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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 USB USB support is enabled.
95 USBHID USB Human Interface Device support is enabled.
96 V4L Video For Linux support is enabled.
97 VGA The VGA console has been enabled.
98 VT Virtual terminal support is enabled.
99 WDT Watchdog support is enabled.
100 XT IBM PC/XT MFM hard disk support is enabled.
101 X86-32 X86-32, aka i386 architecture is enabled.
102 X86-64 X86-64 architecture is enabled.
103 More X86-64 boot options can be found in
104 Documentation/x86/x86_64/boot-options.txt .
105 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
107 In addition, the following text indicates that the option:
109 BUGS= Relates to possible processor bugs on the said processor.
110 KNL Is a kernel start-up parameter.
111 BOOT Is a boot loader parameter.
113 Parameters denoted with BOOT are actually interpreted by the boot
114 loader, and have no meaning to the kernel directly.
115 Do not modify the syntax of boot loader parameters without extreme
116 need or coordination with <Documentation/x86/i386/boot.txt>.
118 There are also arch-specific kernel-parameters not documented here.
119 See for example <Documentation/x86/x86_64/boot-options.txt>.
121 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
122 a trailing = on the name of any parameter states that that parameter will
123 be entered as an environment variable, whereas its absence indicates that
124 it will appear as a kernel argument readable via /proc/cmdline by programs
125 running once the system is up.
127 The number of kernel parameters is not limited, but the length of the
128 complete command line (parameters including spaces etc.) is limited to
129 a fixed number of characters. This limit depends on the architecture
130 and is between 256 and 4096 characters. It is defined in the file
131 ./include/asm/setup.h as COMMAND_LINE_SIZE.
134 acpi= [HW,ACPI,X86-64,i386]
135 Advanced Configuration and Power Interface
136 Format: { force | off | ht | strict | noirq }
137 force -- enable ACPI if default was off
138 off -- disable ACPI if default was on
139 noirq -- do not use ACPI for IRQ routing
140 ht -- run only enough ACPI to enable Hyper Threading
141 strict -- Be less tolerant of platforms that are not
142 strictly ACPI specification compliant.
144 See also Documentation/power/pm.txt, pci=noacpi
146 acpi_apic_instance= [ACPI, IOAPIC]
147 Format: <int>
148 2: use 2nd APIC table, if available
149 1,0: use 1st APIC table
150 default: 0
152 acpi_sleep= [HW,ACPI] Sleep options
153 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig, old_ordering }
154 See Documentation/power/video.txt for s3_bios and s3_mode.
155 s3_beep is for debugging; it makes the PC's speaker beep
156 as soon as the kernel's real-mode entry point is called.
157 s4_nohwsig prevents ACPI hardware signature from being
158 used during resume from hibernation.
159 old_ordering causes the ACPI 1.0 ordering of the _PTS
160 control method, wrt putting devices into low power
161 states, to be enforced (the ACPI 2.0 ordering of _PTS is
162 used by default).
164 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
165 Format: { level | edge | high | low }
167 acpi_irq_balance [HW,ACPI]
168 ACPI will balance active IRQs
169 default in APIC mode
171 acpi_irq_nobalance [HW,ACPI]
172 ACPI will not move active IRQs (default)
173 default in PIC mode
175 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
176 use by PCI
177 Format: <irq>,<irq>...
179 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
180 Format: <irq>,<irq>...
182 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
184 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
185 Format: To spoof as Windows 98: ="Microsoft Windows"
187 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
188 acpi_osi="string1" # add string1 -- only one string
189 acpi_osi="!string2" # remove built-in string2
190 acpi_osi= # disable all strings
192 acpi_serialize [HW,ACPI] force serialization of AML methods
194 acpi_skip_timer_override [HW,ACPI]
195 Recognize and ignore IRQ0/pin2 Interrupt Override.
196 For broken nForce2 BIOS resulting in XT-PIC timer.
197 acpi_use_timer_override [HW,ACPI}
198 Use timer override. For some broken Nvidia NF5 boards
199 that require a timer override, but don't have
200 HPET
202 acpi_backlight= [HW,ACPI]
203 acpi_backlight=vendor
204 acpi_backlight=video
205 If set to vendor, prefer vendor specific driver
206 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
207 of the ACPI video.ko driver.
209 acpi_display_output= [HW,ACPI]
210 acpi_display_output=vendor
211 acpi_display_output=video
212 See above.
214 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
215 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
216 Format: <int>
217 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
218 debug output. Bits in debug_layer correspond to a
219 _COMPONENT in an ACPI source file, e.g.,
220 #define _COMPONENT ACPI_PCI_COMPONENT
221 Bits in debug_level correspond to a level in
222 ACPI_DEBUG_PRINT statements, e.g.,
223 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
224 The debug_level mask defaults to "info". See
225 Documentation/acpi/debug.txt for more information about
226 debug layers and levels.
228 Enable processor driver info messages:
229 acpi.debug_layer=0x20000000
230 Enable PCI/PCI interrupt routing info messages:
231 acpi.debug_layer=0x400000
232 Enable AML "Debug" output, i.e., stores to the Debug
233 object while interpreting AML:
234 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
235 Enable all messages related to ACPI hardware:
236 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
238 Some values produce so much output that the system is
239 unusable. The "log_buf_len" parameter may be useful
240 if you need to capture more output.
242 acpi.power_nocheck= [HW,ACPI]
243 Format: 1/0 enable/disable the check of power state.
244 On some bogus BIOS the _PSC object/_STA object of
245 power resource can't return the correct device power
246 state. In such case it is unneccessary to check its
247 power state again in power transition.
248 1 : disable the power state check
250 acpi_pm_good [X86-32,X86-64]
251 Override the pmtimer bug detection: force the kernel
252 to assume that this machine's pmtimer latches its value
253 and always returns good values.
255 agp= [AGP]
256 { off | try_unsupported }
257 off: disable AGP support
258 try_unsupported: try to drive unsupported chipsets
259 (may crash computer or cause data corruption)
261 enable_timer_pin_1 [i386,x86-64]
262 Enable PIN 1 of APIC timer
263 Can be useful to work around chipset bugs
264 (in particular on some ATI chipsets).
265 The kernel tries to set a reasonable default.
267 disable_timer_pin_1 [i386,x86-64]
268 Disable PIN 1 of APIC timer
269 Can be useful to work around chipset bugs.
271 ad1848= [HW,OSS]
272 Format: <io>,<irq>,<dma>,<dma2>,<type>
274 advansys= [HW,SCSI]
275 See header of drivers/scsi/advansys.c.
277 advwdt= [HW,WDT] Advantech WDT
278 Format: <iostart>,<iostop>
280 aedsp16= [HW,OSS] Audio Excel DSP 16
281 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
282 See also header of sound/oss/aedsp16.c.
284 aha152x= [HW,SCSI]
285 See Documentation/scsi/aha152x.txt.
287 aha1542= [HW,SCSI]
288 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
290 aic7xxx= [HW,SCSI]
291 See Documentation/scsi/aic7xxx.txt.
293 aic79xx= [HW,SCSI]
294 See Documentation/scsi/aic79xx.txt.
296 amd_iommu= [HW,X86-84]
297 Pass parameters to the AMD IOMMU driver in the system.
298 Possible values are:
299 isolate - enable device isolation (each device, as far
300 as possible, will get its own protection
301 domain) [default]
302 share - put every device behind one IOMMU into the
303 same protection domain
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
309 amd_iommu_size= [HW,X86-64]
310 Define the size of the aperture for the AMD IOMMU
311 driver. Possible values are:
312 '32M', '64M' (default), '128M', '256M', '512M', '1G'
314 amijoy.map= [HW,JOY] Amiga joystick support
315 Map of devices attached to JOY0DAT and JOY1DAT
316 Format: <a>,<b>
317 See also Documentation/kernel/input/joystick.txt
319 analog.map= [HW,JOY] Analog joystick and gamepad support
320 Specifies type or capabilities of an analog joystick
321 connected to one of 16 gameports
322 Format: <type1>,<type2>,..<type16>
324 apc= [HW,SPARC]
325 Power management functions (SPARCstation-4/5 + deriv.)
326 Format: noidle
327 Disable APC CPU standby support. SPARCstation-Fox does
328 not play well with APC CPU idle - disable it if you have
329 APC and your system crashes randomly.
331 apic= [APIC,i386] Advanced Programmable Interrupt Controller
332 Change the output verbosity whilst booting
333 Format: { quiet (default) | verbose | debug }
334 Change the amount of debugging information output
335 when initialising the APIC and IO-APIC components.
337 apm= [APM] Advanced Power Management
338 See header of arch/x86/kernel/apm_32.c.
340 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
341 Format: <io>,<irq>,<nodeID>
343 ataflop= [HW,M68k]
345 atarimouse= [HW,MOUSE] Atari Mouse
347 atascsi= [HW,SCSI] Atari SCSI
349 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
350 EzKey and similar keyboards
352 atkbd.reset= [HW] Reset keyboard during initialization
354 atkbd.set= [HW] Select keyboard code set
355 Format: <int> (2 = AT (default), 3 = PS/2)
357 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
358 keyboards
360 atkbd.softraw= [HW] Choose between synthetic and real raw mode
361 Format: <bool> (0 = real, 1 = synthetic (default))
363 atkbd.softrepeat= [HW]
364 Use software keyboard repeat
366 autotest [IA64]
368 baycom_epp= [HW,AX25]
369 Format: <io>,<mode>
371 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
372 Format: <io>,<mode>
373 See header of drivers/net/hamradio/baycom_par.c.
375 baycom_ser_fdx= [HW,AX25]
376 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
377 Format: <io>,<irq>,<mode>[,<baud>]
378 See header of drivers/net/hamradio/baycom_ser_fdx.c.
380 baycom_ser_hdx= [HW,AX25]
381 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
382 Format: <io>,<irq>,<mode>
383 See header of drivers/net/hamradio/baycom_ser_hdx.c.
385 boot_delay= Milliseconds to delay each printk during boot.
