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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 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AVR32 AVR32 architecture is enabled.
38 AX25 Appropriate AX.25 support is enabled.
39 BLACKFIN Blackfin architecture is enabled.
40 DRM Direct Rendering Management support is enabled.
41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
46 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
52 LIBATA Libata driver is enabled
53 LP Printer support is enabled.
54 LOOP Loopback device support is enabled.
55 M68k M68k architecture is enabled.
56 These options have more detailed description inside of
57 Documentation/m68k/kernel-options.txt.
58 MCA MCA bus support is enabled.
59 MDA MDA console support is enabled.
60 MOUSE Appropriate mouse support is enabled.
61 MSI Message Signaled Interrupts (PCI).
62 MTD MTD (Memory Technology Device) support is enabled.
63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
65 GENERIC_TIME The generic timeofday code is enabled.
66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
72 PCIE PCI Express support is enabled.
73 PCMCIA The PCMCIA subsystem is enabled.
74 PNP Plug & Play support is enabled.
75 PPC PowerPC architecture is enabled.
76 PPT Parallel port support is enabled.
77 PS2 Appropriate PS/2 support is enabled.
78 RAM RAM disk support is enabled.
79 ROOTPLUG The example Root Plug LSM is enabled.
80 S390 S390 architecture is enabled.
81 SCSI Appropriate SCSI support is enabled.
82 A lot of drivers has their options described inside of
83 Documentation/scsi/.
84 SECURITY Different security models are enabled.
85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
87 SH SuperH architecture is enabled.
88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
90 SWSUSP Software suspend (hibernation) is enabled.
91 SUSPEND System suspend states are enabled.
92 FTRACE Function tracing enabled.
93 TS Appropriate touchscreen support is enabled.
94 UMS USB Mass Storage support is enabled.
95 USB USB support is enabled.
96 USBHID USB Human Interface Device support is enabled.
97 V4L Video For Linux support is enabled.
98 VGA The VGA console has been enabled.
99 VT Virtual terminal support is enabled.
100 WDT Watchdog support is enabled.
101 XT IBM PC/XT MFM hard disk support is enabled.
102 X86-32 X86-32, aka i386 architecture is enabled.
103 X86-64 X86-64 architecture is enabled.
104 More X86-64 boot options can be found in
105 Documentation/x86/x86_64/boot-options.txt .
106 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
108 In addition, the following text indicates that the option:
110 BUGS= Relates to possible processor bugs on the said processor.
111 KNL Is a kernel start-up parameter.
112 BOOT Is a boot loader parameter.
114 Parameters denoted with BOOT are actually interpreted by the boot
115 loader, and have no meaning to the kernel directly.
116 Do not modify the syntax of boot loader parameters without extreme
117 need or coordination with <Documentation/x86/i386/boot.txt>.
119 There are also arch-specific kernel-parameters not documented here.
120 See for example <Documentation/x86/x86_64/boot-options.txt>.
122 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
123 a trailing = on the name of any parameter states that that parameter will
124 be entered as an environment variable, whereas its absence indicates that
125 it will appear as a kernel argument readable via /proc/cmdline by programs
126 running once the system is up.
128 The number of kernel parameters is not limited, but the length of the
129 complete command line (parameters including spaces etc.) is limited to
130 a fixed number of characters. This limit depends on the architecture
131 and is between 256 and 4096 characters. It is defined in the file
132 ./include/asm/setup.h as COMMAND_LINE_SIZE.
135 acpi= [HW,ACPI,X86-64,i386]
136 Advanced Configuration and Power Interface
137 Format: { force | off | ht | strict | noirq }
138 force -- enable ACPI if default was off
139 off -- disable ACPI if default was on
140 noirq -- do not use ACPI for IRQ routing
141 ht -- run only enough ACPI to enable Hyper Threading
142 strict -- Be less tolerant of platforms that are not
143 strictly ACPI specification compliant.
144 rsdt -- prefer RSDT over (default) XSDT
146 See also Documentation/power/pm.txt, pci=noacpi
148 acpi_apic_instance= [ACPI, IOAPIC]
149 Format: <int>
150 2: use 2nd APIC table, if available
151 1,0: use 1st APIC table
152 default: 0
154 acpi_sleep= [HW,ACPI] Sleep options
155 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
156 old_ordering, s4_nonvs }
157 See Documentation/power/video.txt for information on
158 s3_bios and s3_mode.
159 s3_beep is for debugging; it makes the PC's speaker beep
160 as soon as the kernel's real-mode entry point is called.
161 s4_nohwsig prevents ACPI hardware signature from being
162 used during resume from hibernation.
163 old_ordering causes the ACPI 1.0 ordering of the _PTS
164 control method, with respect to putting devices into
165 low power states, to be enforced (the ACPI 2.0 ordering
166 of _PTS is used by default).
167 s4_nonvs prevents the kernel from saving/restoring the
168 ACPI NVS memory during hibernation.
170 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
171 Format: { level | edge | high | low }
173 acpi_irq_balance [HW,ACPI]
174 ACPI will balance active IRQs
175 default in APIC mode
177 acpi_irq_nobalance [HW,ACPI]
178 ACPI will not move active IRQs (default)
179 default in PIC mode
181 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
182 use by PCI
183 Format: <irq>,<irq>...
185 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
186 Format: <irq>,<irq>...
188 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
190 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
191 Format: To spoof as Windows 98: ="Microsoft Windows"
193 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
194 acpi_osi="string1" # add string1 -- only one string
195 acpi_osi="!string2" # remove built-in string2
196 acpi_osi= # disable all strings
198 acpi_serialize [HW,ACPI] force serialization of AML methods
200 acpi_skip_timer_override [HW,ACPI]
201 Recognize and ignore IRQ0/pin2 Interrupt Override.
202 For broken nForce2 BIOS resulting in XT-PIC timer.
203 acpi_use_timer_override [HW,ACPI]
204 Use timer override. For some broken Nvidia NF5 boards
205 that require a timer override, but don't have
206 HPET
208 acpi_backlight= [HW,ACPI]
209 acpi_backlight=vendor
210 acpi_backlight=video
211 If set to vendor, prefer vendor specific driver
212 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
213 of the ACPI video.ko driver.
215 acpi_display_output= [HW,ACPI]
216 acpi_display_output=vendor
217 acpi_display_output=video
218 See above.
220 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
221 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
222 Format: <int>
223 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
224 debug output. Bits in debug_layer correspond to a
225 _COMPONENT in an ACPI source file, e.g.,
226 #define _COMPONENT ACPI_PCI_COMPONENT
227 Bits in debug_level correspond to a level in
228 ACPI_DEBUG_PRINT statements, e.g.,
229 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
230 The debug_level mask defaults to "info". See
231 Documentation/acpi/debug.txt for more information about
232 debug layers and levels.
234 Enable processor driver info messages:
235 acpi.debug_layer=0x20000000
236 Enable PCI/PCI interrupt routing info messages:
237 acpi.debug_layer=0x400000
238 Enable AML "Debug" output, i.e., stores to the Debug
239 object while interpreting AML:
240 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
241 Enable all messages related to ACPI hardware:
242 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
244 Some values produce so much output that the system is
245 unusable. The "log_buf_len" parameter may be useful
246 if you need to capture more output.
248 acpi.power_nocheck= [HW,ACPI]
249 Format: 1/0 enable/disable the check of power state.
250 On some bogus BIOS the _PSC object/_STA object of
251 power resource can't return the correct device power
252 state. In such case it is unneccessary to check its
253 power state again in power transition.
254 1 : disable the power state check
256 acpi_pm_good [X86-32,X86-64]
257 Override the pmtimer bug detection: force the kernel
258 to assume that this machine's pmtimer latches its value
259 and always returns good values.
261 agp= [AGP]
262 { off | try_unsupported }
263 off: disable AGP support
264 try_unsupported: try to drive unsupported chipsets
265 (may crash computer or cause data corruption)
267 enable_timer_pin_1 [i386,x86-64]
268 Enable PIN 1 of APIC timer
269 Can be useful to work around chipset bugs
270 (in particular on some ATI chipsets).
271 The kernel tries to set a reasonable default.
273 disable_timer_pin_1 [i386,x86-64]
274 Disable PIN 1 of APIC timer
275 Can be useful to work around chipset bugs.
277 ad1848= [HW,OSS]
278 Format: <io>,<irq>,<dma>,<dma2>,<type>
280 advansys= [HW,SCSI]
281 See header of drivers/scsi/advansys.c.
283 advwdt= [HW,WDT] Advantech WDT
284 Format: <iostart>,<iostop>
286 aedsp16= [HW,OSS] Audio Excel DSP 16
287 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
288 See also header of sound/oss/aedsp16.c.
290 aha152x= [HW,SCSI]
291 See Documentation/scsi/aha152x.txt.
293 aha1542= [HW,SCSI]
294 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
296 aic7xxx= [HW,SCSI]
297 See Documentation/scsi/aic7xxx.txt.
299 aic79xx= [HW,SCSI]
300 See Documentation/scsi/aic79xx.txt.
302 amd_iommu= [HW,X86-84]
303 Pass parameters to the AMD IOMMU driver in the system.
304 Possible values are:
305 isolate - enable device isolation (each device, as far
306 as possible, will get its own protection
307 domain) [default]
308 share - put every device behind one IOMMU into the
309 same protection domain
310 fullflush - enable flushing of IO/TLB entries when
311 they are unmapped. Otherwise they are
312 flushed before they will be reused, which
313 is a lot of faster
315 amd_iommu_size= [HW,X86-64]
316 Define the size of the aperture for the AMD IOMMU
317 driver. Possible values are:
318 '32M', '64M' (default), '128M', '256M', '512M', '1G'
320 amijoy.map= [HW,JOY] Amiga joystick support
321 Map of devices attached to JOY0DAT and JOY1DAT
322 Format: <a>,<b>
323 See also Documentation/kernel/input/joystick.txt
325 analog.map= [HW,JOY] Analog joystick and gamepad support
326 Specifies type or capabilities of an analog joystick
327 connected to one of 16 gameports
328 Format: <type1>,<type2>,..<type16>
330 apc= [HW,SPARC]
331 Power management functions (SPARCstation-4/5 + deriv.)
332 Format: noidle
333 Disable APC CPU standby support. SPARCstation-Fox does
334 not play well with APC CPU idle - disable it if you have
335 APC and your system crashes randomly.
337 apic= [APIC,i386] Advanced Programmable Interrupt Controller
338 Change the output verbosity whilst booting
339 Format: { quiet (default) | verbose | debug }
340 Change the amount of debugging information output
341 when initialising the APIC and IO-APIC components.
