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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 DYNAMIC_DEBUG Build in debug messages and enable them at runtime
48 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
49 EFI EFI Partitioning (GPT) is enabled
50 EIDE EIDE/ATAPI support is enabled.
51 FB The frame buffer device is enabled.
52 GCOV GCOV profiling is enabled.
53 HW Appropriate hardware is enabled.
54 IA-64 IA-64 architecture is enabled.
55 IMA Integrity measurement architecture is enabled.
56 IOSCHED More than one I/O scheduler is enabled.
57 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
58 IPV6 IPv6 support is enabled.
59 ISAPNP ISA PnP code is enabled.
60 ISDN Appropriate ISDN support is enabled.
61 JOY Appropriate joystick support is enabled.
62 KGDB Kernel debugger support is enabled.
63 KVM Kernel Virtual Machine support is enabled.
64 LIBATA Libata driver is enabled
65 LP Printer support is enabled.
66 LOOP Loopback device support is enabled.
67 M68k M68k architecture is enabled.
68 These options have more detailed description inside of
69 Documentation/m68k/kernel-options.txt.
70 MCA MCA bus support is enabled.
71 MDA MDA console support is enabled.
72 MOUSE Appropriate mouse support is enabled.
73 MSI Message Signaled Interrupts (PCI).
74 MTD MTD (Memory Technology Device) support is enabled.
75 NET Appropriate network support is enabled.
76 NUMA NUMA support is enabled.
77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
79 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
81 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
83 PCIE PCI Express support is enabled.
84 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
92 A lot of drivers have their options described inside
93 the Documentation/scsi/ sub-directory.
94 SECURITY Different security models are enabled.
95 SELINUX SELinux support is enabled.
96 APPARMOR AppArmor support is enabled.
97 SERIAL Serial support is enabled.
98 SH SuperH architecture is enabled.
99 SMP The kernel is an SMP kernel.
100 SPARC Sparc architecture is enabled.
101 SWSUSP Software suspend (hibernation) is enabled.
102 SUSPEND System suspend states are enabled.
103 FTRACE Function tracing enabled.
104 TPM TPM drivers are enabled.
105 TS Appropriate touchscreen support is enabled.
106 UMS USB Mass Storage support is enabled.
107 USB USB support is enabled.
108 USBHID USB Human Interface Device support is enabled.
109 V4L Video For Linux support is enabled.
110 VGA The VGA console has been enabled.
111 VT Virtual terminal support is enabled.
112 WDT Watchdog support is enabled.
113 XT IBM PC/XT MFM hard disk support is enabled.
114 X86-32 X86-32, aka i386 architecture is enabled.
115 X86-64 X86-64 architecture is enabled.
116 More X86-64 boot options can be found in
117 Documentation/x86/x86_64/boot-options.txt .
118 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
119 XEN Xen support is enabled
121 In addition, the following text indicates that the option:
123 BUGS= Relates to possible processor bugs on the said processor.
124 KNL Is a kernel start-up parameter.
125 BOOT Is a boot loader parameter.
127 Parameters denoted with BOOT are actually interpreted by the boot
128 loader, and have no meaning to the kernel directly.
129 Do not modify the syntax of boot loader parameters without extreme
130 need or coordination with <Documentation/x86/boot.txt>.
132 There are also arch-specific kernel-parameters not documented here.
133 See for example <Documentation/x86/x86_64/boot-options.txt>.
135 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
136 a trailing = on the name of any parameter states that that parameter will
137 be entered as an environment variable, whereas its absence indicates that
138 it will appear as a kernel argument readable via /proc/cmdline by programs
139 running once the system is up.
141 The number of kernel parameters is not limited, but the length of the
142 complete command line (parameters including spaces etc.) is limited to
143 a fixed number of characters. This limit depends on the architecture
144 and is between 256 and 4096 characters. It is defined in the file
145 ./include/asm/setup.h as COMMAND_LINE_SIZE.
147 Finally, the [KMG] suffix is commonly described after a number of kernel
148 parameter values. These 'K', 'M', and 'G' letters represent the _binary_
149 multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
150 bytes respectively. Such letter suffixes can also be entirely omitted.
153 acpi= [HW,ACPI,X86]
154 Advanced Configuration and Power Interface
155 Format: { force | off | strict | noirq | rsdt }
156 force -- enable ACPI if default was off
157 off -- disable ACPI if default was on
158 noirq -- do not use ACPI for IRQ routing
159 strict -- Be less tolerant of platforms that are not
160 strictly ACPI specification compliant.
161 rsdt -- prefer RSDT over (default) XSDT
162 copy_dsdt -- copy DSDT to memory
164 See also Documentation/power/pm.txt, pci=noacpi
166 acpi_apic_instance= [ACPI, IOAPIC]
167 Format: <int>
168 2: use 2nd APIC table, if available
169 1,0: use 1st APIC table
170 default: 0
172 acpi_backlight= [HW,ACPI]
173 acpi_backlight=vendor
174 acpi_backlight=video
175 If set to vendor, prefer vendor specific driver
176 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
177 of the ACPI video.ko driver.
179 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
180 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
181 Format: <int>
182 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
183 debug output. Bits in debug_layer correspond to a
184 _COMPONENT in an ACPI source file, e.g.,
185 #define _COMPONENT ACPI_PCI_COMPONENT
186 Bits in debug_level correspond to a level in
187 ACPI_DEBUG_PRINT statements, e.g.,
188 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
189 The debug_level mask defaults to "info". See
190 Documentation/acpi/debug.txt for more information about
191 debug layers and levels.
193 Enable processor driver info messages:
194 acpi.debug_layer=0x20000000
195 Enable PCI/PCI interrupt routing info messages:
196 acpi.debug_layer=0x400000
197 Enable AML "Debug" output, i.e., stores to the Debug
198 object while interpreting AML:
199 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
200 Enable all messages related to ACPI hardware:
201 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
203 Some values produce so much output that the system is
204 unusable. The "log_buf_len" parameter may be useful
205 if you need to capture more output.
207 acpi_irq_balance [HW,ACPI]
208 ACPI will balance active IRQs
209 default in APIC mode
211 acpi_irq_nobalance [HW,ACPI]
212 ACPI will not move active IRQs (default)
213 default in PIC mode
215 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
216 Format: <irq>,<irq>...
218 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
219 use by PCI
220 Format: <irq>,<irq>...
222 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
224 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
225 Format: To spoof as Windows 98: ="Microsoft Windows"
227 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
228 acpi_osi="string1" # add string1 -- only one string
229 acpi_osi="!string2" # remove built-in string2
230 acpi_osi= # disable all strings
232 acpi_pm_good [X86]
233 Override the pmtimer bug detection: force the kernel
234 to assume that this machine's pmtimer latches its value
235 and always returns good values.
237 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
238 Format: { level | edge | high | low }
240 acpi_serialize [HW,ACPI] force serialization of AML methods
242 acpi_skip_timer_override [HW,ACPI]
243 Recognize and ignore IRQ0/pin2 Interrupt Override.
244 For broken nForce2 BIOS resulting in XT-PIC timer.
246 acpi_sleep= [HW,ACPI] Sleep options
247 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
248 old_ordering, nonvs, sci_force_enable }
249 See Documentation/power/video.txt for information on
250 s3_bios and s3_mode.
251 s3_beep is for debugging; it makes the PC's speaker beep
252 as soon as the kernel's real-mode entry point is called.
253 s4_nohwsig prevents ACPI hardware signature from being
254 used during resume from hibernation.
255 old_ordering causes the ACPI 1.0 ordering of the _PTS
256 control method, with respect to putting devices into
257 low power states, to be enforced (the ACPI 2.0 ordering
258 of _PTS is used by default).
259 nonvs prevents the kernel from saving/restoring the
260 ACPI NVS memory during suspend/hibernation and resume.
261 sci_force_enable causes the kernel to set SCI_EN directly
262 on resume from S1/S3 (which is against the ACPI spec,
263 but some broken systems don't work without it).
265 acpi_use_timer_override [HW,ACPI]
266 Use timer override. For some broken Nvidia NF5 boards
267 that require a timer override, but don't have HPET
269 acpi_enforce_resources= [ACPI]
270 { strict | lax | no }
271 Check for resource conflicts between native drivers
272 and ACPI OperationRegions (SystemIO and SystemMemory
273 only). IO ports and memory declared in ACPI might be
274 used by the ACPI subsystem in arbitrary AML code and
275 can interfere with legacy drivers.
276 strict (default): access to resources claimed by ACPI
277 is denied; legacy drivers trying to access reserved
278 resources will fail to bind to device using them.
279 lax: access to resources claimed by ACPI is allowed;
280 legacy drivers trying to access reserved resources
281 will bind successfully but a warning message is logged.
282 no: ACPI OperationRegions are not marked as reserved,
283 no further checks are performed.
285 add_efi_memmap [EFI; X86] Include EFI memory map in
286 kernel's map of available physical RAM.
288 agp= [AGP]
289 { off | try_unsupported }
290 off: disable AGP support
291 try_unsupported: try to drive unsupported chipsets
292 (may crash computer or cause data corruption)
294 ALSA [HW,ALSA]
295 See Documentation/sound/alsa/alsa-parameters.txt
297 alignment= [KNL,ARM]
298 Allow the default userspace alignment fault handler
299 behaviour to be specified. Bit 0 enables warnings,
300 bit 1 enables fixups, and bit 2 sends a segfault.
302 amd_iommu= [HW,X86-84]
303 Pass parameters to the AMD IOMMU driver in the system.
304 Possible values are:
305 fullflush - enable flushing of IO/TLB entries when
306 they are unmapped. Otherwise they are
307 flushed before they will be reused, which
308 is a lot of faster
309 off - do not initialize any AMD IOMMU found in
310 the system
312 amijoy.map= [HW,JOY] Amiga joystick support
313 Map of devices attached to JOY0DAT and JOY1DAT
314 Format: <a>,<b>
315 See also Documentation/kernel/input/joystick.txt
317 analog.map= [HW,JOY] Analog joystick and gamepad support
318 Specifies type or capabilities of an analog joystick
319 connected to one of 16 gameports
320 Format: <type1>,<type2>,..<type16>
322 apc= [HW,SPARC]
323 Power management functions (SPARCstation-4/5 + deriv.)
324 Format: noidle
325 Disable APC CPU standby support. SPARCstation-Fox does
326 not play well with APC CPU idle - disable it if you have
327 APC and your system crashes randomly.
329 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
330 Change the output verbosity whilst booting
331 Format: { quiet (default) | verbose | debug }
332 Change the amount of debugging information output
333 when initialising the APIC and IO-APIC components.
335 autoconf= [IPV6]
336 See Documentation/networking/ipv6.txt.
338 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
339 Limit apic dumping. The parameter defines the maximal
340 number of local apics being dumped. Also it is possible
341 to set it to "all" by meaning -- no limit here.
342 Format: { 1 (default) | 2 | ... | all }.
343 The parameter valid if only apic=debug or
344 apic=verbose is specified.
