[tomato.git] / release / src-rt-6.x.4708 / linux / linux-2.6.36 / Documentation / kernel-parameters.txt
| blob | 48128ed0800632324b77b6e2fa853d1501b31830 |
1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 GCOV GCOV profiling is enabled.
52 HW Appropriate hardware is enabled.
53 IA-64 IA-64 architecture is enabled.
54 IMA Integrity measurement architecture is enabled.
55 IOSCHED More than one I/O scheduler is enabled.
56 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
57 IPV6 IPv6 support is enabled.
58 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
61 KGDB Kernel debugger support is enabled.
62 KVM Kernel Virtual Machine support is enabled.
63 LIBATA Libata driver is enabled
64 LP Printer support is enabled.
65 LOOP Loopback device support is enabled.
66 M68k M68k architecture is enabled.
67 These options have more detailed description inside of
68 Documentation/m68k/kernel-options.txt.
69 MCA MCA bus support is enabled.
70 MDA MDA console support is enabled.
71 MOUSE Appropriate mouse support is enabled.
72 MSI Message Signaled Interrupts (PCI).
73 MTD MTD (Memory Technology Device) support is enabled.
74 NET Appropriate network support is enabled.
75 NUMA NUMA support is enabled.
76 NFS Appropriate NFS support is enabled.
77 OSS OSS sound support is enabled.
78 PV_OPS A paravirtualized kernel is enabled.
79 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
80 PARISC The PA-RISC architecture is enabled.
81 PCI PCI bus support is enabled.
82 PCIE PCI Express support is enabled.
83 PCMCIA The PCMCIA subsystem is enabled.
84 PNP Plug & Play support is enabled.
85 PPC PowerPC architecture is enabled.
86 PPT Parallel port support is enabled.
87 PS2 Appropriate PS/2 support is enabled.
88 RAM RAM disk support is enabled.
89 S390 S390 architecture is enabled.
90 SCSI Appropriate SCSI support is enabled.
91 A lot of drivers have their options described inside
92 the Documentation/scsi/ sub-directory.
93 SECURITY Different security models are enabled.
94 SELINUX SELinux support is enabled.
95 APPARMOR AppArmor support is enabled.
96 SERIAL Serial support is enabled.
97 SH SuperH architecture is enabled.
98 SMP The kernel is an SMP kernel.
99 SPARC Sparc architecture is enabled.
100 SWSUSP Software suspend (hibernation) is enabled.
101 SUSPEND System suspend states are enabled.
102 FTRACE Function tracing enabled.
103 TPM TPM drivers are enabled.
104 TS Appropriate touchscreen support is enabled.
105 UMS USB Mass Storage support is enabled.
106 USB USB support is enabled.
107 USBHID USB Human Interface Device support is enabled.
108 V4L Video For Linux support is enabled.
109 VGA The VGA console has been enabled.
110 VT Virtual terminal support is enabled.
111 WDT Watchdog support is enabled.
112 XT IBM PC/XT MFM hard disk support is enabled.
113 X86-32 X86-32, aka i386 architecture is enabled.
114 X86-64 X86-64 architecture is enabled.
115 More X86-64 boot options can be found in
116 Documentation/x86/x86_64/boot-options.txt .
117 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
118 XEN Xen support is enabled
120 In addition, the following text indicates that the option:
122 BUGS= Relates to possible processor bugs on the said processor.
123 KNL Is a kernel start-up parameter.
124 BOOT Is a boot loader parameter.
126 Parameters denoted with BOOT are actually interpreted by the boot
127 loader, and have no meaning to the kernel directly.
128 Do not modify the syntax of boot loader parameters without extreme
129 need or coordination with <Documentation/x86/boot.txt>.
131 There are also arch-specific kernel-parameters not documented here.
132 See for example <Documentation/x86/x86_64/boot-options.txt>.
134 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
135 a trailing = on the name of any parameter states that that parameter will
136 be entered as an environment variable, whereas its absence indicates that
137 it will appear as a kernel argument readable via /proc/cmdline by programs
138 running once the system is up.
140 The number of kernel parameters is not limited, but the length of the
141 complete command line (parameters including spaces etc.) is limited to
142 a fixed number of characters. This limit depends on the architecture
143 and is between 256 and 4096 characters. It is defined in the file
144 ./include/asm/setup.h as COMMAND_LINE_SIZE.
147 acpi= [HW,ACPI,X86]
148 Advanced Configuration and Power Interface
149 Format: { force | off | strict | noirq | rsdt }
150 force -- enable ACPI if default was off
151 off -- disable ACPI if default was on
152 noirq -- do not use ACPI for IRQ routing
153 strict -- Be less tolerant of platforms that are not
154 strictly ACPI specification compliant.
155 rsdt -- prefer RSDT over (default) XSDT
156 copy_dsdt -- copy DSDT to memory
158 See also Documentation/power/pm.txt, pci=noacpi
160 acpi_apic_instance= [ACPI, IOAPIC]
161 Format: <int>
162 2: use 2nd APIC table, if available
163 1,0: use 1st APIC table
164 default: 0
166 acpi_backlight= [HW,ACPI]
167 acpi_backlight=vendor
168 acpi_backlight=video
169 If set to vendor, prefer vendor specific driver
170 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
171 of the ACPI video.ko driver.
173 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
174 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
175 Format: <int>
176 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
177 debug output. Bits in debug_layer correspond to a
178 _COMPONENT in an ACPI source file, e.g.,
179 #define _COMPONENT ACPI_PCI_COMPONENT
180 Bits in debug_level correspond to a level in
181 ACPI_DEBUG_PRINT statements, e.g.,
182 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
183 The debug_level mask defaults to "info". See
184 Documentation/acpi/debug.txt for more information about
185 debug layers and levels.
187 Enable processor driver info messages:
188 acpi.debug_layer=0x20000000
189 Enable PCI/PCI interrupt routing info messages:
190 acpi.debug_layer=0x400000
191 Enable AML "Debug" output, i.e., stores to the Debug
192 object while interpreting AML:
193 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
194 Enable all messages related to ACPI hardware:
195 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
197 Some values produce so much output that the system is
198 unusable. The "log_buf_len" parameter may be useful
199 if you need to capture more output.
201 acpi_display_output= [HW,ACPI]
202 acpi_display_output=vendor
203 acpi_display_output=video
204 See above.
206 acpi_irq_balance [HW,ACPI]
207 ACPI will balance active IRQs
208 default in APIC mode
210 acpi_irq_nobalance [HW,ACPI]
211 ACPI will not move active IRQs (default)
212 default in PIC mode
214 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
215 Format: <irq>,<irq>...
217 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
218 use by PCI
219 Format: <irq>,<irq>...
221 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
223 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
224 Format: To spoof as Windows 98: ="Microsoft Windows"
226 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
227 acpi_osi="string1" # add string1 -- only one string
228 acpi_osi="!string2" # remove built-in string2
229 acpi_osi= # disable all strings
231 acpi_pm_good [X86]
232 Override the pmtimer bug detection: force the kernel
233 to assume that this machine's pmtimer latches its value
234 and always returns good values.
236 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
237 Format: { level | edge | high | low }
239 acpi_serialize [HW,ACPI] force serialization of AML methods
241 acpi_skip_timer_override [HW,ACPI]
242 Recognize and ignore IRQ0/pin2 Interrupt Override.
243 For broken nForce2 BIOS resulting in XT-PIC timer.
245 acpi_sleep= [HW,ACPI] Sleep options
246 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
247 old_ordering, s4_nonvs, sci_force_enable }
248 See Documentation/power/video.txt for information on
249 s3_bios and s3_mode.
250 s3_beep is for debugging; it makes the PC's speaker beep
251 as soon as the kernel's real-mode entry point is called.
252 s4_nohwsig prevents ACPI hardware signature from being
253 used during resume from hibernation.
254 old_ordering causes the ACPI 1.0 ordering of the _PTS
255 control method, with respect to putting devices into
256 low power states, to be enforced (the ACPI 2.0 ordering
257 of _PTS is used by default).
258 nonvs prevents the kernel from saving/restoring the
259 ACPI NVS memory during suspend/hibernation and resume.
260 sci_force_enable causes the kernel to set SCI_EN directly
261 on resume from S1/S3 (which is against the ACPI spec,
262 but some broken systems don't work without it).
264 acpi_use_timer_override [HW,ACPI]
265 Use timer override. For some broken Nvidia NF5 boards
266 that require a timer override, but don't have HPET
268 acpi_enforce_resources= [ACPI]
269 { strict | lax | no }
270 Check for resource conflicts between native drivers
271 and ACPI OperationRegions (SystemIO and SystemMemory
272 only). IO ports and memory declared in ACPI might be
273 used by the ACPI subsystem in arbitrary AML code and
274 can interfere with legacy drivers.
275 strict (default): access to resources claimed by ACPI
276 is denied; legacy drivers trying to access reserved
277 resources will fail to bind to device using them.
278 lax: access to resources claimed by ACPI is allowed;
279 legacy drivers trying to access reserved resources
280 will bind successfully but a warning message is logged.
281 no: ACPI OperationRegions are not marked as reserved,
282 no further checks are performed.
284 add_efi_memmap [EFI; X86] Include EFI memory map in
285 kernel's map of available physical RAM.
287 agp= [AGP]
288 { off | try_unsupported }
289 off: disable AGP support
290 try_unsupported: try to drive unsupported chipsets
291 (may crash computer or cause data corruption)
293 ALSA [HW,ALSA]
294 See Documentation/sound/alsa/alsa-parameters.txt
296 alignment= [KNL,ARM]
297 Allow the default userspace alignment fault handler
298 behaviour to be specified. Bit 0 enables warnings,
299 bit 1 enables fixups, and bit 2 sends a segfault.
301 amd_iommu= [HW,X86-84]
302 Pass parameters to the AMD IOMMU driver in the system.
303 Possible values are:
304 fullflush - enable flushing of IO/TLB entries when
305 they are unmapped. Otherwise they are
306 flushed before they will be reused, which
307 is a lot of faster
308 off - do not initialize any AMD IOMMU found in
309 the system
311 amijoy.map= [HW,JOY] Amiga joystick support
312 Map of devices attached to JOY0DAT and JOY1DAT
313 Format: <a>,<b>
314 See also Documentation/kernel/input/joystick.txt
316 analog.map= [HW,JOY] Analog joystick and gamepad support
317 Specifies type or capabilities of an analog joystick
318 connected to one of 16 gameports
319 Format: <type1>,<type2>,..<type16>
321 apc= [HW,SPARC]
322 Power management functions (SPARCstation-4/5 + deriv.)
323 Format: noidle
324 Disable APC CPU standby support. SPARCstation-Fox does
325 not play well with APC CPU idle - disable it if you have
326 APC and your system crashes randomly.
328 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
329 Change the output verbosity whilst booting
330 Format: { quiet (default) | verbose | debug }
331 Change the amount of debugging information output
332 when initialising the APIC and IO-APIC components.
334 autoconf= [IPV6]
335 See Documentation/networking/ipv6.txt.
337 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
338 Limit apic dumping. The parameter defines the maximal
339 number of local apics being dumped. Also it is possible
340 to set it to "all" by meaning -- no limit here.
