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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 include/asm-x86/cpufeature.h for the valid bit numbers.
473 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 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
555 Format:
556 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
558 crashkernel=nn[KMG]@ss[KMG]
559 [KNL] Reserve a chunk of physical memory to
560 hold a kernel to switch to with kexec on panic.
562 crashkernel=range1:size1[,range2:size2,...][@offset]
563 [KNL] Same as above, but depends on the memory
564 in the running system. The syntax of range is
565 start-[end] where start and end are both
566 a memory unit (amount[KMG]). See also
567 Documentation/kdump/kdump.txt for a example.
569 cs4232= [HW,OSS]
570 Format: <io>,<irq>,<dma>,<dma2>,<mpuio>,<mpuirq>
572 cs89x0_dma= [HW,NET]
573 Format: <dma>
575 cs89x0_media= [HW,NET]
576 Format: { rj45 | aui | bnc }
578 dasd= [HW,NET]
579 See header of drivers/s390/block/dasd_devmap.c.
581 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
582 (one device per port)
583 Format: <port#>,<type>
584 See also Documentation/input/joystick-parport.txt
586 debug [KNL] Enable kernel debugging (events log level).
588 debug_locks_verbose=
589 [KNL] verbose self-tests
590 Format=<0|1>
591 Print debugging info while doing the locking API
592 self-tests.
593 We default to 0 (no extra messages), setting it to
594 1 will print _a lot_ more information - normally
595 only useful to kernel developers.
597 debug_objects [KNL] Enable object debugging
599 debugpat [X86] Enable PAT debugging
601 decnet.addr= [HW,NET]
602 Format: <area>[,<node>]
603 See also Documentation/networking/decnet.txt.
605 vt.default_blu= [VT]
606 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
607 Change the default blue palette of the console.
608 This is a 16-member array composed of values
609 ranging from 0-255.
611 vt.default_grn= [VT]
612 Format: <green0>,<green1>,<green2>,...,<green15>
613 Change the default green palette of the console.
614 This is a 16-member array composed of values
615 ranging from 0-255.
617 vt.default_red= [VT]
618 Format: <red0>,<red1>,<red2>,...,<red15>
619 Change the default red palette of the console.
620 This is a 16-member array composed of values
621 ranging from 0-255.
623 vt.default_utf8=
624 [VT]
625 Format=<0|1>
626 Set system-wide default UTF-8 mode for all tty's.
627 Default is 1, i.e. UTF-8 mode is enabled for all
628 newly opened terminals.
630 dhash_entries= [KNL]
631 Set number of hash buckets for dentry cache.
633 digi= [HW,SERIAL]
634 IO parameters + enable/disable command.
636 digiepca= [HW,SERIAL]
637 See drivers/char/README.epca and
638 Documentation/serial/digiepca.txt.
640 disable_mtrr_cleanup [X86]
641 enable_mtrr_cleanup [X86]
642 The kernel tries to adjust MTRR layout from continuous
643 to discrete, to make X server driver able to add WB
644 entry later. This parameter enables/disables that.
646 mtrr_chunk_size=nn[KMG] [X86]
647 used for mtrr cleanup. It is largest continous chunk
648 that could hold holes aka. UC entries.
650 mtrr_gran_size=nn[KMG] [X86]
651 Used for mtrr cleanup. It is granularity of mtrr block.
652 Default is 1.
653 Large value could prevent small alignment from
654 using up MTRRs.
656 mtrr_spare_reg_nr=n [X86]
657 Format: <integer>
658 Range: 0,7 : spare reg number
659 Default : 1
660 Used for mtrr cleanup. It is spare mtrr entries number.
661 Set to 2 or more if your graphical card needs more.
663 disable_mtrr_trim [X86, Intel and AMD only]
664 By default the kernel will trim any uncacheable
665 memory out of your available memory pool based on
666 MTRR settings. This parameter disables that behavior,
667 possibly causing your machine to run very slowly.
669 dmasound= [HW,OSS] Sound subsystem buffers
671 dscc4.setup= [NET]
673 dtc3181e= [HW,SCSI]
675 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
676 earlyprintk=vga
677 earlyprintk=serial[,ttySn[,baudrate]]
678 earlyprintk=dbgp
680 Append ",keep" to not disable it when the real console
681 takes over.