345 Example: apic=debug show_lapic=all
347 apm= [APM] Advanced Power Management
348 See header of arch/x86/kernel/apm_32.c.
350 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
351 Format: <io>,<irq>,<nodeID>
353 ataflop= [HW,M68k]
355 atarimouse= [HW,MOUSE] Atari Mouse
357 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
358 EzKey and similar keyboards
360 atkbd.reset= [HW] Reset keyboard during initialization
362 atkbd.set= [HW] Select keyboard code set
363 Format: <int> (2 = AT (default), 3 = PS/2)
365 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
366 keyboards
368 atkbd.softraw= [HW] Choose between synthetic and real raw mode
369 Format: <bool> (0 = real, 1 = synthetic (default))
371 atkbd.softrepeat= [HW]
372 Use software keyboard repeat
374 autotest [IA64]
376 baycom_epp= [HW,AX25]
377 Format: <io>,<mode>
379 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
380 Format: <io>,<mode>
381 See header of drivers/net/hamradio/baycom_par.c.
383 baycom_ser_fdx= [HW,AX25]
384 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
385 Format: <io>,<irq>,<mode>[,<baud>]
386 See header of drivers/net/hamradio/baycom_ser_fdx.c.
388 baycom_ser_hdx= [HW,AX25]
389 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
390 Format: <io>,<irq>,<mode>
391 See header of drivers/net/hamradio/baycom_ser_hdx.c.
393 boot_delay= Milliseconds to delay each printk during boot.
394 Values larger than 10 seconds (10000) are changed to
395 no delay (0).
396 Format: integer
398 bootmem_debug [KNL] Enable bootmem allocator debug messages.
400 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
401 bttv.radio= Most important insmod options are available as
402 kernel args too.
403 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
404 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
406 bulk_remove=off [PPC] This parameter disables the use of the pSeries
407 firmware feature for flushing multiple hpte entries
408 at a time.
410 c101= [NET] Moxa C101 synchronous serial card
412 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
413 Sometimes CPU hardware bugs make them report the cache
414 size incorrectly. The kernel will attempt work arounds
415 to fix known problems, but for some CPUs it is not
416 possible to determine what the correct size should be.
417 This option provides an override for these situations.
419 capability.disable=
420 [SECURITY] Disable capabilities. This would normally
421 be used only if an alternative security model is to be
422 configured. Potentially dangerous and should only be
423 used if you are entirely sure of the consequences.
425 ccw_timeout_log [S390]
426 See Documentation/s390/CommonIO for details.
428 cgroup_disable= [KNL] Disable a particular controller
429 Format: {name of the controller(s) to disable}
430 {Currently supported controllers - "memory"}
432 checkreqprot [SELINUX] Set initial checkreqprot flag value.
433 Format: { "0" | "1" }
434 See security/selinux/Kconfig help text.
435 0 -- check protection applied by kernel (includes
436 any implied execute protection).
437 1 -- check protection requested by application.
438 Default value is set via a kernel config option.
439 Value can be changed at runtime via
440 /selinux/checkreqprot.
442 cio_ignore= [S390]
443 See Documentation/s390/CommonIO for details.
445 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
446 [Deprecated]
447 Forces specified clocksource (if available) to be used
448 when calculating gettimeofday(). If specified
449 clocksource is not available, it defaults to PIT.
450 Format: { pit | tsc | cyclone | pmtmr }
452 clocksource= Override the default clocksource
453 Format: <string>
454 Override the default clocksource and use the clocksource
455 with the name specified.
456 Some clocksource names to choose from, depending on
457 the platform:
458 [all] jiffies (this is the base, fallback clocksource)
459 [ACPI] acpi_pm
460 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
461 pxa_timer,timer3,32k_counter,timer0_1
462 [AVR32] avr32
463 [X86-32] pit,hpet,tsc;
464 scx200_hrt on Geode; cyclone on IBM x440
465 [MIPS] MIPS
466 [PARISC] cr16
467 [S390] tod
468 [SH] SuperH
469 [SPARC64] tick
470 [X86-64] hpet,tsc
472 clearcpuid=BITNUM [X86]
473 Disable CPUID feature X for the kernel. See
474 arch/x86/include/asm/cpufeature.h for the valid bit
475 numbers. Note the Linux specific bits are not necessarily
476 stable over kernel options, but the vendor specific
477 ones should be.
478 Also note that user programs calling CPUID directly
479 or using the feature without checking anything
480 will still see it. This just prevents it from
481 being used by the kernel or shown in /proc/cpuinfo.
482 Also note the kernel might malfunction if you disable
483 some critical bits.
485 cmo_free_hint= [PPC] Format: { yes | no }
486 Specify whether pages are marked as being inactive
487 when they are freed. This is used in CMO environments
488 to determine OS memory pressure for page stealing by
489 a hypervisor.
490 Default: yes
492 code_bytes [X86] How many bytes of object code to print
493 in an oops report.
494 Range: 0 - 8192
495 Default: 64
497 com20020= [HW,NET] ARCnet - COM20020 chipset
498 Format:
499 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
501 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
502 Format: <io>[,<irq>]
504 com90xx= [HW,NET]
505 ARCnet - COM90xx chipset (memory-mapped buffers)
506 Format: <io>[,<irq>[,<memstart>]]
508 condev= [HW,S390] console device
509 conmode=
511 console= [KNL] Output console device and options.
513 tty<n> Use the virtual console device <n>.
515 ttyS<n>[,options]
516 ttyUSB0[,options]
517 Use the specified serial port. The options are of
518 the form "bbbbpnf", where "bbbb" is the baud rate,
519 "p" is parity ("n", "o", or "e"), "n" is number of
520 bits, and "f" is flow control ("r" for RTS or
521 omit it). Default is "9600n8".
523 See Documentation/serial-console.txt for more
524 information. See
525 Documentation/networking/netconsole.txt for an
526 alternative.
528 uart[8250],io,<addr>[,options]
529 uart[8250],mmio,<addr>[,options]
530 Start an early, polled-mode console on the 8250/16550
531 UART at the specified I/O port or MMIO address,
532 switching to the matching ttyS device later. The
533 options are the same as for ttyS, above.
535 If the device connected to the port is not a TTY but a braille
536 device, prepend "brl," before the device type, for instance
537 console=brl,ttyS0
538 For now, only VisioBraille is supported.
540 consoleblank= [KNL] The console blank (screen saver) timeout in
541 seconds. Defaults to 10*60 = 10mins. A value of 0
542 disables the blank timer.
544 coredump_filter=
545 [KNL] Change the default value for
546 /proc/<pid>/coredump_filter.
547 See also Documentation/filesystems/proc.txt.
549 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
550 Format:
551 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
553 crashkernel=size[KMG][@offset[KMG]]
554 [KNL] Using kexec, Linux can switch to a 'crash kernel'
555 upon panic. This parameter reserves the physical
556 memory region [offset, offset + size] for that kernel
557 image. If '@offset' is omitted, then a suitable offset
558 is selected automatically. Check
559 Documentation/kdump/kdump.txt for further details.
561 crashkernel=range1:size1[,range2:size2,...][@offset]
562 [KNL] Same as above, but depends on the memory
563 in the running system. The syntax of range is
564 start-[end] where start and end are both
565 a memory unit (amount[KMG]). See also
566 Documentation/kdump/kdump.txt for an example.
568 cs89x0_dma= [HW,NET]
569 Format: <dma>
571 cs89x0_media= [HW,NET]
572 Format: { rj45 | aui | bnc }
574 dasd= [HW,NET]
575 See header of drivers/s390/block/dasd_devmap.c.
577 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
578 (one device per port)
579 Format: <port#>,<type>
580 See also Documentation/input/joystick-parport.txt
582 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
583 time. See Documentation/dynamic-debug-howto.txt for
584 details.
586 debug [KNL] Enable kernel debugging (events log level).
588 debug_locks_verbose=
589 [KNL] verbose self-tests
590 Format=<0|1>
591 Print debugging info while doing the locking API
592 self-tests.
593 We default to 0 (no extra messages), setting it to
594 1 will print _a lot_ more information - normally
595 only useful to kernel developers.
597 debug_objects [KNL] Enable object debugging
599 no_debug_objects
600 [KNL] Disable object debugging
602 debugpat [X86] Enable PAT debugging
604 decnet.addr= [HW,NET]
605 Format: <area>[,<node>]
606 See also Documentation/networking/decnet.txt.
608 default_hugepagesz=
609 [same as hugepagesz=] The size of the default
610 HugeTLB page size. This is the size represented by
611 the legacy /proc/ hugepages APIs, used for SHM, and
612 default size when mounting hugetlbfs filesystems.
613 Defaults to the default architecture's huge page size
614 if not specified.
616 dhash_entries= [KNL]
617 Set number of hash buckets for dentry cache.
619 digi= [HW,SERIAL]
620 IO parameters + enable/disable command.
622 digiepca= [HW,SERIAL]
623 See drivers/char/README.epca and
624 Documentation/serial/digiepca.txt.
626 disable= [IPV6]
627 See Documentation/networking/ipv6.txt.
629 disable_ddw [PPC/PSERIES]
630 Disable Dynamic DMA Window support. Use this if
631 to workaround buggy firmware.
633 disable_ipv6= [IPV6]
634 See Documentation/networking/ipv6.txt.
636 disable_mtrr_cleanup [X86]
637 The kernel tries to adjust MTRR layout from continuous
638 to discrete, to make X server driver able to add WB
639 entry later. This parameter disables that.
641 disable_mtrr_trim [X86, Intel and AMD only]
642 By default the kernel will trim any uncacheable
643 memory out of your available memory pool based on
644 MTRR settings. This parameter disables that behavior,
645 possibly causing your machine to run very slowly.
647 disable_timer_pin_1 [X86]
648 Disable PIN 1 of APIC timer
649 Can be useful to work around chipset bugs.
651 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
652 this option disables the debugging code at boot.
654 dma_debug_entries=<number>
655 This option allows to tune the number of preallocated
656 entries for DMA-API debugging code. One entry is
657 required per DMA-API allocation. Use this if the
658 DMA-API debugging code disables itself because the
659 architectural default is too low.
661 dma_debug_driver=<driver_name>
662 With this option the DMA-API debugging driver
663 filter feature can be enabled at boot time. Just
664 pass the driver to filter for as the parameter.
665 The filter can be disabled or changed to another
666 driver later using sysfs.
668 dscc4.setup= [NET]
670 earlycon= [KNL] Output early console device and options.
671 uart[8250],io,<addr>[,options]
672 uart[8250],mmio,<addr>[,options]
673 uart[8250],mmio32,<addr>[,options]
674 Start an early, polled-mode console on the 8250/16550
675 UART at the specified I/O port or MMIO address.
676 MMIO inter-register address stride is either 8bit (mmio)
677 or 32bit (mmio32).
678 The options are the same as for ttyS, above.
680 earlyprintk= [X86,SH,BLACKFIN]
681 earlyprintk=vga
682 earlyprintk=serial[,ttySn[,baudrate]]
683 earlyprintk=ttySn[,baudrate]
684 earlyprintk=dbgp[debugController#]
686 Append ",keep" to not disable it when the real console
687 takes over.
689 Only vga or serial or usb debug port at a time.
691 Currently only ttyS0 and ttyS1 are supported.
693 Interaction with the standard serial driver is not
694 very good.
696 The VGA output is eventually overwritten by the real
697 console.
699 ekgdboc= [X86,KGDB] Allow early kernel console debugging
700 ekgdboc=kbd
702 This is designed to be used in conjunction with
703 the boot argument: earlyprintk=vga
705 edd= [EDD]
706 Format: {"off" | "on" | "skip[mbr]"}
708 eisa_irq_edge= [PARISC,HW]
709 See header of drivers/parisc/eisa.c.
711 elanfreq= [X86-32]
712 See comment before function elanfreq_setup() in
713 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
715 elevator= [IOSCHED]
716 Format: {"cfq" | "deadline" | "noop"}
717 See Documentation/block/as-iosched.txt and
718 Documentation/block/deadline-iosched.txt for details.
720 elfcorehdr= [IA64,PPC,SH,X86]
721 Specifies physical address of start of kernel core
722 image elf header. Generally kexec loader will
723 pass this option to capture kernel.
