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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, s4_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.
1003 intremap= [X86-64, Intel-IOMMU]
1004 Format: { on (default) | off | nosid }
1005 on enable Interrupt Remapping (default)
1006 off disable Interrupt Remapping
1007 nosid disable Source ID checking
1009 inttest= [IA64]
1011 iomem= Disable strict checking of access to MMIO memory
1012 strict regions from userspace.
1013 relaxed
1015 iommu= [x86]
1016 off
1017 force
1018 noforce
1019 biomerge
1020 panic
1021 nopanic
1022 merge
1023 nomerge
1024 forcesac
1025 soft
1026 pt [x86, IA64]
1028 io7= [HW] IO7 for Marvel based alpha systems
1029 See comment before marvel_specify_io7 in
1030 arch/alpha/kernel/core_marvel.c.
1032 io_delay= [X86] I/O delay method
1033 0x80
1034 Standard port 0x80 based delay
1035 0xed
1036 Alternate port 0xed based delay (needed on some systems)
1037 udelay
1038 Simple two microseconds delay
1039 none
1040 No delay
1042 ip= [IP_PNP]
1043 See Documentation/filesystems/nfs/nfsroot.txt.
1045 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1046 See comment before ip2_setup() in
1047 drivers/char/ip2/ip2base.c.
1049 irqfixup [HW]
1050 When an interrupt is not handled search all handlers
1051 for it. Intended to get systems with badly broken
1052 firmware running.
1054 irqpoll [HW]
1055 When an interrupt is not handled search all handlers
1056 for it. Also check all handlers each timer
1057 interrupt. Intended to get systems with badly broken
1058 firmware running.
1060 isapnp= [ISAPNP]
1061 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1063 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1064 Format:
1065 <cpu number>,...,<cpu number>
1066 or
1067 <cpu number>-<cpu number>
1068 (must be a positive range in ascending order)
1069 or a mixture
1070 <cpu number>,...,<cpu number>-<cpu number>
1072 This option can be used to specify one or more CPUs
1073 to isolate from the general SMP balancing and scheduling
1074 algorithms. You can move a process onto or off an
1075 "isolated" CPU via the CPU affinity syscalls or cpuset.
1076 <cpu number> begins at 0 and the maximum value is
1077 "number of CPUs in system - 1".
1079 This option is the preferred way to isolate CPUs. The
1080 alternative -- manually setting the CPU mask of all
1081 tasks in the system -- can cause problems and
1082 suboptimal load balancer performance.
1084 iucv= [HW,NET]
1086 js= [HW,JOY] Analog joystick
1087 See Documentation/input/joystick.txt.
1089 keepinitrd [HW,ARM]
1091 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1092 specifies the amount of memory usable by the kernel
1093 for non-movable allocations. The requested amount is
1094 spread evenly throughout all nodes in the system. The
1095 remaining memory in each node is used for Movable
1096 pages. In the event, a node is too small to have both
1097 kernelcore and Movable pages, kernelcore pages will
1098 take priority and other nodes will have a larger number
1099 of kernelcore pages. The Movable zone is used for the
1100 allocation of pages that may be reclaimed or moved
1101 by the page migration subsystem. This means that
1102 HugeTLB pages may not be allocated from this zone.
1103 Note that allocations like PTEs-from-HighMem still
1104 use the HighMem zone if it exists, and the Normal
1105 zone if it does not.
1107 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1108 Format: <Controller#>[,poll interval]
1109 The controller # is the number of the ehci usb debug
1110 port as it is probed via PCI. The poll interval is
1111 optional and is the number seconds in between
1112 each poll cycle to the debug port in case you need
1113 the functionality for interrupting the kernel with
1114 gdb or control-c on the dbgp connection. When
1115 not using this parameter you use sysrq-g to break into
1116 the kernel debugger.
1118 kgdboc= [KGDB,HW] kgdb over consoles.
1119 Requires a tty driver that supports console polling,
1120 or a supported polling keyboard driver (non-usb).
1121 Serial only format: <serial_device>[,baud]
1122 keyboard only format: kbd
1123 keyboard and serial format: kbd,<serial_device>[,baud]
1124 Optional Kernel mode setting:
1125 kms, kbd format: kms,kbd
1126 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1128 kgdbwait [KGDB] Stop kernel execution and enter the
1129 kernel debugger at the earliest opportunity.
1131 kmac= [MIPS] korina ethernet MAC address.
1132 Configure the RouterBoard 532 series on-chip
1133 Ethernet adapter MAC address.
1135 kmemleak= [KNL] Boot-time kmemleak enable/disable
1136 Valid arguments: on, off
1137 Default: on
1139 kstack=N [X86] Print N words from the kernel stack
1140 in oops dumps.
1142 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1143 Default is 0 (don't ignore, but inject #GP)
1145 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1146 Default is 1 (enabled)
1148 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1149 KVM MMU at runtime.
1150 Default is 0 (off)
1152 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1153 Default is 1 (enabled)
1155 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1156 for all guests.
1157 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1159 kvm-intel.bypass_guest_pf=
1160 [KVM,Intel] Disables bypassing of guest page faults
1161 on Intel chips. Default is 1 (enabled)
1163 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1164 (virtualized MMU) support on capable Intel chips.
1165 Default is 1 (enabled)
1167 kvm-intel.emulate_invalid_guest_state=
1168 [KVM,Intel] Enable emulation of invalid guest states
1169 Default is 0 (disabled)
1171 kvm-intel.flexpriority=
1172 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1173 Default is 1 (enabled)
1175 kvm-intel.unrestricted_guest=
1176 [KVM,Intel] Disable unrestricted guest feature
1177 (virtualized real and unpaged mode) on capable
1178 Intel chips. Default is 1 (enabled)
1180 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1181 feature (tagged TLBs) on capable Intel chips.
1182 Default is 1 (enabled)
1184 l2cr= [PPC]
1186 l3cr= [PPC]
1188 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1189 disabled it.
1191 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1192 in C2 power state.
1194 libata.dma= [LIBATA] DMA control
1195 libata.dma=0 Disable all PATA and SATA DMA
1196 libata.dma=1 PATA and SATA Disk DMA only
1197 libata.dma=2 ATAPI (CDROM) DMA only
1198 libata.dma=4 Compact Flash DMA only
1199 Combinations also work, so libata.dma=3 enables DMA
1200 for disks and CDROMs, but not CFs.
1202 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1203 libata.ignore_hpa=0 keep BIOS limits (default)
1204 libata.ignore_hpa=1 ignore limits, using full disk
1206 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1207 when set.
1208 Format: <int>
1210 libata.force= [LIBATA] Force configurations. The format is comma
1211 separated list of "[ID:]VAL" where ID is
1212 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1213 matching port, link or device. Basically, it matches
1214 the ATA ID string printed on console by libata. If
1215 the whole ID part is omitted, the last PORT and DEVICE
1216 values are used. If ID hasn't been specified yet, the
1217 configuration applies to all ports, links and devices.
1219 If only DEVICE is omitted, the parameter applies to
1220 the port and all links and devices behind it. DEVICE
1221 number of 0 either selects the first device or the
1222 first fan-out link behind PMP device. It does not
1223 select the host link. DEVICE number of 15 selects the
1224 host link and device attached to it.
1226 The VAL specifies the configuration to force. As long
1227 as there's no ambiguity shortcut notation is allowed.
1228 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1229 The following configurations can be forced.
1231 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1232 Any ID with matching PORT is used.
