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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 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
48 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
49 EFI EFI Partitioning (GPT) is enabled
50 EIDE EIDE/ATAPI support is enabled.
51 FB The frame buffer device is enabled.
52 GCOV GCOV profiling is enabled.
53 HW Appropriate hardware is enabled.
54 IA-64 IA-64 architecture is enabled.
55 IMA Integrity measurement architecture is enabled.
56 IOSCHED More than one I/O scheduler is enabled.
57 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
58 IPV6 IPv6 support is enabled.
59 ISAPNP ISA PnP code is enabled.
60 ISDN Appropriate ISDN support is enabled.
61 JOY Appropriate joystick support is enabled.
62 KGDB Kernel debugger support is enabled.
63 KVM Kernel Virtual Machine support is enabled.
64 LIBATA Libata driver is enabled
65 LP Printer support is enabled.
66 LOOP Loopback device support is enabled.
67 M68k M68k architecture is enabled.
68 These options have more detailed description inside of
69 Documentation/m68k/kernel-options.txt.
70 MCA MCA bus support is enabled.
71 MDA MDA console support is enabled.
72 MOUSE Appropriate mouse support is enabled.
73 MSI Message Signaled Interrupts (PCI).
74 MTD MTD (Memory Technology Device) support is enabled.
75 NET Appropriate network support is enabled.
76 NUMA NUMA support is enabled.
77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
79 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
81 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
83 PCIE PCI Express support is enabled.
84 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
92 A lot of drivers have their options described inside
93 the Documentation/scsi/ sub-directory.
94 SECURITY Different security models are enabled.
95 SELINUX SELinux support is enabled.
96 APPARMOR AppArmor support is enabled.
97 SERIAL Serial support is enabled.
98 SH SuperH architecture is enabled.
99 SMP The kernel is an SMP kernel.
100 SPARC Sparc architecture is enabled.
101 SWSUSP Software suspend (hibernation) is enabled.
102 SUSPEND System suspend states are enabled.
103 FTRACE Function tracing enabled.
104 TPM TPM drivers are enabled.
105 TS Appropriate touchscreen support is enabled.
106 UMS USB Mass Storage support is enabled.
107 USB USB support is enabled.
108 USBHID USB Human Interface Device support is enabled.
109 V4L Video For Linux support is enabled.
110 VGA The VGA console has been enabled.
111 VT Virtual terminal support is enabled.
112 WDT Watchdog support is enabled.
113 XT IBM PC/XT MFM hard disk support is enabled.
114 X86-32 X86-32, aka i386 architecture is enabled.
115 X86-64 X86-64 architecture is enabled.
116 More X86-64 boot options can be found in
117 Documentation/x86/x86_64/boot-options.txt .
118 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
119 XEN Xen support is enabled
121 In addition, the following text indicates that the option:
123 BUGS= Relates to possible processor bugs on the said processor.
124 KNL Is a kernel start-up parameter.
125 BOOT Is a boot loader parameter.
127 Parameters denoted with BOOT are actually interpreted by the boot
128 loader, and have no meaning to the kernel directly.
129 Do not modify the syntax of boot loader parameters without extreme
130 need or coordination with <Documentation/x86/boot.txt>.
132 There are also arch-specific kernel-parameters not documented here.
133 See for example <Documentation/x86/x86_64/boot-options.txt>.
135 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
136 a trailing = on the name of any parameter states that that parameter will
137 be entered as an environment variable, whereas its absence indicates that
138 it will appear as a kernel argument readable via /proc/cmdline by programs
139 running once the system is up.
141 The number of kernel parameters is not limited, but the length of the
142 complete command line (parameters including spaces etc.) is limited to
143 a fixed number of characters. This limit depends on the architecture
144 and is between 256 and 4096 characters. It is defined in the file
145 ./include/asm/setup.h as COMMAND_LINE_SIZE.
147 Finally, the [KMG] suffix is commonly described after a number of kernel
148 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
149 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
150 bytes respectively. Such letter suffixes can also be entirely omitted.
153 acpi= [HW,ACPI,X86]
154 Advanced Configuration and Power Interface
155 Format: { force | off | strict | noirq | rsdt }
156 force -- enable ACPI if default was off
157 off -- disable ACPI if default was on
158 noirq -- do not use ACPI for IRQ routing
159 strict -- Be less tolerant of platforms that are not
160 strictly ACPI specification compliant.
161 rsdt -- prefer RSDT over (default) XSDT
162 copy_dsdt -- copy DSDT to memory
164 See also Documentation/power/pm.txt, pci=noacpi
166 acpi_apic_instance= [ACPI, IOAPIC]
167 Format: <int>
168 2: use 2nd APIC table, if available
169 1,0: use 1st APIC table
170 default: 0
172 acpi_backlight= [HW,ACPI]
173 acpi_backlight=vendor
174 acpi_backlight=video
175 If set to vendor, prefer vendor specific driver
176 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
177 of the ACPI video.ko driver.
179 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
180 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
181 Format: <int>
182 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
183 debug output. Bits in debug_layer correspond to a
184 _COMPONENT in an ACPI source file, e.g.,
185 #define _COMPONENT ACPI_PCI_COMPONENT
186 Bits in debug_level correspond to a level in
187 ACPI_DEBUG_PRINT statements, e.g.,
188 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
189 The debug_level mask defaults to "info". See
190 Documentation/acpi/debug.txt for more information about
191 debug layers and levels.
193 Enable processor driver info messages:
194 acpi.debug_layer=0x20000000
195 Enable PCI/PCI interrupt routing info messages:
196 acpi.debug_layer=0x400000
197 Enable AML "Debug" output, i.e., stores to the Debug
198 object while interpreting AML:
199 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
200 Enable all messages related to ACPI hardware:
201 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
203 Some values produce so much output that the system is
204 unusable. The "log_buf_len" parameter may be useful
205 if you need to capture more output.
207 acpi_irq_balance [HW,ACPI]
208 ACPI will balance active IRQs
209 default in APIC mode
211 acpi_irq_nobalance [HW,ACPI]
212 ACPI will not move active IRQs (default)
213 default in PIC mode
215 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
216 Format: <irq>,<irq>...
218 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
219 use by PCI
220 Format: <irq>,<irq>...
222 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
224 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
225 Format: To spoof as Windows 98: ="Microsoft Windows"
227 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
228 acpi_osi="string1" # add string1 -- only one string
229 acpi_osi="!string2" # remove built-in string2
230 acpi_osi= # disable all strings
232 acpi_pm_good [X86]
233 Override the pmtimer bug detection: force the kernel
234 to assume that this machine's pmtimer latches its value
235 and always returns good values.
237 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
238 Format: { level | edge | high | low }
240 acpi_serialize [HW,ACPI] force serialization of AML methods
242 acpi_skip_timer_override [HW,ACPI]
243 Recognize and ignore IRQ0/pin2 Interrupt Override.
244 For broken nForce2 BIOS resulting in XT-PIC timer.
246 acpi_sleep= [HW,ACPI] Sleep options
247 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
248 old_ordering, nonvs, sci_force_enable }
249 See Documentation/power/video.txt for information on
250 s3_bios and s3_mode.
251 s3_beep is for debugging; it makes the PC's speaker beep
252 as soon as the kernel's real-mode entry point is called.
253 s4_nohwsig prevents ACPI hardware signature from being
254 used during resume from hibernation.
255 old_ordering causes the ACPI 1.0 ordering of the _PTS
256 control method, with respect to putting devices into
257 low power states, to be enforced (the ACPI 2.0 ordering
258 of _PTS is used by default).
259 nonvs prevents the kernel from saving/restoring the
260 ACPI NVS memory during suspend/hibernation and resume.
261 sci_force_enable causes the kernel to set SCI_EN directly
262 on resume from S1/S3 (which is against the ACPI spec,
263 but some broken systems don't work without it).
265 acpi_use_timer_override [HW,ACPI]
266 Use timer override. For some broken Nvidia NF5 boards
267 that require a timer override, but don't have HPET
269 acpi_enforce_resources= [ACPI]
270 { strict | lax | no }
271 Check for resource conflicts between native drivers
272 and ACPI OperationRegions (SystemIO and SystemMemory
273 only). IO ports and memory declared in ACPI might be
274 used by the ACPI subsystem in arbitrary AML code and
275 can interfere with legacy drivers.
276 strict (default): access to resources claimed by ACPI
277 is denied; legacy drivers trying to access reserved
278 resources will fail to bind to device using them.
279 lax: access to resources claimed by ACPI is allowed;
280 legacy drivers trying to access reserved resources
281 will bind successfully but a warning message is logged.
282 no: ACPI OperationRegions are not marked as reserved,
283 no further checks are performed.
285 add_efi_memmap [EFI; X86] Include EFI memory map in
286 kernel's map of available physical RAM.
288 agp= [AGP]
289 { off | try_unsupported }
290 off: disable AGP support
291 try_unsupported: try to drive unsupported chipsets
292 (may crash computer or cause data corruption)
294 ALSA [HW,ALSA]
295 See Documentation/sound/alsa/alsa-parameters.txt
297 alignment= [KNL,ARM]
298 Allow the default userspace alignment fault handler
299 behaviour to be specified. Bit 0 enables warnings,
300 bit 1 enables fixups, and bit 2 sends a segfault.
302 amd_iommu= [HW,X86-84]
303 Pass parameters to the AMD IOMMU driver in the system.
304 Possible values are:
305 fullflush - enable flushing of IO/TLB entries when
306 they are unmapped. Otherwise they are
307 flushed before they will be reused, which
308 is a lot of faster
309 off - do not initialize any AMD IOMMU found in
310 the system
312 amijoy.map= [HW,JOY] Amiga joystick support
313 Map of devices attached to JOY0DAT and JOY1DAT
314 Format: <a>,<b>
315 See also Documentation/kernel/input/joystick.txt
317 analog.map= [HW,JOY] Analog joystick and gamepad support
318 Specifies type or capabilities of an analog joystick
319 connected to one of 16 gameports
320 Format: <type1>,<type2>,..<type16>
322 apc= [HW,SPARC]
323 Power management functions (SPARCstation-4/5 + deriv.)
324 Format: noidle
325 Disable APC CPU standby support. SPARCstation-Fox does
326 not play well with APC CPU idle - disable it if you have
327 APC and your system crashes randomly.
329 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
330 Change the output verbosity whilst booting
331 Format: { quiet (default) | verbose | debug }
332 Change the amount of debugging information output
333 when initialising the APIC and IO-APIC components.
335 autoconf= [IPV6]
336 See Documentation/networking/ipv6.txt.
338 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
339 Limit apic dumping. The parameter defines the maximal
340 number of local apics being dumped. Also it is possible
341 to set it to "all" by meaning -- no limit here.
342 Format: { 1 (default) | 2 | ... | all }.
343 The parameter valid if only apic=debug or
344 apic=verbose is specified.