386 Values larger than 10 seconds (10000) are changed to
387 no delay (0).
388 Format: integer
390 bootmem_debug [KNL] Enable bootmem allocator debug messages.
392 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
393 bttv.radio= Most important insmod options are available as
394 kernel args too.
395 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
396 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
398 BusLogic= [HW,SCSI]
399 See drivers/scsi/BusLogic.c, comment before function
400 BusLogic_ParseDriverOptions().
402 c101= [NET] Moxa C101 synchronous serial card
404 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
405 Sometimes CPU hardware bugs make them report the cache
406 size incorrectly. The kernel will attempt work arounds
407 to fix known problems, but for some CPUs it is not
408 possible to determine what the correct size should be.
409 This option provides an override for these situations.
411 security= [SECURITY] Choose a security module to enable at boot.
412 If this boot parameter is not specified, only the first
413 security module asking for security registration will be
414 loaded. An invalid security module name will be treated
415 as if no module has been chosen.
417 capability.disable=
418 [SECURITY] Disable capabilities. This would normally
419 be used only if an alternative security model is to be
420 configured. Potentially dangerous and should only be
421 used if you are entirely sure of the consequences.
423 ccw_timeout_log [S390]
424 See Documentation/s390/CommonIO for details.
426 cgroup_disable= [KNL] Disable a particular controller
427 Format: {name of the controller(s) to disable}
428 {Currently supported controllers - "memory"}
430 checkreqprot [SELINUX] Set initial checkreqprot flag value.
431 Format: { "0" | "1" }
432 See security/selinux/Kconfig help text.
433 0 -- check protection applied by kernel (includes
434 any implied execute protection).
435 1 -- check protection requested by application.
436 Default value is set via a kernel config option.
437 Value can be changed at runtime via
438 /selinux/checkreqprot.
440 cio_ignore= [S390]
441 See Documentation/s390/CommonIO for details.
443 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
444 [Deprecated]
445 Forces specified clocksource (if available) to be used
446 when calculating gettimeofday(). If specified
447 clocksource is not available, it defaults to PIT.
448 Format: { pit | tsc | cyclone | pmtmr }
450 clocksource= [GENERIC_TIME] Override the default clocksource
451 Format: <string>
452 Override the default clocksource and use the clocksource
453 with the name specified.
454 Some clocksource names to choose from, depending on
455 the platform:
456 [all] jiffies (this is the base, fallback clocksource)
457 [ACPI] acpi_pm
458 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
459 pxa_timer,timer3,32k_counter,timer0_1
460 [AVR32] avr32
461 [X86-32] pit,hpet,tsc,vmi-timer;
462 scx200_hrt on Geode; cyclone on IBM x440
463 [MIPS] MIPS
464 [PARISC] cr16
465 [S390] tod
466 [SH] SuperH
467 [SPARC64] tick
468 [X86-64] hpet,tsc
470 clearcpuid=BITNUM [X86]
471 Disable CPUID feature X for the kernel. See
472 arch/x86/include/asm/cpufeature.h for the valid bit
473 numbers. Note the Linux specific bits are not necessarily
474 stable over kernel options, but the vendor specific
475 ones should be.
476 Also note that user programs calling CPUID directly
477 or using the feature without checking anything
478 will still see it. This just prevents it from
479 being used by the kernel or shown in /proc/cpuinfo.
480 Also note the kernel might malfunction if you disable
481 some critical bits.
483 code_bytes [IA32/X86_64] How many bytes of object code to print
484 in an oops report.
485 Range: 0 - 8192
486 Default: 64
488 hpet= [X86-32,HPET] option to control HPET usage
489 Format: { enable (default) | disable | force }
490 disable: disable HPET and use PIT instead
491 force: allow force enabled of undocumented chips (ICH4,
492 VIA, nVidia)
494 com20020= [HW,NET] ARCnet - COM20020 chipset
495 Format:
496 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
498 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
499 Format: <io>[,<irq>]
501 com90xx= [HW,NET]
502 ARCnet - COM90xx chipset (memory-mapped buffers)
503 Format: <io>[,<irq>[,<memstart>]]
505 condev= [HW,S390] console device
506 conmode=
508 console= [KNL] Output console device and options.
510 tty<n> Use the virtual console device <n>.
512 ttyS<n>[,options]
513 ttyUSB0[,options]
514 Use the specified serial port. The options are of
515 the form "bbbbpnf", where "bbbb" is the baud rate,
516 "p" is parity ("n", "o", or "e"), "n" is number of
517 bits, and "f" is flow control ("r" for RTS or
518 omit it). Default is "9600n8".
520 See Documentation/serial-console.txt for more
521 information. See
522 Documentation/networking/netconsole.txt for an
523 alternative.
525 uart[8250],io,<addr>[,options]
526 uart[8250],mmio,<addr>[,options]
527 Start an early, polled-mode console on the 8250/16550
528 UART at the specified I/O port or MMIO address,
529 switching to the matching ttyS device later. The
530 options are the same as for ttyS, above.
532 If the device connected to the port is not a TTY but a braille
533 device, prepend "brl," before the device type, for instance
534 console=brl,ttyS0
535 For now, only VisioBraille is supported.
537 earlycon= [KNL] Output early console device and options.
538 uart[8250],io,<addr>[,options]
539 uart[8250],mmio,<addr>[,options]
540 Start an early, polled-mode console on the 8250/16550
541 UART at the specified I/O port or MMIO address.
542 The options are the same as for ttyS, above.
544 no_console_suspend
545 [HW] Never suspend the console
546 Disable suspending of consoles during suspend and
547 hibernate operations. Once disabled, debugging
548 messages can reach various consoles while the rest
549 of the system is being put to sleep (ie, while
550 debugging driver suspend/resume hooks). This may
551 not work reliably with all consoles, but is known
552 to work with serial and VGA consoles.
554 coredump_filter=
555 [KNL] Change the default value for
556 /proc/<pid>/coredump_filter.
557 See also Documentation/filesystems/proc.txt.
559 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
560 Format:
561 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
563 crashkernel=nn[KMG]@ss[KMG]
564 [KNL] Reserve a chunk of physical memory to
565 hold a kernel to switch to with kexec on panic.
567 crashkernel=range1:size1[,range2:size2,...][@offset]
568 [KNL] Same as above, but depends on the memory
569 in the running system. The syntax of range is
570 start-[end] where start and end are both
571 a memory unit (amount[KMG]). See also
572 Documentation/kdump/kdump.txt for a example.
574 cs4232= [HW,OSS]
575 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
577 cs89x0_dma= [HW,NET]
578 Format: <dma>
580 cs89x0_media= [HW,NET]
581 Format: { rj45 | aui | bnc }
583 dasd= [HW,NET]
584 See header of drivers/s390/block/dasd_devmap.c.
586 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
587 (one device per port)
588 Format: <port#>,<type>
589 See also Documentation/input/joystick-parport.txt
591 debug [KNL] Enable kernel debugging (events log level).
593 debug_locks_verbose=
594 [KNL] verbose self-tests
595 Format=<0|1>
596 Print debugging info while doing the locking API
597 self-tests.
598 We default to 0 (no extra messages), setting it to
599 1 will print _a lot_ more information - normally
600 only useful to kernel developers.
602 debug_objects [KNL] Enable object debugging
604 debugpat [X86] Enable PAT debugging
606 decnet.addr= [HW,NET]
607 Format: <area>[,<node>]
608 See also Documentation/networking/decnet.txt.
610 vt.default_blu= [VT]
611 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
612 Change the default blue palette of the console.
613 This is a 16-member array composed of values
614 ranging from 0-255.
616 vt.default_grn= [VT]
617 Format: <green0>,<green1>,<green2>,...,<green15>
618 Change the default green palette of the console.
619 This is a 16-member array composed of values
620 ranging from 0-255.
622 vt.default_red= [VT]
623 Format: <red0>,<red1>,<red2>,...,<red15>
624 Change the default red palette of the console.
625 This is a 16-member array composed of values
626 ranging from 0-255.
628 vt.default_utf8=
629 [VT]
630 Format=<0|1>
631 Set system-wide default UTF-8 mode for all tty's.
632 Default is 1, i.e. UTF-8 mode is enabled for all
633 newly opened terminals.
635 dhash_entries= [KNL]
636 Set number of hash buckets for dentry cache.
638 digi= [HW,SERIAL]
639 IO parameters + enable/disable command.
641 digiepca= [HW,SERIAL]
642 See drivers/char/README.epca and
643 Documentation/serial/digiepca.txt.
645 disable_mtrr_cleanup [X86]
646 enable_mtrr_cleanup [X86]
647 The kernel tries to adjust MTRR layout from continuous
648 to discrete, to make X server driver able to add WB
649 entry later. This parameter enables/disables that.
651 mtrr_chunk_size=nn[KMG] [X86]
652 used for mtrr cleanup. It is largest continous chunk
653 that could hold holes aka. UC entries.
655 mtrr_gran_size=nn[KMG] [X86]
656 Used for mtrr cleanup. It is granularity of mtrr block.
657 Default is 1.
658 Large value could prevent small alignment from
659 using up MTRRs.