1234 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1236 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1237 udma[/][16,25,33,44,66,100,133] notation is also
1238 allowed.
1240 * [no]ncq: Turn on or off NCQ.
1242 * nohrst, nosrst, norst: suppress hard, soft
1243 and both resets.
1245 * dump_id: dump IDENTIFY data.
1247 If there are multiple matching configurations changing
1248 the same attribute, the last one is used.
1250 memblock=debug [KNL] Enable memblock debug messages.
1252 load_ramdisk= [RAM] List of ramdisks to load from floppy
1253 See Documentation/blockdev/ramdisk.txt.
1255 lockd.nlm_grace_period=P [NFS] Assign grace period.
1256 Format: <integer>
1258 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1259 Format: <integer>
1261 lockd.nlm_timeout=T [NFS] Assign timeout value.
1262 Format: <integer>
1264 lockd.nlm_udpport=M [NFS] Assign UDP port.
1265 Format: <integer>
1267 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1268 Format: <irq>
1270 loglevel= All Kernel Messages with a loglevel smaller than the
1271 console loglevel will be printed to the console. It can
1272 also be changed with klogd or other programs. The
1273 loglevels are defined as follows:
1275 0 (KERN_EMERG) system is unusable
1276 1 (KERN_ALERT) action must be taken immediately
1277 2 (KERN_CRIT) critical conditions
1278 3 (KERN_ERR) error conditions
1279 4 (KERN_WARNING) warning conditions
1280 5 (KERN_NOTICE) normal but significant condition
1281 6 (KERN_INFO) informational
1282 7 (KERN_DEBUG) debug-level messages
1284 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1285 in bytes. n must be a power of two. The default
1286 size is set in the kernel config file.
1288 logo.nologo [FB] Disables display of the built-in Linux logo.
1289 This may be used to provide more screen space for
1290 kernel log messages and is useful when debugging
1291 kernel boot problems.
1293 lp=0 [LP] Specify parallel ports to use, e.g,
1294 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1295 lp=reset first parallel port). 'lp=0' disables the
1296 lp=auto printer driver. 'lp=reset' (which can be
1297 specified in addition to the ports) causes
1298 attached printers to be reset. Using
1299 lp=port1,port2,... specifies the parallel ports
1300 to associate lp devices with, starting with
1301 lp0. A port specification may be 'none' to skip
1302 that lp device, or a parport name such as
1303 'parport0'. Specifying 'lp=auto' instead of a
1304 port specification list means that device IDs
1305 from each port should be examined, to see if
1306 an IEEE 1284-compliant printer is attached; if
1307 so, the driver will manage that printer.
1308 See also header of drivers/char/lp.c.
1310 lpj=n [KNL]
1311 Sets loops_per_jiffy to given constant, thus avoiding
1312 time-consuming boot-time autodetection (up to 250 ms per
1313 CPU). 0 enables autodetection (default). To determine
1314 the correct value for your kernel, boot with normal
1315 autodetection and see what value is printed. Note that
1316 on SMP systems the preset will be applied to all CPUs,
1317 which is likely to cause problems if your CPUs need
1318 significantly divergent settings. An incorrect value
1319 will cause delays in the kernel to be wrong, leading to
1320 unpredictable I/O errors and other breakage. Although
1321 unlikely, in the extreme case this might damage your
1322 hardware.
1324 ltpc= [NET]
1325 Format: <io>,<irq>,<dma>
1327 machvec= [IA64] Force the use of a particular machine-vector
1328 (machvec) in a generic kernel.
1329 Example: machvec=hpzx1_swiotlb
1331 machtype= [Loongson] Share the same kernel image file between different
1332 yeeloong laptop.
1333 Example: machtype=lemote-yeeloong-2f-7inch
1335 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1336 than or equal to this physical address is ignored.
1338 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1339 should make use of. maxcpus=n : n >= 0 limits the
1340 kernel to using 'n' processors. n=0 is a special case,
1341 it is equivalent to "nosmp", which also disables
1342 the IO APIC.
1344 max_loop= [LOOP] Maximum number of loopback devices that can
1345 be mounted
1346 Format: <1-256>
1348 mcatest= [IA-64]
1350 mce [X86-32] Machine Check Exception
1352 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1354 md= [HW] RAID subsystems devices and level
1355 See Documentation/md.txt.
1357 mdacon= [MDA]
1358 Format: <first>,<last>
1359 Specifies range of consoles to be captured by the MDA.
1361 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1362 Amount of memory to be used when the kernel is not able
1363 to see the whole system memory or for test.
1364 [X86-32] Use together with memmap= to avoid physical
1365 address space collisions. Without memmap= PCI devices
1366 could be placed at addresses belonging to unused RAM.
1368 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1369 memory.
1371 memchunk=nn[KMG]
1372 [KNL,SH] Allow user to override the default size for
1373 per-device physically contiguous DMA buffers.
1375 memmap=exactmap [KNL,X86] Enable setting of an exact
1376 E820 memory map, as specified by the user.
1377 Such memmap=exactmap lines can be constructed based on
1378 BIOS output or other requirements. See the memmap=nn@ss
1379 option description.
1381 memmap=nn[KMG]@ss[KMG]
1382 [KNL] Force usage of a specific region of memory
1383 Region of memory to be used, from ss to ss+nn.
1385 memmap=nn[KMG]#ss[KMG]
1386 [KNL,ACPI] Mark specific memory as ACPI data.
1387 Region of memory to be used, from ss to ss+nn.
1389 memmap=nn[KMG]$ss[KMG]
1390 [KNL,ACPI] Mark specific memory as reserved.
1391 Region of memory to be used, from ss to ss+nn.
1392 Example: Exclude memory from 0x18690000-0x1869ffff
1393 memmap=64K$0x18690000
1394 or
1395 memmap=0x10000$0x18690000
1397 memory_corruption_check=0/1 [X86]
1398 Some BIOSes seem to corrupt the first 64k of
1399 memory when doing things like suspend/resume.
1400 Setting this option will scan the memory
1401 looking for corruption. Enabling this will
1402 both detect corruption and prevent the kernel
1403 from using the memory being corrupted.
1404 However, its intended as a diagnostic tool; if
1405 repeatable BIOS-originated corruption always
1406 affects the same memory, you can use memmap=
1407 to prevent the kernel from using that memory.
1409 memory_corruption_check_size=size [X86]
1410 By default it checks for corruption in the low
1411 64k, making this memory unavailable for normal
1412 use. Use this parameter to scan for
1413 corruption in more or less memory.
1415 memory_corruption_check_period=seconds [X86]
1416 By default it checks for corruption every 60
1417 seconds. Use this parameter to check at some
1418 other rate. 0 disables periodic checking.
1420 memtest= [KNL,X86] Enable memtest
1421 Format: <integer>
1422 default : 0 <disable>
1423 Specifies the number of memtest passes to be
1424 performed. Each pass selects another test
1425 pattern from a given set of patterns. Memtest
1426 fills the memory with this pattern, validates
1427 memory contents and reserves bad memory
1428 regions that are detected.
1430 meye.*= [HW] Set MotionEye Camera parameters
1431 See Documentation/video4linux/meye.txt.
1433 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1434 Multi-Function General Purpose Timers on AMD Geode
1435 platforms.
1437 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1438 the BIOS has incorrectly applied a workaround. TinyBIOS
1439 version 0.98 is known to be affected, 0.99 fixes the
1440 problem by letting the user disable the workaround.