345 Example: apic=debug show_lapic=all
347 apm= [APM] Advanced Power Management
348 See header of arch/x86/kernel/apm_32.c.
350 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
351 Format: <io>,<irq>,<nodeID>
353 ataflop= [HW,M68k]
355 atarimouse= [HW,MOUSE] Atari Mouse
357 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
358 EzKey and similar keyboards
360 atkbd.reset= [HW] Reset keyboard during initialization
362 atkbd.set= [HW] Select keyboard code set
363 Format: <int> (2 = AT (default), 3 = PS/2)
365 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
366 keyboards
368 atkbd.softraw= [HW] Choose between synthetic and real raw mode
369 Format: <bool> (0 = real, 1 = synthetic (default))
371 atkbd.softrepeat= [HW]
372 Use software keyboard repeat
374 autotest [IA64]
376 baycom_epp= [HW,AX25]
377 Format: <io>,<mode>
379 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
380 Format: <io>,<mode>
381 See header of drivers/net/hamradio/baycom_par.c.
383 baycom_ser_fdx= [HW,AX25]
384 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
385 Format: <io>,<irq>,<mode>[,<baud>]
386 See header of drivers/net/hamradio/baycom_ser_fdx.c.
388 baycom_ser_hdx= [HW,AX25]
389 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
390 Format: <io>,<irq>,<mode>
391 See header of drivers/net/hamradio/baycom_ser_hdx.c.
393 boot_delay= Milliseconds to delay each printk during boot.
394 Values larger than 10 seconds (10000) are changed to
395 no delay (0).
396 Format: integer
398 bootmem_debug [KNL] Enable bootmem allocator debug messages.
400 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
401 bttv.radio= Most important insmod options are available as
402 kernel args too.
403 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
404 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
406 bulk_remove=off [PPC] This parameter disables the use of the pSeries
407 firmware feature for flushing multiple hpte entries
408 at a time.
410 c101= [NET] Moxa C101 synchronous serial card
412 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
413 Sometimes CPU hardware bugs make them report the cache
414 size incorrectly. The kernel will attempt work arounds
415 to fix known problems, but for some CPUs it is not
416 possible to determine what the correct size should be.
417 This option provides an override for these situations.
419 capability.disable=
420 [SECURITY] Disable capabilities. This would normally
421 be used only if an alternative security model is to be
422 configured. Potentially dangerous and should only be
423 used if you are entirely sure of the consequences.
425 ccw_timeout_log [S390]
426 See Documentation/s390/CommonIO for details.
428 cgroup_disable= [KNL] Disable a particular controller
429 Format: {name of the controller(s) to disable}
430 {Currently supported controllers - "memory"}
432 checkreqprot [SELINUX] Set initial checkreqprot flag value.
433 Format: { "0" | "1" }
434 See security/selinux/Kconfig help text.
435 0 -- check protection applied by kernel (includes
436 any implied execute protection).
437 1 -- check protection requested by application.
438 Default value is set via a kernel config option.
439 Value can be changed at runtime via
440 /selinux/checkreqprot.
442 cio_ignore= [S390]
443 See Documentation/s390/CommonIO for details.
445 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
446 [Deprecated]
447 Forces specified clocksource (if available) to be used
448 when calculating gettimeofday(). If specified
449 clocksource is not available, it defaults to PIT.
450 Format: { pit | tsc | cyclone | pmtmr }
452 clocksource= Override the default clocksource
453 Format: <string>
454 Override the default clocksource and use the clocksource
455 with the name specified.
456 Some clocksource names to choose from, depending on
457 the platform:
458 [all] jiffies (this is the base, fallback clocksource)
459 [ACPI] acpi_pm
460 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
461 pxa_timer,timer3,32k_counter,timer0_1
462 [AVR32] avr32
463 [X86-32] pit,hpet,tsc;
464 scx200_hrt on Geode; cyclone on IBM x440
465 [MIPS] MIPS
466 [PARISC] cr16
467 [S390] tod
468 [SH] SuperH
469 [SPARC64] tick
470 [X86-64] hpet,tsc
472 clearcpuid=BITNUM [X86]
473 Disable CPUID feature X for the kernel. See
474 arch/x86/include/asm/cpufeature.h for the valid bit
475 numbers. Note the Linux specific bits are not necessarily
476 stable over kernel options, but the vendor specific
477 ones should be.
478 Also note that user programs calling CPUID directly
479 or using the feature without checking anything
480 will still see it. This just prevents it from
481 being used by the kernel or shown in /proc/cpuinfo.
482 Also note the kernel might malfunction if you disable
483 some critical bits.
485 cmo_free_hint= [PPC] Format: { yes | no }
486 Specify whether pages are marked as being inactive
487 when they are freed. This is used in CMO environments
488 to determine OS memory pressure for page stealing by
489 a hypervisor.
490 Default: yes
492 code_bytes [X86] How many bytes of object code to print
493 in an oops report.
494 Range: 0 - 8192
495 Default: 64
497 com20020= [HW,NET] ARCnet - COM20020 chipset
498 Format:
499 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
501 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
502 Format: <io>[,<irq>]
504 com90xx= [HW,NET]
505 ARCnet - COM90xx chipset (memory-mapped buffers)
506 Format: <io>[,<irq>[,<memstart>]]
508 condev= [HW,S390] console device
509 conmode=
511 console= [KNL] Output console device and options.
513 tty<n> Use the virtual console device <n>.
515 ttyS<n>[,options]
516 ttyUSB0[,options]
517 Use the specified serial port. The options are of
518 the form "bbbbpnf", where "bbbb" is the baud rate,
519 "p" is parity ("n", "o", or "e"), "n" is number of
520 bits, and "f" is flow control ("r" for RTS or
521 omit it). Default is "9600n8".
523 See Documentation/serial-console.txt for more
524 information. See
525 Documentation/networking/netconsole.txt for an
526 alternative.
528 uart[8250],io,<addr>[,options]
529 uart[8250],mmio,<addr>[,options]
530 Start an early, polled-mode console on the 8250/16550
531 UART at the specified I/O port or MMIO address,
532 switching to the matching ttyS device later. The
533 options are the same as for ttyS, above.
535 If the device connected to the port is not a TTY but a braille
536 device, prepend "brl," before the device type, for instance
537 console=brl,ttyS0
538 For now, only VisioBraille is supported.
540 consoleblank= [KNL] The console blank (screen saver) timeout in
541 seconds. Defaults to 10*60 = 10mins. A value of 0
542 disables the blank timer.
544 coredump_filter=
545 [KNL] Change the default value for
546 /proc/<pid>/coredump_filter.
547 See also Documentation/filesystems/proc.txt.
549 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
550 Format:
551 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
553 crashkernel=size[KMG][@offset[KMG]]
554 [KNL] Using kexec, Linux can switch to a 'crash kernel'
555 upon panic. This parameter reserves the physical
556 memory region [offset, offset + size] for that kernel
557 image. If '@offset' is omitted, then a suitable offset
558 is selected automatically. Check
559 Documentation/kdump/kdump.txt for further details.
561 crashkernel=range1:size1[,range2:size2,...][@offset]
562 [KNL] Same as above, but depends on the memory
563 in the running system. The syntax of range is
564 start-[end] where start and end are both
565 a memory unit (amount[KMG]). See also
566 Documentation/kdump/kdump.txt for an example.
568 cs89x0_dma= [HW,NET]
569 Format: <dma>
571 cs89x0_media= [HW,NET]
572 Format: { rj45 | aui | bnc }
574 dasd= [HW,NET]
575 See header of drivers/s390/block/dasd_devmap.c.
577 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
578 (one device per port)
579 Format: <port#>,<type>
580 See also Documentation/input/joystick-parport.txt
582 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
583 time. See Documentation/dynamic-debug-howto.txt for
584 details.
586 debug [KNL] Enable kernel debugging (events log level).
588 debug_locks_verbose=
589 [KNL] verbose self-tests
590 Format=<0|1>
591 Print debugging info while doing the locking API
592 self-tests.
593 We default to 0 (no extra messages), setting it to
594 1 will print _a lot_ more information - normally
595 only useful to kernel developers.
597 debug_objects [KNL] Enable object debugging
599 no_debug_objects
600 [KNL] Disable object debugging
602 debugpat [X86] Enable PAT debugging
604 decnet.addr= [HW,NET]
605 Format: <area>[,<node>]
606 See also Documentation/networking/decnet.txt.
608 default_hugepagesz=
609 [same as hugepagesz=] The size of the default
610 HugeTLB page size. This is the size represented by
611 the legacy /proc/ hugepages APIs, used for SHM, and
612 default size when mounting hugetlbfs filesystems.
613 Defaults to the default architecture's huge page size
614 if not specified.
616 dhash_entries= [KNL]
617 Set number of hash buckets for dentry cache.
619 digi= [HW,SERIAL]
620 IO parameters + enable/disable command.
622 digiepca= [HW,SERIAL]
623 See drivers/char/README.epca and
624 Documentation/serial/digiepca.txt.
626 disable= [IPV6]
627 See Documentation/networking/ipv6.txt.
629 disable_ddw [PPC/PSERIES]
630 Disable Dynamic DMA Window support. Use this if
631 to workaround buggy firmware.
633 disable_ipv6= [IPV6]
634 See Documentation/networking/ipv6.txt.
636 disable_mtrr_cleanup [X86]
637 The kernel tries to adjust MTRR layout from continuous
638 to discrete, to make X server driver able to add WB
639 entry later. This parameter disables that.
641 disable_mtrr_trim [X86, Intel and AMD only]
642 By default the kernel will trim any uncacheable
643 memory out of your available memory pool based on
644 MTRR settings. This parameter disables that behavior,
645 possibly causing your machine to run very slowly.
647 disable_timer_pin_1 [X86]
648 Disable PIN 1 of APIC timer
649 Can be useful to work around chipset bugs.
651 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
652 this option disables the debugging code at boot.
654 dma_debug_entries=<number>
655 This option allows to tune the number of preallocated
656 entries for DMA-API debugging code. One entry is
657 required per DMA-API allocation. Use this if the
658 DMA-API debugging code disables itself because the
659 architectural default is too low.
661 dma_debug_driver=<driver_name>
662 With this option the DMA-API debugging driver
663 filter feature can be enabled at boot time. Just
664 pass the driver to filter for as the parameter.
665 The filter can be disabled or changed to another
666 driver later using sysfs.
668 dscc4.setup= [NET]
670 earlycon= [KNL] Output early console device and options.
671 uart[8250],io,<addr>[,options]
672 uart[8250],mmio,<addr>[,options]
673 uart[8250],mmio32,<addr>[,options]
674 Start an early, polled-mode console on the 8250/16550
675 UART at the specified I/O port or MMIO address.
676 MMIO inter-register address stride is either 8bit (mmio)
677 or 32bit (mmio32).
678 The options are the same as for ttyS, above.
680 earlyprintk= [X86,SH,BLACKFIN]
681 earlyprintk=vga
682 earlyprintk=serial[,ttySn[,baudrate]]
683 earlyprintk=ttySn[,baudrate]
684 earlyprintk=dbgp[debugController#]
686 Append ",keep" to not disable it when the real console
687 takes over.
689 Only vga or serial or usb debug port at a time.
691 Currently only ttyS0 and ttyS1 are supported.
693 Interaction with the standard serial driver is not
694 very good.
696 The VGA output is eventually overwritten by the real
697 console.
699 ekgdboc= [X86,KGDB] Allow early kernel console debugging
700 ekgdboc=kbd
702 This is designed to be used in conjunction with
703 the boot argument: earlyprintk=vga
705 edd= [EDD]
706 Format: {"off" | "on" | "skip[mbr]"}
708 eisa_irq_edge= [PARISC,HW]
709 See header of drivers/parisc/eisa.c.
711 elanfreq= [X86-32]
712 See comment before function elanfreq_setup() in
713 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
715 elevator= [IOSCHED]
716 Format: {"cfq" | "deadline" | "noop"}
717 See Documentation/block/as-iosched.txt and
718 Documentation/block/deadline-iosched.txt for details.
720 elfcorehdr= [IA64,PPC,SH,X86]
721 Specifies physical address of start of kernel core
722 image elf header. Generally kexec loader will
723 pass this option to capture kernel.
