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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 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.reset [HW] Reset the controller during init and cleanup
883 i8042.unlock [HW] Unlock (ignore) the keylock
885 i810= [HW,DRM]
887 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
888 indicates that the driver is running on unsupported
889 hardware.
890 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
891 does not match list of supported models.
892 i8k.power_status
893 [HW] Report power status in /proc/i8k
894 (disabled by default)
895 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
896 capability is set.
898 icn= [HW,ISDN]
899 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
901 ide-core.nodma= [HW] (E)IDE subsystem
902 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
903 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
904 .cdrom .chs .ignore_cable are additional options
905 See Documentation/ide/ide.txt.
907 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
908 Claim all unknown PCI IDE storage controllers.
910 idle= [X86]
911 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
912 Poll forces a polling idle loop that can slightly
913 improve the performance of waking up a idle CPU, but
914 will use a lot of power and make the system run hot.
915 Not recommended.
916 idle=mwait: On systems which support MONITOR/MWAIT but
917 the kernel chose to not use it because it doesn't save
918 as much power as a normal idle loop, use the
919 MONITOR/MWAIT idle loop anyways. Performance should be
920 the same as idle=poll.
921 idle=halt: Halt is forced to be used for CPU idle.
922 In such case C2/C3 won't be used again.
923 idle=nomwait: Disable mwait for CPU C-states
925 ignore_loglevel [KNL]
926 Ignore loglevel setting - this will print /all/
927 kernel messages to the console. Useful for debugging.
929 ihash_entries= [KNL]
930 Set number of hash buckets for inode cache.
932 ima_audit= [IMA]
933 Format: { "0" | "1" }
934 0 -- integrity auditing messages. (Default)
935 1 -- enable informational integrity auditing messages.
937 ima_hash= [IMA]
938 Format: { "sha1" | "md5" }
939 default: "sha1"
941 ima_tcb [IMA]
942 Load a policy which meets the needs of the Trusted
943 Computing Base. This means IMA will measure all
944 programs exec'd, files mmap'd for exec, and all files
945 opened for read by uid=0.
947 init= [KNL]
948 Format: <full_path>
949 Run specified binary instead of /sbin/init as init
950 process.
952 initcall_debug [KNL] Trace initcalls as they are executed. Useful
953 for working out where the kernel is dying during
954 startup.
956 initrd= [BOOT] Specify the location of the initial ramdisk
958 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
959 Format: <irq>
961 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
962 on
963 Enable intel iommu driver.
964 off
965 Disable intel iommu driver.
966 igfx_off [Default Off]
967 By default, gfx is mapped as normal device. If a gfx
968 device has a dedicated DMAR unit, the DMAR unit is
969 bypassed by not enabling DMAR with this option. In
970 this case, gfx device will use physical address for
971 DMA.
972 forcedac [x86_64]
973 With this option iommu will not optimize to look
974 for io virtual address below 32 bit forcing dual
975 address cycle on pci bus for cards supporting greater
976 than 32 bit addressing. The default is to look
977 for translation below 32 bit and if not available
978 then look in the higher range.
979 strict [Default Off]
980 With this option on every unmap_single operation will
981 result in a hardware IOTLB flush operation as opposed
982 to batching them for performance.
984 intremap= [X86-64, Intel-IOMMU]
985 Format: { on (default) | off | nosid }
986 on enable Interrupt Remapping (default)
987 off disable Interrupt Remapping
988 nosid disable Source ID checking
990 inttest= [IA64]
992 iomem= Disable strict checking of access to MMIO memory
993 strict regions from userspace.
994 relaxed
996 iommu= [x86]
997 off
998 force
999 noforce
1000 biomerge
1001 panic
1002 nopanic
1003 merge
1004 nomerge
1005 forcesac
1006 soft
1007 pt [x86, IA64]
1009 io7= [HW] IO7 for Marvel based alpha systems
1010 See comment before marvel_specify_io7 in
1011 arch/alpha/kernel/core_marvel.c.
1013 io_delay= [X86] I/O delay method
1014 0x80
1015 Standard port 0x80 based delay
1016 0xed
1017 Alternate port 0xed based delay (needed on some systems)
1018 udelay
1019 Simple two microseconds delay
1020 none
1021 No delay
1023 ip= [IP_PNP]
1024 See Documentation/filesystems/nfs/nfsroot.txt.
1026 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1027 See comment before ip2_setup() in
1028 drivers/char/ip2/ip2base.c.
1030 irqfixup [HW]
1031 When an interrupt is not handled search all handlers
1032 for it. Intended to get systems with badly broken
1033 firmware running.
1035 irqpoll [HW]
1036 When an interrupt is not handled search all handlers
1037 for it. Also check all handlers each timer
1038 interrupt. Intended to get systems with badly broken
1039 firmware running.
1041 isapnp= [ISAPNP]
1042 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1044 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1045 Format:
1046 <cpu number>,...,<cpu number>
1047 or
1048 <cpu number>-<cpu number>
1049 (must be a positive range in ascending order)
1050 or a mixture
1051 <cpu number>,...,<cpu number>-<cpu number>
1053 This option can be used to specify one or more CPUs
1054 to isolate from the general SMP balancing and scheduling
1055 algorithms. You can move a process onto or off an
1056 "isolated" CPU via the CPU affinity syscalls or cpuset.
1057 <cpu number> begins at 0 and the maximum value is
1058 "number of CPUs in system - 1".
1060 This option is the preferred way to isolate CPUs. The
1061 alternative -- manually setting the CPU mask of all
1062 tasks in the system -- can cause problems and
1063 suboptimal load balancer performance.
1065 iucv= [HW,NET]
1067 js= [HW,JOY] Analog joystick
1068 See Documentation/input/joystick.txt.
1070 keepinitrd [HW,ARM]
1072 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1073 specifies the amount of memory usable by the kernel
1074 for non-movable allocations. The requested amount is
1075 spread evenly throughout all nodes in the system. The
1076 remaining memory in each node is used for Movable
1077 pages. In the event, a node is too small to have both
1078 kernelcore and Movable pages, kernelcore pages will
1079 take priority and other nodes will have a larger number
1080 of kernelcore pages. The Movable zone is used for the
1081 allocation of pages that may be reclaimed or moved
1082 by the page migration subsystem. This means that
1083 HugeTLB pages may not be allocated from this zone.
1084 Note that allocations like PTEs-from-HighMem still
1085 use the HighMem zone if it exists, and the Normal
1086 zone if it does not.
1088 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1089 Format: <Controller#>[,poll interval]
1090 The controller # is the number of the ehci usb debug
1091 port as it is probed via PCI. The poll interval is
1092 optional and is the number seconds in between
1093 each poll cycle to the debug port in case you need
1094 the functionality for interrupting the kernel with
1095 gdb or control-c on the dbgp connection. When
1096 not using this parameter you use sysrq-g to break into
1097 the kernel debugger.
1099 kgdboc= [KGDB,HW] kgdb over consoles.
1100 Requires a tty driver that supports console polling,
1101 or a supported polling keyboard driver (non-usb).
1102 Serial only format: <serial_device>[,baud]
1103 keyboard only format: kbd
1104 keyboard and serial format: kbd,<serial_device>[,baud]
1105 Optional Kernel mode setting:
1106 kms, kbd format: kms,kbd
1107 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1109 kgdbwait [KGDB] Stop kernel execution and enter the
1110 kernel debugger at the earliest opportunity.
1112 kmac= [MIPS] korina ethernet MAC address.
