| blob | d4ef1330b82e0946d1150f79178db8d91950dbe4 |
1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 GCOV GCOV profiling is enabled.
52 HW Appropriate hardware is enabled.
53 IA-64 IA-64 architecture is enabled.
54 IMA Integrity measurement architecture is enabled.
55 IOSCHED More than one I/O scheduler is enabled.
56 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
57 IPV6 IPv6 support is enabled.
58 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
61 KVM Kernel Virtual Machine support is enabled.
62 LIBATA Libata driver is enabled
63 LP Printer support is enabled.
64 LOOP Loopback device support is enabled.
65 M68k M68k architecture is enabled.
66 These options have more detailed description inside of
67 Documentation/m68k/kernel-options.txt.
68 MCA MCA bus support is enabled.
69 MDA MDA console support is enabled.
70 MOUSE Appropriate mouse support is enabled.
71 MSI Message Signaled Interrupts (PCI).
72 MTD MTD (Memory Technology Device) support is enabled.
73 NET Appropriate network support is enabled.
74 NUMA NUMA support is enabled.
75 GENERIC_TIME The generic timeofday code is enabled.
76 NFS Appropriate NFS support is enabled.
77 OSS OSS sound support is enabled.
78 PV_OPS A paravirtualized kernel is enabled.
79 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
80 PARISC The PA-RISC architecture is enabled.
81 PCI PCI bus support is enabled.
82 PCIE PCI Express support is enabled.
83 PCMCIA The PCMCIA subsystem is enabled.
84 PNP Plug & Play support is enabled.
85 PPC PowerPC architecture is enabled.
86 PPT Parallel port support is enabled.
87 PS2 Appropriate PS/2 support is enabled.
88 RAM RAM disk support is enabled.
89 S390 S390 architecture is enabled.
90 SCSI Appropriate SCSI support is enabled.
91 A lot of drivers has their options described inside of
92 Documentation/scsi/.
93 SECURITY Different security models are enabled.
94 SELINUX SELinux support is enabled.
95 SERIAL Serial support is enabled.
96 SH SuperH architecture is enabled.
97 SMP The kernel is an SMP kernel.
98 SPARC Sparc architecture is enabled.
99 SWSUSP Software suspend (hibernation) is enabled.
100 SUSPEND System suspend states are enabled.
101 FTRACE Function tracing enabled.
102 TS Appropriate touchscreen support is enabled.
103 UMS USB Mass Storage support is enabled.
104 USB USB support is enabled.
105 USBHID USB Human Interface Device support is enabled.
106 V4L Video For Linux support is enabled.
107 VGA The VGA console has been enabled.
108 VT Virtual terminal support is enabled.
109 WDT Watchdog support is enabled.
110 XT IBM PC/XT MFM hard disk support is enabled.
111 X86-32 X86-32, aka i386 architecture is enabled.
112 X86-64 X86-64 architecture is enabled.
113 More X86-64 boot options can be found in
114 Documentation/x86/x86_64/boot-options.txt .
115 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
117 In addition, the following text indicates that the option:
119 BUGS= Relates to possible processor bugs on the said processor.
120 KNL Is a kernel start-up parameter.
121 BOOT Is a boot loader parameter.
123 Parameters denoted with BOOT are actually interpreted by the boot
124 loader, and have no meaning to the kernel directly.
125 Do not modify the syntax of boot loader parameters without extreme
126 need or coordination with <Documentation/x86/boot.txt>.
128 There are also arch-specific kernel-parameters not documented here.
129 See for example <Documentation/x86/x86_64/boot-options.txt>.
131 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
132 a trailing = on the name of any parameter states that that parameter will
133 be entered as an environment variable, whereas its absence indicates that
134 it will appear as a kernel argument readable via /proc/cmdline by programs
135 running once the system is up.
137 The number of kernel parameters is not limited, but the length of the
138 complete command line (parameters including spaces etc.) is limited to
139 a fixed number of characters. This limit depends on the architecture
140 and is between 256 and 4096 characters. It is defined in the file
141 ./include/asm/setup.h as COMMAND_LINE_SIZE.
144 acpi= [HW,ACPI,X86]
145 Advanced Configuration and Power Interface
146 Format: { force | off | ht | strict | noirq | rsdt }
147 force -- enable ACPI if default was off
148 off -- disable ACPI if default was on
149 noirq -- do not use ACPI for IRQ routing
150 ht -- run only enough ACPI to enable Hyper Threading
151 strict -- Be less tolerant of platforms that are not
152 strictly ACPI specification compliant.
153 rsdt -- prefer RSDT over (default) XSDT
155 See also Documentation/power/pm.txt, pci=noacpi
157 acpi_apic_instance= [ACPI, IOAPIC]
158 Format: <int>
159 2: use 2nd APIC table, if available
160 1,0: use 1st APIC table
161 default: 0
163 acpi_backlight= [HW,ACPI]
164 acpi_backlight=vendor
165 acpi_backlight=video
166 If set to vendor, prefer vendor specific driver
167 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
168 of the ACPI video.ko driver.
170 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
171 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
172 Format: <int>
173 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
174 debug output. Bits in debug_layer correspond to a
175 _COMPONENT in an ACPI source file, e.g.,
176 #define _COMPONENT ACPI_PCI_COMPONENT
177 Bits in debug_level correspond to a level in
178 ACPI_DEBUG_PRINT statements, e.g.,
179 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
180 The debug_level mask defaults to "info". See
181 Documentation/acpi/debug.txt for more information about
182 debug layers and levels.
184 Enable processor driver info messages:
185 acpi.debug_layer=0x20000000
186 Enable PCI/PCI interrupt routing info messages:
187 acpi.debug_layer=0x400000
188 Enable AML "Debug" output, i.e., stores to the Debug
189 object while interpreting AML:
190 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
191 Enable all messages related to ACPI hardware:
192 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
194 Some values produce so much output that the system is
195 unusable. The "log_buf_len" parameter may be useful
196 if you need to capture more output.
198 acpi_display_output= [HW,ACPI]
199 acpi_display_output=vendor
200 acpi_display_output=video
201 See above.
203 acpi_irq_balance [HW,ACPI]
204 ACPI will balance active IRQs
205 default in APIC mode
207 acpi_irq_nobalance [HW,ACPI]
208 ACPI will not move active IRQs (default)
209 default in PIC mode
211 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
212 Format: <irq>,<irq>...
214 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
215 use by PCI
216 Format: <irq>,<irq>...
218 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
220 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
221 Format: To spoof as Windows 98: ="Microsoft Windows"
223 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
224 acpi_osi="string1" # add string1 -- only one string
225 acpi_osi="!string2" # remove built-in string2
226 acpi_osi= # disable all strings
228 acpi_pm_good [X86]
229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
233 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
234 Format: { level | edge | high | low }
236 acpi_serialize [HW,ACPI] force serialization of AML methods
238 acpi_skip_timer_override [HW,ACPI]
239 Recognize and ignore IRQ0/pin2 Interrupt Override.
240 For broken nForce2 BIOS resulting in XT-PIC timer.
242 acpi_sleep= [HW,ACPI] Sleep options
243 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
244 old_ordering, s4_nonvs, sci_force_enable }
245 See Documentation/power/video.txt for information on
246 s3_bios and s3_mode.
247 s3_beep is for debugging; it makes the PC's speaker beep
248 as soon as the kernel's real-mode entry point is called.
249 s4_nohwsig prevents ACPI hardware signature from being
250 used during resume from hibernation.
251 old_ordering causes the ACPI 1.0 ordering of the _PTS
252 control method, with respect to putting devices into
253 low power states, to be enforced (the ACPI 2.0 ordering
254 of _PTS is used by default).
255 s4_nonvs prevents the kernel from saving/restoring the
256 ACPI NVS memory during hibernation.
257 sci_force_enable causes the kernel to set SCI_EN directly
258 on resume from S1/S3 (which is against the ACPI spec,
259 but some broken systems don't work without it).
261 acpi_use_timer_override [HW,ACPI]
262 Use timer override. For some broken Nvidia NF5 boards
263 that require a timer override, but don't have HPET
265 acpi_enforce_resources= [ACPI]
266 { strict | lax | no }
267 Check for resource conflicts between native drivers
268 and ACPI OperationRegions (SystemIO and SystemMemory
269 only). IO ports and memory declared in ACPI might be
270 used by the ACPI subsystem in arbitrary AML code and
271 can interfere with legacy drivers.
272 strict (default): access to resources claimed by ACPI
273 is denied; legacy drivers trying to access reserved
274 resources will fail to bind to device using them.
275 lax: access to resources claimed by ACPI is allowed;
276 legacy drivers trying to access reserved resources
277 will bind successfully but a warning message is logged.
278 no: ACPI OperationRegions are not marked as reserved,
279 no further checks are performed.
281 ad1848= [HW,OSS]
282 Format: <io>,<irq>,<dma>,<dma2>,<type>
284 add_efi_memmap [EFI; X86] Include EFI memory map in
285 kernel's map of available physical RAM.
287 advansys= [HW,SCSI]
288 See header of drivers/scsi/advansys.c.
290 advwdt= [HW,WDT] Advantech WDT
291 Format: <iostart>,<iostop>
293 aedsp16= [HW,OSS] Audio Excel DSP 16
294 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
295 See also header of sound/oss/aedsp16.c.
297 agp= [AGP]
298 { off | try_unsupported }
299 off: disable AGP support
300 try_unsupported: try to drive unsupported chipsets
301 (may crash computer or cause data corruption)
303 aha152x= [HW,SCSI]
304 See Documentation/scsi/aha152x.txt.
306 aha1542= [HW,SCSI]
307 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
309 aic7xxx= [HW,SCSI]
310 See Documentation/scsi/aic7xxx.txt.
312 aic79xx= [HW,SCSI]
313 See Documentation/scsi/aic79xx.txt.
315 alignment= [KNL,ARM]
316 Allow the default userspace alignment fault handler
317 behaviour to be specified. Bit 0 enables warnings,
318 bit 1 enables fixups, and bit 2 sends a segfault.
320 amd_iommu= [HW,X86-84]
321 Pass parameters to the AMD IOMMU driver in the system.
322 Possible values are:
323 fullflush - enable flushing of IO/TLB entries when
324 they are unmapped. Otherwise they are
325 flushed before they will be reused, which
326 is a lot of faster
328 amijoy.map= [HW,JOY] Amiga joystick support
329 Map of devices attached to JOY0DAT and JOY1DAT
330 Format: <a>,<b>
331 See also Documentation/kernel/input/joystick.txt
333 analog.map= [HW,JOY] Analog joystick and gamepad support
334 Specifies type or capabilities of an analog joystick
335 connected to one of 16 gameports
336 Format: <type1>,<type2>,..<type16>
338 apc= [HW,SPARC]
339 Power management functions (SPARCstation-4/5 + deriv.)
340 Format: noidle
341 Disable APC CPU standby support. SPARCstation-Fox does
342 not play well with APC CPU idle - disable it if you have
343 APC and your system crashes randomly.
345 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
346 Change the output verbosity whilst booting
347 Format: { quiet (default) | verbose | debug }
348 Change the amount of debugging information output
349 when initialising the APIC and IO-APIC components.
351 autoconf= [IPV6]
352 See Documentation/networking/ipv6.txt.
354 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
355 Limit apic dumping. The parameter defines the maximal
356 number of local apics being dumped. Also it is possible
357 to set it to "all" by meaning -- no limit here.
358 Format: { 1 (default) | 2 | ... | all }.
359 The parameter valid if only apic=debug or
360 apic=verbose is specified.