1442 mga= [HW,DRM]
1444 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1445 physical address is ignored.
1447 mini2440= [ARM,HW,KNL]
1448 Format:[0..2][b][c][t]
1449 Default: "0tb"
1450 MINI2440 configuration specification:
1451 0 - The attached screen is the 3.5" TFT
1452 1 - The attached screen is the 7" TFT
1453 2 - The VGA Shield is attached (1024x768)
1454 Leaving out the screen size parameter will not load
1455 the TFT driver, and the framebuffer will be left
1456 unconfigured.
1457 b - Enable backlight. The TFT backlight pin will be
1458 linked to the kernel VESA blanking code and a GPIO
1459 LED. This parameter is not necessary when using the
1460 VGA shield.
1461 c - Enable the s3c camera interface.
1462 t - Reserved for enabling touchscreen support. The
1463 touchscreen support is not enabled in the mainstream
1464 kernel as of 2.6.30, a preliminary port can be found
1465 in the "bleeding edge" mini2440 support kernel at
1466 http://repo.or.cz/w/linux-2.6/mini2440.git
1468 mminit_loglevel=
1469 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1470 parameter allows control of the logging verbosity for
1471 the additional memory initialisation checks. A value
1472 of 0 disables mminit logging and a level of 4 will
1473 log everything. Information is printed at KERN_DEBUG
1474 so loglevel=8 may also need to be specified.
1476 mousedev.tap_time=
1477 [MOUSE] Maximum time between finger touching and
1478 leaving touchpad surface for touch to be considered
1479 a tap and be reported as a left button click (for
1480 touchpads working in absolute mode only).
1481 Format: <msecs>
1482 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1483 reporting absolute coordinates, such as tablets
1484 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1485 reporting absolute coordinates, such as tablets
1487 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1488 is similar to kernelcore except it specifies the
1489 amount of memory used for migratable allocations.
1490 If both kernelcore and movablecore is specified,
1491 then kernelcore will be at *least* the specified
1492 value but may be more. If movablecore on its own
1493 is specified, the administrator must be careful
1494 that the amount of memory usable for all allocations
1495 is not too small.
1497 MTD_Partition= [MTD]
1498 Format: <name>,<region-number>,<size>,<offset>
1500 MTD_Region= [MTD] Format:
1501 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1503 mtdparts= [MTD]
1504 See drivers/mtd/cmdlinepart.c.
1506 multitce=off [PPC] This parameter disables the use of the pSeries
1507 firmware feature for updating multiple TCE entries
1508 at a time.
1510 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1512 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1514 boundary - index of last SLC block on Flex-OneNAND.
1515 The remaining blocks are configured as MLC blocks.
1516 lock - Configure if Flex-OneNAND boundary should be locked.
1517 Once locked, the boundary cannot be changed.
1518 1 indicates lock status, 0 indicates unlock status.
1520 mtdset= [ARM]
1521 ARM/S3C2412 JIVE boot control
1523 See arch/arm/mach-s3c2412/mach-jive.c
1525 mtouchusb.raw_coordinates=
1526 [HW] Make the MicroTouch USB driver use raw coordinates
1527 ('y', default) or cooked coordinates ('n')
1529 mtrr_chunk_size=nn[KMG] [X86]
1530 used for mtrr cleanup. It is largest continuous chunk
1531 that could hold holes aka. UC entries.
1533 mtrr_gran_size=nn[KMG] [X86]
1534 Used for mtrr cleanup. It is granularity of mtrr block.
1535 Default is 1.
1536 Large value could prevent small alignment from
1537 using up MTRRs.
1539 mtrr_spare_reg_nr=n [X86]
1540 Format: <integer>
1541 Range: 0,7 : spare reg number
1542 Default : 1
1543 Used for mtrr cleanup. It is spare mtrr entries number.
1544 Set to 2 or more if your graphical card needs more.
1546 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1548 netdev= [NET] Network devices parameters
1549 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1550 Note that mem_start is often overloaded to mean
1551 something different and driver-specific.
1552 This usage is only documented in each driver source
1553 file if at all.
1555 nf_conntrack.acct=
1556 [NETFILTER] Enable connection tracking flow accounting
1557 0 to disable accounting
1558 1 to enable accounting
1559 Default value is 0.
1561 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1562 See Documentation/filesystems/nfs/nfsroot.txt.
1564 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1565 See Documentation/filesystems/nfs/nfsroot.txt.
1567 nfsrootdebug [NFS] enable nfsroot debugging messages.
1568 See Documentation/filesystems/nfs/nfsroot.txt.
1570 nfs.callback_tcpport=
1571 [NFS] set the TCP port on which the NFSv4 callback
1572 channel should listen.
1574 nfs.cache_getent=
1575 [NFS] sets the pathname to the program which is used
1576 to update the NFS client cache entries.
1578 nfs.cache_getent_timeout=
1579 [NFS] sets the timeout after which an attempt to
1580 update a cache entry is deemed to have failed.
1582 nfs.idmap_cache_timeout=
1583 [NFS] set the maximum lifetime for idmapper cache
1584 entries.
1586 nfs.enable_ino64=
1587 [NFS] enable 64-bit inode numbers.
1588 If zero, the NFS client will fake up a 32-bit inode
1589 number for the readdir() and stat() syscalls instead
1590 of returning the full 64-bit number.
1591 The default is to return 64-bit inode numbers.
1593 nfs.nfs4_disable_idmapping=
1594 [NFSv4] When set, this option disables the NFSv4
1595 idmapper on the client, but only if the mount
1596 is using the 'sec=sys' security flavour. This may
1597 make migration from legacy NFSv2/v3 systems easier
1598 provided that the server has the appropriate support.
1599 The default is to always enable NFSv4 idmapping.
1601 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1602 when a NMI is triggered.
1603 Format: [state][,regs][,debounce][,die]
1605 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1606 Format: [panic,][nopanic,][num]
1607 Valid num: 0
1608 0 - turn nmi_watchdog off
1609 When panic is specified, panic when an NMI watchdog
1610 timeout occurs (or 'nopanic' to override the opposite
1611 default).
1612 This is useful when you use a panic=... timeout and
1613 need the box quickly up again.
1615 netpoll.carrier_timeout=
1616 [NET] Specifies amount of time (in seconds) that
1617 netpoll should wait for a carrier. By default netpoll
1618 waits 4 seconds.
1620 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1621 emulation library even if a 387 maths coprocessor
1622 is present.
1624 no_console_suspend
1625 [HW] Never suspend the console
1626 Disable suspending of consoles during suspend and
1627 hibernate operations. Once disabled, debugging
1628 messages can reach various consoles while the rest
1629 of the system is being put to sleep (ie, while
1630 debugging driver suspend/resume hooks). This may
1631 not work reliably with all consoles, but is known
1632 to work with serial and VGA consoles.
1634 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1635 caches in the slab allocator. Saves per-node memory,
1636 but will impact performance.
1638 noalign [KNL,ARM]
1640 noapic [SMP,APIC] Tells the kernel to not make use of any
1641 IOAPICs that may be present in the system.
1643 noautogroup Disable scheduler automatic task group creation.
1645 nobats [PPC] Do not use BATs for mapping kernel lowmem
1646 on "Classic" PPC cores.
1648 nocache [ARM]
1650 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1652 nodelayacct [KNL] Disable per-task delay accounting
1654 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1656 nodsp [SH] Disable hardware DSP at boot time.
1658 noefi [X86] Disable EFI runtime services support.
