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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 desgined 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 i2c_bus= [HW] Override the default board specific I2C bus speed
876 or register an additional I2C bus that is not
877 registered from board initialization code.
878 Format:
879 <bus_id>,<clkrate>
881 i8042.debug [HW] Toggle i8042 debug mode
882 i8042.direct [HW] Put keyboard port into non-translated mode
883 i8042.dumbkbd [HW] Pretend that controller can only read data from
884 keyboard and cannot control its state
885 (Don't attempt to blink the leds)
886 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
887 i8042.nokbd [HW] Don't check/create keyboard port
888 i8042.noloop [HW] Disable the AUX Loopback command while probing
889 for the AUX port
890 i8042.nomux [HW] Don't check presence of an active multiplexing
891 controller
892 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
893 controllers
894 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
895 i8042.reset [HW] Reset the controller during init and cleanup
896 i8042.unlock [HW] Unlock (ignore) the keylock
898 i810= [HW,DRM]
900 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
901 indicates that the driver is running on unsupported
902 hardware.
903 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
904 does not match list of supported models.
905 i8k.power_status
906 [HW] Report power status in /proc/i8k
907 (disabled by default)
908 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
909 capability is set.
911 icn= [HW,ISDN]
912 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
914 ide-core.nodma= [HW] (E)IDE subsystem
915 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
916 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
917 .cdrom .chs .ignore_cable are additional options
918 See Documentation/ide/ide.txt.
920 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
921 Claim all unknown PCI IDE storage controllers.
923 idle= [X86]
924 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
925 Poll forces a polling idle loop that can slightly
926 improve the performance of waking up a idle CPU, but
927 will use a lot of power and make the system run hot.
928 Not recommended.
929 idle=mwait: On systems which support MONITOR/MWAIT but
930 the kernel chose to not use it because it doesn't save
931 as much power as a normal idle loop, use the
932 MONITOR/MWAIT idle loop anyways. Performance should be
933 the same as idle=poll.
934 idle=halt: Halt is forced to be used for CPU idle.
935 In such case C2/C3 won't be used again.
936 idle=nomwait: Disable mwait for CPU C-states
938 ignore_loglevel [KNL]
939 Ignore loglevel setting - this will print /all/
940 kernel messages to the console. Useful for debugging.
942 ihash_entries= [KNL]
943 Set number of hash buckets for inode cache.
945 ima_audit= [IMA]
946 Format: { "0" | "1" }
947 0 -- integrity auditing messages. (Default)
948 1 -- enable informational integrity auditing messages.
950 ima_hash= [IMA]
951 Format: { "sha1" | "md5" }
952 default: "sha1"
954 ima_tcb [IMA]
955 Load a policy which meets the needs of the Trusted
956 Computing Base. This means IMA will measure all
957 programs exec'd, files mmap'd for exec, and all files
958 opened for read by uid=0.
960 init= [KNL]
961 Format: <full_path>
962 Run specified binary instead of /sbin/init as init
963 process.
965 initcall_debug [KNL] Trace initcalls as they are executed. Useful
966 for working out where the kernel is dying during
967 startup.
969 initrd= [BOOT] Specify the location of the initial ramdisk
971 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
972 Format: <irq>
974 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
975 on
976 Enable intel iommu driver.
977 off
978 Disable intel iommu driver.
979 igfx_off [Default Off]
980 By default, gfx is mapped as normal device. If a gfx
981 device has a dedicated DMAR unit, the DMAR unit is
982 bypassed by not enabling DMAR with this option. In
983 this case, gfx device will use physical address for
984 DMA.
985 forcedac [x86_64]
986 With this option iommu will not optimize to look
987 for io virtual address below 32 bit forcing dual
988 address cycle on pci bus for cards supporting greater
989 than 32 bit addressing. The default is to look
990 for translation below 32 bit and if not available
991 then look in the higher range.
992 strict [Default Off]
993 With this option on every unmap_single operation will
994 result in a hardware IOTLB flush operation as opposed
995 to batching them for performance.
997 intremap= [X86-64, Intel-IOMMU]
998 Format: { on (default) | off | nosid }
999 on enable Interrupt Remapping (default)
1000 off disable Interrupt Remapping
1001 nosid disable Source ID checking
1003 inttest= [IA64]
1005 iomem= Disable strict checking of access to MMIO memory
1006 strict regions from userspace.
1007 relaxed
1009 iommu= [x86]
1010 off
1011 force
1012 noforce
1013 biomerge
1014 panic
1015 nopanic
1016 merge
1017 nomerge
1018 forcesac
1019 soft
1020 pt [x86, IA64]
1022 io7= [HW] IO7 for Marvel based alpha systems
1023 See comment before marvel_specify_io7 in
1024 arch/alpha/kernel/core_marvel.c.
1026 io_delay= [X86] I/O delay method
1027 0x80
1028 Standard port 0x80 based delay
1029 0xed
1030 Alternate port 0xed based delay (needed on some systems)
1031 udelay
1032 Simple two microseconds delay
1033 none
1034 No delay
1036 ip= [IP_PNP]
1037 See Documentation/filesystems/nfs/nfsroot.txt.
1039 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1040 See comment before ip2_setup() in
1041 drivers/char/ip2/ip2base.c.
1043 irqfixup [HW]
1044 When an interrupt is not handled search all handlers
1045 for it. Intended to get systems with badly broken
1046 firmware running.
1048 irqpoll [HW]
1049 When an interrupt is not handled search all handlers
1050 for it. Also check all handlers each timer
1051 interrupt. Intended to get systems with badly broken
1052 firmware running.
1054 isapnp= [ISAPNP]
1055 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1057 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1058 Format:
1059 <cpu number>,...,<cpu number>
1060 or
1061 <cpu number>-<cpu number>
1062 (must be a positive range in ascending order)
1063 or a mixture
1064 <cpu number>,...,<cpu number>-<cpu number>
1066 This option can be used to specify one or more CPUs
1067 to isolate from the general SMP balancing and scheduling
1068 algorithms. You can move a process onto or off an
1069 "isolated" CPU via the CPU affinity syscalls or cpuset.
1070 <cpu number> begins at 0 and the maximum value is
1071 "number of CPUs in system - 1".
1073 This option is the preferred way to isolate CPUs. The
1074 alternative -- manually setting the CPU mask of all
1075 tasks in the system -- can cause problems and
1076 suboptimal load balancer performance.
1078 iucv= [HW,NET]
1080 js= [HW,JOY] Analog joystick
1081 See Documentation/input/joystick.txt.
1083 keepinitrd [HW,ARM]
1085 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1086 specifies the amount of memory usable by the kernel
1087 for non-movable allocations. The requested amount is
1088 spread evenly throughout all nodes in the system. The
1089 remaining memory in each node is used for Movable
1090 pages. In the event, a node is too small to have both
1091 kernelcore and Movable pages, kernelcore pages will
1092 take priority and other nodes will have a larger number
1093 of kernelcore pages. The Movable zone is used for the
1094 allocation of pages that may be reclaimed or moved
1095 by the page migration subsystem. This means that
1096 HugeTLB pages may not be allocated from this zone.
1097 Note that allocations like PTEs-from-HighMem still
1098 use the HighMem zone if it exists, and the Normal
1099 zone if it does not.
1101 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1102 Format: <Controller#>[,poll interval]
1103 The controller # is the number of the ehci usb debug
1104 port as it is probed via PCI. The poll interval is
1105 optional and is the number seconds in between
1106 each poll cycle to the debug port in case you need
1107 the functionality for interrupting the kernel with
1108 gdb or control-c on the dbgp connection. When
1109 not using this parameter you use sysrq-g to break into
1110 the kernel debugger.
1112 kgdboc= [KGDB,HW] kgdb over consoles.
1113 Requires a tty driver that supports console polling,
1114 or a supported polling keyboard driver (non-usb).