724 See Documentation/kdump/kdump.txt for details.
726 enable_mtrr_cleanup [X86]
727 The kernel tries to adjust MTRR layout from continuous
728 to discrete, to make X server driver able to add WB
729 entry later. This parameter enables that.
731 enable_timer_pin_1 [X86]
732 Enable PIN 1 of APIC timer
733 Can be useful to work around chipset bugs
734 (in particular on some ATI chipsets).
735 The kernel tries to set a reasonable default.
737 enforcing [SELINUX] Set initial enforcing status.
738 Format: {"0" | "1"}
739 See security/selinux/Kconfig help text.
740 0 -- permissive (log only, no denials).
741 1 -- enforcing (deny and log).
742 Default value is 0.
743 Value can be changed at runtime via /selinux/enforce.
745 erst_disable [ACPI]
746 Disable Error Record Serialization Table (ERST)
747 support.
749 ether= [HW,NET] Ethernet cards parameters
750 This option is obsoleted by the "netdev=" option, which
751 has equivalent usage. See its documentation for details.
753 failslab=
754 fail_page_alloc=
755 fail_make_request=[KNL]
756 General fault injection mechanism.
757 Format: <interval>,<probability>,<space>,<times>
758 See also /Documentation/fault-injection/.
760 floppy= [HW]
761 See Documentation/blockdev/floppy.txt.
763 force_pal_cache_flush
764 [IA-64] Avoid check_sal_cache_flush which may hang on
765 buggy SAL_CACHE_FLUSH implementations. Using this
766 parameter will force ia64_sal_cache_flush to call
767 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
769 ftrace=[tracer]
770 [FTRACE] will set and start the specified tracer
771 as early as possible in order to facilitate early
772 boot debugging.
774 ftrace_dump_on_oops[=orig_cpu]
775 [FTRACE] will dump the trace buffers on oops.
776 If no parameter is passed, ftrace will dump
777 buffers of all CPUs, but if you pass orig_cpu, it will
778 dump only the buffer of the CPU that triggered the
779 oops.
781 ftrace_filter=[function-list]
782 [FTRACE] Limit the functions traced by the function
783 tracer at boot up. function-list is a comma separated
784 list of functions. This list can be changed at run
785 time by the set_ftrace_filter file in the debugfs
786 tracing directory.
788 ftrace_notrace=[function-list]
789 [FTRACE] Do not trace the functions specified in
790 function-list. This list can be changed at run time
791 by the set_ftrace_notrace file in the debugfs
792 tracing directory.
794 ftrace_graph_filter=[function-list]
795 [FTRACE] Limit the top level callers functions traced
796 by the function graph tracer at boot up.
797 function-list is a comma separated list of functions
798 that can be changed at run time by the
799 set_graph_function file in the debugfs tracing directory.
801 gamecon.map[2|3]=
802 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
803 support via parallel port (up to 5 devices per port)
804 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
805 See also Documentation/input/joystick-parport.txt
807 gamma= [HW,DRM]
809 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
810 Format: off | on
811 default: on
813 gcov_persist= [GCOV] When non-zero (default), profiling data for
814 kernel modules is saved and remains accessible via
815 debugfs, even when the module is unloaded/reloaded.
816 When zero, profiling data is discarded and associated
817 debugfs files are removed at module unload time.
819 gpt [EFI] Forces disk with valid GPT signature but
820 invalid Protective MBR to be treated as GPT.
822 hashdist= [KNL,NUMA] Large hashes allocated during boot
823 are distributed across NUMA nodes. Defaults on
824 for 64bit NUMA, off otherwise.
825 Format: 0 | 1 (for off | on)
827 hcl= [IA-64] SGI's Hardware Graph compatibility layer
829 hd= [EIDE] (E)IDE hard drive subsystem geometry
830 Format: <cyl>,<head>,<sect>
832 hest_disable [ACPI]
833 Disable Hardware Error Source Table (HEST) support;
834 corresponding firmware-first mode error processing
835 logic will be disabled.
837 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
838 size of <nn>. This works even on boxes that have no
839 highmem otherwise. This also works to reduce highmem
840 size on bigger boxes.
842 highres= [KNL] Enable/disable high resolution timer mode.
843 Valid parameters: "on", "off"
844 Default: "on"
846 hisax= [HW,ISDN]
847 See Documentation/isdn/README.HiSax.
849 hlt [BUGS=ARM,SH]
851 hpet= [X86-32,HPET] option to control HPET usage
852 Format: { enable (default) | disable | force |
853 verbose }
854 disable: disable HPET and use PIT instead
855 force: allow force enabled of undocumented chips (ICH4,
856 VIA, nVidia)
857 verbose: show contents of HPET registers during setup
859 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
860 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
861 On x86-64 and powerpc, this option can be specified
862 multiple times interleaved with hugepages= to reserve
863 huge pages of different sizes. Valid pages sizes on
864 x86-64 are 2M (when the CPU supports "pse") and 1G
865 (when the CPU supports the "pdpe1gb" cpuinfo flag)
866 Note that 1GB pages can only be allocated at boot time
867 using hugepages= and not freed afterwards.
869 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
870 terminal devices. Valid values: 0..8
871 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
872 If specified, z/VM IUCV HVC accepts connections
873 from listed z/VM user IDs only.
875 keep_bootcon [KNL]
876 Do not unregister boot console at start. This is only
877 useful for debugging when something happens in the window
878 between unregistering the boot console and initializing
879 the real console.
881 i2c_bus= [HW] Override the default board specific I2C bus speed
882 or register an additional I2C bus that is not
883 registered from board initialization code.
884 Format:
885 <bus_id>,<clkrate>
887 i8042.debug [HW] Toggle i8042 debug mode
888 i8042.direct [HW] Put keyboard port into non-translated mode
889 i8042.dumbkbd [HW] Pretend that controller can only read data from
890 keyboard and cannot control its state
891 (Don't attempt to blink the leds)
892 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
893 i8042.nokbd [HW] Don't check/create keyboard port
894 i8042.noloop [HW] Disable the AUX Loopback command while probing
895 for the AUX port
896 i8042.nomux [HW] Don't check presence of an active multiplexing
897 controller
898 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
899 controllers
900 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
901 i8042.reset [HW] Reset the controller during init and cleanup
902 i8042.unlock [HW] Unlock (ignore) the keylock
904 i810= [HW,DRM]
906 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
907 indicates that the driver is running on unsupported
908 hardware.
909 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
910 does not match list of supported models.
911 i8k.power_status
912 [HW] Report power status in /proc/i8k
913 (disabled by default)
914 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
915 capability is set.
917 icn= [HW,ISDN]
918 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
920 ide-core.nodma= [HW] (E)IDE subsystem
921 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
922 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
923 .cdrom .chs .ignore_cable are additional options
924 See Documentation/ide/ide.txt.
926 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
927 Claim all unknown PCI IDE storage controllers.
929 idle= [X86]
930 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
931 Poll forces a polling idle loop that can slightly
932 improve the performance of waking up a idle CPU, but
933 will use a lot of power and make the system run hot.
934 Not recommended.
935 idle=mwait: On systems which support MONITOR/MWAIT but
936 the kernel chose to not use it because it doesn't save
937 as much power as a normal idle loop, use the
938 MONITOR/MWAIT idle loop anyways. Performance should be
939 the same as idle=poll.
940 idle=halt: Halt is forced to be used for CPU idle.
941 In such case C2/C3 won't be used again.
942 idle=nomwait: Disable mwait for CPU C-states
944 ignore_loglevel [KNL]
945 Ignore loglevel setting - this will print /all/
946 kernel messages to the console. Useful for debugging.
948 ihash_entries= [KNL]
949 Set number of hash buckets for inode cache.
951 ima_audit= [IMA]
952 Format: { "0" | "1" }
953 0 -- integrity auditing messages. (Default)
954 1 -- enable informational integrity auditing messages.
956 ima_hash= [IMA]
957 Format: { "sha1" | "md5" }
958 default: "sha1"
960 ima_tcb [IMA]
961 Load a policy which meets the needs of the Trusted
962 Computing Base. This means IMA will measure all
963 programs exec'd, files mmap'd for exec, and all files
964 opened for read by uid=0.
966 init= [KNL]
967 Format: <full_path>
968 Run specified binary instead of /sbin/init as init
969 process.
971 initcall_debug [KNL] Trace initcalls as they are executed. Useful
972 for working out where the kernel is dying during
973 startup.
975 initrd= [BOOT] Specify the location of the initial ramdisk
977 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
978 Format: <irq>
980 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
981 on
982 Enable intel iommu driver.
983 off
984 Disable intel iommu driver.
985 igfx_off [Default Off]
986 By default, gfx is mapped as normal device. If a gfx
987 device has a dedicated DMAR unit, the DMAR unit is
988 bypassed by not enabling DMAR with this option. In
989 this case, gfx device will use physical address for
990 DMA.
991 forcedac [x86_64]
992 With this option iommu will not optimize to look
993 for io virtual address below 32 bit forcing dual
994 address cycle on pci bus for cards supporting greater
995 than 32 bit addressing. The default is to look
996 for translation below 32 bit and if not available
997 then look in the higher range.
998 strict [Default Off]
999 With this option on every unmap_single operation will
1000 result in a hardware IOTLB flush operation as opposed
1001 to batching them for performance.
1002 sp_off [Default Off]
1003 By default, super page will be supported if Intel IOMMU
1004 has the capability. With this option, super page will
1005 not be supported.
1006 intremap= [X86-64, Intel-IOMMU]
1007 Format: { on (default) | off | nosid }
1008 on enable Interrupt Remapping (default)
1009 off disable Interrupt Remapping
1010 nosid disable Source ID checking
1012 inttest= [IA64]
1014 iomem= Disable strict checking of access to MMIO memory
1015 strict regions from userspace.
1016 relaxed
1018 iommu= [x86]
1019 off
1020 force
1021 noforce
1022 biomerge
1023 panic
1024 nopanic
1025 merge
1026 nomerge
1027 forcesac
1028 soft
1029 pt [x86, IA64]
1031 io7= [HW] IO7 for Marvel based alpha systems
1032 See comment before marvel_specify_io7 in
1033 arch/alpha/kernel/core_marvel.c.
1035 io_delay= [X86] I/O delay method
1036 0x80
1037 Standard port 0x80 based delay
1038 0xed
1039 Alternate port 0xed based delay (needed on some systems)
1040 udelay
1041 Simple two microseconds delay
1042 none
1043 No delay
1045 ip= [IP_PNP]
1046 See Documentation/filesystems/nfs/nfsroot.txt.
1048 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1049 See comment before ip2_setup() in
1050 drivers/char/ip2/ip2base.c.
1052 irqfixup [HW]
1053 When an interrupt is not handled search all handlers
1054 for it. Intended to get systems with badly broken
1055 firmware running.
1057 irqpoll [HW]
1058 When an interrupt is not handled search all handlers
1059 for it. Also check all handlers each timer
1060 interrupt. Intended to get systems with badly broken
1061 firmware running.
1063 isapnp= [ISAPNP]
1064 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1066 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1067 Format:
1068 <cpu number>,...,<cpu number>
1069 or
1070 <cpu number>-<cpu number>
1071 (must be a positive range in ascending order)
1072 or a mixture
1073 <cpu number>,...,<cpu number>-<cpu number>
1075 This option can be used to specify one or more CPUs
1076 to isolate from the general SMP balancing and scheduling
1077 algorithms. You can move a process onto or off an
1078 "isolated" CPU via the CPU affinity syscalls or cpuset.