661 mtrr_spare_reg_nr=n [X86]
662 Format: <integer>
663 Range: 0,7 : spare reg number
664 Default : 1
665 Used for mtrr cleanup. It is spare mtrr entries number.
666 Set to 2 or more if your graphical card needs more.
668 disable_mtrr_trim [X86, Intel and AMD only]
669 By default the kernel will trim any uncacheable
670 memory out of your available memory pool based on
671 MTRR settings. This parameter disables that behavior,
672 possibly causing your machine to run very slowly.
674 dmasound= [HW,OSS] Sound subsystem buffers
676 dscc4.setup= [NET]
678 dtc3181e= [HW,SCSI]
680 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
681 earlyprintk=vga
682 earlyprintk=serial[,ttySn[,baudrate]]
683 earlyprintk=dbgp
685 Append ",keep" to not disable it when the real console
686 takes over.
688 Only vga or serial or usb debug port at a time.
690 Currently only ttyS0 and ttyS1 are supported.
692 Interaction with the standard serial driver is not
693 very good.
695 The VGA output is eventually overwritten by the real
696 console.
698 eata= [HW,SCSI]
700 edd= [EDD]
701 Format: {"off" | "on" | "skip[mbr]"}
703 eisa_irq_edge= [PARISC,HW]
704 See header of drivers/parisc/eisa.c.
706 elanfreq= [X86-32]
707 See comment before function elanfreq_setup() in
708 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
710 elevator= [IOSCHED]
711 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
712 See Documentation/block/as-iosched.txt and
713 Documentation/block/deadline-iosched.txt for details.
715 elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
716 Specifies physical address of start of kernel core
717 image elf header. Generally kexec loader will
718 pass this option to capture kernel.
719 See Documentation/kdump/kdump.txt for details.
721 enforcing [SELINUX] Set initial enforcing status.
722 Format: {"0" | "1"}
723 See security/selinux/Kconfig help text.
724 0 -- permissive (log only, no denials).
725 1 -- enforcing (deny and log).
726 Default value is 0.
727 Value can be changed at runtime via /selinux/enforce.
729 es1371= [HW,OSS]
730 Format: <spdif>,[<nomix>,[<amplifier>]]
731 See also header of sound/oss/es1371.c.
733 ether= [HW,NET] Ethernet cards parameters
734 This option is obsoleted by the "netdev=" option, which
735 has equivalent usage. See its documentation for details.
737 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
738 Format: <io>[,<irq>]
740 failslab=
741 fail_page_alloc=
742 fail_make_request=[KNL]
743 General fault injection mechanism.
744 Format: <interval>,<probability>,<space>,<times>
745 See also /Documentation/fault-injection/.
747 fd_mcs= [HW,SCSI]
748 See header of drivers/scsi/fd_mcs.c.
750 fdomain= [HW,SCSI]
751 See header of drivers/scsi/fdomain.c.
753 floppy= [HW]
754 See Documentation/blockdev/floppy.txt.
756 force_pal_cache_flush
757 [IA-64] Avoid check_sal_cache_flush which may hang on
758 buggy SAL_CACHE_FLUSH implementations. Using this
759 parameter will force ia64_sal_cache_flush to call
760 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
762 ftrace=[tracer]
763 [ftrace] will set and start the specified tracer
764 as early as possible in order to facilitate early
765 boot debugging.
767 ftrace_dump_on_oops
768 [ftrace] will dump the trace buffers on oops.
770 gamecon.map[2|3]=
771 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
772 support via parallel port (up to 5 devices per port)
773 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
774 See also Documentation/input/joystick-parport.txt
776 gamma= [HW,DRM]
778 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
779 Format: off | on
780 default: on
782 gdth= [HW,SCSI]
783 See header of drivers/scsi/gdth.c.
785 gpt [EFI] Forces disk with valid GPT signature but
786 invalid Protective MBR to be treated as GPT.
788 gvp11= [HW,SCSI]
790 hashdist= [KNL,NUMA] Large hashes allocated during boot
791 are distributed across NUMA nodes. Defaults on
792 for IA-64, off otherwise.
793 Format: 0 | 1 (for off | on)
795 hcl= [IA-64] SGI's Hardware Graph compatibility layer
797 hd= [EIDE] (E)IDE hard drive subsystem geometry
798 Format: <cyl>,<head>,<sect>
800 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
801 size of <nn>. This works even on boxes that have no
802 highmem otherwise. This also works to reduce highmem
803 size on bigger boxes.
805 highres= [KNL] Enable/disable high resolution timer mode.
806 Valid parameters: "on", "off"
807 Default: "on"
809 hisax= [HW,ISDN]
810 See Documentation/isdn/README.HiSax.
812 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
813 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
814 On x86-64 and powerpc, this option can be specified
815 multiple times interleaved with hugepages= to reserve
816 huge pages of different sizes. Valid pages sizes on
817 x86-64 are 2M (when the CPU supports "pse") and 1G
818 (when the CPU supports the "pdpe1gb" cpuinfo flag)
819 Note that 1GB pages can only be allocated at boot time
820 using hugepages= and not freed afterwards.
821 default_hugepagesz=
822 [same as hugepagesz=] The size of the default
823 HugeTLB page size. This is the size represented by
824 the legacy /proc/ hugepages APIs, used for SHM, and
825 default size when mounting hugetlbfs filesystems.
826 Defaults to the default architecture's huge page size
827 if not specified.
829 hlt [BUGS=ARM,SH]
831 hvc_iucv= [S390] Number of z/VM IUCV Hypervisor console (HVC)
832 back-ends. Valid parameters: 0..8
834 i8042.debug [HW] Toggle i8042 debug mode
835 i8042.direct [HW] Put keyboard port into non-translated mode
836 i8042.dumbkbd [HW] Pretend that controller can only read data from
837 keyboard and cannot control its state
838 (Don't attempt to blink the leds)
839 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
840 i8042.nokbd [HW] Don't check/create keyboard port
841 i8042.noloop [HW] Disable the AUX Loopback command while probing
842 for the AUX port
843 i8042.nomux [HW] Don't check presence of an active multiplexing
844 controller
845 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
846 controllers
847 i8042.panicblink=
848 [HW] Frequency with which keyboard LEDs should blink
849 when kernel panics (default is 0.5 sec)
850 i8042.reset [HW] Reset the controller during init and cleanup
851 i8042.unlock [HW] Unlock (ignore) the keylock
853 i810= [HW,DRM]
855 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
856 indicates that the driver is running on unsupported
857 hardware.
858 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
859 does not match list of supported models.
860 i8k.power_status
861 [HW] Report power status in /proc/i8k
862 (disabled by default)
863 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
864 capability is set.
866 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
867 See Documentation/mca.txt.
869 icn= [HW,ISDN]
870 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
872 ide= [HW] (E)IDE subsystem
873 Format: ide=nodma or ide=doubler
874 See Documentation/ide/ide.txt.
876 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
877 See Documentation/ide/ide.txt.
879 idle= [X86]
880 Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
881 Poll forces a polling idle loop that can slightly improves the performance
882 of waking up a idle CPU, but will use a lot of power and make the system
883 run hot. Not recommended.
884 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
885 to not use it because it doesn't save as much power as a normal idle
886 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
887 as idle=poll.
888 idle=halt. Halt is forced to be used for CPU idle.
889 In such case C2/C3 won't be used again.
890 idle=nomwait. Disable mwait for CPU C-states
892 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
893 Claim all unknown PCI IDE storage controllers.
895 ignore_loglevel [KNL]
896 Ignore loglevel setting - this will print /all/
897 kernel messages to the console. Useful for debugging.
899 ihash_entries= [KNL]
900 Set number of hash buckets for inode cache.
902 in2000= [HW,SCSI]
903 See header of drivers/scsi/in2000.c.
905 init= [KNL]
906 Format: <full_path>
907 Run specified binary instead of /sbin/init as init
908 process.
910 initcall_debug [KNL] Trace initcalls as they are executed. Useful
911 for working out where the kernel is dying during
912 startup.
914 initrd= [BOOT] Specify the location of the initial ramdisk
916 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
917 Format: <irq>
919 inttest= [IA64]
921 iommu= [x86]
922 off
923 force
924 noforce
925 biomerge
926 panic
927 nopanic
928 merge
929 nomerge
930 forcesac
931 soft
934 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
935 off
936 Disable intel iommu driver.
937 igfx_off [Default Off]
938 By default, gfx is mapped as normal device. If a gfx
939 device has a dedicated DMAR unit, the DMAR unit is
940 bypassed by not enabling DMAR with this option. In
941 this case, gfx device will use physical address for
942 DMA.
943 forcedac [x86_64]
944 With this option iommu will not optimize to look
945 for io virtual address below 32 bit forcing dual
946 address cycle on pci bus for cards supporting greater
947 than 32 bit addressing. The default is to look
948 for translation below 32 bit and if not available
949 then look in the higher range.
950 strict [Default Off]
951 With this option on every unmap_single operation will
952 result in a hardware IOTLB flush operation as opposed
953 to batching them for performance.
955 io_delay= [X86-32,X86-64] I/O delay method
956 0x80
957 Standard port 0x80 based delay
958 0xed
959 Alternate port 0xed based delay (needed on some systems)
960 udelay
961 Simple two microseconds delay
962 none
963 No delay
965 io7= [HW] IO7 for Marvel based alpha systems
966 See comment before marvel_specify_io7 in
967 arch/alpha/kernel/core_marvel.c.
969 ip= [IP_PNP]
970 See Documentation/filesystems/nfsroot.txt.
972 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
973 See comment before ip2_setup() in
974 drivers/char/ip2/ip2base.c.
976 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
977 See header of drivers/scsi/ips.c.
979 ports= [IP_VS_FTP] IPVS ftp helper module
980 Default is 21.
981 Up to 8 (IP_VS_APP_MAX_PORTS) ports
982 may be specified.