1115 Serial only format: <serial_device>[,baud]
1116 keyboard only format: kbd
1117 keyboard and serial format: kbd,<serial_device>[,baud]
1118 Optional Kernel mode setting:
1119 kms, kbd format: kms,kbd
1120 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1122 kgdbwait [KGDB] Stop kernel execution and enter the
1123 kernel debugger at the earliest opportunity.
1125 kmac= [MIPS] korina ethernet MAC address.
1126 Configure the RouterBoard 532 series on-chip
1127 Ethernet adapter MAC address.
1129 kmemleak= [KNL] Boot-time kmemleak enable/disable
1130 Valid arguments: on, off
1131 Default: on
1133 kstack=N [X86] Print N words from the kernel stack
1134 in oops dumps.
1136 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1137 Default is 0 (don't ignore, but inject #GP)
1139 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1140 Default is 1 (enabled)
1142 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1143 KVM MMU at runtime.
1144 Default is 0 (off)
1146 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1147 Default is 1 (enabled)
1149 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1150 for all guests.
1151 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1153 kvm-intel.bypass_guest_pf=
1154 [KVM,Intel] Disables bypassing of guest page faults
1155 on Intel chips. Default is 1 (enabled)
1157 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1158 (virtualized MMU) support on capable Intel chips.
1159 Default is 1 (enabled)
1161 kvm-intel.emulate_invalid_guest_state=
1162 [KVM,Intel] Enable emulation of invalid guest states
1163 Default is 0 (disabled)
1165 kvm-intel.flexpriority=
1166 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1167 Default is 1 (enabled)
1169 kvm-intel.unrestricted_guest=
1170 [KVM,Intel] Disable unrestricted guest feature
1171 (virtualized real and unpaged mode) on capable
1172 Intel chips. Default is 1 (enabled)
1174 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1175 feature (tagged TLBs) on capable Intel chips.
1176 Default is 1 (enabled)
1178 l2cr= [PPC]
1180 l3cr= [PPC]
1182 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1183 disabled it.
1185 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1186 in C2 power state.
1188 libata.dma= [LIBATA] DMA control
1189 libata.dma=0 Disable all PATA and SATA DMA
1190 libata.dma=1 PATA and SATA Disk DMA only
1191 libata.dma=2 ATAPI (CDROM) DMA only
1192 libata.dma=4 Compact Flash DMA only
1193 Combinations also work, so libata.dma=3 enables DMA
1194 for disks and CDROMs, but not CFs.
1196 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1197 libata.ignore_hpa=0 keep BIOS limits (default)
1198 libata.ignore_hpa=1 ignore limits, using full disk
1200 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1201 when set.
1202 Format: <int>
1204 libata.force= [LIBATA] Force configurations. The format is comma
1205 separated list of "[ID:]VAL" where ID is
1206 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1207 matching port, link or device. Basically, it matches
1208 the ATA ID string printed on console by libata. If
1209 the whole ID part is omitted, the last PORT and DEVICE
1210 values are used. If ID hasn't been specified yet, the
1211 configuration applies to all ports, links and devices.
1213 If only DEVICE is omitted, the parameter applies to
1214 the port and all links and devices behind it. DEVICE
1215 number of 0 either selects the first device or the
1216 first fan-out link behind PMP device. It does not
1217 select the host link. DEVICE number of 15 selects the
1218 host link and device attached to it.
1220 The VAL specifies the configuration to force. As long
1221 as there's no ambiguity shortcut notation is allowed.
1222 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1223 The following configurations can be forced.
1225 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1226 Any ID with matching PORT is used.
1228 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1230 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1231 udma[/][16,25,33,44,66,100,133] notation is also
1232 allowed.
1234 * [no]ncq: Turn on or off NCQ.
1236 * nohrst, nosrst, norst: suppress hard, soft
1237 and both resets.
1239 * dump_id: dump IDENTIFY data.
1241 If there are multiple matching configurations changing
1242 the same attribute, the last one is used.
1244 memblock=debug [KNL] Enable memblock debug messages.
1246 load_ramdisk= [RAM] List of ramdisks to load from floppy
1247 See Documentation/blockdev/ramdisk.txt.
1249 lockd.nlm_grace_period=P [NFS] Assign grace period.
1250 Format: <integer>
1252 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1253 Format: <integer>
1255 lockd.nlm_timeout=T [NFS] Assign timeout value.
1256 Format: <integer>
1258 lockd.nlm_udpport=M [NFS] Assign UDP port.
1259 Format: <integer>
1261 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1262 Format: <irq>
1264 loglevel= All Kernel Messages with a loglevel smaller than the
1265 console loglevel will be printed to the console. It can
1266 also be changed with klogd or other programs. The
1267 loglevels are defined as follows:
1269 0 (KERN_EMERG) system is unusable
1270 1 (KERN_ALERT) action must be taken immediately
1271 2 (KERN_CRIT) critical conditions
1272 3 (KERN_ERR) error conditions
1273 4 (KERN_WARNING) warning conditions
1274 5 (KERN_NOTICE) normal but significant condition
1275 6 (KERN_INFO) informational
1276 7 (KERN_DEBUG) debug-level messages
1278 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1279 in bytes. n must be a power of two. The default
1280 size is set in the kernel config file.
1282 logo.nologo [FB] Disables display of the built-in Linux logo.
1283 This may be used to provide more screen space for
1284 kernel log messages and is useful when debugging
1285 kernel boot problems.
1287 lp=0 [LP] Specify parallel ports to use, e.g,
1288 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1289 lp=reset first parallel port). 'lp=0' disables the
1290 lp=auto printer driver. 'lp=reset' (which can be
1291 specified in addition to the ports) causes
1292 attached printers to be reset. Using
1293 lp=port1,port2,... specifies the parallel ports
1294 to associate lp devices with, starting with
1295 lp0. A port specification may be 'none' to skip
1296 that lp device, or a parport name such as
1297 'parport0'. Specifying 'lp=auto' instead of a
1298 port specification list means that device IDs
1299 from each port should be examined, to see if
1300 an IEEE 1284-compliant printer is attached; if
1301 so, the driver will manage that printer.
1302 See also header of drivers/char/lp.c.
1304 lpj=n [KNL]
1305 Sets loops_per_jiffy to given constant, thus avoiding
1306 time-consuming boot-time autodetection (up to 250 ms per
1307 CPU). 0 enables autodetection (default). To determine
1308 the correct value for your kernel, boot with normal
1309 autodetection and see what value is printed. Note that
1310 on SMP systems the preset will be applied to all CPUs,
1311 which is likely to cause problems if your CPUs need
1312 significantly divergent settings. An incorrect value
1313 will cause delays in the kernel to be wrong, leading to
1314 unpredictable I/O errors and other breakage. Although
1315 unlikely, in the extreme case this might damage your
1316 hardware.
1318 ltpc= [NET]
1319 Format: <io>,<irq>,<dma>
1321 machvec= [IA64] Force the use of a particular machine-vector
1322 (machvec) in a generic kernel.
1323 Example: machvec=hpzx1_swiotlb
1325 machtype= [Loongson] Share the same kernel image file between different
1326 yeeloong laptop.
1327 Example: machtype=lemote-yeeloong-2f-7inch
1329 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1330 than or equal to this physical address is ignored.
1332 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1333 should make use of. maxcpus=n : n >= 0 limits the
1334 kernel to using 'n' processors. n=0 is a special case,
1335 it is equivalent to "nosmp", which also disables
1336 the IO APIC.
1338 max_loop= [LOOP] Maximum number of loopback devices that can
1339 be mounted
1340 Format: <1-256>
1342 mcatest= [IA-64]
1344 mce [X86-32] Machine Check Exception
1346 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1348 md= [HW] RAID subsystems devices and level
1349 See Documentation/md.txt.
1351 mdacon= [MDA]
1352 Format: <first>,<last>
1353 Specifies range of consoles to be captured by the MDA.
1355 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1356 Amount of memory to be used when the kernel is not able
1357 to see the whole system memory or for test.
