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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 GCOV GCOV profiling is enabled.
52 HW Appropriate hardware is enabled.
53 IA-64 IA-64 architecture is enabled.
54 IMA Integrity measurement architecture is enabled.
55 IOSCHED More than one I/O scheduler is enabled.
56 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
57 IPV6 IPv6 support is enabled.
58 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
61 KVM Kernel Virtual Machine support is enabled.
62 LIBATA Libata driver is enabled
63 LP Printer support is enabled.
64 LOOP Loopback device support is enabled.
65 M68k M68k architecture is enabled.
66 These options have more detailed description inside of
67 Documentation/m68k/kernel-options.txt.
68 MCA MCA bus support is enabled.
69 MDA MDA console support is enabled.
70 MOUSE Appropriate mouse support is enabled.
71 MSI Message Signaled Interrupts (PCI).
72 MTD MTD (Memory Technology Device) support is enabled.
73 NET Appropriate network support is enabled.
74 NUMA NUMA support is enabled.
75 GENERIC_TIME The generic timeofday code is enabled.
76 NFS Appropriate NFS support is enabled.
77 OSS OSS sound support is enabled.
78 PV_OPS A paravirtualized kernel is enabled.
79 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
80 PARISC The PA-RISC architecture is enabled.
81 PCI PCI bus support is enabled.
82 PCIE PCI Express support is enabled.
83 PCMCIA The PCMCIA subsystem is enabled.
84 PNP Plug & Play support is enabled.
85 PPC PowerPC architecture is enabled.
86 PPT Parallel port support is enabled.
87 PS2 Appropriate PS/2 support is enabled.
88 RAM RAM disk support is enabled.
89 S390 S390 architecture is enabled.
90 SCSI Appropriate SCSI support is enabled.
91 A lot of drivers has their options described inside of
92 Documentation/scsi/.
93 SECURITY Different security models are enabled.
94 SELINUX SELinux support is enabled.
95 SERIAL Serial support is enabled.
96 SH SuperH architecture is enabled.
97 SMP The kernel is an SMP kernel.
98 SPARC Sparc architecture is enabled.
99 SWSUSP Software suspend (hibernation) is enabled.
100 SUSPEND System suspend states are enabled.
101 FTRACE Function tracing enabled.
102 TPM TPM drivers are enabled.
103 TS Appropriate touchscreen support is enabled.
104 UMS USB Mass Storage support is enabled.
105 USB USB support is enabled.
106 USBHID USB Human Interface Device support is enabled.
107 V4L Video For Linux support is enabled.
108 VGA The VGA console has been enabled.
109 VT Virtual terminal support is enabled.
110 WDT Watchdog support is enabled.
111 XT IBM PC/XT MFM hard disk support is enabled.
112 X86-32 X86-32, aka i386 architecture is enabled.
113 X86-64 X86-64 architecture is enabled.
114 More X86-64 boot options can be found in
115 Documentation/x86/x86_64/boot-options.txt .
116 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
118 In addition, the following text indicates that the option:
120 BUGS= Relates to possible processor bugs on the said processor.
121 KNL Is a kernel start-up parameter.
122 BOOT Is a boot loader parameter.
124 Parameters denoted with BOOT are actually interpreted by the boot
125 loader, and have no meaning to the kernel directly.
126 Do not modify the syntax of boot loader parameters without extreme
127 need or coordination with <Documentation/x86/boot.txt>.
129 There are also arch-specific kernel-parameters not documented here.
130 See for example <Documentation/x86/x86_64/boot-options.txt>.
132 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
133 a trailing = on the name of any parameter states that that parameter will
134 be entered as an environment variable, whereas its absence indicates that
135 it will appear as a kernel argument readable via /proc/cmdline by programs
136 running once the system is up.
138 The number of kernel parameters is not limited, but the length of the
139 complete command line (parameters including spaces etc.) is limited to
140 a fixed number of characters. This limit depends on the architecture
141 and is between 256 and 4096 characters. It is defined in the file
142 ./include/asm/setup.h as COMMAND_LINE_SIZE.
145 acpi= [HW,ACPI,X86]
146 Advanced Configuration and Power Interface
147 Format: { force | off | ht | strict | noirq | rsdt }
148 force -- enable ACPI if default was off
149 off -- disable ACPI if default was on
150 noirq -- do not use ACPI for IRQ routing
151 ht -- run only enough ACPI to enable Hyper Threading
152 strict -- Be less tolerant of platforms that are not
153 strictly ACPI specification compliant.
154 rsdt -- prefer RSDT over (default) XSDT
156 See also Documentation/power/pm.txt, pci=noacpi
158 acpi_apic_instance= [ACPI, IOAPIC]
159 Format: <int>
160 2: use 2nd APIC table, if available
161 1,0: use 1st APIC table
162 default: 0
164 acpi_backlight= [HW,ACPI]
165 acpi_backlight=vendor
166 acpi_backlight=video
167 If set to vendor, prefer vendor specific driver
168 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
169 of the ACPI video.ko driver.
171 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
172 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
173 Format: <int>
174 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
175 debug output. Bits in debug_layer correspond to a
176 _COMPONENT in an ACPI source file, e.g.,
177 #define _COMPONENT ACPI_PCI_COMPONENT
178 Bits in debug_level correspond to a level in
179 ACPI_DEBUG_PRINT statements, e.g.,
180 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
181 The debug_level mask defaults to "info". See
182 Documentation/acpi/debug.txt for more information about
183 debug layers and levels.
185 Enable processor driver info messages:
186 acpi.debug_layer=0x20000000
187 Enable PCI/PCI interrupt routing info messages:
188 acpi.debug_layer=0x400000
189 Enable AML "Debug" output, i.e., stores to the Debug
190 object while interpreting AML:
191 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
192 Enable all messages related to ACPI hardware:
193 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
195 Some values produce so much output that the system is
196 unusable. The "log_buf_len" parameter may be useful
197 if you need to capture more output.
199 acpi_display_output= [HW,ACPI]
200 acpi_display_output=vendor
201 acpi_display_output=video
202 See above.
204 acpi_irq_balance [HW,ACPI]
205 ACPI will balance active IRQs
206 default in APIC mode
208 acpi_irq_nobalance [HW,ACPI]
209 ACPI will not move active IRQs (default)
210 default in PIC mode
212 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
213 Format: <irq>,<irq>...
215 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
216 use by PCI
217 Format: <irq>,<irq>...
219 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
221 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
222 Format: To spoof as Windows 98: ="Microsoft Windows"
224 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
225 acpi_osi="string1" # add string1 -- only one string
226 acpi_osi="!string2" # remove built-in string2
227 acpi_osi= # disable all strings
229 acpi_pm_good [X86]
230 Override the pmtimer bug detection: force the kernel
231 to assume that this machine's pmtimer latches its value
232 and always returns good values.
234 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
235 Format: { level | edge | high | low }
237 acpi_serialize [HW,ACPI] force serialization of AML methods
239 acpi_skip_timer_override [HW,ACPI]
240 Recognize and ignore IRQ0/pin2 Interrupt Override.
241 For broken nForce2 BIOS resulting in XT-PIC timer.
243 acpi_sleep= [HW,ACPI] Sleep options
244 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
245 old_ordering, s4_nonvs, sci_force_enable }
246 See Documentation/power/video.txt for information on
247 s3_bios and s3_mode.
