snd-maestro3= [HW,ALSA]
2429 snd-mpu401= [HW,ALSA]
2431 snd-mtpav= [HW,ALSA]
2433 snd-nm256= [HW,ALSA]
2435 snd-opl3sa2= [HW,ALSA]
2437 snd-opti92x-ad1848=
2438 [HW,ALSA]
2440 snd-opti92x-cs4231=
2441 [HW,ALSA]
2443 snd-opti93x= [HW,ALSA]
2445 snd-pmac= [HW,ALSA]
2447 snd-rme32= [HW,ALSA]
2449 snd-rme96= [HW,ALSA]
2451 snd-rme9652= [HW,ALSA]
2453 snd-sb8= [HW,ALSA]
2455 snd-sb16= [HW,ALSA]
2457 snd-sbawe= [HW,ALSA]
2459 snd-serial= [HW,ALSA]
2461 snd-sgalaxy= [HW,ALSA]
2463 snd-sonicvibes= [HW,ALSA]
2465 snd-sun-amd7930=
2466 [HW,ALSA]
2468 snd-sun-cs4231= [HW,ALSA]
2470 snd-trident= [HW,ALSA]
2472 snd-usb-audio= [HW,ALSA,USB]
2474 snd-via82xx= [HW,ALSA]
2476 snd-virmidi= [HW,ALSA]
2478 snd-wavefront= [HW,ALSA]
2480 snd-ymfpci= [HW,ALSA]
2482 softlockup_panic=
2483 [KNL] Should the soft-lockup detector generate panics.
2485 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2486 See Documentation/sonypi.txt
2488 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2489 See Documentation/serial/specialix.txt.
2491 spia_io_base= [HW,MTD]
2492 spia_fio_base=
2493 spia_pedr=
2494 spia_peddr=
2496 sscape= [HW,OSS]
2497 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2499 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2500 See Documentation/scsi/st.txt.
2502 stacktrace [FTRACE]
2503 Enabled the stack tracer on boot up.
2505 sti= [PARISC,HW]
2506 Format: <num>
2507 Set the STI (builtin display/keyboard on the HP-PARISC
2508 machines) console (graphic card) which should be used
2509 as the initial boot-console.
2510 See also comment in drivers/video/console/sticore.c.
2512 sti_font= [HW]
2513 See comment in drivers/video/console/sticore.c.
2515 stifb= [HW]
2516 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2518 sunrpc.min_resvport=
2519 sunrpc.max_resvport=
2520 [NFS,SUNRPC]
2521 SunRPC servers often require that client requests
2522 originate from a privileged port (i.e. a port in the
2523 range 0 < portnr < 1024).
2524 An administrator who wishes to reserve some of these
2525 ports for other uses may adjust the range that the
2526 kernel's sunrpc client considers to be privileged
2527 using these two parameters to set the minimum and
2528 maximum port values.
2530 sunrpc.pool_mode=
2531 [NFS]
2532 Control how the NFS server code allocates CPUs to
2533 service thread pools. Depending on how many NICs
2534 you have and where their interrupts are bound, this
2535 option will affect which CPUs will do NFS serving.
2536 Note: this parameter cannot be changed while the
2537 NFS server is running.
2539 auto the server chooses an appropriate mode
2540 automatically using heuristics
2541 global a single global pool contains all CPUs
2542 percpu one pool for each CPU
2543 pernode one pool for each NUMA node (equivalent
2544 to global on non-NUMA machines)
2546 sunrpc.tcp_slot_table_entries=
2547 sunrpc.udp_slot_table_entries=
2548 [NFS,SUNRPC]
2549 Sets the upper limit on the number of simultaneous
2550 RPC calls that can be sent from the client to a
2551 server. Increasing these values may allow you to
2552 improve throughput, but will also increase the
2553 amount of memory reserved for use by the client.
2555 swiotlb= [IA-64] Number of I/O TLB slabs
2557 switches= [HW,M68k]
2559 sym53c416= [HW,SCSI]
2560 See header of drivers/scsi/sym53c416.c.
2562 sysrq_always_enabled
2563 [KNL]
2564 Ignore sysrq setting - this boot parameter will
2565 neutralize any effect of /proc/sys/kernel/sysrq.
2566 Useful for debugging.
2568 t128= [HW,SCSI]
2569 See header of drivers/scsi/t128.c.
2571 tdfx= [HW,DRM]
2573 test_suspend= [SUSPEND]
2574 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2575 standby suspend) as the system sleep state to briefly
2576 enter during system startup. The system is woken from
2577 this state using a wakeup-capable RTC alarm.