724 See Documentation/kdump/kdump.txt for details.
726 enable_mtrr_cleanup [X86]
727 The kernel tries to adjust MTRR layout from continuous
728 to discrete, to make X server driver able to add WB
729 entry later. This parameter enables that.
731 enable_timer_pin_1 [X86]
732 Enable PIN 1 of APIC timer
733 Can be useful to work around chipset bugs
734 (in particular on some ATI chipsets).
735 The kernel tries to set a reasonable default.
737 enforcing [SELINUX] Set initial enforcing status.
738 Format: {"0" | "1"}
739 See security/selinux/Kconfig help text.
740 0 -- permissive (log only, no denials).
741 1 -- enforcing (deny and log).
742 Default value is 0.
743 Value can be changed at runtime via /selinux/enforce.
745 erst_disable [ACPI]
746 Disable Error Record Serialization Table (ERST)
747 support.
749 ether= [HW,NET] Ethernet cards parameters
750 This option is obsoleted by the "netdev=" option, which
751 has equivalent usage. See its documentation for details.
753 failslab=
754 fail_page_alloc=
755 fail_make_request=[KNL]
756 General fault injection mechanism.
757 Format: <interval>,<probability>,<space>,<times>
758 See also /Documentation/fault-injection/.
760 floppy= [HW]
761 See Documentation/blockdev/floppy.txt.
763 force_pal_cache_flush
764 [IA-64] Avoid check_sal_cache_flush which may hang on
765 buggy SAL_CACHE_FLUSH implementations. Using this
766 parameter will force ia64_sal_cache_flush to call
767 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
769 ftrace=[tracer]
770 [FTRACE] will set and start the specified tracer
771 as early as possible in order to facilitate early
772 boot debugging.
774 ftrace_dump_on_oops[=orig_cpu]
775 [FTRACE] will dump the trace buffers on oops.
776 If no parameter is passed, ftrace will dump
777 buffers of all CPUs, but if you pass orig_cpu, it will
778 dump only the buffer of the CPU that triggered the
779 oops.
781 ftrace_filter=[function-list]
782 [FTRACE] Limit the functions traced by the function
783 tracer at boot up. function-list is a comma separated
784 list of functions. This list can be changed at run
785 time by the set_ftrace_filter file in the debugfs
786 tracing directory.
788 ftrace_notrace=[function-list]
789 [FTRACE] Do not trace the functions specified in
790 function-list. This list can be changed at run time
791 by the set_ftrace_notrace file in the debugfs
792 tracing directory.
794 ftrace_graph_filter=[function-list]
795 [FTRACE] Limit the top level callers functions traced
796 by the function graph tracer at boot up.
797 function-list is a comma separated list of functions
798 that can be changed at run time by the
799 set_graph_function file in the debugfs tracing directory.
801 gamecon.map[2|3]=
802 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
803 support via parallel port (up to 5 devices per port)
804 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
805 See also Documentation/input/joystick-parport.txt
807 gamma= [HW,DRM]
809 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
810 Format: off | on
811 default: on
813 gcov_persist= [GCOV] When non-zero (default), profiling data for
814 kernel modules is saved and remains accessible via
815 debugfs, even when the module is unloaded/reloaded.
816 When zero, profiling data is discarded and associated
817 debugfs files are removed at module unload time.
819 gpt [EFI] Forces disk with valid GPT signature but
820 invalid Protective MBR to be treated as GPT.
822 hashdist= [KNL,NUMA] Large hashes allocated during boot
823 are distributed across NUMA nodes. Defaults on
824 for 64bit NUMA, off otherwise.
825 Format: 0 | 1 (for off | on)
827 hcl= [IA-64] SGI's Hardware Graph compatibility layer
829 hd= [EIDE] (E)IDE hard drive subsystem geometry
830 Format: <cyl>,<head>,<sect>
832 hest_disable [ACPI]
833 Disable Hardware Error Source Table (HEST) support;
834 corresponding firmware-first mode error processing
835 logic will be disabled.
837 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
838 size of <nn>. This works even on boxes that have no
839 highmem otherwise. This also works to reduce highmem
840 size on bigger boxes.
842 highres= [KNL] Enable/disable high resolution timer mode.
843 Valid parameters: "on", "off"
844 Default: "on"
846 hisax= [HW,ISDN]
847 See Documentation/isdn/README.HiSax.
849 hlt [BUGS=ARM,SH]
851 hpet= [X86-32,HPET] option to control HPET usage
852 Format: { enable (default) | disable | force |
853 verbose }
854 disable: disable HPET and use PIT instead
855 force: allow force enabled of undocumented chips (ICH4,
856 VIA, nVidia)
857 verbose: show contents of HPET registers during setup
859 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
860 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
861 On x86-64 and powerpc, this option can be specified
862 multiple times interleaved with hugepages= to reserve
863 huge pages of different sizes. Valid pages sizes on
864 x86-64 are 2M (when the CPU supports "pse") and 1G
865 (when the CPU supports the "pdpe1gb" cpuinfo flag)
866 Note that 1GB pages can only be allocated at boot time
867 using hugepages= and not freed afterwards.
869 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
870 terminal devices. Valid values: 0..8
871 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
872 If specified, z/VM IUCV HVC accepts connections
873 from listed z/VM user IDs only.
875 keep_bootcon [KNL]
876 Do not unregister boot console at start. This is only
877 useful for debugging when something happens in the window
878 between unregistering the boot console and initializing
879 the real console.
881 i2c_bus= [HW] Override the default board specific I2C bus speed
882 or register an additional I2C bus that is not
883 registered from board initialization code.
884 Format:
885 <bus_id>,<clkrate>
887 i8042.debug [HW] Toggle i8042 debug mode
888 i8042.direct [HW] Put keyboard port into non-translated mode
889 i8042.dumbkbd [HW] Pretend that controller can only read data from
890 keyboard and cannot control its state
891 (Don't attempt to blink the leds)
892 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
893 i8042.nokbd [HW] Don't check/create keyboard port
894 i8042.noloop [HW] Disable the AUX Loopback command while probing
895 for the AUX port
896 i8042.nomux [HW] Don't check presence of an active multiplexing
897 controller
898 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
899 controllers
900 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
901 i8042.reset [HW] Reset the controller during init and cleanup
902 i8042.unlock [HW] Unlock (ignore) the keylock
904 i810= [HW,DRM]
906 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
907 indicates that the driver is running on unsupported
908 hardware.
909 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
910 does not match list of supported models.
911 i8k.power_status
912 [HW] Report power status in /proc/i8k
913 (disabled by default)
914 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
915 capability is set.
917 icn= [HW,ISDN]
918 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
920 ide-core.nodma= [HW] (E)IDE subsystem
921 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
922 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
923 .cdrom .chs .ignore_cable are additional options
924 See Documentation/ide/ide.txt.
926 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
927 Claim all unknown PCI IDE storage controllers.
929 idle= [X86]
930 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
931 Poll forces a polling idle loop that can slightly
932 improve the performance of waking up a idle CPU, but
933 will use a lot of power and make the system run hot.
934 Not recommended.
935 idle=mwait: On systems which support MONITOR/MWAIT but
936 the kernel chose to not use it because it doesn't save
937 as much power as a normal idle loop, use the
938 MONITOR/MWAIT idle loop anyways. Performance should be
939 the same as idle=poll.
940 idle=halt: Halt is forced to be used for CPU idle.
941 In such case C2/C3 won't be used again.
942 idle=nomwait: Disable mwait for CPU C-states
944 ignore_loglevel [KNL]
945 Ignore loglevel setting - this will print /all/
946 kernel messages to the console. Useful for debugging.
948 ihash_entries= [KNL]
949 Set number of hash buckets for inode cache.
951 ima_audit= [IMA]
952 Format: { "0" | "1" }
953 0 -- integrity auditing messages. (Default)
954 1 -- enable informational integrity auditing messages.
956 ima_hash= [IMA]
957 Format: { "sha1" | "md5" }
958 default: "sha1"
960 ima_tcb [IMA]
961 Load a policy which meets the needs of the Trusted
962 Computing Base. This means IMA will measure all
963 programs exec'd, files mmap'd for exec, and all files
964 opened for read by uid=0.
966 init= [KNL]
967 Format: <full_path>
968 Run specified binary instead of /sbin/init as init
969 process.
971 initcall_debug [KNL] Trace initcalls as they are executed. Useful
972 for working out where the kernel is dying during
973 startup.
975 initrd= [BOOT] Specify the location of the initial ramdisk
977 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
978 Format: <irq>
980 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
981 on
982 Enable intel iommu driver.
983 off
984 Disable intel iommu driver.
985 igfx_off [Default Off]
986 By default, gfx is mapped as normal device. If a gfx
987 device has a dedicated DMAR unit, the DMAR unit is
988 bypassed by not enabling DMAR with this option. In
989 this case, gfx device will use physical address for
990 DMA.
991 forcedac [x86_64]
992 With this option iommu will not optimize to look
993 for io virtual address below 32 bit forcing dual
994 address cycle on pci bus for cards supporting greater
995 than 32 bit addressing. The default is to look
996 for translation below 32 bit and if not available
997 then look in the higher range.
998 strict [Default Off]
999 With this option on every unmap_single operation will
1000 result in a hardware IOTLB flush operation as opposed
1001 to batching them for performance.
1002 sp_off [Default Off]
1003 By default, super page will be supported if Intel IOMMU
1004 has the capability. With this option, super page will
1005 not be supported.
1006 intremap= [X86-64, Intel-IOMMU]
1007 Format: { on (default) | off | nosid }
1008 on enable Interrupt Remapping (default)
1009 off disable Interrupt Remapping
1010 nosid disable Source ID checking
1012 inttest= [IA64]
1014 iomem= Disable strict checking of access to MMIO memory
1015 strict regions from userspace.
1016 relaxed
1018 iommu= [x86]
1019 off
1020 force
1021 noforce
1022 biomerge
1023 panic
1024 nopanic
1025 merge
1026 nomerge
1027 forcesac
1028 soft
1029 pt [x86, IA64]
1031 io7= [HW] IO7 for Marvel based alpha systems
1032 See comment before marvel_specify_io7 in
1033 arch/alpha/kernel/core_marvel.c.
1035 io_delay= [X86] I/O delay method
1036 0x80
1037 Standard port 0x80 based delay
1038 0xed
1039 Alternate port 0xed based delay (needed on some systems)
1040 udelay
1041 Simple two microseconds delay
1042 none
1043 No delay
1045 ip= [IP_PNP]
1046 See Documentation/filesystems/nfs/nfsroot.txt.
1048 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1049 See comment before ip2_setup() in
1050 drivers/char/ip2/ip2base.c.
1052 irqfixup [HW]
1053 When an interrupt is not handled search all handlers
1054 for it. Intended to get systems with badly broken
1055 firmware running.
1057 irqpoll [HW]
1058 When an interrupt is not handled search all handlers
1059 for it. Also check all handlers each timer
1060 interrupt. Intended to get systems with badly broken
1061 firmware running.
1063 isapnp= [ISAPNP]
1064 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1066 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1067 Format:
1068 <cpu number>,...,<cpu number>
1069 or
1070 <cpu number>-<cpu number>
1071 (must be a positive range in ascending order)
1072 or a mixture
1073 <cpu number>,...,<cpu number>-<cpu number>
1075 This option can be used to specify one or more CPUs
1076 to isolate from the general SMP balancing and scheduling
1077 algorithms. You can move a process onto or off an
1078 "isolated" CPU via the CPU affinity syscalls or cpuset.