683 Only vga or serial or usb debug port at a time.
685 Currently only ttyS0 and ttyS1 are supported.
687 Interaction with the standard serial driver is not
688 very good.
690 The VGA output is eventually overwritten by the real
691 console.
693 eata= [HW,SCSI]
695 edd= [EDD]
696 Format: {"off" | "on" | "skip[mbr]"}
698 eisa_irq_edge= [PARISC,HW]
699 See header of drivers/parisc/eisa.c.
701 elanfreq= [X86-32]
702 See comment before function elanfreq_setup() in
703 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
705 elevator= [IOSCHED]
706 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
707 See Documentation/block/as-iosched.txt and
708 Documentation/block/deadline-iosched.txt for details.
710 elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
711 Specifies physical address of start of kernel core
712 image elf header. Generally kexec loader will
713 pass this option to capture kernel.
714 See Documentation/kdump/kdump.txt for details.
716 enforcing [SELINUX] Set initial enforcing status.
717 Format: {"0" | "1"}
718 See security/selinux/Kconfig help text.
719 0 -- permissive (log only, no denials).
720 1 -- enforcing (deny and log).
721 Default value is 0.
722 Value can be changed at runtime via /selinux/enforce.
724 es1371= [HW,OSS]
725 Format: <spdif>,[<nomix>,[<amplifier>]]
726 See also header of sound/oss/es1371.c.
728 ether= [HW,NET] Ethernet cards parameters
729 This option is obsoleted by the "netdev=" option, which
730 has equivalent usage. See its documentation for details.
732 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
733 Format: <io>[,<irq>]
735 failslab=
736 fail_page_alloc=
737 fail_make_request=[KNL]
738 General fault injection mechanism.
739 Format: <interval>,<probability>,<space>,<times>
740 See also /Documentation/fault-injection/.
742 fd_mcs= [HW,SCSI]
743 See header of drivers/scsi/fd_mcs.c.
745 fdomain= [HW,SCSI]
746 See header of drivers/scsi/fdomain.c.
748 floppy= [HW]
749 See Documentation/blockdev/floppy.txt.
751 force_pal_cache_flush
752 [IA-64] Avoid check_sal_cache_flush which may hang on
753 buggy SAL_CACHE_FLUSH implementations. Using this
754 parameter will force ia64_sal_cache_flush to call
755 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
757 ftrace=[tracer]
758 [ftrace] will set and start the specified tracer
759 as early as possible in order to facilitate early
760 boot debugging.
762 ftrace_dump_on_oops
763 [ftrace] will dump the trace buffers on oops.
765 gamecon.map[2|3]=
766 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
767 support via parallel port (up to 5 devices per port)
768 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
769 See also Documentation/input/joystick-parport.txt
771 gamma= [HW,DRM]
773 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
774 Format: off | on
775 default: on
777 gdth= [HW,SCSI]
778 See header of drivers/scsi/gdth.c.
780 gpt [EFI] Forces disk with valid GPT signature but
781 invalid Protective MBR to be treated as GPT.
783 gvp11= [HW,SCSI]
785 hashdist= [KNL,NUMA] Large hashes allocated during boot
786 are distributed across NUMA nodes. Defaults on
787 for IA-64, off otherwise.
788 Format: 0 | 1 (for off | on)
790 hcl= [IA-64] SGI's Hardware Graph compatibility layer
792 hd= [EIDE] (E)IDE hard drive subsystem geometry
793 Format: <cyl>,<head>,<sect>
795 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
796 size of <nn>. This works even on boxes that have no
797 highmem otherwise. This also works to reduce highmem
798 size on bigger boxes.
800 highres= [KNL] Enable/disable high resolution timer mode.
801 Valid parameters: "on", "off"
802 Default: "on"
804 hisax= [HW,ISDN]
805 See Documentation/isdn/README.HiSax.
807 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
808 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
809 On x86-64 and powerpc, this option can be specified
810 multiple times interleaved with hugepages= to reserve
811 huge pages of different sizes. Valid pages sizes on
812 x86-64 are 2M (when the CPU supports "pse") and 1G
813 (when the CPU supports the "pdpe1gb" cpuinfo flag)
814 Note that 1GB pages can only be allocated at boot time
815 using hugepages= and not freed afterwards.