1358 [X86-32] Use together with memmap= to avoid physical
1359 address space collisions. Without memmap= PCI devices
1360 could be placed at addresses belonging to unused RAM.
1362 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1363 memory.
1365 memchunk=nn[KMG]
1366 [KNL,SH] Allow user to override the default size for
1367 per-device physically contiguous DMA buffers.
1369 memmap=exactmap [KNL,X86] Enable setting of an exact
1370 E820 memory map, as specified by the user.
1371 Such memmap=exactmap lines can be constructed based on
1372 BIOS output or other requirements. See the memmap=nn@ss
1373 option description.
1375 memmap=nn[KMG]@ss[KMG]
1376 [KNL] Force usage of a specific region of memory
1377 Region of memory to be used, from ss to ss+nn.
1379 memmap=nn[KMG]#ss[KMG]
1380 [KNL,ACPI] Mark specific memory as ACPI data.
1381 Region of memory to be used, from ss to ss+nn.
1383 memmap=nn[KMG]$ss[KMG]
1384 [KNL,ACPI] Mark specific memory as reserved.
1385 Region of memory to be used, from ss to ss+nn.
1386 Example: Exclude memory from 0x18690000-0x1869ffff
1387 memmap=64K$0x18690000
1388 or
1389 memmap=0x10000$0x18690000
1391 memory_corruption_check=0/1 [X86]
1392 Some BIOSes seem to corrupt the first 64k of
1393 memory when doing things like suspend/resume.
1394 Setting this option will scan the memory
1395 looking for corruption. Enabling this will
1396 both detect corruption and prevent the kernel
1397 from using the memory being corrupted.
1398 However, its intended as a diagnostic tool; if
1399 repeatable BIOS-originated corruption always
1400 affects the same memory, you can use memmap=
1401 to prevent the kernel from using that memory.
1403 memory_corruption_check_size=size [X86]
1404 By default it checks for corruption in the low
1405 64k, making this memory unavailable for normal
1406 use. Use this parameter to scan for
1407 corruption in more or less memory.
1409 memory_corruption_check_period=seconds [X86]
1410 By default it checks for corruption every 60
1411 seconds. Use this parameter to check at some
1412 other rate. 0 disables periodic checking.
1414 memtest= [KNL,X86] Enable memtest
1415 Format: <integer>
1416 default : 0 <disable>
1417 Specifies the number of memtest passes to be
1418 performed. Each pass selects another test
1419 pattern from a given set of patterns. Memtest
1420 fills the memory with this pattern, validates
1421 memory contents and reserves bad memory
1422 regions that are detected.
1424 meye.*= [HW] Set MotionEye Camera parameters
1425 See Documentation/video4linux/meye.txt.
1427 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1428 Multi-Function General Purpose Timers on AMD Geode
1429 platforms.
1431 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1432 the BIOS has incorrectly applied a workaround. TinyBIOS
1433 version 0.98 is known to be affected, 0.99 fixes the
1434 problem by letting the user disable the workaround.
1436 mga= [HW,DRM]
1438 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1439 physical address is ignored.
1441 mini2440= [ARM,HW,KNL]
1442 Format:[0..2][b][c][t]
1443 Default: "0tb"
1444 MINI2440 configuration specification:
1445 0 - The attached screen is the 3.5" TFT
1446 1 - The attached screen is the 7" TFT
1447 2 - The VGA Shield is attached (1024x768)
1448 Leaving out the screen size parameter will not load
1449 the TFT driver, and the framebuffer will be left
1450 unconfigured.
1451 b - Enable backlight. The TFT backlight pin will be
1452 linked to the kernel VESA blanking code and a GPIO
1453 LED. This parameter is not necessary when using the
1454 VGA shield.
1455 c - Enable the s3c camera interface.
1456 t - Reserved for enabling touchscreen support. The
1457 touchscreen support is not enabled in the mainstream
1458 kernel as of 2.6.30, a preliminary port can be found
1459 in the "bleeding edge" mini2440 support kernel at
1460 http://repo.or.cz/w/linux-2.6/mini2440.git
1462 mminit_loglevel=
1463 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1464 parameter allows control of the logging verbosity for
1465 the additional memory initialisation checks. A value
1466 of 0 disables mminit logging and a level of 4 will
1467 log everything. Information is printed at KERN_DEBUG
1468 so loglevel=8 may also need to be specified.
1470 mousedev.tap_time=
1471 [MOUSE] Maximum time between finger touching and
1472 leaving touchpad surface for touch to be considered
1473 a tap and be reported as a left button click (for
1474 touchpads working in absolute mode only).
1475 Format: <msecs>
1476 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1477 reporting absolute coordinates, such as tablets
1478 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1479 reporting absolute coordinates, such as tablets
1481 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1482 is similar to kernelcore except it specifies the
1483 amount of memory used for migratable allocations.
1484 If both kernelcore and movablecore is specified,
1485 then kernelcore will be at *least* the specified
1486 value but may be more. If movablecore on its own
1487 is specified, the administrator must be careful
1488 that the amount of memory usable for all allocations
1489 is not too small.
1491 MTD_Partition= [MTD]
1492 Format: <name>,<region-number>,<size>,<offset>
1494 MTD_Region= [MTD] Format:
1495 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1497 mtdparts= [MTD]
1498 See drivers/mtd/cmdlinepart.c.
1500 multitce=off [PPC] This parameter disables the use of the pSeries
1501 firmware feature for updating multiple TCE entries
1502 at a time.
1504 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1506 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1508 boundary - index of last SLC block on Flex-OneNAND.
1509 The remaining blocks are configured as MLC blocks.
1510 lock - Configure if Flex-OneNAND boundary should be locked.
1511 Once locked, the boundary cannot be changed.
1512 1 indicates lock status, 0 indicates unlock status.
1514 mtdset= [ARM]
1515 ARM/S3C2412 JIVE boot control
1517 See arch/arm/mach-s3c2412/mach-jive.c
1519 mtouchusb.raw_coordinates=
1520 [HW] Make the MicroTouch USB driver use raw coordinates
1521 ('y', default) or cooked coordinates ('n')
1523 mtrr_chunk_size=nn[KMG] [X86]
1524 used for mtrr cleanup. It is largest continuous chunk
1525 that could hold holes aka. UC entries.
1527 mtrr_gran_size=nn[KMG] [X86]
1528 Used for mtrr cleanup. It is granularity of mtrr block.
1529 Default is 1.
1530 Large value could prevent small alignment from
1531 using up MTRRs.
1533 mtrr_spare_reg_nr=n [X86]
1534 Format: <integer>
1535 Range: 0,7 : spare reg number
1536 Default : 1
1537 Used for mtrr cleanup. It is spare mtrr entries number.
1538 Set to 2 or more if your graphical card needs more.
1540 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1542 netdev= [NET] Network devices parameters
1543 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1544 Note that mem_start is often overloaded to mean
1545 something different and driver-specific.
1546 This usage is only documented in each driver source
1547 file if at all.
1549 nf_conntrack.acct=
1550 [NETFILTER] Enable connection tracking flow accounting
1551 0 to disable accounting
1552 1 to enable accounting
1553 Default value is 0.
1555 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1556 See Documentation/filesystems/nfs/nfsroot.txt.
1558 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1559 See Documentation/filesystems/nfs/nfsroot.txt.
1561 nfsrootdebug [NFS] enable nfsroot debugging messages.
1562 See Documentation/filesystems/nfs/nfsroot.txt.
1564 nfs.callback_tcpport=
1565 [NFS] set the TCP port on which the NFSv4 callback
1566 channel should listen.
1568 nfs.cache_getent=
1569 [NFS] sets the pathname to the program which is used
1570 to update the NFS client cache entries.
1572 nfs.cache_getent_timeout=
1573 [NFS] sets the timeout after which an attempt to
1574 update a cache entry is deemed to have failed.