983 Format: <port>,<port>....
985 irqfixup [HW]
986 When an interrupt is not handled search all handlers
987 for it. Intended to get systems with badly broken
988 firmware running.
990 irqpoll [HW]
991 When an interrupt is not handled search all handlers
992 for it. Also check all handlers each timer
993 interrupt. Intended to get systems with badly broken
994 firmware running.
996 isapnp= [ISAPNP]
997 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
999 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1000 Format:
1001 <cpu number>,...,<cpu number>
1002 or
1003 <cpu number>-<cpu number>
1004 (must be a positive range in ascending order)
1005 or a mixture
1006 <cpu number>,...,<cpu number>-<cpu number>
1008 This option can be used to specify one or more CPUs
1009 to isolate from the general SMP balancing and scheduling
1010 algorithms. You can move a process onto or off an
1011 "isolated" CPU via the CPU affinity syscalls or cpuset.
1012 <cpu number> begins at 0 and the maximum value is
1013 "number of CPUs in system - 1".
1015 This option is the preferred way to isolate CPUs. The
1016 alternative -- manually setting the CPU mask of all
1017 tasks in the system -- can cause problems and
1018 suboptimal load balancer performance.
1020 iucv= [HW,NET]
1022 js= [HW,JOY] Analog joystick
1023 See Documentation/input/joystick.txt.
1025 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1026 specifies the amount of memory usable by the kernel
1027 for non-movable allocations. The requested amount is
1028 spread evenly throughout all nodes in the system. The
1029 remaining memory in each node is used for Movable
1030 pages. In the event, a node is too small to have both
1031 kernelcore and Movable pages, kernelcore pages will
1032 take priority and other nodes will have a larger number
1033 of kernelcore pages. The Movable zone is used for the
1034 allocation of pages that may be reclaimed or moved
1035 by the page migration subsystem. This means that
1036 HugeTLB pages may not be allocated from this zone.
1037 Note that allocations like PTEs-from-HighMem still
1038 use the HighMem zone if it exists, and the Normal
1039 zone if it does not.
1041 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1042 is similar to kernelcore except it specifies the
1043 amount of memory used for migratable allocations.
1044 If both kernelcore and movablecore is specified,
1045 then kernelcore will be at *least* the specified
1046 value but may be more. If movablecore on its own
1047 is specified, the administrator must be careful
1048 that the amount of memory usable for all allocations
1049 is not too small.
1051 keepinitrd [HW,ARM]
1053 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1054 in oops dumps.
1056 kgdboc= [HW] kgdb over consoles.
1057 Requires a tty driver that supports console polling.
1058 (only serial suported for now)
1059 Format: <serial_device>[,baud]
1061 kmac= [MIPS] korina ethernet MAC address.
1062 Configure the RouterBoard 532 series on-chip
1063 Ethernet adapter MAC address.
1065 l2cr= [PPC]
1067 l3cr= [PPC]
1069 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1070 disabled it.
1072 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
1073 C2 power state.
1075 libata.dma= [LIBATA] DMA control
1076 libata.dma=0 Disable all PATA and SATA DMA
1077 libata.dma=1 PATA and SATA Disk DMA only
1078 libata.dma=2 ATAPI (CDROM) DMA only
1079 libata.dma=4 Compact Flash DMA only
1080 Combinations also work, so libata.dma=3 enables DMA
1081 for disks and CDROMs, but not CFs.
1083 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1084 when set.
1085 Format: <int>
1087 libata.force= [LIBATA] Force configurations. The format is comma
1088 separated list of "[ID:]VAL" where ID is
1089 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1090 matching port, link or device. Basically, it matches
1091 the ATA ID string printed on console by libata. If
1092 the whole ID part is omitted, the last PORT and DEVICE
1093 values are used. If ID hasn't been specified yet, the
1094 configuration applies to all ports, links and devices.
1096 If only DEVICE is omitted, the parameter applies to
1097 the port and all links and devices behind it. DEVICE
1098 number of 0 either selects the first device or the
1099 first fan-out link behind PMP device. It does not
1100 select the host link. DEVICE number of 15 selects the
1101 host link and device attached to it.
1103 The VAL specifies the configuration to force. As long
1104 as there's no ambiguity shortcut notation is allowed.
1105 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1106 The following configurations can be forced.
1108 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1109 Any ID with matching PORT is used.
1111 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1113 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1114 udma[/][16,25,33,44,66,100,133] notation is also
1115 allowed.
1117 * [no]ncq: Turn on or off NCQ.
1119 * nohrst, nosrst, norst: suppress hard, soft
1120 and both resets.
1122 If there are multiple matching configurations changing
1123 the same attribute, the last one is used.
1125 lmb=debug [KNL] Enable lmb debug messages.
1127 load_ramdisk= [RAM] List of ramdisks to load from floppy
1128 See Documentation/blockdev/ramdisk.txt.
1130 lockd.nlm_grace_period=P [NFS] Assign grace period.
1131 Format: <integer>
1133 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1134 Format: <integer>
1136 lockd.nlm_timeout=T [NFS] Assign timeout value.
1137 Format: <integer>
1139 lockd.nlm_udpport=M [NFS] Assign UDP port.
1140 Format: <integer>
1142 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1143 Format: <irq>
1145 loglevel= All Kernel Messages with a loglevel smaller than the
1146 console loglevel will be printed to the console. It can
1147 also be changed with klogd or other programs. The
1148 loglevels are defined as follows:
1150 0 (KERN_EMERG) system is unusable
1151 1 (KERN_ALERT) action must be taken immediately
1152 2 (KERN_CRIT) critical conditions
1153 3 (KERN_ERR) error conditions
1154 4 (KERN_WARNING) warning conditions
1155 5 (KERN_NOTICE) normal but significant condition
1156 6 (KERN_INFO) informational
1157 7 (KERN_DEBUG) debug-level messages
1159 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1160 Format: { n | nk | nM }
1161 n must be a power of two. The default size
1162 is set in the kernel config file.
1164 logo.nologo [FB] Disables display of the built-in Linux logo.
1165 This may be used to provide more screen space for
1166 kernel log messages and is useful when debugging
1167 kernel boot problems.
1169 lp=0 [LP] Specify parallel ports to use, e.g,
1170 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1171 lp=reset first parallel port). 'lp=0' disables the
1172 lp=auto printer driver. 'lp=reset' (which can be
1173 specified in addition to the ports) causes
1174 attached printers to be reset. Using
1175 lp=port1,port2,... specifies the parallel ports
1176 to associate lp devices with, starting with
1177 lp0. A port specification may be 'none' to skip
1178 that lp device, or a parport name such as
1179 'parport0'. Specifying 'lp=auto' instead of a
1180 port specification list means that device IDs
1181 from each port should be examined, to see if
1182 an IEEE 1284-compliant printer is attached; if
1183 so, the driver will manage that printer.
1184 See also header of drivers/char/lp.c.
1186 lpj=n [KNL]
1187 Sets loops_per_jiffy to given constant, thus avoiding
1188 time-consuming boot-time autodetection (up to 250 ms per
1189 CPU). 0 enables autodetection (default). To determine
1190 the correct value for your kernel, boot with normal
1191 autodetection and see what value is printed. Note that
1192 on SMP systems the preset will be applied to all CPUs,
1193 which is likely to cause problems if your CPUs need
1194 significantly divergent settings. An incorrect value
1195 will cause delays in the kernel to be wrong, leading to
1196 unpredictable I/O errors and other breakage. Although
1197 unlikely, in the extreme case this might damage your
1198 hardware.
1200 ltpc= [NET]
1201 Format: <io>,<irq>,<dma>
1203 mac5380= [HW,SCSI] Format:
1204 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1206 machvec= [IA64] Force the use of a particular machine-vector
1207 (machvec) in a generic kernel.
1208 Example: machvec=hpzx1_swiotlb
1210 max_loop= [LOOP] Maximum number of loopback devices that can
1211 be mounted
1212 Format: <1-256>
1214 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1215 should make use of. maxcpus=n : n >= 0 limits the
1216 kernel to using 'n' processors. n=0 is a special case,
1217 it is equivalent to "nosmp", which also disables
1218 the IO APIC.
1220 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than
1221 or equal to this physical address is ignored.
1223 max_luns= [SCSI] Maximum number of LUNs to probe.
1224 Should be between 1 and 2^32-1.
1226 max_report_luns=
1227 [SCSI] Maximum number of LUNs received.
1228 Should be between 1 and 16384.
1230 mcatest= [IA-64]
1232 mce [X86-32] Machine Check Exception
1234 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1236 md= [HW] RAID subsystems devices and level
1237 See Documentation/md.txt.
1239 mdacon= [MDA]
1240 Format: <first>,<last>
1241 Specifies range of consoles to be captured by the MDA.
1243 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1244 Amount of memory to be used when the kernel is not able
1245 to see the whole system memory or for test.
1246 [X86-32] Use together with memmap= to avoid physical
1247 address space collisions. Without memmap= PCI devices
1248 could be placed at addresses belonging to unused RAM.
1250 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1251 memory.
1253 memchunk=nn[KMG]
1254 [KNL,SH] Allow user to override the default size for
1255 per-device physically contiguous DMA buffers.
1257 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1258 E820 memory map, as specified by the user.
1259 Such memmap=exactmap lines can be constructed based on
1260 BIOS output or other requirements. See the memmap=nn@ss
1261 option description.
1263 memmap=nn[KMG]@ss[KMG]
1264 [KNL] Force usage of a specific region of memory
1265 Region of memory to be used, from ss to ss+nn.
1267 memmap=nn[KMG]#ss[KMG]
1268 [KNL,ACPI] Mark specific memory as ACPI data.