1079 <cpu number> begins at 0 and the maximum value is
1080 "number of CPUs in system - 1".
1082 This option is the preferred way to isolate CPUs. The
1083 alternative -- manually setting the CPU mask of all
1084 tasks in the system -- can cause problems and
1085 suboptimal load balancer performance.
1087 iucv= [HW,NET]
1089 js= [HW,JOY] Analog joystick
1090 See Documentation/input/joystick.txt.
1092 keepinitrd [HW,ARM]
1094 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1095 specifies the amount of memory usable by the kernel
1096 for non-movable allocations. The requested amount is
1097 spread evenly throughout all nodes in the system. The
1098 remaining memory in each node is used for Movable
1099 pages. In the event, a node is too small to have both
1100 kernelcore and Movable pages, kernelcore pages will
1101 take priority and other nodes will have a larger number
1102 of kernelcore pages. The Movable zone is used for the
1103 allocation of pages that may be reclaimed or moved
1104 by the page migration subsystem. This means that
1105 HugeTLB pages may not be allocated from this zone.
1106 Note that allocations like PTEs-from-HighMem still
1107 use the HighMem zone if it exists, and the Normal
1108 zone if it does not.
1110 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1111 Format: <Controller#>[,poll interval]
1112 The controller # is the number of the ehci usb debug
1113 port as it is probed via PCI. The poll interval is
1114 optional and is the number seconds in between
1115 each poll cycle to the debug port in case you need
1116 the functionality for interrupting the kernel with
1117 gdb or control-c on the dbgp connection. When
1118 not using this parameter you use sysrq-g to break into
1119 the kernel debugger.
1121 kgdboc= [KGDB,HW] kgdb over consoles.
1122 Requires a tty driver that supports console polling,
1123 or a supported polling keyboard driver (non-usb).
1124 Serial only format: <serial_device>[,baud]
1125 keyboard only format: kbd
1126 keyboard and serial format: kbd,<serial_device>[,baud]
1127 Optional Kernel mode setting:
1128 kms, kbd format: kms,kbd
1129 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1131 kgdbwait [KGDB] Stop kernel execution and enter the
1132 kernel debugger at the earliest opportunity.
1134 kmac= [MIPS] korina ethernet MAC address.
1135 Configure the RouterBoard 532 series on-chip
1136 Ethernet adapter MAC address.
1138 kmemleak= [KNL] Boot-time kmemleak enable/disable
1139 Valid arguments: on, off
1140 Default: on
1142 kstack=N [X86] Print N words from the kernel stack
1143 in oops dumps.
1145 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1146 Default is 0 (don't ignore, but inject #GP)
1148 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1149 Default is 1 (enabled)
1151 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1152 KVM MMU at runtime.
1153 Default is 0 (off)
1155 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1156 Default is 1 (enabled)
1158 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1159 for all guests.
1160 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1162 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1163 (virtualized MMU) support on capable Intel chips.
1164 Default is 1 (enabled)
1166 kvm-intel.emulate_invalid_guest_state=
1167 [KVM,Intel] Enable emulation of invalid guest states
1168 Default is 0 (disabled)
1170 kvm-intel.flexpriority=
1171 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1172 Default is 1 (enabled)
1174 kvm-intel.unrestricted_guest=
1175 [KVM,Intel] Disable unrestricted guest feature
1176 (virtualized real and unpaged mode) on capable
1177 Intel chips. Default is 1 (enabled)
1179 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1180 feature (tagged TLBs) on capable Intel chips.
1181 Default is 1 (enabled)
1183 l2cr= [PPC]
1185 l3cr= [PPC]
1187 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1188 disabled it.
1190 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1191 in C2 power state.
1193 libata.dma= [LIBATA] DMA control
1194 libata.dma=0 Disable all PATA and SATA DMA
1195 libata.dma=1 PATA and SATA Disk DMA only
1196 libata.dma=2 ATAPI (CDROM) DMA only
1197 libata.dma=4 Compact Flash DMA only
1198 Combinations also work, so libata.dma=3 enables DMA
1199 for disks and CDROMs, but not CFs.
1201 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1202 libata.ignore_hpa=0 keep BIOS limits (default)
1203 libata.ignore_hpa=1 ignore limits, using full disk
1205 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1206 when set.
1207 Format: <int>
1209 libata.force= [LIBATA] Force configurations. The format is comma
1210 separated list of "[ID:]VAL" where ID is
1211 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1212 matching port, link or device. Basically, it matches
1213 the ATA ID string printed on console by libata. If
1214 the whole ID part is omitted, the last PORT and DEVICE
1215 values are used. If ID hasn't been specified yet, the
1216 configuration applies to all ports, links and devices.
1218 If only DEVICE is omitted, the parameter applies to
1219 the port and all links and devices behind it. DEVICE
1220 number of 0 either selects the first device or the
1221 first fan-out link behind PMP device. It does not
1222 select the host link. DEVICE number of 15 selects the
1223 host link and device attached to it.
1225 The VAL specifies the configuration to force. As long
1226 as there's no ambiguity shortcut notation is allowed.
1227 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1228 The following configurations can be forced.
1230 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1231 Any ID with matching PORT is used.
1233 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1235 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1236 udma[/][16,25,33,44,66,100,133] notation is also
1237 allowed.
1239 * [no]ncq: Turn on or off NCQ.
1241 * nohrst, nosrst, norst: suppress hard, soft
1242 and both resets.
1244 * dump_id: dump IDENTIFY data.
1246 If there are multiple matching configurations changing
1247 the same attribute, the last one is used.
1249 memblock=debug [KNL] Enable memblock debug messages.
1251 load_ramdisk= [RAM] List of ramdisks to load from floppy
1252 See Documentation/blockdev/ramdisk.txt.
1254 lockd.nlm_grace_period=P [NFS] Assign grace period.
1255 Format: <integer>
1257 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1258 Format: <integer>
1260 lockd.nlm_timeout=T [NFS] Assign timeout value.
1261 Format: <integer>
1263 lockd.nlm_udpport=M [NFS] Assign UDP port.
1264 Format: <integer>
1266 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1267 Format: <irq>
1269 loglevel= All Kernel Messages with a loglevel smaller than the
1270 console loglevel will be printed to the console. It can
1271 also be changed with klogd or other programs. The
1272 loglevels are defined as follows:
1274 0 (KERN_EMERG) system is unusable
1275 1 (KERN_ALERT) action must be taken immediately
1276 2 (KERN_CRIT) critical conditions
1277 3 (KERN_ERR) error conditions
1278 4 (KERN_WARNING) warning conditions
1279 5 (KERN_NOTICE) normal but significant condition
1280 6 (KERN_INFO) informational
1281 7 (KERN_DEBUG) debug-level messages
1283 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1284 in bytes. n must be a power of two. The default
1285 size is set in the kernel config file.
1287 logo.nologo [FB] Disables display of the built-in Linux logo.
1288 This may be used to provide more screen space for
1289 kernel log messages and is useful when debugging
1290 kernel boot problems.
1292 lp=0 [LP] Specify parallel ports to use, e.g,
1293 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1294 lp=reset first parallel port). 'lp=0' disables the
1295 lp=auto printer driver. 'lp=reset' (which can be
1296 specified in addition to the ports) causes
1297 attached printers to be reset. Using
1298 lp=port1,port2,... specifies the parallel ports
1299 to associate lp devices with, starting with
1300 lp0. A port specification may be 'none' to skip
1301 that lp device, or a parport name such as
1302 'parport0'. Specifying 'lp=auto' instead of a
1303 port specification list means that device IDs
1304 from each port should be examined, to see if
1305 an IEEE 1284-compliant printer is attached; if
1306 so, the driver will manage that printer.
1307 See also header of drivers/char/lp.c.
1309 lpj=n [KNL]
1310 Sets loops_per_jiffy to given constant, thus avoiding
1311 time-consuming boot-time autodetection (up to 250 ms per
1312 CPU). 0 enables autodetection (default). To determine
1313 the correct value for your kernel, boot with normal
1314 autodetection and see what value is printed. Note that
1315 on SMP systems the preset will be applied to all CPUs,
1316 which is likely to cause problems if your CPUs need
1317 significantly divergent settings. An incorrect value
1318 will cause delays in the kernel to be wrong, leading to
1319 unpredictable I/O errors and other breakage. Although
1320 unlikely, in the extreme case this might damage your
1321 hardware.
1323 ltpc= [NET]
1324 Format: <io>,<irq>,<dma>
1326 machvec= [IA64] Force the use of a particular machine-vector
1327 (machvec) in a generic kernel.
1328 Example: machvec=hpzx1_swiotlb
1330 machtype= [Loongson] Share the same kernel image file between different
1331 yeeloong laptop.
1332 Example: machtype=lemote-yeeloong-2f-7inch
1334 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1335 than or equal to this physical address is ignored.
1337 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1338 should make use of. maxcpus=n : n >= 0 limits the
1339 kernel to using 'n' processors. n=0 is a special case,
1340 it is equivalent to "nosmp", which also disables
1341 the IO APIC.
1343 max_loop= [LOOP] Maximum number of loopback devices that can
1344 be mounted
1345 Format: <1-256>
1347 mcatest= [IA-64]
1349 mce [X86-32] Machine Check Exception
1351 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1353 md= [HW] RAID subsystems devices and level
1354 See Documentation/md.txt.
1356 mdacon= [MDA]
1357 Format: <first>,<last>
1358 Specifies range of consoles to be captured by the MDA.
1360 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1361 Amount of memory to be used when the kernel is not able
1362 to see the whole system memory or for test.
1363 [X86-32] Use together with memmap= to avoid physical
1364 address space collisions. Without memmap= PCI devices
1365 could be placed at addresses belonging to unused RAM.
1367 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1368 memory.
1370 memchunk=nn[KMG]
1371 [KNL,SH] Allow user to override the default size for
1372 per-device physically contiguous DMA buffers.
1374 memmap=exactmap [KNL,X86] Enable setting of an exact
1375 E820 memory map, as specified by the user.
1376 Such memmap=exactmap lines can be constructed based on
1377 BIOS output or other requirements. See the memmap=nn@ss
1378 option description.
1380 memmap=nn[KMG]@ss[KMG]
1381 [KNL] Force usage of a specific region of memory
1382 Region of memory to be used, from ss to ss+nn.
1384 memmap=nn[KMG]#ss[KMG]
1385 [KNL,ACPI] Mark specific memory as ACPI data.
1386 Region of memory to be used, from ss to ss+nn.
1388 memmap=nn[KMG]$ss[KMG]
1389 [KNL,ACPI] Mark specific memory as reserved.
1390 Region of memory to be used, from ss to ss+nn.
1391 Example: Exclude memory from 0x18690000-0x1869ffff
1392 memmap=64K$0x18690000
1393 or
1394 memmap=0x10000$0x18690000
1396 memory_corruption_check=0/1 [X86]
1397 Some BIOSes seem to corrupt the first 64k of
1398 memory when doing things like suspend/resume.
1399 Setting this option will scan the memory
1400 looking for corruption. Enabling this will
1401 both detect corruption and prevent the kernel
1402 from using the memory being corrupted.
1403 However, its intended as a diagnostic tool; if
1404 repeatable BIOS-originated corruption always
1405 affects the same memory, you can use memmap=
1406 to prevent the kernel from using that memory.
1408 memory_corruption_check_size=size [X86]
1409 By default it checks for corruption in the low
1410 64k, making this memory unavailable for normal
1411 use. Use this parameter to scan for
1412 corruption in more or less memory.