1079 <cpu number> begins at 0 and the maximum value is
1080 "number of CPUs in system - 1".
1082 This option is the preferred way to isolate CPUs. The
1083 alternative -- manually setting the CPU mask of all
1084 tasks in the system -- can cause problems and
1085 suboptimal load balancer performance.
1087 iucv= [HW,NET]
1089 js= [HW,JOY] Analog joystick
1090 See Documentation/input/joystick.txt.
1092 keepinitrd [HW,ARM]
1094 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1095 specifies the amount of memory usable by the kernel
1096 for non-movable allocations. The requested amount is
1097 spread evenly throughout all nodes in the system. The
1098 remaining memory in each node is used for Movable
1099 pages. In the event, a node is too small to have both
1100 kernelcore and Movable pages, kernelcore pages will
1101 take priority and other nodes will have a larger number
1102 of kernelcore pages. The Movable zone is used for the
1103 allocation of pages that may be reclaimed or moved
1104 by the page migration subsystem. This means that
1105 HugeTLB pages may not be allocated from this zone.
1106 Note that allocations like PTEs-from-HighMem still
1107 use the HighMem zone if it exists, and the Normal
1108 zone if it does not.
1110 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1111 Format: <Controller#>[,poll interval]
1112 The controller # is the number of the ehci usb debug
1113 port as it is probed via PCI. The poll interval is
1114 optional and is the number seconds in between
1115 each poll cycle to the debug port in case you need
1116 the functionality for interrupting the kernel with
1117 gdb or control-c on the dbgp connection. When
1118 not using this parameter you use sysrq-g to break into
1119 the kernel debugger.
1121 kgdboc= [KGDB,HW] kgdb over consoles.
1122 Requires a tty driver that supports console polling,
1123 or a supported polling keyboard driver (non-usb).
1124 Serial only format: <serial_device>[,baud]
1125 keyboard only format: kbd
1126 keyboard and serial format: kbd,<serial_device>[,baud]
1127 Optional Kernel mode setting:
1128 kms, kbd format: kms,kbd
1129 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1131 kgdbwait [KGDB] Stop kernel execution and enter the
1132 kernel debugger at the earliest opportunity.
1134 kmac= [MIPS] korina ethernet MAC address.
1135 Configure the RouterBoard 532 series on-chip
1136 Ethernet adapter MAC address.
1138 kmemleak= [KNL] Boot-time kmemleak enable/disable
1139 Valid arguments: on, off
1140 Default: on
1142 kstack=N [X86] Print N words from the kernel stack
1143 in oops dumps.
1145 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1146 Default is 0 (don't ignore, but inject #GP)
1148 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1149 Default is 1 (enabled)
1151 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
1152 KVM MMU at runtime.
1153 Default is 0 (off)
1155 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1156 Default is 1 (enabled)
1158 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1159 for all guests.
1160 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1162 kvm-intel.bypass_guest_pf=
1163 [KVM,Intel] Disables bypassing of guest page faults
1164 on Intel chips. Default is 1 (enabled)
1166 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1167 (virtualized MMU) support on capable Intel chips.
1168 Default is 1 (enabled)
1170 kvm-intel.emulate_invalid_guest_state=
1171 [KVM,Intel] Enable emulation of invalid guest states
1172 Default is 0 (disabled)
1174 kvm-intel.flexpriority=
1175 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1176 Default is 1 (enabled)
1178 kvm-intel.unrestricted_guest=
1179 [KVM,Intel] Disable unrestricted guest feature
1180 (virtualized real and unpaged mode) on capable
1181 Intel chips. Default is 1 (enabled)
1183 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1184 feature (tagged TLBs) on capable Intel chips.
1185 Default is 1 (enabled)
1187 l2cr= [PPC]
1189 l3cr= [PPC]
1191 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1192 disabled it.
1194 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1195 in C2 power state.
1197 libata.dma= [LIBATA] DMA control
1198 libata.dma=0 Disable all PATA and SATA DMA
1199 libata.dma=1 PATA and SATA Disk DMA only
1200 libata.dma=2 ATAPI (CDROM) DMA only
1201 libata.dma=4 Compact Flash DMA only
1202 Combinations also work, so libata.dma=3 enables DMA
1203 for disks and CDROMs, but not CFs.
1205 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1206 libata.ignore_hpa=0 keep BIOS limits (default)
1207 libata.ignore_hpa=1 ignore limits, using full disk
1209 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1210 when set.
1211 Format: <int>
1213 libata.force= [LIBATA] Force configurations. The format is comma
1214 separated list of "[ID:]VAL" where ID is
1215 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1216 matching port, link or device. Basically, it matches
1217 the ATA ID string printed on console by libata. If
1218 the whole ID part is omitted, the last PORT and DEVICE
1219 values are used. If ID hasn't been specified yet, the
1220 configuration applies to all ports, links and devices.
1222 If only DEVICE is omitted, the parameter applies to
1223 the port and all links and devices behind it. DEVICE
1224 number of 0 either selects the first device or the
1225 first fan-out link behind PMP device. It does not
1226 select the host link. DEVICE number of 15 selects the
1227 host link and device attached to it.
1229 The VAL specifies the configuration to force. As long
1230 as there's no ambiguity shortcut notation is allowed.
1231 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1232 The following configurations can be forced.
1234 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1235 Any ID with matching PORT is used.
1237 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1239 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1240 udma[/][16,25,33,44,66,100,133] notation is also
1241 allowed.
1243 * [no]ncq: Turn on or off NCQ.
1245 * nohrst, nosrst, norst: suppress hard, soft
1246 and both resets.
1248 * dump_id: dump IDENTIFY data.
1250 If there are multiple matching configurations changing
1251 the same attribute, the last one is used.
1253 memblock=debug [KNL] Enable memblock debug messages.
1255 load_ramdisk= [RAM] List of ramdisks to load from floppy
1256 See Documentation/blockdev/ramdisk.txt.
1258 lockd.nlm_grace_period=P [NFS] Assign grace period.
1259 Format: <integer>
1261 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1262 Format: <integer>
1264 lockd.nlm_timeout=T [NFS] Assign timeout value.
1265 Format: <integer>
1267 lockd.nlm_udpport=M [NFS] Assign UDP port.
1268 Format: <integer>
1270 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1271 Format: <irq>
1273 loglevel= All Kernel Messages with a loglevel smaller than the
1274 console loglevel will be printed to the console. It can
1275 also be changed with klogd or other programs. The
1276 loglevels are defined as follows:
1278 0 (KERN_EMERG) system is unusable
1279 1 (KERN_ALERT) action must be taken immediately
1280 2 (KERN_CRIT) critical conditions
1281 3 (KERN_ERR) error conditions
1282 4 (KERN_WARNING) warning conditions
1283 5 (KERN_NOTICE) normal but significant condition
1284 6 (KERN_INFO) informational
1285 7 (KERN_DEBUG) debug-level messages
1287 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
1288 in bytes. n must be a power of two. The default
1289 size is set in the kernel config file.
1291 logo.nologo [FB] Disables display of the built-in Linux logo.
1292 This may be used to provide more screen space for
1293 kernel log messages and is useful when debugging
1294 kernel boot problems.
1296 lp=0 [LP] Specify parallel ports to use, e.g,
1297 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1298 lp=reset first parallel port). 'lp=0' disables the
1299 lp=auto printer driver. 'lp=reset' (which can be
1300 specified in addition to the ports) causes
1301 attached printers to be reset. Using
1302 lp=port1,port2,... specifies the parallel ports
1303 to associate lp devices with, starting with
1304 lp0. A port specification may be 'none' to skip
1305 that lp device, or a parport name such as
1306 'parport0'. Specifying 'lp=auto' instead of a
1307 port specification list means that device IDs
1308 from each port should be examined, to see if
1309 an IEEE 1284-compliant printer is attached; if
1310 so, the driver will manage that printer.
1311 See also header of drivers/char/lp.c.
1313 lpj=n [KNL]
1314 Sets loops_per_jiffy to given constant, thus avoiding
1315 time-consuming boot-time autodetection (up to 250 ms per
1316 CPU). 0 enables autodetection (default). To determine
1317 the correct value for your kernel, boot with normal
1318 autodetection and see what value is printed. Note that
1319 on SMP systems the preset will be applied to all CPUs,
1320 which is likely to cause problems if your CPUs need
1321 significantly divergent settings. An incorrect value
1322 will cause delays in the kernel to be wrong, leading to
1323 unpredictable I/O errors and other breakage. Although
1324 unlikely, in the extreme case this might damage your
1325 hardware.
1327 ltpc= [NET]
1328 Format: <io>,<irq>,<dma>
1330 machvec= [IA64] Force the use of a particular machine-vector
1331 (machvec) in a generic kernel.
1332 Example: machvec=hpzx1_swiotlb
1334 machtype= [Loongson] Share the same kernel image file between different
1335 yeeloong laptop.
1336 Example: machtype=lemote-yeeloong-2f-7inch
1338 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1339 than or equal to this physical address is ignored.
1341 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1342 should make use of. maxcpus=n : n >= 0 limits the
1343 kernel to using 'n' processors. n=0 is a special case,
1344 it is equivalent to "nosmp", which also disables
1345 the IO APIC.
1347 max_loop= [LOOP] Maximum number of loopback devices that can
1348 be mounted
1349 Format: <1-256>
1351 mcatest= [IA-64]
1353 mce [X86-32] Machine Check Exception
1355 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1357 md= [HW] RAID subsystems devices and level
1358 See Documentation/md.txt.
1360 mdacon= [MDA]
1361 Format: <first>,<last>
1362 Specifies range of consoles to be captured by the MDA.
1364 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1365 Amount of memory to be used when the kernel is not able
1366 to see the whole system memory or for test.
1367 [X86-32] Use together with memmap= to avoid physical
1368 address space collisions. Without memmap= PCI devices
1369 could be placed at addresses belonging to unused RAM.
1371 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1372 memory.
1374 memchunk=nn[KMG]
1375 [KNL,SH] Allow user to override the default size for
1376 per-device physically contiguous DMA buffers.
1378 memmap=exactmap [KNL,X86] Enable setting of an exact
1379 E820 memory map, as specified by the user.
1380 Such memmap=exactmap lines can be constructed based on
1381 BIOS output or other requirements. See the memmap=nn@ss
1382 option description.
1384 memmap=nn[KMG]@ss[KMG]
1385 [KNL] Force usage of a specific region of memory
1386 Region of memory to be used, from ss to ss+nn.
1388 memmap=nn[KMG]#ss[KMG]
1389 [KNL,ACPI] Mark specific memory as ACPI data.
1390 Region of memory to be used, from ss to ss+nn.
1392 memmap=nn[KMG]$ss[KMG]
1393 [KNL,ACPI] Mark specific memory as reserved.
1394 Region of memory to be used, from ss to ss+nn.
1395 Example: Exclude memory from 0x18690000-0x1869ffff
1396 memmap=64K$0x18690000
1397 or
1398 memmap=0x10000$0x18690000
1400 memory_corruption_check=0/1 [X86]
1401 Some BIOSes seem to corrupt the first 64k of
1402 memory when doing things like suspend/resume.
1403 Setting this option will scan the memory
1404 looking for corruption. Enabling this will
1405 both detect corruption and prevent the kernel
1406 from using the memory being corrupted.