341 Format: { 1 (default) | 2 | ... | all }.
342 The parameter valid if only apic=debug or
343 apic=verbose is specified.
344 Example: apic=debug show_lapic=all
346 apm= [APM] Advanced Power Management
347 See header of arch/x86/kernel/apm_32.c.
349 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
350 Format: <io>,<irq>,<nodeID>
352 ataflop= [HW,M68k]
354 atarimouse= [HW,MOUSE] Atari Mouse
356 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
357 EzKey and similar keyboards
359 atkbd.reset= [HW] Reset keyboard during initialization
361 atkbd.set= [HW] Select keyboard code set
362 Format: <int> (2 = AT (default), 3 = PS/2)
364 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
365 keyboards
367 atkbd.softraw= [HW] Choose between synthetic and real raw mode
368 Format: <bool> (0 = real, 1 = synthetic (default))
370 atkbd.softrepeat= [HW]
371 Use software keyboard repeat
373 autotest [IA64]
375 baycom_epp= [HW,AX25]
376 Format: <io>,<mode>
378 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
379 Format: <io>,<mode>
380 See header of drivers/net/hamradio/baycom_par.c.
382 baycom_ser_fdx= [HW,AX25]
383 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
384 Format: <io>,<irq>,<mode>[,<baud>]
385 See header of drivers/net/hamradio/baycom_ser_fdx.c.
387 baycom_ser_hdx= [HW,AX25]
388 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
389 Format: <io>,<irq>,<mode>
390 See header of drivers/net/hamradio/baycom_ser_hdx.c.
392 boot_delay= Milliseconds to delay each printk during boot.
393 Values larger than 10 seconds (10000) are changed to
394 no delay (0).
395 Format: integer
397 bootmem_debug [KNL] Enable bootmem allocator debug messages.
399 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
400 bttv.radio= Most important insmod options are available as
401 kernel args too.
402 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
403 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
405 c101= [NET] Moxa C101 synchronous serial card
407 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
408 Sometimes CPU hardware bugs make them report the cache
409 size incorrectly. The kernel will attempt work arounds
410 to fix known problems, but for some CPUs it is not
411 possible to determine what the correct size should be.
412 This option provides an override for these situations.
414 capability.disable=
415 [SECURITY] Disable capabilities. This would normally
416 be used only if an alternative security model is to be
417 configured. Potentially dangerous and should only be
418 used if you are entirely sure of the consequences.
420 ccw_timeout_log [S390]
421 See Documentation/s390/CommonIO for details.
423 cgroup_disable= [KNL] Disable a particular controller
424 Format: {name of the controller(s) to disable}
425 {Currently supported controllers - "memory"}
427 checkreqprot [SELINUX] Set initial checkreqprot flag value.
428 Format: { "0" | "1" }
429 See security/selinux/Kconfig help text.
430 0 -- check protection applied by kernel (includes
431 any implied execute protection).
432 1 -- check protection requested by application.
433 Default value is set via a kernel config option.
434 Value can be changed at runtime via
435 /selinux/checkreqprot.
437 cio_ignore= [S390]
438 See Documentation/s390/CommonIO for details.
440 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
441 [Deprecated]
442 Forces specified clocksource (if available) to be used
443 when calculating gettimeofday(). If specified
444 clocksource is not available, it defaults to PIT.
445 Format: { pit | tsc | cyclone | pmtmr }
447 clocksource= Override the default clocksource
448 Format: <string>
449 Override the default clocksource and use the clocksource
450 with the name specified.
451 Some clocksource names to choose from, depending on
452 the platform:
453 [all] jiffies (this is the base, fallback clocksource)
454 [ACPI] acpi_pm
455 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
456 pxa_timer,timer3,32k_counter,timer0_1
457 [AVR32] avr32
458 [X86-32] pit,hpet,tsc,vmi-timer;
459 scx200_hrt on Geode; cyclone on IBM x440
460 [MIPS] MIPS
461 [PARISC] cr16
462 [S390] tod
463 [SH] SuperH
464 [SPARC64] tick
465 [X86-64] hpet,tsc
467 clearcpuid=BITNUM [X86]
468 Disable CPUID feature X for the kernel. See
469 arch/x86/include/asm/cpufeature.h for the valid bit
470 numbers. Note the Linux specific bits are not necessarily
471 stable over kernel options, but the vendor specific
472 ones should be.
473 Also note that user programs calling CPUID directly
474 or using the feature without checking anything
475 will still see it. This just prevents it from
476 being used by the kernel or shown in /proc/cpuinfo.
477 Also note the kernel might malfunction if you disable
478 some critical bits.
480 cmo_free_hint= [PPC] Format: { yes | no }
481 Specify whether pages are marked as being inactive
482 when they are freed. This is used in CMO environments
483 to determine OS memory pressure for page stealing by
484 a hypervisor.
485 Default: yes
487 code_bytes [X86] How many bytes of object code to print
488 in an oops report.
489 Range: 0 - 8192
490 Default: 64
492 com20020= [HW,NET] ARCnet - COM20020 chipset
493 Format:
494 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
496 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
497 Format: <io>[,<irq>]
499 com90xx= [HW,NET]
500 ARCnet - COM90xx chipset (memory-mapped buffers)
501 Format: <io>[,<irq>[,<memstart>]]
503 condev= [HW,S390] console device
504 conmode=
506 console= [KNL] Output console device and options.
508 tty<n> Use the virtual console device <n>.
510 ttyS<n>[,options]
511 ttyUSB0[,options]
512 Use the specified serial port. The options are of
513 the form "bbbbpnf", where "bbbb" is the baud rate,
514 "p" is parity ("n", "o", or "e"), "n" is number of
515 bits, and "f" is flow control ("r" for RTS or
516 omit it). Default is "9600n8".
518 See Documentation/serial-console.txt for more
519 information. See
520 Documentation/networking/netconsole.txt for an
521 alternative.
523 uart[8250],io,<addr>[,options]
524 uart[8250],mmio,<addr>[,options]
525 Start an early, polled-mode console on the 8250/16550
526 UART at the specified I/O port or MMIO address,
527 switching to the matching ttyS device later. The
528 options are the same as for ttyS, above.
530 If the device connected to the port is not a TTY but a braille
531 device, prepend "brl," before the device type, for instance
532 console=brl,ttyS0
533 For now, only VisioBraille is supported.
535 consoleblank= [KNL] The console blank (screen saver) timeout in
536 seconds. Defaults to 10*60 = 10mins. A value of 0
537 disables the blank timer.
539 coredump_filter=
540 [KNL] Change the default value for
541 /proc/<pid>/coredump_filter.
542 See also Documentation/filesystems/proc.txt.
544 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
545 Format:
546 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
548 crashkernel=nn[KMG]@ss[KMG]
549 [KNL] Reserve a chunk of physical memory to
550 hold a kernel to switch to with kexec on panic.
552 crashkernel=range1:size1[,range2:size2,...][@offset]
553 [KNL] Same as above, but depends on the memory
554 in the running system. The syntax of range is
555 start-[end] where start and end are both
556 a memory unit (amount[KMG]). See also
557 Documentation/kdump/kdump.txt for a example.
559 cs89x0_dma= [HW,NET]
560 Format: <dma>
562 cs89x0_media= [HW,NET]
563 Format: { rj45 | aui | bnc }
565 dasd= [HW,NET]
566 See header of drivers/s390/block/dasd_devmap.c.
568 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
569 (one device per port)
570 Format: <port#>,<type>
571 See also Documentation/input/joystick-parport.txt
573 debug [KNL] Enable kernel debugging (events log level).
575 debug_locks_verbose=
576 [KNL] verbose self-tests
577 Format=<0|1>
578 Print debugging info while doing the locking API
579 self-tests.
580 We default to 0 (no extra messages), setting it to
581 1 will print _a lot_ more information - normally
582 only useful to kernel developers.
584 debug_objects [KNL] Enable object debugging
586 no_debug_objects
587 [KNL] Disable object debugging
589 debugpat [X86] Enable PAT debugging
591 decnet.addr= [HW,NET]
592 Format: <area>[,<node>]
593 See also Documentation/networking/decnet.txt.
595 default_hugepagesz=
596 [same as hugepagesz=] The size of the default
597 HugeTLB page size. This is the size represented by
598 the legacy /proc/ hugepages APIs, used for SHM, and
599 default size when mounting hugetlbfs filesystems.
600 Defaults to the default architecture's huge page size
601 if not specified.
603 dhash_entries= [KNL]
604 Set number of hash buckets for dentry cache.
606 digi= [HW,SERIAL]
607 IO parameters + enable/disable command.
609 digiepca= [HW,SERIAL]
610 See drivers/char/README.epca and
611 Documentation/serial/digiepca.txt.
613 disable= [IPV6]
614 See Documentation/networking/ipv6.txt.
616 disable_ipv6= [IPV6]
617 See Documentation/networking/ipv6.txt.
619 disable_mtrr_cleanup [X86]
620 The kernel tries to adjust MTRR layout from continuous
621 to discrete, to make X server driver able to add WB
622 entry later. This parameter disables that.
624 disable_mtrr_trim [X86, Intel and AMD only]
625 By default the kernel will trim any uncacheable
626 memory out of your available memory pool based on
627 MTRR settings. This parameter disables that behavior,
628 possibly causing your machine to run very slowly.
630 disable_timer_pin_1 [X86]
631 Disable PIN 1 of APIC timer
632 Can be useful to work around chipset bugs.
634 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
635 this option disables the debugging code at boot.
637 dma_debug_entries=<number>
638 This option allows to tune the number of preallocated
639 entries for DMA-API debugging code. One entry is
640 required per DMA-API allocation. Use this if the
641 DMA-API debugging code disables itself because the
642 architectural default is too low.
644 dma_debug_driver=<driver_name>
645 With this option the DMA-API debugging driver
646 filter feature can be enabled at boot time. Just
647 pass the driver to filter for as the parameter.
648 The filter can be disabled or changed to another
649 driver later using sysfs.
651 dscc4.setup= [NET]
653 dynamic_printk Enables pr_debug()/dev_dbg() calls if
654 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
655 These can also be switched on/off via
656 <debugfs>/dynamic_printk/modules
658 earlycon= [KNL] Output early console device and options.
659 uart[8250],io,<addr>[,options]
660 uart[8250],mmio,<addr>[,options]
661 uart[8250],mmio32,<addr>[,options]
662 Start an early, polled-mode console on the 8250/16550
663 UART at the specified I/O port or MMIO address.
664 MMIO inter-register address stride is either 8bit (mmio)
665 or 32bit (mmio32).
666 The options are the same as for ttyS, above.
668 earlyprintk= [X86,SH,BLACKFIN]
669 earlyprintk=vga
670 earlyprintk=serial[,ttySn[,baudrate]]
671 earlyprintk=ttySn[,baudrate]
672 earlyprintk=dbgp[debugController#]
674 Append ",keep" to not disable it when the real console
675 takes over.
677 Only vga or serial or usb debug port at a time.
679 Currently only ttyS0 and ttyS1 are supported.
681 Interaction with the standard serial driver is not
682 very good.
684 The VGA output is eventually overwritten by the real
685 console.