343 apm= [APM] Advanced Power Management
344 See header of arch/x86/kernel/apm_32.c.
346 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
347 Format: <io>,<irq>,<nodeID>
349 ataflop= [HW,M68k]
351 atarimouse= [HW,MOUSE] Atari Mouse
353 atascsi= [HW,SCSI] Atari SCSI
355 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
356 EzKey and similar keyboards
358 atkbd.reset= [HW] Reset keyboard during initialization
360 atkbd.set= [HW] Select keyboard code set
361 Format: <int> (2 = AT (default), 3 = PS/2)
363 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
364 keyboards
366 atkbd.softraw= [HW] Choose between synthetic and real raw mode
367 Format: <bool> (0 = real, 1 = synthetic (default))
369 atkbd.softrepeat= [HW]
370 Use software keyboard repeat
372 autotest [IA64]
374 baycom_epp= [HW,AX25]
375 Format: <io>,<mode>
377 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
378 Format: <io>,<mode>
379 See header of drivers/net/hamradio/baycom_par.c.
381 baycom_ser_fdx= [HW,AX25]
382 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
383 Format: <io>,<irq>,<mode>[,<baud>]
384 See header of drivers/net/hamradio/baycom_ser_fdx.c.
386 baycom_ser_hdx= [HW,AX25]
387 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
388 Format: <io>,<irq>,<mode>
389 See header of drivers/net/hamradio/baycom_ser_hdx.c.
391 boot_delay= Milliseconds to delay each printk during boot.
392 Values larger than 10 seconds (10000) are changed to
393 no delay (0).
394 Format: integer
396 bootmem_debug [KNL] Enable bootmem allocator debug messages.
398 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
399 bttv.radio= Most important insmod options are available as
400 kernel args too.
401 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
402 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
404 BusLogic= [HW,SCSI]
405 See drivers/scsi/BusLogic.c, comment before function
406 BusLogic_ParseDriverOptions().
408 c101= [NET] Moxa C101 synchronous serial card
410 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
411 Sometimes CPU hardware bugs make them report the cache
412 size incorrectly. The kernel will attempt work arounds
413 to fix known problems, but for some CPUs it is not
414 possible to determine what the correct size should be.
415 This option provides an override for these situations.
417 security= [SECURITY] Choose a security module to enable at boot.
418 If this boot parameter is not specified, only the first
419 security module asking for security registration will be
420 loaded. An invalid security module name will be treated
421 as if no module has been chosen.
423 capability.disable=
424 [SECURITY] Disable capabilities. This would normally
425 be used only if an alternative security model is to be
426 configured. Potentially dangerous and should only be
427 used if you are entirely sure of the consequences.
429 ccw_timeout_log [S390]
430 See Documentation/s390/CommonIO for details.
432 cgroup_disable= [KNL] Disable a particular controller
433 Format: {name of the controller(s) to disable}
434 {Currently supported controllers - "memory"}
436 checkreqprot [SELINUX] Set initial checkreqprot flag value.
437 Format: { "0" | "1" }
438 See security/selinux/Kconfig help text.
439 0 -- check protection applied by kernel (includes
440 any implied execute protection).
441 1 -- check protection requested by application.
442 Default value is set via a kernel config option.
443 Value can be changed at runtime via
444 /selinux/checkreqprot.
446 cio_ignore= [S390]
447 See Documentation/s390/CommonIO for details.
449 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
450 [Deprecated]
451 Forces specified clocksource (if available) to be used
452 when calculating gettimeofday(). If specified
453 clocksource is not available, it defaults to PIT.
454 Format: { pit | tsc | cyclone | pmtmr }
456 clocksource= [GENERIC_TIME] Override the default clocksource
457 Format: <string>
458 Override the default clocksource and use the clocksource
459 with the name specified.
460 Some clocksource names to choose from, depending on
461 the platform:
462 [all] jiffies (this is the base, fallback clocksource)
463 [ACPI] acpi_pm
464 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
465 pxa_timer,timer3,32k_counter,timer0_1
466 [AVR32] avr32
467 [X86-32] pit,hpet,tsc,vmi-timer;
468 scx200_hrt on Geode; cyclone on IBM x440
469 [MIPS] MIPS
470 [PARISC] cr16
471 [S390] tod
472 [SH] SuperH
473 [SPARC64] tick
474 [X86-64] hpet,tsc
476 clearcpuid=BITNUM [X86]
477 Disable CPUID feature X for the kernel. See
478 arch/x86/include/asm/cpufeature.h for the valid bit
479 numbers. Note the Linux specific bits are not necessarily
480 stable over kernel options, but the vendor specific
481 ones should be.
482 Also note that user programs calling CPUID directly
483 or using the feature without checking anything
484 will still see it. This just prevents it from
485 being used by the kernel or shown in /proc/cpuinfo.
486 Also note the kernel might malfunction if you disable
487 some critical bits.
489 code_bytes [IA32/X86_64] How many bytes of object code to print
490 in an oops report.
491 Range: 0 - 8192
492 Default: 64
494 hpet= [X86-32,HPET] option to control HPET usage
495 Format: { enable (default) | disable | force }
496 disable: disable HPET and use PIT instead
497 force: allow force enabled of undocumented chips (ICH4,
498 VIA, nVidia)
500 com20020= [HW,NET] ARCnet - COM20020 chipset
501 Format:
502 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
504 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
505 Format: <io>[,<irq>]
507 com90xx= [HW,NET]
508 ARCnet - COM90xx chipset (memory-mapped buffers)
509 Format: <io>[,<irq>[,<memstart>]]
511 condev= [HW,S390] console device
512 conmode=
514 console= [KNL] Output console device and options.
516 tty<n> Use the virtual console device <n>.
518 ttyS<n>[,options]
519 ttyUSB0[,options]
520 Use the specified serial port. The options are of
521 the form "bbbbpnf", where "bbbb" is the baud rate,
522 "p" is parity ("n", "o", or "e"), "n" is number of
523 bits, and "f" is flow control ("r" for RTS or
524 omit it). Default is "9600n8".
526 See Documentation/serial-console.txt for more
527 information. See
528 Documentation/networking/netconsole.txt for an
529 alternative.
531 uart[8250],io,<addr>[,options]
532 uart[8250],mmio,<addr>[,options]
533 Start an early, polled-mode console on the 8250/16550
534 UART at the specified I/O port or MMIO address,
535 switching to the matching ttyS device later. The
536 options are the same as for ttyS, above.
538 If the device connected to the port is not a TTY but a braille
539 device, prepend "brl," before the device type, for instance
540 console=brl,ttyS0
541 For now, only VisioBraille is supported.
543 earlycon= [KNL] Output early console device and options.
544 uart[8250],io,<addr>[,options]
545 uart[8250],mmio,<addr>[,options]
546 Start an early, polled-mode console on the 8250/16550
547 UART at the specified I/O port or MMIO address.
548 The options are the same as for ttyS, above.
550 no_console_suspend
551 [HW] Never suspend the console
552 Disable suspending of consoles during suspend and
553 hibernate operations. Once disabled, debugging
554 messages can reach various consoles while the rest
555 of the system is being put to sleep (ie, while
556 debugging driver suspend/resume hooks). This may
557 not work reliably with all consoles, but is known
558 to work with serial and VGA consoles.
560 coredump_filter=
561 [KNL] Change the default value for
562 /proc/<pid>/coredump_filter.
563 See also Documentation/filesystems/proc.txt.
565 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
566 Format:
567 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
569 crashkernel=nn[KMG]@ss[KMG]
570 [KNL] Reserve a chunk of physical memory to
571 hold a kernel to switch to with kexec on panic.
573 crashkernel=range1:size1[,range2:size2,...][@offset]
574 [KNL] Same as above, but depends on the memory
575 in the running system. The syntax of range is
576 start-[end] where start and end are both
577 a memory unit (amount[KMG]). See also
578 Documentation/kdump/kdump.txt for a example.
580 cs89x0_dma= [HW,NET]
581 Format: <dma>
583 cs89x0_media= [HW,NET]
584 Format: { rj45 | aui | bnc }
586 dasd= [HW,NET]
587 See header of drivers/s390/block/dasd_devmap.c.
589 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
590 (one device per port)
591 Format: <port#>,<type>
592 See also Documentation/input/joystick-parport.txt
594 debug [KNL] Enable kernel debugging (events log level).
596 debug_locks_verbose=
597 [KNL] verbose self-tests
598 Format=<0|1>
599 Print debugging info while doing the locking API
600 self-tests.
601 We default to 0 (no extra messages), setting it to
602 1 will print _a lot_ more information - normally
603 only useful to kernel developers.
605 debug_objects [KNL] Enable object debugging
607 debugpat [X86] Enable PAT debugging
609 decnet.addr= [HW,NET]
610 Format: <area>[,<node>]
611 See also Documentation/networking/decnet.txt.
613 vt.default_blu= [VT]
614 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
615 Change the default blue palette of the console.
616 This is a 16-member array composed of values
617 ranging from 0-255.
619 vt.default_grn= [VT]
620 Format: <green0>,<green1>,<green2>,...,<green15>
621 Change the default green palette of the console.
622 This is a 16-member array composed of values
623 ranging from 0-255.
625 vt.default_red= [VT]
626 Format: <red0>,<red1>,<red2>,...,<red15>
627 Change the default red palette of the console.
628 This is a 16-member array composed of values
629 ranging from 0-255.
631 vt.default_utf8=
632 [VT]
633 Format=<0|1>
634 Set system-wide default UTF-8 mode for all tty's.
635 Default is 1, i.e. UTF-8 mode is enabled for all
636 newly opened terminals.