1407 However, its intended as a diagnostic tool; if
1408 repeatable BIOS-originated corruption always
1409 affects the same memory, you can use memmap=
1410 to prevent the kernel from using that memory.
1412 memory_corruption_check_size=size [X86]
1413 By default it checks for corruption in the low
1414 64k, making this memory unavailable for normal
1415 use. Use this parameter to scan for
1416 corruption in more or less memory.
1418 memory_corruption_check_period=seconds [X86]
1419 By default it checks for corruption every 60
1420 seconds. Use this parameter to check at some
1421 other rate. 0 disables periodic checking.
1423 memtest= [KNL,X86] Enable memtest
1424 Format: <integer>
1425 default : 0 <disable>
1426 Specifies the number of memtest passes to be
1427 performed. Each pass selects another test
1428 pattern from a given set of patterns. Memtest
1429 fills the memory with this pattern, validates
1430 memory contents and reserves bad memory
1431 regions that are detected.
1433 meye.*= [HW] Set MotionEye Camera parameters
1434 See Documentation/video4linux/meye.txt.
1436 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1437 Multi-Function General Purpose Timers on AMD Geode
1438 platforms.
1440 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1441 the BIOS has incorrectly applied a workaround. TinyBIOS
1442 version 0.98 is known to be affected, 0.99 fixes the
1443 problem by letting the user disable the workaround.
1445 mga= [HW,DRM]
1447 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1448 physical address is ignored.
1450 mini2440= [ARM,HW,KNL]
1451 Format:[0..2][b][c][t]
1452 Default: "0tb"
1453 MINI2440 configuration specification:
1454 0 - The attached screen is the 3.5" TFT
1455 1 - The attached screen is the 7" TFT
1456 2 - The VGA Shield is attached (1024x768)
1457 Leaving out the screen size parameter will not load
1458 the TFT driver, and the framebuffer will be left
1459 unconfigured.
1460 b - Enable backlight. The TFT backlight pin will be
1461 linked to the kernel VESA blanking code and a GPIO
1462 LED. This parameter is not necessary when using the
1463 VGA shield.
1464 c - Enable the s3c camera interface.
1465 t - Reserved for enabling touchscreen support. The
1466 touchscreen support is not enabled in the mainstream
1467 kernel as of 2.6.30, a preliminary port can be found
1468 in the "bleeding edge" mini2440 support kernel at
1469 http://repo.or.cz/w/linux-2.6/mini2440.git
1471 mminit_loglevel=
1472 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1473 parameter allows control of the logging verbosity for
1474 the additional memory initialisation checks. A value
1475 of 0 disables mminit logging and a level of 4 will
1476 log everything. Information is printed at KERN_DEBUG
1477 so loglevel=8 may also need to be specified.
1479 mousedev.tap_time=
1480 [MOUSE] Maximum time between finger touching and
1481 leaving touchpad surface for touch to be considered
1482 a tap and be reported as a left button click (for
1483 touchpads working in absolute mode only).
1484 Format: <msecs>
1485 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1486 reporting absolute coordinates, such as tablets
1487 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1488 reporting absolute coordinates, such as tablets
1490 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1491 is similar to kernelcore except it specifies the
1492 amount of memory used for migratable allocations.
1493 If both kernelcore and movablecore is specified,
1494 then kernelcore will be at *least* the specified
1495 value but may be more. If movablecore on its own
1496 is specified, the administrator must be careful
1497 that the amount of memory usable for all allocations
1498 is not too small.
1500 MTD_Partition= [MTD]
1501 Format: <name>,<region-number>,<size>,<offset>
1503 MTD_Region= [MTD] Format:
1504 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1506 mtdparts= [MTD]
1507 See drivers/mtd/cmdlinepart.c.
1509 multitce=off [PPC] This parameter disables the use of the pSeries
1510 firmware feature for updating multiple TCE entries
1511 at a time.
1513 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1515 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1517 boundary - index of last SLC block on Flex-OneNAND.
1518 The remaining blocks are configured as MLC blocks.
1519 lock - Configure if Flex-OneNAND boundary should be locked.
1520 Once locked, the boundary cannot be changed.
1521 1 indicates lock status, 0 indicates unlock status.
1523 mtdset= [ARM]
1524 ARM/S3C2412 JIVE boot control
1526 See arch/arm/mach-s3c2412/mach-jive.c
1528 mtouchusb.raw_coordinates=
1529 [HW] Make the MicroTouch USB driver use raw coordinates
1530 ('y', default) or cooked coordinates ('n')
1532 mtrr_chunk_size=nn[KMG] [X86]
1533 used for mtrr cleanup. It is largest continuous chunk
1534 that could hold holes aka. UC entries.
1536 mtrr_gran_size=nn[KMG] [X86]
1537 Used for mtrr cleanup. It is granularity of mtrr block.
1538 Default is 1.
1539 Large value could prevent small alignment from
1540 using up MTRRs.
1542 mtrr_spare_reg_nr=n [X86]
1543 Format: <integer>
1544 Range: 0,7 : spare reg number
1545 Default : 1
1546 Used for mtrr cleanup. It is spare mtrr entries number.
1547 Set to 2 or more if your graphical card needs more.
1549 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1551 netdev= [NET] Network devices parameters
1552 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1553 Note that mem_start is often overloaded to mean
1554 something different and driver-specific.
1555 This usage is only documented in each driver source
1556 file if at all.
1558 nf_conntrack.acct=
1559 [NETFILTER] Enable connection tracking flow accounting
1560 0 to disable accounting
1561 1 to enable accounting
1562 Default value is 0.
1564 nfsaddrs= [NFS] Deprecated. Use ip= instead.
1565 See Documentation/filesystems/nfs/nfsroot.txt.
1567 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1568 See Documentation/filesystems/nfs/nfsroot.txt.
1570 nfsrootdebug [NFS] enable nfsroot debugging messages.
1571 See Documentation/filesystems/nfs/nfsroot.txt.
1573 nfs.callback_tcpport=
1574 [NFS] set the TCP port on which the NFSv4 callback
1575 channel should listen.
1577 nfs.cache_getent=
1578 [NFS] sets the pathname to the program which is used
1579 to update the NFS client cache entries.
1581 nfs.cache_getent_timeout=
1582 [NFS] sets the timeout after which an attempt to
1583 update a cache entry is deemed to have failed.
1585 nfs.idmap_cache_timeout=
1586 [NFS] set the maximum lifetime for idmapper cache
1587 entries.
1589 nfs.enable_ino64=
1590 [NFS] enable 64-bit inode numbers.
1591 If zero, the NFS client will fake up a 32-bit inode
1592 number for the readdir() and stat() syscalls instead
1593 of returning the full 64-bit number.
1594 The default is to return 64-bit inode numbers.
1596 nfs.nfs4_disable_idmapping=
1597 [NFSv4] When set, this option disables the NFSv4
1598 idmapper on the client, but only if the mount
1599 is using the 'sec=sys' security flavour. This may
1600 make migration from legacy NFSv2/v3 systems easier
1601 provided that the server has the appropriate support.
1602 The default is to always enable NFSv4 idmapping.
1604 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1605 when a NMI is triggered.
1606 Format: [state][,regs][,debounce][,die]
1608 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1609 Format: [panic,][nopanic,][num]
1610 Valid num: 0
1611 0 - turn nmi_watchdog off
1612 When panic is specified, panic when an NMI watchdog
1613 timeout occurs (or 'nopanic' to override the opposite
1614 default).
1615 This is useful when you use a panic=... timeout and
1616 need the box quickly up again.
1618 netpoll.carrier_timeout=
1619 [NET] Specifies amount of time (in seconds) that
1620 netpoll should wait for a carrier. By default netpoll
1621 waits 4 seconds.
1623 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1624 emulation library even if a 387 maths coprocessor
1625 is present.
1627 no_console_suspend
1628 [HW] Never suspend the console
1629 Disable suspending of consoles during suspend and
1630 hibernate operations. Once disabled, debugging
1631 messages can reach various consoles while the rest
1632 of the system is being put to sleep (ie, while
1633 debugging driver suspend/resume hooks). This may
1634 not work reliably with all consoles, but is known
1635 to work with serial and VGA consoles.
1637 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1638 caches in the slab allocator. Saves per-node memory,
1639 but will impact performance.
1641 noalign [KNL,ARM]
1643 noapic [SMP,APIC] Tells the kernel to not make use of any
1644 IOAPICs that may be present in the system.
1646 noautogroup Disable scheduler automatic task group creation.
1648 nobats [PPC] Do not use BATs for mapping kernel lowmem
1649 on "Classic" PPC cores.
1651 nocache [ARM]
1653 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1655 nodelayacct [KNL] Disable per-task delay accounting
1657 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1659 nodsp [SH] Disable hardware DSP at boot time.
1661 noefi [X86] Disable EFI runtime services support.
1663 noexec [IA-64]
1665 noexec [X86]
1666 On X86-32 available only on PAE configured kernels.
1667 noexec=on: enable non-executable mappings (default)
1668 noexec=off: disable non-executable mappings
1670 nosmep [X86]
1671 Disable SMEP (Supervisor Mode Execution Protection)
1672 even if it is supported by processor.
1674 noexec32 [X86-64]
1675 This affects only 32-bit executables.
1676 noexec32=on: enable non-executable mappings (default)
1677 read doesn't imply executable mappings
1678 noexec32=off: disable non-executable mappings
1679 read implies executable mappings
1681 nofpu [SH] Disable hardware FPU at boot time.
1683 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1684 register save and restore. The kernel will only save
1685 legacy floating-point registers on task switch.
1687 noxsave [BUGS=X86] Disables x86 extended register state save
1688 and restore using xsave. The kernel will fallback to
1689 enabling legacy floating-point and sse state.
1691 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1692 wfi(ARM) instruction doesn't work correctly and not to
1693 use it. This is also useful when using JTAG debugger.
1695 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1696 instruction doesn't work correctly and not to
1697 use it.
1699 no_file_caps Tells the kernel not to honor file capabilities. The
1700 only way then for a file to be executed with privilege
1701 is to be setuid root or executed by root.
1703 nohalt [IA-64] Tells the kernel not to use the power saving
1704 function PAL_HALT_LIGHT when idle. This increases
1705 power-consumption. On the positive side, it reduces
1706 interrupt wake-up latency, which may improve performance
1707 in certain environments such as networked servers or
1708 real-time systems.
1710 nohz= [KNL] Boottime enable/disable dynamic ticks
1711 Valid arguments: on, off
1712 Default: on
1714 noiotrap [SH] Disables trapped I/O port accesses.
1716 noirqdebug [X86-32] Disables the code which attempts to detect and
1717 disable unhandled interrupt sources.
1719 no_timer_check [X86,APIC] Disables the code which tests for
1720 broken timer IRQ sources.
1722 noisapnp [ISAPNP] Disables ISA PnP code.
1724 noinitrd [RAM] Tells the kernel not to load any configured
1725 initial RAM disk.
1727 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1728 remapping.
1729 [Deprecated - use intremap=off]
1731 nointroute [IA-64]
1733 nojitter [IA64] Disables jitter checking for ITC timers.
1735 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
1737 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
1738 fault handling.
1740 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1742 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1744 noltlbs [PPC] Do not use large page/tlb entries for kernel
1745 lowmem mapping on PPC40x.
1747 nomca [IA-64] Disable machine check abort handling
1749 nomce [X86-32] Machine Check Exception
1751 nomfgpt [X86-32] Disable Multi-Function General Purpose
1752 Timer usage (for AMD Geode machines).
1754 nopat [X86] Disable PAT (page attribute table extension of
1755 pagetables) support.