1113 Configure the RouterBoard 532 series on-chip
1114 Ethernet adapter MAC address.
1116 kmemleak= [KNL] Boot-time kmemleak enable/disable
1117 Valid arguments: on, off
1118 Default: on
1120 kstack=N [X86] Print N words from the kernel stack
1121 in oops dumps.
1123 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1124 Default is 0 (don't ignore, but inject #GP)
1126 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1127 Default is 1 (enabled)
1129 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1130 Default is 0 (off)
1132 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1133 for all guests.
1134 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1136 kvm-intel.bypass_guest_pf=
1137 [KVM,Intel] Disables bypassing of guest page faults
1138 on Intel chips. Default is 1 (enabled)
1140 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1141 (virtualized MMU) support on capable Intel chips.
1142 Default is 1 (enabled)
1144 kvm-intel.emulate_invalid_guest_state=
1145 [KVM,Intel] Enable emulation of invalid guest states
1146 Default is 0 (disabled)
1148 kvm-intel.flexpriority=
1149 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1150 Default is 1 (enabled)
1152 kvm-intel.unrestricted_guest=
1153 [KVM,Intel] Disable unrestricted guest feature
1154 (virtualized real and unpaged mode) on capable
1155 Intel chips. Default is 1 (enabled)
1157 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1158 feature (tagged TLBs) on capable Intel chips.
1159 Default is 1 (enabled)
1161 l2cr= [PPC]
1163 l3cr= [PPC]
1165 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1166 disabled it.
1168 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1169 in C2 power state.
1171 libata.dma= [LIBATA] DMA control
1172 libata.dma=0 Disable all PATA and SATA DMA
1173 libata.dma=1 PATA and SATA Disk DMA only
1174 libata.dma=2 ATAPI (CDROM) DMA only
1175 libata.dma=4 Compact Flash DMA only
1176 Combinations also work, so libata.dma=3 enables DMA
1177 for disks and CDROMs, but not CFs.
1179 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1180 libata.ignore_hpa=0 keep BIOS limits (default)
1181 libata.ignore_hpa=1 ignore limits, using full disk
1183 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1184 when set.
1185 Format: <int>
1187 libata.force= [LIBATA] Force configurations. The format is comma
1188 separated list of "[ID:]VAL" where ID is
1189 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1190 matching port, link or device. Basically, it matches
1191 the ATA ID string printed on console by libata. If
1192 the whole ID part is omitted, the last PORT and DEVICE
1193 values are used. If ID hasn't been specified yet, the
1194 configuration applies to all ports, links and devices.
1196 If only DEVICE is omitted, the parameter applies to
1197 the port and all links and devices behind it. DEVICE
1198 number of 0 either selects the first device or the
1199 first fan-out link behind PMP device. It does not
1200 select the host link. DEVICE number of 15 selects the
1201 host link and device attached to it.
1203 The VAL specifies the configuration to force. As long
1204 as there's no ambiguity shortcut notation is allowed.
1205 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1206 The following configurations can be forced.
1208 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1209 Any ID with matching PORT is used.
1211 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1213 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1214 udma[/][16,25,33,44,66,100,133] notation is also
1215 allowed.
1217 * [no]ncq: Turn on or off NCQ.
1219 * nohrst, nosrst, norst: suppress hard, soft
1220 and both resets.
1222 * dump_id: dump IDENTIFY data.
1224 If there are multiple matching configurations changing
1225 the same attribute, the last one is used.
1227 memblock=debug [KNL] Enable memblock debug messages.
1229 load_ramdisk= [RAM] List of ramdisks to load from floppy
1230 See Documentation/blockdev/ramdisk.txt.
1232 lockd.nlm_grace_period=P [NFS] Assign grace period.
1233 Format: <integer>
1235 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1236 Format: <integer>
1238 lockd.nlm_timeout=T [NFS] Assign timeout value.
1239 Format: <integer>
1241 lockd.nlm_udpport=M [NFS] Assign UDP port.
1242 Format: <integer>
1244 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1245 Format: <irq>
1247 loglevel= All Kernel Messages with a loglevel smaller than the
1248 console loglevel will be printed to the console. It can
1249 also be changed with klogd or other programs. The
1250 loglevels are defined as follows:
1252 0 (KERN_EMERG) system is unusable
1253 1 (KERN_ALERT) action must be taken immediately
1254 2 (KERN_CRIT) critical conditions
1255 3 (KERN_ERR) error conditions
1256 4 (KERN_WARNING) warning conditions
1257 5 (KERN_NOTICE) normal but significant condition
1258 6 (KERN_INFO) informational
1259 7 (KERN_DEBUG) debug-level messages
1261 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1262 Format: { n | nk | nM }
1263 n must be a power of two. The default size
1264 is set in the kernel config file.
1266 logo.nologo [FB] Disables display of the built-in Linux logo.
1267 This may be used to provide more screen space for
1268 kernel log messages and is useful when debugging
1269 kernel boot problems.
1271 lp=0 [LP] Specify parallel ports to use, e.g,
1272 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1273 lp=reset first parallel port). 'lp=0' disables the
1274 lp=auto printer driver. 'lp=reset' (which can be
1275 specified in addition to the ports) causes
1276 attached printers to be reset. Using
1277 lp=port1,port2,... specifies the parallel ports
1278 to associate lp devices with, starting with
1279 lp0. A port specification may be 'none' to skip
1280 that lp device, or a parport name such as
1281 'parport0'. Specifying 'lp=auto' instead of a
1282 port specification list means that device IDs
1283 from each port should be examined, to see if
1284 an IEEE 1284-compliant printer is attached; if
1285 so, the driver will manage that printer.
1286 See also header of drivers/char/lp.c.
1288 lpj=n [KNL]
1289 Sets loops_per_jiffy to given constant, thus avoiding
1290 time-consuming boot-time autodetection (up to 250 ms per
1291 CPU). 0 enables autodetection (default). To determine
1292 the correct value for your kernel, boot with normal
1293 autodetection and see what value is printed. Note that
1294 on SMP systems the preset will be applied to all CPUs,
1295 which is likely to cause problems if your CPUs need
1296 significantly divergent settings. An incorrect value
1297 will cause delays in the kernel to be wrong, leading to
1298 unpredictable I/O errors and other breakage. Although
1299 unlikely, in the extreme case this might damage your
1300 hardware.
1302 ltpc= [NET]
1303 Format: <io>,<irq>,<dma>
1305 machvec= [IA64] Force the use of a particular machine-vector
1306 (machvec) in a generic kernel.
1307 Example: machvec=hpzx1_swiotlb
1309 machtype= [Loongson] Share the same kernel image file between different
1310 yeeloong laptop.
1311 Example: machtype=lemote-yeeloong-2f-7inch
1313 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1314 than or equal to this physical address is ignored.
1316 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1317 should make use of. maxcpus=n : n >= 0 limits the
1318 kernel to using 'n' processors. n=0 is a special case,
1319 it is equivalent to "nosmp", which also disables
1320 the IO APIC.
1322 max_loop= [LOOP] Maximum number of loopback devices that can
1323 be mounted
1324 Format: <1-256>
1326 mcatest= [IA-64]
1328 mce [X86-32] Machine Check Exception
1330 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1332 md= [HW] RAID subsystems devices and level
1333 See Documentation/md.txt.
1335 mdacon= [MDA]
1336 Format: <first>,<last>
1337 Specifies range of consoles to be captured by the MDA.
1339 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1340 Amount of memory to be used when the kernel is not able
1341 to see the whole system memory or for test.
1342 [X86-32] Use together with memmap= to avoid physical
1343 address space collisions. Without memmap= PCI devices
1344 could be placed at addresses belonging to unused RAM.
1346 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1347 memory.