248 s3_beep is for debugging; it makes the PC's speaker beep
249 as soon as the kernel's real-mode entry point is called.
250 s4_nohwsig prevents ACPI hardware signature from being
251 used during resume from hibernation.
252 old_ordering causes the ACPI 1.0 ordering of the _PTS
253 control method, with respect to putting devices into
254 low power states, to be enforced (the ACPI 2.0 ordering
255 of _PTS is used by default).
256 s4_nonvs prevents the kernel from saving/restoring the
257 ACPI NVS memory during hibernation.
258 sci_force_enable causes the kernel to set SCI_EN directly
259 on resume from S1/S3 (which is against the ACPI spec,
260 but some broken systems don't work without it).
262 acpi_use_timer_override [HW,ACPI]
263 Use timer override. For some broken Nvidia NF5 boards
264 that require a timer override, but don't have HPET
266 acpi_enforce_resources= [ACPI]
267 { strict | lax | no }
268 Check for resource conflicts between native drivers
269 and ACPI OperationRegions (SystemIO and SystemMemory
270 only). IO ports and memory declared in ACPI might be
271 used by the ACPI subsystem in arbitrary AML code and
272 can interfere with legacy drivers.
273 strict (default): access to resources claimed by ACPI
274 is denied; legacy drivers trying to access reserved
275 resources will fail to bind to device using them.
276 lax: access to resources claimed by ACPI is allowed;
277 legacy drivers trying to access reserved resources
278 will bind successfully but a warning message is logged.
279 no: ACPI OperationRegions are not marked as reserved,
280 no further checks are performed.
282 ad1848= [HW,OSS]
283 Format: <io>,<irq>,<dma>,<dma2>,<type>
285 add_efi_memmap [EFI; X86] Include EFI memory map in
286 kernel's map of available physical RAM.
288 advansys= [HW,SCSI]
289 See header of drivers/scsi/advansys.c.
291 advwdt= [HW,WDT] Advantech WDT
292 Format: <iostart>,<iostop>
294 aedsp16= [HW,OSS] Audio Excel DSP 16
295 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
296 See also header of sound/oss/aedsp16.c.
298 agp= [AGP]
299 { off | try_unsupported }
300 off: disable AGP support
301 try_unsupported: try to drive unsupported chipsets
302 (may crash computer or cause data corruption)
304 aha152x= [HW,SCSI]
305 See Documentation/scsi/aha152x.txt.
307 aha1542= [HW,SCSI]
308 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
310 aic7xxx= [HW,SCSI]
311 See Documentation/scsi/aic7xxx.txt.
313 aic79xx= [HW,SCSI]
314 See Documentation/scsi/aic79xx.txt.
316 alignment= [KNL,ARM]
317 Allow the default userspace alignment fault handler
318 behaviour to be specified. Bit 0 enables warnings,
319 bit 1 enables fixups, and bit 2 sends a segfault.
321 amd_iommu= [HW,X86-84]
322 Pass parameters to the AMD IOMMU driver in the system.
323 Possible values are:
324 fullflush - enable flushing of IO/TLB entries when
325 they are unmapped. Otherwise they are
326 flushed before they will be reused, which
327 is a lot of faster
329 amijoy.map= [HW,JOY] Amiga joystick support
330 Map of devices attached to JOY0DAT and JOY1DAT
331 Format: <a>,<b>
332 See also Documentation/kernel/input/joystick.txt
334 analog.map= [HW,JOY] Analog joystick and gamepad support
335 Specifies type or capabilities of an analog joystick
336 connected to one of 16 gameports
337 Format: <type1>,<type2>,..<type16>
339 apc= [HW,SPARC]
340 Power management functions (SPARCstation-4/5 + deriv.)
341 Format: noidle
342 Disable APC CPU standby support. SPARCstation-Fox does
343 not play well with APC CPU idle - disable it if you have
344 APC and your system crashes randomly.
346 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
347 Change the output verbosity whilst booting
348 Format: { quiet (default) | verbose | debug }
349 Change the amount of debugging information output
350 when initialising the APIC and IO-APIC components.
352 autoconf= [IPV6]
353 See Documentation/networking/ipv6.txt.
355 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
356 Limit apic dumping. The parameter defines the maximal
357 number of local apics being dumped. Also it is possible
358 to set it to "all" by meaning -- no limit here.
359 Format: { 1 (default) | 2 | ... | all }.
360 The parameter valid if only apic=debug or
361 apic=verbose is specified.
362 Example: apic=debug show_lapic=all
364 apm= [APM] Advanced Power Management
365 See header of arch/x86/kernel/apm_32.c.
367 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
368 Format: <io>,<irq>,<nodeID>
370 ataflop= [HW,M68k]
372 atarimouse= [HW,MOUSE] Atari Mouse
374 atascsi= [HW,SCSI] Atari SCSI
376 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
377 EzKey and similar keyboards
379 atkbd.reset= [HW] Reset keyboard during initialization
381 atkbd.set= [HW] Select keyboard code set
382 Format: <int> (2 = AT (default), 3 = PS/2)
384 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
385 keyboards
387 atkbd.softraw= [HW] Choose between synthetic and real raw mode
388 Format: <bool> (0 = real, 1 = synthetic (default))
390 atkbd.softrepeat= [HW]
391 Use software keyboard repeat
393 autotest [IA64]
395 baycom_epp= [HW,AX25]
396 Format: <io>,<mode>
398 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
399 Format: <io>,<mode>
400 See header of drivers/net/hamradio/baycom_par.c.
402 baycom_ser_fdx= [HW,AX25]
403 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
404 Format: <io>,<irq>,<mode>[,<baud>]
405 See header of drivers/net/hamradio/baycom_ser_fdx.c.
407 baycom_ser_hdx= [HW,AX25]
408 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
409 Format: <io>,<irq>,<mode>
410 See header of drivers/net/hamradio/baycom_ser_hdx.c.
412 boot_delay= Milliseconds to delay each printk during boot.
413 Values larger than 10 seconds (10000) are changed to
414 no delay (0).
415 Format: integer
417 bootmem_debug [KNL] Enable bootmem allocator debug messages.
419 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
420 bttv.radio= Most important insmod options are available as
421 kernel args too.
422 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
423 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
425 BusLogic= [HW,SCSI]
426 See drivers/scsi/BusLogic.c, comment before function
427 BusLogic_ParseDriverOptions().
429 c101= [NET] Moxa C101 synchronous serial card
431 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
432 Sometimes CPU hardware bugs make them report the cache
433 size incorrectly. The kernel will attempt work arounds
434 to fix known problems, but for some CPUs it is not
435 possible to determine what the correct size should be.
436 This option provides an override for these situations.
438 capability.disable=
439 [SECURITY] Disable capabilities. This would normally
440 be used only if an alternative security model is to be
441 configured. Potentially dangerous and should only be
442 used if you are entirely sure of the consequences.
