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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 KGDB Kernel debugger support is enabled.
62 KVM Kernel Virtual Machine support is enabled.
63 LIBATA Libata driver is enabled
64 LP Printer support is enabled.
65 LOOP Loopback device support is enabled.
66 M68k M68k architecture is enabled.
67 These options have more detailed description inside of
68 Documentation/m68k/kernel-options.txt.
69 MCA MCA bus support is enabled.
70 MDA MDA console support is enabled.
71 MOUSE Appropriate mouse support is enabled.
72 MSI Message Signaled Interrupts (PCI).
73 MTD MTD (Memory Technology Device) support is enabled.
74 NET Appropriate network support is enabled.
75 NUMA NUMA support 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 APPARMOR AppArmor support is enabled.
96 SERIAL Serial support is enabled.
97 SH SuperH architecture is enabled.
98 SMP The kernel is an SMP kernel.
99 SPARC Sparc architecture is enabled.
100 SWSUSP Software suspend (hibernation) is enabled.
101 SUSPEND System suspend states are enabled.
102 FTRACE Function tracing enabled.
103 TPM TPM drivers are enabled.
104 TS Appropriate touchscreen support is enabled.
105 UMS USB Mass Storage support is enabled.
106 USB USB support is enabled.
107 USBHID USB Human Interface Device support is enabled.
108 V4L Video For Linux support is enabled.
109 VGA The VGA console has been enabled.
110 VT Virtual terminal support is enabled.
111 WDT Watchdog support is enabled.
112 XT IBM PC/XT MFM hard disk support is enabled.
113 X86-32 X86-32, aka i386 architecture is enabled.
114 X86-64 X86-64 architecture is enabled.
115 More X86-64 boot options can be found in
116 Documentation/x86/x86_64/boot-options.txt .
117 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
118 XEN Xen support is enabled
120 In addition, the following text indicates that the option:
122 BUGS= Relates to possible processor bugs on the said processor.
123 KNL Is a kernel start-up parameter.
124 BOOT Is a boot loader parameter.
126 Parameters denoted with BOOT are actually interpreted by the boot
127 loader, and have no meaning to the kernel directly.
128 Do not modify the syntax of boot loader parameters without extreme
129 need or coordination with <Documentation/x86/boot.txt>.
131 There are also arch-specific kernel-parameters not documented here.
132 See for example <Documentation/x86/x86_64/boot-options.txt>.
134 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
135 a trailing = on the name of any parameter states that that parameter will
136 be entered as an environment variable, whereas its absence indicates that
137 it will appear as a kernel argument readable via /proc/cmdline by programs
138 running once the system is up.
140 The number of kernel parameters is not limited, but the length of the
141 complete command line (parameters including spaces etc.) is limited to
142 a fixed number of characters. This limit depends on the architecture
143 and is between 256 and 4096 characters. It is defined in the file
144 ./include/asm/setup.h as COMMAND_LINE_SIZE.
147 acpi= [HW,ACPI,X86]
148 Advanced Configuration and Power Interface
149 Format: { force | off | strict | noirq | rsdt }
150 force -- enable ACPI if default was off
151 off -- disable ACPI if default was on
152 noirq -- do not use ACPI for IRQ routing
153 strict -- Be less tolerant of platforms that are not
154 strictly ACPI specification compliant.
155 rsdt -- prefer RSDT over (default) XSDT
156 copy_dsdt -- copy DSDT to memory
158 See also Documentation/power/pm.txt, pci=noacpi
160 acpi_apic_instance= [ACPI, IOAPIC]
161 Format: <int>
162 2: use 2nd APIC table, if available
163 1,0: use 1st APIC table
164 default: 0
166 acpi_backlight= [HW,ACPI]
167 acpi_backlight=vendor
168 acpi_backlight=video
169 If set to vendor, prefer vendor specific driver
170 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
171 of the ACPI video.ko driver.
173 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
174 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
175 Format: <int>
176 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
177 debug output. Bits in debug_layer correspond to a
178 _COMPONENT in an ACPI source file, e.g.,
179 #define _COMPONENT ACPI_PCI_COMPONENT
180 Bits in debug_level correspond to a level in
181 ACPI_DEBUG_PRINT statements, e.g.,
182 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
183 The debug_level mask defaults to "info". See
184 Documentation/acpi/debug.txt for more information about
185 debug layers and levels.
187 Enable processor driver info messages:
188 acpi.debug_layer=0x20000000
189 Enable PCI/PCI interrupt routing info messages:
190 acpi.debug_layer=0x400000
191 Enable AML "Debug" output, i.e., stores to the Debug
192 object while interpreting AML:
193 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
194 Enable all messages related to ACPI hardware:
195 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
197 Some values produce so much output that the system is
198 unusable. The "log_buf_len" parameter may be useful
199 if you need to capture more output.
201 acpi_display_output= [HW,ACPI]
202 acpi_display_output=vendor
203 acpi_display_output=video
204 See above.
206 acpi_irq_balance [HW,ACPI]
207 ACPI will balance active IRQs
208 default in APIC mode
210 acpi_irq_nobalance [HW,ACPI]
211 ACPI will not move active IRQs (default)
212 default in PIC mode
214 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
215 Format: <irq>,<irq>...
217 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
218 use by PCI
219 Format: <irq>,<irq>...
221 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
223 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
224 Format: To spoof as Windows 98: ="Microsoft Windows"
226 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
227 acpi_osi="string1" # add string1 -- only one string
228 acpi_osi="!string2" # remove built-in string2
229 acpi_osi= # disable all strings
231 acpi_pm_good [X86]
232 Override the pmtimer bug detection: force the kernel
233 to assume that this machine's pmtimer latches its value
234 and always returns good values.
236 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
237 Format: { level | edge | high | low }
239 acpi_serialize [HW,ACPI] force serialization of AML methods
241 acpi_skip_timer_override [HW,ACPI]
242 Recognize and ignore IRQ0/pin2 Interrupt Override.
243 For broken nForce2 BIOS resulting in XT-PIC timer.
245 acpi_sleep= [HW,ACPI] Sleep options
246 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
247 old_ordering, s4_nonvs, sci_force_enable }
248 See Documentation/power/video.txt for information on
249 s3_bios and s3_mode.
250 s3_beep is for debugging; it makes the PC's speaker beep
251 as soon as the kernel's real-mode entry point is called.
252 s4_nohwsig prevents ACPI hardware signature from being
253 used during resume from hibernation.
254 old_ordering causes the ACPI 1.0 ordering of the _PTS
255 control method, with respect to putting devices into
256 low power states, to be enforced (the ACPI 2.0 ordering
257 of _PTS is used by default).
258 nonvs prevents the kernel from saving/restoring the
259 ACPI NVS memory during suspend/hibernation and resume.
260 sci_force_enable causes the kernel to set SCI_EN directly
261 on resume from S1/S3 (which is against the ACPI spec,
262 but some broken systems don't work without it).
264 acpi_use_timer_override [HW,ACPI]
265 Use timer override. For some broken Nvidia NF5 boards
266 that require a timer override, but don't have HPET
268 acpi_enforce_resources= [ACPI]
269 { strict | lax | no }
270 Check for resource conflicts between native drivers
271 and ACPI OperationRegions (SystemIO and SystemMemory
272 only). IO ports and memory declared in ACPI might be
273 used by the ACPI subsystem in arbitrary AML code and
274 can interfere with legacy drivers.
275 strict (default): access to resources claimed by ACPI
276 is denied; legacy drivers trying to access reserved
277 resources will fail to bind to device using them.
278 lax: access to resources claimed by ACPI is allowed;
279 legacy drivers trying to access reserved resources
280 will bind successfully but a warning message is logged.
281 no: ACPI OperationRegions are not marked as reserved,
282 no further checks are performed.
284 add_efi_memmap [EFI; X86] Include EFI memory map in
285 kernel's map of available physical RAM.
287 advansys= [HW,SCSI]
288 See header of drivers/scsi/advansys.c.
290 agp= [AGP]
291 { off | try_unsupported }
292 off: disable AGP support
293 try_unsupported: try to drive unsupported chipsets
294 (may crash computer or cause data corruption)
296 aha152x= [HW,SCSI]
297 See Documentation/scsi/aha152x.txt.
299 aha1542= [HW,SCSI]
300 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
302 aic7xxx= [HW,SCSI]
303 See Documentation/scsi/aic7xxx.txt.
305 aic79xx= [HW,SCSI]
306 See Documentation/scsi/aic79xx.txt.
308 ALSA [HW,ALSA]
309 See Documentation/sound/alsa/alsa-parameters.txt
311 alignment= [KNL,ARM]
312 Allow the default userspace alignment fault handler
313 behaviour to be specified. Bit 0 enables warnings,
314 bit 1 enables fixups, and bit 2 sends a segfault.
316 amd_iommu= [HW,X86-84]
317 Pass parameters to the AMD IOMMU driver in the system.
318 Possible values are:
319 fullflush - enable flushing of IO/TLB entries when
320 they are unmapped. Otherwise they are
321 flushed before they will be reused, which
322 is a lot of faster
323 off - do not initialize any AMD IOMMU found in
324 the system
326 amijoy.map= [HW,JOY] Amiga joystick support
327 Map of devices attached to JOY0DAT and JOY1DAT
328 Format: <a>,<b>
329 See also Documentation/kernel/input/joystick.txt
331 analog.map= [HW,JOY] Analog joystick and gamepad support
332 Specifies type or capabilities of an analog joystick
333 connected to one of 16 gameports
334 Format: <type1>,<type2>,..<type16>
336 apc= [HW,SPARC]
337 Power management functions (SPARCstation-4/5 + deriv.)
338 Format: noidle
339 Disable APC CPU standby support. SPARCstation-Fox does
340 not play well with APC CPU idle - disable it if you have
341 APC and your system crashes randomly.
343 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
344 Change the output verbosity whilst booting
345 Format: { quiet (default) | verbose | debug }
346 Change the amount of debugging information output
347 when initialising the APIC and IO-APIC components.
349 autoconf= [IPV6]
350 See Documentation/networking/ipv6.txt.
352 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
353 Limit apic dumping. The parameter defines the maximal
354 number of local apics being dumped. Also it is possible
355 to set it to "all" by meaning -- no limit here.
356 Format: { 1 (default) | 2 | ... | all }.
357 The parameter valid if only apic=debug or
358 apic=verbose is specified.
359 Example: apic=debug show_lapic=all
361 apm= [APM] Advanced Power Management
362 See header of arch/x86/kernel/apm_32.c.
364 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
365 Format: <io>,<irq>,<nodeID>
367 ataflop= [HW,M68k]
369 atarimouse= [HW,MOUSE] Atari Mouse
371 atascsi= [HW,SCSI] Atari SCSI
373 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
374 EzKey and similar keyboards
376 atkbd.reset= [HW] Reset keyboard during initialization
378 atkbd.set= [HW] Select keyboard code set
379 Format: <int> (2 = AT (default), 3 = PS/2)
381 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
382 keyboards
384 atkbd.softraw= [HW] Choose between synthetic and real raw mode
385 Format: <bool> (0 = real, 1 = synthetic (default))
387 atkbd.softrepeat= [HW]
388 Use software keyboard repeat
390 autotest [IA64]
392 baycom_epp= [HW,AX25]
393 Format: <io>,<mode>
395 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
396 Format: <io>,<mode>
397 See header of drivers/net/hamradio/baycom_par.c.
399 baycom_ser_fdx= [HW,AX25]
400 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
401 Format: <io>,<irq>,<mode>[,<baud>]
402 See header of drivers/net/hamradio/baycom_ser_fdx.c.
404 baycom_ser_hdx= [HW,AX25]
405 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
406 Format: <io>,<irq>,<mode>
407 See header of drivers/net/hamradio/baycom_ser_hdx.c.
409 boot_delay= Milliseconds to delay each printk during boot.