638 dhash_entries= [KNL]
639 Set number of hash buckets for dentry cache.
641 digi= [HW,SERIAL]
642 IO parameters + enable/disable command.
644 digiepca= [HW,SERIAL]
645 See drivers/char/README.epca and
646 Documentation/serial/digiepca.txt.
648 disable_mtrr_cleanup [X86]
649 enable_mtrr_cleanup [X86]
650 The kernel tries to adjust MTRR layout from continuous
651 to discrete, to make X server driver able to add WB
652 entry later. This parameter enables/disables that.
654 mtrr_chunk_size=nn[KMG] [X86]
655 used for mtrr cleanup. It is largest continous chunk
656 that could hold holes aka. UC entries.
658 mtrr_gran_size=nn[KMG] [X86]
659 Used for mtrr cleanup. It is granularity of mtrr block.
660 Default is 1.
661 Large value could prevent small alignment from
662 using up MTRRs.
664 mtrr_spare_reg_nr=n [X86]
665 Format: <integer>
666 Range: 0,7 : spare reg number
667 Default : 1
668 Used for mtrr cleanup. It is spare mtrr entries number.
669 Set to 2 or more if your graphical card needs more.
671 disable_mtrr_trim [X86, Intel and AMD only]
672 By default the kernel will trim any uncacheable
673 memory out of your available memory pool based on
674 MTRR settings. This parameter disables that behavior,
675 possibly causing your machine to run very slowly.
677 dmasound= [HW,OSS] Sound subsystem buffers
679 dscc4.setup= [NET]
681 dtc3181e= [HW,SCSI]
683 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
684 earlyprintk=vga
685 earlyprintk=serial[,ttySn[,baudrate]]
686 earlyprintk=dbgp
688 Append ",keep" to not disable it when the real console
689 takes over.
691 Only vga or serial or usb debug port at a time.
693 Currently only ttyS0 and ttyS1 are supported.
695 Interaction with the standard serial driver is not
696 very good.
698 The VGA output is eventually overwritten by the real
699 console.
701 eata= [HW,SCSI]
703 edd= [EDD]
704 Format: {"off" | "on" | "skip[mbr]"}
706 eisa_irq_edge= [PARISC,HW]
707 See header of drivers/parisc/eisa.c.
709 elanfreq= [X86-32]
710 See comment before function elanfreq_setup() in
711 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
713 elevator= [IOSCHED]
714 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
715 See Documentation/block/as-iosched.txt and
716 Documentation/block/deadline-iosched.txt for details.
718 elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
719 Specifies physical address of start of kernel core
720 image elf header. Generally kexec loader will
721 pass this option to capture kernel.
722 See Documentation/kdump/kdump.txt for details.
724 enforcing [SELINUX] Set initial enforcing status.
725 Format: {"0" | "1"}
726 See security/selinux/Kconfig help text.
727 0 -- permissive (log only, no denials).
728 1 -- enforcing (deny and log).
729 Default value is 0.
730 Value can be changed at runtime via /selinux/enforce.
732 ether= [HW,NET] Ethernet cards parameters
733 This option is obsoleted by the "netdev=" option, which
734 has equivalent usage. See its documentation for details.
736 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
737 Format: <io>[,<irq>]
739 failslab=
740 fail_page_alloc=
741 fail_make_request=[KNL]
742 General fault injection mechanism.
743 Format: <interval>,<probability>,<space>,<times>
744 See also /Documentation/fault-injection/.
746 fd_mcs= [HW,SCSI]
747 See header of drivers/scsi/fd_mcs.c.
749 fdomain= [HW,SCSI]
750 See header of drivers/scsi/fdomain.c.
752 floppy= [HW]
753 See Documentation/blockdev/floppy.txt.
755 force_pal_cache_flush
756 [IA-64] Avoid check_sal_cache_flush which may hang on
757 buggy SAL_CACHE_FLUSH implementations. Using this
758 parameter will force ia64_sal_cache_flush to call
759 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
761 ftrace=[tracer]
762 [ftrace] will set and start the specified tracer
763 as early as possible in order to facilitate early
764 boot debugging.
766 ftrace_dump_on_oops
767 [ftrace] will dump the trace buffers on oops.
769 gamecon.map[2|3]=
770 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
771 support via parallel port (up to 5 devices per port)
772 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
773 See also Documentation/input/joystick-parport.txt
775 gamma= [HW,DRM]
777 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
778 Format: off | on
779 default: on
781 gdth= [HW,SCSI]
782 See header of drivers/scsi/gdth.c.
784 gpt [EFI] Forces disk with valid GPT signature but
785 invalid Protective MBR to be treated as GPT.
787 gvp11= [HW,SCSI]
789 hashdist= [KNL,NUMA] Large hashes allocated during boot
790 are distributed across NUMA nodes. Defaults on
791 for IA-64, off otherwise.
792 Format: 0 | 1 (for off | on)
794 hcl= [IA-64] SGI's Hardware Graph compatibility layer
796 hd= [EIDE] (E)IDE hard drive subsystem geometry
797 Format: <cyl>,<head>,<sect>
799 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
800 size of <nn>. This works even on boxes that have no
801 highmem otherwise. This also works to reduce highmem
802 size on bigger boxes.
804 highres= [KNL] Enable/disable high resolution timer mode.
805 Valid parameters: "on", "off"
806 Default: "on"
808 hisax= [HW,ISDN]
809 See Documentation/isdn/README.HiSax.
811 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
812 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
813 On x86-64 and powerpc, this option can be specified
814 multiple times interleaved with hugepages= to reserve
815 huge pages of different sizes. Valid pages sizes on
816 x86-64 are 2M (when the CPU supports "pse") and 1G
817 (when the CPU supports the "pdpe1gb" cpuinfo flag)
818 Note that 1GB pages can only be allocated at boot time
819 using hugepages= and not freed afterwards.
820 default_hugepagesz=
821 [same as hugepagesz=] The size of the default
822 HugeTLB page size. This is the size represented by
823 the legacy /proc/ hugepages APIs, used for SHM, and
824 default size when mounting hugetlbfs filesystems.
825 Defaults to the default architecture's huge page size
826 if not specified.
828 hlt [BUGS=ARM,SH]
830 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
831 terminal devices. Valid values: 0..8
833 i8042.debug [HW] Toggle i8042 debug mode
834 i8042.direct [HW] Put keyboard port into non-translated mode
835 i8042.dumbkbd [HW] Pretend that controller can only read data from
836 keyboard and cannot control its state
837 (Don't attempt to blink the leds)
838 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
839 i8042.nokbd [HW] Don't check/create keyboard port
840 i8042.noloop [HW] Disable the AUX Loopback command while probing
841 for the AUX port
842 i8042.nomux [HW] Don't check presence of an active multiplexing
843 controller
844 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
845 controllers
846 i8042.panicblink=
847 [HW] Frequency with which keyboard LEDs should blink
848 when kernel panics (default is 0.5 sec)
849 i8042.reset [HW] Reset the controller during init and cleanup
850 i8042.unlock [HW] Unlock (ignore) the keylock
852 i810= [HW,DRM]
854 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
855 indicates that the driver is running on unsupported
856 hardware.
857 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
858 does not match list of supported models.
859 i8k.power_status
860 [HW] Report power status in /proc/i8k
861 (disabled by default)
862 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
863 capability is set.
865 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
866 See Documentation/mca.txt.
868 icn= [HW,ISDN]
869 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
871 ide= [HW] (E)IDE subsystem
872 Format: ide=nodma or ide=doubler
873 See Documentation/ide/ide.txt.
875 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
876 See Documentation/ide/ide.txt.
878 idle= [X86]
879 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
880 Poll forces a polling idle loop that can slightly
881 improve the performance of waking up a idle CPU, but
882 will use a lot of power and make the system run hot.
883 Not recommended.
884 idle=mwait: On systems which support MONITOR/MWAIT but
885 the kernel chose to not use it because it doesn't save
886 as much power as a normal idle loop, use the
887 MONITOR/MWAIT idle loop anyways. Performance should be
888 the same as idle=poll.
889 idle=halt: Halt is forced to be used for CPU idle.
890 In such case C2/C3 won't be used again.
891 idle=nomwait: Disable mwait for CPU C-states
893 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
894 Claim all unknown PCI IDE storage controllers.
896 ignore_loglevel [KNL]
897 Ignore loglevel setting - this will print /all/
898 kernel messages to the console. Useful for debugging.
900 ihash_entries= [KNL]
901 Set number of hash buckets for inode cache.
903 in2000= [HW,SCSI]
904 See header of drivers/scsi/in2000.c.
906 init= [KNL]
907 Format: <full_path>
908 Run specified binary instead of /sbin/init as init
909 process.
911 initcall_debug [KNL] Trace initcalls as they are executed. Useful
912 for working out where the kernel is dying during
913 startup.
915 initrd= [BOOT] Specify the location of the initial ramdisk
917 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
918 Format: <irq>
920 inttest= [IA64]
922 iomem= Disable strict checking of access to MMIO memory
923 strict regions from userspace.
924 relaxed
926 iommu= [x86]
927 off
928 force
929 noforce
930 biomerge
931 panic
932 nopanic
933 merge
934 nomerge
935 forcesac
936 soft
939 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
940 off
941 Disable intel iommu driver.
942 igfx_off [Default Off]
943 By default, gfx is mapped as normal device. If a gfx
944 device has a dedicated DMAR unit, the DMAR unit is
945 bypassed by not enabling DMAR with this option. In
946 this case, gfx device will use physical address for
947 DMA.
948 forcedac [x86_64]
949 With this option iommu will not optimize to look
950 for io virtual address below 32 bit forcing dual
951 address cycle on pci bus for cards supporting greater
952 than 32 bit addressing. The default is to look
953 for translation below 32 bit and if not available
954 then look in the higher range.
955 strict [Default Off]
956 With this option on every unmap_single operation will
957 result in a hardware IOTLB flush operation as opposed
958 to batching them for performance.