361 Example: apic=debug show_lapic=all
363 apm= [APM] Advanced Power Management
364 See header of arch/x86/kernel/apm_32.c.
366 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
367 Format: <io>,<irq>,<nodeID>
369 ataflop= [HW,M68k]
371 atarimouse= [HW,MOUSE] Atari Mouse
373 atascsi= [HW,SCSI] Atari SCSI
375 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
376 EzKey and similar keyboards
378 atkbd.reset= [HW] Reset keyboard during initialization
380 atkbd.set= [HW] Select keyboard code set
381 Format: <int> (2 = AT (default), 3 = PS/2)
383 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
384 keyboards
386 atkbd.softraw= [HW] Choose between synthetic and real raw mode
387 Format: <bool> (0 = real, 1 = synthetic (default))
389 atkbd.softrepeat= [HW]
390 Use software keyboard repeat
392 autotest [IA64]
394 baycom_epp= [HW,AX25]
395 Format: <io>,<mode>
397 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
398 Format: <io>,<mode>
399 See header of drivers/net/hamradio/baycom_par.c.
401 baycom_ser_fdx= [HW,AX25]
402 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
403 Format: <io>,<irq>,<mode>[,<baud>]
404 See header of drivers/net/hamradio/baycom_ser_fdx.c.
406 baycom_ser_hdx= [HW,AX25]
407 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
408 Format: <io>,<irq>,<mode>
409 See header of drivers/net/hamradio/baycom_ser_hdx.c.
411 boot_delay= Milliseconds to delay each printk during boot.
412 Values larger than 10 seconds (10000) are changed to
413 no delay (0).
414 Format: integer
416 bootmem_debug [KNL] Enable bootmem allocator debug messages.
418 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
419 bttv.radio= Most important insmod options are available as
420 kernel args too.
421 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
422 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
424 BusLogic= [HW,SCSI]
425 See drivers/scsi/BusLogic.c, comment before function
426 BusLogic_ParseDriverOptions().
428 c101= [NET] Moxa C101 synchronous serial card
430 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
431 Sometimes CPU hardware bugs make them report the cache
432 size incorrectly. The kernel will attempt work arounds
433 to fix known problems, but for some CPUs it is not
434 possible to determine what the correct size should be.
435 This option provides an override for these situations.
437 capability.disable=
438 [SECURITY] Disable capabilities. This would normally
439 be used only if an alternative security model is to be
440 configured. Potentially dangerous and should only be
441 used if you are entirely sure of the consequences.
443 ccw_timeout_log [S390]
444 See Documentation/s390/CommonIO for details.
446 cgroup_disable= [KNL] Disable a particular controller
447 Format: {name of the controller(s) to disable}
448 {Currently supported controllers - "memory"}
450 checkreqprot [SELINUX] Set initial checkreqprot flag value.
451 Format: { "0" | "1" }
452 See security/selinux/Kconfig help text.
453 0 -- check protection applied by kernel (includes
454 any implied execute protection).
455 1 -- check protection requested by application.
456 Default value is set via a kernel config option.
457 Value can be changed at runtime via
458 /selinux/checkreqprot.
460 cio_ignore= [S390]
461 See Documentation/s390/CommonIO for details.
463 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
464 [Deprecated]
465 Forces specified clocksource (if available) to be used
466 when calculating gettimeofday(). If specified
467 clocksource is not available, it defaults to PIT.
468 Format: { pit | tsc | cyclone | pmtmr }
470 clocksource= [GENERIC_TIME] Override the default clocksource
471 Format: <string>
472 Override the default clocksource and use the clocksource
473 with the name specified.
474 Some clocksource names to choose from, depending on
475 the platform:
476 [all] jiffies (this is the base, fallback clocksource)
477 [ACPI] acpi_pm
478 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
479 pxa_timer,timer3,32k_counter,timer0_1
480 [AVR32] avr32
481 [X86-32] pit,hpet,tsc,vmi-timer;
482 scx200_hrt on Geode; cyclone on IBM x440
483 [MIPS] MIPS
484 [PARISC] cr16
485 [S390] tod
486 [SH] SuperH
487 [SPARC64] tick
488 [X86-64] hpet,tsc
490 clearcpuid=BITNUM [X86]
491 Disable CPUID feature X for the kernel. See
492 arch/x86/include/asm/cpufeature.h for the valid bit
493 numbers. Note the Linux specific bits are not necessarily
494 stable over kernel options, but the vendor specific
495 ones should be.
496 Also note that user programs calling CPUID directly
497 or using the feature without checking anything
498 will still see it. This just prevents it from
499 being used by the kernel or shown in /proc/cpuinfo.
500 Also note the kernel might malfunction if you disable
501 some critical bits.
503 cmo_free_hint= [PPC] Format: { yes | no }
504 Specify whether pages are marked as being inactive
505 when they are freed. This is used in CMO environments
506 to determine OS memory pressure for page stealing by
507 a hypervisor.
508 Default: yes
510 code_bytes [X86] How many bytes of object code to print
511 in an oops report.
512 Range: 0 - 8192
513 Default: 64
515 com20020= [HW,NET] ARCnet - COM20020 chipset
516 Format:
517 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
519 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
520 Format: <io>[,<irq>]
522 com90xx= [HW,NET]
523 ARCnet - COM90xx chipset (memory-mapped buffers)
524 Format: <io>[,<irq>[,<memstart>]]
526 condev= [HW,S390] console device
527 conmode=
529 console= [KNL] Output console device and options.
531 tty<n> Use the virtual console device <n>.
533 ttyS<n>[,options]
534 ttyUSB0[,options]
535 Use the specified serial port. The options are of
536 the form "bbbbpnf", where "bbbb" is the baud rate,
537 "p" is parity ("n", "o", or "e"), "n" is number of
538 bits, and "f" is flow control ("r" for RTS or
539 omit it). Default is "9600n8".
541 See Documentation/serial-console.txt for more
542 information. See
543 Documentation/networking/netconsole.txt for an
544 alternative.
546 uart[8250],io,<addr>[,options]
547 uart[8250],mmio,<addr>[,options]
548 Start an early, polled-mode console on the 8250/16550
549 UART at the specified I/O port or MMIO address,
550 switching to the matching ttyS device later. The
551 options are the same as for ttyS, above.
553 If the device connected to the port is not a TTY but a braille
554 device, prepend "brl," before the device type, for instance
555 console=brl,ttyS0
556 For now, only VisioBraille is supported.
558 consoleblank= [KNL] The console blank (screen saver) timeout in
559 seconds. Defaults to 10*60 = 10mins. A value of 0
560 disables the blank timer.
562 coredump_filter=
563 [KNL] Change the default value for
564 /proc/<pid>/coredump_filter.
565 See also Documentation/filesystems/proc.txt.
567 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
568 Format:
569 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
571 crashkernel=nn[KMG]@ss[KMG]
572 [KNL] Reserve a chunk of physical memory to
573 hold a kernel to switch to with kexec on panic.
575 crashkernel=range1:size1[,range2:size2,...][@offset]
576 [KNL] Same as above, but depends on the memory
577 in the running system. The syntax of range is
578 start-[end] where start and end are both
579 a memory unit (amount[KMG]). See also
580 Documentation/kdump/kdump.txt for a example.
582 cs89x0_dma= [HW,NET]
583 Format: <dma>
585 cs89x0_media= [HW,NET]
586 Format: { rj45 | aui | bnc }
588 dasd= [HW,NET]
589 See header of drivers/s390/block/dasd_devmap.c.
591 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
592 (one device per port)
593 Format: <port#>,<type>
594 See also Documentation/input/joystick-parport.txt
596 debug [KNL] Enable kernel debugging (events log level).
598 debug_locks_verbose=
599 [KNL] verbose self-tests
600 Format=<0|1>
601 Print debugging info while doing the locking API
602 self-tests.
603 We default to 0 (no extra messages), setting it to
604 1 will print _a lot_ more information - normally
605 only useful to kernel developers.
607 debug_objects [KNL] Enable object debugging
609 no_debug_objects
610 [KNL] Disable object debugging
612 debugpat [X86] Enable PAT debugging
614 decnet.addr= [HW,NET]
615 Format: <area>[,<node>]
616 See also Documentation/networking/decnet.txt.
618 default_hugepagesz=
619 [same as hugepagesz=] The size of the default
620 HugeTLB page size. This is the size represented by
621 the legacy /proc/ hugepages APIs, used for SHM, and
622 default size when mounting hugetlbfs filesystems.
623 Defaults to the default architecture's huge page size
624 if not specified.
626 dhash_entries= [KNL]
627 Set number of hash buckets for dentry cache.
629 digi= [HW,SERIAL]
630 IO parameters + enable/disable command.
632 digiepca= [HW,SERIAL]
633 See drivers/char/README.epca and
634 Documentation/serial/digiepca.txt.
636 disable= [IPV6]
637 See Documentation/networking/ipv6.txt.
639 disable_ipv6= [IPV6]
640 See Documentation/networking/ipv6.txt.
642 disable_mtrr_cleanup [X86]
643 The kernel tries to adjust MTRR layout from continuous
644 to discrete, to make X server driver able to add WB
645 entry later. This parameter disables that.
647 disable_mtrr_trim [X86, Intel and AMD only]
648 By default the kernel will trim any uncacheable
649 memory out of your available memory pool based on
650 MTRR settings. This parameter disables that behavior,
651 possibly causing your machine to run very slowly.
653 disable_timer_pin_1 [X86]
654 Disable PIN 1 of APIC timer
655 Can be useful to work around chipset bugs.
657 dmasound= [HW,OSS] Sound subsystem buffers
659 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
660 this option disables the debugging code at boot.
662 dma_debug_entries=<number>
663 This option allows to tune the number of preallocated
664 entries for DMA-API debugging code. One entry is
665 required per DMA-API allocation. Use this if the
666 DMA-API debugging code disables itself because the
667 architectural default is too low.
669 dma_debug_driver=<driver_name>
670 With this option the DMA-API debugging driver
671 filter feature can be enabled at boot time. Just
672 pass the driver to filter for as the parameter.
673 The filter can be disabled or changed to another
674 driver later using sysfs.
676 dscc4.setup= [NET]
678 dtc3181e= [HW,SCSI]
680 dynamic_printk Enables pr_debug()/dev_dbg() calls if
681 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
682 These can also be switched on/off via
683 <debugfs>/dynamic_printk/modules
685 earlycon= [KNL] Output early console device and options.
686 uart[8250],io,<addr>[,options]
687 uart[8250],mmio,<addr>[,options]
688 Start an early, polled-mode console on the 8250/16550
689 UART at the specified I/O port or MMIO address.
690 The options are the same as for ttyS, above.
692 earlyprintk= [X86,SH,BLACKFIN]
693 earlyprintk=vga
694 earlyprintk=serial[,ttySn[,baudrate]]
695 earlyprintk=ttySn[,baudrate]
696 earlyprintk=dbgp[debugController#]
698 Append ",keep" to not disable it when the real console
699 takes over.
701 Only vga or serial or usb debug port at a time.
703 Currently only ttyS0 and ttyS1 are supported.
705 Interaction with the standard serial driver is not
706 very good.
708 The VGA output is eventually overwritten by the real
709 console.
711 eata= [HW,SCSI]
713 edd= [EDD]
714 Format: {"off" | "on" | "skip[mbr]"}
716 eisa_irq_edge= [PARISC,HW]
717 See header of drivers/parisc/eisa.c.
719 elanfreq= [X86-32]
720 See comment before function elanfreq_setup() in
721 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
723 elevator= [IOSCHED]
724 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
725 See Documentation/block/as-iosched.txt and
726 Documentation/block/deadline-iosched.txt for details.
728 elfcorehdr= [IA64,PPC,SH,X86]
729 Specifies physical address of start of kernel core
730 image elf header. Generally kexec loader will
731 pass this option to capture kernel.