1757 norandmaps Don't use address space randomization. Equivalent to
1758 echo 0 > /proc/sys/kernel/randomize_va_space
1760 noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1762 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1763 with UP alternatives
1765 noresidual [PPC] Don't use residual data on PReP machines.
1767 noresume [SWSUSP] Disables resume and restores original swap
1768 space.
1770 no-scroll [VGA] Disables scrollback.
1771 This is required for the Braillex ib80-piezo Braille
1772 reader made by F.H. Papenmeier (Germany).
1774 nosbagart [IA-64]
1776 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1778 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1779 and disable the IO APIC. legacy for "maxcpus=0".
1781 nosoftlockup [KNL] Disable the soft-lockup detector.
1783 nosync [HW,M68K] Disables sync negotiation for all devices.
1785 notsc [BUGS=X86-32] Disable Time Stamp Counter
1787 nousb [USB] Disable the USB subsystem
1789 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1791 nowb [ARM]
1793 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1795 nptcg= [IA64] Override max number of concurrent global TLB
1796 purges which is reported from either PAL_VM_SUMMARY or
1797 SAL PALO.
1799 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1800 could support. nr_cpus=n : n >= 1 limits the kernel to
1801 supporting 'n' processors. Later in runtime you can not
1802 use hotplug cpu feature to put more cpu back to online.
1803 just like you compile the kernel NR_CPUS=n
1805 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1807 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1808 one of ['zone', 'node', 'default'] can be specified
1809 This can be set from sysctl after boot.
1810 See Documentation/sysctl/vm.txt for details.
1812 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1813 See Documentation/debugging-via-ohci1394.txt for more
1814 info.
1816 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1817 Rather than timing out after 20 ms if an EC
1818 command is not properly ACKed, override the length
1819 of the timeout. We have interrupts disabled while
1820 waiting for the ACK, so if this is set too high
1821 interrupts *may* be lost!
1823 omap_mux= [OMAP] Override bootloader pin multiplexing.
1824 Format: <mux_mode0.mode_name=value>...
1825 For example, to override I2C bus2:
1826 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1828 oprofile.timer= [HW]
1829 Use timer interrupt instead of performance counters
1831 oprofile.cpu_type= Force an oprofile cpu type
1832 This might be useful if you have an older oprofile
1833 userland or if you want common events.
1834 Format: { arch_perfmon }
1835 arch_perfmon: [X86] Force use of architectural
1836 perfmon on Intel CPUs instead of the
1837 CPU specific event set.
1839 oops=panic Always panic on oopses. Default is to just kill the
1840 process, but there is a small probability of
1841 deadlocking the machine.
1842 This will also cause panics on machine check exceptions.
1843 Useful together with panic=30 to trigger a reboot.
1845 OSS [HW,OSS]
1846 See Documentation/sound/oss/oss-parameters.txt
1848 panic= [KNL] Kernel behaviour on panic: delay <timeout>
1849 seconds before rebooting
1850 Format: <timeout>
1852 parkbd.port= [HW] Parallel port number the keyboard adapter is
1853 connected to, default is 0.
1854 Format: <parport#>
1855 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1856 0 for XT, 1 for AT (default is AT).
1857 Format: <mode>
1859 parport= [HW,PPT] Specify parallel ports. 0 disables.
1860 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1861 Use 'auto' to force the driver to use any
1862 IRQ/DMA settings detected (the default is to
1863 ignore detected IRQ/DMA settings because of
1864 possible conflicts). You can specify the base
1865 address, IRQ, and DMA settings; IRQ and DMA
1866 should be numbers, or 'auto' (for using detected
1867 settings on that particular port), or 'nofifo'
1868 (to avoid using a FIFO even if it is detected).
1869 Parallel ports are assigned in the order they
1870 are specified on the command line, starting
1871 with parport0.
1873 parport_init_mode= [HW,PPT]
1874 Configure VIA parallel port to operate in
1875 a specific mode. This is necessary on Pegasos
1876 computer where firmware has no options for setting
1877 up parallel port mode and sets it to spp.
1878 Currently this function knows 686a and 8231 chips.
1879 Format: [spp|ps2|epp|ecp|ecpepp]
1881 pause_on_oops=
1882 Halt all CPUs after the first oops has been printed for
1883 the specified number of seconds. This is to be used if
1884 your oopses keep scrolling off the screen.
1886 pcbit= [HW,ISDN]
1888 pcd. [PARIDE]
1889 See header of drivers/block/paride/pcd.c.
1890 See also Documentation/blockdev/paride.txt.
1892 pci=option[,option...] [PCI] various PCI subsystem options:
1893 earlydump [X86] dump PCI config space before the kernel
1894 changes anything
1895 off [X86] don't probe for the PCI bus
1896 bios [X86-32] force use of PCI BIOS, don't access
1897 the hardware directly. Use this if your machine
1898 has a non-standard PCI host bridge.
1899 nobios [X86-32] disallow use of PCI BIOS, only direct
1900 hardware access methods are allowed. Use this
1901 if you experience crashes upon bootup and you
1902 suspect they are caused by the BIOS.
1903 conf1 [X86] Force use of PCI Configuration
1904 Mechanism 1.
1905 conf2 [X86] Force use of PCI Configuration
1906 Mechanism 2.
1907 noaer [PCIE] If the PCIEAER kernel config parameter is
1908 enabled, this kernel boot option can be used to
1909 disable the use of PCIE advanced error reporting.
1910 nodomains [PCI] Disable support for multiple PCI
1911 root domains (aka PCI segments, in ACPI-speak).
1912 nommconf [X86] Disable use of MMCONFIG for PCI
1913 Configuration
1914 check_enable_amd_mmconf [X86] check for and enable
1915 properly configured MMIO access to PCI
1916 config space on AMD family 10h CPU
1917 nomsi [MSI] If the PCI_MSI kernel config parameter is
1918 enabled, this kernel boot option can be used to
1919 disable the use of MSI interrupts system-wide.
1920 noioapicquirk [APIC] Disable all boot interrupt quirks.
1921 Safety option to keep boot IRQs enabled. This
1922 should never be necessary.
1923 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1924 primary IO-APIC for bridges that cannot disable
1925 boot IRQs. This fixes a source of spurious IRQs
1926 when the system masks IRQs.
1927 noioapicreroute [APIC] Disable workaround that uses the
1928 boot IRQ equivalent of an IRQ that connects to
1929 a chipset where boot IRQs cannot be disabled.
1930 The opposite of ioapicreroute.
1931 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1932 routing table. These calls are known to be buggy
1933 on several machines and they hang the machine
1934 when used, but on other computers it's the only
1935 way to get the interrupt routing table. Try
1936 this option if the kernel is unable to allocate
1937 IRQs or discover secondary PCI buses on your
1938 motherboard.
1939 rom [X86] Assign address space to expansion ROMs.
1940 Use with caution as certain devices share
1941 address decoders between ROMs and other
1942 resources.
1943 norom [X86] Do not assign address space to
1944 expansion ROMs that do not already have
1945 BIOS assigned address ranges.
1946 nobar [X86] Do not assign address space to the
1947 BARs that weren't assigned by the BIOS.
1948 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1949 assigned automatically to PCI devices. You can
1950 make the kernel exclude IRQs of your ISA cards
1951 this way.
1952 pirqaddr=0xAAAAA [X86] Specify the physical address
1953 of the PIRQ table (normally generated
1954 by the BIOS) if it is outside the
1955 F0000h-100000h range.
1956 lastbus=N [X86] Scan all buses thru bus #N. Can be
1957 useful if the kernel is unable to find your
1958 secondary buses and you want to tell it
1959 explicitly which ones they are.
1960 assign-busses [X86] Always assign all PCI bus
1961 numbers ourselves, overriding
1962 whatever the firmware may have done.
1963 usepirqmask [X86] Honor the possible IRQ mask stored
1964 in the BIOS $PIR table. This is needed on
1965 some systems with broken BIOSes, notably
1966 some HP Pavilion N5400 and Omnibook XE3
1967 notebooks. This will have no effect if ACPI
1968 IRQ routing is enabled.
1969 noacpi [X86] Do not use ACPI for IRQ routing
1970 or for PCI scanning.
1971 use_crs [X86] Use PCI host bridge window information
1972 from ACPI. On BIOSes from 2008 or later, this
1973 is enabled by default. If you need to use this,
1974 please report a bug.
1975 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1976 If you need to use this, please report a bug.
1977 routeirq Do IRQ routing for all PCI devices.
1978 This is normally done in pci_enable_device(),
1979 so this option is a temporary workaround
1980 for broken drivers that don't call it.
1981 skip_isa_align [X86] do not align io start addr, so can
1982 handle more pci cards
1983 firmware [ARM] Do not re-enumerate the bus but instead
1984 just use the configuration from the
1985 bootloader. This is currently used on
1986 IXP2000 systems where the bus has to be
1987 configured a certain way for adjunct CPUs.
1988 noearly [X86] Don't do any early type 1 scanning.
1989 This might help on some broken boards which
1990 machine check when some devices' config space
1991 is read. But various workarounds are disabled
1992 and some IOMMU drivers will not work.
1993 bfsort Sort PCI devices into breadth-first order.
1994 This sorting is done to get a device
1995 order compatible with older (<= 2.4) kernels.
1996 nobfsort Don't sort PCI devices into breadth-first order.
1997 cbiosize=nn[KMG] The fixed amount of bus space which is
1998 reserved for the CardBus bridge's IO window.
1999 The default value is 256 bytes.
2000 cbmemsize=nn[KMG] The fixed amount of bus space which is
2001 reserved for the CardBus bridge's memory
2002 window. The default value is 64 megabytes.
2003 resource_alignment=
2004 Format:
2005 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2006 Specifies alignment and device to reassign
2007 aligned memory resources.
2008 If <order of align> is not specified,
2009 PAGE_SIZE is used as alignment.
2010 PCI-PCI bridge can be specified, if resource
2011 windows need to be expanded.
2012 ecrc= Enable/disable PCIe ECRC (transaction layer
2013 end-to-end CRC checking).
2014 bios: Use BIOS/firmware settings. This is the
2015 the default.
2016 off: Turn ECRC off
2017 on: Turn ECRC on.
2019 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2020 Management.
2021 off Disable ASPM.
2022 force Enable ASPM even on devices that claim not to support it.
2023 WARNING: Forcing ASPM on may cause system lockups.
2025 pcie_ports= [PCIE] PCIe ports handling:
2026 auto Ask the BIOS whether or not to use native PCIe services
2027 associated with PCIe ports (PME, hot-plug, AER). Use
2028 them only if that is allowed by the BIOS.
2029 native Use native PCIe services associated with PCIe ports
2030 unconditionally.
2031 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2032 ports driver.
2034 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2035 nomsi Do not use MSI for native PCIe PME signaling (this makes
2036 all PCIe root ports use INTx for all services).
2038 pcmv= [HW,PCMCIA] BadgePAD 4
2040 pd. [PARIDE]
2041 See Documentation/blockdev/paride.txt.
2043 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2044 boot time.
2045 Format: { 0 | 1 }
2046 See arch/parisc/kernel/pdc_chassis.c
2048 percpu_alloc= Select which percpu first chunk allocator to use.
2049 Currently supported values are "embed" and "page".
2050 Archs may support subset or none of the selections.
2051 See comments in mm/percpu.c for details on each
2052 allocator. This parameter is primarily for debugging
2053 and performance comparison.