1660 noexec [IA-64]
1662 noexec [X86]
1663 On X86-32 available only on PAE configured kernels.
1664 noexec=on: enable non-executable mappings (default)
1665 noexec=off: disable non-executable mappings
1667 noexec32 [X86-64]
1668 This affects only 32-bit executables.
1669 noexec32=on: enable non-executable mappings (default)
1670 read doesn't imply executable mappings
1671 noexec32=off: disable non-executable mappings
1672 read implies executable mappings
1674 nofpu [SH] Disable hardware FPU at boot time.
1676 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1677 register save and restore. The kernel will only save
1678 legacy floating-point registers on task switch.
1680 noxsave [BUGS=X86] Disables x86 extended register state save
1681 and restore using xsave. The kernel will fallback to
1682 enabling legacy floating-point and sse state.
1684 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1685 wfi(ARM) instruction doesn't work correctly and not to
1686 use it. This is also useful when using JTAG debugger.
1688 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1689 instruction doesn't work correctly and not to
1690 use it.
1692 no_file_caps Tells the kernel not to honor file capabilities. The
1693 only way then for a file to be executed with privilege
1694 is to be setuid root or executed by root.
1696 nohalt [IA-64] Tells the kernel not to use the power saving
1697 function PAL_HALT_LIGHT when idle. This increases
1698 power-consumption. On the positive side, it reduces
1699 interrupt wake-up latency, which may improve performance
1700 in certain environments such as networked servers or
1701 real-time systems.
1703 nohz= [KNL] Boottime enable/disable dynamic ticks
1704 Valid arguments: on, off
1705 Default: on
1707 noiotrap [SH] Disables trapped I/O port accesses.
1709 noirqdebug [X86-32] Disables the code which attempts to detect and
1710 disable unhandled interrupt sources.
1712 no_timer_check [X86,APIC] Disables the code which tests for
1713 broken timer IRQ sources.
1715 noisapnp [ISAPNP] Disables ISA PnP code.
1717 noinitrd [RAM] Tells the kernel not to load any configured
1718 initial RAM disk.
1720 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1721 remapping.
1722 [Deprecated - use intremap=off]
1724 nointroute [IA-64]
1726 nojitter [IA64] Disables jitter checking for ITC timers.
1728 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1730 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1731 fault handling.
1733 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1735 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1737 noltlbs [PPC] Do not use large page/tlb entries for kernel
1738 lowmem mapping on PPC40x.
1740 nomca [IA-64] Disable machine check abort handling
1742 nomce [X86-32] Machine Check Exception
1744 nomfgpt [X86-32] Disable Multi-Function General Purpose
1745 Timer usage (for AMD Geode machines).
1747 nopat [X86] Disable PAT (page attribute table extension of
1748 pagetables) support.
1750 norandmaps Don't use address space randomization. Equivalent to
1751 echo 0 > /proc/sys/kernel/randomize_va_space
1753 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1755 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1756 with UP alternatives
1758 noresidual [PPC] Don't use residual data on PReP machines.
1760 noresume [SWSUSP] Disables resume and restores original swap
1761 space.
1763 no-scroll [VGA] Disables scrollback.
1764 This is required for the Braillex ib80-piezo Braille
1765 reader made by F.H. Papenmeier (Germany).
1767 nosbagart [IA-64]
1769 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1771 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1772 and disable the IO APIC. legacy for "maxcpus=0".
1774 nosoftlockup [KNL] Disable the soft-lockup detector.
1776 noswapaccount [KNL] Disable accounting of swap in memory resource
1777 controller. (See Documentation/cgroups/memory.txt)
1779 nosync [HW,M68K] Disables sync negotiation for all devices.
1781 notsc [BUGS=X86-32] Disable Time Stamp Counter
1783 nousb [USB] Disable the USB subsystem
1785 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1787 nowb [ARM]
1789 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1791 nptcg= [IA64] Override max number of concurrent global TLB
1792 purges which is reported from either PAL_VM_SUMMARY or
1793 SAL PALO.
1795 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1796 could support. nr_cpus=n : n >= 1 limits the kernel to
1797 supporting 'n' processors. Later in runtime you can not
1798 use hotplug cpu feature to put more cpu back to online.
1799 just like you compile the kernel NR_CPUS=n
1801 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1803 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1804 one of ['zone', 'node', 'default'] can be specified
1805 This can be set from sysctl after boot.
1806 See Documentation/sysctl/vm.txt for details.
1808 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1809 See Documentation/debugging-via-ohci1394.txt for more
1810 info.
1812 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1813 Rather than timing out after 20 ms if an EC
1814 command is not properly ACKed, override the length
1815 of the timeout. We have interrupts disabled while
1816 waiting for the ACK, so if this is set too high
1817 interrupts *may* be lost!
1819 omap_mux= [OMAP] Override bootloader pin multiplexing.
1820 Format: <mux_mode0.mode_name=value>...
1821 For example, to override I2C bus2:
1822 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1824 oprofile.timer= [HW]
1825 Use timer interrupt instead of performance counters
1827 oprofile.cpu_type= Force an oprofile cpu type
1828 This might be useful if you have an older oprofile
1829 userland or if you want common events.
1830 Format: { arch_perfmon }
1831 arch_perfmon: [X86] Force use of architectural
1832 perfmon on Intel CPUs instead of the
1833 CPU specific event set.
1835 oops=panic Always panic on oopses. Default is to just kill the
1836 process, but there is a small probability of
1837 deadlocking the machine.
1838 This will also cause panics on machine check exceptions.
1839 Useful together with panic=30 to trigger a reboot.
1841 OSS [HW,OSS]
1842 See Documentation/sound/oss/oss-parameters.txt
1844 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1845 seconds before rebooting
1846 Format: <timeout>
1848 parkbd.port= [HW] Parallel port number the keyboard adapter is
1849 connected to, default is 0.
1850 Format: <parport#>
1851 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1852 0 for XT, 1 for AT (default is AT).
1853 Format: <mode>
1855 parport= [HW,PPT] Specify parallel ports. 0 disables.
1856 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1857 Use 'auto' to force the driver to use any
1858 IRQ/DMA settings detected (the default is to
1859 ignore detected IRQ/DMA settings because of
1860 possible conflicts). You can specify the base
1861 address, IRQ, and DMA settings; IRQ and DMA
1862 should be numbers, or 'auto' (for using detected
1863 settings on that particular port), or 'nofifo'
1864 (to avoid using a FIFO even if it is detected).
1865 Parallel ports are assigned in the order they
1866 are specified on the command line, starting
1867 with parport0.
1869 parport_init_mode= [HW,PPT]
1870 Configure VIA parallel port to operate in
1871 a specific mode. This is necessary on Pegasos
1872 computer where firmware has no options for setting
1873 up parallel port mode and sets it to spp.
1874 Currently this function knows 686a and 8231 chips.
1875 Format: [spp|ps2|epp|ecp|ecpepp]
1877 pause_on_oops=
1878 Halt all CPUs after the first oops has been printed for
1879 the specified number of seconds. This is to be used if
1880 your oopses keep scrolling off the screen.
1882 pcbit= [HW,ISDN]
1884 pcd. [PARIDE]
1885 See header of drivers/block/paride/pcd.c.
1886 See also Documentation/blockdev/paride.txt.
1888 pci=option[,option...] [PCI] various PCI subsystem options:
1889 earlydump [X86] dump PCI config space before the kernel
1890 changes anything
1891 off [X86] don't probe for the PCI bus
1892 bios [X86-32] force use of PCI BIOS, don't access
1893 the hardware directly. Use this if your machine
1894 has a non-standard PCI host bridge.