444 ccw_timeout_log [S390]
445 See Documentation/s390/CommonIO for details.
447 cgroup_disable= [KNL] Disable a particular controller
448 Format: {name of the controller(s) to disable}
449 {Currently supported controllers - "memory"}
451 checkreqprot [SELINUX] Set initial checkreqprot flag value.
452 Format: { "0" | "1" }
453 See security/selinux/Kconfig help text.
454 0 -- check protection applied by kernel (includes
455 any implied execute protection).
456 1 -- check protection requested by application.
457 Default value is set via a kernel config option.
458 Value can be changed at runtime via
459 /selinux/checkreqprot.
461 cio_ignore= [S390]
462 See Documentation/s390/CommonIO for details.
464 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
465 [Deprecated]
466 Forces specified clocksource (if available) to be used
467 when calculating gettimeofday(). If specified
468 clocksource is not available, it defaults to PIT.
469 Format: { pit | tsc | cyclone | pmtmr }
471 clocksource= [GENERIC_TIME] Override the default clocksource
472 Format: <string>
473 Override the default clocksource and use the clocksource
474 with the name specified.
475 Some clocksource names to choose from, depending on
476 the platform:
477 [all] jiffies (this is the base, fallback clocksource)
478 [ACPI] acpi_pm
479 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
480 pxa_timer,timer3,32k_counter,timer0_1
481 [AVR32] avr32
482 [X86-32] pit,hpet,tsc,vmi-timer;
483 scx200_hrt on Geode; cyclone on IBM x440
484 [MIPS] MIPS
485 [PARISC] cr16
486 [S390] tod
487 [SH] SuperH
488 [SPARC64] tick
489 [X86-64] hpet,tsc
491 clearcpuid=BITNUM [X86]
492 Disable CPUID feature X for the kernel. See
493 arch/x86/include/asm/cpufeature.h for the valid bit
494 numbers. Note the Linux specific bits are not necessarily
495 stable over kernel options, but the vendor specific
496 ones should be.
497 Also note that user programs calling CPUID directly
498 or using the feature without checking anything
499 will still see it. This just prevents it from
500 being used by the kernel or shown in /proc/cpuinfo.
501 Also note the kernel might malfunction if you disable
502 some critical bits.
504 cmo_free_hint= [PPC] Format: { yes | no }
505 Specify whether pages are marked as being inactive
506 when they are freed. This is used in CMO environments
507 to determine OS memory pressure for page stealing by
508 a hypervisor.
509 Default: yes
511 code_bytes [X86] How many bytes of object code to print
512 in an oops report.
513 Range: 0 - 8192
514 Default: 64
516 com20020= [HW,NET] ARCnet - COM20020 chipset
517 Format:
518 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
520 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
521 Format: <io>[,<irq>]
523 com90xx= [HW,NET]
524 ARCnet - COM90xx chipset (memory-mapped buffers)
525 Format: <io>[,<irq>[,<memstart>]]
527 condev= [HW,S390] console device
528 conmode=
530 console= [KNL] Output console device and options.
532 tty<n> Use the virtual console device <n>.
534 ttyS<n>[,options]
535 ttyUSB0[,options]
536 Use the specified serial port. The options are of
537 the form "bbbbpnf", where "bbbb" is the baud rate,
538 "p" is parity ("n", "o", or "e"), "n" is number of
539 bits, and "f" is flow control ("r" for RTS or
540 omit it). Default is "9600n8".
542 See Documentation/serial-console.txt for more
543 information. See
544 Documentation/networking/netconsole.txt for an
545 alternative.
547 uart[8250],io,<addr>[,options]
548 uart[8250],mmio,<addr>[,options]
549 Start an early, polled-mode console on the 8250/16550
550 UART at the specified I/O port or MMIO address,
551 switching to the matching ttyS device later. The
552 options are the same as for ttyS, above.
554 If the device connected to the port is not a TTY but a braille
555 device, prepend "brl," before the device type, for instance
556 console=brl,ttyS0
557 For now, only VisioBraille is supported.
559 consoleblank= [KNL] The console blank (screen saver) timeout in
560 seconds. Defaults to 10*60 = 10mins. A value of 0
561 disables the blank timer.
563 coredump_filter=
564 [KNL] Change the default value for
565 /proc/<pid>/coredump_filter.
566 See also Documentation/filesystems/proc.txt.
568 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
569 Format:
570 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
572 crashkernel=nn[KMG]@ss[KMG]
573 [KNL] Reserve a chunk of physical memory to
574 hold a kernel to switch to with kexec on panic.
576 crashkernel=range1:size1[,range2:size2,...][@offset]
577 [KNL] Same as above, but depends on the memory
578 in the running system. The syntax of range is
579 start-[end] where start and end are both
580 a memory unit (amount[KMG]). See also
581 Documentation/kdump/kdump.txt for a example.
583 cs89x0_dma= [HW,NET]
584 Format: <dma>
586 cs89x0_media= [HW,NET]
587 Format: { rj45 | aui | bnc }
589 dasd= [HW,NET]
590 See header of drivers/s390/block/dasd_devmap.c.
592 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
593 (one device per port)
594 Format: <port#>,<type>
595 See also Documentation/input/joystick-parport.txt
597 debug [KNL] Enable kernel debugging (events log level).
599 debug_locks_verbose=
600 [KNL] verbose self-tests
601 Format=<0|1>
602 Print debugging info while doing the locking API
603 self-tests.
604 We default to 0 (no extra messages), setting it to
605 1 will print _a lot_ more information - normally
606 only useful to kernel developers.
608 debug_objects [KNL] Enable object debugging
610 no_debug_objects
611 [KNL] Disable object debugging
613 debugpat [X86] Enable PAT debugging
615 decnet.addr= [HW,NET]
616 Format: <area>[,<node>]
617 See also Documentation/networking/decnet.txt.
619 default_hugepagesz=
620 [same as hugepagesz=] The size of the default
621 HugeTLB page size. This is the size represented by
622 the legacy /proc/ hugepages APIs, used for SHM, and
623 default size when mounting hugetlbfs filesystems.
624 Defaults to the default architecture's huge page size
625 if not specified.
627 dhash_entries= [KNL]
628 Set number of hash buckets for dentry cache.
630 digi= [HW,SERIAL]
631 IO parameters + enable/disable command.
633 digiepca= [HW,SERIAL]
634 See drivers/char/README.epca and
635 Documentation/serial/digiepca.txt.
637 disable= [IPV6]
638 See Documentation/networking/ipv6.txt.
640 disable_ipv6= [IPV6]
641 See Documentation/networking/ipv6.txt.
643 disable_mtrr_cleanup [X86]
644 The kernel tries to adjust MTRR layout from continuous
645 to discrete, to make X server driver able to add WB
646 entry later. This parameter disables that.
648 disable_mtrr_trim [X86, Intel and AMD only]
649 By default the kernel will trim any uncacheable
650 memory out of your available memory pool based on
651 MTRR settings. This parameter disables that behavior,
652 possibly causing your machine to run very slowly.