1269 Region of memory to be used, from ss to ss+nn.
1271 memmap=nn[KMG]$ss[KMG]
1272 [KNL,ACPI] Mark specific memory as reserved.
1273 Region of memory to be used, from ss to ss+nn.
1274 Example: Exclude memory from 0x18690000-0x1869ffff
1275 memmap=64K$0x18690000
1276 or
1277 memmap=0x10000$0x18690000
1279 memory_corruption_check=0/1 [X86]
1280 Some BIOSes seem to corrupt the first 64k of
1281 memory when doing things like suspend/resume.
1282 Setting this option will scan the memory
1283 looking for corruption. Enabling this will
1284 both detect corruption and prevent the kernel
1285 from using the memory being corrupted.
1286 However, its intended as a diagnostic tool; if
1287 repeatable BIOS-originated corruption always
1288 affects the same memory, you can use memmap=
1289 to prevent the kernel from using that memory.
1291 memory_corruption_check_size=size [X86]
1292 By default it checks for corruption in the low
1293 64k, making this memory unavailable for normal
1294 use. Use this parameter to scan for
1295 corruption in more or less memory.
1297 memory_corruption_check_period=seconds [X86]
1298 By default it checks for corruption every 60
1299 seconds. Use this parameter to check at some
1300 other rate. 0 disables periodic checking.
1302 memtest= [KNL,X86] Enable memtest
1303 Format: <integer>
1304 range: 0,4 : pattern number
1305 default : 0 <disable>
1307 meye.*= [HW] Set MotionEye Camera parameters
1308 See Documentation/video4linux/meye.txt.
1310 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1311 Multi-Function General Purpose Timers on AMD Geode
1312 platforms.
1314 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1315 the BIOS has incorrectly applied a workaround. TinyBIOS
1316 version 0.98 is known to be affected, 0.99 fixes the
1317 problem by letting the user disable the workaround.
1319 mga= [HW,DRM]
1321 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1322 physical address is ignored.
1324 mminit_loglevel=
1325 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1326 parameter allows control of the logging verbosity for
1327 the additional memory initialisation checks. A value
1328 of 0 disables mminit logging and a level of 4 will
1329 log everything. Information is printed at KERN_DEBUG
1330 so loglevel=8 may also need to be specified.
1332 mousedev.tap_time=
1333 [MOUSE] Maximum time between finger touching and
1334 leaving touchpad surface for touch to be considered
1335 a tap and be reported as a left button click (for
1336 touchpads working in absolute mode only).
1337 Format: <msecs>
1338 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1339 reporting absolute coordinates, such as tablets
1340 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1341 reporting absolute coordinates, such as tablets
1343 mpu401= [HW,OSS]
1344 Format: <io>,<irq>
1346 MTD_Partition= [MTD]
1347 Format: <name>,<region-number>,<size>,<offset>
1349 MTD_Region= [MTD] Format:
1350 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1352 mtdparts= [MTD]
1353 See drivers/mtd/cmdlinepart.c.
1355 mtdset= [ARM]
1356 ARM/S3C2412 JIVE boot control
1358 See arch/arm/mach-s3c2412/mach-jive.c
1360 mtouchusb.raw_coordinates=
1361 [HW] Make the MicroTouch USB driver use raw coordinates
1362 ('y', default) or cooked coordinates ('n')
1364 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1366 NCR_D700= [HW,SCSI]
1367 See header of drivers/scsi/NCR_D700.c.
1369 ncr5380= [HW,SCSI]
1371 ncr53c400= [HW,SCSI]
1373 ncr53c400a= [HW,SCSI]
1375 ncr53c406a= [HW,SCSI]
1377 ncr53c8xx= [HW,SCSI]
1379 netdev= [NET] Network devices parameters
1380 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1381 Note that mem_start is often overloaded to mean
1382 something different and driver-specific.
1383 This usage is only documented in each driver source
1384 file if at all.
1386 nf_conntrack.acct=
1387 [NETFILTER] Enable connection tracking flow accounting
1388 0 to disable accounting
1389 1 to enable accounting
1390 Default value depends on CONFIG_NF_CT_ACCT that is
1391 going to be removed in 2.6.29.
1393 nfsaddrs= [NFS]
1394 See Documentation/filesystems/nfsroot.txt.
1396 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1397 See Documentation/filesystems/nfsroot.txt.
1399 nfs.callback_tcpport=
1400 [NFS] set the TCP port on which the NFSv4 callback
1401 channel should listen.
1403 nfs.idmap_cache_timeout=
1404 [NFS] set the maximum lifetime for idmapper cache
1405 entries.
1407 nfs.enable_ino64=
1408 [NFS] enable 64-bit inode numbers.
1409 If zero, the NFS client will fake up a 32-bit inode
1410 number for the readdir() and stat() syscalls instead
1411 of returning the full 64-bit number.
1412 The default is to return 64-bit inode numbers.
1414 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1415 when a NMI is triggered.
1416 Format: [state][,regs][,debounce][,die]
1418 nmi_watchdog= [KNL,BUGS=X86-32,X86-64] Debugging features for SMP kernels
1419 Format: [panic,][num]
1420 Valid num: 0,1,2
1421 0 - turn nmi_watchdog off
1422 1 - use the IO-APIC timer for the NMI watchdog
1423 2 - use the local APIC for the NMI watchdog using
1424 a performance counter. Note: This will use one performance
1425 counter and the local APIC's performance vector.
1426 When panic is specified panic when an NMI watchdog timeout occurs.
1427 This is useful when you use a panic=... timeout and need the box
1428 quickly up again.
1429 Instead of 1 and 2 it is possible to use the following
1430 symbolic names: lapic and ioapic
1431 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1433 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1434 emulation library even if a 387 maths coprocessor
1435 is present.
1437 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1438 caches in the slab allocator. Saves per-node memory,
1439 but will impact performance.
1441 noalign [KNL,ARM]
1443 noapic [SMP,APIC] Tells the kernel to not make use of any
1444 IOAPICs that may be present in the system.
1446 nobats [PPC] Do not use BATs for mapping kernel lowmem
1447 on "Classic" PPC cores.
1449 nocache [ARM]
1451 nodelayacct [KNL] Disable per-task delay accounting
1453 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1455 nodsp [SH] Disable hardware DSP at boot time.
1457 noefi [X86-32,X86-64] Disable EFI runtime services support.
1459 noexec [IA-64]
1461 noexec [X86-32,X86-64]
1462 On X86-32 available only on PAE configured kernels.
1463 noexec=on: enable non-executable mappings (default)
1464 noexec=off: disable non-executable mappings
1466 noexec32 [X86-64]
1467 This affects only 32-bit executables.
1468 noexec32=on: enable non-executable mappings (default)
1469 read doesn't imply executable mappings
1470 noexec32=off: disable non-executable mappings
1471 read implies executable mappings
1473 nofpu [SH] Disable hardware FPU at boot time.
1475 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1476 register save and restore. The kernel will only save
1477 legacy floating-point registers on task switch.
1479 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1481 nohlt [BUGS=ARM,SH]
1483 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1484 instruction doesn't work correctly and not to
1485 use it.
1487 no_file_caps Tells the kernel not to honor file capabilities. The
1488 only way then for a file to be executed with privilege
1489 is to be setuid root or executed by root.
1491 nohalt [IA-64] Tells the kernel not to use the power saving
1492 function PAL_HALT_LIGHT when idle. This increases
1493 power-consumption. On the positive side, it reduces
1494 interrupt wake-up latency, which may improve performance
1495 in certain environments such as networked servers or
1496 real-time systems.
1498 nohz= [KNL] Boottime enable/disable dynamic ticks
1499 Valid arguments: on, off
1500 Default: on
1502 noirqdebug [X86-32] Disables the code which attempts to detect and
1503 disable unhandled interrupt sources.
1505 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1506 broken timer IRQ sources.
1508 noisapnp [ISAPNP] Disables ISA PnP code.
1510 noinitrd [RAM] Tells the kernel not to load any configured
1511 initial RAM disk.
1513 nointroute [IA-64]
1515 nojitter [IA64] Disables jitter checking for ITC timers.
1517 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1519 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1521 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1523 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
1524 default x2apic cluster mode on platforms
1525 supporting x2apic.
1527 noltlbs [PPC] Do not use large page/tlb entries for kernel
1528 lowmem mapping on PPC40x.
1530 nomca [IA-64] Disable machine check abort handling
1532 nomce [X86-32] Machine Check Exception
1534 nomfgpt [X86-32] Disable Multi-Function General Purpose
1535 Timer usage (for AMD Geode machines).
1537 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1539 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1540 with UP alternatives
1542 noresidual [PPC] Don't use residual data on PReP machines.
1544 noresume [SWSUSP] Disables resume and restores original swap
1545 space.
1547 no-scroll [VGA] Disables scrollback.
1548 This is required for the Braillex ib80-piezo Braille
1549 reader made by F.H. Papenmeier (Germany).
1551 nosbagart [IA-64]
1553 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1555 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1556 and disable the IO APIC. legacy for "maxcpus=0".
1558 nosoftlockup [KNL] Disable the soft-lockup detector.
1560 nosync [HW,M68K] Disables sync negotiation for all devices.
1562 notsc [BUGS=X86-32] Disable Time Stamp Counter
1564 nousb [USB] Disable the USB subsystem
1566 nowb [ARM]
1568 nptcg= [IA64] Override max number of concurrent global TLB
1569 purges which is reported from either PAL_VM_SUMMARY or
1570 SAL PALO.
1572 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1573 one of ['zone', 'node', 'default'] can be specified
1574 This can be set from sysctl after boot.
1575 See Documentation/sysctl/vm.txt for details.
1577 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1579 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1580 See Documentation/debugging-via-ohci1394.txt for more
1581 info.