1895 nobios [X86-32] disallow use of PCI BIOS, only direct
1896 hardware access methods are allowed. Use this
1897 if you experience crashes upon bootup and you
1898 suspect they are caused by the BIOS.
1899 conf1 [X86] Force use of PCI Configuration
1900 Mechanism 1.
1901 conf2 [X86] Force use of PCI Configuration
1902 Mechanism 2.
1903 noaer [PCIE] If the PCIEAER kernel config parameter is
1904 enabled, this kernel boot option can be used to
1905 disable the use of PCIE advanced error reporting.
1906 nodomains [PCI] Disable support for multiple PCI
1907 root domains (aka PCI segments, in ACPI-speak).
1908 nommconf [X86] Disable use of MMCONFIG for PCI
1909 Configuration
1910 check_enable_amd_mmconf [X86] check for and enable
1911 properly configured MMIO access to PCI
1912 config space on AMD family 10h CPU
1913 nomsi [MSI] If the PCI_MSI kernel config parameter is
1914 enabled, this kernel boot option can be used to
1915 disable the use of MSI interrupts system-wide.
1916 noioapicquirk [APIC] Disable all boot interrupt quirks.
1917 Safety option to keep boot IRQs enabled. This
1918 should never be necessary.
1919 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1920 primary IO-APIC for bridges that cannot disable
1921 boot IRQs. This fixes a source of spurious IRQs
1922 when the system masks IRQs.
1923 noioapicreroute [APIC] Disable workaround that uses the
1924 boot IRQ equivalent of an IRQ that connects to
1925 a chipset where boot IRQs cannot be disabled.
1926 The opposite of ioapicreroute.
1927 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1928 routing table. These calls are known to be buggy
1929 on several machines and they hang the machine
1930 when used, but on other computers it's the only
1931 way to get the interrupt routing table. Try
1932 this option if the kernel is unable to allocate
1933 IRQs or discover secondary PCI buses on your
1934 motherboard.
1935 rom [X86] Assign address space to expansion ROMs.
1936 Use with caution as certain devices share
1937 address decoders between ROMs and other
1938 resources.
1939 norom [X86] Do not assign address space to
1940 expansion ROMs that do not already have
1941 BIOS assigned address ranges.
1942 nobar [X86] Do not assign address space to the
1943 BARs that weren't assigned by the BIOS.
1944 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1945 assigned automatically to PCI devices. You can
1946 make the kernel exclude IRQs of your ISA cards
1947 this way.
1948 pirqaddr=0xAAAAA [X86] Specify the physical address
1949 of the PIRQ table (normally generated
1950 by the BIOS) if it is outside the
1951 F0000h-100000h range.
1952 lastbus=N [X86] Scan all buses thru bus #N. Can be
1953 useful if the kernel is unable to find your
1954 secondary buses and you want to tell it
1955 explicitly which ones they are.
1956 assign-busses [X86] Always assign all PCI bus
1957 numbers ourselves, overriding
1958 whatever the firmware may have done.
1959 usepirqmask [X86] Honor the possible IRQ mask stored
1960 in the BIOS $PIR table. This is needed on
1961 some systems with broken BIOSes, notably
1962 some HP Pavilion N5400 and Omnibook XE3
1963 notebooks. This will have no effect if ACPI
1964 IRQ routing is enabled.
1965 noacpi [X86] Do not use ACPI for IRQ routing
1966 or for PCI scanning.
1967 use_crs [X86] Use PCI host bridge window information
1968 from ACPI. On BIOSes from 2008 or later, this
1969 is enabled by default. If you need to use this,
1970 please report a bug.
1971 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1972 If you need to use this, please report a bug.
1973 routeirq Do IRQ routing for all PCI devices.
1974 This is normally done in pci_enable_device(),
1975 so this option is a temporary workaround
1976 for broken drivers that don't call it.
1977 skip_isa_align [X86] do not align io start addr, so can
1978 handle more pci cards
1979 firmware [ARM] Do not re-enumerate the bus but instead
1980 just use the configuration from the
1981 bootloader. This is currently used on
1982 IXP2000 systems where the bus has to be
1983 configured a certain way for adjunct CPUs.
1984 noearly [X86] Don't do any early type 1 scanning.
1985 This might help on some broken boards which
1986 machine check when some devices' config space
1987 is read. But various workarounds are disabled
1988 and some IOMMU drivers will not work.
1989 bfsort Sort PCI devices into breadth-first order.
1990 This sorting is done to get a device
1991 order compatible with older (<= 2.4) kernels.
1992 nobfsort Don't sort PCI devices into breadth-first order.
1993 cbiosize=nn[KMG] The fixed amount of bus space which is
1994 reserved for the CardBus bridge's IO window.
1995 The default value is 256 bytes.
1996 cbmemsize=nn[KMG] The fixed amount of bus space which is
1997 reserved for the CardBus bridge's memory
1998 window. The default value is 64 megabytes.
1999 resource_alignment=
2000 Format:
2001 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2002 Specifies alignment and device to reassign
2003 aligned memory resources.
2004 If <order of align> is not specified,
2005 PAGE_SIZE is used as alignment.
2006 PCI-PCI bridge can be specified, if resource
2007 windows need to be expanded.
2008 ecrc= Enable/disable PCIe ECRC (transaction layer
2009 end-to-end CRC checking).
2010 bios: Use BIOS/firmware settings. This is the
2011 the default.
2012 off: Turn ECRC off
2013 on: Turn ECRC on.
2015 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2016 Management.
2017 off Disable ASPM.
2018 force Enable ASPM even on devices that claim not to support it.
2019 WARNING: Forcing ASPM on may cause system lockups.
2021 pcie_ports= [PCIE] PCIe ports handling:
2022 auto Ask the BIOS whether or not to use native PCIe services
2023 associated with PCIe ports (PME, hot-plug, AER). Use
2024 them only if that is allowed by the BIOS.
2025 native Use native PCIe services associated with PCIe ports
2026 unconditionally.
2027 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2028 ports driver.
2030 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2031 nomsi Do not use MSI for native PCIe PME signaling (this makes
2032 all PCIe root ports use INTx for all services).
2034 pcmv= [HW,PCMCIA] BadgePAD 4
2036 pd. [PARIDE]
2037 See Documentation/blockdev/paride.txt.
2039 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2040 boot time.
2041 Format: { 0 | 1 }
2042 See arch/parisc/kernel/pdc_chassis.c
2044 percpu_alloc= Select which percpu first chunk allocator to use.
2045 Currently supported values are "embed" and "page".
2046 Archs may support subset or none of the selections.
2047 See comments in mm/percpu.c for details on each
2048 allocator. This parameter is primarily for debugging
2049 and performance comparison.
2051 pf. [PARIDE]
2052 See Documentation/blockdev/paride.txt.
2054 pg. [PARIDE]
2055 See Documentation/blockdev/paride.txt.
2057 pirq= [SMP,APIC] Manual mp-table setup
2058 See Documentation/x86/i386/IO-APIC.txt.
2060 plip= [PPT,NET] Parallel port network link
2061 Format: { parport<nr> | timid | 0 }
2062 See also Documentation/parport.txt.
2064 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2065 Override pmtimer IOPort with a hex value.