654 disable_timer_pin_1 [X86]
655 Disable PIN 1 of APIC timer
656 Can be useful to work around chipset bugs.
658 dmasound= [HW,OSS] Sound subsystem buffers
660 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
661 this option disables the debugging code at boot.
663 dma_debug_entries=<number>
664 This option allows to tune the number of preallocated
665 entries for DMA-API debugging code. One entry is
666 required per DMA-API allocation. Use this if the
667 DMA-API debugging code disables itself because the
668 architectural default is too low.
670 dma_debug_driver=<driver_name>
671 With this option the DMA-API debugging driver
672 filter feature can be enabled at boot time. Just
673 pass the driver to filter for as the parameter.
674 The filter can be disabled or changed to another
675 driver later using sysfs.
677 dscc4.setup= [NET]
679 dtc3181e= [HW,SCSI]
681 dynamic_printk Enables pr_debug()/dev_dbg() calls if
682 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
683 These can also be switched on/off via
684 <debugfs>/dynamic_printk/modules
686 earlycon= [KNL] Output early console device and options.
687 uart[8250],io,<addr>[,options]
688 uart[8250],mmio,<addr>[,options]
689 Start an early, polled-mode console on the 8250/16550
690 UART at the specified I/O port or MMIO address.
691 The options are the same as for ttyS, above.
693 earlyprintk= [X86,SH,BLACKFIN]
694 earlyprintk=vga
695 earlyprintk=serial[,ttySn[,baudrate]]
696 earlyprintk=ttySn[,baudrate]
697 earlyprintk=dbgp[debugController#]
699 Append ",keep" to not disable it when the real console
700 takes over.
702 Only vga or serial or usb debug port at a time.
704 Currently only ttyS0 and ttyS1 are supported.
706 Interaction with the standard serial driver is not
707 very good.
709 The VGA output is eventually overwritten by the real
710 console.
712 eata= [HW,SCSI]
714 edd= [EDD]
715 Format: {"off" | "on" | "skip[mbr]"}
717 eisa_irq_edge= [PARISC,HW]
718 See header of drivers/parisc/eisa.c.
720 elanfreq= [X86-32]
721 See comment before function elanfreq_setup() in
722 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
724 elevator= [IOSCHED]
725 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
726 See Documentation/block/as-iosched.txt and
727 Documentation/block/deadline-iosched.txt for details.
729 elfcorehdr= [IA64,PPC,SH,X86]
730 Specifies physical address of start of kernel core
731 image elf header. Generally kexec loader will
732 pass this option to capture kernel.
733 See Documentation/kdump/kdump.txt for details.
735 enable_mtrr_cleanup [X86]
736 The kernel tries to adjust MTRR layout from continuous
737 to discrete, to make X server driver able to add WB
738 entry later. This parameter enables that.
740 enable_timer_pin_1 [X86]
741 Enable PIN 1 of APIC timer
742 Can be useful to work around chipset bugs
743 (in particular on some ATI chipsets).
744 The kernel tries to set a reasonable default.
746 enforcing [SELINUX] Set initial enforcing status.
747 Format: {"0" | "1"}
748 See security/selinux/Kconfig help text.
749 0 -- permissive (log only, no denials).
750 1 -- enforcing (deny and log).
751 Default value is 0.
752 Value can be changed at runtime via /selinux/enforce.
754 ether= [HW,NET] Ethernet cards parameters
755 This option is obsoleted by the "netdev=" option, which
756 has equivalent usage. See its documentation for details.
758 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
759 Format: <io>[,<irq>]
761 failslab=
762 fail_page_alloc=
763 fail_make_request=[KNL]
764 General fault injection mechanism.
765 Format: <interval>,<probability>,<space>,<times>
766 See also /Documentation/fault-injection/.
768 fd_mcs= [HW,SCSI]
769 See header of drivers/scsi/fd_mcs.c.
771 fdomain= [HW,SCSI]
772 See header of drivers/scsi/fdomain.c.
774 floppy= [HW]
775 See Documentation/blockdev/floppy.txt.
777 force_pal_cache_flush
778 [IA-64] Avoid check_sal_cache_flush which may hang on
779 buggy SAL_CACHE_FLUSH implementations. Using this
780 parameter will force ia64_sal_cache_flush to call
781 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
783 ftrace=[tracer]
784 [FTRACE] will set and start the specified tracer
785 as early as possible in order to facilitate early
786 boot debugging.
788 ftrace_dump_on_oops
789 [FTRACE] will dump the trace buffers on oops.
791 ftrace_filter=[function-list]
792 [FTRACE] Limit the functions traced by the function
793 tracer at boot up. function-list is a comma separated
794 list of functions. This list can be changed at run
795 time by the set_ftrace_filter file in the debugfs
796 tracing directory.
798 ftrace_notrace=[function-list]
799 [FTRACE] Do not trace the functions specified in
800 function-list. This list can be changed at run time
801 by the set_ftrace_notrace file in the debugfs
802 tracing directory.
804 ftrace_graph_filter=[function-list]
805 [FTRACE] Limit the top level callers functions traced
806 by the function graph tracer at boot up.
807 function-list is a comma separated list of functions
808 that can be changed at run time by the
809 set_graph_function file in the debugfs tracing directory.
811 gamecon.map[2|3]=
812 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
813 support via parallel port (up to 5 devices per port)
814 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
815 See also Documentation/input/joystick-parport.txt
817 gamma= [HW,DRM]
819 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
820 Format: off | on
821 default: on
823 gcov_persist= [GCOV] When non-zero (default), profiling data for
824 kernel modules is saved and remains accessible via
825 debugfs, even when the module is unloaded/reloaded.
826 When zero, profiling data is discarded and associated
827 debugfs files are removed at module unload time.
829 gdth= [HW,SCSI]
830 See header of drivers/scsi/gdth.c.
832 gpt [EFI] Forces disk with valid GPT signature but
833 invalid Protective MBR to be treated as GPT.
835 gvp11= [HW,SCSI]
837 hashdist= [KNL,NUMA] Large hashes allocated during boot
838 are distributed across NUMA nodes. Defaults on
839 for 64bit NUMA, off otherwise.
840 Format: 0 | 1 (for off | on)
842 hcl= [IA-64] SGI's Hardware Graph compatibility layer
844 hd= [EIDE] (E)IDE hard drive subsystem geometry
845 Format: <cyl>,<head>,<sect>
847 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
848 size of <nn>. This works even on boxes that have no
849 highmem otherwise. This also works to reduce highmem
850 size on bigger boxes.
852 highres= [KNL] Enable/disable high resolution timer mode.
853 Valid parameters: "on", "off"
854 Default: "on"
856 hisax= [HW,ISDN]
857 See Documentation/isdn/README.HiSax.
859 hlt [BUGS=ARM,SH]
861 hpet= [X86-32,HPET] option to control HPET usage
862 Format: { enable (default) | disable | force |
863 verbose }
864 disable: disable HPET and use PIT instead
865 force: allow force enabled of undocumented chips (ICH4,
866 VIA, nVidia)
867 verbose: show contents of HPET registers during setup
869 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
870 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
871 On x86-64 and powerpc, this option can be specified
872 multiple times interleaved with hugepages= to reserve
873 huge pages of different sizes. Valid pages sizes on
874 x86-64 are 2M (when the CPU supports "pse") and 1G
875 (when the CPU supports the "pdpe1gb" cpuinfo flag)
876 Note that 1GB pages can only be allocated at boot time
877 using hugepages= and not freed afterwards.