960 io_delay= [X86-32,X86-64] I/O delay method
961 0x80
962 Standard port 0x80 based delay
963 0xed
964 Alternate port 0xed based delay (needed on some systems)
965 udelay
966 Simple two microseconds delay
967 none
968 No delay
970 io7= [HW] IO7 for Marvel based alpha systems
971 See comment before marvel_specify_io7 in
972 arch/alpha/kernel/core_marvel.c.
974 ip= [IP_PNP]
975 See Documentation/filesystems/nfsroot.txt.
977 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
978 See comment before ip2_setup() in
979 drivers/char/ip2/ip2base.c.
981 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
982 See header of drivers/scsi/ips.c.
984 ports= [IP_VS_FTP] IPVS ftp helper module
985 Default is 21.
986 Up to 8 (IP_VS_APP_MAX_PORTS) ports
987 may be specified.
988 Format: <port>,<port>....
990 irqfixup [HW]
991 When an interrupt is not handled search all handlers
992 for it. Intended to get systems with badly broken
993 firmware running.
995 irqpoll [HW]
996 When an interrupt is not handled search all handlers
997 for it. Also check all handlers each timer
998 interrupt. Intended to get systems with badly broken
999 firmware running.
1001 isapnp= [ISAPNP]
1002 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1004 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1005 Format:
1006 <cpu number>,...,<cpu number>
1007 or
1008 <cpu number>-<cpu number>
1009 (must be a positive range in ascending order)
1010 or a mixture
1011 <cpu number>,...,<cpu number>-<cpu number>
1013 This option can be used to specify one or more CPUs
1014 to isolate from the general SMP balancing and scheduling
1015 algorithms. You can move a process onto or off an
1016 "isolated" CPU via the CPU affinity syscalls or cpuset.
1017 <cpu number> begins at 0 and the maximum value is
1018 "number of CPUs in system - 1".
1020 This option is the preferred way to isolate CPUs. The
1021 alternative -- manually setting the CPU mask of all
1022 tasks in the system -- can cause problems and
1023 suboptimal load balancer performance.
1025 iucv= [HW,NET]
1027 js= [HW,JOY] Analog joystick
1028 See Documentation/input/joystick.txt.
1030 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1031 specifies the amount of memory usable by the kernel
1032 for non-movable allocations. The requested amount is
1033 spread evenly throughout all nodes in the system. The
1034 remaining memory in each node is used for Movable
1035 pages. In the event, a node is too small to have both
1036 kernelcore and Movable pages, kernelcore pages will
1037 take priority and other nodes will have a larger number
1038 of kernelcore pages. The Movable zone is used for the
1039 allocation of pages that may be reclaimed or moved
1040 by the page migration subsystem. This means that
1041 HugeTLB pages may not be allocated from this zone.
1042 Note that allocations like PTEs-from-HighMem still
1043 use the HighMem zone if it exists, and the Normal
1044 zone if it does not.
1046 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1047 is similar to kernelcore except it specifies the
1048 amount of memory used for migratable allocations.
1049 If both kernelcore and movablecore is specified,
1050 then kernelcore will be at *least* the specified
1051 value but may be more. If movablecore on its own
1052 is specified, the administrator must be careful
1053 that the amount of memory usable for all allocations
1054 is not too small.
1056 keepinitrd [HW,ARM]
1058 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1059 in oops dumps.
1061 kgdboc= [HW] kgdb over consoles.
1062 Requires a tty driver that supports console polling.
1063 (only serial suported for now)
1064 Format: <serial_device>[,baud]
1066 kmac= [MIPS] korina ethernet MAC address.
1067 Configure the RouterBoard 532 series on-chip
1068 Ethernet adapter MAC address.
1070 l2cr= [PPC]
1072 l3cr= [PPC]
1074 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1075 disabled it.
1077 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer
1078 in C2 power state.
1080 libata.dma= [LIBATA] DMA control
1081 libata.dma=0 Disable all PATA and SATA DMA
1082 libata.dma=1 PATA and SATA Disk DMA only
1083 libata.dma=2 ATAPI (CDROM) DMA only
1084 libata.dma=4 Compact Flash DMA only
1085 Combinations also work, so libata.dma=3 enables DMA
1086 for disks and CDROMs, but not CFs.
1088 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1089 when set.
1090 Format: <int>
1092 libata.force= [LIBATA] Force configurations. The format is comma
1093 separated list of "[ID:]VAL" where ID is
1094 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1095 matching port, link or device. Basically, it matches
1096 the ATA ID string printed on console by libata. If
1097 the whole ID part is omitted, the last PORT and DEVICE
1098 values are used. If ID hasn't been specified yet, the
1099 configuration applies to all ports, links and devices.
1101 If only DEVICE is omitted, the parameter applies to
1102 the port and all links and devices behind it. DEVICE
1103 number of 0 either selects the first device or the
1104 first fan-out link behind PMP device. It does not
1105 select the host link. DEVICE number of 15 selects the
1106 host link and device attached to it.
1108 The VAL specifies the configuration to force. As long
1109 as there's no ambiguity shortcut notation is allowed.
1110 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1111 The following configurations can be forced.
1113 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1114 Any ID with matching PORT is used.
1116 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1118 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1119 udma[/][16,25,33,44,66,100,133] notation is also
1120 allowed.
1122 * [no]ncq: Turn on or off NCQ.
1124 * nohrst, nosrst, norst: suppress hard, soft
1125 and both resets.
1127 If there are multiple matching configurations changing
1128 the same attribute, the last one is used.
1130 lmb=debug [KNL] Enable lmb debug messages.
1132 load_ramdisk= [RAM] List of ramdisks to load from floppy
1133 See Documentation/blockdev/ramdisk.txt.
1135 lockd.nlm_grace_period=P [NFS] Assign grace period.
1136 Format: <integer>
1138 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1139 Format: <integer>
1141 lockd.nlm_timeout=T [NFS] Assign timeout value.
1142 Format: <integer>
1144 lockd.nlm_udpport=M [NFS] Assign UDP port.
1145 Format: <integer>
1147 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1148 Format: <irq>
1150 loglevel= All Kernel Messages with a loglevel smaller than the
1151 console loglevel will be printed to the console. It can
1152 also be changed with klogd or other programs. The
1153 loglevels are defined as follows:
1155 0 (KERN_EMERG) system is unusable
1156 1 (KERN_ALERT) action must be taken immediately
1157 2 (KERN_CRIT) critical conditions
1158 3 (KERN_ERR) error conditions
1159 4 (KERN_WARNING) warning conditions
1160 5 (KERN_NOTICE) normal but significant condition
1161 6 (KERN_INFO) informational
1162 7 (KERN_DEBUG) debug-level messages
1164 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1165 Format: { n | nk | nM }
1166 n must be a power of two. The default size
1167 is set in the kernel config file.
1169 logo.nologo [FB] Disables display of the built-in Linux logo.
1170 This may be used to provide more screen space for
1171 kernel log messages and is useful when debugging
1172 kernel boot problems.
1174 lp=0 [LP] Specify parallel ports to use, e.g,
1175 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1176 lp=reset first parallel port). 'lp=0' disables the
1177 lp=auto printer driver. 'lp=reset' (which can be
1178 specified in addition to the ports) causes
1179 attached printers to be reset. Using
1180 lp=port1,port2,... specifies the parallel ports
1181 to associate lp devices with, starting with
1182 lp0. A port specification may be 'none' to skip
1183 that lp device, or a parport name such as
1184 'parport0'. Specifying 'lp=auto' instead of a
1185 port specification list means that device IDs
1186 from each port should be examined, to see if
1187 an IEEE 1284-compliant printer is attached; if
1188 so, the driver will manage that printer.
1189 See also header of drivers/char/lp.c.
1191 lpj=n [KNL]
1192 Sets loops_per_jiffy to given constant, thus avoiding
1193 time-consuming boot-time autodetection (up to 250 ms per
1194 CPU). 0 enables autodetection (default). To determine
1195 the correct value for your kernel, boot with normal
1196 autodetection and see what value is printed. Note that
1197 on SMP systems the preset will be applied to all CPUs,
1198 which is likely to cause problems if your CPUs need
1199 significantly divergent settings. An incorrect value
1200 will cause delays in the kernel to be wrong, leading to
1201 unpredictable I/O errors and other breakage. Although
1202 unlikely, in the extreme case this might damage your
1203 hardware.
1205 ltpc= [NET]
1206 Format: <io>,<irq>,<dma>
1208 mac5380= [HW,SCSI] Format:
1209 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1211 machvec= [IA64] Force the use of a particular machine-vector
1212 (machvec) in a generic kernel.
1213 Example: machvec=hpzx1_swiotlb
1215 max_loop= [LOOP] Maximum number of loopback devices that can
1216 be mounted
1217 Format: <1-256>
1219 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1220 should make use of. maxcpus=n : n >= 0 limits the
1221 kernel to using 'n' processors. n=0 is a special case,
1222 it is equivalent to "nosmp", which also disables
1223 the IO APIC.
1225 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than
1226 or equal to this physical address is ignored.
1228 max_luns= [SCSI] Maximum number of LUNs to probe.
1229 Should be between 1 and 2^32-1.
1231 max_report_luns=
1232 [SCSI] Maximum number of LUNs received.
1233 Should be between 1 and 16384.
1235 mcatest= [IA-64]
1237 mce [X86-32] Machine Check Exception
1239 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1241 md= [HW] RAID subsystems devices and level
1242 See Documentation/md.txt.
1244 mdacon= [MDA]
1245 Format: <first>,<last>
1246 Specifies range of consoles to be captured by the MDA.
1248 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1249 Amount of memory to be used when the kernel is not able
1250 to see the whole system memory or for test.
1251 [X86-32] Use together with memmap= to avoid physical
1252 address space collisions. Without memmap= PCI devices
1253 could be placed at addresses belonging to unused RAM.
1255 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1256 memory.
1258 memchunk=nn[KMG]
1259 [KNL,SH] Allow user to override the default size for
1260 per-device physically contiguous DMA buffers.
1262 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1263 E820 memory map, as specified by the user.
1264 Such memmap=exactmap lines can be constructed based on
1265 BIOS output or other requirements. See the memmap=nn@ss
1266 option description.