1414 memory_corruption_check_period=seconds [X86]
1415 By default it checks for corruption every 60
1416 seconds. Use this parameter to check at some
1417 other rate. 0 disables periodic checking.
1419 memtest= [KNL,X86] Enable memtest
1420 Format: <integer>
1421 default : 0 <disable>
1422 Specifies the number of memtest passes to be
1423 performed. Each pass selects another test
1424 pattern from a given set of patterns. Memtest
1425 fills the memory with this pattern, validates
1426 memory contents and reserves bad memory
1427 regions that are detected.
1429 meye.*= [HW] Set MotionEye Camera parameters
1430 See Documentation/video4linux/meye.txt.
1432 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1433 Multi-Function General Purpose Timers on AMD Geode
1434 platforms.
1436 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1437 the BIOS has incorrectly applied a workaround. TinyBIOS
1438 version 0.98 is known to be affected, 0.99 fixes the
1439 problem by letting the user disable the workaround.
1441 mga= [HW,DRM]
1443 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1444 physical address is ignored.
1446 mini2440= [ARM,HW,KNL]
1447 Format:[0..2][b][c][t]
1448 Default: "0tb"
1449 MINI2440 configuration specification:
1450 0 - The attached screen is the 3.5" TFT
1451 1 - The attached screen is the 7" TFT
1452 2 - The VGA Shield is attached (1024x768)
1453 Leaving out the screen size parameter will not load
1454 the TFT driver, and the framebuffer will be left
1455 unconfigured.
1456 b - Enable backlight. The TFT backlight pin will be
1457 linked to the kernel VESA blanking code and a GPIO
1458 LED. This parameter is not necessary when using the
1459 VGA shield.
1460 c - Enable the s3c camera interface.
1461 t - Reserved for enabling touchscreen support. The
1462 touchscreen support is not enabled in the mainstream
1463 kernel as of 2.6.30, a preliminary port can be found
1464 in the "bleeding edge" mini2440 support kernel at
1465 http://repo.or.cz/w/linux-2.6/mini2440.git
1467 mminit_loglevel=
1468 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1469 parameter allows control of the logging verbosity for
1470 the additional memory initialisation checks. A value
1471 of 0 disables mminit logging and a level of 4 will
1472 log everything. Information is printed at KERN_DEBUG
1473 so loglevel=8 may also need to be specified.
1475 mousedev.tap_time=
1476 [MOUSE] Maximum time between finger touching and
1477 leaving touchpad surface for touch to be considered
1478 a tap and be reported as a left button click (for
1479 touchpads working in absolute mode only).
1480 Format: <msecs>
1481 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1482 reporting absolute coordinates, such as tablets
1483 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1484 reporting absolute coordinates, such as tablets
1486 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1487 is similar to kernelcore except it specifies the
1488 amount of memory used for migratable allocations.
1489 If both kernelcore and movablecore is specified,
1490 then kernelcore will be at *least* the specified
1491 value but may be more. If movablecore on its own
1492 is specified, the administrator must be careful
1493 that the amount of memory usable for all allocations
1494 is not too small.
1496 MTD_Partition= [MTD]
1497 Format: <name>,<region-number>,<size>,<offset>
1499 MTD_Region= [MTD] Format:
1500 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1502 mtdparts= [MTD]
1503 See drivers/mtd/cmdlinepart.c.
1505 multitce=off [PPC] This parameter disables the use of the pSeries
1506 firmware feature for updating multiple TCE entries
1507 at a time.
1509 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1511 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1513 boundary - index of last SLC block on Flex-OneNAND.
1514 The remaining blocks are configured as MLC blocks.
1515 lock - Configure if Flex-OneNAND boundary should be locked.
1516 Once locked, the boundary cannot be changed.
1517 1 indicates lock status, 0 indicates unlock status.
1519 mtdset= [ARM]
1520 ARM/S3C2412 JIVE boot control
1522 See arch/arm/mach-s3c2412/mach-jive.c
1524 mtouchusb.raw_coordinates=
1525 [HW] Make the MicroTouch USB driver use raw coordinates
1526 ('y', default) or cooked coordinates ('n')
1528 mtrr_chunk_size=nn[KMG] [X86]
1529 used for mtrr cleanup. It is largest continuous chunk
1530 that could hold holes aka. UC entries.
1532 mtrr_gran_size=nn[KMG] [X86]
1533 Used for mtrr cleanup. It is granularity of mtrr block.
1534 Default is 1.
1535 Large value could prevent small alignment from
1536 using up MTRRs.
1538 mtrr_spare_reg_nr=n [X86]
1539 Format: <integer>
1540 Range: 0,7 : spare reg number
1541 Default : 1
1542 Used for mtrr cleanup. It is spare mtrr entries number.
1543 Set to 2 or more if your graphical card needs more.
1545 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1547 netdev= [NET] Network devices parameters
1548 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1549 Note that mem_start is often overloaded to mean
1550 something different and driver-specific.
1551 This usage is only documented in each driver source
1552 file if at all.
1554 nf_conntrack.acct=
1555 [NETFILTER] Enable connection tracking flow accounting
1556 0 to disable accounting
1557 1 to enable accounting
1558 Default value is 0.
1560 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1561 See Documentation/filesystems/nfs/nfsroot.txt.
1563 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1564 See Documentation/filesystems/nfs/nfsroot.txt.
1566 nfsrootdebug [NFS] enable nfsroot debugging messages.
1567 See Documentation/filesystems/nfs/nfsroot.txt.
1569 nfs.callback_tcpport=
1570 [NFS] set the TCP port on which the NFSv4 callback
1571 channel should listen.
1573 nfs.cache_getent=
1574 [NFS] sets the pathname to the program which is used
1575 to update the NFS client cache entries.
1577 nfs.cache_getent_timeout=
1578 [NFS] sets the timeout after which an attempt to
1579 update a cache entry is deemed to have failed.
1581 nfs.idmap_cache_timeout=
1582 [NFS] set the maximum lifetime for idmapper cache
1583 entries.
1585 nfs.enable_ino64=
1586 [NFS] enable 64-bit inode numbers.
1587 If zero, the NFS client will fake up a 32-bit inode
1588 number for the readdir() and stat() syscalls instead
1589 of returning the full 64-bit number.
1590 The default is to return 64-bit inode numbers.
1592 nfs.nfs4_disable_idmapping=
1593 [NFSv4] When set, this option disables the NFSv4
1594 idmapper on the client, but only if the mount
1595 is using the 'sec=sys' security flavour. This may
1596 make migration from legacy NFSv2/v3 systems easier
1597 provided that the server has the appropriate support.
1598 The default is to always enable NFSv4 idmapping.
1600 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1601 when a NMI is triggered.
1602 Format: [state][,regs][,debounce][,die]
1604 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1605 Format: [panic,][nopanic,][num]
1606 Valid num: 0
1607 0 - turn nmi_watchdog off
1608 When panic is specified, panic when an NMI watchdog
1609 timeout occurs (or 'nopanic' to override the opposite
1610 default).
1611 This is useful when you use a panic=... timeout and
1612 need the box quickly up again.
1614 netpoll.carrier_timeout=
1615 [NET] Specifies amount of time (in seconds) that
1616 netpoll should wait for a carrier. By default netpoll
1617 waits 4 seconds.
1619 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1620 emulation library even if a 387 maths coprocessor
1621 is present.
1623 no_console_suspend
1624 [HW] Never suspend the console
1625 Disable suspending of consoles during suspend and
1626 hibernate operations. Once disabled, debugging
1627 messages can reach various consoles while the rest
1628 of the system is being put to sleep (ie, while
1629 debugging driver suspend/resume hooks). This may
1630 not work reliably with all consoles, but is known
1631 to work with serial and VGA consoles.
1633 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1634 caches in the slab allocator. Saves per-node memory,
1635 but will impact performance.
1637 noalign [KNL,ARM]
1639 noapic [SMP,APIC] Tells the kernel to not make use of any
1640 IOAPICs that may be present in the system.
1642 noautogroup Disable scheduler automatic task group creation.
1644 nobats [PPC] Do not use BATs for mapping kernel lowmem
1645 on "Classic" PPC cores.
1647 nocache [ARM]
1649 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1651 nodelayacct [KNL] Disable per-task delay accounting
1653 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1655 nodsp [SH] Disable hardware DSP at boot time.
1657 noefi [X86] Disable EFI runtime services support.
1659 noexec [IA-64]
1661 noexec [X86]
1662 On X86-32 available only on PAE configured kernels.
1663 noexec=on: enable non-executable mappings (default)
1664 noexec=off: disable non-executable mappings
1666 nosmep [X86]
1667 Disable SMEP (Supervisor Mode Execution Protection)
1668 even if it is supported by processor.
1670 noexec32 [X86-64]
1671 This affects only 32-bit executables.
1672 noexec32=on: enable non-executable mappings (default)
1673 read doesn't imply executable mappings
1674 noexec32=off: disable non-executable mappings
1675 read implies executable mappings
1677 nofpu [SH] Disable hardware FPU at boot time.
1679 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1680 register save and restore. The kernel will only save
1681 legacy floating-point registers on task switch.
1683 noxsave [BUGS=X86] Disables x86 extended register state save
1684 and restore using xsave. The kernel will fallback to
1685 enabling legacy floating-point and sse state.
1687 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1688 wfi(ARM) instruction doesn't work correctly and not to
1689 use it. This is also useful when using JTAG debugger.
1691 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1692 instruction doesn't work correctly and not to
1693 use it.
1695 no_file_caps Tells the kernel not to honor file capabilities. The
1696 only way then for a file to be executed with privilege
1697 is to be setuid root or executed by root.
1699 nohalt [IA-64] Tells the kernel not to use the power saving
1700 function PAL_HALT_LIGHT when idle. This increases
1701 power-consumption. On the positive side, it reduces
1702 interrupt wake-up latency, which may improve performance
1703 in certain environments such as networked servers or
1704 real-time systems.
1706 nohz= [KNL] Boottime enable/disable dynamic ticks
1707 Valid arguments: on, off
1708 Default: on
1710 noiotrap [SH] Disables trapped I/O port accesses.
1712 noirqdebug [X86-32] Disables the code which attempts to detect and
1713 disable unhandled interrupt sources.
1715 no_timer_check [X86,APIC] Disables the code which tests for
1716 broken timer IRQ sources.
1718 noisapnp [ISAPNP] Disables ISA PnP code.
1720 noinitrd [RAM] Tells the kernel not to load any configured
1721 initial RAM disk.
1723 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1724 remapping.
1725 [Deprecated - use intremap=off]
1727 nointroute [IA-64]
1729 nojitter [IA64] Disables jitter checking for ITC timers.
1731 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1733 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1734 fault handling.
1736 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
1737 steal time is computed, but won't influence scheduler
1738 behaviour
1740 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1742 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1744 noltlbs [PPC] Do not use large page/tlb entries for kernel
1745 lowmem mapping on PPC40x.
1747 nomca [IA-64] Disable machine check abort handling
1749 nomce [X86-32] Machine Check Exception
1751 nomfgpt [X86-32] Disable Multi-Function General Purpose
1752 Timer usage (for AMD Geode machines).
1754 nopat [X86] Disable PAT (page attribute table extension of
1755 pagetables) support.
1757 norandmaps Don't use address space randomization. Equivalent to
1758 echo 0 > /proc/sys/kernel/randomize_va_space
1760 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1762 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1763 with UP alternatives
1765 noresidual [PPC] Don't use residual data on PReP machines.
1767 noresume [SWSUSP] Disables resume and restores original swap
1768 space.