410 Values larger than 10 seconds (10000) are changed to
411 no delay (0).
412 Format: integer
414 bootmem_debug [KNL] Enable bootmem allocator debug messages.
416 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
417 bttv.radio= Most important insmod options are available as
418 kernel args too.
419 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
420 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
422 BusLogic= [HW,SCSI]
423 See drivers/scsi/BusLogic.c, comment before function
424 BusLogic_ParseDriverOptions().
426 c101= [NET] Moxa C101 synchronous serial card
428 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
429 Sometimes CPU hardware bugs make them report the cache
430 size incorrectly. The kernel will attempt work arounds
431 to fix known problems, but for some CPUs it is not
432 possible to determine what the correct size should be.
433 This option provides an override for these situations.
435 capability.disable=
436 [SECURITY] Disable capabilities. This would normally
437 be used only if an alternative security model is to be
438 configured. Potentially dangerous and should only be
439 used if you are entirely sure of the consequences.
441 ccw_timeout_log [S390]
442 See Documentation/s390/CommonIO for details.
444 cgroup_disable= [KNL] Disable a particular controller
445 Format: {name of the controller(s) to disable}
446 {Currently supported controllers - "memory"}
448 checkreqprot [SELINUX] Set initial checkreqprot flag value.
449 Format: { "0" | "1" }
450 See security/selinux/Kconfig help text.
451 0 -- check protection applied by kernel (includes
452 any implied execute protection).
453 1 -- check protection requested by application.
454 Default value is set via a kernel config option.
455 Value can be changed at runtime via
456 /selinux/checkreqprot.
458 cio_ignore= [S390]
459 See Documentation/s390/CommonIO for details.
461 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
462 [Deprecated]
463 Forces specified clocksource (if available) to be used
464 when calculating gettimeofday(). If specified
465 clocksource is not available, it defaults to PIT.
466 Format: { pit | tsc | cyclone | pmtmr }
468 clocksource= Override the default clocksource
469 Format: <string>
470 Override the default clocksource and use the clocksource
471 with the name specified.
472 Some clocksource names to choose from, depending on
473 the platform:
474 [all] jiffies (this is the base, fallback clocksource)
475 [ACPI] acpi_pm
476 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
477 pxa_timer,timer3,32k_counter,timer0_1
478 [AVR32] avr32
479 [X86-32] pit,hpet,tsc,vmi-timer;
480 scx200_hrt on Geode; cyclone on IBM x440
481 [MIPS] MIPS
482 [PARISC] cr16
483 [S390] tod
484 [SH] SuperH
485 [SPARC64] tick
486 [X86-64] hpet,tsc
488 clearcpuid=BITNUM [X86]
489 Disable CPUID feature X for the kernel. See
490 arch/x86/include/asm/cpufeature.h for the valid bit
491 numbers. Note the Linux specific bits are not necessarily
492 stable over kernel options, but the vendor specific
493 ones should be.
494 Also note that user programs calling CPUID directly
495 or using the feature without checking anything
496 will still see it. This just prevents it from
497 being used by the kernel or shown in /proc/cpuinfo.
498 Also note the kernel might malfunction if you disable
499 some critical bits.
501 cmo_free_hint= [PPC] Format: { yes | no }
502 Specify whether pages are marked as being inactive
503 when they are freed. This is used in CMO environments
504 to determine OS memory pressure for page stealing by
505 a hypervisor.
506 Default: yes
508 code_bytes [X86] How many bytes of object code to print
509 in an oops report.
510 Range: 0 - 8192
511 Default: 64
513 com20020= [HW,NET] ARCnet - COM20020 chipset
514 Format:
515 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
517 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
518 Format: <io>[,<irq>]
520 com90xx= [HW,NET]
521 ARCnet - COM90xx chipset (memory-mapped buffers)
522 Format: <io>[,<irq>[,<memstart>]]
524 condev= [HW,S390] console device
525 conmode=
527 console= [KNL] Output console device and options.
529 tty<n> Use the virtual console device <n>.
531 ttyS<n>[,options]
532 ttyUSB0[,options]
533 Use the specified serial port. The options are of
534 the form "bbbbpnf", where "bbbb" is the baud rate,
535 "p" is parity ("n", "o", or "e"), "n" is number of
536 bits, and "f" is flow control ("r" for RTS or
537 omit it). Default is "9600n8".
539 See Documentation/serial-console.txt for more
540 information. See
541 Documentation/networking/netconsole.txt for an
542 alternative.
544 uart[8250],io,<addr>[,options]
545 uart[8250],mmio,<addr>[,options]
546 Start an early, polled-mode console on the 8250/16550
547 UART at the specified I/O port or MMIO address,
548 switching to the matching ttyS device later. The
549 options are the same as for ttyS, above.
551 If the device connected to the port is not a TTY but a braille
552 device, prepend "brl," before the device type, for instance
553 console=brl,ttyS0
554 For now, only VisioBraille is supported.
556 consoleblank= [KNL] The console blank (screen saver) timeout in
557 seconds. Defaults to 10*60 = 10mins. A value of 0
558 disables the blank timer.
560 coredump_filter=
561 [KNL] Change the default value for
562 /proc/<pid>/coredump_filter.
563 See also Documentation/filesystems/proc.txt.
565 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
566 Format:
567 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
569 crashkernel=nn[KMG]@ss[KMG]
570 [KNL] Reserve a chunk of physical memory to
571 hold a kernel to switch to with kexec on panic.
573 crashkernel=range1:size1[,range2:size2,...][@offset]
574 [KNL] Same as above, but depends on the memory
575 in the running system. The syntax of range is
576 start-[end] where start and end are both
577 a memory unit (amount[KMG]). See also
578 Documentation/kdump/kdump.txt for a example.
580 cs89x0_dma= [HW,NET]
581 Format: <dma>
583 cs89x0_media= [HW,NET]
584 Format: { rj45 | aui | bnc }
586 dasd= [HW,NET]
587 See header of drivers/s390/block/dasd_devmap.c.
589 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
590 (one device per port)
591 Format: <port#>,<type>
592 See also Documentation/input/joystick-parport.txt
594 debug [KNL] Enable kernel debugging (events log level).
596 debug_locks_verbose=
597 [KNL] verbose self-tests
598 Format=<0|1>
599 Print debugging info while doing the locking API
600 self-tests.
601 We default to 0 (no extra messages), setting it to
602 1 will print _a lot_ more information - normally
603 only useful to kernel developers.
605 debug_objects [KNL] Enable object debugging
607 no_debug_objects
608 [KNL] Disable object debugging
610 debugpat [X86] Enable PAT debugging
612 decnet.addr= [HW,NET]
613 Format: <area>[,<node>]
614 See also Documentation/networking/decnet.txt.
616 default_hugepagesz=
617 [same as hugepagesz=] The size of the default
618 HugeTLB page size. This is the size represented by
619 the legacy /proc/ hugepages APIs, used for SHM, and
620 default size when mounting hugetlbfs filesystems.
621 Defaults to the default architecture's huge page size
622 if not specified.
624 dhash_entries= [KNL]
625 Set number of hash buckets for dentry cache.
627 digi= [HW,SERIAL]
628 IO parameters + enable/disable command.
630 digiepca= [HW,SERIAL]
631 See drivers/char/README.epca and
632 Documentation/serial/digiepca.txt.
634 disable= [IPV6]
635 See Documentation/networking/ipv6.txt.
637 disable_ipv6= [IPV6]
638 See Documentation/networking/ipv6.txt.
640 disable_mtrr_cleanup [X86]
641 The kernel tries to adjust MTRR layout from continuous
642 to discrete, to make X server driver able to add WB
643 entry later. This parameter disables that.
645 disable_mtrr_trim [X86, Intel and AMD only]
646 By default the kernel will trim any uncacheable
647 memory out of your available memory pool based on
648 MTRR settings. This parameter disables that behavior,
649 possibly causing your machine to run very slowly.
651 disable_timer_pin_1 [X86]
652 Disable PIN 1 of APIC timer
653 Can be useful to work around chipset bugs.
655 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
656 this option disables the debugging code at boot.
658 dma_debug_entries=<number>
659 This option allows to tune the number of preallocated
660 entries for DMA-API debugging code. One entry is
661 required per DMA-API allocation. Use this if the
662 DMA-API debugging code disables itself because the
663 architectural default is too low.
665 dma_debug_driver=<driver_name>
666 With this option the DMA-API debugging driver
667 filter feature can be enabled at boot time. Just
668 pass the driver to filter for as the parameter.
669 The filter can be disabled or changed to another
670 driver later using sysfs.
672 dscc4.setup= [NET]
674 dtc3181e= [HW,SCSI]
676 dynamic_printk Enables pr_debug()/dev_dbg() calls if
677 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
678 These can also be switched on/off via
679 <debugfs>/dynamic_printk/modules
681 earlycon= [KNL] Output early console device and options.
682 uart[8250],io,<addr>[,options]
683 uart[8250],mmio,<addr>[,options]
684 Start an early, polled-mode console on the 8250/16550
685 UART at the specified I/O port or MMIO address.
686 The options are the same as for ttyS, above.
688 earlyprintk= [X86,SH,BLACKFIN]
689 earlyprintk=vga
690 earlyprintk=serial[,ttySn[,baudrate]]
691 earlyprintk=ttySn[,baudrate]
692 earlyprintk=dbgp[debugController#]
694 Append ",keep" to not disable it when the real console
695 takes over.
697 Only vga or serial or usb debug port at a time.
699 Currently only ttyS0 and ttyS1 are supported.
701 Interaction with the standard serial driver is not
702 very good.
704 The VGA output is eventually overwritten by the real
705 console.
707 ekgdboc= [X86,KGDB] Allow early kernel console debugging
708 ekgdboc=kbd
710 This is desgined to be used in conjunction with
711 the boot argument: earlyprintk=vga
713 eata= [HW,SCSI]
715 edd= [EDD]
716 Format: {"off" | "on" | "skip[mbr]"}
718 eisa_irq_edge= [PARISC,HW]
719 See header of drivers/parisc/eisa.c.
721 elanfreq= [X86-32]
722 See comment before function elanfreq_setup() in
723 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
725 elevator= [IOSCHED]
726 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
727 See Documentation/block/as-iosched.txt and
728 Documentation/block/deadline-iosched.txt for details.
730 elfcorehdr= [IA64,PPC,SH,X86]
731 Specifies physical address of start of kernel core
732 image elf header. Generally kexec loader will
733 pass this option to capture kernel.
734 See Documentation/kdump/kdump.txt for details.
736 enable_mtrr_cleanup [X86]
737 The kernel tries to adjust MTRR layout from continuous
738 to discrete, to make X server driver able to add WB
739 entry later. This parameter enables that.
741 enable_timer_pin_1 [X86]
742 Enable PIN 1 of APIC timer
743 Can be useful to work around chipset bugs
744 (in particular on some ATI chipsets).
745 The kernel tries to set a reasonable default.
747 enforcing [SELINUX] Set initial enforcing status.