2055 pf. [PARIDE]
2056 See Documentation/blockdev/paride.txt.
2058 pg. [PARIDE]
2059 See Documentation/blockdev/paride.txt.
2061 pirq= [SMP,APIC] Manual mp-table setup
2062 See Documentation/x86/i386/IO-APIC.txt.
2064 plip= [PPT,NET] Parallel port network link
2065 Format: { parport<nr> | timid | 0 }
2066 See also Documentation/parport.txt.
2068 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2069 Override pmtimer IOPort with a hex value.
2070 e.g. pmtmr=0x508
2072 pnp.debug [PNP]
2073 Enable PNP debug messages. This depends on the
2074 CONFIG_PNP_DEBUG_MESSAGES option.
2076 pnpacpi= [ACPI]
2077 { off }
2079 pnpbios= [ISAPNP]
2080 { on | off | curr | res | no-curr | no-res }
2082 pnp_reserve_irq=
2083 [ISAPNP] Exclude IRQs for the autoconfiguration
2085 pnp_reserve_dma=
2086 [ISAPNP] Exclude DMAs for the autoconfiguration
2088 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2089 Ranges are in pairs (I/O port base and size).
2091 pnp_reserve_mem=
2092 [ISAPNP] Exclude memory regions for the
2093 autoconfiguration.
2094 Ranges are in pairs (memory base and size).
2096 ports= [IP_VS_FTP] IPVS ftp helper module
2097 Default is 21.
2098 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2099 may be specified.
2100 Format: <port>,<port>....
2102 print-fatal-signals=
2103 [KNL] debug: print fatal signals
2105 If enabled, warn about various signal handling
2106 related application anomalies: too many signals,
2107 too many POSIX.1 timers, fatal signals causing a
2108 coredump - etc.
2110 If you hit the warning due to signal overflow,
2111 you might want to try "ulimit -i unlimited".
2113 default: off.
2115 printk.time= Show timing data prefixed to each printk message line
2116 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2118 processor.max_cstate= [HW,ACPI]
2119 Limit processor to maximum C-state
2120 max_cstate=9 overrides any DMI blacklist limit.
2122 processor.nocst [HW,ACPI]
2123 Ignore the _CST method to determine C-states,
2124 instead using the legacy FADT method
2126 profile= [KNL] Enable kernel profiling via /proc/profile
2127 Format: [schedule,]<number>
2128 Param: "schedule" - profile schedule points.
2129 Param: <number> - step/bucket size as a power of 2 for
2130 statistical time based profiling.
2131 Param: "sleep" - profile D-state sleeping (millisecs).
2132 Requires CONFIG_SCHEDSTATS
2133 Param: "kvm" - profile VM exits.
2135 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2136 before loading.
2137 See Documentation/blockdev/ramdisk.txt.
2139 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2140 probe for; one of (bare|imps|exps|lifebook|any).
2141 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2142 per second.
2143 psmouse.resetafter= [HW,MOUSE]
2144 Try to reset the device after so many bad packets
2145 (0 = never).
2146 psmouse.resolution=
2147 [HW,MOUSE] Set desired mouse resolution, in dpi.
2148 psmouse.smartscroll=
2149 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2150 0 = disabled, 1 = enabled (default).
2152 pt. [PARIDE]
2153 See Documentation/blockdev/paride.txt.
2155 pty.legacy_count=
2156 [KNL] Number of legacy pty's. Overwrites compiled-in
2157 default number.
2159 quiet [KNL] Disable most log messages
2161 r128= [HW,DRM]
2163 raid= [HW,RAID]
2164 See Documentation/md.txt.
2166 ramdisk_blocksize= [RAM]
2167 See Documentation/blockdev/ramdisk.txt.
2169 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2170 See Documentation/blockdev/ramdisk.txt.
2172 rcupdate.blimit= [KNL,BOOT]
2173 Set maximum number of finished RCU callbacks to process
2174 in one batch.
2176 rcupdate.qhimark= [KNL,BOOT]
2177 Set threshold of queued
2178 RCU callbacks over which batch limiting is disabled.
2180 rcupdate.qlowmark= [KNL,BOOT]
2181 Set threshold of queued RCU callbacks below which
2182 batch limiting is re-enabled.
2184 rdinit= [KNL]
2185 Format: <full_path>
2186 Run specified binary instead of /init from the ramdisk,
2187 used for early userspace startup. See initrd.
2189 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2190 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2191 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2193 relax_domain_level=
2194 [KNL, SMP] Set scheduler's default relax_domain_level.
2195 See Documentation/cgroups/cpusets.txt.
2197 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2199 reservetop= [X86-32]
2200 Format: nn[KMG]
2201 Reserves a hole at the top of the kernel virtual
2202 address space.
2204 reservelow= [X86]
2205 Format: nn[K]
2206 Set the amount of memory to reserve for BIOS at
2207 the bottom of the address space.
2209 reset_devices [KNL] Force drivers to reset the underlying device
2210 during initialization.
2212 resume= [SWSUSP]
2213 Specify the partition device for software suspend
2215 resume_offset= [SWSUSP]
2216 Specify the offset from the beginning of the partition
2217 given by "resume=" at which the swap header is located,
2218 in <PAGE_SIZE> units (needed only for swap files).
2219 See Documentation/power/swsusp-and-swap-files.txt
2221 hibernate= [HIBERNATION]
2222 noresume Don't check if there's a hibernation image
2223 present during boot.
2224 nocompress Don't compress/decompress hibernation images.
2226 retain_initrd [RAM] Keep initrd memory after extraction
2228 rhash_entries= [KNL,NET]
2229 Set number of hash buckets for route cache
2231 riscom8= [HW,SERIAL]
2232 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2234 ro [KNL] Mount root device read-only on boot
2236 root= [KNL] Root filesystem
2238 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2239 mount the root filesystem
2241 rootflags= [KNL] Set root filesystem mount option string
2243 rootfstype= [KNL] Set root filesystem type
2245 rootwait [KNL] Wait (indefinitely) for root device to show up.
2246 Useful for devices that are detected asynchronously
2247 (e.g. USB and MMC devices).
2249 rw [KNL] Mount root device read-write on boot
2251 S [KNL] Run init in single mode
2253 sa1100ir [NET]
2254 See drivers/net/irda/sa1100_ir.c.
2256 sbni= [NET] Granch SBNI12 leased line adapter
2258 sched_debug [KNL] Enables verbose scheduler debug messages.
2260 security= [SECURITY] Choose a security module to enable at boot.
2261 If this boot parameter is not specified, only the first
2262 security module asking for security registration will be
2263 loaded. An invalid security module name will be treated
2264 as if no module has been chosen.
2266 selinux= [SELINUX] Disable or enable SELinux at boot time.
2267 Format: { "0" | "1" }
2268 See security/selinux/Kconfig help text.
2269 0 -- disable.
2270 1 -- enable.
2271 Default value is set via kernel config option.
2272 If enabled at boot time, /selinux/disable can be used
2273 later to disable prior to initial policy load.
2275 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2276 Format: { "0" | "1" }
2277 See security/apparmor/Kconfig help text
2278 0 -- disable.
2279 1 -- enable.
2280 Default value is set via kernel config option.
2282 serialnumber [BUGS=X86-32]
2284 shapers= [NET]
2285 Maximal number of shapers.
2287 show_msr= [x86] show boot-time MSR settings
2288 Format: { <integer> }
2289 Show boot-time (BIOS-initialized) MSR settings.
2290 The parameter means the number of CPUs to show,
2291 for example 1 means boot CPU only.
2293 simeth= [IA-64]
2294 simscsi=
2296 slram= [HW,MTD]
2298 slub_debug[=options[,slabs]] [MM, SLUB]
2299 Enabling slub_debug allows one to determine the
2300 culprit if slab objects become corrupted. Enabling
2301 slub_debug can create guard zones around objects and
2302 may poison objects when not in use. Also tracks the
2303 last alloc / free. For more information see
2304 Documentation/vm/slub.txt.
2306 slub_max_order= [MM, SLUB]
2307 Determines the maximum allowed order for slabs.
2308 A high setting may cause OOMs due to memory
2309 fragmentation. For more information see
2310 Documentation/vm/slub.txt.
2312 slub_min_objects= [MM, SLUB]
2313 The minimum number of objects per slab. SLUB will
2314 increase the slab order up to slub_max_order to
2315 generate a sufficiently large slab able to contain
2316 the number of objects indicated. The higher the number
2317 of objects the smaller the overhead of tracking slabs
2318 and the less frequently locks need to be acquired.
2319 For more information see Documentation/vm/slub.txt.
2321 slub_min_order= [MM, SLUB]
2322 Determines the mininum page order for slabs. Must be
2323 lower than slub_max_order.
2324 For more information see Documentation/vm/slub.txt.
2326 slub_nomerge [MM, SLUB]
2327 Disable merging of slabs with similar size. May be
2328 necessary if there is some reason to distinguish
2329 allocs to different slabs. Debug options disable
2330 merging on their own.
2331 For more information see Documentation/vm/slub.txt.
2333 smart2= [HW]
2334 Format: <io1>[,<io2>[,...,<io8>]]
2336 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2337 attempt to substitute SMP alternatives once at boot.
2339 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2340 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2341 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2342 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2343 smsc-ircc2.ircc_irq= [HW] IRQ line
2344 smsc-ircc2.ircc_dma= [HW] DMA channel
2345 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2346 0: Toshiba Satellite 1800 (GP data pin select)
2347 1: Fast pin select (default)
2348 2: ATC IRMode
2350 softlockup_panic=
2351 [KNL] Should the soft-lockup detector generate panics.
2352 Format: <integer>
2354 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2355 See Documentation/sonypi.txt
2357 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2358 See Documentation/serial/specialix.txt.
2360 spia_io_base= [HW,MTD]
2361 spia_fio_base=
2362 spia_pedr=
2363 spia_peddr=
2365 stacktrace [FTRACE]
2366 Enabled the stack tracer on boot up.
2368 sti= [PARISC,HW]
2369 Format: <num>
2370 Set the STI (builtin display/keyboard on the HP-PARISC
2371 machines) console (graphic card) which should be used
2372 as the initial boot-console.
2373 See also comment in drivers/video/console/sticore.c.
2375 sti_font= [HW]
2376 See comment in drivers/video/console/sticore.c.
2378 stifb= [HW]
2379 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2381 sunrpc.min_resvport=
2382 sunrpc.max_resvport=
2383 [NFS,SUNRPC]
2384 SunRPC servers often require that client requests
2385 originate from a privileged port (i.e. a port in the
2386 range 0 < portnr < 1024).
2387 An administrator who wishes to reserve some of these
2388 ports for other uses may adjust the range that the
2389 kernel's sunrpc client considers to be privileged
2390 using these two parameters to set the minimum and
2391 maximum port values.
2393 sunrpc.pool_mode=
2394 [NFS]
2395 Control how the NFS server code allocates CPUs to
2396 service thread pools. Depending on how many NICs
2397 you have and where their interrupts are bound, this
2398 option will affect which CPUs will do NFS serving.
2399 Note: this parameter cannot be changed while the
2400 NFS server is running.
2402 auto the server chooses an appropriate mode
2403 automatically using heuristics
2404 global a single global pool contains all CPUs
2405 percpu one pool for each CPU
2406 pernode one pool for each NUMA node (equivalent
2407 to global on non-NUMA machines)
2409 sunrpc.tcp_slot_table_entries=
2410 sunrpc.udp_slot_table_entries=
2411 [NFS,SUNRPC]
2412 Sets the upper limit on the number of simultaneous
2413 RPC calls that can be sent from the client to a
2414 server. Increasing these values may allow you to
2415 improve throughput, but will also increase the
2416 amount of memory reserved for use by the client.