1770 no-scroll [VGA] Disables scrollback.
1771 This is required for the Braillex ib80-piezo Braille
1772 reader made by F.H. Papenmeier (Germany).
1774 nosbagart [IA-64]
1776 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1778 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1779 and disable the IO APIC. legacy for "maxcpus=0".
1781 nosoftlockup [KNL] Disable the soft-lockup detector.
1783 nosync [HW,M68K] Disables sync negotiation for all devices.
1785 notsc [BUGS=X86-32] Disable Time Stamp Counter
1787 nousb [USB] Disable the USB subsystem
1789 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1791 nowb [ARM]
1793 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1795 nptcg= [IA64] Override max number of concurrent global TLB
1796 purges which is reported from either PAL_VM_SUMMARY or
1797 SAL PALO.
1799 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1800 could support. nr_cpus=n : n >= 1 limits the kernel to
1801 supporting 'n' processors. Later in runtime you can not
1802 use hotplug cpu feature to put more cpu back to online.
1803 just like you compile the kernel NR_CPUS=n
1805 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1807 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1808 one of ['zone', 'node', 'default'] can be specified
1809 This can be set from sysctl after boot.
1810 See Documentation/sysctl/vm.txt for details.
1812 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1813 See Documentation/debugging-via-ohci1394.txt for more
1814 info.
1816 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1817 Rather than timing out after 20 ms if an EC
1818 command is not properly ACKed, override the length
1819 of the timeout. We have interrupts disabled while
1820 waiting for the ACK, so if this is set too high
1821 interrupts *may* be lost!
1823 omap_mux= [OMAP] Override bootloader pin multiplexing.
1824 Format: <mux_mode0.mode_name=value>...
1825 For example, to override I2C bus2:
1826 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1828 oprofile.timer= [HW]
1829 Use timer interrupt instead of performance counters
1831 oprofile.cpu_type= Force an oprofile cpu type
1832 This might be useful if you have an older oprofile
1833 userland or if you want common events.
1834 Format: { arch_perfmon }
1835 arch_perfmon: [X86] Force use of architectural
1836 perfmon on Intel CPUs instead of the
1837 CPU specific event set.
1839 oops=panic Always panic on oopses. Default is to just kill the
1840 process, but there is a small probability of
1841 deadlocking the machine.
1842 This will also cause panics on machine check exceptions.
1843 Useful together with panic=30 to trigger a reboot.
1845 OSS [HW,OSS]
1846 See Documentation/sound/oss/oss-parameters.txt
1848 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1849 timeout > 0: seconds before rebooting
1850 timeout = 0: wait forever
1851 timeout < 0: reboot immediately
1852 Format: <timeout>
1854 parkbd.port= [HW] Parallel port number the keyboard adapter is
1855 connected to, default is 0.
1856 Format: <parport#>
1857 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1858 0 for XT, 1 for AT (default is AT).
1859 Format: <mode>
1861 parport= [HW,PPT] Specify parallel ports. 0 disables.
1862 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1863 Use 'auto' to force the driver to use any
1864 IRQ/DMA settings detected (the default is to
1865 ignore detected IRQ/DMA settings because of
1866 possible conflicts). You can specify the base
1867 address, IRQ, and DMA settings; IRQ and DMA
1868 should be numbers, or 'auto' (for using detected
1869 settings on that particular port), or 'nofifo'
1870 (to avoid using a FIFO even if it is detected).
1871 Parallel ports are assigned in the order they
1872 are specified on the command line, starting
1873 with parport0.
1875 parport_init_mode= [HW,PPT]
1876 Configure VIA parallel port to operate in
1877 a specific mode. This is necessary on Pegasos
1878 computer where firmware has no options for setting
1879 up parallel port mode and sets it to spp.
1880 Currently this function knows 686a and 8231 chips.
1881 Format: [spp|ps2|epp|ecp|ecpepp]
1883 pause_on_oops=
1884 Halt all CPUs after the first oops has been printed for
1885 the specified number of seconds. This is to be used if
1886 your oopses keep scrolling off the screen.
1888 pcbit= [HW,ISDN]
1890 pcd. [PARIDE]
1891 See header of drivers/block/paride/pcd.c.
1892 See also Documentation/blockdev/paride.txt.
1894 pci=option[,option...] [PCI] various PCI subsystem options:
1895 earlydump [X86] dump PCI config space before the kernel
1896 changes anything
1897 off [X86] don't probe for the PCI bus
1898 bios [X86-32] force use of PCI BIOS, don't access
1899 the hardware directly. Use this if your machine
1900 has a non-standard PCI host bridge.
1901 nobios [X86-32] disallow use of PCI BIOS, only direct
1902 hardware access methods are allowed. Use this
1903 if you experience crashes upon bootup and you
1904 suspect they are caused by the BIOS.
1905 conf1 [X86] Force use of PCI Configuration
1906 Mechanism 1.
1907 conf2 [X86] Force use of PCI Configuration
1908 Mechanism 2.
1909 noaer [PCIE] If the PCIEAER kernel config parameter is
1910 enabled, this kernel boot option can be used to
1911 disable the use of PCIE advanced error reporting.
1912 nodomains [PCI] Disable support for multiple PCI
1913 root domains (aka PCI segments, in ACPI-speak).
1914 nommconf [X86] Disable use of MMCONFIG for PCI
1915 Configuration
1916 check_enable_amd_mmconf [X86] check for and enable
1917 properly configured MMIO access to PCI
1918 config space on AMD family 10h CPU
1919 nomsi [MSI] If the PCI_MSI kernel config parameter is
1920 enabled, this kernel boot option can be used to
1921 disable the use of MSI interrupts system-wide.
1922 noioapicquirk [APIC] Disable all boot interrupt quirks.
1923 Safety option to keep boot IRQs enabled. This
1924 should never be necessary.
1925 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1926 primary IO-APIC for bridges that cannot disable
1927 boot IRQs. This fixes a source of spurious IRQs
1928 when the system masks IRQs.
1929 noioapicreroute [APIC] Disable workaround that uses the
1930 boot IRQ equivalent of an IRQ that connects to
1931 a chipset where boot IRQs cannot be disabled.
1932 The opposite of ioapicreroute.
1933 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1934 routing table. These calls are known to be buggy
1935 on several machines and they hang the machine
1936 when used, but on other computers it's the only
1937 way to get the interrupt routing table. Try
1938 this option if the kernel is unable to allocate
1939 IRQs or discover secondary PCI buses on your
1940 motherboard.
1941 rom [X86] Assign address space to expansion ROMs.
1942 Use with caution as certain devices share
1943 address decoders between ROMs and other
1944 resources.
1945 norom [X86] Do not assign address space to
1946 expansion ROMs that do not already have
1947 BIOS assigned address ranges.
1948 nobar [X86] Do not assign address space to the
1949 BARs that weren't assigned by the BIOS.
1950 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1951 assigned automatically to PCI devices. You can
1952 make the kernel exclude IRQs of your ISA cards
1953 this way.
1954 pirqaddr=0xAAAAA [X86] Specify the physical address
1955 of the PIRQ table (normally generated
1956 by the BIOS) if it is outside the
1957 F0000h-100000h range.
1958 lastbus=N [X86] Scan all buses thru bus #N. Can be
1959 useful if the kernel is unable to find your
1960 secondary buses and you want to tell it
1961 explicitly which ones they are.
1962 assign-busses [X86] Always assign all PCI bus
1963 numbers ourselves, overriding
1964 whatever the firmware may have done.
1965 usepirqmask [X86] Honor the possible IRQ mask stored
1966 in the BIOS $PIR table. This is needed on
1967 some systems with broken BIOSes, notably
1968 some HP Pavilion N5400 and Omnibook XE3
1969 notebooks. This will have no effect if ACPI
1970 IRQ routing is enabled.
1971 noacpi [X86] Do not use ACPI for IRQ routing
1972 or for PCI scanning.
1973 use_crs [X86] Use PCI host bridge window information
1974 from ACPI. On BIOSes from 2008 or later, this
1975 is enabled by default. If you need to use this,
1976 please report a bug.
1977 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1978 If you need to use this, please report a bug.
1979 routeirq Do IRQ routing for all PCI devices.
1980 This is normally done in pci_enable_device(),
1981 so this option is a temporary workaround
1982 for broken drivers that don't call it.
1983 skip_isa_align [X86] do not align io start addr, so can
1984 handle more pci cards
1985 firmware [ARM] Do not re-enumerate the bus but instead
1986 just use the configuration from the
1987 bootloader. This is currently used on
1988 IXP2000 systems where the bus has to be
1989 configured a certain way for adjunct CPUs.
1990 noearly [X86] Don't do any early type 1 scanning.
1991 This might help on some broken boards which
1992 machine check when some devices' config space
1993 is read. But various workarounds are disabled
1994 and some IOMMU drivers will not work.
1995 bfsort Sort PCI devices into breadth-first order.
1996 This sorting is done to get a device
1997 order compatible with older (<= 2.4) kernels.
1998 nobfsort Don't sort PCI devices into breadth-first order.
1999 cbiosize=nn[KMG] The fixed amount of bus space which is
2000 reserved for the CardBus bridge's IO window.
2001 The default value is 256 bytes.
2002 cbmemsize=nn[KMG] The fixed amount of bus space which is
2003 reserved for the CardBus bridge's memory
2004 window. The default value is 64 megabytes.
2005 resource_alignment=
2006 Format:
2007 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2008 Specifies alignment and device to reassign
2009 aligned memory resources.
2010 If <order of align> is not specified,
2011 PAGE_SIZE is used as alignment.
2012 PCI-PCI bridge can be specified, if resource
2013 windows need to be expanded.
2014 ecrc= Enable/disable PCIe ECRC (transaction layer
2015 end-to-end CRC checking).
2016 bios: Use BIOS/firmware settings. This is the
2017 the default.
2018 off: Turn ECRC off
2019 on: Turn ECRC on.
2020 realloc reallocate PCI resources if allocations done by BIOS
2021 are erroneous.
2023 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2024 Management.
2025 off Disable ASPM.
2026 force Enable ASPM even on devices that claim not to support it.
2027 WARNING: Forcing ASPM on may cause system lockups.
2029 pcie_ports= [PCIE] PCIe ports handling:
2030 auto Ask the BIOS whether or not to use native PCIe services
2031 associated with PCIe ports (PME, hot-plug, AER). Use
2032 them only if that is allowed by the BIOS.
2033 native Use native PCIe services associated with PCIe ports
2034 unconditionally.
2035 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2036 ports driver.
2038 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2039 nomsi Do not use MSI for native PCIe PME signaling (this makes
2040 all PCIe root ports use INTx for all services).
2042 pcmv= [HW,PCMCIA] BadgePAD 4
2044 pd. [PARIDE]
2045 See Documentation/blockdev/paride.txt.
2047 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2048 boot time.
2049 Format: { 0 | 1 }
2050 See arch/parisc/kernel/pdc_chassis.c
2052 percpu_alloc= Select which percpu first chunk allocator to use.
2053 Currently supported values are "embed" and "page".
2054 Archs may support subset or none of the selections.
2055 See comments in mm/percpu.c for details on each
2056 allocator. This parameter is primarily for debugging
2057 and performance comparison.
2059 pf. [PARIDE]
2060 See Documentation/blockdev/paride.txt.
2062 pg. [PARIDE]
2063 See Documentation/blockdev/paride.txt.
2065 pirq= [SMP,APIC] Manual mp-table setup
2066 See Documentation/x86/i386/IO-APIC.txt.
2068 plip= [PPT,NET] Parallel port network link
2069 Format: { parport<nr> | timid | 0 }
2070 See also Documentation/parport.txt.
2072 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2073 Override pmtimer IOPort with a hex value.