1268 memmap=nn[KMG]@ss[KMG]
1269 [KNL] Force usage of a specific region of memory
1270 Region of memory to be used, from ss to ss+nn.
1272 memmap=nn[KMG]#ss[KMG]
1273 [KNL,ACPI] Mark specific memory as ACPI data.
1274 Region of memory to be used, from ss to ss+nn.
1276 memmap=nn[KMG]$ss[KMG]
1277 [KNL,ACPI] Mark specific memory as reserved.
1278 Region of memory to be used, from ss to ss+nn.
1279 Example: Exclude memory from 0x18690000-0x1869ffff
1280 memmap=64K$0x18690000
1281 or
1282 memmap=0x10000$0x18690000
1284 memory_corruption_check=0/1 [X86]
1285 Some BIOSes seem to corrupt the first 64k of
1286 memory when doing things like suspend/resume.
1287 Setting this option will scan the memory
1288 looking for corruption. Enabling this will
1289 both detect corruption and prevent the kernel
1290 from using the memory being corrupted.
1291 However, its intended as a diagnostic tool; if
1292 repeatable BIOS-originated corruption always
1293 affects the same memory, you can use memmap=
1294 to prevent the kernel from using that memory.
1296 memory_corruption_check_size=size [X86]
1297 By default it checks for corruption in the low
1298 64k, making this memory unavailable for normal
1299 use. Use this parameter to scan for
1300 corruption in more or less memory.
1302 memory_corruption_check_period=seconds [X86]
1303 By default it checks for corruption every 60
1304 seconds. Use this parameter to check at some
1305 other rate. 0 disables periodic checking.
1307 memtest= [KNL,X86] Enable memtest
1308 Format: <integer>
1309 range: 0,4 : pattern number
1310 default : 0 <disable>
1312 meye.*= [HW] Set MotionEye Camera parameters
1313 See Documentation/video4linux/meye.txt.
1315 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1316 Multi-Function General Purpose Timers on AMD Geode
1317 platforms.
1319 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1320 the BIOS has incorrectly applied a workaround. TinyBIOS
1321 version 0.98 is known to be affected, 0.99 fixes the
1322 problem by letting the user disable the workaround.
1324 mga= [HW,DRM]
1326 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1327 physical address is ignored.
1329 mminit_loglevel=
1330 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1331 parameter allows control of the logging verbosity for
1332 the additional memory initialisation checks. A value
1333 of 0 disables mminit logging and a level of 4 will
1334 log everything. Information is printed at KERN_DEBUG
1335 so loglevel=8 may also need to be specified.
1337 mousedev.tap_time=
1338 [MOUSE] Maximum time between finger touching and
1339 leaving touchpad surface for touch to be considered
1340 a tap and be reported as a left button click (for
1341 touchpads working in absolute mode only).
1342 Format: <msecs>
1343 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1344 reporting absolute coordinates, such as tablets
1345 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1346 reporting absolute coordinates, such as tablets
1348 mpu401= [HW,OSS]
1349 Format: <io>,<irq>
1351 MTD_Partition= [MTD]
1352 Format: <name>,<region-number>,<size>,<offset>
1354 MTD_Region= [MTD] Format:
1355 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1357 mtdparts= [MTD]
1358 See drivers/mtd/cmdlinepart.c.
1360 mtdset= [ARM]
1361 ARM/S3C2412 JIVE boot control
1363 See arch/arm/mach-s3c2412/mach-jive.c
1365 mtouchusb.raw_coordinates=
1366 [HW] Make the MicroTouch USB driver use raw coordinates
1367 ('y', default) or cooked coordinates ('n')
1369 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1371 NCR_D700= [HW,SCSI]
1372 See header of drivers/scsi/NCR_D700.c.
1374 ncr5380= [HW,SCSI]
1376 ncr53c400= [HW,SCSI]
1378 ncr53c400a= [HW,SCSI]
1380 ncr53c406a= [HW,SCSI]
1382 ncr53c8xx= [HW,SCSI]
1384 netdev= [NET] Network devices parameters
1385 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1386 Note that mem_start is often overloaded to mean
1387 something different and driver-specific.
1388 This usage is only documented in each driver source
1389 file if at all.
1391 nf_conntrack.acct=
1392 [NETFILTER] Enable connection tracking flow accounting
1393 0 to disable accounting
1394 1 to enable accounting
1395 Default value depends on CONFIG_NF_CT_ACCT that is
1396 going to be removed in 2.6.29.
1398 nfsaddrs= [NFS]
1399 See Documentation/filesystems/nfsroot.txt.
1401 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1402 See Documentation/filesystems/nfsroot.txt.
1404 nfs.callback_tcpport=
1405 [NFS] set the TCP port on which the NFSv4 callback
1406 channel should listen.
1408 nfs.idmap_cache_timeout=
1409 [NFS] set the maximum lifetime for idmapper cache
1410 entries.
1412 nfs.enable_ino64=
1413 [NFS] enable 64-bit inode numbers.
1414 If zero, the NFS client will fake up a 32-bit inode
1415 number for the readdir() and stat() syscalls instead
1416 of returning the full 64-bit number.
1417 The default is to return 64-bit inode numbers.
1419 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1420 when a NMI is triggered.
1421 Format: [state][,regs][,debounce][,die]
1423 nmi_watchdog= [KNL,BUGS=X86-32,X86-64] Debugging features for SMP kernels
1424 Format: [panic,][num]
1425 Valid num: 0,1,2
1426 0 - turn nmi_watchdog off
1427 1 - use the IO-APIC timer for the NMI watchdog
1428 2 - use the local APIC for the NMI watchdog using
1429 a performance counter. Note: This will use one performance
1430 counter and the local APIC's performance vector.
1431 When panic is specified panic when an NMI watchdog timeout occurs.
1432 This is useful when you use a panic=... timeout and need the box
1433 quickly up again.
1434 Instead of 1 and 2 it is possible to use the following
1435 symbolic names: lapic and ioapic
1436 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1438 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1439 emulation library even if a 387 maths coprocessor
1440 is present.
1442 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1443 caches in the slab allocator. Saves per-node memory,
1444 but will impact performance.
1446 noalign [KNL,ARM]
1448 noapic [SMP,APIC] Tells the kernel to not make use of any
1449 IOAPICs that may be present in the system.
1451 nobats [PPC] Do not use BATs for mapping kernel lowmem
1452 on "Classic" PPC cores.
1454 nocache [ARM]
1456 nodelayacct [KNL] Disable per-task delay accounting
1458 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1460 nodsp [SH] Disable hardware DSP at boot time.
1462 noefi [X86-32,X86-64] Disable EFI runtime services support.
1464 noexec [IA-64]
1466 noexec [X86-32,X86-64]
1467 On X86-32 available only on PAE configured kernels.
1468 noexec=on: enable non-executable mappings (default)
1469 noexec=off: disable non-executable mappings
1471 noexec32 [X86-64]
1472 This affects only 32-bit executables.
1473 noexec32=on: enable non-executable mappings (default)
1474 read doesn't imply executable mappings
1475 noexec32=off: disable non-executable mappings
1476 read implies executable mappings
1478 nofpu [SH] Disable hardware FPU at boot time.
1480 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1481 register save and restore. The kernel will only save
1482 legacy floating-point registers on task switch.
1484 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1486 nohlt [BUGS=ARM,SH]
1488 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1489 instruction doesn't work correctly and not to
1490 use it.
1492 no_file_caps Tells the kernel not to honor file capabilities. The
1493 only way then for a file to be executed with privilege
1494 is to be setuid root or executed by root.
1496 nohalt [IA-64] Tells the kernel not to use the power saving
1497 function PAL_HALT_LIGHT when idle. This increases
1498 power-consumption. On the positive side, it reduces
1499 interrupt wake-up latency, which may improve performance
1500 in certain environments such as networked servers or
1501 real-time systems.
1503 nohz= [KNL] Boottime enable/disable dynamic ticks
1504 Valid arguments: on, off
1505 Default: on
1507 noirqdebug [X86-32] Disables the code which attempts to detect and
1508 disable unhandled interrupt sources.
1510 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1511 broken timer IRQ sources.
1513 noisapnp [ISAPNP] Disables ISA PnP code.
1515 noinitrd [RAM] Tells the kernel not to load any configured
1516 initial RAM disk.
1518 nointroute [IA-64]
1520 nojitter [IA64] Disables jitter checking for ITC timers.
1522 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1524 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1526 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1528 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
1529 default x2apic cluster mode on platforms
1530 supporting x2apic.
1532 noltlbs [PPC] Do not use large page/tlb entries for kernel
1533 lowmem mapping on PPC40x.
1535 nomca [IA-64] Disable machine check abort handling
1537 nomce [X86-32] Machine Check Exception
1539 nomfgpt [X86-32] Disable Multi-Function General Purpose
1540 Timer usage (for AMD Geode machines).
1542 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1544 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1545 with UP alternatives
1547 noresidual [PPC] Don't use residual data on PReP machines.
1549 noresume [SWSUSP] Disables resume and restores original swap
1550 space.
1552 no-scroll [VGA] Disables scrollback.
1553 This is required for the Braillex ib80-piezo Braille
1554 reader made by F.H. Papenmeier (Germany).
1556 nosbagart [IA-64]
1558 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1560 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1561 and disable the IO APIC. legacy for "maxcpus=0".
1563 nosoftlockup [KNL] Disable the soft-lockup detector.
1565 noswapaccount [KNL] Disable accounting of swap in memory resource
1566 controller. (See Documentation/controllers/memory.txt)
1568 nosync [HW,M68K] Disables sync negotiation for all devices.
1570 notsc [BUGS=X86-32] Disable Time Stamp Counter
1572 nousb [USB] Disable the USB subsystem
1574 nowb [ARM]
1576 nptcg= [IA64] Override max number of concurrent global TLB
1577 purges which is reported from either PAL_VM_SUMMARY or
1578 SAL PALO.
1580 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1581 one of ['zone', 'node', 'default'] can be specified
1582 This can be set from sysctl after boot.
1583 See Documentation/sysctl/vm.txt for details.
1585 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1587 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1588 See Documentation/debugging-via-ohci1394.txt for more
1589 info.