1583 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1584 Rather than timing out after 20 ms if an EC
1585 command is not properly ACKed, override the length
1586 of the timeout. We have interrupts disabled while
1587 waiting for the ACK, so if this is set too high
1588 interrupts *may* be lost!
1590 opl3= [HW,OSS]
1591 Format: <io>
1593 oprofile.timer= [HW]
1594 Use timer interrupt instead of performance counters
1596 osst= [HW,SCSI] SCSI Tape Driver
1597 Format: <buffer_size>,<write_threshold>
1598 See also Documentation/scsi/st.txt.
1600 panic= [KNL] Kernel behaviour on panic
1601 Format: <timeout>
1603 parkbd.port= [HW] Parallel port number the keyboard adapter is
1604 connected to, default is 0.
1605 Format: <parport#>
1606 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1607 0 for XT, 1 for AT (default is AT).
1608 Format: <mode>
1610 parport= [HW,PPT] Specify parallel ports. 0 disables.
1611 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1612 Use 'auto' to force the driver to use any
1613 IRQ/DMA settings detected (the default is to
1614 ignore detected IRQ/DMA settings because of
1615 possible conflicts). You can specify the base
1616 address, IRQ, and DMA settings; IRQ and DMA
1617 should be numbers, or 'auto' (for using detected
1618 settings on that particular port), or 'nofifo'
1619 (to avoid using a FIFO even if it is detected).
1620 Parallel ports are assigned in the order they
1621 are specified on the command line, starting
1622 with parport0.
1624 parport_init_mode= [HW,PPT]
1625 Configure VIA parallel port to operate in
1626 a specific mode. This is necessary on Pegasos
1627 computer where firmware has no options for setting
1628 up parallel port mode and sets it to spp.
1629 Currently this function knows 686a and 8231 chips.
1630 Format: [spp|ps2|epp|ecp|ecpepp]
1632 pas2= [HW,OSS] Format:
1633 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1635 pas16= [HW,SCSI]
1636 See header of drivers/scsi/pas16.c.
1638 pause_on_oops=
1639 Halt all CPUs after the first oops has been printed for
1640 the specified number of seconds. This is to be used if
1641 your oopses keep scrolling off the screen.
1643 pcbit= [HW,ISDN]
1645 pcd. [PARIDE]
1646 See header of drivers/block/paride/pcd.c.
1647 See also Documentation/blockdev/paride.txt.
1649 pci=option[,option...] [PCI] various PCI subsystem options:
1650 off [X86] don't probe for the PCI bus
1651 bios [X86-32] force use of PCI BIOS, don't access
1652 the hardware directly. Use this if your machine
1653 has a non-standard PCI host bridge.
1654 nobios [X86-32] disallow use of PCI BIOS, only direct
1655 hardware access methods are allowed. Use this
1656 if you experience crashes upon bootup and you
1657 suspect they are caused by the BIOS.
1658 conf1 [X86] Force use of PCI Configuration
1659 Mechanism 1.
1660 conf2 [X86] Force use of PCI Configuration
1661 Mechanism 2.
1662 noaer [PCIE] If the PCIEAER kernel config parameter is
1663 enabled, this kernel boot option can be used to
1664 disable the use of PCIE advanced error reporting.
1665 nodomains [PCI] Disable support for multiple PCI
1666 root domains (aka PCI segments, in ACPI-speak).
1667 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1668 Configuration
1669 nomsi [MSI] If the PCI_MSI kernel config parameter is
1670 enabled, this kernel boot option can be used to
1671 disable the use of MSI interrupts system-wide.
1672 noioapicquirk [APIC] Disable all boot interrupt quirks.
1673 Safety option to keep boot IRQs enabled. This
1674 should never be necessary.
1675 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1676 primary IO-APIC for bridges that cannot disable
1677 boot IRQs. This fixes a source of spurious IRQs
1678 when the system masks IRQs.
1679 noioapicreroute [APIC] Disable workaround that uses the
1680 boot IRQ equivalent of an IRQ that connects to
1681 a chipset where boot IRQs cannot be disabled.
1682 The opposite of ioapicreroute.
1683 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1684 routing table. These calls are known to be buggy
1685 on several machines and they hang the machine
1686 when used, but on other computers it's the only
1687 way to get the interrupt routing table. Try
1688 this option if the kernel is unable to allocate
1689 IRQs or discover secondary PCI buses on your
1690 motherboard.
1691 rom [X86] Assign address space to expansion ROMs.
1692 Use with caution as certain devices share
1693 address decoders between ROMs and other
1694 resources.
1695 norom [X86] Do not assign address space to
1696 expansion ROMs that do not already have
1697 BIOS assigned address ranges.
1698 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1699 assigned automatically to PCI devices. You can
1700 make the kernel exclude IRQs of your ISA cards
1701 this way.
1702 pirqaddr=0xAAAAA [X86] Specify the physical address
1703 of the PIRQ table (normally generated
1704 by the BIOS) if it is outside the
1705 F0000h-100000h range.
1706 lastbus=N [X86] Scan all buses thru bus #N. Can be
1707 useful if the kernel is unable to find your
1708 secondary buses and you want to tell it
1709 explicitly which ones they are.
1710 assign-busses [X86] Always assign all PCI bus
1711 numbers ourselves, overriding
1712 whatever the firmware may have done.
1713 usepirqmask [X86] Honor the possible IRQ mask stored
1714 in the BIOS $PIR table. This is needed on
1715 some systems with broken BIOSes, notably
1716 some HP Pavilion N5400 and Omnibook XE3
1717 notebooks. This will have no effect if ACPI
1718 IRQ routing is enabled.
1719 noacpi [X86] Do not use ACPI for IRQ routing
1720 or for PCI scanning.
1721 use_crs [X86] Use _CRS for PCI resource
1722 allocation.
1723 routeirq Do IRQ routing for all PCI devices.
1724 This is normally done in pci_enable_device(),
1725 so this option is a temporary workaround
1726 for broken drivers that don't call it.
1727 skip_isa_align [X86] do not align io start addr, so can
1728 handle more pci cards
1729 firmware [ARM] Do not re-enumerate the bus but instead
1730 just use the configuration from the
1731 bootloader. This is currently used on
1732 IXP2000 systems where the bus has to be
1733 configured a certain way for adjunct CPUs.
1734 noearly [X86] Don't do any early type 1 scanning.
1735 This might help on some broken boards which
1736 machine check when some devices' config space
1737 is read. But various workarounds are disabled
1738 and some IOMMU drivers will not work.
1739 bfsort Sort PCI devices into breadth-first order.
1740 This sorting is done to get a device
1741 order compatible with older (<= 2.4) kernels.
1742 nobfsort Don't sort PCI devices into breadth-first order.
1743 cbiosize=nn[KMG] The fixed amount of bus space which is
1744 reserved for the CardBus bridge's IO window.
1745 The default value is 256 bytes.
1746 cbmemsize=nn[KMG] The fixed amount of bus space which is
1747 reserved for the CardBus bridge's memory
1748 window. The default value is 64 megabytes.
1750 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1751 Management.
1752 off Disable ASPM.
1753 force Enable ASPM even on devices that claim not to support it.
1754 WARNING: Forcing ASPM on may cause system lockups.
1756 pcmv= [HW,PCMCIA] BadgePAD 4
1758 pd. [PARIDE]
1759 See Documentation/blockdev/paride.txt.
1761 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1762 boot time.
1763 Format: { 0 | 1 }
1764 See arch/parisc/kernel/pdc_chassis.c
1766 pf. [PARIDE]
1767 See Documentation/blockdev/paride.txt.
1769 pg. [PARIDE]
1770 See Documentation/blockdev/paride.txt.
1772 pirq= [SMP,APIC] Manual mp-table setup
1773 See Documentation/x86/i386/IO-APIC.txt.
1775 plip= [PPT,NET] Parallel port network link
1776 Format: { parport<nr> | timid | 0 }
1777 See also Documentation/parport.txt.
1779 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1780 Override pmtimer IOPort with a hex value.
1781 e.g. pmtmr=0x508
1783 pnp.debug [PNP]
1784 Enable PNP debug messages. This depends on the
1785 CONFIG_PNP_DEBUG_MESSAGES option.
1787 pnpacpi= [ACPI]
1788 { off }
1790 pnpbios= [ISAPNP]
1791 { on | off | curr | res | no-curr | no-res }
1793 pnp_reserve_irq=
1794 [ISAPNP] Exclude IRQs for the autoconfiguration
1796 pnp_reserve_dma=
1797 [ISAPNP] Exclude DMAs for the autoconfiguration
1799 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1800 Ranges are in pairs (I/O port base and size).
1802 pnp_reserve_mem=
1803 [ISAPNP] Exclude memory regions for the
1804 autoconfiguration.
1805 Ranges are in pairs (memory base and size).
1807 dynamic_printk Enables pr_debug()/dev_dbg() calls if
1808 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
1809 These can also be switched on/off via
1810 <debugfs>/dynamic_printk/modules
1812 print-fatal-signals=
1813 [KNL] debug: print fatal signals
1814 print-fatal-signals=1: print segfault info to
1815 the kernel console.
1816 default: off.
1818 printk.time= Show timing data prefixed to each printk message line
1819 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1821 profile= [KNL] Enable kernel profiling via /proc/profile
1822 Format: [schedule,]<number>
1823 Param: "schedule" - profile schedule points.
1824 Param: <number> - step/bucket size as a power of 2 for
1825 statistical time based profiling.