2418 swapaccount[=0|1]
2419 [KNL] Enable accounting of swap in memory resource
2420 controller if no parameter or 1 is given or disable
2421 it if 0 is given (See Documentation/cgroups/memory.txt)
2423 swiotlb= [IA-64] Number of I/O TLB slabs
2425 switches= [HW,M68k]
2427 sysfs.deprecated=0|1 [KNL]
2428 Enable/disable old style sysfs layout for old udev
2429 on older distributions. When this option is enabled
2430 very new udev will not work anymore. When this option
2431 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2432 in older udev will not work anymore.
2433 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2434 the kernel configuration.
2436 sysrq_always_enabled
2437 [KNL]
2438 Ignore sysrq setting - this boot parameter will
2439 neutralize any effect of /proc/sys/kernel/sysrq.
2440 Useful for debugging.
2442 tdfx= [HW,DRM]
2444 test_suspend= [SUSPEND]
2445 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2446 standby suspend) as the system sleep state to briefly
2447 enter during system startup. The system is woken from
2448 this state using a wakeup-capable RTC alarm.
2450 thash_entries= [KNL,NET]
2451 Set number of hash buckets for TCP connection
2453 thermal.act= [HW,ACPI]
2454 -1: disable all active trip points in all thermal zones
2455 <degrees C>: override all lowest active trip points
2457 thermal.crt= [HW,ACPI]
2458 -1: disable all critical trip points in all thermal zones
2459 <degrees C>: override all critical trip points
2461 thermal.nocrt= [HW,ACPI]
2462 Set to disable actions on ACPI thermal zone
2463 critical and hot trip points.
2465 thermal.off= [HW,ACPI]
2466 1: disable ACPI thermal control
2468 thermal.psv= [HW,ACPI]
2469 -1: disable all passive trip points
2470 <degrees C>: override all passive trip points to this
2471 value
2473 thermal.tzp= [HW,ACPI]
2474 Specify global default ACPI thermal zone polling rate
2475 <deci-seconds>: poll all this frequency
2476 0: no polling (default)
2478 threadirqs [KNL]
2479 Force threading of all interrupt handlers except those
2480 marked explicitely IRQF_NO_THREAD.
2482 topology= [S390]
2483 Format: {off | on}
2484 Specify if the kernel should make use of the cpu
2485 topology information if the hardware supports this.
2486 The scheduler will make use of this information and
2487 e.g. base its process migration decisions on it.
2488 Default is on.
2490 tp720= [HW,PS2]
2492 tpm_suspend_pcr=[HW,TPM]
2493 Format: integer pcr id
2494 Specify that at suspend time, the tpm driver
2495 should extend the specified pcr with zeros,
2496 as a workaround for some chips which fail to
2497 flush the last written pcr on TPM_SaveState.
2498 This will guarantee that all the other pcrs
2499 are saved.
2501 trace_buf_size=nn[KMG]
2502 [FTRACE] will set tracing buffer size.
2504 trace_event=[event-list]
2505 [FTRACE] Set and start specified trace events in order
2506 to facilitate early boot debugging.
2507 See also Documentation/trace/events.txt
2509 tsc= Disable clocksource stability checks for TSC.
2510 Format: <string>
2511 [x86] reliable: mark tsc clocksource as reliable, this
2512 disables clocksource verification at runtime, as well
2513 as the stability checks done at bootup. Used to enable
2514 high-resolution timer mode on older hardware, and in
2515 virtualized environment.
2516 [x86] noirqtime: Do not use TSC to do irq accounting.
2517 Used to run time disable IRQ_TIME_ACCOUNTING on any
2518 platforms where RDTSC is slow and this accounting
2519 can add overhead.
2521 turbografx.map[2|3]= [HW,JOY]
2522 TurboGraFX parallel port interface
2523 Format:
2524 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2525 See also Documentation/input/joystick-parport.txt
2527 uhash_entries= [KNL,NET]
2528 Set number of hash buckets for UDP/UDP-Lite connections
2530 uhci-hcd.ignore_oc=
2531 [USB] Ignore overcurrent events (default N).
2532 Some badly-designed motherboards generate lots of
2533 bogus events, for ports that aren't wired to
2534 anything. Set this parameter to avoid log spamming.
2535 Note that genuine overcurrent events won't be
2536 reported either.
2538 unknown_nmi_panic
2539 [X86] Cause panic on unknown NMI.
2541 usbcore.autosuspend=
2542 [USB] The autosuspend time delay (in seconds) used
2543 for newly-detected USB devices (default 2). This
2544 is the time required before an idle device will be
2545 autosuspended. Devices for which the delay is set
2546 to a negative value won't be autosuspended at all.
2548 usbcore.usbfs_snoop=
2549 [USB] Set to log all usbfs traffic (default 0 = off).
2551 usbcore.blinkenlights=
2552 [USB] Set to cycle leds on hubs (default 0 = off).
2554 usbcore.old_scheme_first=
2555 [USB] Start with the old device initialization
2556 scheme (default 0 = off).
2558 usbcore.use_both_schemes=
2559 [USB] Try the other device initialization scheme
2560 if the first one fails (default 1 = enabled).
2562 usbcore.initial_descriptor_timeout=
2563 [USB] Specifies timeout for the initial 64-byte
2564 USB_REQ_GET_DESCRIPTOR request in milliseconds
2565 (default 5000 = 5.0 seconds).
2567 usbhid.mousepoll=
2568 [USBHID] The interval which mice are to be polled at.
2570 usb-storage.delay_use=
2571 [UMS] The delay in seconds before a new device is
2572 scanned for Logical Units (default 5).
2574 usb-storage.quirks=
2575 [UMS] A list of quirks entries to supplement or
2576 override the built-in unusual_devs list. List
2577 entries are separated by commas. Each entry has
2578 the form VID:PID:Flags where VID and PID are Vendor
2579 and Product ID values (4-digit hex numbers) and
2580 Flags is a set of characters, each corresponding
2581 to a common usb-storage quirk flag as follows:
2582 a = SANE_SENSE (collect more than 18 bytes
2583 of sense data);
2584 b = BAD_SENSE (don't collect more than 18
2585 bytes of sense data);
2586 c = FIX_CAPACITY (decrease the reported
2587 device capacity by one sector);
2588 d = NO_READ_DISC_INFO (don't use
2589 READ_DISC_INFO command);
2590 e = NO_READ_CAPACITY_16 (don't use
2591 READ_CAPACITY_16 command);
2592 h = CAPACITY_HEURISTICS (decrease the
2593 reported device capacity by one
2594 sector if the number is odd);
2595 i = IGNORE_DEVICE (don't bind to this
2596 device);
2597 l = NOT_LOCKABLE (don't try to lock and
2598 unlock ejectable media);
2599 m = MAX_SECTORS_64 (don't transfer more
2600 than 64 sectors = 32 KB at a time);
2601 n = INITIAL_READ10 (force a retry of the
2602 initial READ(10) command);
2603 o = CAPACITY_OK (accept the capacity
2604 reported by the device);
2605 r = IGNORE_RESIDUE (the device reports
2606 bogus residue values);
2607 s = SINGLE_LUN (the device has only one
2608 Logical Unit);
2609 w = NO_WP_DETECT (don't test whether the
2610 medium is write-protected).
2611 Example: quirks=0419:aaf5:rl,0421:0433:rc
2613 userpte=
2614 [X86] Flags controlling user PTE allocations.
2616 nohigh = do not allocate PTE pages in
2617 HIGHMEM regardless of setting
2618 of CONFIG_HIGHPTE.
2620 vdso= [X86,SH]
2621 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2622 vdso=1: enable VDSO (default)
2623 vdso=0: disable VDSO mapping
2625 vdso32= [X86]
2626 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2627 vdso32=1: enable 32-bit VDSO (default)
2628 vdso32=0: disable 32-bit VDSO mapping
2630 vector= [IA-64,SMP]
2631 vector=percpu: enable percpu vector domain
2633 video= [FB] Frame buffer configuration
2634 See Documentation/fb/modedb.txt.
2636 vga= [BOOT,X86-32] Select a particular video mode
2637 See Documentation/x86/boot.txt and
2638 Documentation/svga.txt.
2639 Use vga=ask for menu.
2640 This is actually a boot loader parameter; the value is
2641 passed to the kernel using a special protocol.
2643 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2644 size of <nn>. This can be used to increase the
2645 minimum size (128MB on x86). It can also be used to
2646 decrease the size and leave more room for directly
2647 mapped kernel RAM.
2649 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2650 Format: <command>
2652 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2653 Format: <command>
2655 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2656 Format: <command>
2658 vt.cur_default= [VT] Default cursor shape.
2659 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2660 the parameters of the <Esc>[?A;B;Cc escape sequence;
2661 see VGA-softcursor.txt. Default: 2 = underline.
2663 vt.default_blu= [VT]
2664 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2665 Change the default blue palette of the console.
2666 This is a 16-member array composed of values
2667 ranging from 0-255.
2669 vt.default_grn= [VT]
2670 Format: <green0>,<green1>,<green2>,...,<green15>
2671 Change the default green palette of the console.
2672 This is a 16-member array composed of values
2673 ranging from 0-255.
2675 vt.default_red= [VT]
2676 Format: <red0>,<red1>,<red2>,...,<red15>
2677 Change the default red palette of the console.
2678 This is a 16-member array composed of values
2679 ranging from 0-255.
2681 vt.default_utf8=
2682 [VT]
2683 Format=<0|1>
2684 Set system-wide default UTF-8 mode for all tty's.
2685 Default is 1, i.e. UTF-8 mode is enabled for all
2686 newly opened terminals.
2688 vt.global_cursor_default=
2689 [VT]
2690 Format=<-1|0|1>
2691 Set system-wide default for whether a cursor
2692 is shown on new VTs. Default is -1,
2693 i.e. cursors will be created by default unless
2694 overridden by individual drivers. 0 will hide
2695 cursors, 1 will display them.
2697 watchdog timers [HW,WDT] For information on watchdog timers,
2698 see Documentation/watchdog/watchdog-parameters.txt
2699 or other driver-specific files in the
2700 Documentation/watchdog/ directory.
2702 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2703 default x2apic cluster mode on platforms
2704 supporting x2apic.
2706 x86_mrst_timer= [X86-32,APBT]
2707 Choose timer option for x86 Moorestown MID platform.
2708 Two valid options are apbt timer only and lapic timer
2709 plus one apbt timer for broadcast timer.
2710 x86_mrst_timer=apbt_only | lapic_and_apbt
2712 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2713 xd_geo= See header of drivers/block/xd.c.
2715 xen_emul_unplug= [HW,X86,XEN]
2716 Unplug Xen emulated devices
2717 Format: [unplug0,][unplug1]
2718 ide-disks -- unplug primary master IDE devices
2719 aux-ide-disks -- unplug non-primary-master IDE devices
2720 nics -- unplug network devices
2721 all -- unplug all emulated devices (NICs and IDE disks)
2722 unnecessary -- unplugging emulated devices is
2723 unnecessary even if the host did not respond to
2724 the unplug protocol
2725 never -- do not unplug even if version check succeeds
2727 xirc2ps_cs= [NET,PCMCIA]
2728 Format:
2729 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2731 ______________________________________________________________________
2733 TODO:
2735 Add more DRM drivers.