1349 memchunk=nn[KMG]
1350 [KNL,SH] Allow user to override the default size for
1351 per-device physically contiguous DMA buffers.
1353 memmap=exactmap [KNL,X86] Enable setting of an exact
1354 E820 memory map, as specified by the user.
1355 Such memmap=exactmap lines can be constructed based on
1356 BIOS output or other requirements. See the memmap=nn@ss
1357 option description.
1359 memmap=nn[KMG]@ss[KMG]
1360 [KNL] Force usage of a specific region of memory
1361 Region of memory to be used, from ss to ss+nn.
1363 memmap=nn[KMG]#ss[KMG]
1364 [KNL,ACPI] Mark specific memory as ACPI data.
1365 Region of memory to be used, from ss to ss+nn.
1367 memmap=nn[KMG]$ss[KMG]
1368 [KNL,ACPI] Mark specific memory as reserved.
1369 Region of memory to be used, from ss to ss+nn.
1370 Example: Exclude memory from 0x18690000-0x1869ffff
1371 memmap=64K$0x18690000
1372 or
1373 memmap=0x10000$0x18690000
1375 memory_corruption_check=0/1 [X86]
1376 Some BIOSes seem to corrupt the first 64k of
1377 memory when doing things like suspend/resume.
1378 Setting this option will scan the memory
1379 looking for corruption. Enabling this will
1380 both detect corruption and prevent the kernel
1381 from using the memory being corrupted.
1382 However, its intended as a diagnostic tool; if
1383 repeatable BIOS-originated corruption always
1384 affects the same memory, you can use memmap=
1385 to prevent the kernel from using that memory.
1387 memory_corruption_check_size=size [X86]
1388 By default it checks for corruption in the low
1389 64k, making this memory unavailable for normal
1390 use. Use this parameter to scan for
1391 corruption in more or less memory.
1393 memory_corruption_check_period=seconds [X86]
1394 By default it checks for corruption every 60
1395 seconds. Use this parameter to check at some
1396 other rate. 0 disables periodic checking.
1398 memtest= [KNL,X86] Enable memtest
1399 Format: <integer>
1400 default : 0 <disable>
1401 Specifies the number of memtest passes to be
1402 performed. Each pass selects another test
1403 pattern from a given set of patterns. Memtest
1404 fills the memory with this pattern, validates
1405 memory contents and reserves bad memory
1406 regions that are detected.
1408 meye.*= [HW] Set MotionEye Camera parameters
1409 See Documentation/video4linux/meye.txt.
1411 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1412 Multi-Function General Purpose Timers on AMD Geode
1413 platforms.
1415 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1416 the BIOS has incorrectly applied a workaround. TinyBIOS
1417 version 0.98 is known to be affected, 0.99 fixes the
1418 problem by letting the user disable the workaround.
1420 mga= [HW,DRM]
1422 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1423 physical address is ignored.
1425 mini2440= [ARM,HW,KNL]
1426 Format:[0..2][b][c][t]
1427 Default: "0tb"
1428 MINI2440 configuration specification:
1429 0 - The attached screen is the 3.5" TFT
1430 1 - The attached screen is the 7" TFT
1431 2 - The VGA Shield is attached (1024x768)
1432 Leaving out the screen size parameter will not load
1433 the TFT driver, and the framebuffer will be left
1434 unconfigured.
1435 b - Enable backlight. The TFT backlight pin will be
1436 linked to the kernel VESA blanking code and a GPIO
1437 LED. This parameter is not necessary when using the
1438 VGA shield.
1439 c - Enable the s3c camera interface.
1440 t - Reserved for enabling touchscreen support. The
1441 touchscreen support is not enabled in the mainstream
1442 kernel as of 2.6.30, a preliminary port can be found
1443 in the "bleeding edge" mini2440 support kernel at
1444 http://repo.or.cz/w/linux-2.6/mini2440.git
1446 mminit_loglevel=
1447 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1448 parameter allows control of the logging verbosity for
1449 the additional memory initialisation checks. A value
1450 of 0 disables mminit logging and a level of 4 will
1451 log everything. Information is printed at KERN_DEBUG
1452 so loglevel=8 may also need to be specified.
1454 mousedev.tap_time=
1455 [MOUSE] Maximum time between finger touching and
1456 leaving touchpad surface for touch to be considered
1457 a tap and be reported as a left button click (for
1458 touchpads working in absolute mode only).
1459 Format: <msecs>
1460 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1461 reporting absolute coordinates, such as tablets
1462 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1463 reporting absolute coordinates, such as tablets
1465 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1466 is similar to kernelcore except it specifies the
1467 amount of memory used for migratable allocations.
1468 If both kernelcore and movablecore is specified,
1469 then kernelcore will be at *least* the specified
1470 value but may be more. If movablecore on its own
1471 is specified, the administrator must be careful
1472 that the amount of memory usable for all allocations
1473 is not too small.
1475 MTD_Partition= [MTD]
1476 Format: <name>,<region-number>,<size>,<offset>
1478 MTD_Region= [MTD] Format:
1479 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1481 mtdparts= [MTD]
1482 See drivers/mtd/cmdlinepart.c.
1484 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1486 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1488 boundary - index of last SLC block on Flex-OneNAND.
1489 The remaining blocks are configured as MLC blocks.
1490 lock - Configure if Flex-OneNAND boundary should be locked.
1491 Once locked, the boundary cannot be changed.
1492 1 indicates lock status, 0 indicates unlock status.
1494 mtdset= [ARM]
1495 ARM/S3C2412 JIVE boot control
1497 See arch/arm/mach-s3c2412/mach-jive.c
1499 mtouchusb.raw_coordinates=
1500 [HW] Make the MicroTouch USB driver use raw coordinates
1501 ('y', default) or cooked coordinates ('n')
1503 mtrr_chunk_size=nn[KMG] [X86]
1504 used for mtrr cleanup. It is largest continuous chunk
1505 that could hold holes aka. UC entries.
1507 mtrr_gran_size=nn[KMG] [X86]
1508 Used for mtrr cleanup. It is granularity of mtrr block.
1509 Default is 1.
1510 Large value could prevent small alignment from
1511 using up MTRRs.
1513 mtrr_spare_reg_nr=n [X86]
1514 Format: <integer>
1515 Range: 0,7 : spare reg number
1516 Default : 1
1517 Used for mtrr cleanup. It is spare mtrr entries number.
1518 Set to 2 or more if your graphical card needs more.
1520 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1522 netdev= [NET] Network devices parameters
1523 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1524 Note that mem_start is often overloaded to mean
1525 something different and driver-specific.
1526 This usage is only documented in each driver source
1527 file if at all.
1529 nf_conntrack.acct=
1530 [NETFILTER] Enable connection tracking flow accounting
1531 0 to disable accounting
1532 1 to enable accounting
1533 Default value is 0.
1535 nfsaddrs= [NFS]
1536 See Documentation/filesystems/nfs/nfsroot.txt.
1538 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1539 See Documentation/filesystems/nfs/nfsroot.txt.
1541 nfs.callback_tcpport=
1542 [NFS] set the TCP port on which the NFSv4 callback
1543 channel should listen.
1545 nfs.cache_getent=
1546 [NFS] sets the pathname to the program which is used
1547 to update the NFS client cache entries.
1549 nfs.cache_getent_timeout=
1550 [NFS] sets the timeout after which an attempt to
1551 update a cache entry is deemed to have failed.
1553 nfs.idmap_cache_timeout=
1554 [NFS] set the maximum lifetime for idmapper cache
1555 entries.
1557 nfs.enable_ino64=
1558 [NFS] enable 64-bit inode numbers.