2066 e.g. pmtmr=0x508
2068 pnp.debug [PNP]
2069 Enable PNP debug messages. This depends on the
2070 CONFIG_PNP_DEBUG_MESSAGES option.
2072 pnpacpi= [ACPI]
2073 { off }
2075 pnpbios= [ISAPNP]
2076 { on | off | curr | res | no-curr | no-res }
2078 pnp_reserve_irq=
2079 [ISAPNP] Exclude IRQs for the autoconfiguration
2081 pnp_reserve_dma=
2082 [ISAPNP] Exclude DMAs for the autoconfiguration
2084 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2085 Ranges are in pairs (I/O port base and size).
2087 pnp_reserve_mem=
2088 [ISAPNP] Exclude memory regions for the
2089 autoconfiguration.
2090 Ranges are in pairs (memory base and size).
2092 ports= [IP_VS_FTP] IPVS ftp helper module
2093 Default is 21.
2094 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2095 may be specified.
2096 Format: <port>,<port>....
2098 print-fatal-signals=
2099 [KNL] debug: print fatal signals
2101 If enabled, warn about various signal handling
2102 related application anomalies: too many signals,
2103 too many POSIX.1 timers, fatal signals causing a
2104 coredump - etc.
2106 If you hit the warning due to signal overflow,
2107 you might want to try "ulimit -i unlimited".
2109 default: off.
2111 printk.time= Show timing data prefixed to each printk message line
2112 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2114 processor.max_cstate= [HW,ACPI]
2115 Limit processor to maximum C-state
2116 max_cstate=9 overrides any DMI blacklist limit.
2118 processor.nocst [HW,ACPI]
2119 Ignore the _CST method to determine C-states,
2120 instead using the legacy FADT method
2122 profile= [KNL] Enable kernel profiling via /proc/profile
2123 Format: [schedule,]<number>
2124 Param: "schedule" - profile schedule points.
2125 Param: <number> - step/bucket size as a power of 2 for
2126 statistical time based profiling.
2127 Param: "sleep" - profile D-state sleeping (millisecs).
2128 Requires CONFIG_SCHEDSTATS
2129 Param: "kvm" - profile VM exits.
2131 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2132 before loading.
2133 See Documentation/blockdev/ramdisk.txt.
2135 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2136 probe for; one of (bare|imps|exps|lifebook|any).
2137 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2138 per second.
2139 psmouse.resetafter= [HW,MOUSE]
2140 Try to reset the device after so many bad packets
2141 (0 = never).
2142 psmouse.resolution=
2143 [HW,MOUSE] Set desired mouse resolution, in dpi.
2144 psmouse.smartscroll=
2145 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2146 0 = disabled, 1 = enabled (default).
2148 pt. [PARIDE]
2149 See Documentation/blockdev/paride.txt.
2151 pty.legacy_count=
2152 [KNL] Number of legacy pty's. Overwrites compiled-in
2153 default number.
2155 quiet [KNL] Disable most log messages
2157 r128= [HW,DRM]
2159 raid= [HW,RAID]
2160 See Documentation/md.txt.
2162 ramdisk_blocksize= [RAM]
2163 See Documentation/blockdev/ramdisk.txt.
2165 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2166 See Documentation/blockdev/ramdisk.txt.
2168 rcupdate.blimit= [KNL,BOOT]
2169 Set maximum number of finished RCU callbacks to process
2170 in one batch.
2172 rcupdate.qhimark= [KNL,BOOT]
2173 Set threshold of queued
2174 RCU callbacks over which batch limiting is disabled.
2176 rcupdate.qlowmark= [KNL,BOOT]
2177 Set threshold of queued RCU callbacks below which
2178 batch limiting is re-enabled.
2180 rdinit= [KNL]
2181 Format: <full_path>
2182 Run specified binary instead of /init from the ramdisk,
2183 used for early userspace startup. See initrd.
2185 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2186 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2187 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2189 relax_domain_level=
2190 [KNL, SMP] Set scheduler's default relax_domain_level.
2191 See Documentation/cgroups/cpusets.txt.
2193 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2195 reservetop= [X86-32]
2196 Format: nn[KMG]
2197 Reserves a hole at the top of the kernel virtual
2198 address space.
2200 reservelow= [X86]
2201 Format: nn[K]
2202 Set the amount of memory to reserve for BIOS at
2203 the bottom of the address space.
2205 reset_devices [KNL] Force drivers to reset the underlying device
2206 during initialization.
2208 resume= [SWSUSP]
2209 Specify the partition device for software suspend
2211 resume_offset= [SWSUSP]
2212 Specify the offset from the beginning of the partition
2213 given by "resume=" at which the swap header is located,
2214 in <PAGE_SIZE> units (needed only for swap files).
2215 See Documentation/power/swsusp-and-swap-files.txt
2217 hibernate= [HIBERNATION]
2218 noresume Don't check if there's a hibernation image
2219 present during boot.
2220 nocompress Don't compress/decompress hibernation images.
2222 retain_initrd [RAM] Keep initrd memory after extraction
2224 rhash_entries= [KNL,NET]
2225 Set number of hash buckets for route cache
2227 riscom8= [HW,SERIAL]
2228 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2230 ro [KNL] Mount root device read-only on boot
2232 root= [KNL] Root filesystem
2234 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2235 mount the root filesystem
2237 rootflags= [KNL] Set root filesystem mount option string
2239 rootfstype= [KNL] Set root filesystem type
2241 rootwait [KNL] Wait (indefinitely) for root device to show up.
2242 Useful for devices that are detected asynchronously
2243 (e.g. USB and MMC devices).
2245 rw [KNL] Mount root device read-write on boot
2247 S [KNL] Run init in single mode
2249 sa1100ir [NET]
2250 See drivers/net/irda/sa1100_ir.c.
2252 sbni= [NET] Granch SBNI12 leased line adapter
2254 sched_debug [KNL] Enables verbose scheduler debug messages.
2256 security= [SECURITY] Choose a security module to enable at boot.
2257 If this boot parameter is not specified, only the first
2258 security module asking for security registration will be
2259 loaded. An invalid security module name will be treated
2260 as if no module has been chosen.
2262 selinux= [SELINUX] Disable or enable SELinux at boot time.
2263 Format: { "0" | "1" }
2264 See security/selinux/Kconfig help text.
2265 0 -- disable.
2266 1 -- enable.
2267 Default value is set via kernel config option.
2268 If enabled at boot time, /selinux/disable can be used
2269 later to disable prior to initial policy load.
2271 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2272 Format: { "0" | "1" }
2273 See security/apparmor/Kconfig help text
2274 0 -- disable.
2275 1 -- enable.
2276 Default value is set via kernel config option.
2278 serialnumber [BUGS=X86-32]
2280 shapers= [NET]
2281 Maximal number of shapers.
2283 show_msr= [x86] show boot-time MSR settings
2284 Format: { <integer> }
2285 Show boot-time (BIOS-initialized) MSR settings.
2286 The parameter means the number of CPUs to show,
2287 for example 1 means boot CPU only.