732 See Documentation/kdump/kdump.txt for details.
734 enable_mtrr_cleanup [X86]
735 The kernel tries to adjust MTRR layout from continuous
736 to discrete, to make X server driver able to add WB
737 entry later. This parameter enables that.
739 enable_timer_pin_1 [X86]
740 Enable PIN 1 of APIC timer
741 Can be useful to work around chipset bugs
742 (in particular on some ATI chipsets).
743 The kernel tries to set a reasonable default.
745 enforcing [SELINUX] Set initial enforcing status.
746 Format: {"0" | "1"}
747 See security/selinux/Kconfig help text.
748 0 -- permissive (log only, no denials).
749 1 -- enforcing (deny and log).
750 Default value is 0.
751 Value can be changed at runtime via /selinux/enforce.
753 ether= [HW,NET] Ethernet cards parameters
754 This option is obsoleted by the "netdev=" option, which
755 has equivalent usage. See its documentation for details.
757 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
758 Format: <io>[,<irq>]
760 failslab=
761 fail_page_alloc=
762 fail_make_request=[KNL]
763 General fault injection mechanism.
764 Format: <interval>,<probability>,<space>,<times>
765 See also /Documentation/fault-injection/.
767 fd_mcs= [HW,SCSI]
768 See header of drivers/scsi/fd_mcs.c.
770 fdomain= [HW,SCSI]
771 See header of drivers/scsi/fdomain.c.
773 floppy= [HW]
774 See Documentation/blockdev/floppy.txt.
776 force_pal_cache_flush
777 [IA-64] Avoid check_sal_cache_flush which may hang on
778 buggy SAL_CACHE_FLUSH implementations. Using this
779 parameter will force ia64_sal_cache_flush to call
780 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
782 ftrace=[tracer]
783 [FTRACE] will set and start the specified tracer
784 as early as possible in order to facilitate early
785 boot debugging.
787 ftrace_dump_on_oops
788 [FTRACE] will dump the trace buffers on oops.
790 ftrace_filter=[function-list]
791 [FTRACE] Limit the functions traced by the function
792 tracer at boot up. function-list is a comma separated
793 list of functions. This list can be changed at run
794 time by the set_ftrace_filter file in the debugfs
795 tracing directory.
797 ftrace_notrace=[function-list]
798 [FTRACE] Do not trace the functions specified in
799 function-list. This list can be changed at run time
800 by the set_ftrace_notrace file in the debugfs
801 tracing directory.
803 ftrace_graph_filter=[function-list]
804 [FTRACE] Limit the top level callers functions traced
805 by the function graph tracer at boot up.
806 function-list is a comma separated list of functions
807 that can be changed at run time by the
808 set_graph_function file in the debugfs tracing directory.
810 gamecon.map[2|3]=
811 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
812 support via parallel port (up to 5 devices per port)
813 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
814 See also Documentation/input/joystick-parport.txt
816 gamma= [HW,DRM]
818 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
819 Format: off | on
820 default: on
822 gcov_persist= [GCOV] When non-zero (default), profiling data for
823 kernel modules is saved and remains accessible via
824 debugfs, even when the module is unloaded/reloaded.
825 When zero, profiling data is discarded and associated
826 debugfs files are removed at module unload time.
828 gdth= [HW,SCSI]
829 See header of drivers/scsi/gdth.c.
831 gpt [EFI] Forces disk with valid GPT signature but
832 invalid Protective MBR to be treated as GPT.
834 gvp11= [HW,SCSI]
836 hashdist= [KNL,NUMA] Large hashes allocated during boot
837 are distributed across NUMA nodes. Defaults on
838 for 64bit NUMA, off otherwise.
839 Format: 0 | 1 (for off | on)
841 hcl= [IA-64] SGI's Hardware Graph compatibility layer
843 hd= [EIDE] (E)IDE hard drive subsystem geometry
844 Format: <cyl>,<head>,<sect>
846 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
847 size of <nn>. This works even on boxes that have no
848 highmem otherwise. This also works to reduce highmem
849 size on bigger boxes.
851 highres= [KNL] Enable/disable high resolution timer mode.
852 Valid parameters: "on", "off"
853 Default: "on"
855 hisax= [HW,ISDN]
856 See Documentation/isdn/README.HiSax.
858 hlt [BUGS=ARM,SH]
860 hpet= [X86-32,HPET] option to control HPET usage
861 Format: { enable (default) | disable | force |
862 verbose }
863 disable: disable HPET and use PIT instead
864 force: allow force enabled of undocumented chips (ICH4,
865 VIA, nVidia)
866 verbose: show contents of HPET registers during setup
868 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
869 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
870 On x86-64 and powerpc, this option can be specified
871 multiple times interleaved with hugepages= to reserve
872 huge pages of different sizes. Valid pages sizes on
873 x86-64 are 2M (when the CPU supports "pse") and 1G
874 (when the CPU supports the "pdpe1gb" cpuinfo flag)
875 Note that 1GB pages can only be allocated at boot time
876 using hugepages= and not freed afterwards.
878 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
879 terminal devices. Valid values: 0..8
880 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
881 If specified, z/VM IUCV HVC accepts connections
882 from listed z/VM user IDs only.
884 i2c_bus= [HW] Override the default board specific I2C bus speed
885 or register an additional I2C bus that is not
886 registered from board initialization code.
887 Format:
888 <bus_id>,<clkrate>
890 i8042.debug [HW] Toggle i8042 debug mode
891 i8042.direct [HW] Put keyboard port into non-translated mode
892 i8042.dumbkbd [HW] Pretend that controller can only read data from
893 keyboard and cannot control its state
894 (Don't attempt to blink the leds)
895 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
896 i8042.nokbd [HW] Don't check/create keyboard port
897 i8042.noloop [HW] Disable the AUX Loopback command while probing
898 for the AUX port
899 i8042.nomux [HW] Don't check presence of an active multiplexing
900 controller
901 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
902 controllers
903 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
904 i8042.panicblink=
905 [HW] Frequency with which keyboard LEDs should blink
906 when kernel panics (default is 0.5 sec)
907 i8042.reset [HW] Reset the controller during init and cleanup
908 i8042.unlock [HW] Unlock (ignore) the keylock
910 i810= [HW,DRM]
912 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
913 indicates that the driver is running on unsupported
914 hardware.
915 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
916 does not match list of supported models.
917 i8k.power_status
918 [HW] Report power status in /proc/i8k
919 (disabled by default)
920 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
921 capability is set.
923 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
924 See Documentation/mca.txt.
926 icn= [HW,ISDN]
927 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
929 ide-core.nodma= [HW] (E)IDE subsystem
930 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
931 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
932 .cdrom .chs .ignore_cable are additional options
933 See Documentation/ide/ide.txt.
935 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
936 Claim all unknown PCI IDE storage controllers.
938 idle= [X86]
939 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
940 Poll forces a polling idle loop that can slightly
941 improve the performance of waking up a idle CPU, but
942 will use a lot of power and make the system run hot.
943 Not recommended.
944 idle=mwait: On systems which support MONITOR/MWAIT but
945 the kernel chose to not use it because it doesn't save
946 as much power as a normal idle loop, use the
947 MONITOR/MWAIT idle loop anyways. Performance should be
948 the same as idle=poll.
949 idle=halt: Halt is forced to be used for CPU idle.
950 In such case C2/C3 won't be used again.
951 idle=nomwait: Disable mwait for CPU C-states
953 ignore_loglevel [KNL]
954 Ignore loglevel setting - this will print /all/
955 kernel messages to the console. Useful for debugging.
957 ihash_entries= [KNL]
958 Set number of hash buckets for inode cache.
960 ima_audit= [IMA]
961 Format: { "0" | "1" }
962 0 -- integrity auditing messages. (Default)
963 1 -- enable informational integrity auditing messages.
965 ima_hash= [IMA]
966 Format: { "sha1" | "md5" }
967 default: "sha1"
969 ima_tcb [IMA]
970 Load a policy which meets the needs of the Trusted
971 Computing Base. This means IMA will measure all
972 programs exec'd, files mmap'd for exec, and all files
973 opened for read by uid=0.
975 in2000= [HW,SCSI]
976 See header of drivers/scsi/in2000.c.
978 init= [KNL]
979 Format: <full_path>
980 Run specified binary instead of /sbin/init as init
981 process.
983 initcall_debug [KNL] Trace initcalls as they are executed. Useful
984 for working out where the kernel is dying during
985 startup.
987 initrd= [BOOT] Specify the location of the initial ramdisk
989 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
990 Format: <irq>
992 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
993 on
994 Enable intel iommu driver.
995 off
996 Disable intel iommu driver.
997 igfx_off [Default Off]
998 By default, gfx is mapped as normal device. If a gfx
999 device has a dedicated DMAR unit, the DMAR unit is
1000 bypassed by not enabling DMAR with this option. In
1001 this case, gfx device will use physical address for
1002 DMA.
1003 forcedac [x86_64]
1004 With this option iommu will not optimize to look
1005 for io virtual address below 32 bit forcing dual
1006 address cycle on pci bus for cards supporting greater
1007 than 32 bit addressing. The default is to look
1008 for translation below 32 bit and if not available
1009 then look in the higher range.
1010 strict [Default Off]
1011 With this option on every unmap_single operation will
1012 result in a hardware IOTLB flush operation as opposed
1013 to batching them for performance.
1015 inttest= [IA64]
1017 iomem= Disable strict checking of access to MMIO memory
1018 strict regions from userspace.
1019 relaxed
1021 iommu= [x86]
1022 off
1023 force
1024 noforce
1025 biomerge
1026 panic
1027 nopanic
1028 merge
1029 nomerge
1030 forcesac
1031 soft
1032 pt [x86, IA64]
1034 io7= [HW] IO7 for Marvel based alpha systems
1035 See comment before marvel_specify_io7 in
1036 arch/alpha/kernel/core_marvel.c.
1038 io_delay= [X86] I/O delay method
1039 0x80
1040 Standard port 0x80 based delay
1041 0xed
1042 Alternate port 0xed based delay (needed on some systems)
1043 udelay
1044 Simple two microseconds delay
1045 none
1046 No delay
1048 ip= [IP_PNP]
1049 See Documentation/filesystems/nfs/nfsroot.txt.
1051 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1052 See comment before ip2_setup() in
1053 drivers/char/ip2/ip2base.c.
1055 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1056 See header of drivers/scsi/ips.c.
1058 irqfixup [HW]
1059 When an interrupt is not handled search all handlers
1060 for it. Intended to get systems with badly broken
1061 firmware running.
1063 irqpoll [HW]
1064 When an interrupt is not handled search all handlers
1065 for it. Also check all handlers each timer
1066 interrupt. Intended to get systems with badly broken
1067 firmware running.
1069 isapnp= [ISAPNP]
1070 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1072 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1073 Format:
1074 <cpu number>,...,<cpu number>
1075 or
1076 <cpu number>-<cpu number>
1077 (must be a positive range in ascending order)
1078 or a mixture
1079 <cpu number>,...,<cpu number>-<cpu number>
1081 This option can be used to specify one or more CPUs
1082 to isolate from the general SMP balancing and scheduling
1083 algorithms. You can move a process onto or off an
1084 "isolated" CPU via the CPU affinity syscalls or cpuset.
1085 <cpu number> begins at 0 and the maximum value is
1086 "number of CPUs in system - 1".
1088 This option is the preferred way to isolate CPUs. The
1089 alternative -- manually setting the CPU mask of all
1090 tasks in the system -- can cause problems and
1091 suboptimal load balancer performance.