1576 nfs.idmap_cache_timeout=
1577 [NFS] set the maximum lifetime for idmapper cache
1578 entries.
1580 nfs.enable_ino64=
1581 [NFS] enable 64-bit inode numbers.
1582 If zero, the NFS client will fake up a 32-bit inode
1583 number for the readdir() and stat() syscalls instead
1584 of returning the full 64-bit number.
1585 The default is to return 64-bit inode numbers.
1587 nfs.nfs4_disable_idmapping=
1588 [NFSv4] When set, this option disables the NFSv4
1589 idmapper on the client, but only if the mount
1590 is using the 'sec=sys' security flavour. This may
1591 make migration from legacy NFSv2/v3 systems easier
1592 provided that the server has the appropriate support.
1593 The default is to always enable NFSv4 idmapping.
1595 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1596 when a NMI is triggered.
1597 Format: [state][,regs][,debounce][,die]
1599 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1600 Format: [panic,][num]
1601 Valid num: 0
1602 0 - turn nmi_watchdog off
1603 When panic is specified, panic when an NMI watchdog
1604 timeout occurs.
1605 This is useful when you use a panic=... timeout and
1606 need the box quickly up again.
1608 netpoll.carrier_timeout=
1609 [NET] Specifies amount of time (in seconds) that
1610 netpoll should wait for a carrier. By default netpoll
1611 waits 4 seconds.
1613 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1614 emulation library even if a 387 maths coprocessor
1615 is present.
1617 no_console_suspend
1618 [HW] Never suspend the console
1619 Disable suspending of consoles during suspend and
1620 hibernate operations. Once disabled, debugging
1621 messages can reach various consoles while the rest
1622 of the system is being put to sleep (ie, while
1623 debugging driver suspend/resume hooks). This may
1624 not work reliably with all consoles, but is known
1625 to work with serial and VGA consoles.
1627 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1628 caches in the slab allocator. Saves per-node memory,
1629 but will impact performance.
1631 noalign [KNL,ARM]
1633 noapic [SMP,APIC] Tells the kernel to not make use of any
1634 IOAPICs that may be present in the system.
1636 noautogroup Disable scheduler automatic task group creation.
1638 nobats [PPC] Do not use BATs for mapping kernel lowmem
1639 on "Classic" PPC cores.
1641 nocache [ARM]
1643 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1645 nodelayacct [KNL] Disable per-task delay accounting
1647 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1649 nodsp [SH] Disable hardware DSP at boot time.
1651 noefi [X86] Disable EFI runtime services support.
1653 noexec [IA-64]
1655 noexec [X86]
1656 On X86-32 available only on PAE configured kernels.
1657 noexec=on: enable non-executable mappings (default)
1658 noexec=off: disable non-executable mappings
1660 noexec32 [X86-64]
1661 This affects only 32-bit executables.
1662 noexec32=on: enable non-executable mappings (default)
1663 read doesn't imply executable mappings
1664 noexec32=off: disable non-executable mappings
1665 read implies executable mappings
1667 nofpu [SH] Disable hardware FPU at boot time.
1669 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1670 register save and restore. The kernel will only save
1671 legacy floating-point registers on task switch.
1673 noxsave [BUGS=X86] Disables x86 extended register state save
1674 and restore using xsave. The kernel will fallback to
1675 enabling legacy floating-point and sse state.
1677 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1678 wfi(ARM) instruction doesn't work correctly and not to
1679 use it. This is also useful when using JTAG debugger.
1681 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1682 instruction doesn't work correctly and not to
1683 use it.
1685 no_file_caps Tells the kernel not to honor file capabilities. The
1686 only way then for a file to be executed with privilege
1687 is to be setuid root or executed by root.
1689 nohalt [IA-64] Tells the kernel not to use the power saving
1690 function PAL_HALT_LIGHT when idle. This increases
1691 power-consumption. On the positive side, it reduces
1692 interrupt wake-up latency, which may improve performance
1693 in certain environments such as networked servers or
1694 real-time systems.
1696 nohz= [KNL] Boottime enable/disable dynamic ticks
1697 Valid arguments: on, off
1698 Default: on
1700 noiotrap [SH] Disables trapped I/O port accesses.
1702 noirqdebug [X86-32] Disables the code which attempts to detect and
1703 disable unhandled interrupt sources.
1705 no_timer_check [X86,APIC] Disables the code which tests for
1706 broken timer IRQ sources.
1708 noisapnp [ISAPNP] Disables ISA PnP code.
1710 noinitrd [RAM] Tells the kernel not to load any configured
1711 initial RAM disk.
1713 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1714 remapping.
1715 [Deprecated - use intremap=off]
1717 nointroute [IA-64]
1719 nojitter [IA64] Disables jitter checking for ITC timers.
1721 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1723 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1724 fault handling.
1726 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1728 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1730 noltlbs [PPC] Do not use large page/tlb entries for kernel
1731 lowmem mapping on PPC40x.
1733 nomca [IA-64] Disable machine check abort handling
1735 nomce [X86-32] Machine Check Exception
1737 nomfgpt [X86-32] Disable Multi-Function General Purpose
1738 Timer usage (for AMD Geode machines).
1740 nopat [X86] Disable PAT (page attribute table extension of
1741 pagetables) support.
1743 norandmaps Don't use address space randomization. Equivalent to
1744 echo 0 > /proc/sys/kernel/randomize_va_space
1746 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1748 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1749 with UP alternatives
1751 noresidual [PPC] Don't use residual data on PReP machines.
1753 noresume [SWSUSP] Disables resume and restores original swap
1754 space.
1756 no-scroll [VGA] Disables scrollback.
1757 This is required for the Braillex ib80-piezo Braille
1758 reader made by F.H. Papenmeier (Germany).
1760 nosbagart [IA-64]
1762 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1764 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1765 and disable the IO APIC. legacy for "maxcpus=0".
1767 nosoftlockup [KNL] Disable the soft-lockup detector.
1769 noswapaccount [KNL] Disable accounting of swap in memory resource
1770 controller. (See Documentation/cgroups/memory.txt)
1772 nosync [HW,M68K] Disables sync negotiation for all devices.
1774 notsc [BUGS=X86-32] Disable Time Stamp Counter
1776 nousb [USB] Disable the USB subsystem
1778 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1780 nowb [ARM]
1782 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1784 nptcg= [IA64] Override max number of concurrent global TLB
1785 purges which is reported from either PAL_VM_SUMMARY or
1786 SAL PALO.
1788 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1789 could support. nr_cpus=n : n >= 1 limits the kernel to
1790 supporting 'n' processors. Later in runtime you can not
1791 use hotplug cpu feature to put more cpu back to online.
1792 just like you compile the kernel NR_CPUS=n
1794 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1796 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1797 one of ['zone', 'node', 'default'] can be specified
1798 This can be set from sysctl after boot.
1799 See Documentation/sysctl/vm.txt for details.
1801 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1802 See Documentation/debugging-via-ohci1394.txt for more
1803 info.
1805 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1806 Rather than timing out after 20 ms if an EC
1807 command is not properly ACKed, override the length
1808 of the timeout. We have interrupts disabled while
1809 waiting for the ACK, so if this is set too high
1810 interrupts *may* be lost!
1812 omap_mux= [OMAP] Override bootloader pin multiplexing.
1813 Format: <mux_mode0.mode_name=value>...
1814 For example, to override I2C bus2:
1815 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1817 oprofile.timer= [HW]
1818 Use timer interrupt instead of performance counters
1820 oprofile.cpu_type= Force an oprofile cpu type
1821 This might be useful if you have an older oprofile
1822 userland or if you want common events.
1823 Format: { arch_perfmon }
1824 arch_perfmon: [X86] Force use of architectural
1825 perfmon on Intel CPUs instead of the
1826 CPU specific event set.
1828 OSS [HW,OSS]
1829 See Documentation/sound/oss/oss-parameters.txt
1831 panic= [KNL] Kernel behaviour on panic
1832 Format: <timeout>
1834 parkbd.port= [HW] Parallel port number the keyboard adapter is
1835 connected to, default is 0.