748 Format: {"0" | "1"}
749 See security/selinux/Kconfig help text.
750 0 -- permissive (log only, no denials).
751 1 -- enforcing (deny and log).
752 Default value is 0.
753 Value can be changed at runtime via /selinux/enforce.
755 erst_disable [ACPI]
756 Disable Error Record Serialization Table (ERST)
757 support.
759 ether= [HW,NET] Ethernet cards parameters
760 This option is obsoleted by the "netdev=" option, which
761 has equivalent usage. See its documentation for details.
763 failslab=
764 fail_page_alloc=
765 fail_make_request=[KNL]
766 General fault injection mechanism.
767 Format: <interval>,<probability>,<space>,<times>
768 See also /Documentation/fault-injection/.
770 fd_mcs= [HW,SCSI]
771 See header of drivers/scsi/fd_mcs.c.
773 fdomain= [HW,SCSI]
774 See header of drivers/scsi/fdomain.c.
776 floppy= [HW]
777 See Documentation/blockdev/floppy.txt.
779 force_pal_cache_flush
780 [IA-64] Avoid check_sal_cache_flush which may hang on
781 buggy SAL_CACHE_FLUSH implementations. Using this
782 parameter will force ia64_sal_cache_flush to call
783 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
785 ftrace=[tracer]
786 [FTRACE] will set and start the specified tracer
787 as early as possible in order to facilitate early
788 boot debugging.
790 ftrace_dump_on_oops[=orig_cpu]
791 [FTRACE] will dump the trace buffers on oops.
792 If no parameter is passed, ftrace will dump
793 buffers of all CPUs, but if you pass orig_cpu, it will
794 dump only the buffer of the CPU that triggered the
795 oops.
797 ftrace_filter=[function-list]
798 [FTRACE] Limit the functions traced by the function
799 tracer at boot up. function-list is a comma separated
800 list of functions. This list can be changed at run
801 time by the set_ftrace_filter file in the debugfs
802 tracing directory.
804 ftrace_notrace=[function-list]
805 [FTRACE] Do not trace the functions specified in
806 function-list. This list can be changed at run time
807 by the set_ftrace_notrace file in the debugfs
808 tracing directory.
810 ftrace_graph_filter=[function-list]
811 [FTRACE] Limit the top level callers functions traced
812 by the function graph tracer at boot up.
813 function-list is a comma separated list of functions
814 that can be changed at run time by the
815 set_graph_function file in the debugfs tracing directory.
817 gamecon.map[2|3]=
818 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
819 support via parallel port (up to 5 devices per port)
820 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
821 See also Documentation/input/joystick-parport.txt
823 gamma= [HW,DRM]
825 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
826 Format: off | on
827 default: on
829 gcov_persist= [GCOV] When non-zero (default), profiling data for
830 kernel modules is saved and remains accessible via
831 debugfs, even when the module is unloaded/reloaded.
832 When zero, profiling data is discarded and associated
833 debugfs files are removed at module unload time.
835 gdth= [HW,SCSI]
836 See header of drivers/scsi/gdth.c.
838 gpt [EFI] Forces disk with valid GPT signature but
839 invalid Protective MBR to be treated as GPT.
841 gvp11= [HW,SCSI]
843 hashdist= [KNL,NUMA] Large hashes allocated during boot
844 are distributed across NUMA nodes. Defaults on
845 for 64bit NUMA, off otherwise.
846 Format: 0 | 1 (for off | on)
848 hcl= [IA-64] SGI's Hardware Graph compatibility layer
850 hd= [EIDE] (E)IDE hard drive subsystem geometry
851 Format: <cyl>,<head>,<sect>
853 hest_disable [ACPI]
854 Disable Hardware Error Source Table (HEST) support;
855 corresponding firmware-first mode error processing
856 logic will be disabled.
858 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
859 size of <nn>. This works even on boxes that have no
860 highmem otherwise. This also works to reduce highmem
861 size on bigger boxes.
863 highres= [KNL] Enable/disable high resolution timer mode.
864 Valid parameters: "on", "off"
865 Default: "on"
867 hisax= [HW,ISDN]
868 See Documentation/isdn/README.HiSax.
870 hlt [BUGS=ARM,SH]
872 hpet= [X86-32,HPET] option to control HPET usage
873 Format: { enable (default) | disable | force |
874 verbose }
875 disable: disable HPET and use PIT instead
876 force: allow force enabled of undocumented chips (ICH4,
877 VIA, nVidia)
878 verbose: show contents of HPET registers during setup
880 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
881 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
882 On x86-64 and powerpc, this option can be specified
883 multiple times interleaved with hugepages= to reserve
884 huge pages of different sizes. Valid pages sizes on
885 x86-64 are 2M (when the CPU supports "pse") and 1G
886 (when the CPU supports the "pdpe1gb" cpuinfo flag)
887 Note that 1GB pages can only be allocated at boot time
888 using hugepages= and not freed afterwards.
890 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
891 terminal devices. Valid values: 0..8
892 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
893 If specified, z/VM IUCV HVC accepts connections
894 from listed z/VM user IDs only.
896 i2c_bus= [HW] Override the default board specific I2C bus speed
897 or register an additional I2C bus that is not
898 registered from board initialization code.
899 Format:
900 <bus_id>,<clkrate>
902 i8042.debug [HW] Toggle i8042 debug mode
903 i8042.direct [HW] Put keyboard port into non-translated mode
904 i8042.dumbkbd [HW] Pretend that controller can only read data from
905 keyboard and cannot control its state
906 (Don't attempt to blink the leds)
907 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
908 i8042.nokbd [HW] Don't check/create keyboard port
909 i8042.noloop [HW] Disable the AUX Loopback command while probing
910 for the AUX port
911 i8042.nomux [HW] Don't check presence of an active multiplexing
912 controller
913 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
914 controllers
915 i8042.panicblink=
916 [HW] Frequency with which keyboard LEDs should blink
917 when kernel panics (default is 0.5 sec)
918 i8042.reset [HW] Reset the controller during init and cleanup
919 i8042.unlock [HW] Unlock (ignore) the keylock
921 i810= [HW,DRM]
923 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
924 indicates that the driver is running on unsupported
925 hardware.
926 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
927 does not match list of supported models.
928 i8k.power_status
929 [HW] Report power status in /proc/i8k
930 (disabled by default)
931 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
932 capability is set.
934 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
935 See Documentation/mca.txt.
937 icn= [HW,ISDN]
938 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
940 ide-core.nodma= [HW] (E)IDE subsystem
941 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
942 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
943 .cdrom .chs .ignore_cable are additional options
944 See Documentation/ide/ide.txt.
946 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
947 Claim all unknown PCI IDE storage controllers.
949 idle= [X86]
950 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
951 Poll forces a polling idle loop that can slightly
952 improve the performance of waking up a idle CPU, but
953 will use a lot of power and make the system run hot.
954 Not recommended.
955 idle=mwait: On systems which support MONITOR/MWAIT but
956 the kernel chose to not use it because it doesn't save
957 as much power as a normal idle loop, use the
958 MONITOR/MWAIT idle loop anyways. Performance should be
959 the same as idle=poll.
960 idle=halt: Halt is forced to be used for CPU idle.
961 In such case C2/C3 won't be used again.
962 idle=nomwait: Disable mwait for CPU C-states
964 ignore_loglevel [KNL]
965 Ignore loglevel setting - this will print /all/
966 kernel messages to the console. Useful for debugging.
968 ihash_entries= [KNL]
969 Set number of hash buckets for inode cache.
971 ima_audit= [IMA]
972 Format: { "0" | "1" }
973 0 -- integrity auditing messages. (Default)
974 1 -- enable informational integrity auditing messages.
976 ima_hash= [IMA]
977 Format: { "sha1" | "md5" }
978 default: "sha1"
980 ima_tcb [IMA]
981 Load a policy which meets the needs of the Trusted
982 Computing Base. This means IMA will measure all
983 programs exec'd, files mmap'd for exec, and all files
984 opened for read by uid=0.
986 in2000= [HW,SCSI]
987 See header of drivers/scsi/in2000.c.
989 init= [KNL]
990 Format: <full_path>
991 Run specified binary instead of /sbin/init as init
992 process.
994 initcall_debug [KNL] Trace initcalls as they are executed. Useful
995 for working out where the kernel is dying during
996 startup.
998 initrd= [BOOT] Specify the location of the initial ramdisk
1000 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1001 Format: <irq>
1003 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1004 on
1005 Enable intel iommu driver.
1006 off
1007 Disable intel iommu driver.
1008 igfx_off [Default Off]
1009 By default, gfx is mapped as normal device. If a gfx
1010 device has a dedicated DMAR unit, the DMAR unit is
1011 bypassed by not enabling DMAR with this option. In
1012 this case, gfx device will use physical address for
1013 DMA.
1014 forcedac [x86_64]
1015 With this option iommu will not optimize to look
1016 for io virtual address below 32 bit forcing dual
1017 address cycle on pci bus for cards supporting greater
1018 than 32 bit addressing. The default is to look
1019 for translation below 32 bit and if not available
1020 then look in the higher range.
1021 strict [Default Off]
1022 With this option on every unmap_single operation will
1023 result in a hardware IOTLB flush operation as opposed
1024 to batching them for performance.
1026 inttest= [IA64]
1028 iomem= Disable strict checking of access to MMIO memory
1029 strict regions from userspace.
1030 relaxed
1032 iommu= [x86]
1033 off
1034 force
1035 noforce
1036 biomerge
1037 panic
1038 nopanic
1039 merge
1040 nomerge
1041 forcesac
1042 soft
1043 pt [x86, IA64]
1045 io7= [HW] IO7 for Marvel based alpha systems
1046 See comment before marvel_specify_io7 in
1047 arch/alpha/kernel/core_marvel.c.
1049 io_delay= [X86] I/O delay method
1050 0x80
1051 Standard port 0x80 based delay
1052 0xed
1053 Alternate port 0xed based delay (needed on some systems)
1054 udelay
1055 Simple two microseconds delay
1056 none
1057 No delay
1059 ip= [IP_PNP]
1060 See Documentation/filesystems/nfs/nfsroot.txt.
1062 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1063 See comment before ip2_setup() in
1064 drivers/char/ip2/ip2base.c.
1066 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1067 See header of drivers/scsi/ips.c.
1069 irqfixup [HW]
1070 When an interrupt is not handled search all handlers
1071 for it. Intended to get systems with badly broken
1072 firmware running.
1074 irqpoll [HW]
1075 When an interrupt is not handled search all handlers
1076 for it. Also check all handlers each timer
1077 interrupt. Intended to get systems with badly broken
1078 firmware running.
1080 isapnp= [ISAPNP]
1081 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1083 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1084 Format:
1085 <cpu number>,...,<cpu number>
1086 or
1087 <cpu number>-<cpu number>
1088 (must be a positive range in ascending order)
1089 or a mixture
1090 <cpu number>,...,<cpu number>-<cpu number>
1092 This option can be used to specify one or more CPUs
1093 to isolate from the general SMP balancing and scheduling
1094 algorithms. You can move a process onto or off an
1095 "isolated" CPU via the CPU affinity syscalls or cpuset.
1096 <cpu number> begins at 0 and the maximum value is
1097 "number of CPUs in system - 1".
1099 This option is the preferred way to isolate CPUs. The
1100 alternative -- manually setting the CPU mask of all
1101 tasks in the system -- can cause problems and
1102 suboptimal load balancer performance.