1093 iucv= [HW,NET]
1095 js= [HW,JOY] Analog joystick
1096 See Documentation/input/joystick.txt.
1098 keepinitrd [HW,ARM]
1100 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1101 specifies the amount of memory usable by the kernel
1102 for non-movable allocations. The requested amount is
1103 spread evenly throughout all nodes in the system. The
1104 remaining memory in each node is used for Movable
1105 pages. In the event, a node is too small to have both
1106 kernelcore and Movable pages, kernelcore pages will
1107 take priority and other nodes will have a larger number
1108 of kernelcore pages. The Movable zone is used for the
1109 allocation of pages that may be reclaimed or moved
1110 by the page migration subsystem. This means that
1111 HugeTLB pages may not be allocated from this zone.
1112 Note that allocations like PTEs-from-HighMem still
1113 use the HighMem zone if it exists, and the Normal
1114 zone if it does not.
1116 kgdboc= [HW] kgdb over consoles.
1117 Requires a tty driver that supports console polling.
1118 (only serial supported for now)
1119 Format: <serial_device>[,baud]
1121 kmac= [MIPS] korina ethernet MAC address.
1122 Configure the RouterBoard 532 series on-chip
1123 Ethernet adapter MAC address.
1125 kmemleak= [KNL] Boot-time kmemleak enable/disable
1126 Valid arguments: on, off
1127 Default: on
1129 kstack=N [X86] Print N words from the kernel stack
1130 in oops dumps.
1132 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1133 Default is 0 (don't ignore, but inject #GP)
1135 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1136 Default is 1 (enabled)
1138 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1139 Default is 0 (off)
1141 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1142 for all guests.
1143 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1145 kvm-intel.bypass_guest_pf=
1146 [KVM,Intel] Disables bypassing of guest page faults
1147 on Intel chips. Default is 1 (enabled)
1149 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1150 (virtualized MMU) support on capable Intel chips.
1151 Default is 1 (enabled)
1153 kvm-intel.emulate_invalid_guest_state=
1154 [KVM,Intel] Enable emulation of invalid guest states
1155 Default is 0 (disabled)
1157 kvm-intel.flexpriority=
1158 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1159 Default is 1 (enabled)
1161 kvm-intel.unrestricted_guest=
1162 [KVM,Intel] Disable unrestricted guest feature
1163 (virtualized real and unpaged mode) on capable
1164 Intel chips. Default is 1 (enabled)
1166 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1167 feature (tagged TLBs) on capable Intel chips.
1168 Default is 1 (enabled)
1170 l2cr= [PPC]
1172 l3cr= [PPC]
1174 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1175 disabled it.
1177 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1178 in C2 power state.
1180 libata.dma= [LIBATA] DMA control
1181 libata.dma=0 Disable all PATA and SATA DMA
1182 libata.dma=1 PATA and SATA Disk DMA only
1183 libata.dma=2 ATAPI (CDROM) DMA only
1184 libata.dma=4 Compact Flash DMA only
1185 Combinations also work, so libata.dma=3 enables DMA
1186 for disks and CDROMs, but not CFs.
1188 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1189 libata.ignore_hpa=0 keep BIOS limits (default)
1190 libata.ignore_hpa=1 ignore limits, using full disk
1192 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1193 when set.
1194 Format: <int>
1196 libata.force= [LIBATA] Force configurations. The format is comma
1197 separated list of "[ID:]VAL" where ID is
1198 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1199 matching port, link or device. Basically, it matches
1200 the ATA ID string printed on console by libata. If
1201 the whole ID part is omitted, the last PORT and DEVICE
1202 values are used. If ID hasn't been specified yet, the
1203 configuration applies to all ports, links and devices.
1205 If only DEVICE is omitted, the parameter applies to
1206 the port and all links and devices behind it. DEVICE
1207 number of 0 either selects the first device or the
1208 first fan-out link behind PMP device. It does not
1209 select the host link. DEVICE number of 15 selects the
1210 host link and device attached to it.
1212 The VAL specifies the configuration to force. As long
1213 as there's no ambiguity shortcut notation is allowed.
1214 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1215 The following configurations can be forced.
1217 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1218 Any ID with matching PORT is used.
1220 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1222 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1223 udma[/][16,25,33,44,66,100,133] notation is also
1224 allowed.
1226 * [no]ncq: Turn on or off NCQ.
1228 * nohrst, nosrst, norst: suppress hard, soft
1229 and both resets.
1231 If there are multiple matching configurations changing
1232 the same attribute, the last one is used.
1234 lmb=debug [KNL] Enable lmb debug messages.
1236 load_ramdisk= [RAM] List of ramdisks to load from floppy
1237 See Documentation/blockdev/ramdisk.txt.
1239 lockd.nlm_grace_period=P [NFS] Assign grace period.
1240 Format: <integer>
1242 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1243 Format: <integer>
1245 lockd.nlm_timeout=T [NFS] Assign timeout value.
1246 Format: <integer>
1248 lockd.nlm_udpport=M [NFS] Assign UDP port.
1249 Format: <integer>
1251 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1252 Format: <irq>
1254 loglevel= All Kernel Messages with a loglevel smaller than the
1255 console loglevel will be printed to the console. It can
1256 also be changed with klogd or other programs. The
1257 loglevels are defined as follows:
1259 0 (KERN_EMERG) system is unusable
1260 1 (KERN_ALERT) action must be taken immediately
1261 2 (KERN_CRIT) critical conditions
1262 3 (KERN_ERR) error conditions
1263 4 (KERN_WARNING) warning conditions
1264 5 (KERN_NOTICE) normal but significant condition
1265 6 (KERN_INFO) informational
1266 7 (KERN_DEBUG) debug-level messages
1268 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1269 Format: { n | nk | nM }
1270 n must be a power of two. The default size
1271 is set in the kernel config file.
1273 logo.nologo [FB] Disables display of the built-in Linux logo.
1274 This may be used to provide more screen space for
1275 kernel log messages and is useful when debugging
1276 kernel boot problems.
1278 lp=0 [LP] Specify parallel ports to use, e.g,
1279 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1280 lp=reset first parallel port). 'lp=0' disables the
1281 lp=auto printer driver. 'lp=reset' (which can be
1282 specified in addition to the ports) causes
1283 attached printers to be reset. Using
1284 lp=port1,port2,... specifies the parallel ports
1285 to associate lp devices with, starting with
1286 lp0. A port specification may be 'none' to skip
1287 that lp device, or a parport name such as
1288 'parport0'. Specifying 'lp=auto' instead of a
1289 port specification list means that device IDs
1290 from each port should be examined, to see if
1291 an IEEE 1284-compliant printer is attached; if
1292 so, the driver will manage that printer.
1293 See also header of drivers/char/lp.c.
1295 lpj=n [KNL]
1296 Sets loops_per_jiffy to given constant, thus avoiding
1297 time-consuming boot-time autodetection (up to 250 ms per
1298 CPU). 0 enables autodetection (default). To determine
1299 the correct value for your kernel, boot with normal
1300 autodetection and see what value is printed. Note that
1301 on SMP systems the preset will be applied to all CPUs,
1302 which is likely to cause problems if your CPUs need
1303 significantly divergent settings. An incorrect value
1304 will cause delays in the kernel to be wrong, leading to
1305 unpredictable I/O errors and other breakage. Although
1306 unlikely, in the extreme case this might damage your
1307 hardware.
1309 ltpc= [NET]
1310 Format: <io>,<irq>,<dma>
1312 mac5380= [HW,SCSI] Format:
1313 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1315 machvec= [IA64] Force the use of a particular machine-vector
1316 (machvec) in a generic kernel.
1317 Example: machvec=hpzx1_swiotlb
1319 machtype= [Loongson] Share the same kernel image file between different
1320 yeeloong laptop.
1321 Example: machtype=lemote-yeeloong-2f-7inch
1323 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1324 than or equal to this physical address is ignored.
1326 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1327 should make use of. maxcpus=n : n >= 0 limits the
1328 kernel to using 'n' processors. n=0 is a special case,
1329 it is equivalent to "nosmp", which also disables
1330 the IO APIC.
1332 max_loop= [LOOP] Maximum number of loopback devices that can
1333 be mounted
1334 Format: <1-256>
1336 max_luns= [SCSI] Maximum number of LUNs to probe.
1337 Should be between 1 and 2^32-1.
1339 max_report_luns=
1340 [SCSI] Maximum number of LUNs received.
1341 Should be between 1 and 16384.
1343 mcatest= [IA-64]
1345 mce [X86-32] Machine Check Exception
1347 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1349 md= [HW] RAID subsystems devices and level
1350 See Documentation/md.txt.
1352 mdacon= [MDA]
1353 Format: <first>,<last>
1354 Specifies range of consoles to be captured by the MDA.
1356 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1357 Amount of memory to be used when the kernel is not able
1358 to see the whole system memory or for test.
1359 [X86-32] Use together with memmap= to avoid physical
1360 address space collisions. Without memmap= PCI devices
1361 could be placed at addresses belonging to unused RAM.
1363 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1364 memory.
1366 memchunk=nn[KMG]
1367 [KNL,SH] Allow user to override the default size for
1368 per-device physically contiguous DMA buffers.
1370 memmap=exactmap [KNL,X86] Enable setting of an exact
1371 E820 memory map, as specified by the user.
1372 Such memmap=exactmap lines can be constructed based on
1373 BIOS output or other requirements. See the memmap=nn@ss
1374 option description.
1376 memmap=nn[KMG]@ss[KMG]
1377 [KNL] Force usage of a specific region of memory
1378 Region of memory to be used, from ss to ss+nn.
1380 memmap=nn[KMG]#ss[KMG]
1381 [KNL,ACPI] Mark specific memory as ACPI data.
1382 Region of memory to be used, from ss to ss+nn.
1384 memmap=nn[KMG]$ss[KMG]
1385 [KNL,ACPI] Mark specific memory as reserved.
1386 Region of memory to be used, from ss to ss+nn.
1387 Example: Exclude memory from 0x18690000-0x1869ffff
1388 memmap=64K$0x18690000
1389 or
1390 memmap=0x10000$0x18690000
1392 memory_corruption_check=0/1 [X86]
1393 Some BIOSes seem to corrupt the first 64k of
1394 memory when doing things like suspend/resume.
1395 Setting this option will scan the memory
1396 looking for corruption. Enabling this will
1397 both detect corruption and prevent the kernel
1398 from using the memory being corrupted.
1399 However, its intended as a diagnostic tool; if
1400 repeatable BIOS-originated corruption always
1401 affects the same memory, you can use memmap=
1402 to prevent the kernel from using that memory.
1404 memory_corruption_check_size=size [X86]
1405 By default it checks for corruption in the low
1406 64k, making this memory unavailable for normal
1407 use. Use this parameter to scan for
1408 corruption in more or less memory.
1410 memory_corruption_check_period=seconds [X86]
1411 By default it checks for corruption every 60
1412 seconds. Use this parameter to check at some
1413 other rate. 0 disables periodic checking.
1415 memtest= [KNL,X86] Enable memtest
1416 Format: <integer>
1417 default : 0 <disable>
1418 Specifies the number of memtest passes to be
1419 performed. Each pass selects another test
1420 pattern from a given set of patterns. Memtest
1421 fills the memory with this pattern, validates
1422 memory contents and reserves bad memory
1423 regions that are detected.
1425 meye.*= [HW] Set MotionEye Camera parameters
1426 See Documentation/video4linux/meye.txt.
1428 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1429 Multi-Function General Purpose Timers on AMD Geode
1430 platforms.
1432 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1433 the BIOS has incorrectly applied a workaround. TinyBIOS
1434 version 0.98 is known to be affected, 0.99 fixes the
1435 problem by letting the user disable the workaround.
1437 mga= [HW,DRM]
1439 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1440 physical address is ignored.