2074 e.g. pmtmr=0x508
2076 pnp.debug [PNP]
2077 Enable PNP debug messages. This depends on the
2078 CONFIG_PNP_DEBUG_MESSAGES option.
2080 pnpacpi= [ACPI]
2081 { off }
2083 pnpbios= [ISAPNP]
2084 { on | off | curr | res | no-curr | no-res }
2086 pnp_reserve_irq=
2087 [ISAPNP] Exclude IRQs for the autoconfiguration
2089 pnp_reserve_dma=
2090 [ISAPNP] Exclude DMAs for the autoconfiguration
2092 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2093 Ranges are in pairs (I/O port base and size).
2095 pnp_reserve_mem=
2096 [ISAPNP] Exclude memory regions for the
2097 autoconfiguration.
2098 Ranges are in pairs (memory base and size).
2100 ports= [IP_VS_FTP] IPVS ftp helper module
2101 Default is 21.
2102 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2103 may be specified.
2104 Format: <port>,<port>....
2106 print-fatal-signals=
2107 [KNL] debug: print fatal signals
2109 If enabled, warn about various signal handling
2110 related application anomalies: too many signals,
2111 too many POSIX.1 timers, fatal signals causing a
2112 coredump - etc.
2114 If you hit the warning due to signal overflow,
2115 you might want to try "ulimit -i unlimited".
2117 default: off.
2119 printk.time= Show timing data prefixed to each printk message line
2120 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2122 processor.max_cstate= [HW,ACPI]
2123 Limit processor to maximum C-state
2124 max_cstate=9 overrides any DMI blacklist limit.
2126 processor.nocst [HW,ACPI]
2127 Ignore the _CST method to determine C-states,
2128 instead using the legacy FADT method
2130 profile= [KNL] Enable kernel profiling via /proc/profile
2131 Format: [schedule,]<number>
2132 Param: "schedule" - profile schedule points.
2133 Param: <number> - step/bucket size as a power of 2 for
2134 statistical time based profiling.
2135 Param: "sleep" - profile D-state sleeping (millisecs).
2136 Requires CONFIG_SCHEDSTATS
2137 Param: "kvm" - profile VM exits.
2139 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2140 before loading.
2141 See Documentation/blockdev/ramdisk.txt.
2143 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2144 probe for; one of (bare|imps|exps|lifebook|any).
2145 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2146 per second.
2147 psmouse.resetafter= [HW,MOUSE]
2148 Try to reset the device after so many bad packets
2149 (0 = never).
2150 psmouse.resolution=
2151 [HW,MOUSE] Set desired mouse resolution, in dpi.
2152 psmouse.smartscroll=
2153 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2154 0 = disabled, 1 = enabled (default).
2156 pt. [PARIDE]
2157 See Documentation/blockdev/paride.txt.
2159 pty.legacy_count=
2160 [KNL] Number of legacy pty's. Overwrites compiled-in
2161 default number.
2163 quiet [KNL] Disable most log messages
2165 r128= [HW,DRM]
2167 raid= [HW,RAID]
2168 See Documentation/md.txt.
2170 ramdisk_blocksize= [RAM]
2171 See Documentation/blockdev/ramdisk.txt.
2173 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2174 See Documentation/blockdev/ramdisk.txt.
2176 rcupdate.blimit= [KNL,BOOT]
2177 Set maximum number of finished RCU callbacks to process
2178 in one batch.
2180 rcupdate.qhimark= [KNL,BOOT]
2181 Set threshold of queued
2182 RCU callbacks over which batch limiting is disabled.
2184 rcupdate.qlowmark= [KNL,BOOT]
2185 Set threshold of queued RCU callbacks below which
2186 batch limiting is re-enabled.
2188 rdinit= [KNL]
2189 Format: <full_path>
2190 Run specified binary instead of /init from the ramdisk,
2191 used for early userspace startup. See initrd.
2193 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2194 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2195 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2197 relax_domain_level=
2198 [KNL, SMP] Set scheduler's default relax_domain_level.
2199 See Documentation/cgroups/cpusets.txt.
2201 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2203 reservetop= [X86-32]
2204 Format: nn[KMG]
2205 Reserves a hole at the top of the kernel virtual
2206 address space.
2208 reservelow= [X86]
2209 Format: nn[K]
2210 Set the amount of memory to reserve for BIOS at
2211 the bottom of the address space.
2213 reset_devices [KNL] Force drivers to reset the underlying device
2214 during initialization.
2216 resume= [SWSUSP]
2217 Specify the partition device for software suspend
2219 resume_offset= [SWSUSP]
2220 Specify the offset from the beginning of the partition
2221 given by "resume=" at which the swap header is located,
2222 in <PAGE_SIZE> units (needed only for swap files).
2223 See Documentation/power/swsusp-and-swap-files.txt
2225 hibernate= [HIBERNATION]
2226 noresume Don't check if there's a hibernation image
2227 present during boot.
2228 nocompress Don't compress/decompress hibernation images.
2230 retain_initrd [RAM] Keep initrd memory after extraction
2232 rhash_entries= [KNL,NET]
2233 Set number of hash buckets for route cache
2235 riscom8= [HW,SERIAL]
2236 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2238 ro [KNL] Mount root device read-only on boot
2240 root= [KNL] Root filesystem
2242 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2243 mount the root filesystem
2245 rootflags= [KNL] Set root filesystem mount option string
2247 rootfstype= [KNL] Set root filesystem type
2249 rootwait [KNL] Wait (indefinitely) for root device to show up.
2250 Useful for devices that are detected asynchronously
2251 (e.g. USB and MMC devices).
2253 rw [KNL] Mount root device read-write on boot
2255 S [KNL] Run init in single mode
2257 sa1100ir [NET]
2258 See drivers/net/irda/sa1100_ir.c.
2260 sbni= [NET] Granch SBNI12 leased line adapter
2262 sched_debug [KNL] Enables verbose scheduler debug messages.
2264 security= [SECURITY] Choose a security module to enable at boot.
2265 If this boot parameter is not specified, only the first
2266 security module asking for security registration will be
2267 loaded. An invalid security module name will be treated
2268 as if no module has been chosen.
2270 selinux= [SELINUX] Disable or enable SELinux at boot time.
2271 Format: { "0" | "1" }
2272 See security/selinux/Kconfig help text.
2273 0 -- disable.
2274 1 -- enable.
2275 Default value is set via kernel config option.
2276 If enabled at boot time, /selinux/disable can be used
2277 later to disable prior to initial policy load.
2279 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2280 Format: { "0" | "1" }
2281 See security/apparmor/Kconfig help text
2282 0 -- disable.
2283 1 -- enable.
2284 Default value is set via kernel config option.
2286 serialnumber [BUGS=X86-32]
2288 shapers= [NET]
2289 Maximal number of shapers.
2291 show_msr= [x86] show boot-time MSR settings
2292 Format: { <integer> }
2293 Show boot-time (BIOS-initialized) MSR settings.
2294 The parameter means the number of CPUs to show,
2295 for example 1 means boot CPU only.
2297 simeth= [IA-64]
2298 simscsi=
2300 slram= [HW,MTD]
2302 slub_debug[=options[,slabs]] [MM, SLUB]
2303 Enabling slub_debug allows one to determine the
2304 culprit if slab objects become corrupted. Enabling
2305 slub_debug can create guard zones around objects and
2306 may poison objects when not in use. Also tracks the
2307 last alloc / free. For more information see
2308 Documentation/vm/slub.txt.
2310 slub_max_order= [MM, SLUB]
2311 Determines the maximum allowed order for slabs.
2312 A high setting may cause OOMs due to memory
2313 fragmentation. For more information see
2314 Documentation/vm/slub.txt.
2316 slub_min_objects= [MM, SLUB]
2317 The minimum number of objects per slab. SLUB will
2318 increase the slab order up to slub_max_order to
2319 generate a sufficiently large slab able to contain
2320 the number of objects indicated. The higher the number
2321 of objects the smaller the overhead of tracking slabs
2322 and the less frequently locks need to be acquired.
2323 For more information see Documentation/vm/slub.txt.
2325 slub_min_order= [MM, SLUB]
2326 Determines the mininum page order for slabs. Must be
2327 lower than slub_max_order.
2328 For more information see Documentation/vm/slub.txt.
2330 slub_nomerge [MM, SLUB]
2331 Disable merging of slabs with similar size. May be
2332 necessary if there is some reason to distinguish
2333 allocs to different slabs. Debug options disable
2334 merging on their own.
2335 For more information see Documentation/vm/slub.txt.
2337 smart2= [HW]
2338 Format: <io1>[,<io2>[,...,<io8>]]
2340 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2341 attempt to substitute SMP alternatives once at boot.
2343 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2344 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2345 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2346 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2347 smsc-ircc2.ircc_irq= [HW] IRQ line
2348 smsc-ircc2.ircc_dma= [HW] DMA channel
2349 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2350 0: Toshiba Satellite 1800 (GP data pin select)
2351 1: Fast pin select (default)
2352 2: ATC IRMode
2354 softlockup_panic=
2355 [KNL] Should the soft-lockup detector generate panics.
2356 Format: <integer>
2358 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2359 See Documentation/sonypi.txt
2361 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2362 See Documentation/serial/specialix.txt.
2364 spia_io_base= [HW,MTD]
2365 spia_fio_base=
2366 spia_pedr=
2367 spia_peddr=
2369 stacktrace [FTRACE]
2370 Enabled the stack tracer on boot up.
2372 sti= [PARISC,HW]
2373 Format: <num>
2374 Set the STI (builtin display/keyboard on the HP-PARISC
2375 machines) console (graphic card) which should be used
2376 as the initial boot-console.
2377 See also comment in drivers/video/console/sticore.c.
2379 sti_font= [HW]
2380 See comment in drivers/video/console/sticore.c.
2382 stifb= [HW]
2383 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2385 sunrpc.min_resvport=
2386 sunrpc.max_resvport=
2387 [NFS,SUNRPC]
2388 SunRPC servers often require that client requests
2389 originate from a privileged port (i.e. a port in the
2390 range 0 < portnr < 1024).
2391 An administrator who wishes to reserve some of these
2392 ports for other uses may adjust the range that the
2393 kernel's sunrpc client considers to be privileged
2394 using these two parameters to set the minimum and
2395 maximum port values.
2397 sunrpc.pool_mode=
2398 [NFS]
2399 Control how the NFS server code allocates CPUs to
2400 service thread pools. Depending on how many NICs
2401 you have and where their interrupts are bound, this
2402 option will affect which CPUs will do NFS serving.
2403 Note: this parameter cannot be changed while the
2404 NFS server is running.
2406 auto the server chooses an appropriate mode
2407 automatically using heuristics
2408 global a single global pool contains all CPUs
2409 percpu one pool for each CPU
2410 pernode one pool for each NUMA node (equivalent
2411 to global on non-NUMA machines)
2413 sunrpc.tcp_slot_table_entries=
2414 sunrpc.udp_slot_table_entries=
2415 [NFS,SUNRPC]
2416 Sets the upper limit on the number of simultaneous
2417 RPC calls that can be sent from the client to a
2418 server. Increasing these values may allow you to
2419 improve throughput, but will also increase the
2420 amount of memory reserved for use by the client.