1826 Param: "sleep" - profile D-state sleeping (millisecs).
1827 Requires CONFIG_SCHEDSTATS
1828 Param: "kvm" - profile VM exits.
1830 processor.max_cstate= [HW,ACPI]
1831 Limit processor to maximum C-state
1832 max_cstate=9 overrides any DMI blacklist limit.
1834 processor.nocst [HW,ACPI]
1835 Ignore the _CST method to determine C-states,
1836 instead using the legacy FADT method
1838 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1839 before loading.
1840 See Documentation/blockdev/ramdisk.txt.
1842 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1843 probe for; one of (bare|imps|exps|lifebook|any).
1844 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1845 per second.
1846 psmouse.resetafter= [HW,MOUSE]
1847 Try to reset the device after so many bad packets
1848 (0 = never).
1849 psmouse.resolution=
1850 [HW,MOUSE] Set desired mouse resolution, in dpi.
1851 psmouse.smartscroll=
1852 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1853 0 = disabled, 1 = enabled (default).
1855 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1856 Format:
1857 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1859 pt. [PARIDE]
1860 See Documentation/blockdev/paride.txt.
1862 pty.legacy_count=
1863 [KNL] Number of legacy pty's. Overwrites compiled-in
1864 default number.
1866 quiet [KNL] Disable most log messages
1868 r128= [HW,DRM]
1870 raid= [HW,RAID]
1871 See Documentation/md.txt.
1873 ramdisk_blocksize= [RAM]
1874 See Documentation/blockdev/ramdisk.txt.
1876 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1877 See Documentation/blockdev/ramdisk.txt.
1879 rcupdate.blimit= [KNL,BOOT]
1880 Set maximum number of finished RCU callbacks to process
1881 in one batch.
1883 rcupdate.qhimark= [KNL,BOOT]
1884 Set threshold of queued
1885 RCU callbacks over which batch limiting is disabled.
1887 rcupdate.qlowmark= [KNL,BOOT]
1888 Set threshold of queued RCU callbacks below which
1889 batch limiting is re-enabled.
1891 rdinit= [KNL]
1892 Format: <full_path>
1893 Run specified binary instead of /init from the ramdisk,
1894 used for early userspace startup. See initrd.
1896 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1897 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1898 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1900 relax_domain_level=
1901 [KNL, SMP] Set scheduler's default relax_domain_level.
1902 See Documentation/cpusets.txt.
1904 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1906 reservetop= [X86-32]
1907 Format: nn[KMG]
1908 Reserves a hole at the top of the kernel virtual
1909 address space.
1911 reset_devices [KNL] Force drivers to reset the underlying device
1912 during initialization.
1914 resume= [SWSUSP]
1915 Specify the partition device for software suspend
1917 resume_offset= [SWSUSP]
1918 Specify the offset from the beginning of the partition
1919 given by "resume=" at which the swap header is located,
1920 in <PAGE_SIZE> units (needed only for swap files).
1921 See Documentation/power/swsusp-and-swap-files.txt
1923 retain_initrd [RAM] Keep initrd memory after extraction
1925 rhash_entries= [KNL,NET]
1926 Set number of hash buckets for route cache
1928 riscom8= [HW,SERIAL]
1929 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1931 ro [KNL] Mount root device read-only on boot
1933 root= [KNL] Root filesystem
1935 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1936 mount the root filesystem
1938 rootflags= [KNL] Set root filesystem mount option string
1940 rootfstype= [KNL] Set root filesystem type
1942 rootwait [KNL] Wait (indefinitely) for root device to show up.
1943 Useful for devices that are detected asynchronously
1944 (e.g. USB and MMC devices).
1946 root_plug.vendor_id=
1947 [ROOTPLUG] Override the default vendor ID
1949 root_plug.product_id=
1950 [ROOTPLUG] Override the default product ID
1952 root_plug.debug=
1953 [ROOTPLUG] Enable debugging output
1955 rw [KNL] Mount root device read-write on boot
1957 S [KNL] Run init in single mode
1959 sa1100ir [NET]
1960 See drivers/net/irda/sa1100_ir.c.
1962 sbni= [NET] Granch SBNI12 leased line adapter
1964 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1965 Format: <io>[,<timeout>[,<isapnp>]]
1967 scsi_debug_*= [SCSI]
1968 See drivers/scsi/scsi_debug.c.
1970 scsi_default_dev_flags=
1971 [SCSI] SCSI default device flags
1972 Format: <integer>
1974 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1975 Format: <vendor>:<model>:<flags>
1976 (flags are integer value)
1978 scsi_logging_level= [SCSI] a bit mask of logging levels
1979 See drivers/scsi/scsi_logging.h for bits. Also
1980 settable via sysctl at dev.scsi.logging_level
1981 (/proc/sys/dev/scsi/logging_level).
1982 There is also a nice 'scsi_logging_level' script in the
1983 S390-tools package, available for download at
1984 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1986 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1987 discovered. async scans them in kernel threads,
1988 allowing boot to proceed. none ignores them, expecting
1989 user space to do the scan.
1991 selinux [SELINUX] Disable or enable SELinux at boot time.
1992 Format: { "0" | "1" }
1993 See security/selinux/Kconfig help text.
1994 0 -- disable.
1995 1 -- enable.
1996 Default value is set via kernel config option.
1997 If enabled at boot time, /selinux/disable can be used
1998 later to disable prior to initial policy load.
2000 selinux_compat_net =
2001 [SELINUX] Set initial selinux_compat_net flag value.
2002 Format: { "0" | "1" }
2003 0 -- use new secmark-based packet controls
2004 1 -- use legacy packet controls
2005 Default value is 0 (preferred).
2006 Value can be changed at runtime via
2007 /selinux/compat_net.
2009 serialnumber [BUGS=X86-32]
2011 shapers= [NET]
2012 Maximal number of shapers.
2014 show_msr= [x86] show boot-time MSR settings
2015 Format: { <integer> }
2016 Show boot-time (BIOS-initialized) MSR settings.
2017 The parameter means the number of CPUs to show,
2018 for example 1 means boot CPU only.
2020 sim710= [SCSI,HW]
2021 See header of drivers/scsi/sim710.c.
2023 simeth= [IA-64]
2024 simscsi=
2026 slram= [HW,MTD]
2028 slub_debug[=options[,slabs]] [MM, SLUB]
2029 Enabling slub_debug allows one to determine the
2030 culprit if slab objects become corrupted. Enabling
2031 slub_debug can create guard zones around objects and
2032 may poison objects when not in use. Also tracks the
2033 last alloc / free. For more information see
2034 Documentation/vm/slub.txt.
2036 slub_max_order= [MM, SLUB]
2037 Determines the maximum allowed order for slabs.
2038 A high setting may cause OOMs due to memory
2039 fragmentation. For more information see
2040 Documentation/vm/slub.txt.
2042 slub_min_objects= [MM, SLUB]
2043 The minimum number of objects per slab. SLUB will
2044 increase the slab order up to slub_max_order to
2045 generate a sufficiently large slab able to contain
2046 the number of objects indicated. The higher the number
2047 of objects the smaller the overhead of tracking slabs
2048 and the less frequently locks need to be acquired.
2049 For more information see Documentation/vm/slub.txt.
2051 slub_min_order= [MM, SLUB]
2052 Determines the mininum page order for slabs. Must be
2053 lower than slub_max_order.
2054 For more information see Documentation/vm/slub.txt.
2056 slub_nomerge [MM, SLUB]
2057 Disable merging of slabs with similar size. May be
2058 necessary if there is some reason to distinguish
2059 allocs to different slabs. Debug options disable
2060 merging on their own.
2061 For more information see Documentation/vm/slub.txt.
2063 smart2= [HW]
2064 Format: <io1>[,<io2>[,...,<io8>]]
2066 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2067 attempt to substitute SMP alternatives once at boot.
2069 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2070 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2071 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2072 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2073 smsc-ircc2.ircc_irq= [HW] IRQ line
2074 smsc-ircc2.ircc_dma= [HW] DMA channel
2075 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2076 0: Toshiba Satellite 1800 (GP data pin select)
2077 1: Fast pin select (default)
2078 2: ATC IRMode
2080 snd-ad1816a= [HW,ALSA]
2082 snd-ad1848= [HW,ALSA]
2084 snd-ali5451= [HW,ALSA]
2086 snd-als100= [HW,ALSA]
2088 snd-als4000= [HW,ALSA]
2090 snd-azt2320= [HW,ALSA]
2092 snd-cmi8330= [HW,ALSA]
2094 snd-cmipci= [HW,ALSA]
2096 snd-cs4231= [HW,ALSA]
2098 snd-cs4232= [HW,ALSA]
2100 snd-cs4236= [HW,ALSA]
2102 snd-cs4281= [HW,ALSA]
2104 snd-cs46xx= [HW,ALSA]
2106 snd-dt019x= [HW,ALSA]
2108 snd-dummy= [HW,ALSA]
2110 snd-emu10k1= [HW,ALSA]
2112 snd-ens1370= [HW,ALSA]
2114 snd-ens1371= [HW,ALSA]
2116 snd-es968= [HW,ALSA]
2118 snd-es1688= [HW,ALSA]
2120 snd-es18xx= [HW,ALSA]
2122 snd-es1938= [HW,ALSA]
2124 snd-es1968= [HW,ALSA]
2126 snd-fm801= [HW,ALSA]
2128 snd-gusclassic= [HW,ALSA]
2130 snd-gusextreme= [HW,ALSA]
2132 snd-gusmax= [HW,ALSA]
2134 snd-hdsp= [HW,ALSA]
2136 snd-ice1712= [HW,ALSA]
2138 snd-intel8x0= [HW,ALSA]
2140 snd-interwave= [HW,ALSA]
2142 snd-interwave-stb=
2143 [HW,ALSA]
2145 snd-korg1212= [HW,ALSA]
2147 snd-maestro3= [HW,ALSA]
2149 snd-mpu401= [HW,ALSA]
2151 snd-mtpav= [HW,ALSA]
2153 snd-nm256= [HW,ALSA]
2155 snd-opl3sa2= [HW,ALSA]
2157 snd-opti92x-ad1848=
2158 [HW,ALSA]
2160 snd-opti92x-cs4231=
2161 [HW,ALSA]
2163 snd-opti93x= [HW,ALSA]
2165 snd-pmac= [HW,ALSA]
2167 snd-rme32= [HW,ALSA]
2169 snd-rme96= [HW,ALSA]
2171 snd-rme9652= [HW,ALSA]
2173 snd-sb8= [HW,ALSA]
2175 snd-sb16= [HW,ALSA]
2177 snd-sbawe= [HW,ALSA]
2179 snd-serial= [HW,ALSA]
2181 snd-sgalaxy= [HW,ALSA]
2183 snd-sonicvibes= [HW,ALSA]
2185 snd-sun-amd7930=
2186 [HW,ALSA]
2188 snd-sun-cs4231= [HW,ALSA]
2190 snd-trident= [HW,ALSA]
2192 snd-usb-audio= [HW,ALSA,USB]
2194 snd-via82xx= [HW,ALSA]
2196 snd-virmidi= [HW,ALSA]
2198 snd-wavefront= [HW,ALSA]
2200 snd-ymfpci= [HW,ALSA]
2202 softlockup_panic=
2203 [KNL] Should the soft-lockup detector generate panics.