687 ekgdboc= [X86,KGDB] Allow early kernel console debugging
688 ekgdboc=kbd
690 This is desgined to be used in conjunction with
691 the boot argument: earlyprintk=vga
693 edd= [EDD]
694 Format: {"off" | "on" | "skip[mbr]"}
696 eisa_irq_edge= [PARISC,HW]
697 See header of drivers/parisc/eisa.c.
699 elanfreq= [X86-32]
700 See comment before function elanfreq_setup() in
701 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
703 elevator= [IOSCHED]
704 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
705 See Documentation/block/as-iosched.txt and
706 Documentation/block/deadline-iosched.txt for details.
708 elfcorehdr= [IA64,PPC,SH,X86]
709 Specifies physical address of start of kernel core
710 image elf header. Generally kexec loader will
711 pass this option to capture kernel.
712 See Documentation/kdump/kdump.txt for details.
714 enable_mtrr_cleanup [X86]
715 The kernel tries to adjust MTRR layout from continuous
716 to discrete, to make X server driver able to add WB
717 entry later. This parameter enables that.
719 enable_timer_pin_1 [X86]
720 Enable PIN 1 of APIC timer
721 Can be useful to work around chipset bugs
722 (in particular on some ATI chipsets).
723 The kernel tries to set a reasonable default.
725 enforcing [SELINUX] Set initial enforcing status.
726 Format: {"0" | "1"}
727 See security/selinux/Kconfig help text.
728 0 -- permissive (log only, no denials).
729 1 -- enforcing (deny and log).
730 Default value is 0.
731 Value can be changed at runtime via /selinux/enforce.
733 erst_disable [ACPI]
734 Disable Error Record Serialization Table (ERST)
735 support.
737 ether= [HW,NET] Ethernet cards parameters
738 This option is obsoleted by the "netdev=" option, which
739 has equivalent usage. See its documentation for details.
741 failslab=
742 fail_page_alloc=
743 fail_make_request=[KNL]
744 General fault injection mechanism.
745 Format: <interval>,<probability>,<space>,<times>
746 See also /Documentation/fault-injection/.
748 floppy= [HW]
749 See Documentation/blockdev/floppy.txt.
751 force_pal_cache_flush
752 [IA-64] Avoid check_sal_cache_flush which may hang on
753 buggy SAL_CACHE_FLUSH implementations. Using this
754 parameter will force ia64_sal_cache_flush to call
755 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
757 ftrace=[tracer]
758 [FTRACE] will set and start the specified tracer
759 as early as possible in order to facilitate early
760 boot debugging.
762 ftrace_dump_on_oops[=orig_cpu]
763 [FTRACE] will dump the trace buffers on oops.
764 If no parameter is passed, ftrace will dump
765 buffers of all CPUs, but if you pass orig_cpu, it will
766 dump only the buffer of the CPU that triggered the
767 oops.
769 ftrace_filter=[function-list]
770 [FTRACE] Limit the functions traced by the function
771 tracer at boot up. function-list is a comma separated
772 list of functions. This list can be changed at run
773 time by the set_ftrace_filter file in the debugfs
774 tracing directory.
776 ftrace_notrace=[function-list]
777 [FTRACE] Do not trace the functions specified in
778 function-list. This list can be changed at run time
779 by the set_ftrace_notrace file in the debugfs
780 tracing directory.
782 ftrace_graph_filter=[function-list]
783 [FTRACE] Limit the top level callers functions traced
784 by the function graph tracer at boot up.
785 function-list is a comma separated list of functions
786 that can be changed at run time by the
787 set_graph_function file in the debugfs tracing directory.
789 gamecon.map[2|3]=
790 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
791 support via parallel port (up to 5 devices per port)
792 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
793 See also Documentation/input/joystick-parport.txt
795 gamma= [HW,DRM]
797 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
798 Format: off | on
799 default: on
801 gcov_persist= [GCOV] When non-zero (default), profiling data for
802 kernel modules is saved and remains accessible via
803 debugfs, even when the module is unloaded/reloaded.
804 When zero, profiling data is discarded and associated
805 debugfs files are removed at module unload time.
807 gpt [EFI] Forces disk with valid GPT signature but
808 invalid Protective MBR to be treated as GPT.
810 hashdist= [KNL,NUMA] Large hashes allocated during boot
811 are distributed across NUMA nodes. Defaults on
812 for 64bit NUMA, off otherwise.
813 Format: 0 | 1 (for off | on)
815 hcl= [IA-64] SGI's Hardware Graph compatibility layer
817 hd= [EIDE] (E)IDE hard drive subsystem geometry
818 Format: <cyl>,<head>,<sect>
820 hest_disable [ACPI]
821 Disable Hardware Error Source Table (HEST) support;
822 corresponding firmware-first mode error processing
823 logic will be disabled.
825 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
826 size of <nn>. This works even on boxes that have no
827 highmem otherwise. This also works to reduce highmem
828 size on bigger boxes.
830 highres= [KNL] Enable/disable high resolution timer mode.
831 Valid parameters: "on", "off"
832 Default: "on"
834 hisax= [HW,ISDN]
835 See Documentation/isdn/README.HiSax.
837 hlt [BUGS=ARM,SH]
839 hpet= [X86-32,HPET] option to control HPET usage
840 Format: { enable (default) | disable | force |
841 verbose }
842 disable: disable HPET and use PIT instead
843 force: allow force enabled of undocumented chips (ICH4,
844 VIA, nVidia)
845 verbose: show contents of HPET registers during setup
847 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
848 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
849 On x86-64 and powerpc, this option can be specified
850 multiple times interleaved with hugepages= to reserve
851 huge pages of different sizes. Valid pages sizes on
852 x86-64 are 2M (when the CPU supports "pse") and 1G
853 (when the CPU supports the "pdpe1gb" cpuinfo flag)
854 Note that 1GB pages can only be allocated at boot time
855 using hugepages= and not freed afterwards.
857 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
858 terminal devices. Valid values: 0..8
859 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
860 If specified, z/VM IUCV HVC accepts connections
861 from listed z/VM user IDs only.
863 i2c_bus= [HW] Override the default board specific I2C bus speed
864 or register an additional I2C bus that is not
865 registered from board initialization code.
866 Format:
867 <bus_id>,<clkrate>
869 i8042.debug [HW] Toggle i8042 debug mode
870 i8042.direct [HW] Put keyboard port into non-translated mode
871 i8042.dumbkbd [HW] Pretend that controller can only read data from
872 keyboard and cannot control its state
873 (Don't attempt to blink the leds)
874 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
875 i8042.nokbd [HW] Don't check/create keyboard port
876 i8042.noloop [HW] Disable the AUX Loopback command while probing
877 for the AUX port
878 i8042.nomux [HW] Don't check presence of an active multiplexing
879 controller
880 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
881 controllers
882 i8042.notimeout [HW] Ignore timeout condition signalled by conroller
883 i8042.reset [HW] Reset the controller during init and cleanup
884 i8042.unlock [HW] Unlock (ignore) the keylock
886 i810= [HW,DRM]
888 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
889 indicates that the driver is running on unsupported
890 hardware.
891 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
892 does not match list of supported models.
893 i8k.power_status
894 [HW] Report power status in /proc/i8k
895 (disabled by default)
896 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
897 capability is set.
899 icn= [HW,ISDN]
900 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
902 ide-core.nodma= [HW] (E)IDE subsystem
903 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
904 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
905 .cdrom .chs .ignore_cable are additional options
906 See Documentation/ide/ide.txt.
908 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
909 Claim all unknown PCI IDE storage controllers.
911 idle= [X86]
912 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
913 Poll forces a polling idle loop that can slightly
914 improve the performance of waking up a idle CPU, but
915 will use a lot of power and make the system run hot.
916 Not recommended.
917 idle=mwait: On systems which support MONITOR/MWAIT but
918 the kernel chose to not use it because it doesn't save
919 as much power as a normal idle loop, use the
920 MONITOR/MWAIT idle loop anyways. Performance should be
921 the same as idle=poll.
922 idle=halt: Halt is forced to be used for CPU idle.
923 In such case C2/C3 won't be used again.
924 idle=nomwait: Disable mwait for CPU C-states
926 ignore_loglevel [KNL]
927 Ignore loglevel setting - this will print /all/
928 kernel messages to the console. Useful for debugging.
930 ihash_entries= [KNL]
931 Set number of hash buckets for inode cache.
933 ima_audit= [IMA]
934 Format: { "0" | "1" }
935 0 -- integrity auditing messages. (Default)
936 1 -- enable informational integrity auditing messages.
938 ima_hash= [IMA]
939 Format: { "sha1" | "md5" }
940 default: "sha1"
942 ima_tcb [IMA]
943 Load a policy which meets the needs of the Trusted
944 Computing Base. This means IMA will measure all
945 programs exec'd, files mmap'd for exec, and all files
946 opened for read by uid=0.
948 init= [KNL]
949 Format: <full_path>
950 Run specified binary instead of /sbin/init as init
951 process.
953 initcall_debug [KNL] Trace initcalls as they are executed. Useful
954 for working out where the kernel is dying during
955 startup.
957 initrd= [BOOT] Specify the location of the initial ramdisk
959 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
960 Format: <irq>
962 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
963 on
964 Enable intel iommu driver.
965 off
966 Disable intel iommu driver.
967 igfx_off [Default Off]
968 By default, gfx is mapped as normal device. If a gfx
969 device has a dedicated DMAR unit, the DMAR unit is
970 bypassed by not enabling DMAR with this option. In
971 this case, gfx device will use physical address for
972 DMA.
973 forcedac [x86_64]
974 With this option iommu will not optimize to look
975 for io virtual address below 32 bit forcing dual
976 address cycle on pci bus for cards supporting greater
977 than 32 bit addressing. The default is to look
978 for translation below 32 bit and if not available
979 then look in the higher range.
980 strict [Default Off]
981 With this option on every unmap_single operation will
982 result in a hardware IOTLB flush operation as opposed
983 to batching them for performance.
985 intremap= [X86-64, Intel-IOMMU]
986 Format: { on (default) | off | nosid }
987 on enable Interrupt Remapping (default)
988 off disable Interrupt Remapping
989 nosid disable Source ID checking
991 inttest= [IA64]
993 iomem= Disable strict checking of access to MMIO memory
994 strict regions from userspace.
995 relaxed
997 iommu= [x86]
998 off
999 force
1000 noforce
1001 biomerge
1002 panic
1003 nopanic
1004 merge
1005 nomerge
1006 forcesac
1007 soft
1008 pt [x86, IA64]
1010 io7= [HW] IO7 for Marvel based alpha systems
1011 See comment before marvel_specify_io7 in
1012 arch/alpha/kernel/core_marvel.c.
1014 io_delay= [X86] I/O delay method
1015 0x80
1016 Standard port 0x80 based delay
1017 0xed
1018 Alternate port 0xed based delay (needed on some systems)
1019 udelay
1020 Simple two microseconds delay
1021 none
1022 No delay
1024 ip= [IP_PNP]
1025 See Documentation/filesystems/nfs/nfsroot.txt.
1027 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1028 See comment before ip2_setup() in
1029 drivers/char/ip2/ip2base.c.