1591 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1592 Rather than timing out after 20 ms if an EC
1593 command is not properly ACKed, override the length
1594 of the timeout. We have interrupts disabled while
1595 waiting for the ACK, so if this is set too high
1596 interrupts *may* be lost!
1598 opl3= [HW,OSS]
1599 Format: <io>
1601 oprofile.timer= [HW]
1602 Use timer interrupt instead of performance counters
1604 osst= [HW,SCSI] SCSI Tape Driver
1605 Format: <buffer_size>,<write_threshold>
1606 See also Documentation/scsi/st.txt.
1608 panic= [KNL] Kernel behaviour on panic
1609 Format: <timeout>
1611 parkbd.port= [HW] Parallel port number the keyboard adapter is
1612 connected to, default is 0.
1613 Format: <parport#>
1614 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1615 0 for XT, 1 for AT (default is AT).
1616 Format: <mode>
1618 parport= [HW,PPT] Specify parallel ports. 0 disables.
1619 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1620 Use 'auto' to force the driver to use any
1621 IRQ/DMA settings detected (the default is to
1622 ignore detected IRQ/DMA settings because of
1623 possible conflicts). You can specify the base
1624 address, IRQ, and DMA settings; IRQ and DMA
1625 should be numbers, or 'auto' (for using detected
1626 settings on that particular port), or 'nofifo'
1627 (to avoid using a FIFO even if it is detected).
1628 Parallel ports are assigned in the order they
1629 are specified on the command line, starting
1630 with parport0.
1632 parport_init_mode= [HW,PPT]
1633 Configure VIA parallel port to operate in
1634 a specific mode. This is necessary on Pegasos
1635 computer where firmware has no options for setting
1636 up parallel port mode and sets it to spp.
1637 Currently this function knows 686a and 8231 chips.
1638 Format: [spp|ps2|epp|ecp|ecpepp]
1640 pas2= [HW,OSS] Format:
1641 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1643 pas16= [HW,SCSI]
1644 See header of drivers/scsi/pas16.c.
1646 pause_on_oops=
1647 Halt all CPUs after the first oops has been printed for
1648 the specified number of seconds. This is to be used if
1649 your oopses keep scrolling off the screen.
1651 pcbit= [HW,ISDN]
1653 pcd. [PARIDE]
1654 See header of drivers/block/paride/pcd.c.
1655 See also Documentation/blockdev/paride.txt.
1657 pci=option[,option...] [PCI] various PCI subsystem options:
1658 off [X86] don't probe for the PCI bus
1659 bios [X86-32] force use of PCI BIOS, don't access
1660 the hardware directly. Use this if your machine
1661 has a non-standard PCI host bridge.
1662 nobios [X86-32] disallow use of PCI BIOS, only direct
1663 hardware access methods are allowed. Use this
1664 if you experience crashes upon bootup and you
1665 suspect they are caused by the BIOS.
1666 conf1 [X86] Force use of PCI Configuration
1667 Mechanism 1.
1668 conf2 [X86] Force use of PCI Configuration
1669 Mechanism 2.
1670 noaer [PCIE] If the PCIEAER kernel config parameter is
1671 enabled, this kernel boot option can be used to
1672 disable the use of PCIE advanced error reporting.
1673 nodomains [PCI] Disable support for multiple PCI
1674 root domains (aka PCI segments, in ACPI-speak).
1675 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1676 Configuration
1677 nomsi [MSI] If the PCI_MSI kernel config parameter is
1678 enabled, this kernel boot option can be used to
1679 disable the use of MSI interrupts system-wide.
1680 noioapicquirk [APIC] Disable all boot interrupt quirks.
1681 Safety option to keep boot IRQs enabled. This
1682 should never be necessary.
1683 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1684 primary IO-APIC for bridges that cannot disable
1685 boot IRQs. This fixes a source of spurious IRQs
1686 when the system masks IRQs.
1687 noioapicreroute [APIC] Disable workaround that uses the
1688 boot IRQ equivalent of an IRQ that connects to
1689 a chipset where boot IRQs cannot be disabled.
1690 The opposite of ioapicreroute.
1691 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1692 routing table. These calls are known to be buggy
1693 on several machines and they hang the machine
1694 when used, but on other computers it's the only
1695 way to get the interrupt routing table. Try
1696 this option if the kernel is unable to allocate
1697 IRQs or discover secondary PCI buses on your
1698 motherboard.
1699 rom [X86] Assign address space to expansion ROMs.
1700 Use with caution as certain devices share
1701 address decoders between ROMs and other
1702 resources.
1703 norom [X86] Do not assign address space to
1704 expansion ROMs that do not already have
1705 BIOS assigned address ranges.
1706 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1707 assigned automatically to PCI devices. You can
1708 make the kernel exclude IRQs of your ISA cards
1709 this way.
1710 pirqaddr=0xAAAAA [X86] Specify the physical address
1711 of the PIRQ table (normally generated
1712 by the BIOS) if it is outside the
1713 F0000h-100000h range.
1714 lastbus=N [X86] Scan all buses thru bus #N. Can be
1715 useful if the kernel is unable to find your
1716 secondary buses and you want to tell it
1717 explicitly which ones they are.
1718 assign-busses [X86] Always assign all PCI bus
1719 numbers ourselves, overriding
1720 whatever the firmware may have done.
1721 usepirqmask [X86] Honor the possible IRQ mask stored
1722 in the BIOS $PIR table. This is needed on
1723 some systems with broken BIOSes, notably
1724 some HP Pavilion N5400 and Omnibook XE3
1725 notebooks. This will have no effect if ACPI
1726 IRQ routing is enabled.
1727 noacpi [X86] Do not use ACPI for IRQ routing
1728 or for PCI scanning.
1729 use_crs [X86] Use _CRS for PCI resource
1730 allocation.
1731 routeirq Do IRQ routing for all PCI devices.
1732 This is normally done in pci_enable_device(),
1733 so this option is a temporary workaround
1734 for broken drivers that don't call it.
1735 skip_isa_align [X86] do not align io start addr, so can
1736 handle more pci cards
1737 firmware [ARM] Do not re-enumerate the bus but instead
1738 just use the configuration from the
1739 bootloader. This is currently used on
1740 IXP2000 systems where the bus has to be
1741 configured a certain way for adjunct CPUs.
1742 noearly [X86] Don't do any early type 1 scanning.
1743 This might help on some broken boards which
1744 machine check when some devices' config space
1745 is read. But various workarounds are disabled
1746 and some IOMMU drivers will not work.
1747 bfsort Sort PCI devices into breadth-first order.
1748 This sorting is done to get a device
1749 order compatible with older (<= 2.4) kernels.
1750 nobfsort Don't sort PCI devices into breadth-first order.
1751 cbiosize=nn[KMG] The fixed amount of bus space which is
1752 reserved for the CardBus bridge's IO window.
1753 The default value is 256 bytes.
1754 cbmemsize=nn[KMG] The fixed amount of bus space which is
1755 reserved for the CardBus bridge's memory
1756 window. The default value is 64 megabytes.
1758 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1759 Management.
1760 off Disable ASPM.
1761 force Enable ASPM even on devices that claim not to support it.
1762 WARNING: Forcing ASPM on may cause system lockups.
1764 pcmv= [HW,PCMCIA] BadgePAD 4
1766 pd. [PARIDE]
1767 See Documentation/blockdev/paride.txt.
1769 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1770 boot time.
1771 Format: { 0 | 1 }
1772 See arch/parisc/kernel/pdc_chassis.c
1774 pf. [PARIDE]
1775 See Documentation/blockdev/paride.txt.
1777 pg. [PARIDE]
1778 See Documentation/blockdev/paride.txt.
1780 pirq= [SMP,APIC] Manual mp-table setup
1781 See Documentation/x86/i386/IO-APIC.txt.
1783 plip= [PPT,NET] Parallel port network link
1784 Format: { parport<nr> | timid | 0 }
1785 See also Documentation/parport.txt.
1787 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1788 Override pmtimer IOPort with a hex value.
1789 e.g. pmtmr=0x508
1791 pnp.debug [PNP]
1792 Enable PNP debug messages. This depends on the
1793 CONFIG_PNP_DEBUG_MESSAGES option.
1795 pnpacpi= [ACPI]
1796 { off }
1798 pnpbios= [ISAPNP]
1799 { on | off | curr | res | no-curr | no-res }
1801 pnp_reserve_irq=
1802 [ISAPNP] Exclude IRQs for the autoconfiguration
1804 pnp_reserve_dma=
1805 [ISAPNP] Exclude DMAs for the autoconfiguration
1807 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1808 Ranges are in pairs (I/O port base and size).
1810 pnp_reserve_mem=
1811 [ISAPNP] Exclude memory regions for the
1812 autoconfiguration.
1813 Ranges are in pairs (memory base and size).
1815 dynamic_printk Enables pr_debug()/dev_dbg() calls if
1816 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
1817 These can also be switched on/off via
1818 <debugfs>/dynamic_printk/modules
1820 print-fatal-signals=
1821 [KNL] debug: print fatal signals
1822 print-fatal-signals=1: print segfault info to
1823 the kernel console.
1824 default: off.
1826 printk.time= Show timing data prefixed to each printk message line
1827 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1829 profile= [KNL] Enable kernel profiling via /proc/profile
1830 Format: [schedule,]<number>
1831 Param: "schedule" - profile schedule points.
1832 Param: <number> - step/bucket size as a power of 2 for
1833 statistical time based profiling.
1834 Param: "sleep" - profile D-state sleeping (millisecs).
1835 Requires CONFIG_SCHEDSTATS
1836 Param: "kvm" - profile VM exits.
1838 processor.max_cstate= [HW,ACPI]
1839 Limit processor to maximum C-state
1840 max_cstate=9 overrides any DMI blacklist limit.
1842 processor.nocst [HW,ACPI]
1843 Ignore the _CST method to determine C-states,
1844 instead using the legacy FADT method
1846 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1847 before loading.