1559 If zero, the NFS client will fake up a 32-bit inode
1560 number for the readdir() and stat() syscalls instead
1561 of returning the full 64-bit number.
1562 The default is to return 64-bit inode numbers.
1564 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1565 when a NMI is triggered.
1566 Format: [state][,regs][,debounce][,die]
1568 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1569 Format: [panic,][num]
1570 Valid num: 0,1,2
1571 0 - turn nmi_watchdog off
1572 1 - use the IO-APIC timer for the NMI watchdog
1573 2 - use the local APIC for the NMI watchdog using
1574 a performance counter. Note: This will use one
1575 performance counter and the local APIC's performance
1576 vector.
1577 When panic is specified, panic when an NMI watchdog
1578 timeout occurs.
1579 This is useful when you use a panic=... timeout and
1580 need the box quickly up again.
1581 Instead of 1 and 2 it is possible to use the following
1582 symbolic names: lapic and ioapic
1583 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1585 netpoll.carrier_timeout=
1586 [NET] Specifies amount of time (in seconds) that
1587 netpoll should wait for a carrier. By default netpoll
1588 waits 4 seconds.
1590 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1591 emulation library even if a 387 maths coprocessor
1592 is present.
1594 no_console_suspend
1595 [HW] Never suspend the console
1596 Disable suspending of consoles during suspend and
1597 hibernate operations. Once disabled, debugging
1598 messages can reach various consoles while the rest
1599 of the system is being put to sleep (ie, while
1600 debugging driver suspend/resume hooks). This may
1601 not work reliably with all consoles, but is known
1602 to work with serial and VGA consoles.
1604 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1605 caches in the slab allocator. Saves per-node memory,
1606 but will impact performance.
1608 noalign [KNL,ARM]
1610 noapic [SMP,APIC] Tells the kernel to not make use of any
1611 IOAPICs that may be present in the system.
1613 nobats [PPC] Do not use BATs for mapping kernel lowmem
1614 on "Classic" PPC cores.
1616 nocache [ARM]
1618 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1620 nodelayacct [KNL] Disable per-task delay accounting
1622 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1624 nodsp [SH] Disable hardware DSP at boot time.
1626 noefi [X86] Disable EFI runtime services support.
1628 noexec [IA-64]
1630 noexec [X86]
1631 On X86-32 available only on PAE configured kernels.
1632 noexec=on: enable non-executable mappings (default)
1633 noexec=off: disable non-executable mappings
1635 noexec32 [X86-64]
1636 This affects only 32-bit executables.
1637 noexec32=on: enable non-executable mappings (default)
1638 read doesn't imply executable mappings
1639 noexec32=off: disable non-executable mappings
1640 read implies executable mappings
1642 nofpu [SH] Disable hardware FPU at boot time.
1644 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1645 register save and restore. The kernel will only save
1646 legacy floating-point registers on task switch.
1648 noxsave [BUGS=X86] Disables x86 extended register state save
1649 and restore using xsave. The kernel will fallback to
1650 enabling legacy floating-point and sse state.
1652 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1653 wfi(ARM) instruction doesn't work correctly and not to
1654 use it. This is also useful when using JTAG debugger.
1656 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1657 instruction doesn't work correctly and not to
1658 use it.
1660 no_file_caps Tells the kernel not to honor file capabilities. The
1661 only way then for a file to be executed with privilege
1662 is to be setuid root or executed by root.
1664 nohalt [IA-64] Tells the kernel not to use the power saving
1665 function PAL_HALT_LIGHT when idle. This increases
1666 power-consumption. On the positive side, it reduces
1667 interrupt wake-up latency, which may improve performance
1668 in certain environments such as networked servers or
1669 real-time systems.
1671 nohz= [KNL] Boottime enable/disable dynamic ticks
1672 Valid arguments: on, off
1673 Default: on
1675 noiotrap [SH] Disables trapped I/O port accesses.
1677 noirqdebug [X86-32] Disables the code which attempts to detect and
1678 disable unhandled interrupt sources.
1680 no_timer_check [X86,APIC] Disables the code which tests for
1681 broken timer IRQ sources.
1683 noisapnp [ISAPNP] Disables ISA PnP code.
1685 noinitrd [RAM] Tells the kernel not to load any configured
1686 initial RAM disk.
1688 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1689 remapping.
1690 [Deprecated - use intremap=off]
1692 nointroute [IA-64]
1694 nojitter [IA64] Disables jitter checking for ITC timers.
1696 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1698 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1700 noltlbs [PPC] Do not use large page/tlb entries for kernel
1701 lowmem mapping on PPC40x.
1703 nomca [IA-64] Disable machine check abort handling
1705 nomce [X86-32] Machine Check Exception
1707 nomfgpt [X86-32] Disable Multi-Function General Purpose
1708 Timer usage (for AMD Geode machines).
1710 nopat [X86] Disable PAT (page attribute table extension of
1711 pagetables) support.
1713 norandmaps Don't use address space randomization. Equivalent to
1714 echo 0 > /proc/sys/kernel/randomize_va_space
1716 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1718 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1719 with UP alternatives
1721 noresidual [PPC] Don't use residual data on PReP machines.
1723 noresume [SWSUSP] Disables resume and restores original swap
1724 space.
1726 no-scroll [VGA] Disables scrollback.
1727 This is required for the Braillex ib80-piezo Braille
1728 reader made by F.H. Papenmeier (Germany).
1730 nosbagart [IA-64]
1732 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1734 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1735 and disable the IO APIC. legacy for "maxcpus=0".
1737 nosoftlockup [KNL] Disable the soft-lockup detector.
1739 noswapaccount [KNL] Disable accounting of swap in memory resource
1740 controller. (See Documentation/cgroups/memory.txt)
1742 nosync [HW,M68K] Disables sync negotiation for all devices.
1744 notsc [BUGS=X86-32] Disable Time Stamp Counter
1746 nousb [USB] Disable the USB subsystem
1748 nowatchdog [KNL] Disable the lockup detector.
1750 nowb [ARM]
1752 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1754 nptcg= [IA64] Override max number of concurrent global TLB
1755 purges which is reported from either PAL_VM_SUMMARY or
1756 SAL PALO.
1758 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1759 could support. nr_cpus=n : n >= 1 limits the kernel to
1760 supporting 'n' processors. Later in runtime you can not
1761 use hotplug cpu feature to put more cpu back to online.
1762 just like you compile the kernel NR_CPUS=n
1764 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1766 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1767 one of ['zone', 'node', 'default'] can be specified
1768 This can be set from sysctl after boot.
1769 See Documentation/sysctl/vm.txt for details.
1771 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1772 See Documentation/debugging-via-ohci1394.txt for more
1773 info.
1775 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1776 Rather than timing out after 20 ms if an EC
1777 command is not properly ACKed, override the length
1778 of the timeout. We have interrupts disabled while
1779 waiting for the ACK, so if this is set too high
1780 interrupts *may* be lost!
1782 omap_mux= [OMAP] Override bootloader pin multiplexing.
1783 Format: <mux_mode0.mode_name=value>...
1784 For example, to override I2C bus2:
1785 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1787 oprofile.timer= [HW]
1788 Use timer interrupt instead of performance counters
1790 oprofile.cpu_type= Force an oprofile cpu type
1791 This might be useful if you have an older oprofile
1792 userland or if you want common events.