1031 irqfixup [HW]
1032 When an interrupt is not handled search all handlers
1033 for it. Intended to get systems with badly broken
1034 firmware running.
1036 irqpoll [HW]
1037 When an interrupt is not handled search all handlers
1038 for it. Also check all handlers each timer
1039 interrupt. Intended to get systems with badly broken
1040 firmware running.
1042 isapnp= [ISAPNP]
1043 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1045 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1046 Format:
1047 <cpu number>,...,<cpu number>
1048 or
1049 <cpu number>-<cpu number>
1050 (must be a positive range in ascending order)
1051 or a mixture
1052 <cpu number>,...,<cpu number>-<cpu number>
1054 This option can be used to specify one or more CPUs
1055 to isolate from the general SMP balancing and scheduling
1056 algorithms. You can move a process onto or off an
1057 "isolated" CPU via the CPU affinity syscalls or cpuset.
1058 <cpu number> begins at 0 and the maximum value is
1059 "number of CPUs in system - 1".
1061 This option is the preferred way to isolate CPUs. The
1062 alternative -- manually setting the CPU mask of all
1063 tasks in the system -- can cause problems and
1064 suboptimal load balancer performance.
1066 iucv= [HW,NET]
1068 js= [HW,JOY] Analog joystick
1069 See Documentation/input/joystick.txt.
1071 keepinitrd [HW,ARM]
1073 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1074 specifies the amount of memory usable by the kernel
1075 for non-movable allocations. The requested amount is
1076 spread evenly throughout all nodes in the system. The
1077 remaining memory in each node is used for Movable
1078 pages. In the event, a node is too small to have both
1079 kernelcore and Movable pages, kernelcore pages will
1080 take priority and other nodes will have a larger number
1081 of kernelcore pages. The Movable zone is used for the
1082 allocation of pages that may be reclaimed or moved
1083 by the page migration subsystem. This means that
1084 HugeTLB pages may not be allocated from this zone.
1085 Note that allocations like PTEs-from-HighMem still
1086 use the HighMem zone if it exists, and the Normal
1087 zone if it does not.
1089 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1090 Format: <Controller#>[,poll interval]
1091 The controller # is the number of the ehci usb debug
1092 port as it is probed via PCI. The poll interval is
1093 optional and is the number seconds in between
1094 each poll cycle to the debug port in case you need
1095 the functionality for interrupting the kernel with
1096 gdb or control-c on the dbgp connection. When
1097 not using this parameter you use sysrq-g to break into
1098 the kernel debugger.
1100 kgdboc= [KGDB,HW] kgdb over consoles.
1101 Requires a tty driver that supports console polling,
1102 or a supported polling keyboard driver (non-usb).
1103 Serial only format: <serial_device>[,baud]
1104 keyboard only format: kbd
1105 keyboard and serial format: kbd,<serial_device>[,baud]
1106 Optional Kernel mode setting:
1107 kms, kbd format: kms,kbd
1108 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1110 kgdbwait [KGDB] Stop kernel execution and enter the
1111 kernel debugger at the earliest opportunity.
1113 kmac= [MIPS] korina ethernet MAC address.
1114 Configure the RouterBoard 532 series on-chip
1115 Ethernet adapter MAC address.
1117 kmemleak= [KNL] Boot-time kmemleak enable/disable
1118 Valid arguments: on, off
1119 Default: on
1121 kstack=N [X86] Print N words from the kernel stack
1122 in oops dumps.
1124 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1125 Default is 0 (don't ignore, but inject #GP)
1127 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1128 Default is 1 (enabled)
1130 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1131 Default is 0 (off)
1133 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1134 for all guests.
1135 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1137 kvm-intel.bypass_guest_pf=
1138 [KVM,Intel] Disables bypassing of guest page faults
1139 on Intel chips. Default is 1 (enabled)
1141 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1142 (virtualized MMU) support on capable Intel chips.
1143 Default is 1 (enabled)
1145 kvm-intel.emulate_invalid_guest_state=
1146 [KVM,Intel] Enable emulation of invalid guest states
1147 Default is 0 (disabled)
1149 kvm-intel.flexpriority=
1150 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1151 Default is 1 (enabled)
1153 kvm-intel.unrestricted_guest=
1154 [KVM,Intel] Disable unrestricted guest feature
1155 (virtualized real and unpaged mode) on capable
1156 Intel chips. Default is 1 (enabled)
1158 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1159 feature (tagged TLBs) on capable Intel chips.
1160 Default is 1 (enabled)
1162 l2cr= [PPC]
1164 l3cr= [PPC]
1166 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1167 disabled it.
1169 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1170 in C2 power state.
1172 libata.dma= [LIBATA] DMA control
1173 libata.dma=0 Disable all PATA and SATA DMA
1174 libata.dma=1 PATA and SATA Disk DMA only
1175 libata.dma=2 ATAPI (CDROM) DMA only
1176 libata.dma=4 Compact Flash DMA only
1177 Combinations also work, so libata.dma=3 enables DMA
1178 for disks and CDROMs, but not CFs.
1180 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1181 libata.ignore_hpa=0 keep BIOS limits (default)
1182 libata.ignore_hpa=1 ignore limits, using full disk
1184 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1185 when set.
1186 Format: <int>
1188 libata.force= [LIBATA] Force configurations. The format is comma
1189 separated list of "[ID:]VAL" where ID is
1190 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1191 matching port, link or device. Basically, it matches
1192 the ATA ID string printed on console by libata. If
1193 the whole ID part is omitted, the last PORT and DEVICE
1194 values are used. If ID hasn't been specified yet, the
1195 configuration applies to all ports, links and devices.
1197 If only DEVICE is omitted, the parameter applies to
1198 the port and all links and devices behind it. DEVICE
1199 number of 0 either selects the first device or the
1200 first fan-out link behind PMP device. It does not
1201 select the host link. DEVICE number of 15 selects the
1202 host link and device attached to it.
1204 The VAL specifies the configuration to force. As long
1205 as there's no ambiguity shortcut notation is allowed.
1206 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1207 The following configurations can be forced.
1209 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1210 Any ID with matching PORT is used.
1212 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1214 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1215 udma[/][16,25,33,44,66,100,133] notation is also
1216 allowed.
1218 * [no]ncq: Turn on or off NCQ.
1220 * nohrst, nosrst, norst: suppress hard, soft
1221 and both resets.
1223 * dump_id: dump IDENTIFY data.
1225 If there are multiple matching configurations changing
1226 the same attribute, the last one is used.
1228 memblock=debug [KNL] Enable memblock debug messages.
1230 load_ramdisk= [RAM] List of ramdisks to load from floppy
1231 See Documentation/blockdev/ramdisk.txt.
1233 lockd.nlm_grace_period=P [NFS] Assign grace period.
1234 Format: <integer>
1236 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1237 Format: <integer>
1239 lockd.nlm_timeout=T [NFS] Assign timeout value.
1240 Format: <integer>
1242 lockd.nlm_udpport=M [NFS] Assign UDP port.
1243 Format: <integer>
1245 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1246 Format: <irq>
1248 loglevel= All Kernel Messages with a loglevel smaller than the
1249 console loglevel will be printed to the console. It can
1250 also be changed with klogd or other programs. The
1251 loglevels are defined as follows:
1253 0 (KERN_EMERG) system is unusable
1254 1 (KERN_ALERT) action must be taken immediately
1255 2 (KERN_CRIT) critical conditions
1256 3 (KERN_ERR) error conditions
1257 4 (KERN_WARNING) warning conditions
1258 5 (KERN_NOTICE) normal but significant condition
1259 6 (KERN_INFO) informational
1260 7 (KERN_DEBUG) debug-level messages
1262 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1263 Format: { n | nk | nM }
1264 n must be a power of two. The default size
1265 is set in the kernel config file.
1267 logo.nologo [FB] Disables display of the built-in Linux logo.
1268 This may be used to provide more screen space for
1269 kernel log messages and is useful when debugging
1270 kernel boot problems.
1272 lp=0 [LP] Specify parallel ports to use, e.g,
1273 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1274 lp=reset first parallel port). 'lp=0' disables the
1275 lp=auto printer driver. 'lp=reset' (which can be
1276 specified in addition to the ports) causes
1277 attached printers to be reset. Using
1278 lp=port1,port2,... specifies the parallel ports
1279 to associate lp devices with, starting with
1280 lp0. A port specification may be 'none' to skip
1281 that lp device, or a parport name such as
1282 'parport0'. Specifying 'lp=auto' instead of a
1283 port specification list means that device IDs
1284 from each port should be examined, to see if
1285 an IEEE 1284-compliant printer is attached; if
1286 so, the driver will manage that printer.
1287 See also header of drivers/char/lp.c.
1289 lpj=n [KNL]
1290 Sets loops_per_jiffy to given constant, thus avoiding
1291 time-consuming boot-time autodetection (up to 250 ms per
1292 CPU). 0 enables autodetection (default). To determine
1293 the correct value for your kernel, boot with normal
1294 autodetection and see what value is printed. Note that
1295 on SMP systems the preset will be applied to all CPUs,
1296 which is likely to cause problems if your CPUs need
1297 significantly divergent settings. An incorrect value
1298 will cause delays in the kernel to be wrong, leading to
1299 unpredictable I/O errors and other breakage. Although
1300 unlikely, in the extreme case this might damage your
1301 hardware.
1303 ltpc= [NET]
1304 Format: <io>,<irq>,<dma>
1306 machvec= [IA64] Force the use of a particular machine-vector
1307 (machvec) in a generic kernel.
1308 Example: machvec=hpzx1_swiotlb
1310 machtype= [Loongson] Share the same kernel image file between different
1311 yeeloong laptop.
1312 Example: machtype=lemote-yeeloong-2f-7inch
1314 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1315 than or equal to this physical address is ignored.
1317 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1318 should make use of. maxcpus=n : n >= 0 limits the
1319 kernel to using 'n' processors. n=0 is a special case,
1320 it is equivalent to "nosmp", which also disables
1321 the IO APIC.
1323 max_loop= [LOOP] Maximum number of loopback devices that can
1324 be mounted
1325 Format: <1-256>
1327 mcatest= [IA-64]
1329 mce [X86-32] Machine Check Exception
1331 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1333 md= [HW] RAID subsystems devices and level
1334 See Documentation/md.txt.
1336 mdacon= [MDA]
1337 Format: <first>,<last>
1338 Specifies range of consoles to be captured by the MDA.
1340 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1341 Amount of memory to be used when the kernel is not able
1342 to see the whole system memory or for test.
1343 [X86-32] Use together with memmap= to avoid physical
1344 address space collisions. Without memmap= PCI devices
1345 could be placed at addresses belonging to unused RAM.
1347 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1348 memory.
1350 memchunk=nn[KMG]
1351 [KNL,SH] Allow user to override the default size for
1352 per-device physically contiguous DMA buffers.
1354 memmap=exactmap [KNL,X86] Enable setting of an exact
1355 E820 memory map, as specified by the user.
1356 Such memmap=exactmap lines can be constructed based on
1357 BIOS output or other requirements. See the memmap=nn@ss
1358 option description.