1104 iucv= [HW,NET]
1106 js= [HW,JOY] Analog joystick
1107 See Documentation/input/joystick.txt.
1109 keepinitrd [HW,ARM]
1111 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1112 specifies the amount of memory usable by the kernel
1113 for non-movable allocations. The requested amount is
1114 spread evenly throughout all nodes in the system. The
1115 remaining memory in each node is used for Movable
1116 pages. In the event, a node is too small to have both
1117 kernelcore and Movable pages, kernelcore pages will
1118 take priority and other nodes will have a larger number
1119 of kernelcore pages. The Movable zone is used for the
1120 allocation of pages that may be reclaimed or moved
1121 by the page migration subsystem. This means that
1122 HugeTLB pages may not be allocated from this zone.
1123 Note that allocations like PTEs-from-HighMem still
1124 use the HighMem zone if it exists, and the Normal
1125 zone if it does not.
1127 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1128 Format: <Controller#>[,poll interval]
1129 The controller # is the number of the ehci usb debug
1130 port as it is probed via PCI. The poll interval is
1131 optional and is the number seconds in between
1132 each poll cycle to the debug port in case you need
1133 the functionality for interrupting the kernel with
1134 gdb or control-c on the dbgp connection. When
1135 not using this parameter you use sysrq-g to break into
1136 the kernel debugger.
1138 kgdboc= [KGDB,HW] kgdb over consoles.
1139 Requires a tty driver that supports console polling,
1140 or a supported polling keyboard driver (non-usb).
1141 Serial only format: <serial_device>[,baud]
1142 keyboard only format: kbd
1143 keyboard and serial format: kbd,<serial_device>[,baud]
1144 Optional Kernel mode setting:
1145 kms, kbd format: kms,kbd
1146 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1148 kgdbwait [KGDB] Stop kernel execution and enter the
1149 kernel debugger at the earliest opportunity.
1151 kmac= [MIPS] korina ethernet MAC address.
1152 Configure the RouterBoard 532 series on-chip
1153 Ethernet adapter MAC address.
1155 kmemleak= [KNL] Boot-time kmemleak enable/disable
1156 Valid arguments: on, off
1157 Default: on
1159 kstack=N [X86] Print N words from the kernel stack
1160 in oops dumps.
1162 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1163 Default is 0 (don't ignore, but inject #GP)
1165 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1166 Default is 1 (enabled)
1168 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1169 Default is 0 (off)
1171 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1172 for all guests.
1173 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1175 kvm-intel.bypass_guest_pf=
1176 [KVM,Intel] Disables bypassing of guest page faults
1177 on Intel chips. Default is 1 (enabled)
1179 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1180 (virtualized MMU) support on capable Intel chips.
1181 Default is 1 (enabled)
1183 kvm-intel.emulate_invalid_guest_state=
1184 [KVM,Intel] Enable emulation of invalid guest states
1185 Default is 0 (disabled)
1187 kvm-intel.flexpriority=
1188 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1189 Default is 1 (enabled)
1191 kvm-intel.unrestricted_guest=
1192 [KVM,Intel] Disable unrestricted guest feature
1193 (virtualized real and unpaged mode) on capable
1194 Intel chips. Default is 1 (enabled)
1196 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1197 feature (tagged TLBs) on capable Intel chips.
1198 Default is 1 (enabled)
1200 l2cr= [PPC]
1202 l3cr= [PPC]
1204 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1205 disabled it.
1207 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1208 in C2 power state.
1210 libata.dma= [LIBATA] DMA control
1211 libata.dma=0 Disable all PATA and SATA DMA
1212 libata.dma=1 PATA and SATA Disk DMA only
1213 libata.dma=2 ATAPI (CDROM) DMA only
1214 libata.dma=4 Compact Flash DMA only
1215 Combinations also work, so libata.dma=3 enables DMA
1216 for disks and CDROMs, but not CFs.
1218 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1219 libata.ignore_hpa=0 keep BIOS limits (default)
1220 libata.ignore_hpa=1 ignore limits, using full disk
1222 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1223 when set.
1224 Format: <int>
1226 libata.force= [LIBATA] Force configurations. The format is comma
1227 separated list of "[ID:]VAL" where ID is
1228 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1229 matching port, link or device. Basically, it matches
1230 the ATA ID string printed on console by libata. If
1231 the whole ID part is omitted, the last PORT and DEVICE
1232 values are used. If ID hasn't been specified yet, the
1233 configuration applies to all ports, links and devices.
1235 If only DEVICE is omitted, the parameter applies to
1236 the port and all links and devices behind it. DEVICE
1237 number of 0 either selects the first device or the
1238 first fan-out link behind PMP device. It does not
1239 select the host link. DEVICE number of 15 selects the
1240 host link and device attached to it.
1242 The VAL specifies the configuration to force. As long
1243 as there's no ambiguity shortcut notation is allowed.
1244 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1245 The following configurations can be forced.
1247 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1248 Any ID with matching PORT is used.
1250 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1252 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1253 udma[/][16,25,33,44,66,100,133] notation is also
1254 allowed.
1256 * [no]ncq: Turn on or off NCQ.
1258 * nohrst, nosrst, norst: suppress hard, soft
1259 and both resets.
1261 * dump_id: dump IDENTIFY data.
1263 If there are multiple matching configurations changing
1264 the same attribute, the last one is used.
1266 memblock=debug [KNL] Enable memblock debug messages.
1268 load_ramdisk= [RAM] List of ramdisks to load from floppy
1269 See Documentation/blockdev/ramdisk.txt.
1271 lockd.nlm_grace_period=P [NFS] Assign grace period.
1272 Format: <integer>
1274 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1275 Format: <integer>
1277 lockd.nlm_timeout=T [NFS] Assign timeout value.
1278 Format: <integer>
1280 lockd.nlm_udpport=M [NFS] Assign UDP port.
1281 Format: <integer>
1283 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1284 Format: <irq>
1286 loglevel= All Kernel Messages with a loglevel smaller than the
1287 console loglevel will be printed to the console. It can
1288 also be changed with klogd or other programs. The
1289 loglevels are defined as follows:
1291 0 (KERN_EMERG) system is unusable
1292 1 (KERN_ALERT) action must be taken immediately
1293 2 (KERN_CRIT) critical conditions
1294 3 (KERN_ERR) error conditions
1295 4 (KERN_WARNING) warning conditions
1296 5 (KERN_NOTICE) normal but significant condition
1297 6 (KERN_INFO) informational
1298 7 (KERN_DEBUG) debug-level messages
1300 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1301 Format: { n | nk | nM }
1302 n must be a power of two. The default size
1303 is set in the kernel config file.
1305 logo.nologo [FB] Disables display of the built-in Linux logo.
1306 This may be used to provide more screen space for
1307 kernel log messages and is useful when debugging
1308 kernel boot problems.
1310 lp=0 [LP] Specify parallel ports to use, e.g,
1311 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1312 lp=reset first parallel port). 'lp=0' disables the
1313 lp=auto printer driver. 'lp=reset' (which can be
1314 specified in addition to the ports) causes
1315 attached printers to be reset. Using
1316 lp=port1,port2,... specifies the parallel ports
1317 to associate lp devices with, starting with
1318 lp0. A port specification may be 'none' to skip
1319 that lp device, or a parport name such as
1320 'parport0'. Specifying 'lp=auto' instead of a
1321 port specification list means that device IDs
1322 from each port should be examined, to see if
1323 an IEEE 1284-compliant printer is attached; if
1324 so, the driver will manage that printer.
1325 See also header of drivers/char/lp.c.
1327 lpj=n [KNL]
1328 Sets loops_per_jiffy to given constant, thus avoiding
1329 time-consuming boot-time autodetection (up to 250 ms per
1330 CPU). 0 enables autodetection (default). To determine
1331 the correct value for your kernel, boot with normal
1332 autodetection and see what value is printed. Note that
1333 on SMP systems the preset will be applied to all CPUs,
1334 which is likely to cause problems if your CPUs need
1335 significantly divergent settings. An incorrect value
1336 will cause delays in the kernel to be wrong, leading to
1337 unpredictable I/O errors and other breakage. Although
1338 unlikely, in the extreme case this might damage your
1339 hardware.
1341 ltpc= [NET]
1342 Format: <io>,<irq>,<dma>
1344 mac5380= [HW,SCSI] Format:
1345 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1347 machvec= [IA64] Force the use of a particular machine-vector
1348 (machvec) in a generic kernel.
1349 Example: machvec=hpzx1_swiotlb
1351 machtype= [Loongson] Share the same kernel image file between different
1352 yeeloong laptop.
1353 Example: machtype=lemote-yeeloong-2f-7inch
1355 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1356 than or equal to this physical address is ignored.
1358 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1359 should make use of. maxcpus=n : n >= 0 limits the
1360 kernel to using 'n' processors. n=0 is a special case,
1361 it is equivalent to "nosmp", which also disables
1362 the IO APIC.
1364 max_loop= [LOOP] Maximum number of loopback devices that can
1365 be mounted
1366 Format: <1-256>
1368 max_luns= [SCSI] Maximum number of LUNs to probe.
1369 Should be between 1 and 2^32-1.
1371 max_report_luns=
1372 [SCSI] Maximum number of LUNs received.
1373 Should be between 1 and 16384.
1375 mcatest= [IA-64]
1377 mce [X86-32] Machine Check Exception
1379 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1381 md= [HW] RAID subsystems devices and level
1382 See Documentation/md.txt.
1384 mdacon= [MDA]
1385 Format: <first>,<last>
1386 Specifies range of consoles to be captured by the MDA.
1388 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1389 Amount of memory to be used when the kernel is not able
1390 to see the whole system memory or for test.
1391 [X86-32] Use together with memmap= to avoid physical
1392 address space collisions. Without memmap= PCI devices
1393 could be placed at addresses belonging to unused RAM.
1395 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1396 memory.
1398 memchunk=nn[KMG]
1399 [KNL,SH] Allow user to override the default size for
1400 per-device physically contiguous DMA buffers.
1402 memmap=exactmap [KNL,X86] Enable setting of an exact
1403 E820 memory map, as specified by the user.
1404 Such memmap=exactmap lines can be constructed based on
1405 BIOS output or other requirements. See the memmap=nn@ss
1406 option description.
1408 memmap=nn[KMG]@ss[KMG]
1409 [KNL] Force usage of a specific region of memory
1410 Region of memory to be used, from ss to ss+nn.
1412 memmap=nn[KMG]#ss[KMG]
1413 [KNL,ACPI] Mark specific memory as ACPI data.
1414 Region of memory to be used, from ss to ss+nn.
1416 memmap=nn[KMG]$ss[KMG]
1417 [KNL,ACPI] Mark specific memory as reserved.
1418 Region of memory to be used, from ss to ss+nn.
1419 Example: Exclude memory from 0x18690000-0x1869ffff
1420 memmap=64K$0x18690000
1421 or
1422 memmap=0x10000$0x18690000
1424 memory_corruption_check=0/1 [X86]
1425 Some BIOSes seem to corrupt the first 64k of
1426 memory when doing things like suspend/resume.
1427 Setting this option will scan the memory
1428 looking for corruption. Enabling this will
1429 both detect corruption and prevent the kernel
1430 from using the memory being corrupted.
1431 However, its intended as a diagnostic tool; if
1432 repeatable BIOS-originated corruption always
1433 affects the same memory, you can use memmap=
1434 to prevent the kernel from using that memory.