1836 Format: <parport#>
1837 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1838 0 for XT, 1 for AT (default is AT).
1839 Format: <mode>
1841 parport= [HW,PPT] Specify parallel ports. 0 disables.
1842 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1843 Use 'auto' to force the driver to use any
1844 IRQ/DMA settings detected (the default is to
1845 ignore detected IRQ/DMA settings because of
1846 possible conflicts). You can specify the base
1847 address, IRQ, and DMA settings; IRQ and DMA
1848 should be numbers, or 'auto' (for using detected
1849 settings on that particular port), or 'nofifo'
1850 (to avoid using a FIFO even if it is detected).
1851 Parallel ports are assigned in the order they
1852 are specified on the command line, starting
1853 with parport0.
1855 parport_init_mode= [HW,PPT]
1856 Configure VIA parallel port to operate in
1857 a specific mode. This is necessary on Pegasos
1858 computer where firmware has no options for setting
1859 up parallel port mode and sets it to spp.
1860 Currently this function knows 686a and 8231 chips.
1861 Format: [spp|ps2|epp|ecp|ecpepp]
1863 pause_on_oops=
1864 Halt all CPUs after the first oops has been printed for
1865 the specified number of seconds. This is to be used if
1866 your oopses keep scrolling off the screen.
1868 pcbit= [HW,ISDN]
1870 pcd. [PARIDE]
1871 See header of drivers/block/paride/pcd.c.
1872 See also Documentation/blockdev/paride.txt.
1874 pci=option[,option...] [PCI] various PCI subsystem options:
1875 earlydump [X86] dump PCI config space before the kernel
1876 changes anything
1877 off [X86] don't probe for the PCI bus
1878 bios [X86-32] force use of PCI BIOS, don't access
1879 the hardware directly. Use this if your machine
1880 has a non-standard PCI host bridge.
1881 nobios [X86-32] disallow use of PCI BIOS, only direct
1882 hardware access methods are allowed. Use this
1883 if you experience crashes upon bootup and you
1884 suspect they are caused by the BIOS.
1885 conf1 [X86] Force use of PCI Configuration
1886 Mechanism 1.
1887 conf2 [X86] Force use of PCI Configuration
1888 Mechanism 2.
1889 noaer [PCIE] If the PCIEAER kernel config parameter is
1890 enabled, this kernel boot option can be used to
1891 disable the use of PCIE advanced error reporting.
1892 nodomains [PCI] Disable support for multiple PCI
1893 root domains (aka PCI segments, in ACPI-speak).
1894 nommconf [X86] Disable use of MMCONFIG for PCI
1895 Configuration
1896 check_enable_amd_mmconf [X86] check for and enable
1897 properly configured MMIO access to PCI
1898 config space on AMD family 10h CPU
1899 nomsi [MSI] If the PCI_MSI kernel config parameter is
1900 enabled, this kernel boot option can be used to
1901 disable the use of MSI interrupts system-wide.
1902 noioapicquirk [APIC] Disable all boot interrupt quirks.
1903 Safety option to keep boot IRQs enabled. This
1904 should never be necessary.
1905 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1906 primary IO-APIC for bridges that cannot disable
1907 boot IRQs. This fixes a source of spurious IRQs
1908 when the system masks IRQs.
1909 noioapicreroute [APIC] Disable workaround that uses the
1910 boot IRQ equivalent of an IRQ that connects to
1911 a chipset where boot IRQs cannot be disabled.
1912 The opposite of ioapicreroute.
1913 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1914 routing table. These calls are known to be buggy
1915 on several machines and they hang the machine
1916 when used, but on other computers it's the only
1917 way to get the interrupt routing table. Try
1918 this option if the kernel is unable to allocate
1919 IRQs or discover secondary PCI buses on your
1920 motherboard.
1921 rom [X86] Assign address space to expansion ROMs.
1922 Use with caution as certain devices share
1923 address decoders between ROMs and other
1924 resources.
1925 norom [X86] Do not assign address space to
1926 expansion ROMs that do not already have
1927 BIOS assigned address ranges.
1928 nobar [X86] Do not assign address space to the
1929 BARs that weren't assigned by the BIOS.
1930 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1931 assigned automatically to PCI devices. You can
1932 make the kernel exclude IRQs of your ISA cards
1933 this way.
1934 pirqaddr=0xAAAAA [X86] Specify the physical address
1935 of the PIRQ table (normally generated
1936 by the BIOS) if it is outside the
1937 F0000h-100000h range.
1938 lastbus=N [X86] Scan all buses thru bus #N. Can be
1939 useful if the kernel is unable to find your
1940 secondary buses and you want to tell it
1941 explicitly which ones they are.
1942 assign-busses [X86] Always assign all PCI bus
1943 numbers ourselves, overriding
1944 whatever the firmware may have done.
1945 usepirqmask [X86] Honor the possible IRQ mask stored
1946 in the BIOS $PIR table. This is needed on
1947 some systems with broken BIOSes, notably
1948 some HP Pavilion N5400 and Omnibook XE3
1949 notebooks. This will have no effect if ACPI
1950 IRQ routing is enabled.
1951 noacpi [X86] Do not use ACPI for IRQ routing
1952 or for PCI scanning.
1953 use_crs [X86] Use PCI host bridge window information
1954 from ACPI. On BIOSes from 2008 or later, this
1955 is enabled by default. If you need to use this,
1956 please report a bug.
1957 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1958 If you need to use this, please report a bug.
1959 routeirq Do IRQ routing for all PCI devices.
1960 This is normally done in pci_enable_device(),
1961 so this option is a temporary workaround
1962 for broken drivers that don't call it.
1963 skip_isa_align [X86] do not align io start addr, so can
1964 handle more pci cards
1965 firmware [ARM] Do not re-enumerate the bus but instead
1966 just use the configuration from the
1967 bootloader. This is currently used on
1968 IXP2000 systems where the bus has to be
1969 configured a certain way for adjunct CPUs.
1970 noearly [X86] Don't do any early type 1 scanning.
1971 This might help on some broken boards which
1972 machine check when some devices' config space
1973 is read. But various workarounds are disabled
1974 and some IOMMU drivers will not work.
1975 bfsort Sort PCI devices into breadth-first order.
1976 This sorting is done to get a device
1977 order compatible with older (<= 2.4) kernels.
1978 nobfsort Don't sort PCI devices into breadth-first order.
1979 cbiosize=nn[KMG] The fixed amount of bus space which is
1980 reserved for the CardBus bridge's IO window.
1981 The default value is 256 bytes.
1982 cbmemsize=nn[KMG] The fixed amount of bus space which is
1983 reserved for the CardBus bridge's memory
1984 window. The default value is 64 megabytes.
1985 resource_alignment=
1986 Format:
1987 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1988 Specifies alignment and device to reassign
1989 aligned memory resources.
1990 If <order of align> is not specified,
1991 PAGE_SIZE is used as alignment.
1992 PCI-PCI bridge can be specified, if resource
1993 windows need to be expanded.
1994 ecrc= Enable/disable PCIe ECRC (transaction layer
1995 end-to-end CRC checking).
1996 bios: Use BIOS/firmware settings. This is the
1997 the default.
1998 off: Turn ECRC off
1999 on: Turn ECRC on.
2001 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2002 Management.
2003 off Disable ASPM.
2004 force Enable ASPM even on devices that claim not to support it.
2005 WARNING: Forcing ASPM on may cause system lockups.
2007 pcie_ports= [PCIE] PCIe ports handling:
2008 auto Ask the BIOS whether or not to use native PCIe services
2009 associated with PCIe ports (PME, hot-plug, AER). Use
2010 them only if that is allowed by the BIOS.
2011 native Use native PCIe services associated with PCIe ports
2012 unconditionally.