1360 memmap=nn[KMG]@ss[KMG]
1361 [KNL] Force usage of a specific region of memory
1362 Region of memory to be used, from ss to ss+nn.
1364 memmap=nn[KMG]#ss[KMG]
1365 [KNL,ACPI] Mark specific memory as ACPI data.
1366 Region of memory to be used, from ss to ss+nn.
1368 memmap=nn[KMG]$ss[KMG]
1369 [KNL,ACPI] Mark specific memory as reserved.
1370 Region of memory to be used, from ss to ss+nn.
1371 Example: Exclude memory from 0x18690000-0x1869ffff
1372 memmap=64K$0x18690000
1373 or
1374 memmap=0x10000$0x18690000
1376 memory_corruption_check=0/1 [X86]
1377 Some BIOSes seem to corrupt the first 64k of
1378 memory when doing things like suspend/resume.
1379 Setting this option will scan the memory
1380 looking for corruption. Enabling this will
1381 both detect corruption and prevent the kernel
1382 from using the memory being corrupted.
1383 However, its intended as a diagnostic tool; if
1384 repeatable BIOS-originated corruption always
1385 affects the same memory, you can use memmap=
1386 to prevent the kernel from using that memory.
1388 memory_corruption_check_size=size [X86]
1389 By default it checks for corruption in the low
1390 64k, making this memory unavailable for normal
1391 use. Use this parameter to scan for
1392 corruption in more or less memory.
1394 memory_corruption_check_period=seconds [X86]
1395 By default it checks for corruption every 60
1396 seconds. Use this parameter to check at some
1397 other rate. 0 disables periodic checking.
1399 memtest= [KNL,X86] Enable memtest
1400 Format: <integer>
1401 default : 0 <disable>
1402 Specifies the number of memtest passes to be
1403 performed. Each pass selects another test
1404 pattern from a given set of patterns. Memtest
1405 fills the memory with this pattern, validates
1406 memory contents and reserves bad memory
1407 regions that are detected.
1409 meye.*= [HW] Set MotionEye Camera parameters
1410 See Documentation/video4linux/meye.txt.
1412 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1413 Multi-Function General Purpose Timers on AMD Geode
1414 platforms.
1416 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1417 the BIOS has incorrectly applied a workaround. TinyBIOS
1418 version 0.98 is known to be affected, 0.99 fixes the
1419 problem by letting the user disable the workaround.
1421 mga= [HW,DRM]
1423 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1424 physical address is ignored.
1426 mini2440= [ARM,HW,KNL]
1427 Format:[0..2][b][c][t]
1428 Default: "0tb"
1429 MINI2440 configuration specification:
1430 0 - The attached screen is the 3.5" TFT
1431 1 - The attached screen is the 7" TFT
1432 2 - The VGA Shield is attached (1024x768)
1433 Leaving out the screen size parameter will not load
1434 the TFT driver, and the framebuffer will be left
1435 unconfigured.
1436 b - Enable backlight. The TFT backlight pin will be
1437 linked to the kernel VESA blanking code and a GPIO
1438 LED. This parameter is not necessary when using the
1439 VGA shield.
1440 c - Enable the s3c camera interface.
1441 t - Reserved for enabling touchscreen support. The
1442 touchscreen support is not enabled in the mainstream
1443 kernel as of 2.6.30, a preliminary port can be found
1444 in the "bleeding edge" mini2440 support kernel at
1445 http://repo.or.cz/w/linux-2.6/mini2440.git
1447 mminit_loglevel=
1448 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1449 parameter allows control of the logging verbosity for
1450 the additional memory initialisation checks. A value
1451 of 0 disables mminit logging and a level of 4 will
1452 log everything. Information is printed at KERN_DEBUG
1453 so loglevel=8 may also need to be specified.
1455 mousedev.tap_time=
1456 [MOUSE] Maximum time between finger touching and
1457 leaving touchpad surface for touch to be considered
1458 a tap and be reported as a left button click (for
1459 touchpads working in absolute mode only).
1460 Format: <msecs>
1461 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1462 reporting absolute coordinates, such as tablets
1463 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1464 reporting absolute coordinates, such as tablets
1466 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1467 is similar to kernelcore except it specifies the
1468 amount of memory used for migratable allocations.
1469 If both kernelcore and movablecore is specified,
1470 then kernelcore will be at *least* the specified
1471 value but may be more. If movablecore on its own
1472 is specified, the administrator must be careful
1473 that the amount of memory usable for all allocations
1474 is not too small.
1476 MTD_Partition= [MTD]
1477 Format: <name>,<region-number>,<size>,<offset>
1479 MTD_Region= [MTD] Format:
1480 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1482 mtdparts= [MTD]
1483 See drivers/mtd/cmdlinepart.c.
1485 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1487 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1489 boundary - index of last SLC block on Flex-OneNAND.
1490 The remaining blocks are configured as MLC blocks.
1491 lock - Configure if Flex-OneNAND boundary should be locked.
1492 Once locked, the boundary cannot be changed.
1493 1 indicates lock status, 0 indicates unlock status.
1495 mtdset= [ARM]
1496 ARM/S3C2412 JIVE boot control
1498 See arch/arm/mach-s3c2412/mach-jive.c
1500 mtouchusb.raw_coordinates=
1501 [HW] Make the MicroTouch USB driver use raw coordinates
1502 ('y', default) or cooked coordinates ('n')
1504 mtrr_chunk_size=nn[KMG] [X86]
1505 used for mtrr cleanup. It is largest continuous chunk
1506 that could hold holes aka. UC entries.
1508 mtrr_gran_size=nn[KMG] [X86]
1509 Used for mtrr cleanup. It is granularity of mtrr block.
1510 Default is 1.
1511 Large value could prevent small alignment from
1512 using up MTRRs.
1514 mtrr_spare_reg_nr=n [X86]
1515 Format: <integer>
1516 Range: 0,7 : spare reg number
1517 Default : 1
1518 Used for mtrr cleanup. It is spare mtrr entries number.
1519 Set to 2 or more if your graphical card needs more.
1521 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1523 netdev= [NET] Network devices parameters
1524 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1525 Note that mem_start is often overloaded to mean
1526 something different and driver-specific.
1527 This usage is only documented in each driver source
1528 file if at all.
1530 nf_conntrack.acct=
1531 [NETFILTER] Enable connection tracking flow accounting
1532 0 to disable accounting
1533 1 to enable accounting
1534 Default value is 0.
1536 nfsaddrs= [NFS]
1537 See Documentation/filesystems/nfs/nfsroot.txt.
1539 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1540 See Documentation/filesystems/nfs/nfsroot.txt.
1542 nfs.callback_tcpport=
1543 [NFS] set the TCP port on which the NFSv4 callback
1544 channel should listen.
1546 nfs.cache_getent=
1547 [NFS] sets the pathname to the program which is used
1548 to update the NFS client cache entries.
1550 nfs.cache_getent_timeout=
1551 [NFS] sets the timeout after which an attempt to
1552 update a cache entry is deemed to have failed.
1554 nfs.idmap_cache_timeout=
1555 [NFS] set the maximum lifetime for idmapper cache
1556 entries.
1558 nfs.enable_ino64=
1559 [NFS] enable 64-bit inode numbers.
1560 If zero, the NFS client will fake up a 32-bit inode
1561 number for the readdir() and stat() syscalls instead
1562 of returning the full 64-bit number.
1563 The default is to return 64-bit inode numbers.
1565 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1566 when a NMI is triggered.
1567 Format: [state][,regs][,debounce][,die]
1569 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1570 Format: [panic,][num]
1571 Valid num: 0,1,2
1572 0 - turn nmi_watchdog off
1573 1 - use the IO-APIC timer for the NMI watchdog
1574 2 - use the local APIC for the NMI watchdog using
1575 a performance counter. Note: This will use one
1576 performance counter and the local APIC's performance
1577 vector.
1578 When panic is specified, panic when an NMI watchdog
1579 timeout occurs.
1580 This is useful when you use a panic=... timeout and
1581 need the box quickly up again.
1582 Instead of 1 and 2 it is possible to use the following
1583 symbolic names: lapic and ioapic
1584 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1586 netpoll.carrier_timeout=
1587 [NET] Specifies amount of time (in seconds) that
1588 netpoll should wait for a carrier. By default netpoll
1589 waits 4 seconds.
1591 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1592 emulation library even if a 387 maths coprocessor
1593 is present.
1595 no_console_suspend
1596 [HW] Never suspend the console
1597 Disable suspending of consoles during suspend and
1598 hibernate operations. Once disabled, debugging
1599 messages can reach various consoles while the rest
1600 of the system is being put to sleep (ie, while
1601 debugging driver suspend/resume hooks). This may
1602 not work reliably with all consoles, but is known
1603 to work with serial and VGA consoles.
1605 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1606 caches in the slab allocator. Saves per-node memory,
1607 but will impact performance.
1609 noalign [KNL,ARM]
1611 noapic [SMP,APIC] Tells the kernel to not make use of any
1612 IOAPICs that may be present in the system.
1614 nobats [PPC] Do not use BATs for mapping kernel lowmem
1615 on "Classic" PPC cores.
1617 nocache [ARM]
1619 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1621 nodelayacct [KNL] Disable per-task delay accounting
1623 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1625 nodsp [SH] Disable hardware DSP at boot time.
1627 noefi [X86] Disable EFI runtime services support.
1629 noexec [IA-64]
1631 noexec [X86]
1632 On X86-32 available only on PAE configured kernels.
1633 noexec=on: enable non-executable mappings (default)
1634 noexec=off: disable non-executable mappings
1636 noexec32 [X86-64]
1637 This affects only 32-bit executables.
1638 noexec32=on: enable non-executable mappings (default)
1639 read doesn't imply executable mappings
1640 noexec32=off: disable non-executable mappings
1641 read implies executable mappings
1643 nofpu [SH] Disable hardware FPU at boot time.
1645 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1646 register save and restore. The kernel will only save
1647 legacy floating-point registers on task switch.
1649 noxsave [BUGS=X86] Disables x86 extended register state save
1650 and restore using xsave. The kernel will fallback to
1651 enabling legacy floating-point and sse state.
1653 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1654 wfi(ARM) instruction doesn't work correctly and not to
1655 use it. This is also useful when using JTAG debugger.
1657 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1658 instruction doesn't work correctly and not to
1659 use it.
1661 no_file_caps Tells the kernel not to honor file capabilities. The
1662 only way then for a file to be executed with privilege
1663 is to be setuid root or executed by root.
1665 nohalt [IA-64] Tells the kernel not to use the power saving
1666 function PAL_HALT_LIGHT when idle. This increases
1667 power-consumption. On the positive side, it reduces
1668 interrupt wake-up latency, which may improve performance
1669 in certain environments such as networked servers or
1670 real-time systems.
1672 nohz= [KNL] Boottime enable/disable dynamic ticks
1673 Valid arguments: on, off
1674 Default: on
1676 noiotrap [SH] Disables trapped I/O port accesses.
1678 noirqdebug [X86-32] Disables the code which attempts to detect and
1679 disable unhandled interrupt sources.
1681 no_timer_check [X86,APIC] Disables the code which tests for
1682 broken timer IRQ sources.
1684 noisapnp [ISAPNP] Disables ISA PnP code.