1436 memory_corruption_check_size=size [X86]
1437 By default it checks for corruption in the low
1438 64k, making this memory unavailable for normal
1439 use. Use this parameter to scan for
1440 corruption in more or less memory.
1442 memory_corruption_check_period=seconds [X86]
1443 By default it checks for corruption every 60
1444 seconds. Use this parameter to check at some
1445 other rate. 0 disables periodic checking.
1447 memtest= [KNL,X86] Enable memtest
1448 Format: <integer>
1449 default : 0 <disable>
1450 Specifies the number of memtest passes to be
1451 performed. Each pass selects another test
1452 pattern from a given set of patterns. Memtest
1453 fills the memory with this pattern, validates
1454 memory contents and reserves bad memory
1455 regions that are detected.
1457 meye.*= [HW] Set MotionEye Camera parameters
1458 See Documentation/video4linux/meye.txt.
1460 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1461 Multi-Function General Purpose Timers on AMD Geode
1462 platforms.
1464 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1465 the BIOS has incorrectly applied a workaround. TinyBIOS
1466 version 0.98 is known to be affected, 0.99 fixes the
1467 problem by letting the user disable the workaround.
1469 mga= [HW,DRM]
1471 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1472 physical address is ignored.
1474 mini2440= [ARM,HW,KNL]
1475 Format:[0..2][b][c][t]
1476 Default: "0tb"
1477 MINI2440 configuration specification:
1478 0 - The attached screen is the 3.5" TFT
1479 1 - The attached screen is the 7" TFT
1480 2 - The VGA Shield is attached (1024x768)
1481 Leaving out the screen size parameter will not load
1482 the TFT driver, and the framebuffer will be left
1483 unconfigured.
1484 b - Enable backlight. The TFT backlight pin will be
1485 linked to the kernel VESA blanking code and a GPIO
1486 LED. This parameter is not necessary when using the
1487 VGA shield.
1488 c - Enable the s3c camera interface.
1489 t - Reserved for enabling touchscreen support. The
1490 touchscreen support is not enabled in the mainstream
1491 kernel as of 2.6.30, a preliminary port can be found
1492 in the "bleeding edge" mini2440 support kernel at
1493 http://repo.or.cz/w/linux-2.6/mini2440.git
1495 mminit_loglevel=
1496 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1497 parameter allows control of the logging verbosity for
1498 the additional memory initialisation checks. A value
1499 of 0 disables mminit logging and a level of 4 will
1500 log everything. Information is printed at KERN_DEBUG
1501 so loglevel=8 may also need to be specified.
1503 mousedev.tap_time=
1504 [MOUSE] Maximum time between finger touching and
1505 leaving touchpad surface for touch to be considered
1506 a tap and be reported as a left button click (for
1507 touchpads working in absolute mode only).
1508 Format: <msecs>
1509 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1510 reporting absolute coordinates, such as tablets
1511 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1512 reporting absolute coordinates, such as tablets
1514 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1515 is similar to kernelcore except it specifies the
1516 amount of memory used for migratable allocations.
1517 If both kernelcore and movablecore is specified,
1518 then kernelcore will be at *least* the specified
1519 value but may be more. If movablecore on its own
1520 is specified, the administrator must be careful
1521 that the amount of memory usable for all allocations
1522 is not too small.
1524 MTD_Partition= [MTD]
1525 Format: <name>,<region-number>,<size>,<offset>
1527 MTD_Region= [MTD] Format:
1528 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1530 mtdparts= [MTD]
1531 See drivers/mtd/cmdlinepart.c.
1533 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1535 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1537 boundary - index of last SLC block on Flex-OneNAND.
1538 The remaining blocks are configured as MLC blocks.
1539 lock - Configure if Flex-OneNAND boundary should be locked.
1540 Once locked, the boundary cannot be changed.
1541 1 indicates lock status, 0 indicates unlock status.
1543 mtdset= [ARM]
1544 ARM/S3C2412 JIVE boot control
1546 See arch/arm/mach-s3c2412/mach-jive.c
1548 mtouchusb.raw_coordinates=
1549 [HW] Make the MicroTouch USB driver use raw coordinates
1550 ('y', default) or cooked coordinates ('n')
1552 mtrr_chunk_size=nn[KMG] [X86]
1553 used for mtrr cleanup. It is largest continuous chunk
1554 that could hold holes aka. UC entries.
1556 mtrr_gran_size=nn[KMG] [X86]
1557 Used for mtrr cleanup. It is granularity of mtrr block.
1558 Default is 1.
1559 Large value could prevent small alignment from
1560 using up MTRRs.
1562 mtrr_spare_reg_nr=n [X86]
1563 Format: <integer>
1564 Range: 0,7 : spare reg number
1565 Default : 1
1566 Used for mtrr cleanup. It is spare mtrr entries number.
1567 Set to 2 or more if your graphical card needs more.
1569 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1571 NCR_D700= [HW,SCSI]
1572 See header of drivers/scsi/NCR_D700.c.
1574 ncr5380= [HW,SCSI]
1576 ncr53c400= [HW,SCSI]
1578 ncr53c400a= [HW,SCSI]
1580 ncr53c406a= [HW,SCSI]
1582 ncr53c8xx= [HW,SCSI]
1584 netdev= [NET] Network devices parameters
1585 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1586 Note that mem_start is often overloaded to mean
1587 something different and driver-specific.
1588 This usage is only documented in each driver source
1589 file if at all.
1591 nf_conntrack.acct=
1592 [NETFILTER] Enable connection tracking flow accounting
1593 0 to disable accounting
1594 1 to enable accounting
1595 Default value is 0.
1597 nfsaddrs= [NFS]
1598 See Documentation/filesystems/nfs/nfsroot.txt.
1600 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1601 See Documentation/filesystems/nfs/nfsroot.txt.
1603 nfs.callback_tcpport=
1604 [NFS] set the TCP port on which the NFSv4 callback
1605 channel should listen.
1607 nfs.cache_getent=
1608 [NFS] sets the pathname to the program which is used
1609 to update the NFS client cache entries.
1611 nfs.cache_getent_timeout=
1612 [NFS] sets the timeout after which an attempt to
1613 update a cache entry is deemed to have failed.
1615 nfs.idmap_cache_timeout=
1616 [NFS] set the maximum lifetime for idmapper cache
1617 entries.
1619 nfs.enable_ino64=
1620 [NFS] enable 64-bit inode numbers.
1621 If zero, the NFS client will fake up a 32-bit inode
1622 number for the readdir() and stat() syscalls instead
1623 of returning the full 64-bit number.
1624 The default is to return 64-bit inode numbers.
1626 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1627 when a NMI is triggered.
1628 Format: [state][,regs][,debounce][,die]
1630 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1631 Format: [panic,][num]
1632 Valid num: 0,1,2
1633 0 - turn nmi_watchdog off
1634 1 - use the IO-APIC timer for the NMI watchdog
1635 2 - use the local APIC for the NMI watchdog using
1636 a performance counter. Note: This will use one
1637 performance counter and the local APIC's performance
1638 vector.
1639 When panic is specified, panic when an NMI watchdog
1640 timeout occurs.
1641 This is useful when you use a panic=... timeout and
1642 need the box quickly up again.
1643 Instead of 1 and 2 it is possible to use the following
1644 symbolic names: lapic and ioapic
1645 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1647 netpoll.carrier_timeout=
1648 [NET] Specifies amount of time (in seconds) that
1649 netpoll should wait for a carrier. By default netpoll
1650 waits 4 seconds.
1652 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1653 emulation library even if a 387 maths coprocessor
1654 is present.
1656 no_console_suspend
1657 [HW] Never suspend the console
1658 Disable suspending of consoles during suspend and
1659 hibernate operations. Once disabled, debugging
1660 messages can reach various consoles while the rest
1661 of the system is being put to sleep (ie, while
1662 debugging driver suspend/resume hooks). This may
1663 not work reliably with all consoles, but is known
1664 to work with serial and VGA consoles.
1666 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1667 caches in the slab allocator. Saves per-node memory,
1668 but will impact performance.
1670 noalign [KNL,ARM]
1672 noapic [SMP,APIC] Tells the kernel to not make use of any
1673 IOAPICs that may be present in the system.
1675 nobats [PPC] Do not use BATs for mapping kernel lowmem
1676 on "Classic" PPC cores.
1678 nocache [ARM]
1680 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1682 nodelayacct [KNL] Disable per-task delay accounting
1684 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1686 nodsp [SH] Disable hardware DSP at boot time.
1688 noefi [X86] Disable EFI runtime services support.
1690 noexec [IA-64]
1692 noexec [X86]
1693 On X86-32 available only on PAE configured kernels.
1694 noexec=on: enable non-executable mappings (default)
1695 noexec=off: disable non-executable mappings
1697 noexec32 [X86-64]
1698 This affects only 32-bit executables.
1699 noexec32=on: enable non-executable mappings (default)
1700 read doesn't imply executable mappings
1701 noexec32=off: disable non-executable mappings
1702 read implies executable mappings
1704 nofpu [SH] Disable hardware FPU at boot time.
1706 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1707 register save and restore. The kernel will only save
1708 legacy floating-point registers on task switch.
1710 noxsave [BUGS=X86] Disables x86 extended register state save
1711 and restore using xsave. The kernel will fallback to
1712 enabling legacy floating-point and sse state.
1714 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1715 wfi(ARM) instruction doesn't work correctly and not to
1716 use it. This is also useful when using JTAG debugger.
1718 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1719 instruction doesn't work correctly and not to
1720 use it.
1722 no_file_caps Tells the kernel not to honor file capabilities. The
1723 only way then for a file to be executed with privilege
1724 is to be setuid root or executed by root.
1726 nohalt [IA-64] Tells the kernel not to use the power saving
1727 function PAL_HALT_LIGHT when idle. This increases
1728 power-consumption. On the positive side, it reduces
1729 interrupt wake-up latency, which may improve performance
1730 in certain environments such as networked servers or
1731 real-time systems.
1733 nohz= [KNL] Boottime enable/disable dynamic ticks
1734 Valid arguments: on, off
1735 Default: on
1737 noiotrap [SH] Disables trapped I/O port accesses.
1739 noirqdebug [X86-32] Disables the code which attempts to detect and
1740 disable unhandled interrupt sources.
1742 no_timer_check [X86,APIC] Disables the code which tests for
1743 broken timer IRQ sources.
1745 noisapnp [ISAPNP] Disables ISA PnP code.
1747 noinitrd [RAM] Tells the kernel not to load any configured
1748 initial RAM disk.
1750 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1751 remapping.
1753 nointroute [IA-64]
1755 nojitter [IA64] Disables jitter checking for ITC timers.
1757 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1759 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1761 noltlbs [PPC] Do not use large page/tlb entries for kernel
1762 lowmem mapping on PPC40x.
1764 nomca [IA-64] Disable machine check abort handling
1766 nomce [X86-32] Machine Check Exception
1768 nomfgpt [X86-32] Disable Multi-Function General Purpose
1769 Timer usage (for AMD Geode machines).
1771 nopat [X86] Disable PAT (page attribute table extension of
1772 pagetables) support.
1774 norandmaps Don't use address space randomization. Equivalent to
1775 echo 0 > /proc/sys/kernel/randomize_va_space
1777 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1779 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1780 with UP alternatives
1782 noresidual [PPC] Don't use residual data on PReP machines.