879 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
880 terminal devices. Valid values: 0..8
881 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
882 If specified, z/VM IUCV HVC accepts connections
883 from listed z/VM user IDs only.
885 i2c_bus= [HW] Override the default board specific I2C bus speed
886 or register an additional I2C bus that is not
887 registered from board initialization code.
888 Format:
889 <bus_id>,<clkrate>
891 i8042.debug [HW] Toggle i8042 debug mode
892 i8042.direct [HW] Put keyboard port into non-translated mode
893 i8042.dumbkbd [HW] Pretend that controller can only read data from
894 keyboard and cannot control its state
895 (Don't attempt to blink the leds)
896 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
897 i8042.nokbd [HW] Don't check/create keyboard port
898 i8042.noloop [HW] Disable the AUX Loopback command while probing
899 for the AUX port
900 i8042.nomux [HW] Don't check presence of an active multiplexing
901 controller
902 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
903 controllers
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 off Do not use native PCIe PME signaling.
2018 force Use native PCIe PME signaling even if the BIOS refuses
2019 to allow the kernel to control the relevant PCIe config
2020 registers.
2021 nomsi Do not use MSI for native PCIe PME signaling (this makes
2022 all PCIe root ports use INTx for everything).
2024 pcmv= [HW,PCMCIA] BadgePAD 4
2026 pd. [PARIDE]
2027 See Documentation/blockdev/paride.txt.
2029 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2030 boot time.
2031 Format: { 0 | 1 }
2032 See arch/parisc/kernel/pdc_chassis.c
2034 percpu_alloc= Select which percpu first chunk allocator to use.
2035 Currently supported values are "embed" and "page".
2036 Archs may support subset or none of the selections.
2037 See comments in mm/percpu.c for details on each
2038 allocator. This parameter is primarily for debugging
2039 and performance comparison.
2041 pf. [PARIDE]
2042 See Documentation/blockdev/paride.txt.
2044 pg. [PARIDE]
2045 See Documentation/blockdev/paride.txt.
2047 pirq= [SMP,APIC] Manual mp-table setup
2048 See Documentation/x86/i386/IO-APIC.txt.
2050 plip= [PPT,NET] Parallel port network link
2051 Format: { parport<nr> | timid | 0 }
2052 See also Documentation/parport.txt.
2054 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2055 Override pmtimer IOPort with a hex value.
2056 e.g. pmtmr=0x508
2058 pnp.debug [PNP]
2059 Enable PNP debug messages. This depends on the
2060 CONFIG_PNP_DEBUG_MESSAGES option.
2062 pnpacpi= [ACPI]
2063 { off }
2065 pnpbios= [ISAPNP]
2066 { on | off | curr | res | no-curr | no-res }
2068 pnp_reserve_irq=
2069 [ISAPNP] Exclude IRQs for the autoconfiguration
2071 pnp_reserve_dma=
2072 [ISAPNP] Exclude DMAs for the autoconfiguration
2074 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2075 Ranges are in pairs (I/O port base and size).
2077 pnp_reserve_mem=
2078 [ISAPNP] Exclude memory regions for the
2079 autoconfiguration.
2080 Ranges are in pairs (memory base and size).
2082 ports= [IP_VS_FTP] IPVS ftp helper module
2083 Default is 21.
2084 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2085 may be specified.
2086 Format: <port>,<port>....
2088 print-fatal-signals=
2089 [KNL] debug: print fatal signals
2091 If enabled, warn about various signal handling
2092 related application anomalies: too many signals,
2093 too many POSIX.1 timers, fatal signals causing a
2094 coredump - etc.
2096 If you hit the warning due to signal overflow,
2097 you might want to try "ulimit -i unlimited".
2099 default: off.
2101 printk.time= Show timing data prefixed to each printk message line
2102 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2104 processor.max_cstate= [HW,ACPI]
2105 Limit processor to maximum C-state
2106 max_cstate=9 overrides any DMI blacklist limit.
2108 processor.nocst [HW,ACPI]
2109 Ignore the _CST method to determine C-states,
2110 instead using the legacy FADT method
2112 profile= [KNL] Enable kernel profiling via /proc/profile
2113 Format: [schedule,]<number>
2114 Param: "schedule" - profile schedule points.
2115 Param: <number> - step/bucket size as a power of 2 for
2116 statistical time based profiling.
2117 Param: "sleep" - profile D-state sleeping (millisecs).
2118 Requires CONFIG_SCHEDSTATS
2119 Param: "kvm" - profile VM exits.
2121 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2122 before loading.
2123 See Documentation/blockdev/ramdisk.txt.
2125 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2126 probe for; one of (bare|imps|exps|lifebook|any).
2127 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2128 per second.
2129 psmouse.resetafter= [HW,MOUSE]
2130 Try to reset the device after so many bad packets
2131 (0 = never).
2132 psmouse.resolution=
2133 [HW,MOUSE] Set desired mouse resolution, in dpi.
2134 psmouse.smartscroll=
2135 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2136 0 = disabled, 1 = enabled (default).
2138 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2139 Format:
2140 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2142 pt. [PARIDE]
2143 See Documentation/blockdev/paride.txt.
2145 pty.legacy_count=
2146 [KNL] Number of legacy pty's. Overwrites compiled-in
2147 default number.
2149 quiet [KNL] Disable most log messages
2151 r128= [HW,DRM]
2153 raid= [HW,RAID]
2154 See Documentation/md.txt.
2156 ramdisk_blocksize= [RAM]
2157 See Documentation/blockdev/ramdisk.txt.
2159 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2160 See Documentation/blockdev/ramdisk.txt.
2162 rcupdate.blimit= [KNL,BOOT]
2163 Set maximum number of finished RCU callbacks to process
2164 in one batch.
2166 rcupdate.qhimark= [KNL,BOOT]
2167 Set threshold of queued
2168 RCU callbacks over which batch limiting is disabled.
2170 rcupdate.qlowmark= [KNL,BOOT]
2171 Set threshold of queued RCU callbacks below which
2172 batch limiting is re-enabled.
2174 rdinit= [KNL]
2175 Format: <full_path>
2176 Run specified binary instead of /init from the ramdisk,
2177 used for early userspace startup. See initrd.
2179 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2180 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2181 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2183 relax_domain_level=
2184 [KNL, SMP] Set scheduler's default relax_domain_level.
2185 See Documentation/cgroups/cpusets.txt.
2187 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2189 reservetop= [X86-32]
2190 Format: nn[KMG]
2191 Reserves a hole at the top of the kernel virtual
2192 address space.
2194 reset_devices [KNL] Force drivers to reset the underlying device
2195 during initialization.