1686 noinitrd [RAM] Tells the kernel not to load any configured
1687 initial RAM disk.
1689 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1690 remapping.
1691 [Deprecated - use intremap=off]
1693 nointroute [IA-64]
1695 nojitter [IA64] Disables jitter checking for ITC timers.
1697 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1699 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1701 noltlbs [PPC] Do not use large page/tlb entries for kernel
1702 lowmem mapping on PPC40x.
1704 nomca [IA-64] Disable machine check abort handling
1706 nomce [X86-32] Machine Check Exception
1708 nomfgpt [X86-32] Disable Multi-Function General Purpose
1709 Timer usage (for AMD Geode machines).
1711 nopat [X86] Disable PAT (page attribute table extension of
1712 pagetables) support.
1714 norandmaps Don't use address space randomization. Equivalent to
1715 echo 0 > /proc/sys/kernel/randomize_va_space
1717 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1719 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1720 with UP alternatives
1722 noresidual [PPC] Don't use residual data on PReP machines.
1724 noresume [SWSUSP] Disables resume and restores original swap
1725 space.
1727 no-scroll [VGA] Disables scrollback.
1728 This is required for the Braillex ib80-piezo Braille
1729 reader made by F.H. Papenmeier (Germany).
1731 nosbagart [IA-64]
1733 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1735 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1736 and disable the IO APIC. legacy for "maxcpus=0".
1738 nosoftlockup [KNL] Disable the soft-lockup detector.
1740 noswapaccount [KNL] Disable accounting of swap in memory resource
1741 controller. (See Documentation/cgroups/memory.txt)
1743 nosync [HW,M68K] Disables sync negotiation for all devices.
1745 notsc [BUGS=X86-32] Disable Time Stamp Counter
1747 nousb [USB] Disable the USB subsystem
1749 nowatchdog [KNL] Disable the lockup detector (NMI watchdog).
1751 nowb [ARM]
1753 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1755 nptcg= [IA64] Override max number of concurrent global TLB
1756 purges which is reported from either PAL_VM_SUMMARY or
1757 SAL PALO.
1759 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1760 could support. nr_cpus=n : n >= 1 limits the kernel to
1761 supporting 'n' processors. Later in runtime you can not
1762 use hotplug cpu feature to put more cpu back to online.
1763 just like you compile the kernel NR_CPUS=n
1765 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1767 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1768 one of ['zone', 'node', 'default'] can be specified
1769 This can be set from sysctl after boot.
1770 See Documentation/sysctl/vm.txt for details.
1772 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1773 See Documentation/debugging-via-ohci1394.txt for more
1774 info.
1776 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1777 Rather than timing out after 20 ms if an EC
1778 command is not properly ACKed, override the length
1779 of the timeout. We have interrupts disabled while
1780 waiting for the ACK, so if this is set too high
1781 interrupts *may* be lost!
1783 omap_mux= [OMAP] Override bootloader pin multiplexing.
1784 Format: <mux_mode0.mode_name=value>...
1785 For example, to override I2C bus2:
1786 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1788 oprofile.timer= [HW]
1789 Use timer interrupt instead of performance counters
1791 oprofile.cpu_type= Force an oprofile cpu type
1792 This might be useful if you have an older oprofile
1793 userland or if you want common events.
1794 Format: { arch_perfmon }
1795 arch_perfmon: [X86] Force use of architectural
1796 perfmon on Intel CPUs instead of the
1797 CPU specific event set.
1799 OSS [HW,OSS]
1800 See Documentation/sound/oss/oss-parameters.txt
1802 panic= [KNL] Kernel behaviour on panic
1803 Format: <timeout>
1805 parkbd.port= [HW] Parallel port number the keyboard adapter is
1806 connected to, default is 0.
1807 Format: <parport#>
1808 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1809 0 for XT, 1 for AT (default is AT).
1810 Format: <mode>
1812 parport= [HW,PPT] Specify parallel ports. 0 disables.
1813 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1814 Use 'auto' to force the driver to use any
1815 IRQ/DMA settings detected (the default is to
1816 ignore detected IRQ/DMA settings because of
1817 possible conflicts). You can specify the base
1818 address, IRQ, and DMA settings; IRQ and DMA
1819 should be numbers, or 'auto' (for using detected
1820 settings on that particular port), or 'nofifo'
1821 (to avoid using a FIFO even if it is detected).
1822 Parallel ports are assigned in the order they
1823 are specified on the command line, starting
1824 with parport0.
1826 parport_init_mode= [HW,PPT]
1827 Configure VIA parallel port to operate in
1828 a specific mode. This is necessary on Pegasos
1829 computer where firmware has no options for setting
1830 up parallel port mode and sets it to spp.
1831 Currently this function knows 686a and 8231 chips.
1832 Format: [spp|ps2|epp|ecp|ecpepp]
1834 pause_on_oops=
1835 Halt all CPUs after the first oops has been printed for
1836 the specified number of seconds. This is to be used if
1837 your oopses keep scrolling off the screen.
1839 pcbit= [HW,ISDN]
1841 pcd. [PARIDE]
1842 See header of drivers/block/paride/pcd.c.
1843 See also Documentation/blockdev/paride.txt.
1845 pci=option[,option...] [PCI] various PCI subsystem options:
1846 earlydump [X86] dump PCI config space before the kernel
1847 changes anything
1848 off [X86] don't probe for the PCI bus
1849 bios [X86-32] force use of PCI BIOS, don't access
1850 the hardware directly. Use this if your machine
1851 has a non-standard PCI host bridge.
1852 nobios [X86-32] disallow use of PCI BIOS, only direct
1853 hardware access methods are allowed. Use this
1854 if you experience crashes upon bootup and you
1855 suspect they are caused by the BIOS.
1856 conf1 [X86] Force use of PCI Configuration
1857 Mechanism 1.
1858 conf2 [X86] Force use of PCI Configuration
1859 Mechanism 2.
1860 noaer [PCIE] If the PCIEAER kernel config parameter is
1861 enabled, this kernel boot option can be used to
1862 disable the use of PCIE advanced error reporting.
1863 nodomains [PCI] Disable support for multiple PCI
1864 root domains (aka PCI segments, in ACPI-speak).
1865 nommconf [X86] Disable use of MMCONFIG for PCI
1866 Configuration
1867 check_enable_amd_mmconf [X86] check for and enable
1868 properly configured MMIO access to PCI
1869 config space on AMD family 10h CPU
1870 nomsi [MSI] If the PCI_MSI kernel config parameter is
1871 enabled, this kernel boot option can be used to
1872 disable the use of MSI interrupts system-wide.
1873 noioapicquirk [APIC] Disable all boot interrupt quirks.
1874 Safety option to keep boot IRQs enabled. This
1875 should never be necessary.
1876 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1877 primary IO-APIC for bridges that cannot disable
1878 boot IRQs. This fixes a source of spurious IRQs
1879 when the system masks IRQs.
1880 noioapicreroute [APIC] Disable workaround that uses the
1881 boot IRQ equivalent of an IRQ that connects to
1882 a chipset where boot IRQs cannot be disabled.
1883 The opposite of ioapicreroute.
1884 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1885 routing table. These calls are known to be buggy
1886 on several machines and they hang the machine
1887 when used, but on other computers it's the only
1888 way to get the interrupt routing table. Try
1889 this option if the kernel is unable to allocate
1890 IRQs or discover secondary PCI buses on your
1891 motherboard.
1892 rom [X86] Assign address space to expansion ROMs.
1893 Use with caution as certain devices share
1894 address decoders between ROMs and other
1895 resources.
1896 norom [X86] Do not assign address space to
1897 expansion ROMs that do not already have
1898 BIOS assigned address ranges.
1899 nobar [X86] Do not assign address space to the
1900 BARs that weren't assigned by the BIOS.
1901 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1902 assigned automatically to PCI devices. You can
1903 make the kernel exclude IRQs of your ISA cards
1904 this way.
1905 pirqaddr=0xAAAAA [X86] Specify the physical address
1906 of the PIRQ table (normally generated
1907 by the BIOS) if it is outside the
1908 F0000h-100000h range.
1909 lastbus=N [X86] Scan all buses thru bus #N. Can be
1910 useful if the kernel is unable to find your
1911 secondary buses and you want to tell it
1912 explicitly which ones they are.
1913 assign-busses [X86] Always assign all PCI bus
1914 numbers ourselves, overriding
1915 whatever the firmware may have done.
1916 usepirqmask [X86] Honor the possible IRQ mask stored
1917 in the BIOS $PIR table. This is needed on
1918 some systems with broken BIOSes, notably
1919 some HP Pavilion N5400 and Omnibook XE3
1920 notebooks. This will have no effect if ACPI
1921 IRQ routing is enabled.
1922 noacpi [X86] Do not use ACPI for IRQ routing
1923 or for PCI scanning.
1924 use_crs [X86] Use PCI host bridge window information
1925 from ACPI. On BIOSes from 2008 or later, this
1926 is enabled by default. If you need to use this,
1927 please report a bug.
1928 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1929 If you need to use this, please report a bug.
1930 routeirq Do IRQ routing for all PCI devices.
1931 This is normally done in pci_enable_device(),
1932 so this option is a temporary workaround
1933 for broken drivers that don't call it.
1934 skip_isa_align [X86] do not align io start addr, so can
1935 handle more pci cards
1936 firmware [ARM] Do not re-enumerate the bus but instead
1937 just use the configuration from the
1938 bootloader. This is currently used on
1939 IXP2000 systems where the bus has to be
1940 configured a certain way for adjunct CPUs.
1941 noearly [X86] Don't do any early type 1 scanning.
1942 This might help on some broken boards which
1943 machine check when some devices' config space
1944 is read. But various workarounds are disabled
1945 and some IOMMU drivers will not work.
1946 bfsort Sort PCI devices into breadth-first order.
1947 This sorting is done to get a device
1948 order compatible with older (<= 2.4) kernels.
1949 nobfsort Don't sort PCI devices into breadth-first order.
1950 cbiosize=nn[KMG] The fixed amount of bus space which is
1951 reserved for the CardBus bridge's IO window.
1952 The default value is 256 bytes.
1953 cbmemsize=nn[KMG] The fixed amount of bus space which is
1954 reserved for the CardBus bridge's memory
1955 window. The default value is 64 megabytes.
1956 resource_alignment=
1957 Format:
1958 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1959 Specifies alignment and device to reassign
1960 aligned memory resources.
1961 If <order of align> is not specified,
1962 PAGE_SIZE is used as alignment.
1963 PCI-PCI bridge can be specified, if resource
1964 windows need to be expanded.
1965 ecrc= Enable/disable PCIe ECRC (transaction layer
1966 end-to-end CRC checking).
1967 bios: Use BIOS/firmware settings. This is the
1968 the default.
1969 off: Turn ECRC off
1970 on: Turn ECRC on.
1972 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1973 Management.
1974 off Disable ASPM.
1975 force Enable ASPM even on devices that claim not to support it.
1976 WARNING: Forcing ASPM on may cause system lockups.
1978 pcie_ports= [PCIE] PCIe ports handling:
1979 auto Ask the BIOS whether or not to use native PCIe services
1980 associated with PCIe ports (PME, hot-plug, AER). Use
1981 them only if that is allowed by the BIOS.