1442 mini2440= [ARM,HW,KNL]
1443 Format:[0..2][b][c][t]
1444 Default: "0tb"
1445 MINI2440 configuration specification:
1446 0 - The attached screen is the 3.5" TFT
1447 1 - The attached screen is the 7" TFT
1448 2 - The VGA Shield is attached (1024x768)
1449 Leaving out the screen size parameter will not load
1450 the TFT driver, and the framebuffer will be left
1451 unconfigured.
1452 b - Enable backlight. The TFT backlight pin will be
1453 linked to the kernel VESA blanking code and a GPIO
1454 LED. This parameter is not necessary when using the
1455 VGA shield.
1456 c - Enable the s3c camera interface.
1457 t - Reserved for enabling touchscreen support. The
1458 touchscreen support is not enabled in the mainstream
1459 kernel as of 2.6.30, a preliminary port can be found
1460 in the "bleeding edge" mini2440 support kernel at
1461 http://repo.or.cz/w/linux-2.6/mini2440.git
1463 mminit_loglevel=
1464 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1465 parameter allows control of the logging verbosity for
1466 the additional memory initialisation checks. A value
1467 of 0 disables mminit logging and a level of 4 will
1468 log everything. Information is printed at KERN_DEBUG
1469 so loglevel=8 may also need to be specified.
1471 mousedev.tap_time=
1472 [MOUSE] Maximum time between finger touching and
1473 leaving touchpad surface for touch to be considered
1474 a tap and be reported as a left button click (for
1475 touchpads working in absolute mode only).
1476 Format: <msecs>
1477 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1478 reporting absolute coordinates, such as tablets
1479 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1480 reporting absolute coordinates, such as tablets
1482 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1483 is similar to kernelcore except it specifies the
1484 amount of memory used for migratable allocations.
1485 If both kernelcore and movablecore is specified,
1486 then kernelcore will be at *least* the specified
1487 value but may be more. If movablecore on its own
1488 is specified, the administrator must be careful
1489 that the amount of memory usable for all allocations
1490 is not too small.
1492 mpu401= [HW,OSS]
1493 Format: <io>,<irq>
1495 MTD_Partition= [MTD]
1496 Format: <name>,<region-number>,<size>,<offset>
1498 MTD_Region= [MTD] Format:
1499 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1501 mtdparts= [MTD]
1502 See drivers/mtd/cmdlinepart.c.
1504 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1506 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1508 boundary - index of last SLC block on Flex-OneNAND.
1509 The remaining blocks are configured as MLC blocks.
1510 lock - Configure if Flex-OneNAND boundary should be locked.
1511 Once locked, the boundary cannot be changed.
1512 1 indicates lock status, 0 indicates unlock status.
1514 mtdset= [ARM]
1515 ARM/S3C2412 JIVE boot control
1517 See arch/arm/mach-s3c2412/mach-jive.c
1519 mtouchusb.raw_coordinates=
1520 [HW] Make the MicroTouch USB driver use raw coordinates
1521 ('y', default) or cooked coordinates ('n')
1523 mtrr_chunk_size=nn[KMG] [X86]
1524 used for mtrr cleanup. It is largest continuous chunk
1525 that could hold holes aka. UC entries.
1527 mtrr_gran_size=nn[KMG] [X86]
1528 Used for mtrr cleanup. It is granularity of mtrr block.
1529 Default is 1.
1530 Large value could prevent small alignment from
1531 using up MTRRs.
1533 mtrr_spare_reg_nr=n [X86]
1534 Format: <integer>
1535 Range: 0,7 : spare reg number
1536 Default : 1
1537 Used for mtrr cleanup. It is spare mtrr entries number.
1538 Set to 2 or more if your graphical card needs more.
1540 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1542 NCR_D700= [HW,SCSI]
1543 See header of drivers/scsi/NCR_D700.c.
1545 ncr5380= [HW,SCSI]
1547 ncr53c400= [HW,SCSI]
1549 ncr53c400a= [HW,SCSI]
1551 ncr53c406a= [HW,SCSI]
1553 ncr53c8xx= [HW,SCSI]
1555 netdev= [NET] Network devices parameters
1556 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1557 Note that mem_start is often overloaded to mean
1558 something different and driver-specific.
1559 This usage is only documented in each driver source
1560 file if at all.
1562 nf_conntrack.acct=
1563 [NETFILTER] Enable connection tracking flow accounting
1564 0 to disable accounting
1565 1 to enable accounting
1566 Default value depends on CONFIG_NF_CT_ACCT that is
1567 going to be removed in 2.6.29.
1569 nfsaddrs= [NFS]
1570 See Documentation/filesystems/nfs/nfsroot.txt.
1572 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1573 See Documentation/filesystems/nfs/nfsroot.txt.
1575 nfs.callback_tcpport=
1576 [NFS] set the TCP port on which the NFSv4 callback
1577 channel should listen.
1579 nfs.cache_getent=
1580 [NFS] sets the pathname to the program which is used
1581 to update the NFS client cache entries.
1583 nfs.cache_getent_timeout=
1584 [NFS] sets the timeout after which an attempt to
1585 update a cache entry is deemed to have failed.
1587 nfs.idmap_cache_timeout=
1588 [NFS] set the maximum lifetime for idmapper cache
1589 entries.
1591 nfs.enable_ino64=
1592 [NFS] enable 64-bit inode numbers.
1593 If zero, the NFS client will fake up a 32-bit inode
1594 number for the readdir() and stat() syscalls instead
1595 of returning the full 64-bit number.
1596 The default is to return 64-bit inode numbers.
1598 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1599 when a NMI is triggered.
1600 Format: [state][,regs][,debounce][,die]
1602 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1603 Format: [panic,][num]
1604 Valid num: 0,1,2
1605 0 - turn nmi_watchdog off
1606 1 - use the IO-APIC timer for the NMI watchdog
1607 2 - use the local APIC for the NMI watchdog using
1608 a performance counter. Note: This will use one
1609 performance counter and the local APIC's performance
1610 vector.
1611 When panic is specified, panic when an NMI watchdog
1612 timeout occurs.
1613 This is useful when you use a panic=... timeout and
1614 need the box quickly up again.
1615 Instead of 1 and 2 it is possible to use the following
1616 symbolic names: lapic and ioapic
1617 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1619 netpoll.carrier_timeout=
1620 [NET] Specifies amount of time (in seconds) that
1621 netpoll should wait for a carrier. By default netpoll
1622 waits 4 seconds.
1624 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1625 emulation library even if a 387 maths coprocessor
1626 is present.
1628 no_console_suspend
1629 [HW] Never suspend the console
1630 Disable suspending of consoles during suspend and
1631 hibernate operations. Once disabled, debugging
1632 messages can reach various consoles while the rest
1633 of the system is being put to sleep (ie, while
1634 debugging driver suspend/resume hooks). This may
1635 not work reliably with all consoles, but is known
1636 to work with serial and VGA consoles.
1638 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1639 caches in the slab allocator. Saves per-node memory,
1640 but will impact performance.
1642 noalign [KNL,ARM]
1644 noapic [SMP,APIC] Tells the kernel to not make use of any
1645 IOAPICs that may be present in the system.
1647 nobats [PPC] Do not use BATs for mapping kernel lowmem
1648 on "Classic" PPC cores.
1650 nocache [ARM]
1652 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1654 nodelayacct [KNL] Disable per-task delay accounting
1656 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1658 nodsp [SH] Disable hardware DSP at boot time.
1660 noefi [X86] Disable EFI runtime services support.
1662 noexec [IA-64]
1664 noexec [X86]
1665 On X86-32 available only on PAE configured kernels.
1666 noexec=on: enable non-executable mappings (default)
1667 noexec=off: disable non-executable mappings
1669 noexec32 [X86-64]
1670 This affects only 32-bit executables.
1671 noexec32=on: enable non-executable mappings (default)
1672 read doesn't imply executable mappings
1673 noexec32=off: disable non-executable mappings
1674 read implies executable mappings
1676 nofpu [SH] Disable hardware FPU at boot time.
1678 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1679 register save and restore. The kernel will only save
1680 legacy floating-point registers on task switch.
1682 noxsave [BUGS=X86] Disables x86 extended register state save
1683 and restore using xsave. The kernel will fallback to
1684 enabling legacy floating-point and sse state.
1686 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1687 wfi(ARM) instruction doesn't work correctly and not to
1688 use it. This is also useful when using JTAG debugger.
1690 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1691 instruction doesn't work correctly and not to
1692 use it.
1694 no_file_caps Tells the kernel not to honor file capabilities. The
1695 only way then for a file to be executed with privilege
1696 is to be setuid root or executed by root.
1698 nohalt [IA-64] Tells the kernel not to use the power saving
1699 function PAL_HALT_LIGHT when idle. This increases
1700 power-consumption. On the positive side, it reduces
1701 interrupt wake-up latency, which may improve performance
1702 in certain environments such as networked servers or
1703 real-time systems.
1705 nohz= [KNL] Boottime enable/disable dynamic ticks
1706 Valid arguments: on, off
1707 Default: on
1709 noiotrap [SH] Disables trapped I/O port accesses.
1711 noirqdebug [X86-32] Disables the code which attempts to detect and
1712 disable unhandled interrupt sources.
1714 no_timer_check [X86,APIC] Disables the code which tests for
1715 broken timer IRQ sources.
1717 noisapnp [ISAPNP] Disables ISA PnP code.
1719 noinitrd [RAM] Tells the kernel not to load any configured
1720 initial RAM disk.
1722 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1723 remapping.
1725 nointroute [IA-64]
1727 nojitter [IA64] Disables jitter checking for ITC timers.
1729 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1731 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1733 noltlbs [PPC] Do not use large page/tlb entries for kernel
1734 lowmem mapping on PPC40x.
1736 nomca [IA-64] Disable machine check abort handling
1738 nomce [X86-32] Machine Check Exception
1740 nomfgpt [X86-32] Disable Multi-Function General Purpose
1741 Timer usage (for AMD Geode machines).
1743 nopat [X86] Disable PAT (page attribute table extension of
1744 pagetables) support.
1746 norandmaps Don't use address space randomization. Equivalent to
1747 echo 0 > /proc/sys/kernel/randomize_va_space
1749 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1751 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1752 with UP alternatives
1754 noresidual [PPC] Don't use residual data on PReP machines.
1756 noresume [SWSUSP] Disables resume and restores original swap
1757 space.
1759 no-scroll [VGA] Disables scrollback.
1760 This is required for the Braillex ib80-piezo Braille
1761 reader made by F.H. Papenmeier (Germany).
1763 nosbagart [IA-64]
1765 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1767 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1768 and disable the IO APIC. legacy for "maxcpus=0".
1770 nosoftlockup [KNL] Disable the soft-lockup detector.
1772 noswapaccount [KNL] Disable accounting of swap in memory resource
1773 controller. (See Documentation/cgroups/memory.txt)
1775 nosync [HW,M68K] Disables sync negotiation for all devices.
1777 notsc [BUGS=X86-32] Disable Time Stamp Counter
1779 nousb [USB] Disable the USB subsystem
1781 nowb [ARM]
1783 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1785 nptcg= [IA64] Override max number of concurrent global TLB
1786 purges which is reported from either PAL_VM_SUMMARY or
1787 SAL PALO.
1789 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1790 could support. nr_cpus=n : n >= 1 limits the kernel to
1791 supporting 'n' processors. Later in runtime you can not
1792 use hotplug cpu feature to put more cpu back to online.
1793 just like you compile the kernel NR_CPUS=n
1795 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1797 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1798 one of ['zone', 'node', 'default'] can be specified
1799 This can be set from sysctl after boot.
1800 See Documentation/sysctl/vm.txt for details.
1802 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1803 See Documentation/debugging-via-ohci1394.txt for more
1804 info.