2197 resume= [SWSUSP]
2198 Specify the partition device for software suspend
2200 resume_offset= [SWSUSP]
2201 Specify the offset from the beginning of the partition
2202 given by "resume=" at which the swap header is located,
2203 in <PAGE_SIZE> units (needed only for swap files).
2204 See Documentation/power/swsusp-and-swap-files.txt
2206 retain_initrd [RAM] Keep initrd memory after extraction
2208 rhash_entries= [KNL,NET]
2209 Set number of hash buckets for route cache
2211 riscom8= [HW,SERIAL]
2212 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2214 ro [KNL] Mount root device read-only on boot
2216 root= [KNL] Root filesystem
2218 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2219 mount the root filesystem
2221 rootflags= [KNL] Set root filesystem mount option string
2223 rootfstype= [KNL] Set root filesystem type
2225 rootwait [KNL] Wait (indefinitely) for root device to show up.
2226 Useful for devices that are detected asynchronously
2227 (e.g. USB and MMC devices).
2229 rw [KNL] Mount root device read-write on boot
2231 S [KNL] Run init in single mode
2233 sa1100ir [NET]
2234 See drivers/net/irda/sa1100_ir.c.
2236 sbni= [NET] Granch SBNI12 leased line adapter
2238 sched_debug [KNL] Enables verbose scheduler debug messages.
2240 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2241 Format: <io>[,<timeout>[,<isapnp>]]
2243 scsi_debug_*= [SCSI]
2244 See drivers/scsi/scsi_debug.c.
2246 scsi_default_dev_flags=
2247 [SCSI] SCSI default device flags
2248 Format: <integer>
2250 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2251 Format: <vendor>:<model>:<flags>
2252 (flags are integer value)
2254 scsi_logging_level= [SCSI] a bit mask of logging levels
2255 See drivers/scsi/scsi_logging.h for bits. Also
2256 settable via sysctl at dev.scsi.logging_level
2257 (/proc/sys/dev/scsi/logging_level).
2258 There is also a nice 'scsi_logging_level' script in the
2259 S390-tools package, available for download at
2260 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2262 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2263 discovered. async scans them in kernel threads,
2264 allowing boot to proceed. none ignores them, expecting
2265 user space to do the scan.
2267 security= [SECURITY] Choose a security module to enable at boot.
2268 If this boot parameter is not specified, only the first
2269 security module asking for security registration will be
2270 loaded. An invalid security module name will be treated
2271 as if no module has been chosen.
2273 selinux= [SELINUX] Disable or enable SELinux at boot time.
2274 Format: { "0" | "1" }
2275 See security/selinux/Kconfig help text.
2276 0 -- disable.
2277 1 -- enable.
2278 Default value is set via kernel config option.
2279 If enabled at boot time, /selinux/disable can be used
2280 later to disable prior to initial policy load.
2282 serialnumber [BUGS=X86-32]
2284 shapers= [NET]
2285 Maximal number of shapers.
2287 show_msr= [x86] show boot-time MSR settings
2288 Format: { <integer> }
2289 Show boot-time (BIOS-initialized) MSR settings.
2290 The parameter means the number of CPUs to show,
2291 for example 1 means boot CPU only.
2293 sim710= [SCSI,HW]
2294 See header of drivers/scsi/sim710.c.
2296 simeth= [IA-64]
2297 simscsi=
2299 slram= [HW,MTD]
2301 slub_debug[=options[,slabs]] [MM, SLUB]
2302 Enabling slub_debug allows one to determine the
2303 culprit if slab objects become corrupted. Enabling
2304 slub_debug can create guard zones around objects and
2305 may poison objects when not in use. Also tracks the
2306 last alloc / free. For more information see
2307 Documentation/vm/slub.txt.
2309 slub_max_order= [MM, SLUB]
2310 Determines the maximum allowed order for slabs.
2311 A high setting may cause OOMs due to memory
2312 fragmentation. For more information see
2313 Documentation/vm/slub.txt.
2315 slub_min_objects= [MM, SLUB]
2316 The minimum number of objects per slab. SLUB will
2317 increase the slab order up to slub_max_order to
2318 generate a sufficiently large slab able to contain
2319 the number of objects indicated. The higher the number
2320 of objects the smaller the overhead of tracking slabs
2321 and the less frequently locks need to be acquired.
2322 For more information see Documentation/vm/slub.txt.
2324 slub_min_order= [MM, SLUB]
2325 Determines the mininum page order for slabs. Must be
2326 lower than slub_max_order.
2327 For more information see Documentation/vm/slub.txt.
2329 slub_nomerge [MM, SLUB]
2330 Disable merging of slabs with similar size. May be
2331 necessary if there is some reason to distinguish
2332 allocs to different slabs. Debug options disable
2333 merging on their own.
2334 For more information see Documentation/vm/slub.txt.
2336 smart2= [HW]
2337 Format: <io1>[,<io2>[,...,<io8>]]
2339 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2340 attempt to substitute SMP alternatives once at boot.
2342 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2343 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2344 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2345 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2346 smsc-ircc2.ircc_irq= [HW] IRQ line
2347 smsc-ircc2.ircc_dma= [HW] DMA channel
2348 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2349 0: Toshiba Satellite 1800 (GP data pin select)
2350 1: Fast pin select (default)
2351 2: ATC IRMode
2353 snd-ad1816a= [HW,ALSA]
2355 snd-ad1848= [HW,ALSA]
2357 snd-ali5451= [HW,ALSA]
2359 snd-als100= [HW,ALSA]
2361 snd-als4000= [HW,ALSA]
2363 snd-azt2320= [HW,ALSA]
2365 snd-cmi8330= [HW,ALSA]
2367 snd-cmipci= [HW,ALSA]
2369 snd-cs4231= [HW,ALSA]
2371 snd-cs4232= [HW,ALSA]
2373 snd-cs4236= [HW,ALSA]
2375 snd-cs4281= [HW,ALSA]
2377 snd-cs46xx= [HW,ALSA]
2379 snd-dt019x= [HW,ALSA]
2381 snd-dummy= [HW,ALSA]
2383 snd-emu10k1= [HW,ALSA]
2385 snd-ens1370= [HW,ALSA]
2387 snd-ens1371= [HW,ALSA]
2389 snd-es968= [HW,ALSA]
2391 snd-es1688= [HW,ALSA]
2393 snd-es18xx= [HW,ALSA]
2395 snd-es1938= [HW,ALSA]
2397 snd-es1968= [HW,ALSA]
2399 snd-fm801= [HW,ALSA]
2401 snd-gusclassic= [HW,ALSA]
2403 snd-gusextreme= [HW,ALSA]
2405 snd-gusmax= [HW,ALSA]
2407 snd-hdsp= [HW,ALSA]
2409 snd-ice1712= [HW,ALSA]
2411 snd-intel8x0= [HW,ALSA]
2413 snd-interwave= [HW,ALSA]
2415 snd-interwave-stb=
2416 [HW,ALSA]
2418 snd-korg1212= [HW,ALSA]
2420 snd-maestro3= [HW,ALSA]
2422 snd-mpu401= [HW,ALSA]
2424 snd-mtpav= [HW,ALSA]
2426 snd-nm256= [HW,ALSA]
2428 snd-opl3sa2= [HW,ALSA]
2430 snd-opti92x-ad1848=
2431 [HW,ALSA]
2433 snd-opti92x-cs4231=
2434 [HW,ALSA]
2436 snd-opti93x= [HW,ALSA]
2438 snd-pmac= [HW,ALSA]
2440 snd-rme32= [HW,ALSA]
2442 snd-rme96= [HW,ALSA]
2444 snd-rme9652= [HW,ALSA]
2446 snd-sb8= [HW,ALSA]
2448 snd-sb16= [HW,ALSA]
2450 snd-sbawe= [HW,ALSA]
2452 snd-serial= [HW,ALSA]
2454 snd-sgalaxy= [HW,ALSA]
2456 snd-sonicvibes= [HW,ALSA]
2458 snd-sun-amd7930=
2459 [HW,ALSA]
2461 snd-sun-cs4231= [HW,ALSA]
2463 snd-trident= [HW,ALSA]
2465 snd-usb-audio= [HW,ALSA,USB]
2467 snd-via82xx= [HW,ALSA]
2469 snd-virmidi= [HW,ALSA]
2471 snd-wavefront= [HW,ALSA]
2473 snd-ymfpci= [HW,ALSA]
2475 softlockup_panic=
2476 [KNL] Should the soft-lockup detector generate panics.