1793 Format: { arch_perfmon }
1794 arch_perfmon: [X86] Force use of architectural
1795 perfmon on Intel CPUs instead of the
1796 CPU specific event set.
1798 OSS [HW,OSS]
1799 See Documentation/sound/oss/oss-parameters.txt
1801 panic= [KNL] Kernel behaviour on panic
1802 Format: <timeout>
1804 parkbd.port= [HW] Parallel port number the keyboard adapter is
1805 connected to, default is 0.
1806 Format: <parport#>
1807 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1808 0 for XT, 1 for AT (default is AT).
1809 Format: <mode>
1811 parport= [HW,PPT] Specify parallel ports. 0 disables.
1812 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1813 Use 'auto' to force the driver to use any
1814 IRQ/DMA settings detected (the default is to
1815 ignore detected IRQ/DMA settings because of
1816 possible conflicts). You can specify the base
1817 address, IRQ, and DMA settings; IRQ and DMA
1818 should be numbers, or 'auto' (for using detected
1819 settings on that particular port), or 'nofifo'
1820 (to avoid using a FIFO even if it is detected).
1821 Parallel ports are assigned in the order they
1822 are specified on the command line, starting
1823 with parport0.
1825 parport_init_mode= [HW,PPT]
1826 Configure VIA parallel port to operate in
1827 a specific mode. This is necessary on Pegasos
1828 computer where firmware has no options for setting
1829 up parallel port mode and sets it to spp.
1830 Currently this function knows 686a and 8231 chips.
1831 Format: [spp|ps2|epp|ecp|ecpepp]
1833 pause_on_oops=
1834 Halt all CPUs after the first oops has been printed for
1835 the specified number of seconds. This is to be used if
1836 your oopses keep scrolling off the screen.
1838 pcbit= [HW,ISDN]
1840 pcd. [PARIDE]
1841 See header of drivers/block/paride/pcd.c.
1842 See also Documentation/blockdev/paride.txt.
1844 pci=option[,option...] [PCI] various PCI subsystem options:
1845 earlydump [X86] dump PCI config space before the kernel
1846 changes anything
1847 off [X86] don't probe for the PCI bus
1848 bios [X86-32] force use of PCI BIOS, don't access
1849 the hardware directly. Use this if your machine
1850 has a non-standard PCI host bridge.
1851 nobios [X86-32] disallow use of PCI BIOS, only direct
1852 hardware access methods are allowed. Use this
1853 if you experience crashes upon bootup and you
1854 suspect they are caused by the BIOS.
1855 conf1 [X86] Force use of PCI Configuration
1856 Mechanism 1.
1857 conf2 [X86] Force use of PCI Configuration
1858 Mechanism 2.
1859 noaer [PCIE] If the PCIEAER kernel config parameter is
1860 enabled, this kernel boot option can be used to
1861 disable the use of PCIE advanced error reporting.
1862 nodomains [PCI] Disable support for multiple PCI
1863 root domains (aka PCI segments, in ACPI-speak).
1864 nommconf [X86] Disable use of MMCONFIG for PCI
1865 Configuration
1866 check_enable_amd_mmconf [X86] check for and enable
1867 properly configured MMIO access to PCI
1868 config space on AMD family 10h CPU
1869 nomsi [MSI] If the PCI_MSI kernel config parameter is
1870 enabled, this kernel boot option can be used to
1871 disable the use of MSI interrupts system-wide.
1872 noioapicquirk [APIC] Disable all boot interrupt quirks.
1873 Safety option to keep boot IRQs enabled. This
1874 should never be necessary.
1875 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1876 primary IO-APIC for bridges that cannot disable
1877 boot IRQs. This fixes a source of spurious IRQs
1878 when the system masks IRQs.
1879 noioapicreroute [APIC] Disable workaround that uses the
1880 boot IRQ equivalent of an IRQ that connects to
1881 a chipset where boot IRQs cannot be disabled.
1882 The opposite of ioapicreroute.
1883 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1884 routing table. These calls are known to be buggy
1885 on several machines and they hang the machine
1886 when used, but on other computers it's the only
1887 way to get the interrupt routing table. Try
1888 this option if the kernel is unable to allocate
1889 IRQs or discover secondary PCI buses on your
1890 motherboard.
1891 rom [X86] Assign address space to expansion ROMs.
1892 Use with caution as certain devices share
1893 address decoders between ROMs and other
1894 resources.
1895 norom [X86] Do not assign address space to
1896 expansion ROMs that do not already have
1897 BIOS assigned address ranges.
1898 nobar [X86] Do not assign address space to the
1899 BARs that weren't assigned by the BIOS.
1900 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1901 assigned automatically to PCI devices. You can
1902 make the kernel exclude IRQs of your ISA cards
1903 this way.
1904 pirqaddr=0xAAAAA [X86] Specify the physical address
1905 of the PIRQ table (normally generated
1906 by the BIOS) if it is outside the
1907 F0000h-100000h range.
1908 lastbus=N [X86] Scan all buses thru bus #N. Can be
1909 useful if the kernel is unable to find your
1910 secondary buses and you want to tell it
1911 explicitly which ones they are.
1912 assign-busses [X86] Always assign all PCI bus
1913 numbers ourselves, overriding
1914 whatever the firmware may have done.
1915 usepirqmask [X86] Honor the possible IRQ mask stored
1916 in the BIOS $PIR table. This is needed on
1917 some systems with broken BIOSes, notably
1918 some HP Pavilion N5400 and Omnibook XE3
1919 notebooks. This will have no effect if ACPI
1920 IRQ routing is enabled.
1921 noacpi [X86] Do not use ACPI for IRQ routing
1922 or for PCI scanning.
1923 use_crs [X86] Use PCI host bridge window information
1924 from ACPI. On BIOSes from 2008 or later, this
1925 is enabled by default. If you need to use this,
1926 please report a bug.
1927 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1928 If you need to use this, please report a bug.
1929 routeirq Do IRQ routing for all PCI devices.
1930 This is normally done in pci_enable_device(),
1931 so this option is a temporary workaround
1932 for broken drivers that don't call it.
1933 skip_isa_align [X86] do not align io start addr, so can
1934 handle more pci cards
1935 firmware [ARM] Do not re-enumerate the bus but instead
1936 just use the configuration from the
1937 bootloader. This is currently used on
1938 IXP2000 systems where the bus has to be
1939 configured a certain way for adjunct CPUs.
1940 noearly [X86] Don't do any early type 1 scanning.
1941 This might help on some broken boards which
1942 machine check when some devices' config space
1943 is read. But various workarounds are disabled
1944 and some IOMMU drivers will not work.
1945 bfsort Sort PCI devices into breadth-first order.
1946 This sorting is done to get a device
1947 order compatible with older (<= 2.4) kernels.
1948 nobfsort Don't sort PCI devices into breadth-first order.
1949 cbiosize=nn[KMG] The fixed amount of bus space which is
1950 reserved for the CardBus bridge's IO window.
1951 The default value is 256 bytes.
1952 cbmemsize=nn[KMG] The fixed amount of bus space which is
1953 reserved for the CardBus bridge's memory
1954 window. The default value is 64 megabytes.
1955 resource_alignment=
1956 Format:
1957 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1958 Specifies alignment and device to reassign
1959 aligned memory resources.
1960 If <order of align> is not specified,
1961 PAGE_SIZE is used as alignment.
1962 PCI-PCI bridge can be specified, if resource
1963 windows need to be expanded.
1964 ecrc= Enable/disable PCIe ECRC (transaction layer
1965 end-to-end CRC checking).
1966 bios: Use BIOS/firmware settings. This is the
1967 the default.
1968 off: Turn ECRC off
1969 on: Turn ECRC on.
1971 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1972 Management.
1973 off Disable ASPM.
1974 force Enable ASPM even on devices that claim not to support it.