2579 thash_entries= [KNL,NET]
2580 Set number of hash buckets for TCP connection
2582 thermal.act= [HW,ACPI]
2583 -1: disable all active trip points in all thermal zones
2584 <degrees C>: override all lowest active trip points
2586 thermal.crt= [HW,ACPI]
2587 -1: disable all critical trip points in all thermal zones
2588 <degrees C>: override all critical trip points
2590 thermal.nocrt= [HW,ACPI]
2591 Set to disable actions on ACPI thermal zone
2592 critical and hot trip points.
2594 thermal.off= [HW,ACPI]
2595 1: disable ACPI thermal control
2597 thermal.psv= [HW,ACPI]
2598 -1: disable all passive trip points
2599 <degrees C>: override all passive trip points to this
2600 value
2602 thermal.tzp= [HW,ACPI]
2603 Specify global default ACPI thermal zone polling rate
2604 <deci-seconds>: poll all this frequency
2605 0: no polling (default)
2607 tmscsim= [HW,SCSI]
2608 See comment before function dc390_setup() in
2609 drivers/scsi/tmscsim.c.
2611 topology= [S390]
2612 Format: {off | on}
2613 Specify if the kernel should make use of the cpu
2614 topology informations if the hardware supports these.
2615 The scheduler will make use of these informations and
2616 e.g. base its process migration decisions on it.
2617 Default is off.
2619 tp720= [HW,PS2]
2621 tpm_suspend_pcr=[HW,TPM]
2622 Format: integer pcr id
2623 Specify that at suspend time, the tpm driver
2624 should extend the specified pcr with zeros,
2625 as a workaround for some chips which fail to
2626 flush the last written pcr on TPM_SaveState.
2627 This will guarantee that all the other pcrs
2628 are saved.
2630 trace_buf_size=nn[KMG]
2631 [FTRACE] will set tracing buffer size.
2633 trace_event=[event-list]
2634 [FTRACE] Set and start specified trace events in order
2635 to facilitate early boot debugging.
2636 See also Documentation/trace/events.txt
2638 trix= [HW,OSS] MediaTrix AudioTrix Pro
2639 Format:
2640 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2642 tsc= Disable clocksource-must-verify flag for TSC.
2643 Format: <string>
2644 [x86] reliable: mark tsc clocksource as reliable, this
2645 disables clocksource verification at runtime.
2646 Used to enable high-resolution timer mode on older
2647 hardware, and in virtualized environment.
2649 turbografx.map[2|3]= [HW,JOY]
2650 TurboGraFX parallel port interface
2651 Format:
2652 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2653 See also Documentation/input/joystick-parport.txt
2655 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2656 See header of drivers/scsi/u14-34f.c.
2658 uart401= [HW,OSS]
2659 Format: <io>,<irq>
2661 uart6850= [HW,OSS]
2662 Format: <io>,<irq>
2664 uhash_entries= [KNL,NET]
2665 Set number of hash buckets for UDP/UDP-Lite connections
2667 uhci-hcd.ignore_oc=
2668 [USB] Ignore overcurrent events (default N).
2669 Some badly-designed motherboards generate lots of
2670 bogus events, for ports that aren't wired to
2671 anything. Set this parameter to avoid log spamming.
2672 Note that genuine overcurrent events won't be
2673 reported either.
2675 unknown_nmi_panic
2676 [X86]
2677 Set unknown_nmi_panic=1 early on boot.
2679 usbcore.autosuspend=
2680 [USB] The autosuspend time delay (in seconds) used
2681 for newly-detected USB devices (default 2). This
2682 is the time required before an idle device will be
2683 autosuspended. Devices for which the delay is set
2684 to a negative value won't be autosuspended at all.
2686 usbcore.usbfs_snoop=
2687 [USB] Set to log all usbfs traffic (default 0 = off).
2689 usbcore.blinkenlights=
2690 [USB] Set to cycle leds on hubs (default 0 = off).
2692 usbcore.old_scheme_first=
2693 [USB] Start with the old device initialization
2694 scheme (default 0 = off).
2696 usbcore.use_both_schemes=
2697 [USB] Try the other device initialization scheme
2698 if the first one fails (default 1 = enabled).
2700 usbcore.initial_descriptor_timeout=
2701 [USB] Specifies timeout for the initial 64-byte
2702 USB_REQ_GET_DESCRIPTOR request in milliseconds
2703 (default 5000 = 5.0 seconds).
2705 usbhid.mousepoll=
2706 [USBHID] The interval which mice are to be polled at.
2708 usb-storage.delay_use=
2709 [UMS] The delay in seconds before a new device is
2710 scanned for Logical Units (default 5).