2478 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2479 See Documentation/sonypi.txt
2481 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2482 See Documentation/serial/specialix.txt.
2484 spia_io_base= [HW,MTD]
2485 spia_fio_base=
2486 spia_pedr=
2487 spia_peddr=
2489 sscape= [HW,OSS]
2490 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2492 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2493 See Documentation/scsi/st.txt.
2495 stacktrace [FTRACE]
2496 Enabled the stack tracer on boot up.
2498 sti= [PARISC,HW]
2499 Format: <num>
2500 Set the STI (builtin display/keyboard on the HP-PARISC
2501 machines) console (graphic card) which should be used
2502 as the initial boot-console.
2503 See also comment in drivers/video/console/sticore.c.
2505 sti_font= [HW]
2506 See comment in drivers/video/console/sticore.c.
2508 stifb= [HW]
2509 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2511 sunrpc.min_resvport=
2512 sunrpc.max_resvport=
2513 [NFS,SUNRPC]
2514 SunRPC servers often require that client requests
2515 originate from a privileged port (i.e. a port in the
2516 range 0 < portnr < 1024).
2517 An administrator who wishes to reserve some of these
2518 ports for other uses may adjust the range that the
2519 kernel's sunrpc client considers to be privileged
2520 using these two parameters to set the minimum and
2521 maximum port values.
2523 sunrpc.pool_mode=
2524 [NFS]
2525 Control how the NFS server code allocates CPUs to
2526 service thread pools. Depending on how many NICs
2527 you have and where their interrupts are bound, this
2528 option will affect which CPUs will do NFS serving.
2529 Note: this parameter cannot be changed while the
2530 NFS server is running.
2532 auto the server chooses an appropriate mode
2533 automatically using heuristics
2534 global a single global pool contains all CPUs
2535 percpu one pool for each CPU
2536 pernode one pool for each NUMA node (equivalent
2537 to global on non-NUMA machines)
2539 sunrpc.tcp_slot_table_entries=
2540 sunrpc.udp_slot_table_entries=
2541 [NFS,SUNRPC]
2542 Sets the upper limit on the number of simultaneous
2543 RPC calls that can be sent from the client to a
2544 server. Increasing these values may allow you to
2545 improve throughput, but will also increase the
2546 amount of memory reserved for use by the client.
2548 swiotlb= [IA-64] Number of I/O TLB slabs
2550 switches= [HW,M68k]
2552 sym53c416= [HW,SCSI]
2553 See header of drivers/scsi/sym53c416.c.
2555 sysrq_always_enabled
2556 [KNL]
2557 Ignore sysrq setting - this boot parameter will
2558 neutralize any effect of /proc/sys/kernel/sysrq.
2559 Useful for debugging.
2561 t128= [HW,SCSI]
2562 See header of drivers/scsi/t128.c.
2564 tdfx= [HW,DRM]
2566 test_suspend= [SUSPEND]
2567 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2568 standby suspend) as the system sleep state to briefly
2569 enter during system startup. The system is woken from
2570 this state using a wakeup-capable RTC alarm.
2572 thash_entries= [KNL,NET]
2573 Set number of hash buckets for TCP connection
2575 thermal.act= [HW,ACPI]
2576 -1: disable all active trip points in all thermal zones
2577 <degrees C>: override all lowest active trip points
2579 thermal.crt= [HW,ACPI]
2580 -1: disable all critical trip points in all thermal zones
2581 <degrees C>: override all critical trip points
2583 thermal.nocrt= [HW,ACPI]
2584 Set to disable actions on ACPI thermal zone
2585 critical and hot trip points.
2587 thermal.off= [HW,ACPI]
2588 1: disable ACPI thermal control
2590 thermal.psv= [HW,ACPI]
2591 -1: disable all passive trip points
2592 <degrees C>: override all passive trip points to this
2593 value
2595 thermal.tzp= [HW,ACPI]
2596 Specify global default ACPI thermal zone polling rate
2597 <deci-seconds>: poll all this frequency
2598 0: no polling (default)
2600 tmscsim= [HW,SCSI]
2601 See comment before function dc390_setup() in
2602 drivers/scsi/tmscsim.c.
2604 topology= [S390]
2605 Format: {off | on}
2606 Specify if the kernel should make use of the cpu
2607 topology informations if the hardware supports these.
2608 The scheduler will make use of these informations and
2609 e.g. base its process migration decisions on it.
2610 Default is off.
2612 tp720= [HW,PS2]
2614 tpm_suspend_pcr=[HW,TPM]
2615 Format: integer pcr id
2616 Specify that at suspend time, the tpm driver
2617 should extend the specified pcr with zeros,
2618 as a workaround for some chips which fail to
2619 flush the last written pcr on TPM_SaveState.
2620 This will guarantee that all the other pcrs
2621 are saved.
2623 trace_buf_size=nn[KMG]
2624 [FTRACE] will set tracing buffer size.
2626 trace_event=[event-list]
2627 [FTRACE] Set and start specified trace events in order
2628 to facilitate early boot debugging.
2629 See also Documentation/trace/events.txt
2631 trix= [HW,OSS] MediaTrix AudioTrix Pro
2632 Format:
2633 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2635 tsc= Disable clocksource-must-verify flag for TSC.
2636 Format: <string>
2637 [x86] reliable: mark tsc clocksource as reliable, this
2638 disables clocksource verification at runtime.
2639 Used to enable high-resolution timer mode on older
2640 hardware, and in virtualized environment.
2642 turbografx.map[2|3]= [HW,JOY]
2643 TurboGraFX parallel port interface
2644 Format:
2645 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2646 See also Documentation/input/joystick-parport.txt
2648 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2649 See header of drivers/scsi/u14-34f.c.