1975 WARNING: Forcing ASPM on may cause system lockups.
1977 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
1978 Format: {auto|force}[,nomsi]
1979 auto Use native PCIe PME signaling if the BIOS allows the
1980 kernel to control PCIe config registers of root ports.
1981 force Use native PCIe PME signaling even if the BIOS refuses
1982 to allow the kernel to control the relevant PCIe config
1983 registers.
1984 nomsi Do not use MSI for native PCIe PME signaling (this makes
1985 all PCIe root ports use INTx for everything).
1987 pcmv= [HW,PCMCIA] BadgePAD 4
1989 pd. [PARIDE]
1990 See Documentation/blockdev/paride.txt.
1992 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1993 boot time.
1994 Format: { 0 | 1 }
1995 See arch/parisc/kernel/pdc_chassis.c
1997 percpu_alloc= Select which percpu first chunk allocator to use.
1998 Currently supported values are "embed" and "page".
1999 Archs may support subset or none of the selections.
2000 See comments in mm/percpu.c for details on each
2001 allocator. This parameter is primarily for debugging
2002 and performance comparison.
2004 pf. [PARIDE]
2005 See Documentation/blockdev/paride.txt.
2007 pg. [PARIDE]
2008 See Documentation/blockdev/paride.txt.
2010 pirq= [SMP,APIC] Manual mp-table setup
2011 See Documentation/x86/i386/IO-APIC.txt.
2013 plip= [PPT,NET] Parallel port network link
2014 Format: { parport<nr> | timid | 0 }
2015 See also Documentation/parport.txt.
2017 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2018 Override pmtimer IOPort with a hex value.
2019 e.g. pmtmr=0x508
2021 pnp.debug [PNP]
2022 Enable PNP debug messages. This depends on the
2023 CONFIG_PNP_DEBUG_MESSAGES option.
2025 pnpacpi= [ACPI]
2026 { off }
2028 pnpbios= [ISAPNP]
2029 { on | off | curr | res | no-curr | no-res }
2031 pnp_reserve_irq=
2032 [ISAPNP] Exclude IRQs for the autoconfiguration
2034 pnp_reserve_dma=
2035 [ISAPNP] Exclude DMAs for the autoconfiguration
2037 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2038 Ranges are in pairs (I/O port base and size).
2040 pnp_reserve_mem=
2041 [ISAPNP] Exclude memory regions for the
2042 autoconfiguration.
2043 Ranges are in pairs (memory base and size).
2045 ports= [IP_VS_FTP] IPVS ftp helper module
2046 Default is 21.
2047 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2048 may be specified.
2049 Format: <port>,<port>....
2051 print-fatal-signals=
2052 [KNL] debug: print fatal signals
2054 If enabled, warn about various signal handling
2055 related application anomalies: too many signals,
2056 too many POSIX.1 timers, fatal signals causing a
2057 coredump - etc.
2059 If you hit the warning due to signal overflow,
2060 you might want to try "ulimit -i unlimited".
2062 default: off.
2064 printk.time= Show timing data prefixed to each printk message line
2065 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2067 processor.max_cstate= [HW,ACPI]
2068 Limit processor to maximum C-state
2069 max_cstate=9 overrides any DMI blacklist limit.
2071 processor.nocst [HW,ACPI]
2072 Ignore the _CST method to determine C-states,
2073 instead using the legacy FADT method
2075 profile= [KNL] Enable kernel profiling via /proc/profile
2076 Format: [schedule,]<number>
2077 Param: "schedule" - profile schedule points.
2078 Param: <number> - step/bucket size as a power of 2 for
2079 statistical time based profiling.
2080 Param: "sleep" - profile D-state sleeping (millisecs).
2081 Requires CONFIG_SCHEDSTATS
2082 Param: "kvm" - profile VM exits.
2084 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2085 before loading.
2086 See Documentation/blockdev/ramdisk.txt.
2088 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2089 probe for; one of (bare|imps|exps|lifebook|any).
2090 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2091 per second.
2092 psmouse.resetafter= [HW,MOUSE]
2093 Try to reset the device after so many bad packets
2094 (0 = never).
2095 psmouse.resolution=
2096 [HW,MOUSE] Set desired mouse resolution, in dpi.
2097 psmouse.smartscroll=
2098 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2099 0 = disabled, 1 = enabled (default).
2101 pt. [PARIDE]
2102 See Documentation/blockdev/paride.txt.
2104 pty.legacy_count=
2105 [KNL] Number of legacy pty's. Overwrites compiled-in
2106 default number.
2108 quiet [KNL] Disable most log messages
2110 r128= [HW,DRM]
2112 raid= [HW,RAID]
2113 See Documentation/md.txt.
2115 ramdisk_blocksize= [RAM]
2116 See Documentation/blockdev/ramdisk.txt.
2118 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2119 See Documentation/blockdev/ramdisk.txt.
2121 rcupdate.blimit= [KNL,BOOT]
2122 Set maximum number of finished RCU callbacks to process
2123 in one batch.
2125 rcupdate.qhimark= [KNL,BOOT]
2126 Set threshold of queued
2127 RCU callbacks over which batch limiting is disabled.
2129 rcupdate.qlowmark= [KNL,BOOT]
2130 Set threshold of queued RCU callbacks below which
2131 batch limiting is re-enabled.
2133 rdinit= [KNL]
2134 Format: <full_path>
2135 Run specified binary instead of /init from the ramdisk,
2136 used for early userspace startup. See initrd.
2138 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2139 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2140 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2142 relax_domain_level=
2143 [KNL, SMP] Set scheduler's default relax_domain_level.
2144 See Documentation/cgroups/cpusets.txt.
2146 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2148 reservetop= [X86-32]
2149 Format: nn[KMG]
2150 Reserves a hole at the top of the kernel virtual
2151 address space.
2153 reset_devices [KNL] Force drivers to reset the underlying device
2154 during initialization.
2156 resume= [SWSUSP]
2157 Specify the partition device for software suspend
2159 resume_offset= [SWSUSP]
2160 Specify the offset from the beginning of the partition
2161 given by "resume=" at which the swap header is located,
2162 in <PAGE_SIZE> units (needed only for swap files).
2163 See Documentation/power/swsusp-and-swap-files.txt
2165 retain_initrd [RAM] Keep initrd memory after extraction
2167 rhash_entries= [KNL,NET]
2168 Set number of hash buckets for route cache
2170 riscom8= [HW,SERIAL]
2171 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2173 ro [KNL] Mount root device read-only on boot
2175 root= [KNL] Root filesystem
2177 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2178 mount the root filesystem
2180 rootflags= [KNL] Set root filesystem mount option string
2182 rootfstype= [KNL] Set root filesystem type
2184 rootwait [KNL] Wait (indefinitely) for root device to show up.
2185 Useful for devices that are detected asynchronously
2186 (e.g. USB and MMC devices).
2188 rw [KNL] Mount root device read-write on boot
2190 S [KNL] Run init in single mode
2192 sa1100ir [NET]
2193 See drivers/net/irda/sa1100_ir.c.
2195 sbni= [NET] Granch SBNI12 leased line adapter
2197 sched_debug [KNL] Enables verbose scheduler debug messages.
2199 security= [SECURITY] Choose a security module to enable at boot.
2200 If this boot parameter is not specified, only the first
2201 security module asking for security registration will be
2202 loaded. An invalid security module name will be treated
2203 as if no module has been chosen.
2205 selinux= [SELINUX] Disable or enable SELinux at boot time.
2206 Format: { "0" | "1" }
2207 See security/selinux/Kconfig help text.
2208 0 -- disable.