1784 noresume [SWSUSP] Disables resume and restores original swap
1785 space.
1787 no-scroll [VGA] Disables scrollback.
1788 This is required for the Braillex ib80-piezo Braille
1789 reader made by F.H. Papenmeier (Germany).
1791 nosbagart [IA-64]
1793 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1795 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1796 and disable the IO APIC. legacy for "maxcpus=0".
1798 nosoftlockup [KNL] Disable the soft-lockup detector.
1800 noswapaccount [KNL] Disable accounting of swap in memory resource
1801 controller. (See Documentation/cgroups/memory.txt)
1803 nosync [HW,M68K] Disables sync negotiation for all devices.
1805 notsc [BUGS=X86-32] Disable Time Stamp Counter
1807 nousb [USB] Disable the USB subsystem
1809 nowatchdog [KNL] Disable the lockup detector.
1811 nowb [ARM]
1813 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1815 nptcg= [IA64] Override max number of concurrent global TLB
1816 purges which is reported from either PAL_VM_SUMMARY or
1817 SAL PALO.
1819 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1820 could support. nr_cpus=n : n >= 1 limits the kernel to
1821 supporting 'n' processors. Later in runtime you can not
1822 use hotplug cpu feature to put more cpu back to online.
1823 just like you compile the kernel NR_CPUS=n
1825 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1827 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1828 one of ['zone', 'node', 'default'] can be specified
1829 This can be set from sysctl after boot.
1830 See Documentation/sysctl/vm.txt for details.
1832 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1833 See Documentation/debugging-via-ohci1394.txt for more
1834 info.
1836 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1837 Rather than timing out after 20 ms if an EC
1838 command is not properly ACKed, override the length
1839 of the timeout. We have interrupts disabled while
1840 waiting for the ACK, so if this is set too high
1841 interrupts *may* be lost!
1843 omap_mux= [OMAP] Override bootloader pin multiplexing.
1844 Format: <mux_mode0.mode_name=value>...
1845 For example, to override I2C bus2:
1846 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1848 oprofile.timer= [HW]
1849 Use timer interrupt instead of performance counters
1851 oprofile.cpu_type= Force an oprofile cpu type
1852 This might be useful if you have an older oprofile
1853 userland or if you want common events.
1854 Format: { arch_perfmon }
1855 arch_perfmon: [X86] Force use of architectural
1856 perfmon on Intel CPUs instead of the
1857 CPU specific event set.
1859 OSS [HW,OSS]
1860 See Documentation/sound/oss/oss-parameters.txt
1862 osst= [HW,SCSI] SCSI Tape Driver
1863 Format: <buffer_size>,<write_threshold>
1864 See also Documentation/scsi/st.txt.
1866 panic= [KNL] Kernel behaviour on panic
1867 Format: <timeout>
1869 parkbd.port= [HW] Parallel port number the keyboard adapter is
1870 connected to, default is 0.
1871 Format: <parport#>
1872 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1873 0 for XT, 1 for AT (default is AT).
1874 Format: <mode>
1876 parport= [HW,PPT] Specify parallel ports. 0 disables.
1877 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1878 Use 'auto' to force the driver to use any
1879 IRQ/DMA settings detected (the default is to
1880 ignore detected IRQ/DMA settings because of
1881 possible conflicts). You can specify the base
1882 address, IRQ, and DMA settings; IRQ and DMA
1883 should be numbers, or 'auto' (for using detected
1884 settings on that particular port), or 'nofifo'
1885 (to avoid using a FIFO even if it is detected).
1886 Parallel ports are assigned in the order they
1887 are specified on the command line, starting
1888 with parport0.
1890 parport_init_mode= [HW,PPT]
1891 Configure VIA parallel port to operate in
1892 a specific mode. This is necessary on Pegasos
1893 computer where firmware has no options for setting
1894 up parallel port mode and sets it to spp.
1895 Currently this function knows 686a and 8231 chips.
1896 Format: [spp|ps2|epp|ecp|ecpepp]
1898 pas16= [HW,SCSI]
1899 See header of drivers/scsi/pas16.c.
1901 pause_on_oops=
1902 Halt all CPUs after the first oops has been printed for
1903 the specified number of seconds. This is to be used if
1904 your oopses keep scrolling off the screen.
1906 pcbit= [HW,ISDN]
1908 pcd. [PARIDE]
1909 See header of drivers/block/paride/pcd.c.
1910 See also Documentation/blockdev/paride.txt.
1912 pci=option[,option...] [PCI] various PCI subsystem options:
1913 earlydump [X86] dump PCI config space before the kernel
1914 changes anything
1915 off [X86] don't probe for the PCI bus
1916 bios [X86-32] force use of PCI BIOS, don't access
1917 the hardware directly. Use this if your machine
1918 has a non-standard PCI host bridge.
1919 nobios [X86-32] disallow use of PCI BIOS, only direct
1920 hardware access methods are allowed. Use this
1921 if you experience crashes upon bootup and you
1922 suspect they are caused by the BIOS.
1923 conf1 [X86] Force use of PCI Configuration
1924 Mechanism 1.
1925 conf2 [X86] Force use of PCI Configuration
1926 Mechanism 2.
1927 noaer [PCIE] If the PCIEAER kernel config parameter is
1928 enabled, this kernel boot option can be used to
1929 disable the use of PCIE advanced error reporting.
1930 nodomains [PCI] Disable support for multiple PCI
1931 root domains (aka PCI segments, in ACPI-speak).
1932 nommconf [X86] Disable use of MMCONFIG for PCI
1933 Configuration
1934 check_enable_amd_mmconf [X86] check for and enable
1935 properly configured MMIO access to PCI
1936 config space on AMD family 10h CPU
1937 nomsi [MSI] If the PCI_MSI kernel config parameter is
1938 enabled, this kernel boot option can be used to
1939 disable the use of MSI interrupts system-wide.
1940 noioapicquirk [APIC] Disable all boot interrupt quirks.
1941 Safety option to keep boot IRQs enabled. This
1942 should never be necessary.
1943 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1944 primary IO-APIC for bridges that cannot disable
1945 boot IRQs. This fixes a source of spurious IRQs
1946 when the system masks IRQs.
1947 noioapicreroute [APIC] Disable workaround that uses the
1948 boot IRQ equivalent of an IRQ that connects to
1949 a chipset where boot IRQs cannot be disabled.
1950 The opposite of ioapicreroute.
1951 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1952 routing table. These calls are known to be buggy
1953 on several machines and they hang the machine
1954 when used, but on other computers it's the only
1955 way to get the interrupt routing table. Try
1956 this option if the kernel is unable to allocate
1957 IRQs or discover secondary PCI buses on your
1958 motherboard.
1959 rom [X86] Assign address space to expansion ROMs.
1960 Use with caution as certain devices share
1961 address decoders between ROMs and other
1962 resources.
1963 norom [X86] Do not assign address space to
1964 expansion ROMs that do not already have
1965 BIOS assigned address ranges.
1966 nobar [X86] Do not assign address space to the
1967 BARs that weren't assigned by the BIOS.
1968 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1969 assigned automatically to PCI devices. You can
1970 make the kernel exclude IRQs of your ISA cards
1971 this way.
1972 pirqaddr=0xAAAAA [X86] Specify the physical address
1973 of the PIRQ table (normally generated
1974 by the BIOS) if it is outside the
1975 F0000h-100000h range.
1976 lastbus=N [X86] Scan all buses thru bus #N. Can be
1977 useful if the kernel is unable to find your
1978 secondary buses and you want to tell it
1979 explicitly which ones they are.
1980 assign-busses [X86] Always assign all PCI bus
1981 numbers ourselves, overriding
1982 whatever the firmware may have done.
1983 usepirqmask [X86] Honor the possible IRQ mask stored
1984 in the BIOS $PIR table. This is needed on
1985 some systems with broken BIOSes, notably
1986 some HP Pavilion N5400 and Omnibook XE3
1987 notebooks. This will have no effect if ACPI
1988 IRQ routing is enabled.
1989 noacpi [X86] Do not use ACPI for IRQ routing
1990 or for PCI scanning.
1991 use_crs [X86] Use PCI host bridge window information
1992 from ACPI. On BIOSes from 2008 or later, this
1993 is enabled by default. If you need to use this,
1994 please report a bug.
1995 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1996 If you need to use this, please report a bug.
1997 routeirq Do IRQ routing for all PCI devices.
1998 This is normally done in pci_enable_device(),
1999 so this option is a temporary workaround
2000 for broken drivers that don't call it.
2001 skip_isa_align [X86] do not align io start addr, so can
2002 handle more pci cards
2003 firmware [ARM] Do not re-enumerate the bus but instead
2004 just use the configuration from the
2005 bootloader. This is currently used on
2006 IXP2000 systems where the bus has to be
2007 configured a certain way for adjunct CPUs.
2008 noearly [X86] Don't do any early type 1 scanning.
2009 This might help on some broken boards which
2010 machine check when some devices' config space
2011 is read. But various workarounds are disabled
2012 and some IOMMU drivers will not work.
2013 bfsort Sort PCI devices into breadth-first order.
2014 This sorting is done to get a device
2015 order compatible with older (<= 2.4) kernels.
2016 nobfsort Don't sort PCI devices into breadth-first order.
2017 cbiosize=nn[KMG] The fixed amount of bus space which is
2018 reserved for the CardBus bridge's IO window.
2019 The default value is 256 bytes.
2020 cbmemsize=nn[KMG] The fixed amount of bus space which is
2021 reserved for the CardBus bridge's memory
2022 window. The default value is 64 megabytes.
2023 resource_alignment=
2024 Format:
2025 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2026 Specifies alignment and device to reassign
2027 aligned memory resources.
2028 If <order of align> is not specified,
2029 PAGE_SIZE is used as alignment.
2030 PCI-PCI bridge can be specified, if resource
2031 windows need to be expanded.
2032 ecrc= Enable/disable PCIe ECRC (transaction layer
2033 end-to-end CRC checking).
2034 bios: Use BIOS/firmware settings. This is the
2035 the default.
2036 off: Turn ECRC off
2037 on: Turn ECRC on.
2039 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2040 Management.
2041 off Disable ASPM.
2042 force Enable ASPM even on devices that claim not to support it.
2043 WARNING: Forcing ASPM on may cause system lockups.
2045 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2046 Format: {auto|force}[,nomsi]
2047 auto Use native PCIe PME signaling if the BIOS allows the
2048 kernel to control PCIe config registers of root ports.
2049 force Use native PCIe PME signaling even if the BIOS refuses
2050 to allow the kernel to control the relevant PCIe config
2051 registers.
2052 nomsi Do not use MSI for native PCIe PME signaling (this makes
2053 all PCIe root ports use INTx for everything).
2055 pcmv= [HW,PCMCIA] BadgePAD 4
2057 pd. [PARIDE]
2058 See Documentation/blockdev/paride.txt.
2060 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2061 boot time.
2062 Format: { 0 | 1 }
2063 See arch/parisc/kernel/pdc_chassis.c
2065 percpu_alloc= Select which percpu first chunk allocator to use.
2066 Currently supported values are "embed" and "page".
2067 Archs may support subset or none of the selections.
2068 See comments in mm/percpu.c for details on each
2069 allocator. This parameter is primarily for debugging
2070 and performance comparison.