2651 uart401= [HW,OSS]
2652 Format: <io>,<irq>
2654 uart6850= [HW,OSS]
2655 Format: <io>,<irq>
2657 uhash_entries= [KNL,NET]
2658 Set number of hash buckets for UDP/UDP-Lite connections
2660 uhci-hcd.ignore_oc=
2661 [USB] Ignore overcurrent events (default N).
2662 Some badly-designed motherboards generate lots of
2663 bogus events, for ports that aren't wired to
2664 anything. Set this parameter to avoid log spamming.
2665 Note that genuine overcurrent events won't be
2666 reported either.
2668 unknown_nmi_panic
2669 [X86]
2670 Set unknown_nmi_panic=1 early on boot.
2672 usbcore.autosuspend=
2673 [USB] The autosuspend time delay (in seconds) used
2674 for newly-detected USB devices (default 2). This
2675 is the time required before an idle device will be
2676 autosuspended. Devices for which the delay is set
2677 to a negative value won't be autosuspended at all.
2679 usbcore.usbfs_snoop=
2680 [USB] Set to log all usbfs traffic (default 0 = off).
2682 usbcore.blinkenlights=
2683 [USB] Set to cycle leds on hubs (default 0 = off).
2685 usbcore.old_scheme_first=
2686 [USB] Start with the old device initialization
2687 scheme (default 0 = off).
2689 usbcore.use_both_schemes=
2690 [USB] Try the other device initialization scheme
2691 if the first one fails (default 1 = enabled).
2693 usbcore.initial_descriptor_timeout=
2694 [USB] Specifies timeout for the initial 64-byte
2695 USB_REQ_GET_DESCRIPTOR request in milliseconds
2696 (default 5000 = 5.0 seconds).
2698 usbhid.mousepoll=
2699 [USBHID] The interval which mice are to be polled at.
2701 usb-storage.delay_use=
2702 [UMS] The delay in seconds before a new device is
2703 scanned for Logical Units (default 5).
2705 usb-storage.quirks=
2706 [UMS] A list of quirks entries to supplement or
2707 override the built-in unusual_devs list. List
2708 entries are separated by commas. Each entry has
2709 the form VID:PID:Flags where VID and PID are Vendor
2710 and Product ID values (4-digit hex numbers) and
2711 Flags is a set of characters, each corresponding
2712 to a common usb-storage quirk flag as follows:
2713 a = SANE_SENSE (collect more than 18 bytes
2714 of sense data);
2715 b = BAD_SENSE (don't collect more than 18
2716 bytes of sense data);
2717 c = FIX_CAPACITY (decrease the reported
2718 device capacity by one sector);
2719 h = CAPACITY_HEURISTICS (decrease the
2720 reported device capacity by one
2721 sector if the number is odd);
2722 i = IGNORE_DEVICE (don't bind to this
2723 device);
2724 l = NOT_LOCKABLE (don't try to lock and
2725 unlock ejectable media);
2726 m = MAX_SECTORS_64 (don't transfer more
2727 than 64 sectors = 32 KB at a time);
2728 o = CAPACITY_OK (accept the capacity
2729 reported by the device);
2730 r = IGNORE_RESIDUE (the device reports
2731 bogus residue values);
2732 s = SINGLE_LUN (the device has only one
2733 Logical Unit);
2734 w = NO_WP_DETECT (don't test whether the
2735 medium is write-protected).
2736 Example: quirks=0419:aaf5:rl,0421:0433:rc
2738 userpte=
2739 [X86] Flags controlling user PTE allocations.
2741 nohigh = do not allocate PTE pages in
2742 HIGHMEM regardless of setting
2743 of CONFIG_HIGHPTE.
2745 vdso= [X86,SH]
2746 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2747 vdso=1: enable VDSO (default)
2748 vdso=0: disable VDSO mapping
2750 vdso32= [X86]
2751 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2752 vdso32=1: enable 32-bit VDSO (default)
2753 vdso32=0: disable 32-bit VDSO mapping
2755 vector= [IA-64,SMP]
2756 vector=percpu: enable percpu vector domain
2758 video= [FB] Frame buffer configuration
2759 See Documentation/fb/modedb.txt.
2761 vga= [BOOT,X86-32] Select a particular video mode
2762 See Documentation/x86/boot.txt and
2763 Documentation/svga.txt.
2764 Use vga=ask for menu.
2765 This is actually a boot loader parameter; the value is
2766 passed to the kernel using a special protocol.
2768 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2769 size of <nn>. This can be used to increase the
2770 minimum size (128MB on x86). It can also be used to
2771 decrease the size and leave more room for directly
2772 mapped kernel RAM.
2774 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2775 Format: <command>
2777 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2778 Format: <command>
2780 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2781 Format: <command>
2783 vt.cur_default= [VT] Default cursor shape.
2784 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2785 the parameters of the <Esc>[?A;B;Cc escape sequence;
2786 see VGA-softcursor.txt. Default: 2 = underline.
2788 vt.default_blu= [VT]
2789 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2790 Change the default blue palette of the console.
2791 This is a 16-member array composed of values
2792 ranging from 0-255.
2794 vt.default_grn= [VT]
2795 Format: <green0>,<green1>,<green2>,...,<green15>
2796 Change the default green palette of the console.
2797 This is a 16-member array composed of values
2798 ranging from 0-255.
2800 vt.default_red= [VT]
2801 Format: <red0>,<red1>,<red2>,...,<red15>
2802 Change the default red palette of the console.
2803 This is a 16-member array composed of values
2804 ranging from 0-255.
2806 vt.default_utf8=
2807 [VT]
2808 Format=<0|1>
2809 Set system-wide default UTF-8 mode for all tty's.
2810 Default is 1, i.e. UTF-8 mode is enabled for all
2811 newly opened terminals.
2813 vt.global_cursor_default=
2814 [VT]
2815 Format=<-1|0|1>
2816 Set system-wide default for whether a cursor
2817 is shown on new VTs. Default is -1,
2818 i.e. cursors will be created by default unless
2819 overridden by individual drivers. 0 will hide
2820 cursors, 1 will display them.
2822 waveartist= [HW,OSS]
2823 Format: <io>,<irq>,<dma>,<dma2>
2825 wd33c93= [HW,SCSI]
2826 See header of drivers/scsi/wd33c93.c.
2828 wd7000= [HW,SCSI]
2829 See header of drivers/scsi/wd7000.c.
2831 wdt= [WDT] Watchdog
2832 See Documentation/watchdog/wdt.txt.
2834 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2835 default x2apic cluster mode on platforms
2836 supporting x2apic.
2838 x86_mrst_timer= [X86-32,APBT]
2839 Choose timer option for x86 Moorestown MID platform.
2840 Two valid options are apbt timer only and lapic timer
2841 plus one apbt timer for broadcast timer.
2842 x86_mrst_timer=apbt_only | lapic_and_apbt
2844 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2845 xd_geo= See header of drivers/block/xd.c.
2847 xirc2ps_cs= [NET,PCMCIA]
2848 Format:
2849 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2851 ______________________________________________________________________
2853 TODO:
2855 Add documentation for ALSA options.
2856 Add more DRM drivers.