1806 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1807 Rather than timing out after 20 ms if an EC
1808 command is not properly ACKed, override the length
1809 of the timeout. We have interrupts disabled while
1810 waiting for the ACK, so if this is set too high
1811 interrupts *may* be lost!
1813 omap_mux= [OMAP] Override bootloader pin multiplexing.
1814 Format: <mux_mode0.mode_name=value>...
1815 For example, to override I2C bus2:
1816 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1818 opl3= [HW,OSS]
1819 Format: <io>
1821 oprofile.timer= [HW]
1822 Use timer interrupt instead of performance counters
1824 oprofile.cpu_type= Force an oprofile cpu type
1825 This might be useful if you have an older oprofile
1826 userland or if you want common events.
1827 Format: { arch_perfmon }
1828 arch_perfmon: [X86] Force use of architectural
1829 perfmon on Intel CPUs instead of the
1830 CPU specific event set.
1832 osst= [HW,SCSI] SCSI Tape Driver
1833 Format: <buffer_size>,<write_threshold>
1834 See also Documentation/scsi/st.txt.
1836 panic= [KNL] Kernel behaviour on panic
1837 Format: <timeout>
1839 parkbd.port= [HW] Parallel port number the keyboard adapter is
1840 connected to, default is 0.
1841 Format: <parport#>
1842 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1843 0 for XT, 1 for AT (default is AT).
1844 Format: <mode>
1846 parport= [HW,PPT] Specify parallel ports. 0 disables.
1847 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1848 Use 'auto' to force the driver to use any
1849 IRQ/DMA settings detected (the default is to
1850 ignore detected IRQ/DMA settings because of
1851 possible conflicts). You can specify the base
1852 address, IRQ, and DMA settings; IRQ and DMA
1853 should be numbers, or 'auto' (for using detected
1854 settings on that particular port), or 'nofifo'
1855 (to avoid using a FIFO even if it is detected).
1856 Parallel ports are assigned in the order they
1857 are specified on the command line, starting
1858 with parport0.
1860 parport_init_mode= [HW,PPT]
1861 Configure VIA parallel port to operate in
1862 a specific mode. This is necessary on Pegasos
1863 computer where firmware has no options for setting
1864 up parallel port mode and sets it to spp.
1865 Currently this function knows 686a and 8231 chips.
1866 Format: [spp|ps2|epp|ecp|ecpepp]
1868 pas2= [HW,OSS] Format:
1869 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1871 pas16= [HW,SCSI]
1872 See header of drivers/scsi/pas16.c.
1874 pause_on_oops=
1875 Halt all CPUs after the first oops has been printed for
1876 the specified number of seconds. This is to be used if
1877 your oopses keep scrolling off the screen.
1879 pcbit= [HW,ISDN]
1881 pcd. [PARIDE]
1882 See header of drivers/block/paride/pcd.c.
1883 See also Documentation/blockdev/paride.txt.
1885 pci=option[,option...] [PCI] various PCI subsystem options:
1886 earlydump [X86] dump PCI config space before the kernel
1887 changes anything
1888 off [X86] don't probe for the PCI bus
1889 bios [X86-32] force use of PCI BIOS, don't access
1890 the hardware directly. Use this if your machine
1891 has a non-standard PCI host bridge.
1892 nobios [X86-32] disallow use of PCI BIOS, only direct
1893 hardware access methods are allowed. Use this
1894 if you experience crashes upon bootup and you
1895 suspect they are caused by the BIOS.
1896 conf1 [X86] Force use of PCI Configuration
1897 Mechanism 1.
1898 conf2 [X86] Force use of PCI Configuration
1899 Mechanism 2.
1900 noaer [PCIE] If the PCIEAER kernel config parameter is
1901 enabled, this kernel boot option can be used to
1902 disable the use of PCIE advanced error reporting.
1903 nodomains [PCI] Disable support for multiple PCI
1904 root domains (aka PCI segments, in ACPI-speak).
1905 nommconf [X86] Disable use of MMCONFIG for PCI
1906 Configuration
1907 check_enable_amd_mmconf [X86] check for and enable
1908 properly configured MMIO access to PCI
1909 config space on AMD family 10h CPU
1910 nomsi [MSI] If the PCI_MSI kernel config parameter is
1911 enabled, this kernel boot option can be used to
1912 disable the use of MSI interrupts system-wide.
1913 noioapicquirk [APIC] Disable all boot interrupt quirks.
1914 Safety option to keep boot IRQs enabled. This
1915 should never be necessary.
1916 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1917 primary IO-APIC for bridges that cannot disable
1918 boot IRQs. This fixes a source of spurious IRQs
1919 when the system masks IRQs.
1920 noioapicreroute [APIC] Disable workaround that uses the
1921 boot IRQ equivalent of an IRQ that connects to
1922 a chipset where boot IRQs cannot be disabled.
1923 The opposite of ioapicreroute.
1924 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1925 routing table. These calls are known to be buggy
1926 on several machines and they hang the machine
1927 when used, but on other computers it's the only
1928 way to get the interrupt routing table. Try
1929 this option if the kernel is unable to allocate
1930 IRQs or discover secondary PCI buses on your
1931 motherboard.
1932 rom [X86] Assign address space to expansion ROMs.
1933 Use with caution as certain devices share
1934 address decoders between ROMs and other
1935 resources.
1936 norom [X86] Do not assign address space to
1937 expansion ROMs that do not already have
1938 BIOS assigned address ranges.
1939 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1940 assigned automatically to PCI devices. You can
1941 make the kernel exclude IRQs of your ISA cards
1942 this way.
1943 pirqaddr=0xAAAAA [X86] Specify the physical address
1944 of the PIRQ table (normally generated
1945 by the BIOS) if it is outside the
1946 F0000h-100000h range.
1947 lastbus=N [X86] Scan all buses thru bus #N. Can be
1948 useful if the kernel is unable to find your
1949 secondary buses and you want to tell it
1950 explicitly which ones they are.
1951 assign-busses [X86] Always assign all PCI bus
1952 numbers ourselves, overriding
1953 whatever the firmware may have done.
1954 usepirqmask [X86] Honor the possible IRQ mask stored
1955 in the BIOS $PIR table. This is needed on
1956 some systems with broken BIOSes, notably
1957 some HP Pavilion N5400 and Omnibook XE3
1958 notebooks. This will have no effect if ACPI
1959 IRQ routing is enabled.
1960 noacpi [X86] Do not use ACPI for IRQ routing
1961 or for PCI scanning.
1962 use_crs [X86] Use PCI host bridge window information
1963 from ACPI. On BIOSes from 2008 or later, this
1964 is enabled by default. If you need to use this,
1965 please report a bug.
1966 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1967 If you need to use this, please report a bug.
1968 routeirq Do IRQ routing for all PCI devices.
1969 This is normally done in pci_enable_device(),
1970 so this option is a temporary workaround
1971 for broken drivers that don't call it.
1972 skip_isa_align [X86] do not align io start addr, so can
1973 handle more pci cards
1974 firmware [ARM] Do not re-enumerate the bus but instead
1975 just use the configuration from the
1976 bootloader. This is currently used on
1977 IXP2000 systems where the bus has to be
1978 configured a certain way for adjunct CPUs.
1979 noearly [X86] Don't do any early type 1 scanning.
1980 This might help on some broken boards which
1981 machine check when some devices' config space
1982 is read. But various workarounds are disabled
1983 and some IOMMU drivers will not work.
1984 bfsort Sort PCI devices into breadth-first order.
1985 This sorting is done to get a device
1986 order compatible with older (<= 2.4) kernels.
1987 nobfsort Don't sort PCI devices into breadth-first order.
1988 cbiosize=nn[KMG] The fixed amount of bus space which is
1989 reserved for the CardBus bridge's IO window.
1990 The default value is 256 bytes.
1991 cbmemsize=nn[KMG] The fixed amount of bus space which is
1992 reserved for the CardBus bridge's memory
1993 window. The default value is 64 megabytes.
1994 resource_alignment=
1995 Format:
1996 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1997 Specifies alignment and device to reassign
1998 aligned memory resources.
1999 If <order of align> is not specified,
2000 PAGE_SIZE is used as alignment.
2001 PCI-PCI bridge can be specified, if resource
2002 windows need to be expanded.
2003 ecrc= Enable/disable PCIe ECRC (transaction layer
2004 end-to-end CRC checking).
2005 bios: Use BIOS/firmware settings. This is the
2006 the default.
2007 off: Turn ECRC off
2008 on: Turn ECRC on.
2010 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2011 Management.
2012 off Disable ASPM.
2013 force Enable ASPM even on devices that claim not to support it.
2014 WARNING: Forcing ASPM on may cause system lockups.
2016 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2017 Format: {auto|force}[,nomsi]
2018 auto Use native PCIe PME signaling if the BIOS allows the
2019 kernel to control PCIe config registers of root ports.
2020 force Use native PCIe PME signaling even if the BIOS refuses
2021 to allow the kernel to control the relevant PCIe config
2022 registers.
2023 nomsi Do not use MSI for native PCIe PME signaling (this makes
2024 all PCIe root ports use INTx for everything).
2026 pcmv= [HW,PCMCIA] BadgePAD 4
2028 pd. [PARIDE]
2029 See Documentation/blockdev/paride.txt.
2031 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2032 boot time.
2033 Format: { 0 | 1 }
2034 See arch/parisc/kernel/pdc_chassis.c
2036 percpu_alloc= Select which percpu first chunk allocator to use.
2037 Currently supported values are "embed" and "page".
2038 Archs may support subset or none of the selections.
2039 See comments in mm/percpu.c for details on each
2040 allocator. This parameter is primarily for debugging
2041 and performance comparison.
2043 pf. [PARIDE]
2044 See Documentation/blockdev/paride.txt.
2046 pg. [PARIDE]
2047 See Documentation/blockdev/paride.txt.
2049 pirq= [SMP,APIC] Manual mp-table setup
2050 See Documentation/x86/i386/IO-APIC.txt.
2052 plip= [PPT,NET] Parallel port network link
2053 Format: { parport<nr> | timid | 0 }
2054 See also Documentation/parport.txt.
2056 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2057 Override pmtimer IOPort with a hex value.
2058 e.g. pmtmr=0x508
2060 pnp.debug [PNP]
2061 Enable PNP debug messages. This depends on the
2062 CONFIG_PNP_DEBUG_MESSAGES option.
2064 pnpacpi= [ACPI]
2065 { off }
2067 pnpbios= [ISAPNP]
2068 { on | off | curr | res | no-curr | no-res }
2070 pnp_reserve_irq=
2071 [ISAPNP] Exclude IRQs for the autoconfiguration
2073 pnp_reserve_dma=
2074 [ISAPNP] Exclude DMAs for the autoconfiguration
2076 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2077 Ranges are in pairs (I/O port base and size).
2079 pnp_reserve_mem=
2080 [ISAPNP] Exclude memory regions for the
2081 autoconfiguration.
2082 Ranges are in pairs (memory base and size).
2084 ports= [IP_VS_FTP] IPVS ftp helper module
2085 Default is 21.
2086 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2087 may be specified.
2088 Format: <port>,<port>....
2090 print-fatal-signals=
2091 [KNL] debug: print fatal signals
2093 If enabled, warn about various signal handling
2094 related application anomalies: too many signals,
2095 too many POSIX.1 timers, fatal signals causing a
2096 coredump - etc.
2098 If you hit the warning due to signal overflow,
2099 you might want to try "ulimit -i unlimited".
2101 default: off.
2103 printk.time= Show timing data prefixed to each printk message line
2104 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2106 processor.max_cstate= [HW,ACPI]
2107 Limit processor to maximum C-state
2108 max_cstate=9 overrides any DMI blacklist limit.