1982 native Use native PCIe services associated with PCIe ports
1983 unconditionally.
1984 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
1985 ports driver.
1987 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
1988 nomsi Do not use MSI for native PCIe PME signaling (this makes
1989 all PCIe root ports use INTx for all services).
1991 pcmv= [HW,PCMCIA] BadgePAD 4
1993 pd. [PARIDE]
1994 See Documentation/blockdev/paride.txt.
1996 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1997 boot time.
1998 Format: { 0 | 1 }
1999 See arch/parisc/kernel/pdc_chassis.c
2001 percpu_alloc= Select which percpu first chunk allocator to use.
2002 Currently supported values are "embed" and "page".
2003 Archs may support subset or none of the selections.
2004 See comments in mm/percpu.c for details on each
2005 allocator. This parameter is primarily for debugging
2006 and performance comparison.
2008 pf. [PARIDE]
2009 See Documentation/blockdev/paride.txt.
2011 pg. [PARIDE]
2012 See Documentation/blockdev/paride.txt.
2014 pirq= [SMP,APIC] Manual mp-table setup
2015 See Documentation/x86/i386/IO-APIC.txt.
2017 plip= [PPT,NET] Parallel port network link
2018 Format: { parport<nr> | timid | 0 }
2019 See also Documentation/parport.txt.
2021 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2022 Override pmtimer IOPort with a hex value.
2023 e.g. pmtmr=0x508
2025 pnp.debug [PNP]
2026 Enable PNP debug messages. This depends on the
2027 CONFIG_PNP_DEBUG_MESSAGES option.
2029 pnpacpi= [ACPI]
2030 { off }
2032 pnpbios= [ISAPNP]
2033 { on | off | curr | res | no-curr | no-res }
2035 pnp_reserve_irq=
2036 [ISAPNP] Exclude IRQs for the autoconfiguration
2038 pnp_reserve_dma=
2039 [ISAPNP] Exclude DMAs for the autoconfiguration
2041 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2042 Ranges are in pairs (I/O port base and size).
2044 pnp_reserve_mem=
2045 [ISAPNP] Exclude memory regions for the
2046 autoconfiguration.
2047 Ranges are in pairs (memory base and size).
2049 ports= [IP_VS_FTP] IPVS ftp helper module
2050 Default is 21.
2051 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2052 may be specified.
2053 Format: <port>,<port>....
2055 print-fatal-signals=
2056 [KNL] debug: print fatal signals
2058 If enabled, warn about various signal handling
2059 related application anomalies: too many signals,
2060 too many POSIX.1 timers, fatal signals causing a
2061 coredump - etc.
2063 If you hit the warning due to signal overflow,
2064 you might want to try "ulimit -i unlimited".
2066 default: off.
2068 printk.time= Show timing data prefixed to each printk message line
2069 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2071 processor.max_cstate= [HW,ACPI]
2072 Limit processor to maximum C-state
2073 max_cstate=9 overrides any DMI blacklist limit.
2075 processor.nocst [HW,ACPI]
2076 Ignore the _CST method to determine C-states,
2077 instead using the legacy FADT method
2079 profile= [KNL] Enable kernel profiling via /proc/profile
2080 Format: [schedule,]<number>
2081 Param: "schedule" - profile schedule points.
2082 Param: <number> - step/bucket size as a power of 2 for
2083 statistical time based profiling.
2084 Param: "sleep" - profile D-state sleeping (millisecs).
2085 Requires CONFIG_SCHEDSTATS
2086 Param: "kvm" - profile VM exits.
2088 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2089 before loading.
2090 See Documentation/blockdev/ramdisk.txt.
2092 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2093 probe for; one of (bare|imps|exps|lifebook|any).
2094 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2095 per second.
2096 psmouse.resetafter= [HW,MOUSE]
2097 Try to reset the device after so many bad packets
2098 (0 = never).
2099 psmouse.resolution=
2100 [HW,MOUSE] Set desired mouse resolution, in dpi.
2101 psmouse.smartscroll=
2102 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2103 0 = disabled, 1 = enabled (default).
2105 pt. [PARIDE]
2106 See Documentation/blockdev/paride.txt.
2108 pty.legacy_count=
2109 [KNL] Number of legacy pty's. Overwrites compiled-in
2110 default number.
2112 quiet [KNL] Disable most log messages
2114 r128= [HW,DRM]
2116 raid= [HW,RAID]
2117 See Documentation/md.txt.
2119 ramdisk_blocksize= [RAM]
2120 See Documentation/blockdev/ramdisk.txt.
2122 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2123 See Documentation/blockdev/ramdisk.txt.
2125 rcupdate.blimit= [KNL,BOOT]
2126 Set maximum number of finished RCU callbacks to process
2127 in one batch.
2129 rcupdate.qhimark= [KNL,BOOT]
2130 Set threshold of queued
2131 RCU callbacks over which batch limiting is disabled.
2133 rcupdate.qlowmark= [KNL,BOOT]
2134 Set threshold of queued RCU callbacks below which
2135 batch limiting is re-enabled.
2137 rdinit= [KNL]
2138 Format: <full_path>
2139 Run specified binary instead of /init from the ramdisk,
2140 used for early userspace startup. See initrd.
2142 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2143 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2144 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2146 relax_domain_level=
2147 [KNL, SMP] Set scheduler's default relax_domain_level.
2148 See Documentation/cgroups/cpusets.txt.
2150 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2152 reservetop= [X86-32]
2153 Format: nn[KMG]
2154 Reserves a hole at the top of the kernel virtual
2155 address space.
2157 reset_devices [KNL] Force drivers to reset the underlying device
2158 during initialization.
2160 resume= [SWSUSP]
2161 Specify the partition device for software suspend
2163 resume_offset= [SWSUSP]
2164 Specify the offset from the beginning of the partition
2165 given by "resume=" at which the swap header is located,
2166 in <PAGE_SIZE> units (needed only for swap files).
2167 See Documentation/power/swsusp-and-swap-files.txt
2169 retain_initrd [RAM] Keep initrd memory after extraction
2171 rhash_entries= [KNL,NET]
2172 Set number of hash buckets for route cache
2174 riscom8= [HW,SERIAL]
2175 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2177 ro [KNL] Mount root device read-only on boot
2179 root= [KNL] Root filesystem
2181 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2182 mount the root filesystem
2184 rootflags= [KNL] Set root filesystem mount option string
2186 rootfstype= [KNL] Set root filesystem type
2188 rootwait [KNL] Wait (indefinitely) for root device to show up.
2189 Useful for devices that are detected asynchronously
2190 (e.g. USB and MMC devices).
2192 rw [KNL] Mount root device read-write on boot
2194 S [KNL] Run init in single mode
2196 sa1100ir [NET]
2197 See drivers/net/irda/sa1100_ir.c.
2199 sbni= [NET] Granch SBNI12 leased line adapter
2201 sched_debug [KNL] Enables verbose scheduler debug messages.
2203 security= [SECURITY] Choose a security module to enable at boot.
2204 If this boot parameter is not specified, only the first
2205 security module asking for security registration will be
2206 loaded. An invalid security module name will be treated
2207 as if no module has been chosen.
2209 selinux= [SELINUX] Disable or enable SELinux at boot time.
2210 Format: { "0" | "1" }
2211 See security/selinux/Kconfig help text.
2212 0 -- disable.
2213 1 -- enable.
2214 Default value is set via kernel config option.
2215 If enabled at boot time, /selinux/disable can be used
2216 later to disable prior to initial policy load.
2218 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2219 Format: { "0" | "1" }
2220 See security/apparmor/Kconfig help text
2221 0 -- disable.
2222 1 -- enable.
2223 Default value is set via kernel config option.
2225 serialnumber [BUGS=X86-32]
2227 shapers= [NET]
2228 Maximal number of shapers.
2230 show_msr= [x86] show boot-time MSR settings
2231 Format: { <integer> }
2232 Show boot-time (BIOS-initialized) MSR settings.
2233 The parameter means the number of CPUs to show,
2234 for example 1 means boot CPU only.
2236 simeth= [IA-64]
2237 simscsi=
2239 slram= [HW,MTD]
2241 slub_debug[=options[,slabs]] [MM, SLUB]
2242 Enabling slub_debug allows one to determine the
2243 culprit if slab objects become corrupted. Enabling
2244 slub_debug can create guard zones around objects and
2245 may poison objects when not in use. Also tracks the
2246 last alloc / free. For more information see
2247 Documentation/vm/slub.txt.
2249 slub_max_order= [MM, SLUB]
2250 Determines the maximum allowed order for slabs.
2251 A high setting may cause OOMs due to memory
2252 fragmentation. For more information see
2253 Documentation/vm/slub.txt.
2255 slub_min_objects= [MM, SLUB]
2256 The minimum number of objects per slab. SLUB will
2257 increase the slab order up to slub_max_order to
2258 generate a sufficiently large slab able to contain
2259 the number of objects indicated. The higher the number
2260 of objects the smaller the overhead of tracking slabs
2261 and the less frequently locks need to be acquired.
2262 For more information see Documentation/vm/slub.txt.
2264 slub_min_order= [MM, SLUB]
2265 Determines the mininum page order for slabs. Must be
2266 lower than slub_max_order.
2267 For more information see Documentation/vm/slub.txt.
2269 slub_nomerge [MM, SLUB]
2270 Disable merging of slabs with similar size. May be
2271 necessary if there is some reason to distinguish
2272 allocs to different slabs. Debug options disable
2273 merging on their own.
2274 For more information see Documentation/vm/slub.txt.
2276 smart2= [HW]
2277 Format: <io1>[,<io2>[,...,<io8>]]
2279 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2280 attempt to substitute SMP alternatives once at boot.
2282 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2283 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2284 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2285 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2286 smsc-ircc2.ircc_irq= [HW] IRQ line
2287 smsc-ircc2.ircc_dma= [HW] DMA channel
2288 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2289 0: Toshiba Satellite 1800 (GP data pin select)
2290 1: Fast pin select (default)
2291 2: ATC IRMode
2293 softlockup_panic=
2294 [KNL] Should the soft-lockup detector generate panics.
2296 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2297 See Documentation/sonypi.txt
2299 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2300 See Documentation/serial/specialix.txt.
2302 spia_io_base= [HW,MTD]
2303 spia_fio_base=
2304 spia_pedr=
2305 spia_peddr=
2307 stacktrace [FTRACE]
2308 Enabled the stack tracer on boot up.
2310 sti= [PARISC,HW]
2311 Format: <num>
2312 Set the STI (builtin display/keyboard on the HP-PARISC
2313 machines) console (graphic card) which should be used
2314 as the initial boot-console.
2315 See also comment in drivers/video/console/sticore.c.
2317 sti_font= [HW]
2318 See comment in drivers/video/console/sticore.c.
2320 stifb= [HW]
2321 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2323 sunrpc.min_resvport=
2324 sunrpc.max_resvport=
2325 [NFS,SUNRPC]
2326 SunRPC servers often require that client requests
2327 originate from a privileged port (i.e. a port in the
2328 range 0 < portnr < 1024).