1848 See Documentation/blockdev/ramdisk.txt.
1850 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1851 probe for; one of (bare|imps|exps|lifebook|any).
1852 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1853 per second.
1854 psmouse.resetafter= [HW,MOUSE]
1855 Try to reset the device after so many bad packets
1856 (0 = never).
1857 psmouse.resolution=
1858 [HW,MOUSE] Set desired mouse resolution, in dpi.
1859 psmouse.smartscroll=
1860 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1861 0 = disabled, 1 = enabled (default).
1863 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1864 Format:
1865 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1867 pt. [PARIDE]
1868 See Documentation/blockdev/paride.txt.
1870 pty.legacy_count=
1871 [KNL] Number of legacy pty's. Overwrites compiled-in
1872 default number.
1874 quiet [KNL] Disable most log messages
1876 r128= [HW,DRM]
1878 raid= [HW,RAID]
1879 See Documentation/md.txt.
1881 ramdisk_blocksize= [RAM]
1882 See Documentation/blockdev/ramdisk.txt.
1884 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1885 See Documentation/blockdev/ramdisk.txt.
1887 rcupdate.blimit= [KNL,BOOT]
1888 Set maximum number of finished RCU callbacks to process
1889 in one batch.
1891 rcupdate.qhimark= [KNL,BOOT]
1892 Set threshold of queued
1893 RCU callbacks over which batch limiting is disabled.
1895 rcupdate.qlowmark= [KNL,BOOT]
1896 Set threshold of queued RCU callbacks below which
1897 batch limiting is re-enabled.
1899 rdinit= [KNL]
1900 Format: <full_path>
1901 Run specified binary instead of /init from the ramdisk,
1902 used for early userspace startup. See initrd.
1904 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1905 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1906 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1908 relax_domain_level=
1909 [KNL, SMP] Set scheduler's default relax_domain_level.
1910 See Documentation/cpusets.txt.
1912 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1914 reservetop= [X86-32]
1915 Format: nn[KMG]
1916 Reserves a hole at the top of the kernel virtual
1917 address space.
1919 reset_devices [KNL] Force drivers to reset the underlying device
1920 during initialization.
1922 resume= [SWSUSP]
1923 Specify the partition device for software suspend
1925 resume_offset= [SWSUSP]
1926 Specify the offset from the beginning of the partition
1927 given by "resume=" at which the swap header is located,
1928 in <PAGE_SIZE> units (needed only for swap files).
1929 See Documentation/power/swsusp-and-swap-files.txt
1931 retain_initrd [RAM] Keep initrd memory after extraction
1933 rhash_entries= [KNL,NET]
1934 Set number of hash buckets for route cache
1936 riscom8= [HW,SERIAL]
1937 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1939 ro [KNL] Mount root device read-only on boot
1941 root= [KNL] Root filesystem
1943 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1944 mount the root filesystem
1946 rootflags= [KNL] Set root filesystem mount option string
1948 rootfstype= [KNL] Set root filesystem type
1950 rootwait [KNL] Wait (indefinitely) for root device to show up.
1951 Useful for devices that are detected asynchronously
1952 (e.g. USB and MMC devices).
1954 root_plug.vendor_id=
1955 [ROOTPLUG] Override the default vendor ID
1957 root_plug.product_id=
1958 [ROOTPLUG] Override the default product ID
1960 root_plug.debug=
1961 [ROOTPLUG] Enable debugging output
1963 rw [KNL] Mount root device read-write on boot
1965 S [KNL] Run init in single mode
1967 sa1100ir [NET]
1968 See drivers/net/irda/sa1100_ir.c.
1970 sbni= [NET] Granch SBNI12 leased line adapter
1972 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1973 Format: <io>[,<timeout>[,<isapnp>]]
1975 scsi_debug_*= [SCSI]
1976 See drivers/scsi/scsi_debug.c.
1978 scsi_default_dev_flags=
1979 [SCSI] SCSI default device flags
1980 Format: <integer>
1982 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1983 Format: <vendor>:<model>:<flags>
1984 (flags are integer value)
1986 scsi_logging_level= [SCSI] a bit mask of logging levels
1987 See drivers/scsi/scsi_logging.h for bits. Also
1988 settable via sysctl at dev.scsi.logging_level
1989 (/proc/sys/dev/scsi/logging_level).
1990 There is also a nice 'scsi_logging_level' script in the
1991 S390-tools package, available for download at
1992 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1994 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1995 discovered. async scans them in kernel threads,
1996 allowing boot to proceed. none ignores them, expecting
1997 user space to do the scan.
1999 selinux [SELINUX] Disable or enable SELinux at boot time.
2000 Format: { "0" | "1" }
2001 See security/selinux/Kconfig help text.
2002 0 -- disable.
2003 1 -- enable.
2004 Default value is set via kernel config option.
2005 If enabled at boot time, /selinux/disable can be used
2006 later to disable prior to initial policy load.
2008 selinux_compat_net =
2009 [SELINUX] Set initial selinux_compat_net flag value.
2010 Format: { "0" | "1" }
2011 0 -- use new secmark-based packet controls
2012 1 -- use legacy packet controls
2013 Default value is 0 (preferred).
2014 Value can be changed at runtime via
2015 /selinux/compat_net.
2017 serialnumber [BUGS=X86-32]
2019 shapers= [NET]
2020 Maximal number of shapers.
2022 show_msr= [x86] show boot-time MSR settings
2023 Format: { <integer> }
2024 Show boot-time (BIOS-initialized) MSR settings.
2025 The parameter means the number of CPUs to show,
2026 for example 1 means boot CPU only.
2028 sim710= [SCSI,HW]
2029 See header of drivers/scsi/sim710.c.
2031 simeth= [IA-64]
2032 simscsi=
2034 slram= [HW,MTD]
2036 slub_debug[=options[,slabs]] [MM, SLUB]
2037 Enabling slub_debug allows one to determine the
2038 culprit if slab objects become corrupted. Enabling
2039 slub_debug can create guard zones around objects and
2040 may poison objects when not in use. Also tracks the
2041 last alloc / free. For more information see
2042 Documentation/vm/slub.txt.
2044 slub_max_order= [MM, SLUB]
2045 Determines the maximum allowed order for slabs.
2046 A high setting may cause OOMs due to memory
2047 fragmentation. For more information see
2048 Documentation/vm/slub.txt.
2050 slub_min_objects= [MM, SLUB]
2051 The minimum number of objects per slab. SLUB will
2052 increase the slab order up to slub_max_order to
2053 generate a sufficiently large slab able to contain
2054 the number of objects indicated. The higher the number
2055 of objects the smaller the overhead of tracking slabs
2056 and the less frequently locks need to be acquired.
2057 For more information see Documentation/vm/slub.txt.
2059 slub_min_order= [MM, SLUB]
2060 Determines the mininum page order for slabs. Must be
2061 lower than slub_max_order.
2062 For more information see Documentation/vm/slub.txt.
2064 slub_nomerge [MM, SLUB]
2065 Disable merging of slabs with similar size. May be
2066 necessary if there is some reason to distinguish
2067 allocs to different slabs. Debug options disable
2068 merging on their own.
2069 For more information see Documentation/vm/slub.txt.
2071 smart2= [HW]
2072 Format: <io1>[,<io2>[,...,<io8>]]
2074 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2075 attempt to substitute SMP alternatives once at boot.
2077 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2078 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2079 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2080 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2081 smsc-ircc2.ircc_irq= [HW] IRQ line
2082 smsc-ircc2.ircc_dma= [HW] DMA channel
2083 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2084 0: Toshiba Satellite 1800 (GP data pin select)
2085 1: Fast pin select (default)
2086 2: ATC IRMode
2088 snd-ad1816a= [HW,ALSA]
2090 snd-ad1848= [HW,ALSA]
2092 snd-ali5451= [HW,ALSA]
2094 snd-als100= [HW,ALSA]
2096 snd-als4000= [HW,ALSA]
2098 snd-azt2320= [HW,ALSA]
2100 snd-cmi8330= [HW,ALSA]
2102 snd-cmipci= [HW,ALSA]
2104 snd-cs4231= [HW,ALSA]
2106 snd-cs4232= [HW,ALSA]
2108 snd-cs4236= [HW,ALSA]
2110 snd-cs4281= [HW,ALSA]
2112 snd-cs46xx= [HW,ALSA]
2114 snd-dt019x= [HW,ALSA]
2116 snd-dummy= [HW,ALSA]
2118 snd-emu10k1= [HW,ALSA]
2120 snd-ens1370= [HW,ALSA]
2122 snd-ens1371= [HW,ALSA]
2124 snd-es968= [HW,ALSA]
2126 snd-es1688= [HW,ALSA]
2128 snd-es18xx= [HW,ALSA]
2130 snd-es1938= [HW,ALSA]
2132 snd-es1968= [HW,ALSA]
2134 snd-fm801= [HW,ALSA]
2136 snd-gusclassic= [HW,ALSA]
2138 snd-gusextreme= [HW,ALSA]
2140 snd-gusmax= [HW,ALSA]
2142 snd-hdsp= [HW,ALSA]
2144 snd-ice1712= [HW,ALSA]
2146 snd-intel8x0= [HW,ALSA]
2148 snd-interwave= [HW,ALSA]
2150 snd-interwave-stb=
2151 [HW,ALSA]
2153 snd-korg1212= [HW,ALSA]
2155 snd-maestro3= [HW,ALSA]
2157 snd-mpu401= [HW,ALSA]
2159 snd-mtpav= [HW,ALSA]
2161 snd-nm256= [HW,ALSA]
2163 snd-opl3sa2= [HW,ALSA]
2165 snd-opti92x-ad1848=
2166 [HW,ALSA]
2168 snd-opti92x-cs4231=
2169 [HW,ALSA]
2171 snd-opti93x= [HW,ALSA]
2173 snd-pmac= [HW,ALSA]
2175 snd-rme32= [HW,ALSA]
2177 snd-rme96= [HW,ALSA]
2179 snd-rme9652= [HW,ALSA]
2181 snd-sb8= [HW,ALSA]
2183 snd-sb16= [HW,ALSA]
2185 snd-sbawe= [HW,ALSA]
2187 snd-serial= [HW,ALSA]
2189 snd-sgalaxy= [HW,ALSA]
2191 snd-sonicvibes= [HW,ALSA]
2193 snd-sun-amd7930=
2194 [HW,ALSA]
2196 snd-sun-cs4231= [HW,ALSA]
2198 snd-trident= [HW,ALSA]
2200 snd-usb-audio= [HW,ALSA,USB]
2202 snd-via82xx= [HW,ALSA]
2204 snd-virmidi= [HW,ALSA]
2206 snd-wavefront= [HW,ALSA]
2208 snd-ymfpci= [HW,ALSA]
2210 softlockup_panic=
2211 [KNL] Should the soft-lockup detector generate panics.