2110 processor.nocst [HW,ACPI]
2111 Ignore the _CST method to determine C-states,
2112 instead using the legacy FADT method
2114 profile= [KNL] Enable kernel profiling via /proc/profile
2115 Format: [schedule,]<number>
2116 Param: "schedule" - profile schedule points.
2117 Param: <number> - step/bucket size as a power of 2 for
2118 statistical time based profiling.
2119 Param: "sleep" - profile D-state sleeping (millisecs).
2120 Requires CONFIG_SCHEDSTATS
2121 Param: "kvm" - profile VM exits.
2123 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2124 before loading.
2125 See Documentation/blockdev/ramdisk.txt.
2127 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2128 probe for; one of (bare|imps|exps|lifebook|any).
2129 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2130 per second.
2131 psmouse.resetafter= [HW,MOUSE]
2132 Try to reset the device after so many bad packets
2133 (0 = never).
2134 psmouse.resolution=
2135 [HW,MOUSE] Set desired mouse resolution, in dpi.
2136 psmouse.smartscroll=
2137 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2138 0 = disabled, 1 = enabled (default).
2140 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2141 Format:
2142 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2144 pt. [PARIDE]
2145 See Documentation/blockdev/paride.txt.
2147 pty.legacy_count=
2148 [KNL] Number of legacy pty's. Overwrites compiled-in
2149 default number.
2151 quiet [KNL] Disable most log messages
2153 r128= [HW,DRM]
2155 raid= [HW,RAID]
2156 See Documentation/md.txt.
2158 ramdisk_blocksize= [RAM]
2159 See Documentation/blockdev/ramdisk.txt.
2161 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2162 See Documentation/blockdev/ramdisk.txt.
2164 rcupdate.blimit= [KNL,BOOT]
2165 Set maximum number of finished RCU callbacks to process
2166 in one batch.
2168 rcupdate.qhimark= [KNL,BOOT]
2169 Set threshold of queued
2170 RCU callbacks over which batch limiting is disabled.
2172 rcupdate.qlowmark= [KNL,BOOT]
2173 Set threshold of queued RCU callbacks below which
2174 batch limiting is re-enabled.
2176 rdinit= [KNL]
2177 Format: <full_path>
2178 Run specified binary instead of /init from the ramdisk,
2179 used for early userspace startup. See initrd.
2181 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2182 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2183 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2185 relax_domain_level=
2186 [KNL, SMP] Set scheduler's default relax_domain_level.
2187 See Documentation/cgroups/cpusets.txt.
2189 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2191 reservetop= [X86-32]
2192 Format: nn[KMG]
2193 Reserves a hole at the top of the kernel virtual
2194 address space.
2196 reset_devices [KNL] Force drivers to reset the underlying device
2197 during initialization.
2199 resume= [SWSUSP]
2200 Specify the partition device for software suspend
2202 resume_offset= [SWSUSP]
2203 Specify the offset from the beginning of the partition
2204 given by "resume=" at which the swap header is located,
2205 in <PAGE_SIZE> units (needed only for swap files).
2206 See Documentation/power/swsusp-and-swap-files.txt
2208 retain_initrd [RAM] Keep initrd memory after extraction
2210 rhash_entries= [KNL,NET]
2211 Set number of hash buckets for route cache
2213 riscom8= [HW,SERIAL]
2214 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2216 ro [KNL] Mount root device read-only on boot
2218 root= [KNL] Root filesystem
2220 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2221 mount the root filesystem
2223 rootflags= [KNL] Set root filesystem mount option string
2225 rootfstype= [KNL] Set root filesystem type
2227 rootwait [KNL] Wait (indefinitely) for root device to show up.
2228 Useful for devices that are detected asynchronously
2229 (e.g. USB and MMC devices).
2231 rw [KNL] Mount root device read-write on boot
2233 S [KNL] Run init in single mode
2235 sa1100ir [NET]
2236 See drivers/net/irda/sa1100_ir.c.
2238 sbni= [NET] Granch SBNI12 leased line adapter
2240 sched_debug [KNL] Enables verbose scheduler debug messages.
2242 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2243 Format: <io>[,<timeout>[,<isapnp>]]
2245 scsi_debug_*= [SCSI]
2246 See drivers/scsi/scsi_debug.c.
2248 scsi_default_dev_flags=
2249 [SCSI] SCSI default device flags
2250 Format: <integer>
2252 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2253 Format: <vendor>:<model>:<flags>
2254 (flags are integer value)
2256 scsi_logging_level= [SCSI] a bit mask of logging levels
2257 See drivers/scsi/scsi_logging.h for bits. Also
2258 settable via sysctl at dev.scsi.logging_level
2259 (/proc/sys/dev/scsi/logging_level).
2260 There is also a nice 'scsi_logging_level' script in the
2261 S390-tools package, available for download at
2262 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2264 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2265 discovered. async scans them in kernel threads,
2266 allowing boot to proceed. none ignores them, expecting
2267 user space to do the scan.
2269 security= [SECURITY] Choose a security module to enable at boot.
2270 If this boot parameter is not specified, only the first
2271 security module asking for security registration will be
2272 loaded. An invalid security module name will be treated
2273 as if no module has been chosen.
2275 selinux= [SELINUX] Disable or enable SELinux at boot time.
2276 Format: { "0" | "1" }
2277 See security/selinux/Kconfig help text.
2278 0 -- disable.
2279 1 -- enable.
2280 Default value is set via kernel config option.
2281 If enabled at boot time, /selinux/disable can be used
2282 later to disable prior to initial policy load.
2284 serialnumber [BUGS=X86-32]
2286 shapers= [NET]
2287 Maximal number of shapers.
2289 show_msr= [x86] show boot-time MSR settings
2290 Format: { <integer> }
2291 Show boot-time (BIOS-initialized) MSR settings.
2292 The parameter means the number of CPUs to show,
2293 for example 1 means boot CPU only.
2295 sim710= [SCSI,HW]
2296 See header of drivers/scsi/sim710.c.
2298 simeth= [IA-64]
2299 simscsi=
2301 slram= [HW,MTD]
2303 slub_debug[=options[,slabs]] [MM, SLUB]
2304 Enabling slub_debug allows one to determine the
2305 culprit if slab objects become corrupted. Enabling
2306 slub_debug can create guard zones around objects and
2307 may poison objects when not in use. Also tracks the
2308 last alloc / free. For more information see
2309 Documentation/vm/slub.txt.
2311 slub_max_order= [MM, SLUB]
2312 Determines the maximum allowed order for slabs.
2313 A high setting may cause OOMs due to memory
2314 fragmentation. For more information see
2315 Documentation/vm/slub.txt.
2317 slub_min_objects= [MM, SLUB]
2318 The minimum number of objects per slab. SLUB will
2319 increase the slab order up to slub_max_order to
2320 generate a sufficiently large slab able to contain
2321 the number of objects indicated. The higher the number
2322 of objects the smaller the overhead of tracking slabs
2323 and the less frequently locks need to be acquired.
2324 For more information see Documentation/vm/slub.txt.
2326 slub_min_order= [MM, SLUB]
2327 Determines the mininum page order for slabs. Must be
2328 lower than slub_max_order.
2329 For more information see Documentation/vm/slub.txt.
2331 slub_nomerge [MM, SLUB]
2332 Disable merging of slabs with similar size. May be
2333 necessary if there is some reason to distinguish
2334 allocs to different slabs. Debug options disable
2335 merging on their own.
2336 For more information see Documentation/vm/slub.txt.
2338 smart2= [HW]
2339 Format: <io1>[,<io2>[,...,<io8>]]
2341 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2342 attempt to substitute SMP alternatives once at boot.
2344 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2345 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2346 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2347 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2348 smsc-ircc2.ircc_irq= [HW] IRQ line
2349 smsc-ircc2.ircc_dma= [HW] DMA channel
2350 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2351 0: Toshiba Satellite 1800 (GP data pin select)
2352 1: Fast pin select (default)
2353 2: ATC IRMode
2355 snd-ad1816a= [HW,ALSA]
2357 snd-ad1848= [HW,ALSA]
2359 snd-ali5451= [HW,ALSA]
2361 snd-als100= [HW,ALSA]
2363 snd-als4000= [HW,ALSA]
2365 snd-azt2320= [HW,ALSA]
2367 snd-cmi8330= [HW,ALSA]
2369 snd-cmipci= [HW,ALSA]
2371 snd-cs4231= [HW,ALSA]
2373 snd-cs4232= [HW,ALSA]
2375 snd-cs4236= [HW,ALSA]
2377 snd-cs4281= [HW,ALSA]
2379 snd-cs46xx= [HW,ALSA]
2381 snd-dt019x= [HW,ALSA]
2383 snd-dummy= [HW,ALSA]
2385 snd-emu10k1= [HW,ALSA]
2387 snd-ens1370= [HW,ALSA]
2389 snd-ens1371= [HW,ALSA]
2391 snd-es968= [HW,ALSA]
2393 snd-es1688= [HW,ALSA]
2395 snd-es18xx= [HW,ALSA]
2397 snd-es1938= [HW,ALSA]
2399 snd-es1968= [HW,ALSA]
2401 snd-fm801= [HW,ALSA]
2403 snd-gusclassic= [HW,ALSA]
2405 snd-gusextreme= [HW,ALSA]
2407 snd-gusmax= [HW,ALSA]
2409 snd-hdsp= [HW,ALSA]
2411 snd-ice1712= [HW,ALSA]
2413 snd-intel8x0= [HW,ALSA]
2415 snd-interwave= [HW,ALSA]
2417 snd-interwave-stb=
2418 [HW,ALSA]
2420 snd-korg1212= [HW,ALSA]
2422 snd-maestro3= [HW,ALSA]
2424 snd-mpu401= [HW,ALSA]
2426 snd-mtpav= [HW,ALSA]
2428 snd-nm256= [HW,ALSA]
2430 snd-opl3sa2= [HW,ALSA]
2432 snd-opti92x-ad1848=
2433 [HW,ALSA]
2435 snd-opti92x-cs4231=
2436 [HW,ALSA]
2438 snd-opti93x= [HW,ALSA]
2440 snd-pmac= [HW,ALSA]
2442 snd-rme32= [HW,ALSA]
2444 snd-rme96= [HW,ALSA]
2446 snd-rme9652= [HW,ALSA]
2448 snd-sb8= [HW,ALSA]
2450 snd-sb16= [HW,ALSA]
2452 snd-sbawe= [HW,ALSA]
2454 snd-serial= [HW,ALSA]
2456 snd-sgalaxy= [HW,ALSA]
2458 snd-sonicvibes= [HW,ALSA]
2460 snd-sun-amd7930=
2461 [HW,ALSA]
2463 snd-sun-cs4231= [HW,ALSA]
2465 snd-trident= [HW,ALSA]
2467 snd-usb-audio= [HW,ALSA,USB]
2469 snd-via82xx= [HW,ALSA]
2471 snd-virmidi= [HW,ALSA]
2473 snd-wavefront= [HW,ALSA]
2475 snd-ymfpci= [HW,ALSA]
2477 softlockup_panic=
2478 [KNL] Should the soft-lockup detector generate panics.
2480 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2481 See Documentation/sonypi.txt
2483 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2484 See Documentation/serial/specialix.txt.
2486 spia_io_base= [HW,MTD]
2487 spia_fio_base=
2488 spia_pedr=
2489 spia_peddr=
2491 sscape= [HW,OSS]
2492 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2494 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2495 See Documentation/scsi/st.txt.
2497 stacktrace [FTRACE]
2498 Enabled the stack tracer on boot up.
2500 sti= [PARISC,HW]
2501 Format: <num>
2502 Set the STI (builtin display/keyboard on the HP-PARISC
2503 machines) console (graphic card) which should be used
2504 as the initial boot-console.