2329 An administrator who wishes to reserve some of these
2330 ports for other uses may adjust the range that the
2331 kernel's sunrpc client considers to be privileged
2332 using these two parameters to set the minimum and
2333 maximum port values.
2335 sunrpc.pool_mode=
2336 [NFS]
2337 Control how the NFS server code allocates CPUs to
2338 service thread pools. Depending on how many NICs
2339 you have and where their interrupts are bound, this
2340 option will affect which CPUs will do NFS serving.
2341 Note: this parameter cannot be changed while the
2342 NFS server is running.
2344 auto the server chooses an appropriate mode
2345 automatically using heuristics
2346 global a single global pool contains all CPUs
2347 percpu one pool for each CPU
2348 pernode one pool for each NUMA node (equivalent
2349 to global on non-NUMA machines)
2351 sunrpc.tcp_slot_table_entries=
2352 sunrpc.udp_slot_table_entries=
2353 [NFS,SUNRPC]
2354 Sets the upper limit on the number of simultaneous
2355 RPC calls that can be sent from the client to a
2356 server. Increasing these values may allow you to
2357 improve throughput, but will also increase the
2358 amount of memory reserved for use by the client.
2360 swiotlb= [IA-64] Number of I/O TLB slabs
2362 switches= [HW,M68k]
2364 sysrq_always_enabled
2365 [KNL]
2366 Ignore sysrq setting - this boot parameter will
2367 neutralize any effect of /proc/sys/kernel/sysrq.
2368 Useful for debugging.
2370 tdfx= [HW,DRM]
2372 test_suspend= [SUSPEND]
2373 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2374 standby suspend) as the system sleep state to briefly
2375 enter during system startup. The system is woken from
2376 this state using a wakeup-capable RTC alarm.
2378 thash_entries= [KNL,NET]
2379 Set number of hash buckets for TCP connection
2381 thermal.act= [HW,ACPI]
2382 -1: disable all active trip points in all thermal zones
2383 <degrees C>: override all lowest active trip points
2385 thermal.crt= [HW,ACPI]
2386 -1: disable all critical trip points in all thermal zones
2387 <degrees C>: override all critical trip points
2389 thermal.nocrt= [HW,ACPI]
2390 Set to disable actions on ACPI thermal zone
2391 critical and hot trip points.
2393 thermal.off= [HW,ACPI]
2394 1: disable ACPI thermal control
2396 thermal.psv= [HW,ACPI]
2397 -1: disable all passive trip points
2398 <degrees C>: override all passive trip points to this
2399 value
2401 thermal.tzp= [HW,ACPI]
2402 Specify global default ACPI thermal zone polling rate
2403 <deci-seconds>: poll all this frequency
2404 0: no polling (default)
2406 topology= [S390]
2407 Format: {off | on}
2408 Specify if the kernel should make use of the cpu
2409 topology informations if the hardware supports these.
2410 The scheduler will make use of these informations and
2411 e.g. base its process migration decisions on it.
2412 Default is off.
2414 tp720= [HW,PS2]
2416 tpm_suspend_pcr=[HW,TPM]
2417 Format: integer pcr id
2418 Specify that at suspend time, the tpm driver
2419 should extend the specified pcr with zeros,
2420 as a workaround for some chips which fail to
2421 flush the last written pcr on TPM_SaveState.
2422 This will guarantee that all the other pcrs
2423 are saved.
2425 trace_buf_size=nn[KMG]
2426 [FTRACE] will set tracing buffer size.
2428 trace_event=[event-list]
2429 [FTRACE] Set and start specified trace events in order
2430 to facilitate early boot debugging.
2431 See also Documentation/trace/events.txt
2433 tsc= Disable clocksource-must-verify flag for TSC.
2434 Format: <string>
2435 [x86] reliable: mark tsc clocksource as reliable, this
2436 disables clocksource verification at runtime.
2437 Used to enable high-resolution timer mode on older
2438 hardware, and in virtualized environment.
2440 turbografx.map[2|3]= [HW,JOY]
2441 TurboGraFX parallel port interface
2442 Format:
2443 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2444 See also Documentation/input/joystick-parport.txt
2446 uhash_entries= [KNL,NET]
2447 Set number of hash buckets for UDP/UDP-Lite connections
2449 uhci-hcd.ignore_oc=
2450 [USB] Ignore overcurrent events (default N).
2451 Some badly-designed motherboards generate lots of
2452 bogus events, for ports that aren't wired to
2453 anything. Set this parameter to avoid log spamming.
2454 Note that genuine overcurrent events won't be
2455 reported either.
2457 unknown_nmi_panic
2458 [X86]
2459 Set unknown_nmi_panic=1 early on boot.
2461 usbcore.autosuspend=
2462 [USB] The autosuspend time delay (in seconds) used
2463 for newly-detected USB devices (default 2). This
2464 is the time required before an idle device will be
2465 autosuspended. Devices for which the delay is set
2466 to a negative value won't be autosuspended at all.
2468 usbcore.usbfs_snoop=
2469 [USB] Set to log all usbfs traffic (default 0 = off).
2471 usbcore.blinkenlights=
2472 [USB] Set to cycle leds on hubs (default 0 = off).
2474 usbcore.old_scheme_first=
2475 [USB] Start with the old device initialization
2476 scheme (default 0 = off).
2478 usbcore.use_both_schemes=
2479 [USB] Try the other device initialization scheme
2480 if the first one fails (default 1 = enabled).
2482 usbcore.initial_descriptor_timeout=
2483 [USB] Specifies timeout for the initial 64-byte
2484 USB_REQ_GET_DESCRIPTOR request in milliseconds
2485 (default 5000 = 5.0 seconds).
2487 usbhid.mousepoll=
2488 [USBHID] The interval which mice are to be polled at.
2490 usb-storage.delay_use=
2491 [UMS] The delay in seconds before a new device is
2492 scanned for Logical Units (default 5).
2494 usb-storage.quirks=
2495 [UMS] A list of quirks entries to supplement or
2496 override the built-in unusual_devs list. List
2497 entries are separated by commas. Each entry has
2498 the form VID:PID:Flags where VID and PID are Vendor
2499 and Product ID values (4-digit hex numbers) and
2500 Flags is a set of characters, each corresponding
2501 to a common usb-storage quirk flag as follows:
2502 a = SANE_SENSE (collect more than 18 bytes
2503 of sense data);
2504 b = BAD_SENSE (don't collect more than 18
2505 bytes of sense data);
2506 c = FIX_CAPACITY (decrease the reported
2507 device capacity by one sector);
2508 h = CAPACITY_HEURISTICS (decrease the
2509 reported device capacity by one
2510 sector if the number is odd);
2511 i = IGNORE_DEVICE (don't bind to this
2512 device);
2513 l = NOT_LOCKABLE (don't try to lock and
2514 unlock ejectable media);
2515 m = MAX_SECTORS_64 (don't transfer more
2516 than 64 sectors = 32 KB at a time);
2517 o = CAPACITY_OK (accept the capacity
2518 reported by the device);
2519 r = IGNORE_RESIDUE (the device reports
2520 bogus residue values);
2521 s = SINGLE_LUN (the device has only one
2522 Logical Unit);
2523 w = NO_WP_DETECT (don't test whether the
2524 medium is write-protected).
2525 Example: quirks=0419:aaf5:rl,0421:0433:rc
2527 userpte=
2528 [X86] Flags controlling user PTE allocations.
2530 nohigh = do not allocate PTE pages in
2531 HIGHMEM regardless of setting
2532 of CONFIG_HIGHPTE.
2534 vdso= [X86,SH]
2535 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2536 vdso=1: enable VDSO (default)
2537 vdso=0: disable VDSO mapping
2539 vdso32= [X86]
2540 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2541 vdso32=1: enable 32-bit VDSO (default)
2542 vdso32=0: disable 32-bit VDSO mapping
2544 vector= [IA-64,SMP]
2545 vector=percpu: enable percpu vector domain
2547 video= [FB] Frame buffer configuration
2548 See Documentation/fb/modedb.txt.
2550 vga= [BOOT,X86-32] Select a particular video mode
2551 See Documentation/x86/boot.txt and
2552 Documentation/svga.txt.
2553 Use vga=ask for menu.
2554 This is actually a boot loader parameter; the value is
2555 passed to the kernel using a special protocol.
2557 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2558 size of <nn>. This can be used to increase the
2559 minimum size (128MB on x86). It can also be used to
2560 decrease the size and leave more room for directly
2561 mapped kernel RAM.
2563 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2564 Format: <command>
2566 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2567 Format: <command>
2569 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2570 Format: <command>
2572 vt.cur_default= [VT] Default cursor shape.
2573 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2574 the parameters of the <Esc>[?A;B;Cc escape sequence;
2575 see VGA-softcursor.txt. Default: 2 = underline.
2577 vt.default_blu= [VT]
2578 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2579 Change the default blue palette of the console.
2580 This is a 16-member array composed of values
2581 ranging from 0-255.
2583 vt.default_grn= [VT]
2584 Format: <green0>,<green1>,<green2>,...,<green15>
2585 Change the default green palette of the console.
2586 This is a 16-member array composed of values
2587 ranging from 0-255.
2589 vt.default_red= [VT]
2590 Format: <red0>,<red1>,<red2>,...,<red15>
2591 Change the default red palette of the console.
2592 This is a 16-member array composed of values
2593 ranging from 0-255.
2595 vt.default_utf8=
2596 [VT]
2597 Format=<0|1>
2598 Set system-wide default UTF-8 mode for all tty's.
2599 Default is 1, i.e. UTF-8 mode is enabled for all
2600 newly opened terminals.
2602 vt.global_cursor_default=
2603 [VT]
2604 Format=<-1|0|1>
2605 Set system-wide default for whether a cursor
2606 is shown on new VTs. Default is -1,
2607 i.e. cursors will be created by default unless
2608 overridden by individual drivers. 0 will hide
2609 cursors, 1 will display them.
2611 watchdog timers [HW,WDT] For information on watchdog timers,
2612 see Documentation/watchdog/watchdog-parameters.txt
2613 or other driver-specific files in the
2614 Documentation/watchdog/ directory.
2616 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2617 default x2apic cluster mode on platforms
2618 supporting x2apic.
2620 x86_mrst_timer= [X86-32,APBT]
2621 Choose timer option for x86 Moorestown MID platform.
2622 Two valid options are apbt timer only and lapic timer
2623 plus one apbt timer for broadcast timer.
2624 x86_mrst_timer=apbt_only | lapic_and_apbt
2626 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2627 xd_geo= See header of drivers/block/xd.c.
2629 xen_emul_unplug= [HW,X86,XEN]
2630 Unplug Xen emulated devices
2631 Format: [unplug0,][unplug1]
2632 ide-disks -- unplug primary master IDE devices
2633 aux-ide-disks -- unplug non-primary-master IDE devices
2634 nics -- unplug network devices
2635 all -- unplug all emulated devices (NICs and IDE disks)
2636 unnecessary -- unplugging emulated devices is
2637 unnecessary even if the host did not respond to
2638 the unplug protocol
2639 never -- do not unplug even if version check succeeds
2641 xirc2ps_cs= [NET,PCMCIA]
2642 Format:
2643 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2645 ______________________________________________________________________
2647 TODO:
2649 Add more DRM drivers.