2209 1 -- enable.
2210 Default value is set via kernel config option.
2211 If enabled at boot time, /selinux/disable can be used
2212 later to disable prior to initial policy load.
2214 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2215 Format: { "0" | "1" }
2216 See security/apparmor/Kconfig help text
2217 0 -- disable.
2218 1 -- enable.
2219 Default value is set via kernel config option.
2221 serialnumber [BUGS=X86-32]
2223 shapers= [NET]
2224 Maximal number of shapers.
2226 show_msr= [x86] show boot-time MSR settings
2227 Format: { <integer> }
2228 Show boot-time (BIOS-initialized) MSR settings.
2229 The parameter means the number of CPUs to show,
2230 for example 1 means boot CPU only.
2232 simeth= [IA-64]
2233 simscsi=
2235 slram= [HW,MTD]
2237 slub_debug[=options[,slabs]] [MM, SLUB]
2238 Enabling slub_debug allows one to determine the
2239 culprit if slab objects become corrupted. Enabling
2240 slub_debug can create guard zones around objects and
2241 may poison objects when not in use. Also tracks the
2242 last alloc / free. For more information see
2243 Documentation/vm/slub.txt.
2245 slub_max_order= [MM, SLUB]
2246 Determines the maximum allowed order for slabs.
2247 A high setting may cause OOMs due to memory
2248 fragmentation. For more information see
2249 Documentation/vm/slub.txt.
2251 slub_min_objects= [MM, SLUB]
2252 The minimum number of objects per slab. SLUB will
2253 increase the slab order up to slub_max_order to
2254 generate a sufficiently large slab able to contain
2255 the number of objects indicated. The higher the number
2256 of objects the smaller the overhead of tracking slabs
2257 and the less frequently locks need to be acquired.
2258 For more information see Documentation/vm/slub.txt.
2260 slub_min_order= [MM, SLUB]
2261 Determines the mininum page order for slabs. Must be
2262 lower than slub_max_order.
2263 For more information see Documentation/vm/slub.txt.
2265 slub_nomerge [MM, SLUB]
2266 Disable merging of slabs with similar size. May be
2267 necessary if there is some reason to distinguish
2268 allocs to different slabs. Debug options disable
2269 merging on their own.
2270 For more information see Documentation/vm/slub.txt.
2272 smart2= [HW]
2273 Format: <io1>[,<io2>[,...,<io8>]]
2275 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2276 attempt to substitute SMP alternatives once at boot.
2278 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2279 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2280 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2281 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2282 smsc-ircc2.ircc_irq= [HW] IRQ line
2283 smsc-ircc2.ircc_dma= [HW] DMA channel
2284 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2285 0: Toshiba Satellite 1800 (GP data pin select)
2286 1: Fast pin select (default)
2287 2: ATC IRMode
2289 softlockup_panic=
2290 [KNL] Should the soft-lockup detector generate panics.
2292 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2293 See Documentation/sonypi.txt
2295 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2296 See Documentation/serial/specialix.txt.
2298 spia_io_base= [HW,MTD]
2299 spia_fio_base=
2300 spia_pedr=
2301 spia_peddr=
2303 stacktrace [FTRACE]
2304 Enabled the stack tracer on boot up.
2306 sti= [PARISC,HW]
2307 Format: <num>
2308 Set the STI (builtin display/keyboard on the HP-PARISC
2309 machines) console (graphic card) which should be used
2310 as the initial boot-console.
2311 See also comment in drivers/video/console/sticore.c.
2313 sti_font= [HW]
2314 See comment in drivers/video/console/sticore.c.
2316 stifb= [HW]
2317 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2319 sunrpc.min_resvport=
2320 sunrpc.max_resvport=
2321 [NFS,SUNRPC]
2322 SunRPC servers often require that client requests
2323 originate from a privileged port (i.e. a port in the
2324 range 0 < portnr < 1024).
2325 An administrator who wishes to reserve some of these
2326 ports for other uses may adjust the range that the
2327 kernel's sunrpc client considers to be privileged
2328 using these two parameters to set the minimum and
2329 maximum port values.
2331 sunrpc.pool_mode=
2332 [NFS]
2333 Control how the NFS server code allocates CPUs to
2334 service thread pools. Depending on how many NICs
2335 you have and where their interrupts are bound, this
2336 option will affect which CPUs will do NFS serving.
2337 Note: this parameter cannot be changed while the
2338 NFS server is running.
2340 auto the server chooses an appropriate mode
2341 automatically using heuristics
2342 global a single global pool contains all CPUs
2343 percpu one pool for each CPU
2344 pernode one pool for each NUMA node (equivalent
2345 to global on non-NUMA machines)
2347 sunrpc.tcp_slot_table_entries=
2348 sunrpc.udp_slot_table_entries=
2349 [NFS,SUNRPC]
2350 Sets the upper limit on the number of simultaneous
2351 RPC calls that can be sent from the client to a
2352 server. Increasing these values may allow you to
2353 improve throughput, but will also increase the
2354 amount of memory reserved for use by the client.
2356 swiotlb= [IA-64] Number of I/O TLB slabs
2358 switches= [HW,M68k]
2360 sysrq_always_enabled
2361 [KNL]
2362 Ignore sysrq setting - this boot parameter will
2363 neutralize any effect of /proc/sys/kernel/sysrq.
2364 Useful for debugging.
2366 tdfx= [HW,DRM]
2368 test_suspend= [SUSPEND]
2369 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2370 standby suspend) as the system sleep state to briefly
2371 enter during system startup. The system is woken from
2372 this state using a wakeup-capable RTC alarm.
2374 thash_entries= [KNL,NET]
2375 Set number of hash buckets for TCP connection
2377 thermal.act= [HW,ACPI]
2378 -1: disable all active trip points in all thermal zones
2379 <degrees C>: override all lowest active trip points
2381 thermal.crt= [HW,ACPI]
2382 -1: disable all critical trip points in all thermal zones
2383 <degrees C>: override all critical trip points
2385 thermal.nocrt= [HW,ACPI]
2386 Set to disable actions on ACPI thermal zone
2387 critical and hot trip points.
2389 thermal.off= [HW,ACPI]
2390 1: disable ACPI thermal control
2392 thermal.psv= [HW,ACPI]
2393 -1: disable all passive trip points
2394 <degrees C>: override all passive trip points to this
2395 value
2397 thermal.tzp= [HW,ACPI]
2398 Specify global default ACPI thermal zone polling rate
2399 <deci-seconds>: poll all this frequency
2400 0: no polling (default)
2402 topology= [S390]
2403 Format: {off | on}
2404 Specify if the kernel should make use of the cpu
2405 topology informations if the hardware supports these.
2406 The scheduler will make use of these informations and
2407 e.g. base its process migration decisions on it.
2408 Default is off.
2410 tp720= [HW,PS2]
2412 tpm_suspend_pcr=[HW,TPM]
2413 Format: integer pcr id
2414 Specify that at suspend time, the tpm driver
2415 should extend the specified pcr with zeros,
2416 as a workaround for some chips which fail to
2417 flush the last written pcr on TPM_SaveState.
2418 This will guarantee that all the other pcrs
2419 are saved.
2421 trace_buf_size=nn[KMG]
2422 [FTRACE] will set tracing buffer size.
2424 trace_event=[event-list]
2425 [FTRACE] Set and start specified trace events in order
2426 to facilitate early boot debugging.
2427 See also Documentation/trace/events.txt
2429 tsc= Disable clocksource-must-verify flag for TSC.
2430 Format: <string>
2431 [x86] reliable: mark tsc clocksource as reliable, this
2432 disables clocksource verification at runtime.