2712 usb-storage.quirks=
2713 [UMS] A list of quirks entries to supplement or
2714 override the built-in unusual_devs list. List
2715 entries are separated by commas. Each entry has
2716 the form VID:PID:Flags where VID and PID are Vendor
2717 and Product ID values (4-digit hex numbers) and
2718 Flags is a set of characters, each corresponding
2719 to a common usb-storage quirk flag as follows:
2720 a = SANE_SENSE (collect more than 18 bytes
2721 of sense data);
2722 b = BAD_SENSE (don't collect more than 18
2723 bytes of sense data);
2724 c = FIX_CAPACITY (decrease the reported
2725 device capacity by one sector);
2726 h = CAPACITY_HEURISTICS (decrease the
2727 reported device capacity by one
2728 sector if the number is odd);
2729 i = IGNORE_DEVICE (don't bind to this
2730 device);
2731 l = NOT_LOCKABLE (don't try to lock and
2732 unlock ejectable media);
2733 m = MAX_SECTORS_64 (don't transfer more
2734 than 64 sectors = 32 KB at a time);
2735 o = CAPACITY_OK (accept the capacity
2736 reported by the device);
2737 r = IGNORE_RESIDUE (the device reports
2738 bogus residue values);
2739 s = SINGLE_LUN (the device has only one
2740 Logical Unit);
2741 w = NO_WP_DETECT (don't test whether the
2742 medium is write-protected).
2743 Example: quirks=0419:aaf5:rl,0421:0433:rc
2745 userpte=
2746 [X86] Flags controlling user PTE allocations.
2748 nohigh = do not allocate PTE pages in
2749 HIGHMEM regardless of setting
2750 of CONFIG_HIGHPTE.
2752 vdso= [X86,SH]
2753 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2754 vdso=1: enable VDSO (default)
2755 vdso=0: disable VDSO mapping
2757 vdso32= [X86]
2758 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2759 vdso32=1: enable 32-bit VDSO (default)
2760 vdso32=0: disable 32-bit VDSO mapping
2762 vector= [IA-64,SMP]
2763 vector=percpu: enable percpu vector domain
2765 video= [FB] Frame buffer configuration
2766 See Documentation/fb/modedb.txt.
2768 vga= [BOOT,X86-32] Select a particular video mode
2769 See Documentation/x86/boot.txt and
2770 Documentation/svga.txt.
2771 Use vga=ask for menu.
2772 This is actually a boot loader parameter; the value is
2773 passed to the kernel using a special protocol.
2775 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2776 size of <nn>. This can be used to increase the
2777 minimum size (128MB on x86). It can also be used to
2778 decrease the size and leave more room for directly
2779 mapped kernel RAM.
2781 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2782 Format: <command>
2784 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2785 Format: <command>
2787 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2788 Format: <command>
2790 vt.cur_default= [VT] Default cursor shape.
2791 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2792 the parameters of the <Esc>[?A;B;Cc escape sequence;
2793 see VGA-softcursor.txt. Default: 2 = underline.
2795 vt.default_blu= [VT]
2796 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2797 Change the default blue palette of the console.
2798 This is a 16-member array composed of values
2799 ranging from 0-255.
2801 vt.default_grn= [VT]
2802 Format: <green0>,<green1>,<green2>,...,<green15>
2803 Change the default green palette of the console.
2804 This is a 16-member array composed of values
2805 ranging from 0-255.
2807 vt.default_red= [VT]
2808 Format: <red0>,<red1>,<red2>,...,<red15>
2809 Change the default red palette of the console.
2810 This is a 16-member array composed of values
2811 ranging from 0-255.
2813 vt.default_utf8=
2814 [VT]
2815 Format=<0|1>
2816 Set system-wide default UTF-8 mode for all tty's.
2817 Default is 1, i.e. UTF-8 mode is enabled for all
2818 newly opened terminals.
2820 vt.global_cursor_default=
2821 [VT]
2822 Format=<-1|0|1>
2823 Set system-wide default for whether a cursor
2824 is shown on new VTs. Default is -1,
2825 i.e. cursors will be created by default unless
2826 overridden by individual drivers. 0 will hide
2827 cursors, 1 will display them.
2829 waveartist= [HW,OSS]
2830 Format: <io>,<irq>,<dma>,<dma2>
2832 wd33c93= [HW,SCSI]
2833 See header of drivers/scsi/wd33c93.c.
2835 wd7000= [HW,SCSI]
2836 See header of drivers/scsi/wd7000.c.
2838 wdt= [WDT] Watchdog
2839 See Documentation/watchdog/wdt.txt.
2841 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2842 default x2apic cluster mode on platforms
2843 supporting x2apic.
2845 x86_mrst_timer= [X86-32,APBT]
2846 Choose timer option for x86 Moorestown MID platform.
2847 Two valid options are apbt timer only and lapic timer
2848 plus one apbt timer for broadcast timer.
2849 x86_mrst_timer=apbt_only | lapic_and_apbt
2851 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2852 xd_geo= See header of drivers/block/xd.c.
2854 xirc2ps_cs= [NET,PCMCIA]
2855 Format:
2856 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2858 ______________________________________________________________________
2860 TODO:
2862 Add documentation for ALSA options.
2863 Add more DRM drivers.