2505 See also comment in drivers/video/console/sticore.c.
2507 sti_font= [HW]
2508 See comment in drivers/video/console/sticore.c.
2510 stifb= [HW]
2511 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2513 sunrpc.min_resvport=
2514 sunrpc.max_resvport=
2515 [NFS,SUNRPC]
2516 SunRPC servers often require that client requests
2517 originate from a privileged port (i.e. a port in the
2518 range 0 < portnr < 1024).
2519 An administrator who wishes to reserve some of these
2520 ports for other uses may adjust the range that the
2521 kernel's sunrpc client considers to be privileged
2522 using these two parameters to set the minimum and
2523 maximum port values.
2525 sunrpc.pool_mode=
2526 [NFS]
2527 Control how the NFS server code allocates CPUs to
2528 service thread pools. Depending on how many NICs
2529 you have and where their interrupts are bound, this
2530 option will affect which CPUs will do NFS serving.
2531 Note: this parameter cannot be changed while the
2532 NFS server is running.
2534 auto the server chooses an appropriate mode
2535 automatically using heuristics
2536 global a single global pool contains all CPUs
2537 percpu one pool for each CPU
2538 pernode one pool for each NUMA node (equivalent
2539 to global on non-NUMA machines)
2541 sunrpc.tcp_slot_table_entries=
2542 sunrpc.udp_slot_table_entries=
2543 [NFS,SUNRPC]
2544 Sets the upper limit on the number of simultaneous
2545 RPC calls that can be sent from the client to a
2546 server. Increasing these values may allow you to
2547 improve throughput, but will also increase the
2548 amount of memory reserved for use by the client.
2550 swiotlb= [IA-64] Number of I/O TLB slabs
2552 switches= [HW,M68k]
2554 sym53c416= [HW,SCSI]
2555 See header of drivers/scsi/sym53c416.c.
2557 sysrq_always_enabled
2558 [KNL]
2559 Ignore sysrq setting - this boot parameter will
2560 neutralize any effect of /proc/sys/kernel/sysrq.
2561 Useful for debugging.
2563 t128= [HW,SCSI]
2564 See header of drivers/scsi/t128.c.
2566 tdfx= [HW,DRM]
2568 test_suspend= [SUSPEND]
2569 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2570 standby suspend) as the system sleep state to briefly
2571 enter during system startup. The system is woken from
2572 this state using a wakeup-capable RTC alarm.
2574 thash_entries= [KNL,NET]
2575 Set number of hash buckets for TCP connection
2577 thermal.act= [HW,ACPI]
2578 -1: disable all active trip points in all thermal zones
2579 <degrees C>: override all lowest active trip points
2581 thermal.crt= [HW,ACPI]
2582 -1: disable all critical trip points in all thermal zones
2583 <degrees C>: override all critical trip points
2585 thermal.nocrt= [HW,ACPI]
2586 Set to disable actions on ACPI thermal zone
2587 critical and hot trip points.
2589 thermal.off= [HW,ACPI]
2590 1: disable ACPI thermal control
2592 thermal.psv= [HW,ACPI]
2593 -1: disable all passive trip points
2594 <degrees C>: override all passive trip points to this
2595 value
2597 thermal.tzp= [HW,ACPI]
2598 Specify global default ACPI thermal zone polling rate
2599 <deci-seconds>: poll all this frequency
2600 0: no polling (default)
2602 tmscsim= [HW,SCSI]
2603 See comment before function dc390_setup() in
2604 drivers/scsi/tmscsim.c.
2606 topology= [S390]
2607 Format: {off | on}
2608 Specify if the kernel should make use of the cpu
2609 topology informations if the hardware supports these.
2610 The scheduler will make use of these informations and
2611 e.g. base its process migration decisions on it.
2612 Default is off.
2614 tp720= [HW,PS2]
2616 trace_buf_size=nn[KMG]
2617 [FTRACE] will set tracing buffer size.
2619 trace_event=[event-list]
2620 [FTRACE] Set and start specified trace events in order
2621 to facilitate early boot debugging.
2622 See also Documentation/trace/events.txt
2624 trix= [HW,OSS] MediaTrix AudioTrix Pro
2625 Format:
2626 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2628 tsc= Disable clocksource-must-verify flag for TSC.
2629 Format: <string>
2630 [x86] reliable: mark tsc clocksource as reliable, this
2631 disables clocksource verification at runtime.
2632 Used to enable high-resolution timer mode on older
2633 hardware, and in virtualized environment.
2635 turbografx.map[2|3]= [HW,JOY]
2636 TurboGraFX parallel port interface
2637 Format:
2638 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2639 See also Documentation/input/joystick-parport.txt
2641 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2642 See header of drivers/scsi/u14-34f.c.
2644 uart401= [HW,OSS]
2645 Format: <io>,<irq>
2647 uart6850= [HW,OSS]
2648 Format: <io>,<irq>
2650 uhash_entries= [KNL,NET]
2651 Set number of hash buckets for UDP/UDP-Lite connections
2653 uhci-hcd.ignore_oc=
2654 [USB] Ignore overcurrent events (default N).
2655 Some badly-designed motherboards generate lots of
2656 bogus events, for ports that aren't wired to
2657 anything. Set this parameter to avoid log spamming.
2658 Note that genuine overcurrent events won't be
2659 reported either.
2661 unknown_nmi_panic
2662 [X86]
2663 Set unknown_nmi_panic=1 early on boot.
2665 usbcore.autosuspend=
2666 [USB] The autosuspend time delay (in seconds) used
2667 for newly-detected USB devices (default 2). This
2668 is the time required before an idle device will be
2669 autosuspended. Devices for which the delay is set
2670 to a negative value won't be autosuspended at all.
2672 usbcore.usbfs_snoop=
2673 [USB] Set to log all usbfs traffic (default 0 = off).
2675 usbcore.blinkenlights=
2676 [USB] Set to cycle leds on hubs (default 0 = off).
2678 usbcore.old_scheme_first=
2679 [USB] Start with the old device initialization
2680 scheme (default 0 = off).
2682 usbcore.use_both_schemes=
2683 [USB] Try the other device initialization scheme
2684 if the first one fails (default 1 = enabled).
2686 usbcore.initial_descriptor_timeout=
2687 [USB] Specifies timeout for the initial 64-byte
2688 USB_REQ_GET_DESCRIPTOR request in milliseconds
2689 (default 5000 = 5.0 seconds).
2691 usbhid.mousepoll=
2692 [USBHID] The interval which mice are to be polled at.
2694 usb-storage.delay_use=
2695 [UMS] The delay in seconds before a new device is
2696 scanned for Logical Units (default 5).
2698 usb-storage.quirks=
2699 [UMS] A list of quirks entries to supplement or
2700 override the built-in unusual_devs list. List
2701 entries are separated by commas. Each entry has
2702 the form VID:PID:Flags where VID and PID are Vendor
2703 and Product ID values (4-digit hex numbers) and
2704 Flags is a set of characters, each corresponding
2705 to a common usb-storage quirk flag as follows:
2706 a = SANE_SENSE (collect more than 18 bytes
2707 of sense data);
2708 b = BAD_SENSE (don't collect more than 18
2709 bytes of sense data);
2710 c = FIX_CAPACITY (decrease the reported
2711 device capacity by one sector);
2712 h = CAPACITY_HEURISTICS (decrease the
2713 reported device capacity by one
2714 sector if the number is odd);
2715 i = IGNORE_DEVICE (don't bind to this
2716 device);
2717 l = NOT_LOCKABLE (don't try to lock and
2718 unlock ejectable media);
2719 m = MAX_SECTORS_64 (don't transfer more
2720 than 64 sectors = 32 KB at a time);
2721 o = CAPACITY_OK (accept the capacity
2722 reported by the device);
2723 r = IGNORE_RESIDUE (the device reports
2724 bogus residue values);
2725 s = SINGLE_LUN (the device has only one
2726 Logical Unit);
2727 w = NO_WP_DETECT (don't test whether the
2728 medium is write-protected).
2729 Example: quirks=0419:aaf5:rl,0421:0433:rc
2731 userpte=
2732 [X86] Flags controlling user PTE allocations.
2734 nohigh = do not allocate PTE pages in
2735 HIGHMEM regardless of setting
2736 of CONFIG_HIGHPTE.
2738 vdso= [X86,SH]
2739 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2740 vdso=1: enable VDSO (default)
2741 vdso=0: disable VDSO mapping
2743 vdso32= [X86]
2744 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2745 vdso32=1: enable 32-bit VDSO (default)
2746 vdso32=0: disable 32-bit VDSO mapping
2748 vector= [IA-64,SMP]
2749 vector=percpu: enable percpu vector domain
2751 video= [FB] Frame buffer configuration
2752 See Documentation/fb/modedb.txt.
2754 vga= [BOOT,X86-32] Select a particular video mode
2755 See Documentation/x86/boot.txt and
2756 Documentation/svga.txt.
2757 Use vga=ask for menu.
2758 This is actually a boot loader parameter; the value is
2759 passed to the kernel using a special protocol.
2761 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2762 size of <nn>. This can be used to increase the
2763 minimum size (128MB on x86). It can also be used to
2764 decrease the size and leave more room for directly
2765 mapped kernel RAM.
2767 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2768 Format: <command>
2770 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2771 Format: <command>
2773 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2774 Format: <command>
2776 vt.cur_default= [VT] Default cursor shape.
2777 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2778 the parameters of the <Esc>[?A;B;Cc escape sequence;
2779 see VGA-softcursor.txt. Default: 2 = underline.
2781 vt.default_blu= [VT]
2782 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2783 Change the default blue palette of the console.
2784 This is a 16-member array composed of values
2785 ranging from 0-255.
2787 vt.default_grn= [VT]
2788 Format: <green0>,<green1>,<green2>,...,<green15>
2789 Change the default green palette of the console.
2790 This is a 16-member array composed of values
2791 ranging from 0-255.
2793 vt.default_red= [VT]
2794 Format: <red0>,<red1>,<red2>,...,<red15>
2795 Change the default red palette of the console.
2796 This is a 16-member array composed of values
2797 ranging from 0-255.
2799 vt.default_utf8=
2800 [VT]
2801 Format=<0|1>
2802 Set system-wide default UTF-8 mode for all tty's.
2803 Default is 1, i.e. UTF-8 mode is enabled for all
2804 newly opened terminals.
2806 vt.global_cursor_default=
2807 [VT]
2808 Format=<-1|0|1>
2809 Set system-wide default for whether a cursor
2810 is shown on new VTs. Default is -1,
2811 i.e. cursors will be created by default unless
2812 overridden by individual drivers. 0 will hide
2813 cursors, 1 will display them.
2815 waveartist= [HW,OSS]
2816 Format: <io>,<irq>,<dma>,<dma2>
2818 wd33c93= [HW,SCSI]
2819 See header of drivers/scsi/wd33c93.c.
2821 wd7000= [HW,SCSI]
2822 See header of drivers/scsi/wd7000.c.
2824 wdt= [WDT] Watchdog
2825 See Documentation/watchdog/wdt.txt.
2827 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2828 default x2apic cluster mode on platforms
2829 supporting x2apic.
2831 x86_mrst_timer= [X86-32,APBT]
2832 Choose timer option for x86 Moorestown MID platform.
2833 Two valid options are apbt timer only and lapic timer
2834 plus one apbt timer for broadcast timer.
2835 x86_mrst_timer=apbt_only | lapic_and_apbt
2837 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2838 xd_geo= See header of drivers/block/xd.c.
2840 xirc2ps_cs= [NET,PCMCIA]
2841 Format:
2842 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2844 ______________________________________________________________________
2846 TODO:
2848 Add documentation for ALSA options.
2849 Add more DRM drivers.