2013 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2014 ports driver.
2016 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2017 nomsi Do not use MSI for native PCIe PME signaling (this makes
2018 all PCIe root ports use INTx for all services).
2020 pcmv= [HW,PCMCIA] BadgePAD 4
2022 pd. [PARIDE]
2023 See Documentation/blockdev/paride.txt.
2025 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2026 boot time.
2027 Format: { 0 | 1 }
2028 See arch/parisc/kernel/pdc_chassis.c
2030 percpu_alloc= Select which percpu first chunk allocator to use.
2031 Currently supported values are "embed" and "page".
2032 Archs may support subset or none of the selections.
2033 See comments in mm/percpu.c for details on each
2034 allocator. This parameter is primarily for debugging
2035 and performance comparison.
2037 pf. [PARIDE]
2038 See Documentation/blockdev/paride.txt.
2040 pg. [PARIDE]
2041 See Documentation/blockdev/paride.txt.
2043 pirq= [SMP,APIC] Manual mp-table setup
2044 See Documentation/x86/i386/IO-APIC.txt.
2046 plip= [PPT,NET] Parallel port network link
2047 Format: { parport<nr> | timid | 0 }
2048 See also Documentation/parport.txt.
2050 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2051 Override pmtimer IOPort with a hex value.
2052 e.g. pmtmr=0x508
2054 pnp.debug [PNP]
2055 Enable PNP debug messages. This depends on the
2056 CONFIG_PNP_DEBUG_MESSAGES option.
2058 pnpacpi= [ACPI]
2059 { off }
2061 pnpbios= [ISAPNP]
2062 { on | off | curr | res | no-curr | no-res }
2064 pnp_reserve_irq=
2065 [ISAPNP] Exclude IRQs for the autoconfiguration
2067 pnp_reserve_dma=
2068 [ISAPNP] Exclude DMAs for the autoconfiguration
2070 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2071 Ranges are in pairs (I/O port base and size).
2073 pnp_reserve_mem=
2074 [ISAPNP] Exclude memory regions for the
2075 autoconfiguration.
2076 Ranges are in pairs (memory base and size).
2078 ports= [IP_VS_FTP] IPVS ftp helper module
2079 Default is 21.
2080 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2081 may be specified.
2082 Format: <port>,<port>....
2084 print-fatal-signals=
2085 [KNL] debug: print fatal signals
2087 If enabled, warn about various signal handling
2088 related application anomalies: too many signals,
2089 too many POSIX.1 timers, fatal signals causing a
2090 coredump - etc.
2092 If you hit the warning due to signal overflow,
2093 you might want to try "ulimit -i unlimited".
2095 default: off.
2097 printk.time= Show timing data prefixed to each printk message line
2098 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2100 processor.max_cstate= [HW,ACPI]
2101 Limit processor to maximum C-state
2102 max_cstate=9 overrides any DMI blacklist limit.
2104 processor.nocst [HW,ACPI]
2105 Ignore the _CST method to determine C-states,
2106 instead using the legacy FADT method
2108 profile= [KNL] Enable kernel profiling via /proc/profile
2109 Format: [schedule,]<number>
2110 Param: "schedule" - profile schedule points.
2111 Param: <number> - step/bucket size as a power of 2 for
2112 statistical time based profiling.
2113 Param: "sleep" - profile D-state sleeping (millisecs).
2114 Requires CONFIG_SCHEDSTATS
2115 Param: "kvm" - profile VM exits.
2117 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2118 before loading.
2119 See Documentation/blockdev/ramdisk.txt.
2121 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2122 probe for; one of (bare|imps|exps|lifebook|any).
2123 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2124 per second.
2125 psmouse.resetafter= [HW,MOUSE]
2126 Try to reset the device after so many bad packets
2127 (0 = never).
2128 psmouse.resolution=
2129 [HW,MOUSE] Set desired mouse resolution, in dpi.
2130 psmouse.smartscroll=
2131 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2132 0 = disabled, 1 = enabled (default).
2134 pt. [PARIDE]
2135 See Documentation/blockdev/paride.txt.
2137 pty.legacy_count=
2138 [KNL] Number of legacy pty's. Overwrites compiled-in
2139 default number.
2141 quiet [KNL] Disable most log messages
2143 r128= [HW,DRM]
2145 raid= [HW,RAID]
2146 See Documentation/md.txt.
2148 ramdisk_blocksize= [RAM]
2149 See Documentation/blockdev/ramdisk.txt.
2151 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2152 See Documentation/blockdev/ramdisk.txt.
2154 rcupdate.blimit= [KNL,BOOT]
2155 Set maximum number of finished RCU callbacks to process
2156 in one batch.
2158 rcupdate.qhimark= [KNL,BOOT]
2159 Set threshold of queued
2160 RCU callbacks over which batch limiting is disabled.
2162 rcupdate.qlowmark= [KNL,BOOT]
2163 Set threshold of queued RCU callbacks below which
2164 batch limiting is re-enabled.
2166 rdinit= [KNL]
2167 Format: <full_path>
2168 Run specified binary instead of /init from the ramdisk,
2169 used for early userspace startup. See initrd.
2171 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2172 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2173 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2175 relax_domain_level=
2176 [KNL, SMP] Set scheduler's default relax_domain_level.
2177 See Documentation/cgroups/cpusets.txt.
2179 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2181 reservetop= [X86-32]
2182 Format: nn[KMG]
2183 Reserves a hole at the top of the kernel virtual
2184 address space.
2186 reservelow= [X86]
2187 Format: nn[K]
2188 Set the amount of memory to reserve for BIOS at
2189 the bottom of the address space.
2191 reset_devices [KNL] Force drivers to reset the underlying device
2192 during initialization.
2194 resume= [SWSUSP]
2195 Specify the partition device for software suspend
2197 resume_offset= [SWSUSP]
2198 Specify the offset from the beginning of the partition
2199 given by "resume=" at which the swap header is located,
2200 in <PAGE_SIZE> units (needed only for swap files).
2201 See Documentation/power/swsusp-and-swap-files.txt
2203 hibernate= [HIBERNATION]
2204 noresume Don't check if there's a hibernation image
2205 present during boot.
2206 nocompress Don't compress/decompress hibernation images.
2208 retain_initrd [RAM] Keep initrd memory after extraction
2210 rhash_entries= [KNL,NET]
2211 Set number of hash buckets for route cache
2213 riscom8= [HW,SERIAL]
2214 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2216 ro [KNL] Mount root device read-only on boot
2218 root= [KNL] Root filesystem
2220 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2221 mount the root filesystem
2223 rootflags= [KNL] Set root filesystem mount option string
2225 rootfstype= [KNL] Set root filesystem type
2227 rootwait [KNL] Wait (indefinitely) for root device to show up.
2228 Useful for devices that are detected asynchronously
2229 (e.g. USB and MMC devices).
2231 rw [KNL] Mount root device read-write on boot
2233 S [KNL] Run init in single mode
2235 sa1100ir [NET]
2236 See drivers/net/irda/sa1100_ir.c.
2238 sbni= [NET] Granch SBNI12 leased line adapter
2240 sched_debug [KNL] Enables verbose scheduler debug messages.
2242 security= [SECURITY] Choose a security module to enable at boot.
2243 If this boot parameter is not specified, only the first
2244 security module asking for security registration will be
2245 loaded. An invalid security module name will be treated
2246 as if no module has been chosen.
2248 selinux= [SELINUX] Disable or enable SELinux at boot time.
2249 Format: { "0" | "1" }
2250 See security/selinux/Kconfig help text.
2251 0 -- disable.
2252 1 -- enable.
2253 Default value is set via kernel config option.
2254 If enabled at boot time, /selinux/disable can be used
2255 later to disable prior to initial policy load.
2257 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2258 Format: { "0" | "1" }
2259 See security/apparmor/Kconfig help text
2260 0 -- disable.