2072 pf. [PARIDE]
2073 See Documentation/blockdev/paride.txt.
2075 pg. [PARIDE]
2076 See Documentation/blockdev/paride.txt.
2078 pirq= [SMP,APIC] Manual mp-table setup
2079 See Documentation/x86/i386/IO-APIC.txt.
2081 plip= [PPT,NET] Parallel port network link
2082 Format: { parport<nr> | timid | 0 }
2083 See also Documentation/parport.txt.
2085 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2086 Override pmtimer IOPort with a hex value.
2087 e.g. pmtmr=0x508
2089 pnp.debug [PNP]
2090 Enable PNP debug messages. This depends on the
2091 CONFIG_PNP_DEBUG_MESSAGES option.
2093 pnpacpi= [ACPI]
2094 { off }
2096 pnpbios= [ISAPNP]
2097 { on | off | curr | res | no-curr | no-res }
2099 pnp_reserve_irq=
2100 [ISAPNP] Exclude IRQs for the autoconfiguration
2102 pnp_reserve_dma=
2103 [ISAPNP] Exclude DMAs for the autoconfiguration
2105 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2106 Ranges are in pairs (I/O port base and size).
2108 pnp_reserve_mem=
2109 [ISAPNP] Exclude memory regions for the
2110 autoconfiguration.
2111 Ranges are in pairs (memory base and size).
2113 ports= [IP_VS_FTP] IPVS ftp helper module
2114 Default is 21.
2115 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2116 may be specified.
2117 Format: <port>,<port>....
2119 print-fatal-signals=
2120 [KNL] debug: print fatal signals
2122 If enabled, warn about various signal handling
2123 related application anomalies: too many signals,
2124 too many POSIX.1 timers, fatal signals causing a
2125 coredump - etc.
2127 If you hit the warning due to signal overflow,
2128 you might want to try "ulimit -i unlimited".
2130 default: off.
2132 printk.time= Show timing data prefixed to each printk message line
2133 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2135 processor.max_cstate= [HW,ACPI]
2136 Limit processor to maximum C-state
2137 max_cstate=9 overrides any DMI blacklist limit.
2139 processor.nocst [HW,ACPI]
2140 Ignore the _CST method to determine C-states,
2141 instead using the legacy FADT method
2143 profile= [KNL] Enable kernel profiling via /proc/profile
2144 Format: [schedule,]<number>
2145 Param: "schedule" - profile schedule points.
2146 Param: <number> - step/bucket size as a power of 2 for
2147 statistical time based profiling.
2148 Param: "sleep" - profile D-state sleeping (millisecs).
2149 Requires CONFIG_SCHEDSTATS
2150 Param: "kvm" - profile VM exits.
2152 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2153 before loading.
2154 See Documentation/blockdev/ramdisk.txt.
2156 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2157 probe for; one of (bare|imps|exps|lifebook|any).
2158 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2159 per second.
2160 psmouse.resetafter= [HW,MOUSE]
2161 Try to reset the device after so many bad packets
2162 (0 = never).
2163 psmouse.resolution=
2164 [HW,MOUSE] Set desired mouse resolution, in dpi.
2165 psmouse.smartscroll=
2166 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2167 0 = disabled, 1 = enabled (default).
2169 pt. [PARIDE]
2170 See Documentation/blockdev/paride.txt.
2172 pty.legacy_count=
2173 [KNL] Number of legacy pty's. Overwrites compiled-in
2174 default number.
2176 quiet [KNL] Disable most log messages
2178 r128= [HW,DRM]
2180 raid= [HW,RAID]
2181 See Documentation/md.txt.
2183 ramdisk_blocksize= [RAM]
2184 See Documentation/blockdev/ramdisk.txt.
2186 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2187 See Documentation/blockdev/ramdisk.txt.
2189 rcupdate.blimit= [KNL,BOOT]
2190 Set maximum number of finished RCU callbacks to process
2191 in one batch.
2193 rcupdate.qhimark= [KNL,BOOT]
2194 Set threshold of queued
2195 RCU callbacks over which batch limiting is disabled.
2197 rcupdate.qlowmark= [KNL,BOOT]
2198 Set threshold of queued RCU callbacks below which
2199 batch limiting is re-enabled.
2201 rdinit= [KNL]
2202 Format: <full_path>
2203 Run specified binary instead of /init from the ramdisk,
2204 used for early userspace startup. See initrd.
2206 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2207 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2208 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2210 relax_domain_level=
2211 [KNL, SMP] Set scheduler's default relax_domain_level.
2212 See Documentation/cgroups/cpusets.txt.
2214 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2216 reservetop= [X86-32]
2217 Format: nn[KMG]
2218 Reserves a hole at the top of the kernel virtual
2219 address space.
2221 reset_devices [KNL] Force drivers to reset the underlying device
2222 during initialization.
2224 resume= [SWSUSP]
2225 Specify the partition device for software suspend
2227 resume_offset= [SWSUSP]
2228 Specify the offset from the beginning of the partition
2229 given by "resume=" at which the swap header is located,
2230 in <PAGE_SIZE> units (needed only for swap files).
2231 See Documentation/power/swsusp-and-swap-files.txt
2233 retain_initrd [RAM] Keep initrd memory after extraction
2235 rhash_entries= [KNL,NET]
2236 Set number of hash buckets for route cache
2238 riscom8= [HW,SERIAL]
2239 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2241 ro [KNL] Mount root device read-only on boot
2243 root= [KNL] Root filesystem
2245 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2246 mount the root filesystem
2248 rootflags= [KNL] Set root filesystem mount option string
2250 rootfstype= [KNL] Set root filesystem type
2252 rootwait [KNL] Wait (indefinitely) for root device to show up.
2253 Useful for devices that are detected asynchronously
2254 (e.g. USB and MMC devices).
2256 rw [KNL] Mount root device read-write on boot
2258 S [KNL] Run init in single mode
2260 sa1100ir [NET]
2261 See drivers/net/irda/sa1100_ir.c.
2263 sbni= [NET] Granch SBNI12 leased line adapter
2265 sched_debug [KNL] Enables verbose scheduler debug messages.
2267 scsi_debug_*= [SCSI]
2268 See drivers/scsi/scsi_debug.c.
2270 scsi_default_dev_flags=
2271 [SCSI] SCSI default device flags
2272 Format: <integer>
2274 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2275 Format: <vendor>:<model>:<flags>
2276 (flags are integer value)
2278 scsi_logging_level= [SCSI] a bit mask of logging levels
2279 See drivers/scsi/scsi_logging.h for bits. Also
2280 settable via sysctl at dev.scsi.logging_level
2281 (/proc/sys/dev/scsi/logging_level).
2282 There is also a nice 'scsi_logging_level' script in the
2283 S390-tools package, available for download at
2284 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2286 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2287 discovered. async scans them in kernel threads,
2288 allowing boot to proceed. none ignores them, expecting
2289 user space to do the scan.
2291 security= [SECURITY] Choose a security module to enable at boot.
2292 If this boot parameter is not specified, only the first
2293 security module asking for security registration will be
2294 loaded. An invalid security module name will be treated
2295 as if no module has been chosen.
2297 selinux= [SELINUX] Disable or enable SELinux at boot time.
2298 Format: { "0" | "1" }
2299 See security/selinux/Kconfig help text.
2300 0 -- disable.
2301 1 -- enable.
2302 Default value is set via kernel config option.
2303 If enabled at boot time, /selinux/disable can be used
2304 later to disable prior to initial policy load.
2306 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2307 Format: { "0" | "1" }
2308 See security/apparmor/Kconfig help text
2309 0 -- disable.
2310 1 -- enable.
2311 Default value is set via kernel config option.
2313 serialnumber [BUGS=X86-32]
2315 shapers= [NET]
2316 Maximal number of shapers.
2318 show_msr= [x86] show boot-time MSR settings
2319 Format: { <integer> }
2320 Show boot-time (BIOS-initialized) MSR settings.
2321 The parameter means the number of CPUs to show,
2322 for example 1 means boot CPU only.
2324 sim710= [SCSI,HW]
2325 See header of drivers/scsi/sim710.c.
2327 simeth= [IA-64]
2328 simscsi=
2330 slram= [HW,MTD]
2332 slub_debug[=options[,slabs]] [MM, SLUB]
2333 Enabling slub_debug allows one to determine the
2334 culprit if slab objects become corrupted. Enabling
2335 slub_debug can create guard zones around objects and
2336 may poison objects when not in use. Also tracks the
2337 last alloc / free. For more information see
2338 Documentation/vm/slub.txt.
2340 slub_max_order= [MM, SLUB]
2341 Determines the maximum allowed order for slabs.
2342 A high setting may cause OOMs due to memory
2343 fragmentation. For more information see
2344 Documentation/vm/slub.txt.
2346 slub_min_objects= [MM, SLUB]
2347 The minimum number of objects per slab. SLUB will
2348 increase the slab order up to slub_max_order to
2349 generate a sufficiently large slab able to contain
2350 the number of objects indicated. The higher the number
2351 of objects the smaller the overhead of tracking slabs
2352 and the less frequently locks need to be acquired.
2353 For more information see Documentation/vm/slub.txt.
2355 slub_min_order= [MM, SLUB]
2356 Determines the mininum page order for slabs. Must be
2357 lower than slub_max_order.
2358 For more information see Documentation/vm/slub.txt.
2360 slub_nomerge [MM, SLUB]
2361 Disable merging of slabs with similar size. May be
2362 necessary if there is some reason to distinguish
2363 allocs to different slabs. Debug options disable
2364 merging on their own.
2365 For more information see Documentation/vm/slub.txt.
2367 smart2= [HW]
2368 Format: <io1>[,<io2>[,...,<io8>]]
2370 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2371 attempt to substitute SMP alternatives once at boot.
2373 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2374 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2375 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2376 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2377 smsc-ircc2.ircc_irq= [HW] IRQ line
2378 smsc-ircc2.ircc_dma= [HW] DMA channel
2379 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2380 0: Toshiba Satellite 1800 (GP data pin select)
2381 1: Fast pin select (default)
2382 2: ATC IRMode
2384 softlockup_panic=
2385 [KNL] Should the soft-lockup detector generate panics.
2387 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2388 See Documentation/sonypi.txt
2390 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2391 See Documentation/serial/specialix.txt.
2393 spia_io_base= [HW,MTD]
2394 spia_fio_base=
2395 spia_pedr=
2396 spia_peddr=
2398 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2399 See Documentation/scsi/st.txt.
2401 stacktrace [FTRACE]
2402 Enabled the stack tracer on boot up.
2404 sti= [PARISC,HW]
2405 Format: <num>
2406 Set the STI (builtin display/keyboard on the HP-PARISC
2407 machines) console (graphic card) which should be used
2408 as the initial boot-console.
2409 See also comment in drivers/video/console/sticore.c.
2411 sti_font= [HW]
2412 See comment in drivers/video/console/sticore.c.
2414 stifb= [HW]
2415 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2417 sunrpc.min_resvport=
2418 sunrpc.max_resvport=
2419 [NFS,SUNRPC]
2420 SunRPC servers often require that client requests
2421 originate from a privileged port (i.e. a port in the
2422 range 0 < portnr < 1024).
2423 An administrator who wishes to reserve some of these
2424 ports for other uses may adjust the range that the
2425 kernel's sunrpc client considers to be privileged
2426 using these two parameters to set the minimum and
2427 maximum port values.
2429 sunrpc.pool_mode=
2430 [NFS]
2431 Control how the NFS server code allocates CPUs to
2432 service thread pools. Depending on how many NICs
2433 you have and where their interrupts are bound, this
2434 option will affect which CPUs will do NFS serving.