2433 Used to enable high-resolution timer mode on older
2434 hardware, and in virtualized environment.
2436 turbografx.map[2|3]= [HW,JOY]
2437 TurboGraFX parallel port interface
2438 Format:
2439 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2440 See also Documentation/input/joystick-parport.txt
2442 uhash_entries= [KNL,NET]
2443 Set number of hash buckets for UDP/UDP-Lite connections
2445 uhci-hcd.ignore_oc=
2446 [USB] Ignore overcurrent events (default N).
2447 Some badly-designed motherboards generate lots of
2448 bogus events, for ports that aren't wired to
2449 anything. Set this parameter to avoid log spamming.
2450 Note that genuine overcurrent events won't be
2451 reported either.
2453 unknown_nmi_panic
2454 [X86]
2455 Set unknown_nmi_panic=1 early on boot.
2457 usbcore.autosuspend=
2458 [USB] The autosuspend time delay (in seconds) used
2459 for newly-detected USB devices (default 2). This
2460 is the time required before an idle device will be
2461 autosuspended. Devices for which the delay is set
2462 to a negative value won't be autosuspended at all.
2464 usbcore.usbfs_snoop=
2465 [USB] Set to log all usbfs traffic (default 0 = off).
2467 usbcore.blinkenlights=
2468 [USB] Set to cycle leds on hubs (default 0 = off).
2470 usbcore.old_scheme_first=
2471 [USB] Start with the old device initialization
2472 scheme (default 0 = off).
2474 usbcore.use_both_schemes=
2475 [USB] Try the other device initialization scheme
2476 if the first one fails (default 1 = enabled).
2478 usbcore.initial_descriptor_timeout=
2479 [USB] Specifies timeout for the initial 64-byte
2480 USB_REQ_GET_DESCRIPTOR request in milliseconds
2481 (default 5000 = 5.0 seconds).
2483 usbhid.mousepoll=
2484 [USBHID] The interval which mice are to be polled at.
2486 usb-storage.delay_use=
2487 [UMS] The delay in seconds before a new device is
2488 scanned for Logical Units (default 5).
2490 usb-storage.quirks=
2491 [UMS] A list of quirks entries to supplement or
2492 override the built-in unusual_devs list. List
2493 entries are separated by commas. Each entry has
2494 the form VID:PID:Flags where VID and PID are Vendor
2495 and Product ID values (4-digit hex numbers) and
2496 Flags is a set of characters, each corresponding
2497 to a common usb-storage quirk flag as follows:
2498 a = SANE_SENSE (collect more than 18 bytes
2499 of sense data);
2500 b = BAD_SENSE (don't collect more than 18
2501 bytes of sense data);
2502 c = FIX_CAPACITY (decrease the reported
2503 device capacity by one sector);
2504 h = CAPACITY_HEURISTICS (decrease the
2505 reported device capacity by one
2506 sector if the number is odd);
2507 i = IGNORE_DEVICE (don't bind to this
2508 device);
2509 l = NOT_LOCKABLE (don't try to lock and
2510 unlock ejectable media);
2511 m = MAX_SECTORS_64 (don't transfer more
2512 than 64 sectors = 32 KB at a time);
2513 o = CAPACITY_OK (accept the capacity
2514 reported by the device);
2515 r = IGNORE_RESIDUE (the device reports
2516 bogus residue values);
2517 s = SINGLE_LUN (the device has only one
2518 Logical Unit);
2519 w = NO_WP_DETECT (don't test whether the
2520 medium is write-protected).
2521 Example: quirks=0419:aaf5:rl,0421:0433:rc
2523 userpte=
2524 [X86] Flags controlling user PTE allocations.
2526 nohigh = do not allocate PTE pages in
2527 HIGHMEM regardless of setting
2528 of CONFIG_HIGHPTE.
2530 vdso= [X86,SH]
2531 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2532 vdso=1: enable VDSO (default)
2533 vdso=0: disable VDSO mapping
2535 vdso32= [X86]
2536 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2537 vdso32=1: enable 32-bit VDSO (default)
2538 vdso32=0: disable 32-bit VDSO mapping
2540 vector= [IA-64,SMP]
2541 vector=percpu: enable percpu vector domain
2543 video= [FB] Frame buffer configuration
2544 See Documentation/fb/modedb.txt.
2546 vga= [BOOT,X86-32] Select a particular video mode
2547 See Documentation/x86/boot.txt and
2548 Documentation/svga.txt.
2549 Use vga=ask for menu.
2550 This is actually a boot loader parameter; the value is
2551 passed to the kernel using a special protocol.
2553 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2554 size of <nn>. This can be used to increase the
2555 minimum size (128MB on x86). It can also be used to
2556 decrease the size and leave more room for directly
2557 mapped kernel RAM.
2559 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2560 Format: <command>
2562 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2563 Format: <command>
2565 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2566 Format: <command>
2568 vt.cur_default= [VT] Default cursor shape.
2569 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2570 the parameters of the <Esc>[?A;B;Cc escape sequence;
2571 see VGA-softcursor.txt. Default: 2 = underline.
2573 vt.default_blu= [VT]
2574 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2575 Change the default blue palette of the console.
2576 This is a 16-member array composed of values
2577 ranging from 0-255.
2579 vt.default_grn= [VT]
2580 Format: <green0>,<green1>,<green2>,...,<green15>
2581 Change the default green palette of the console.
2582 This is a 16-member array composed of values
2583 ranging from 0-255.
2585 vt.default_red= [VT]
2586 Format: <red0>,<red1>,<red2>,...,<red15>
2587 Change the default red palette of the console.
2588 This is a 16-member array composed of values
2589 ranging from 0-255.
2591 vt.default_utf8=
2592 [VT]
2593 Format=<0|1>
2594 Set system-wide default UTF-8 mode for all tty's.
2595 Default is 1, i.e. UTF-8 mode is enabled for all
2596 newly opened terminals.
2598 vt.global_cursor_default=
2599 [VT]
2600 Format=<-1|0|1>
2601 Set system-wide default for whether a cursor
2602 is shown on new VTs. Default is -1,
2603 i.e. cursors will be created by default unless
2604 overridden by individual drivers. 0 will hide
2605 cursors, 1 will display them.
2607 watchdog timers [HW,WDT] For information on watchdog timers,
2608 see Documentation/watchdog/watchdog-parameters.txt
2609 or other driver-specific files in the
2610 Documentation/watchdog/ directory.
2612 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2613 default x2apic cluster mode on platforms
2614 supporting x2apic.
2616 x86_mrst_timer= [X86-32,APBT]
2617 Choose timer option for x86 Moorestown MID platform.
2618 Two valid options are apbt timer only and lapic timer
2619 plus one apbt timer for broadcast timer.
2620 x86_mrst_timer=apbt_only | lapic_and_apbt
2622 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2623 xd_geo= See header of drivers/block/xd.c.
2625 xen_emul_unplug= [HW,X86,XEN]
2626 Unplug Xen emulated devices
2627 Format: [unplug0,][unplug1]
2628 ide-disks -- unplug primary master IDE devices
2629 aux-ide-disks -- unplug non-primary-master IDE devices
2630 nics -- unplug network devices
2631 all -- unplug all emulated devices (NICs and IDE disks)
2632 unnecessary -- unplugging emulated devices is
2633 unnecessary even if the host did not respond to
2634 the unplug protocol
2635 never -- do not unplug even if version check succeeds
2637 xirc2ps_cs= [NET,PCMCIA]
2638 Format:
2639 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2641 ______________________________________________________________________
2643 TODO:
2645 Add more DRM drivers.