2261 1 -- enable.
2262 Default value is set via kernel config option.
2264 serialnumber [BUGS=X86-32]
2266 shapers= [NET]
2267 Maximal number of shapers.
2269 show_msr= [x86] show boot-time MSR settings
2270 Format: { <integer> }
2271 Show boot-time (BIOS-initialized) MSR settings.
2272 The parameter means the number of CPUs to show,
2273 for example 1 means boot CPU only.
2275 simeth= [IA-64]
2276 simscsi=
2278 slram= [HW,MTD]
2280 slub_debug[=options[,slabs]] [MM, SLUB]
2281 Enabling slub_debug allows one to determine the
2282 culprit if slab objects become corrupted. Enabling
2283 slub_debug can create guard zones around objects and
2284 may poison objects when not in use. Also tracks the
2285 last alloc / free. For more information see
2286 Documentation/vm/slub.txt.
2288 slub_max_order= [MM, SLUB]
2289 Determines the maximum allowed order for slabs.
2290 A high setting may cause OOMs due to memory
2291 fragmentation. For more information see
2292 Documentation/vm/slub.txt.
2294 slub_min_objects= [MM, SLUB]
2295 The minimum number of objects per slab. SLUB will
2296 increase the slab order up to slub_max_order to
2297 generate a sufficiently large slab able to contain
2298 the number of objects indicated. The higher the number
2299 of objects the smaller the overhead of tracking slabs
2300 and the less frequently locks need to be acquired.
2301 For more information see Documentation/vm/slub.txt.
2303 slub_min_order= [MM, SLUB]
2304 Determines the mininum page order for slabs. Must be
2305 lower than slub_max_order.
2306 For more information see Documentation/vm/slub.txt.
2308 slub_nomerge [MM, SLUB]
2309 Disable merging of slabs with similar size. May be
2310 necessary if there is some reason to distinguish
2311 allocs to different slabs. Debug options disable
2312 merging on their own.
2313 For more information see Documentation/vm/slub.txt.
2315 smart2= [HW]
2316 Format: <io1>[,<io2>[,...,<io8>]]
2318 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2319 attempt to substitute SMP alternatives once at boot.
2321 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2322 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2323 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2324 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2325 smsc-ircc2.ircc_irq= [HW] IRQ line
2326 smsc-ircc2.ircc_dma= [HW] DMA channel
2327 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2328 0: Toshiba Satellite 1800 (GP data pin select)
2329 1: Fast pin select (default)
2330 2: ATC IRMode
2332 softlockup_panic=
2333 [KNL] Should the soft-lockup detector generate panics.
2335 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2336 See Documentation/sonypi.txt
2338 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2339 See Documentation/serial/specialix.txt.
2341 spia_io_base= [HW,MTD]
2342 spia_fio_base=
2343 spia_pedr=
2344 spia_peddr=
2346 stacktrace [FTRACE]
2347 Enabled the stack tracer on boot up.
2349 sti= [PARISC,HW]
2350 Format: <num>
2351 Set the STI (builtin display/keyboard on the HP-PARISC
2352 machines) console (graphic card) which should be used
2353 as the initial boot-console.
2354 See also comment in drivers/video/console/sticore.c.
2356 sti_font= [HW]
2357 See comment in drivers/video/console/sticore.c.
2359 stifb= [HW]
2360 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2362 sunrpc.min_resvport=
2363 sunrpc.max_resvport=
2364 [NFS,SUNRPC]
2365 SunRPC servers often require that client requests
2366 originate from a privileged port (i.e. a port in the
2367 range 0 < portnr < 1024).
2368 An administrator who wishes to reserve some of these
2369 ports for other uses may adjust the range that the
2370 kernel's sunrpc client considers to be privileged
2371 using these two parameters to set the minimum and
2372 maximum port values.
2374 sunrpc.pool_mode=
2375 [NFS]
2376 Control how the NFS server code allocates CPUs to
2377 service thread pools. Depending on how many NICs
2378 you have and where their interrupts are bound, this
2379 option will affect which CPUs will do NFS serving.
2380 Note: this parameter cannot be changed while the
2381 NFS server is running.
2383 auto the server chooses an appropriate mode
2384 automatically using heuristics
2385 global a single global pool contains all CPUs
2386 percpu one pool for each CPU
2387 pernode one pool for each NUMA node (equivalent
2388 to global on non-NUMA machines)
2390 sunrpc.tcp_slot_table_entries=
2391 sunrpc.udp_slot_table_entries=
2392 [NFS,SUNRPC]
2393 Sets the upper limit on the number of simultaneous
2394 RPC calls that can be sent from the client to a
2395 server. Increasing these values may allow you to
2396 improve throughput, but will also increase the
2397 amount of memory reserved for use by the client.
2399 swapaccount[=0|1]
2400 [KNL] Enable accounting of swap in memory resource
2401 controller if no parameter or 1 is given or disable
2402 it if 0 is given (See Documentation/cgroups/memory.txt)
2404 swiotlb= [IA-64] Number of I/O TLB slabs
2406 switches= [HW,M68k]
2408 sysfs.deprecated=0|1 [KNL]
2409 Enable/disable old style sysfs layout for old udev
2410 on older distributions. When this option is enabled
2411 very new udev will not work anymore. When this option
2412 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2413 in older udev will not work anymore.
2414 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2415 the kernel configuration.
2417 sysrq_always_enabled
2418 [KNL]
2419 Ignore sysrq setting - this boot parameter will
2420 neutralize any effect of /proc/sys/kernel/sysrq.
2421 Useful for debugging.
2423 tdfx= [HW,DRM]
2425 test_suspend= [SUSPEND]
2426 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2427 standby suspend) as the system sleep state to briefly
2428 enter during system startup. The system is woken from
2429 this state using a wakeup-capable RTC alarm.
2431 thash_entries= [KNL,NET]
2432 Set number of hash buckets for TCP connection
2434 thermal.act= [HW,ACPI]
2435 -1: disable all active trip points in all thermal zones
2436 <degrees C>: override all lowest active trip points
2438 thermal.crt= [HW,ACPI]
2439 -1: disable all critical trip points in all thermal zones
2440 <degrees C>: override all critical trip points
2442 thermal.nocrt= [HW,ACPI]
2443 Set to disable actions on ACPI thermal zone
2444 critical and hot trip points.
2446 thermal.off= [HW,ACPI]
2447 1: disable ACPI thermal control
2449 thermal.psv= [HW,ACPI]
2450 -1: disable all passive trip points
2451 <degrees C>: override all passive trip points to this
2452 value
2454 thermal.tzp= [HW,ACPI]
2455 Specify global default ACPI thermal zone polling rate
2456 <deci-seconds>: poll all this frequency
2457 0: no polling (default)
2459 threadirqs [KNL]
2460 Force threading of all interrupt handlers except those
2461 marked explicitely IRQF_NO_THREAD.
2463 topology= [S390]
2464 Format: {off | on}
2465 Specify if the kernel should make use of the cpu
2466 topology informations if the hardware supports these.
2467 The scheduler will make use of these informations and
2468 e.g. base its process migration decisions on it.
2469 Default is on.
2471 tp720= [HW,PS2]
2473 tpm_suspend_pcr=[HW,TPM]
2474 Format: integer pcr id
2475 Specify that at suspend time, the tpm driver
2476 should extend the specified pcr with zeros,
2477 as a workaround for some chips which fail to
2478 flush the last written pcr on TPM_SaveState.
2479 This will guarantee that all the other pcrs
2480 are saved.
2482 trace_buf_size=nn[KMG]
2483 [FTRACE] will set tracing buffer size.
2485 trace_event=[event-list]
2486 [FTRACE] Set and start specified trace events in order
2487 to facilitate early boot debugging.
2488 See also Documentation/trace/events.txt
2490 tsc= Disable clocksource stability checks for TSC.