2422 swapaccount[=0|1]
2423 [KNL] Enable accounting of swap in memory resource
2424 controller if no parameter or 1 is given or disable
2425 it if 0 is given (See Documentation/cgroups/memory.txt)
2427 swiotlb= [IA-64] Number of I/O TLB slabs
2429 switches= [HW,M68k]
2431 sysfs.deprecated=0|1 [KNL]
2432 Enable/disable old style sysfs layout for old udev
2433 on older distributions. When this option is enabled
2434 very new udev will not work anymore. When this option
2435 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2436 in older udev will not work anymore.
2437 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2438 the kernel configuration.
2440 sysrq_always_enabled
2441 [KNL]
2442 Ignore sysrq setting - this boot parameter will
2443 neutralize any effect of /proc/sys/kernel/sysrq.
2444 Useful for debugging.
2446 tdfx= [HW,DRM]
2448 test_suspend= [SUSPEND]
2449 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2450 standby suspend) as the system sleep state to briefly
2451 enter during system startup. The system is woken from
2452 this state using a wakeup-capable RTC alarm.
2454 thash_entries= [KNL,NET]
2455 Set number of hash buckets for TCP connection
2457 thermal.act= [HW,ACPI]
2458 -1: disable all active trip points in all thermal zones
2459 <degrees C>: override all lowest active trip points
2461 thermal.crt= [HW,ACPI]
2462 -1: disable all critical trip points in all thermal zones
2463 <degrees C>: override all critical trip points
2465 thermal.nocrt= [HW,ACPI]
2466 Set to disable actions on ACPI thermal zone
2467 critical and hot trip points.
2469 thermal.off= [HW,ACPI]
2470 1: disable ACPI thermal control
2472 thermal.psv= [HW,ACPI]
2473 -1: disable all passive trip points
2474 <degrees C>: override all passive trip points to this
2475 value
2477 thermal.tzp= [HW,ACPI]
2478 Specify global default ACPI thermal zone polling rate
2479 <deci-seconds>: poll all this frequency
2480 0: no polling (default)
2482 threadirqs [KNL]
2483 Force threading of all interrupt handlers except those
2484 marked explicitely IRQF_NO_THREAD.
2486 topology= [S390]
2487 Format: {off | on}
2488 Specify if the kernel should make use of the cpu
2489 topology information if the hardware supports this.
2490 The scheduler will make use of this information and
2491 e.g. base its process migration decisions on it.
2492 Default is on.
2494 tp720= [HW,PS2]
2496 tpm_suspend_pcr=[HW,TPM]
2497 Format: integer pcr id
2498 Specify that at suspend time, the tpm driver
2499 should extend the specified pcr with zeros,
2500 as a workaround for some chips which fail to
2501 flush the last written pcr on TPM_SaveState.
2502 This will guarantee that all the other pcrs
2503 are saved.
2505 trace_buf_size=nn[KMG]
2506 [FTRACE] will set tracing buffer size.
2508 trace_event=[event-list]
2509 [FTRACE] Set and start specified trace events in order
2510 to facilitate early boot debugging.
2511 See also Documentation/trace/events.txt
2513 tsc= Disable clocksource stability checks for TSC.
2514 Format: <string>
2515 [x86] reliable: mark tsc clocksource as reliable, this
2516 disables clocksource verification at runtime, as well
2517 as the stability checks done at bootup. Used to enable
2518 high-resolution timer mode on older hardware, and in
2519 virtualized environment.
2520 [x86] noirqtime: Do not use TSC to do irq accounting.
2521 Used to run time disable IRQ_TIME_ACCOUNTING on any
2522 platforms where RDTSC is slow and this accounting
2523 can add overhead.
2525 turbografx.map[2|3]= [HW,JOY]
2526 TurboGraFX parallel port interface
2527 Format:
2528 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2529 See also Documentation/input/joystick-parport.txt
2531 udbg-immortal [PPC] When debugging early kernel crashes that
2532 happen after console_init() and before a proper
2533 console driver takes over, this boot options might
2534 help "seeing" what's going on.
2536 uhash_entries= [KNL,NET]
2537 Set number of hash buckets for UDP/UDP-Lite connections
2539 uhci-hcd.ignore_oc=
2540 [USB] Ignore overcurrent events (default N).
2541 Some badly-designed motherboards generate lots of
2542 bogus events, for ports that aren't wired to
2543 anything. Set this parameter to avoid log spamming.
2544 Note that genuine overcurrent events won't be
2545 reported either.
2547 unknown_nmi_panic
2548 [X86] Cause panic on unknown NMI.
2550 usbcore.authorized_default=
2551 [USB] Default USB device authorization:
2552 (default -1 = authorized except for wireless USB,
2553 0 = not authorized, 1 = authorized)
2555 usbcore.autosuspend=
2556 [USB] The autosuspend time delay (in seconds) used
2557 for newly-detected USB devices (default 2). This
2558 is the time required before an idle device will be
2559 autosuspended. Devices for which the delay is set
2560 to a negative value won't be autosuspended at all.
2562 usbcore.usbfs_snoop=
2563 [USB] Set to log all usbfs traffic (default 0 = off).
2565 usbcore.blinkenlights=
2566 [USB] Set to cycle leds on hubs (default 0 = off).
2568 usbcore.old_scheme_first=
2569 [USB] Start with the old device initialization
2570 scheme (default 0 = off).
2572 usbcore.use_both_schemes=
2573 [USB] Try the other device initialization scheme
2574 if the first one fails (default 1 = enabled).
2576 usbcore.initial_descriptor_timeout=
2577 [USB] Specifies timeout for the initial 64-byte
2578 USB_REQ_GET_DESCRIPTOR request in milliseconds
2579 (default 5000 = 5.0 seconds).
2581 usbhid.mousepoll=
2582 [USBHID] The interval which mice are to be polled at.
2584 usb-storage.delay_use=
2585 [UMS] The delay in seconds before a new device is
2586 scanned for Logical Units (default 5).
2588 usb-storage.quirks=
2589 [UMS] A list of quirks entries to supplement or
2590 override the built-in unusual_devs list. List
2591 entries are separated by commas. Each entry has
2592 the form VID:PID:Flags where VID and PID are Vendor
2593 and Product ID values (4-digit hex numbers) and
2594 Flags is a set of characters, each corresponding
2595 to a common usb-storage quirk flag as follows:
2596 a = SANE_SENSE (collect more than 18 bytes
2597 of sense data);
2598 b = BAD_SENSE (don't collect more than 18
2599 bytes of sense data);
2600 c = FIX_CAPACITY (decrease the reported
2601 device capacity by one sector);
2602 d = NO_READ_DISC_INFO (don't use
2603 READ_DISC_INFO command);
2604 e = NO_READ_CAPACITY_16 (don't use
2605 READ_CAPACITY_16 command);
2606 h = CAPACITY_HEURISTICS (decrease the
2607 reported device capacity by one
2608 sector if the number is odd);
2609 i = IGNORE_DEVICE (don't bind to this
2610 device);
2611 l = NOT_LOCKABLE (don't try to lock and
2612 unlock ejectable media);
2613 m = MAX_SECTORS_64 (don't transfer more
2614 than 64 sectors = 32 KB at a time);
2615 n = INITIAL_READ10 (force a retry of the
2616 initial READ(10) command);
2617 o = CAPACITY_OK (accept the capacity
2618 reported by the device);
2619 r = IGNORE_RESIDUE (the device reports
2620 bogus residue values);
2621 s = SINGLE_LUN (the device has only one
2622 Logical Unit);
2623 w = NO_WP_DETECT (don't test whether the
2624 medium is write-protected).
2625 Example: quirks=0419:aaf5:rl,0421:0433:rc
2627 userpte=
2628 [X86] Flags controlling user PTE allocations.
2630 nohigh = do not allocate PTE pages in
2631 HIGHMEM regardless of setting
2632 of CONFIG_HIGHPTE.
2634 vdso= [X86,SH]
2635 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2636 vdso=1: enable VDSO (default)
2637 vdso=0: disable VDSO mapping
2639 vdso32= [X86]
2640 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2641 vdso32=1: enable 32-bit VDSO (default)
2642 vdso32=0: disable 32-bit VDSO mapping
2644 vector= [IA-64,SMP]
2645 vector=percpu: enable percpu vector domain
2647 video= [FB] Frame buffer configuration
2648 See Documentation/fb/modedb.txt.
2650 vga= [BOOT,X86-32] Select a particular video mode
2651 See Documentation/x86/boot.txt and
2652 Documentation/svga.txt.
2653 Use vga=ask for menu.
2654 This is actually a boot loader parameter; the value is
2655 passed to the kernel using a special protocol.
2657 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2658 size of <nn>. This can be used to increase the
2659 minimum size (128MB on x86). It can also be used to
2660 decrease the size and leave more room for directly
2661 mapped kernel RAM.
2663 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2664 Format: <command>
2666 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2667 Format: <command>
2669 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2670 Format: <command>
2672 vt.cur_default= [VT] Default cursor shape.
2673 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2674 the parameters of the <Esc>[?A;B;Cc escape sequence;
2675 see VGA-softcursor.txt. Default: 2 = underline.
2677 vt.default_blu= [VT]
2678 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2679 Change the default blue palette of the console.
2680 This is a 16-member array composed of values
2681 ranging from 0-255.
2683 vt.default_grn= [VT]
2684 Format: <green0>,<green1>,<green2>,...,<green15>
2685 Change the default green palette of the console.
2686 This is a 16-member array composed of values
2687 ranging from 0-255.
2689 vt.default_red= [VT]
2690 Format: <red0>,<red1>,<red2>,...,<red15>
2691 Change the default red palette of the console.
2692 This is a 16-member array composed of values
2693 ranging from 0-255.
2695 vt.default_utf8=
2696 [VT]
2697 Format=<0|1>
2698 Set system-wide default UTF-8 mode for all tty's.
2699 Default is 1, i.e. UTF-8 mode is enabled for all
2700 newly opened terminals.
2702 vt.global_cursor_default=
2703 [VT]
2704 Format=<-1|0|1>
2705 Set system-wide default for whether a cursor
2706 is shown on new VTs. Default is -1,
2707 i.e. cursors will be created by default unless
2708 overridden by individual drivers. 0 will hide
2709 cursors, 1 will display them.
2711 watchdog timers [HW,WDT] For information on watchdog timers,
2712 see Documentation/watchdog/watchdog-parameters.txt
2713 or other driver-specific files in the
2714 Documentation/watchdog/ directory.
2716 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2717 default x2apic cluster mode on platforms
2718 supporting x2apic.
2720 x86_mrst_timer= [X86-32,APBT]
2721 Choose timer option for x86 Moorestown MID platform.
2722 Two valid options are apbt timer only and lapic timer
2723 plus one apbt timer for broadcast timer.
2724 x86_mrst_timer=apbt_only | lapic_and_apbt
2726 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2727 xd_geo= See header of drivers/block/xd.c.
2729 xen_emul_unplug= [HW,X86,XEN]
2730 Unplug Xen emulated devices
2731 Format: [unplug0,][unplug1]
2732 ide-disks -- unplug primary master IDE devices
2733 aux-ide-disks -- unplug non-primary-master IDE devices
2734 nics -- unplug network devices
2735 all -- unplug all emulated devices (NICs and IDE disks)
2736 unnecessary -- unplugging emulated devices is
2737 unnecessary even if the host did not respond to
2738 the unplug protocol
2739 never -- do not unplug even if version check succeeds
2741 xirc2ps_cs= [NET,PCMCIA]
2742 Format:
2743 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2745 ______________________________________________________________________
2747 TODO:
2749 Add more DRM drivers.