2289 simeth= [IA-64]
2290 simscsi=
2292 slram= [HW,MTD]
2294 slub_debug[=options[,slabs]] [MM, SLUB]
2295 Enabling slub_debug allows one to determine the
2296 culprit if slab objects become corrupted. Enabling
2297 slub_debug can create guard zones around objects and
2298 may poison objects when not in use. Also tracks the
2299 last alloc / free. For more information see
2300 Documentation/vm/slub.txt.
2302 slub_max_order= [MM, SLUB]
2303 Determines the maximum allowed order for slabs.
2304 A high setting may cause OOMs due to memory
2305 fragmentation. For more information see
2306 Documentation/vm/slub.txt.
2308 slub_min_objects= [MM, SLUB]
2309 The minimum number of objects per slab. SLUB will
2310 increase the slab order up to slub_max_order to
2311 generate a sufficiently large slab able to contain
2312 the number of objects indicated. The higher the number
2313 of objects the smaller the overhead of tracking slabs
2314 and the less frequently locks need to be acquired.
2315 For more information see Documentation/vm/slub.txt.
2317 slub_min_order= [MM, SLUB]
2318 Determines the mininum page order for slabs. Must be
2319 lower than slub_max_order.
2320 For more information see Documentation/vm/slub.txt.
2322 slub_nomerge [MM, SLUB]
2323 Disable merging of slabs with similar size. May be
2324 necessary if there is some reason to distinguish
2325 allocs to different slabs. Debug options disable
2326 merging on their own.
2327 For more information see Documentation/vm/slub.txt.
2329 smart2= [HW]
2330 Format: <io1>[,<io2>[,...,<io8>]]
2332 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2333 attempt to substitute SMP alternatives once at boot.
2335 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2336 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2337 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2338 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2339 smsc-ircc2.ircc_irq= [HW] IRQ line
2340 smsc-ircc2.ircc_dma= [HW] DMA channel
2341 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2342 0: Toshiba Satellite 1800 (GP data pin select)
2343 1: Fast pin select (default)
2344 2: ATC IRMode
2346 softlockup_panic=
2347 [KNL] Should the soft-lockup detector generate panics.
2348 Format: <integer>
2350 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2351 See Documentation/sonypi.txt
2353 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2354 See Documentation/serial/specialix.txt.
2356 spia_io_base= [HW,MTD]
2357 spia_fio_base=
2358 spia_pedr=
2359 spia_peddr=
2361 stacktrace [FTRACE]
2362 Enabled the stack tracer on boot up.
2364 sti= [PARISC,HW]
2365 Format: <num>
2366 Set the STI (builtin display/keyboard on the HP-PARISC
2367 machines) console (graphic card) which should be used
2368 as the initial boot-console.
2369 See also comment in drivers/video/console/sticore.c.
2371 sti_font= [HW]
2372 See comment in drivers/video/console/sticore.c.
2374 stifb= [HW]
2375 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2377 sunrpc.min_resvport=
2378 sunrpc.max_resvport=
2379 [NFS,SUNRPC]
2380 SunRPC servers often require that client requests
2381 originate from a privileged port (i.e. a port in the
2382 range 0 < portnr < 1024).
2383 An administrator who wishes to reserve some of these
2384 ports for other uses may adjust the range that the
2385 kernel's sunrpc client considers to be privileged
2386 using these two parameters to set the minimum and
2387 maximum port values.
2389 sunrpc.pool_mode=
2390 [NFS]
2391 Control how the NFS server code allocates CPUs to
2392 service thread pools. Depending on how many NICs
2393 you have and where their interrupts are bound, this
2394 option will affect which CPUs will do NFS serving.
2395 Note: this parameter cannot be changed while the
2396 NFS server is running.
2398 auto the server chooses an appropriate mode
2399 automatically using heuristics
2400 global a single global pool contains all CPUs
2401 percpu one pool for each CPU
2402 pernode one pool for each NUMA node (equivalent
2403 to global on non-NUMA machines)
2405 sunrpc.tcp_slot_table_entries=
2406 sunrpc.udp_slot_table_entries=
2407 [NFS,SUNRPC]
2408 Sets the upper limit on the number of simultaneous
2409 RPC calls that can be sent from the client to a
2410 server. Increasing these values may allow you to
2411 improve throughput, but will also increase the
2412 amount of memory reserved for use by the client.
2414 swapaccount[=0|1]
2415 [KNL] Enable accounting of swap in memory resource
2416 controller if no parameter or 1 is given or disable
2417 it if 0 is given (See Documentation/cgroups/memory.txt)
2419 swiotlb= [IA-64] Number of I/O TLB slabs
2421 switches= [HW,M68k]
2423 sysfs.deprecated=0|1 [KNL]
2424 Enable/disable old style sysfs layout for old udev
2425 on older distributions. When this option is enabled
2426 very new udev will not work anymore. When this option
2427 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2428 in older udev will not work anymore.
2429 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2430 the kernel configuration.
2432 sysrq_always_enabled
2433 [KNL]
2434 Ignore sysrq setting - this boot parameter will
2435 neutralize any effect of /proc/sys/kernel/sysrq.
2436 Useful for debugging.
2438 tdfx= [HW,DRM]
2440 test_suspend= [SUSPEND]
2441 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2442 standby suspend) as the system sleep state to briefly
2443 enter during system startup. The system is woken from
2444 this state using a wakeup-capable RTC alarm.
2446 thash_entries= [KNL,NET]
2447 Set number of hash buckets for TCP connection
2449 thermal.act= [HW,ACPI]
2450 -1: disable all active trip points in all thermal zones
2451 <degrees C>: override all lowest active trip points
2453 thermal.crt= [HW,ACPI]
2454 -1: disable all critical trip points in all thermal zones
2455 <degrees C>: override all critical trip points
2457 thermal.nocrt= [HW,ACPI]
2458 Set to disable actions on ACPI thermal zone
2459 critical and hot trip points.
2461 thermal.off= [HW,ACPI]
2462 1: disable ACPI thermal control
2464 thermal.psv= [HW,ACPI]
2465 -1: disable all passive trip points
2466 <degrees C>: override all passive trip points to this
2467 value
2469 thermal.tzp= [HW,ACPI]
2470 Specify global default ACPI thermal zone polling rate
2471 <deci-seconds>: poll all this frequency
2472 0: no polling (default)
2474 threadirqs [KNL]
2475 Force threading of all interrupt handlers except those
2476 marked explicitely IRQF_NO_THREAD.
2478 topology= [S390]
2479 Format: {off | on}
2480 Specify if the kernel should make use of the cpu
2481 topology information if the hardware supports this.
2482 The scheduler will make use of this information and
2483 e.g. base its process migration decisions on it.
2484 Default is on.
2486 tp720= [HW,PS2]
2488 tpm_suspend_pcr=[HW,TPM]
2489 Format: integer pcr id
2490 Specify that at suspend time, the tpm driver
2491 should extend the specified pcr with zeros,
2492 as a workaround for some chips which fail to
2493 flush the last written pcr on TPM_SaveState.
2494 This will guarantee that all the other pcrs
2495 are saved.
2497 trace_buf_size=nn[KMG]
2498 [FTRACE] will set tracing buffer size.
2500 trace_event=[event-list]
2501 [FTRACE] Set and start specified trace events in order
2502 to facilitate early boot debugging.
2503 See also Documentation/trace/events.txt
2505 tsc= Disable clocksource stability checks for TSC.
2506 Format: <string>
2507 [x86] reliable: mark tsc clocksource as reliable, this
2508 disables clocksource verification at runtime, as well
2509 as the stability checks done at bootup. Used to enable
2510 high-resolution timer mode on older hardware, and in
2511 virtualized environment.
2512 [x86] noirqtime: Do not use TSC to do irq accounting.
2513 Used to run time disable IRQ_TIME_ACCOUNTING on any
2514 platforms where RDTSC is slow and this accounting
2515 can add overhead.