2435 Note: this parameter cannot be changed while the
2436 NFS server is running.
2438 auto the server chooses an appropriate mode
2439 automatically using heuristics
2440 global a single global pool contains all CPUs
2441 percpu one pool for each CPU
2442 pernode one pool for each NUMA node (equivalent
2443 to global on non-NUMA machines)
2445 sunrpc.tcp_slot_table_entries=
2446 sunrpc.udp_slot_table_entries=
2447 [NFS,SUNRPC]
2448 Sets the upper limit on the number of simultaneous
2449 RPC calls that can be sent from the client to a
2450 server. Increasing these values may allow you to
2451 improve throughput, but will also increase the
2452 amount of memory reserved for use by the client.
2454 swiotlb= [IA-64] Number of I/O TLB slabs
2456 switches= [HW,M68k]
2458 sym53c416= [HW,SCSI]
2459 See header of drivers/scsi/sym53c416.c.
2461 sysrq_always_enabled
2462 [KNL]
2463 Ignore sysrq setting - this boot parameter will
2464 neutralize any effect of /proc/sys/kernel/sysrq.
2465 Useful for debugging.
2467 t128= [HW,SCSI]
2468 See header of drivers/scsi/t128.c.
2470 tdfx= [HW,DRM]
2472 test_suspend= [SUSPEND]
2473 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2474 standby suspend) as the system sleep state to briefly
2475 enter during system startup. The system is woken from
2476 this state using a wakeup-capable RTC alarm.
2478 thash_entries= [KNL,NET]
2479 Set number of hash buckets for TCP connection
2481 thermal.act= [HW,ACPI]
2482 -1: disable all active trip points in all thermal zones
2483 <degrees C>: override all lowest active trip points
2485 thermal.crt= [HW,ACPI]
2486 -1: disable all critical trip points in all thermal zones
2487 <degrees C>: override all critical trip points
2489 thermal.nocrt= [HW,ACPI]
2490 Set to disable actions on ACPI thermal zone
2491 critical and hot trip points.
2493 thermal.off= [HW,ACPI]
2494 1: disable ACPI thermal control
2496 thermal.psv= [HW,ACPI]
2497 -1: disable all passive trip points
2498 <degrees C>: override all passive trip points to this
2499 value
2501 thermal.tzp= [HW,ACPI]
2502 Specify global default ACPI thermal zone polling rate
2503 <deci-seconds>: poll all this frequency
2504 0: no polling (default)
2506 tmscsim= [HW,SCSI]
2507 See comment before function dc390_setup() in
2508 drivers/scsi/tmscsim.c.
2510 topology= [S390]
2511 Format: {off | on}
2512 Specify if the kernel should make use of the cpu
2513 topology informations if the hardware supports these.
2514 The scheduler will make use of these informations and
2515 e.g. base its process migration decisions on it.
2516 Default is off.
2518 tp720= [HW,PS2]
2520 tpm_suspend_pcr=[HW,TPM]
2521 Format: integer pcr id
2522 Specify that at suspend time, the tpm driver
2523 should extend the specified pcr with zeros,
2524 as a workaround for some chips which fail to
2525 flush the last written pcr on TPM_SaveState.
2526 This will guarantee that all the other pcrs
2527 are saved.
2529 trace_buf_size=nn[KMG]
2530 [FTRACE] will set tracing buffer size.
2532 trace_event=[event-list]
2533 [FTRACE] Set and start specified trace events in order
2534 to facilitate early boot debugging.
2535 See also Documentation/trace/events.txt
2537 tsc= Disable clocksource-must-verify flag for TSC.
2538 Format: <string>
2539 [x86] reliable: mark tsc clocksource as reliable, this
2540 disables clocksource verification at runtime.
2541 Used to enable high-resolution timer mode on older
2542 hardware, and in virtualized environment.
2544 turbografx.map[2|3]= [HW,JOY]
2545 TurboGraFX parallel port interface
2546 Format:
2547 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2548 See also Documentation/input/joystick-parport.txt
2550 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2551 See header of drivers/scsi/u14-34f.c.
2553 uhash_entries= [KNL,NET]
2554 Set number of hash buckets for UDP/UDP-Lite connections
2556 uhci-hcd.ignore_oc=
2557 [USB] Ignore overcurrent events (default N).
2558 Some badly-designed motherboards generate lots of
2559 bogus events, for ports that aren't wired to
2560 anything. Set this parameter to avoid log spamming.
2561 Note that genuine overcurrent events won't be
2562 reported either.
2564 unknown_nmi_panic
2565 [X86]
2566 Set unknown_nmi_panic=1 early on boot.
2568 usbcore.autosuspend=
2569 [USB] The autosuspend time delay (in seconds) used
2570 for newly-detected USB devices (default 2). This
2571 is the time required before an idle device will be
2572 autosuspended. Devices for which the delay is set
2573 to a negative value won't be autosuspended at all.
2575 usbcore.usbfs_snoop=
2576 [USB] Set to log all usbfs traffic (default 0 = off).
2578 usbcore.blinkenlights=
2579 [USB] Set to cycle leds on hubs (default 0 = off).
2581 usbcore.old_scheme_first=
2582 [USB] Start with the old device initialization
2583 scheme (default 0 = off).
2585 usbcore.use_both_schemes=
2586 [USB] Try the other device initialization scheme
2587 if the first one fails (default 1 = enabled).
2589 usbcore.initial_descriptor_timeout=
2590 [USB] Specifies timeout for the initial 64-byte
2591 USB_REQ_GET_DESCRIPTOR request in milliseconds
2592 (default 5000 = 5.0 seconds).
2594 usbhid.mousepoll=
2595 [USBHID] The interval which mice are to be polled at.
2597 usb-storage.delay_use=
2598 [UMS] The delay in seconds before a new device is
2599 scanned for Logical Units (default 5).
2601 usb-storage.quirks=
2602 [UMS] A list of quirks entries to supplement or
2603 override the built-in unusual_devs list. List
2604 entries are separated by commas. Each entry has
2605 the form VID:PID:Flags where VID and PID are Vendor
2606 and Product ID values (4-digit hex numbers) and
2607 Flags is a set of characters, each corresponding
2608 to a common usb-storage quirk flag as follows:
2609 a = SANE_SENSE (collect more than 18 bytes
2610 of sense data);
2611 b = BAD_SENSE (don't collect more than 18
2612 bytes of sense data);
2613 c = FIX_CAPACITY (decrease the reported
2614 device capacity by one sector);
2615 h = CAPACITY_HEURISTICS (decrease the
2616 reported device capacity by one
2617 sector if the number is odd);
2618 i = IGNORE_DEVICE (don't bind to this
2619 device);
2620 l = NOT_LOCKABLE (don't try to lock and
2621 unlock ejectable media);
2622 m = MAX_SECTORS_64 (don't transfer more
2623 than 64 sectors = 32 KB at a time);
2624 o = CAPACITY_OK (accept the capacity
2625 reported by the device);
2626 r = IGNORE_RESIDUE (the device reports
2627 bogus residue values);
2628 s = SINGLE_LUN (the device has only one
2629 Logical Unit);
2630 w = NO_WP_DETECT (don't test whether the
2631 medium is write-protected).
2632 Example: quirks=0419:aaf5:rl,0421:0433:rc
2634 userpte=
2635 [X86] Flags controlling user PTE allocations.
2637 nohigh = do not allocate PTE pages in
2638 HIGHMEM regardless of setting
2639 of CONFIG_HIGHPTE.
2641 vdso= [X86,SH]
2642 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2643 vdso=1: enable VDSO (default)
2644 vdso=0: disable VDSO mapping
2646 vdso32= [X86]
2647 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2648 vdso32=1: enable 32-bit VDSO (default)
2649 vdso32=0: disable 32-bit VDSO mapping
2651 vector= [IA-64,SMP]
2652 vector=percpu: enable percpu vector domain
2654 video= [FB] Frame buffer configuration
2655 See Documentation/fb/modedb.txt.
2657 vga= [BOOT,X86-32] Select a particular video mode
2658 See Documentation/x86/boot.txt and
2659 Documentation/svga.txt.
2660 Use vga=ask for menu.
2661 This is actually a boot loader parameter; the value is
2662 passed to the kernel using a special protocol.
2664 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2665 size of <nn>. This can be used to increase the
2666 minimum size (128MB on x86). It can also be used to
2667 decrease the size and leave more room for directly
2668 mapped kernel RAM.
2670 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2671 Format: <command>
2673 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2674 Format: <command>
2676 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2677 Format: <command>
2679 vt.cur_default= [VT] Default cursor shape.
2680 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2681 the parameters of the <Esc>[?A;B;Cc escape sequence;
2682 see VGA-softcursor.txt. Default: 2 = underline.
2684 vt.default_blu= [VT]
2685 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2686 Change the default blue palette of the console.
2687 This is a 16-member array composed of values
2688 ranging from 0-255.
2690 vt.default_grn= [VT]
2691 Format: <green0>,<green1>,<green2>,...,<green15>
2692 Change the default green palette of the console.
2693 This is a 16-member array composed of values
2694 ranging from 0-255.
2696 vt.default_red= [VT]
2697 Format: <red0>,<red1>,<red2>,...,<red15>
2698 Change the default red palette of the console.
2699 This is a 16-member array composed of values
2700 ranging from 0-255.
2702 vt.default_utf8=
2703 [VT]
2704 Format=<0|1>
2705 Set system-wide default UTF-8 mode for all tty's.
2706 Default is 1, i.e. UTF-8 mode is enabled for all
2707 newly opened terminals.
2709 vt.global_cursor_default=
2710 [VT]
2711 Format=<-1|0|1>
2712 Set system-wide default for whether a cursor
2713 is shown on new VTs. Default is -1,
2714 i.e. cursors will be created by default unless
2715 overridden by individual drivers. 0 will hide
2716 cursors, 1 will display them.
2718 wd33c93= [HW,SCSI]
2719 See header of drivers/scsi/wd33c93.c.
2721 wd7000= [HW,SCSI]
2722 See header of drivers/scsi/wd7000.c.
2724 watchdog timers [HW,WDT] For information on watchdog timers,
2725 see Documentation/watchdog/watchdog-parameters.txt
2726 or other driver-specific files in the
2727 Documentation/watchdog/ directory.
2729 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2730 default x2apic cluster mode on platforms
2731 supporting x2apic.
2733 x86_mrst_timer= [X86-32,APBT]
2734 Choose timer option for x86 Moorestown MID platform.
2735 Two valid options are apbt timer only and lapic timer
2736 plus one apbt timer for broadcast timer.
2737 x86_mrst_timer=apbt_only | lapic_and_apbt
2739 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2740 xd_geo= See header of drivers/block/xd.c.
2742 xen_emul_unplug= [HW,X86,XEN]
2743 Unplug Xen emulated devices
2744 Format: [unplug0,][unplug1]
2745 ide-disks -- unplug primary master IDE devices
2746 aux-ide-disks -- unplug non-primary-master IDE devices
2747 nics -- unplug network devices
2748 all -- unplug all emulated devices (NICs and IDE disks)
2749 ignore -- continue loading the Xen platform PCI driver even
2750 if the version check failed
2752 xirc2ps_cs= [NET,PCMCIA]
2753 Format:
2754 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2756 ______________________________________________________________________
2758 TODO:
2760 Add more DRM drivers.