2213 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2214 See Documentation/sonypi.txt
2216 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2217 See Documentation/serial/specialix.txt.
2219 spia_io_base= [HW,MTD]
2220 spia_fio_base=
2221 spia_pedr=
2222 spia_peddr=
2224 sscape= [HW,OSS]
2225 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2227 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2228 See Documentation/scsi/st.txt.
2230 stacktrace [FTRACE]
2231 Enabled the stack tracer on boot up.
2233 sti= [PARISC,HW]
2234 Format: <num>
2235 Set the STI (builtin display/keyboard on the HP-PARISC
2236 machines) console (graphic card) which should be used
2237 as the initial boot-console.
2238 See also comment in drivers/video/console/sticore.c.
2240 sti_font= [HW]
2241 See comment in drivers/video/console/sticore.c.
2243 stifb= [HW]
2244 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2246 sunrpc.pool_mode=
2247 [NFS]
2248 Control how the NFS server code allocates CPUs to
2249 service thread pools. Depending on how many NICs
2250 you have and where their interrupts are bound, this
2251 option will affect which CPUs will do NFS serving.
2252 Note: this parameter cannot be changed while the
2253 NFS server is running.
2255 auto the server chooses an appropriate mode
2256 automatically using heuristics
2257 global a single global pool contains all CPUs
2258 percpu one pool for each CPU
2259 pernode one pool for each NUMA node (equivalent
2260 to global on non-NUMA machines)
2262 swiotlb= [IA-64] Number of I/O TLB slabs
2264 switches= [HW,M68k]
2266 sym53c416= [HW,SCSI]
2267 See header of drivers/scsi/sym53c416.c.
2269 sysrq_always_enabled
2270 [KNL]
2271 Ignore sysrq setting - this boot parameter will
2272 neutralize any effect of /proc/sys/kernel/sysrq.
2273 Useful for debugging.
2275 t128= [HW,SCSI]
2276 See header of drivers/scsi/t128.c.
2278 tdfx= [HW,DRM]
2280 test_suspend= [SUSPEND]
2281 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2282 standby suspend) as the system sleep state to briefly
2283 enter during system startup. The system is woken from
2284 this state using a wakeup-capable RTC alarm.
2286 thash_entries= [KNL,NET]
2287 Set number of hash buckets for TCP connection
2289 thermal.act= [HW,ACPI]
2290 -1: disable all active trip points in all thermal zones
2291 <degrees C>: override all lowest active trip points
2293 thermal.crt= [HW,ACPI]
2294 -1: disable all critical trip points in all thermal zones
2295 <degrees C>: override all critical trip points
2297 thermal.nocrt= [HW,ACPI]
2298 Set to disable actions on ACPI thermal zone
2299 critical and hot trip points.
2301 thermal.off= [HW,ACPI]
2302 1: disable ACPI thermal control
2304 thermal.psv= [HW,ACPI]
2305 -1: disable all passive trip points
2306 <degrees C>: override all passive trip points to this
2307 value
2309 thermal.tzp= [HW,ACPI]
2310 Specify global default ACPI thermal zone polling rate
2311 <deci-seconds>: poll all this frequency
2312 0: no polling (default)
2314 tmscsim= [HW,SCSI]
2315 See comment before function dc390_setup() in
2316 drivers/scsi/tmscsim.c.
2318 topology= [S390]
2319 Format: {off | on}
2320 Specify if the kernel should make use of the cpu
2321 topology informations if the hardware supports these.
2322 The scheduler will make use of these informations and
2323 e.g. base its process migration decisions on it.
2324 Default is off.
2326 tp720= [HW,PS2]
2328 trix= [HW,OSS] MediaTrix AudioTrix Pro
2329 Format:
2330 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2332 tsc= Disable clocksource-must-verify flag for TSC.
2333 Format: <string>
2334 [x86] reliable: mark tsc clocksource as reliable, this
2335 disables clocksource verification at runtime.
2336 Used to enable high-resolution timer mode on older
2337 hardware, and in virtualized environment.
2339 turbografx.map[2|3]= [HW,JOY]
2340 TurboGraFX parallel port interface
2341 Format:
2342 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2343 See also Documentation/input/joystick-parport.txt
2345 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2346 See header of drivers/scsi/u14-34f.c.
2348 uart401= [HW,OSS]
2349 Format: <io>,<irq>
2351 uart6850= [HW,OSS]
2352 Format: <io>,<irq>
2354 uhci-hcd.ignore_oc=
2355 [USB] Ignore overcurrent events (default N).
2356 Some badly-designed motherboards generate lots of
2357 bogus events, for ports that aren't wired to
2358 anything. Set this parameter to avoid log spamming.
2359 Note that genuine overcurrent events won't be
2360 reported either.
2362 unknown_nmi_panic
2363 [X86-32,X86-64]
2364 Set unknown_nmi_panic=1 early on boot.
2366 usbcore.autosuspend=
2367 [USB] The autosuspend time delay (in seconds) used
2368 for newly-detected USB devices (default 2). This
2369 is the time required before an idle device will be
2370 autosuspended. Devices for which the delay is set
2371 to a negative value won't be autosuspended at all.
2373 usbcore.usbfs_snoop=
2374 [USB] Set to log all usbfs traffic (default 0 = off).
2376 usbcore.blinkenlights=
2377 [USB] Set to cycle leds on hubs (default 0 = off).
2379 usbcore.old_scheme_first=
2380 [USB] Start with the old device initialization
2381 scheme (default 0 = off).
2383 usbcore.use_both_schemes=
2384 [USB] Try the other device initialization scheme
2385 if the first one fails (default 1 = enabled).
2387 usbcore.initial_descriptor_timeout=
2388 [USB] Specifies timeout for the initial 64-byte
2389 USB_REQ_GET_DESCRIPTOR request in milliseconds
2390 (default 5000 = 5.0 seconds).
2392 usbhid.mousepoll=
2393 [USBHID] The interval which mice are to be polled at.
2395 usb-storage.delay_use=
2396 [UMS] The delay in seconds before a new device is
2397 scanned for Logical Units (default 5).
2399 usb-storage.quirks=
2400 [UMS] A list of quirks entries to supplement or
2401 override the built-in unusual_devs list. List
2402 entries are separated by commas. Each entry has
2403 the form VID:PID:Flags where VID and PID are Vendor
2404 and Product ID values (4-digit hex numbers) and
2405 Flags is a set of characters, each corresponding
2406 to a common usb-storage quirk flag as follows:
2407 a = SANE_SENSE (collect more than 18 bytes
2408 of sense data);
2409 c = FIX_CAPACITY (decrease the reported
2410 device capacity by one sector);
2411 h = CAPACITY_HEURISTICS (decrease the
2412 reported device capacity by one
2413 sector if the number is odd);
2414 i = IGNORE_DEVICE (don't bind to this
2415 device);
2416 l = NOT_LOCKABLE (don't try to lock and
2417 unlock ejectable media);
2418 m = MAX_SECTORS_64 (don't transfer more
2419 than 64 sectors = 32 KB at a time);
2420 o = CAPACITY_OK (accept the capacity
2421 reported by the device);
2422 r = IGNORE_RESIDUE (the device reports
2423 bogus residue values);
2424 s = SINGLE_LUN (the device has only one
2425 Logical Unit);
2426 w = NO_WP_DETECT (don't test whether the
2427 medium is write-protected).
2428 Example: quirks=0419:aaf5:rl,0421:0433:rc
2430 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2431 kernel's map of available physical RAM.
2433 vdso= [X86-32,SH,x86-64]
2434 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2435 vdso=1: enable VDSO (default)
2436 vdso=0: disable VDSO mapping
2438 vdso32= [X86-32,X86-64]
2439 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2440 vdso32=1: enable 32-bit VDSO (default)
2441 vdso32=0: disable 32-bit VDSO mapping
2443 vector= [IA-64,SMP]
2444 vector=percpu: enable percpu vector domain
2446 video= [FB] Frame buffer configuration
2447 See Documentation/fb/modedb.txt.
2449 vga= [BOOT,X86-32] Select a particular video mode
2450 See Documentation/x86/i386/boot.txt and
2451 Documentation/svga.txt.
2452 Use vga=ask for menu.
2453 This is actually a boot loader parameter; the value is
2454 passed to the kernel using a special protocol.
2456 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2457 size of <nn>. This can be used to increase the
2458 minimum size (128MB on x86). It can also be used to
2459 decrease the size and leave more room for directly
2460 mapped kernel RAM.
2462 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2463 Format: <command>
2465 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2466 Format: <command>
2468 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2469 Format: <command>
2471 waveartist= [HW,OSS]
2472 Format: <io>,<irq>,<dma>,<dma2>
2474 wd33c93= [HW,SCSI]
2475 See header of drivers/scsi/wd33c93.c.
2477 wd7000= [HW,SCSI]
2478 See header of drivers/scsi/wd7000.c.
2480 wdt= [WDT] Watchdog
2481 See Documentation/watchdog/wdt.txt.
2483 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2484 xd_geo= See header of drivers/block/xd.c.
2486 xirc2ps_cs= [NET,PCMCIA]
2487 Format:
2488 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2490 norandmaps Don't use address space randomization. Equivalent to
2491 echo 0 > /proc/sys/kernel/randomize_va_space
2493 ______________________________________________________________________
2495 TODO:
2497 Add documentation for ALSA options.
2498 Add more DRM drivers.