2517 turbografx.map[2|3]= [HW,JOY]
2518 TurboGraFX parallel port interface
2519 Format:
2520 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2521 See also Documentation/input/joystick-parport.txt
2523 uhash_entries= [KNL,NET]
2524 Set number of hash buckets for UDP/UDP-Lite connections
2526 uhci-hcd.ignore_oc=
2527 [USB] Ignore overcurrent events (default N).
2528 Some badly-designed motherboards generate lots of
2529 bogus events, for ports that aren't wired to
2530 anything. Set this parameter to avoid log spamming.
2531 Note that genuine overcurrent events won't be
2532 reported either.
2534 unknown_nmi_panic
2535 [X86] Cause panic on unknown NMI.
2537 usbcore.autosuspend=
2538 [USB] The autosuspend time delay (in seconds) used
2539 for newly-detected USB devices (default 2). This
2540 is the time required before an idle device will be
2541 autosuspended. Devices for which the delay is set
2542 to a negative value won't be autosuspended at all.
2544 usbcore.usbfs_snoop=
2545 [USB] Set to log all usbfs traffic (default 0 = off).
2547 usbcore.blinkenlights=
2548 [USB] Set to cycle leds on hubs (default 0 = off).
2550 usbcore.old_scheme_first=
2551 [USB] Start with the old device initialization
2552 scheme (default 0 = off).
2554 usbcore.use_both_schemes=
2555 [USB] Try the other device initialization scheme
2556 if the first one fails (default 1 = enabled).
2558 usbcore.initial_descriptor_timeout=
2559 [USB] Specifies timeout for the initial 64-byte
2560 USB_REQ_GET_DESCRIPTOR request in milliseconds
2561 (default 5000 = 5.0 seconds).
2563 usbhid.mousepoll=
2564 [USBHID] The interval which mice are to be polled at.
2566 usb-storage.delay_use=
2567 [UMS] The delay in seconds before a new device is
2568 scanned for Logical Units (default 5).
2570 usb-storage.quirks=
2571 [UMS] A list of quirks entries to supplement or
2572 override the built-in unusual_devs list. List
2573 entries are separated by commas. Each entry has
2574 the form VID:PID:Flags where VID and PID are Vendor
2575 and Product ID values (4-digit hex numbers) and
2576 Flags is a set of characters, each corresponding
2577 to a common usb-storage quirk flag as follows:
2578 a = SANE_SENSE (collect more than 18 bytes
2579 of sense data);
2580 b = BAD_SENSE (don't collect more than 18
2581 bytes of sense data);
2582 c = FIX_CAPACITY (decrease the reported
2583 device capacity by one sector);
2584 h = CAPACITY_HEURISTICS (decrease the
2585 reported device capacity by one
2586 sector if the number is odd);
2587 i = IGNORE_DEVICE (don't bind to this
2588 device);
2589 l = NOT_LOCKABLE (don't try to lock and
2590 unlock ejectable media);
2591 m = MAX_SECTORS_64 (don't transfer more
2592 than 64 sectors = 32 KB at a time);
2593 o = CAPACITY_OK (accept the capacity
2594 reported by the device);
2595 r = IGNORE_RESIDUE (the device reports
2596 bogus residue values);
2597 s = SINGLE_LUN (the device has only one
2598 Logical Unit);
2599 w = NO_WP_DETECT (don't test whether the
2600 medium is write-protected).
2601 Example: quirks=0419:aaf5:rl,0421:0433:rc
2603 userpte=
2604 [X86] Flags controlling user PTE allocations.
2606 nohigh = do not allocate PTE pages in
2607 HIGHMEM regardless of setting
2608 of CONFIG_HIGHPTE.
2610 vdso= [X86,SH]
2611 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2612 vdso=1: enable VDSO (default)
2613 vdso=0: disable VDSO mapping
2615 vdso32= [X86]
2616 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2617 vdso32=1: enable 32-bit VDSO (default)
2618 vdso32=0: disable 32-bit VDSO mapping
2620 vector= [IA-64,SMP]
2621 vector=percpu: enable percpu vector domain
2623 video= [FB] Frame buffer configuration
2624 See Documentation/fb/modedb.txt.
2626 vga= [BOOT,X86-32] Select a particular video mode
2627 See Documentation/x86/boot.txt and
2628 Documentation/svga.txt.
2629 Use vga=ask for menu.
2630 This is actually a boot loader parameter; the value is
2631 passed to the kernel using a special protocol.
2633 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2634 size of <nn>. This can be used to increase the
2635 minimum size (128MB on x86). It can also be used to
2636 decrease the size and leave more room for directly
2637 mapped kernel RAM.
2639 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2640 Format: <command>
2642 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2643 Format: <command>
2645 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2646 Format: <command>
2648 vt.cur_default= [VT] Default cursor shape.
2649 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2650 the parameters of the <Esc>[?A;B;Cc escape sequence;
2651 see VGA-softcursor.txt. Default: 2 = underline.
2653 vt.default_blu= [VT]
2654 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2655 Change the default blue palette of the console.
2656 This is a 16-member array composed of values
2657 ranging from 0-255.
2659 vt.default_grn= [VT]
2660 Format: <green0>,<green1>,<green2>,...,<green15>
2661 Change the default green palette of the console.
2662 This is a 16-member array composed of values
2663 ranging from 0-255.
2665 vt.default_red= [VT]
2666 Format: <red0>,<red1>,<red2>,...,<red15>
2667 Change the default red palette of the console.
2668 This is a 16-member array composed of values
2669 ranging from 0-255.
2671 vt.default_utf8=
2672 [VT]
2673 Format=<0|1>
2674 Set system-wide default UTF-8 mode for all tty's.
2675 Default is 1, i.e. UTF-8 mode is enabled for all
2676 newly opened terminals.
2678 vt.global_cursor_default=
2679 [VT]
2680 Format=<-1|0|1>
2681 Set system-wide default for whether a cursor
2682 is shown on new VTs. Default is -1,
2683 i.e. cursors will be created by default unless
2684 overridden by individual drivers. 0 will hide
2685 cursors, 1 will display them.
2687 watchdog timers [HW,WDT] For information on watchdog timers,
2688 see Documentation/watchdog/watchdog-parameters.txt
2689 or other driver-specific files in the
2690 Documentation/watchdog/ directory.
2692 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2693 default x2apic cluster mode on platforms
2694 supporting x2apic.
2696 x86_mrst_timer= [X86-32,APBT]
2697 Choose timer option for x86 Moorestown MID platform.
2698 Two valid options are apbt timer only and lapic timer
2699 plus one apbt timer for broadcast timer.
2700 x86_mrst_timer=apbt_only | lapic_and_apbt
2702 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2703 xd_geo= See header of drivers/block/xd.c.
2705 xen_emul_unplug= [HW,X86,XEN]
2706 Unplug Xen emulated devices
2707 Format: [unplug0,][unplug1]
2708 ide-disks -- unplug primary master IDE devices
2709 aux-ide-disks -- unplug non-primary-master IDE devices
2710 nics -- unplug network devices
2711 all -- unplug all emulated devices (NICs and IDE disks)
2712 unnecessary -- unplugging emulated devices is
2713 unnecessary even if the host did not respond to
2714 the unplug protocol
2715 never -- do not unplug even if version check succeeds
2717 xirc2ps_cs= [NET,PCMCIA]
2718 Format:
2719 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2721 ______________________________________________________________________
2723 TODO:
2725 Add more DRM drivers.