2491 Format: <string>
2492 [x86] reliable: mark tsc clocksource as reliable, this
2493 disables clocksource verification at runtime, as well
2494 as the stability checks done at bootup. Used to enable
2495 high-resolution timer mode on older hardware, and in
2496 virtualized environment.
2497 [x86] noirqtime: Do not use TSC to do irq accounting.
2498 Used to run time disable IRQ_TIME_ACCOUNTING on any
2499 platforms where RDTSC is slow and this accounting
2500 can add overhead.
2502 turbografx.map[2|3]= [HW,JOY]
2503 TurboGraFX parallel port interface
2504 Format:
2505 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2506 See also Documentation/input/joystick-parport.txt
2508 uhash_entries= [KNL,NET]
2509 Set number of hash buckets for UDP/UDP-Lite connections
2511 uhci-hcd.ignore_oc=
2512 [USB] Ignore overcurrent events (default N).
2513 Some badly-designed motherboards generate lots of
2514 bogus events, for ports that aren't wired to
2515 anything. Set this parameter to avoid log spamming.
2516 Note that genuine overcurrent events won't be
2517 reported either.
2519 unknown_nmi_panic
2520 [X86]
2521 Set unknown_nmi_panic=1 early on boot.
2523 usbcore.autosuspend=
2524 [USB] The autosuspend time delay (in seconds) used
2525 for newly-detected USB devices (default 2). This
2526 is the time required before an idle device will be
2527 autosuspended. Devices for which the delay is set
2528 to a negative value won't be autosuspended at all.
2530 usbcore.usbfs_snoop=
2531 [USB] Set to log all usbfs traffic (default 0 = off).
2533 usbcore.blinkenlights=
2534 [USB] Set to cycle leds on hubs (default 0 = off).
2536 usbcore.old_scheme_first=
2537 [USB] Start with the old device initialization
2538 scheme (default 0 = off).
2540 usbcore.use_both_schemes=
2541 [USB] Try the other device initialization scheme
2542 if the first one fails (default 1 = enabled).
2544 usbcore.initial_descriptor_timeout=
2545 [USB] Specifies timeout for the initial 64-byte
2546 USB_REQ_GET_DESCRIPTOR request in milliseconds
2547 (default 5000 = 5.0 seconds).
2549 usbhid.mousepoll=
2550 [USBHID] The interval which mice are to be polled at.
2552 usb-storage.delay_use=
2553 [UMS] The delay in seconds before a new device is
2554 scanned for Logical Units (default 5).
2556 usb-storage.quirks=
2557 [UMS] A list of quirks entries to supplement or
2558 override the built-in unusual_devs list. List
2559 entries are separated by commas. Each entry has
2560 the form VID:PID:Flags where VID and PID are Vendor
2561 and Product ID values (4-digit hex numbers) and
2562 Flags is a set of characters, each corresponding
2563 to a common usb-storage quirk flag as follows:
2564 a = SANE_SENSE (collect more than 18 bytes
2565 of sense data);
2566 b = BAD_SENSE (don't collect more than 18
2567 bytes of sense data);
2568 c = FIX_CAPACITY (decrease the reported
2569 device capacity by one sector);
2570 h = CAPACITY_HEURISTICS (decrease the
2571 reported device capacity by one
2572 sector if the number is odd);
2573 i = IGNORE_DEVICE (don't bind to this
2574 device);
2575 l = NOT_LOCKABLE (don't try to lock and
2576 unlock ejectable media);
2577 m = MAX_SECTORS_64 (don't transfer more
2578 than 64 sectors = 32 KB at a time);
2579 o = CAPACITY_OK (accept the capacity
2580 reported by the device);
2581 r = IGNORE_RESIDUE (the device reports
2582 bogus residue values);
2583 s = SINGLE_LUN (the device has only one
2584 Logical Unit);
2585 w = NO_WP_DETECT (don't test whether the
2586 medium is write-protected).
2587 Example: quirks=0419:aaf5:rl,0421:0433:rc
2589 userpte=
2590 [X86] Flags controlling user PTE allocations.
2592 nohigh = do not allocate PTE pages in
2593 HIGHMEM regardless of setting
2594 of CONFIG_HIGHPTE.
2596 vdso= [X86,SH]
2597 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2598 vdso=1: enable VDSO (default)
2599 vdso=0: disable VDSO mapping
2601 vdso32= [X86]
2602 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2603 vdso32=1: enable 32-bit VDSO (default)
2604 vdso32=0: disable 32-bit VDSO mapping
2606 vector= [IA-64,SMP]
2607 vector=percpu: enable percpu vector domain
2609 video= [FB] Frame buffer configuration
2610 See Documentation/fb/modedb.txt.
2612 vga= [BOOT,X86-32] Select a particular video mode
2613 See Documentation/x86/boot.txt and
2614 Documentation/svga.txt.
2615 Use vga=ask for menu.
2616 This is actually a boot loader parameter; the value is
2617 passed to the kernel using a special protocol.
2619 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2620 size of <nn>. This can be used to increase the
2621 minimum size (128MB on x86). It can also be used to
2622 decrease the size and leave more room for directly
2623 mapped kernel RAM.
2625 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2626 Format: <command>
2628 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2629 Format: <command>
2631 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2632 Format: <command>
2634 vt.cur_default= [VT] Default cursor shape.
2635 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2636 the parameters of the <Esc>[?A;B;Cc escape sequence;
2637 see VGA-softcursor.txt. Default: 2 = underline.
2639 vt.default_blu= [VT]
2640 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2641 Change the default blue palette of the console.
2642 This is a 16-member array composed of values
2643 ranging from 0-255.
2645 vt.default_grn= [VT]
2646 Format: <green0>,<green1>,<green2>,...,<green15>
2647 Change the default green palette of the console.
2648 This is a 16-member array composed of values
2649 ranging from 0-255.
2651 vt.default_red= [VT]
2652 Format: <red0>,<red1>,<red2>,...,<red15>
2653 Change the default red palette of the console.
2654 This is a 16-member array composed of values
2655 ranging from 0-255.
2657 vt.default_utf8=
2658 [VT]
2659 Format=<0|1>
2660 Set system-wide default UTF-8 mode for all tty's.
2661 Default is 1, i.e. UTF-8 mode is enabled for all
2662 newly opened terminals.
2664 vt.global_cursor_default=
2665 [VT]
2666 Format=<-1|0|1>
2667 Set system-wide default for whether a cursor
2668 is shown on new VTs. Default is -1,
2669 i.e. cursors will be created by default unless
2670 overridden by individual drivers. 0 will hide
2671 cursors, 1 will display them.
2673 watchdog timers [HW,WDT] For information on watchdog timers,
2674 see Documentation/watchdog/watchdog-parameters.txt
2675 or other driver-specific files in the
2676 Documentation/watchdog/ directory.
2678 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2679 default x2apic cluster mode on platforms
2680 supporting x2apic.
2682 x86_mrst_timer= [X86-32,APBT]
2683 Choose timer option for x86 Moorestown MID platform.
2684 Two valid options are apbt timer only and lapic timer
2685 plus one apbt timer for broadcast timer.
2686 x86_mrst_timer=apbt_only | lapic_and_apbt
2688 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2689 xd_geo= See header of drivers/block/xd.c.
2691 xen_emul_unplug= [HW,X86,XEN]
2692 Unplug Xen emulated devices
2693 Format: [unplug0,][unplug1]
2694 ide-disks -- unplug primary master IDE devices
2695 aux-ide-disks -- unplug non-primary-master IDE devices
2696 nics -- unplug network devices
2697 all -- unplug all emulated devices (NICs and IDE disks)
2698 unnecessary -- unplugging emulated devices is
2699 unnecessary even if the host did not respond to
2700 the unplug protocol
2701 never -- do not unplug even if version check succeeds
2703 xirc2ps_cs= [NET,PCMCIA]
2704 Format:
2705 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2707 ______________________________________________________________________
2709 TODO:
2711 Add more DRM drivers.