2205 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2206 See Documentation/sonypi.txt
2208 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2209 See Documentation/serial/specialix.txt.
2211 spia_io_base= [HW,MTD]
2212 spia_fio_base=
2213 spia_pedr=
2214 spia_peddr=
2216 sscape= [HW,OSS]
2217 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2219 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2220 See Documentation/scsi/st.txt.
2222 stacktrace [FTRACE]
2223 Enabled the stack tracer on boot up.
2225 sti= [PARISC,HW]
2226 Format: <num>
2227 Set the STI (builtin display/keyboard on the HP-PARISC
2228 machines) console (graphic card) which should be used
2229 as the initial boot-console.
2230 See also comment in drivers/video/console/sticore.c.
2232 sti_font= [HW]
2233 See comment in drivers/video/console/sticore.c.
2235 stifb= [HW]
2236 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2238 sunrpc.pool_mode=
2239 [NFS]
2240 Control how the NFS server code allocates CPUs to
2241 service thread pools. Depending on how many NICs
2242 you have and where their interrupts are bound, this
2243 option will affect which CPUs will do NFS serving.
2244 Note: this parameter cannot be changed while the
2245 NFS server is running.
2247 auto the server chooses an appropriate mode
2248 automatically using heuristics
2249 global a single global pool contains all CPUs
2250 percpu one pool for each CPU
2251 pernode one pool for each NUMA node (equivalent
2252 to global on non-NUMA machines)
2254 swiotlb= [IA-64] Number of I/O TLB slabs
2256 switches= [HW,M68k]
2258 sym53c416= [HW,SCSI]
2259 See header of drivers/scsi/sym53c416.c.
2261 sysrq_always_enabled
2262 [KNL]
2263 Ignore sysrq setting - this boot parameter will
2264 neutralize any effect of /proc/sys/kernel/sysrq.
2265 Useful for debugging.
2267 t128= [HW,SCSI]
2268 See header of drivers/scsi/t128.c.
2270 tdfx= [HW,DRM]
2272 test_suspend= [SUSPEND]
2273 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2274 standby suspend) as the system sleep state to briefly
2275 enter during system startup. The system is woken from
2276 this state using a wakeup-capable RTC alarm.
2278 thash_entries= [KNL,NET]
2279 Set number of hash buckets for TCP connection
2281 thermal.act= [HW,ACPI]
2282 -1: disable all active trip points in all thermal zones
2283 <degrees C>: override all lowest active trip points
2285 thermal.crt= [HW,ACPI]
2286 -1: disable all critical trip points in all thermal zones
2287 <degrees C>: override all critical trip points
2289 thermal.nocrt= [HW,ACPI]
2290 Set to disable actions on ACPI thermal zone
2291 critical and hot trip points.
2293 thermal.off= [HW,ACPI]
2294 1: disable ACPI thermal control
2296 thermal.psv= [HW,ACPI]
2297 -1: disable all passive trip points
2298 <degrees C>: override all passive trip points to this value
2300 thermal.tzp= [HW,ACPI]
2301 Specify global default ACPI thermal zone polling rate
2302 <deci-seconds>: poll all this frequency
2303 0: no polling (default)
2305 tmscsim= [HW,SCSI]
2306 See comment before function dc390_setup() in
2307 drivers/scsi/tmscsim.c.
2309 topology= [S390]
2310 Format: {off | on}
2311 Specify if the kernel should make use of the cpu
2312 topology informations if the hardware supports these.
2313 The scheduler will make use of these informations and
2314 e.g. base its process migration decisions on it.
2315 Default is off.
2317 tp720= [HW,PS2]
2319 trix= [HW,OSS] MediaTrix AudioTrix Pro
2320 Format:
2321 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2323 tsc= Disable clocksource-must-verify flag for TSC.
2324 Format: <string>
2325 [x86] reliable: mark tsc clocksource as reliable, this
2326 disables clocksource verification at runtime.
2327 Used to enable high-resolution timer mode on older
2328 hardware, and in virtualized environment.
2330 turbografx.map[2|3]= [HW,JOY]
2331 TurboGraFX parallel port interface
2332 Format:
2333 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2334 See also Documentation/input/joystick-parport.txt
2336 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2337 See header of drivers/scsi/u14-34f.c.
2339 uart401= [HW,OSS]
2340 Format: <io>,<irq>
2342 uart6850= [HW,OSS]
2343 Format: <io>,<irq>
2345 uhci-hcd.ignore_oc=
2346 [USB] Ignore overcurrent events (default N).
2347 Some badly-designed motherboards generate lots of
2348 bogus events, for ports that aren't wired to
2349 anything. Set this parameter to avoid log spamming.
2350 Note that genuine overcurrent events won't be
2351 reported either.
2353 unknown_nmi_panic
2354 [X86-32,X86-64]
2355 Set unknown_nmi_panic=1 early on boot.
2357 usbcore.autosuspend=
2358 [USB] The autosuspend time delay (in seconds) used
2359 for newly-detected USB devices (default 2). This
2360 is the time required before an idle device will be
2361 autosuspended. Devices for which the delay is set
2362 to a negative value won't be autosuspended at all.
2364 usbcore.usbfs_snoop=
2365 [USB] Set to log all usbfs traffic (default 0 = off).
2367 usbcore.blinkenlights=
2368 [USB] Set to cycle leds on hubs (default 0 = off).
2370 usbcore.old_scheme_first=
2371 [USB] Start with the old device initialization
2372 scheme (default 0 = off).
2374 usbcore.use_both_schemes=
2375 [USB] Try the other device initialization scheme
2376 if the first one fails (default 1 = enabled).
2378 usbcore.initial_descriptor_timeout=
2379 [USB] Specifies timeout for the initial 64-byte
2380 USB_REQ_GET_DESCRIPTOR request in milliseconds
2381 (default 5000 = 5.0 seconds).
2383 usbhid.mousepoll=
2384 [USBHID] The interval which mice are to be polled at.
2386 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2387 kernel's map of available physical RAM.
2389 vdso= [X86-32,SH,x86-64]
2390 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2391 vdso=1: enable VDSO (default)
2392 vdso=0: disable VDSO mapping
2394 vdso32= [X86-32,X86-64]
2395 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2396 vdso32=1: enable 32-bit VDSO (default)
2397 vdso32=0: disable 32-bit VDSO mapping
2399 vector= [IA-64,SMP]
2400 vector=percpu: enable percpu vector domain
2402 video= [FB] Frame buffer configuration
2403 See Documentation/fb/modedb.txt.
2405 vga= [BOOT,X86-32] Select a particular video mode
2406 See Documentation/x86/i386/boot.txt and
2407 Documentation/svga.txt.
2408 Use vga=ask for menu.
2409 This is actually a boot loader parameter; the value is
2410 passed to the kernel using a special protocol.
2412 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2413 size of <nn>. This can be used to increase the
2414 minimum size (128MB on x86). It can also be used to
2415 decrease the size and leave more room for directly
2416 mapped kernel RAM.
2418 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2419 Format: <command>
2421 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2422 Format: <command>
2424 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2425 Format: <command>
2427 waveartist= [HW,OSS]
2428 Format: <io>,<irq>,<dma>,<dma2>
2430 wd33c93= [HW,SCSI]
2431 See header of drivers/scsi/wd33c93.c.
2433 wd7000= [HW,SCSI]
2434 See header of drivers/scsi/wd7000.c.
2436 wdt= [WDT] Watchdog
2437 See Documentation/watchdog/wdt.txt.
2439 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2440 xd_geo= See header of drivers/block/xd.c.
2442 xirc2ps_cs= [NET,PCMCIA]
2443 Format:
2444 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2446 norandmaps Don't use address space randomization. Equivalent to
2447 echo 0 > /proc/sys/kernel/randomize_va_space
2449 ______________________________________________________________________
2451 TODO:
2453 Add documentation for ALSA options.
2454 Add more DRM drivers.