816 default_hugepagesz=
817 [same as hugepagesz=] The size of the default
818 HugeTLB page size. This is the size represented by
819 the legacy /proc/ hugepages APIs, used for SHM, and
820 default size when mounting hugetlbfs filesystems.
821 Defaults to the default architecture's huge page size
822 if not specified.
824 hlt [BUGS=ARM,SH]
826 hvc_iucv= [S390] Number of z/VM IUCV Hypervisor console (HVC)
827 back-ends. Valid parameters: 0..8
829 i8042.debug [HW] Toggle i8042 debug mode
830 i8042.direct [HW] Put keyboard port into non-translated mode
831 i8042.dumbkbd [HW] Pretend that controller can only read data from
832 keyboard and cannot control its state
833 (Don't attempt to blink the leds)
834 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
835 i8042.nokbd [HW] Don't check/create keyboard port
836 i8042.noloop [HW] Disable the AUX Loopback command while probing
837 for the AUX port
838 i8042.nomux [HW] Don't check presence of an active multiplexing
839 controller
840 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
841 controllers
842 i8042.panicblink=
843 [HW] Frequency with which keyboard LEDs should blink
844 when kernel panics (default is 0.5 sec)
845 i8042.reset [HW] Reset the controller during init and cleanup
846 i8042.unlock [HW] Unlock (ignore) the keylock
848 i810= [HW,DRM]
850 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
851 indicates that the driver is running on unsupported
852 hardware.
853 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
854 does not match list of supported models.
855 i8k.power_status
856 [HW] Report power status in /proc/i8k
857 (disabled by default)
858 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
859 capability is set.
861 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
862 See Documentation/mca.txt.
864 icn= [HW,ISDN]
865 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
867 ide= [HW] (E)IDE subsystem
868 Format: ide=nodma or ide=doubler
869 See Documentation/ide/ide.txt.
871 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
872 See Documentation/ide/ide.txt.
874 idle= [X86]
875 Format: idle=poll or idle=mwait, idle=halt, idle=nomwait
876 Poll forces a polling idle loop that can slightly improves the performance
877 of waking up a idle CPU, but will use a lot of power and make the system
878 run hot. Not recommended.
879 idle=mwait. On systems which support MONITOR/MWAIT but the kernel chose
880 to not use it because it doesn't save as much power as a normal idle
881 loop use the MONITOR/MWAIT idle loop anyways. Performance should be the same
882 as idle=poll.
883 idle=halt. Halt is forced to be used for CPU idle.
884 In such case C2/C3 won't be used again.
885 idle=nomwait. Disable mwait for CPU C-states
887 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
888 Claim all unknown PCI IDE storage controllers.
890 ignore_loglevel [KNL]
891 Ignore loglevel setting - this will print /all/
892 kernel messages to the console. Useful for debugging.
894 ihash_entries= [KNL]
895 Set number of hash buckets for inode cache.
897 in2000= [HW,SCSI]
898 See header of drivers/scsi/in2000.c.
900 init= [KNL]
901 Format: <full_path>
902 Run specified binary instead of /sbin/init as init
903 process.
905 initcall_debug [KNL] Trace initcalls as they are executed. Useful
906 for working out where the kernel is dying during
907 startup.
909 initrd= [BOOT] Specify the location of the initial ramdisk
911 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
912 Format: <irq>
914 inttest= [IA64]
916 iommu= [x86]
917 off
918 force
919 noforce
920 biomerge
921 panic
922 nopanic
923 merge
924 nomerge
925 forcesac
926 soft
929 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
930 off
931 Disable intel iommu driver.
932 igfx_off [Default Off]
933 By default, gfx is mapped as normal device. If a gfx
934 device has a dedicated DMAR unit, the DMAR unit is
935 bypassed by not enabling DMAR with this option. In
936 this case, gfx device will use physical address for
937 DMA.
938 forcedac [x86_64]
939 With this option iommu will not optimize to look
940 for io virtual address below 32 bit forcing dual
941 address cycle on pci bus for cards supporting greater
942 than 32 bit addressing. The default is to look
943 for translation below 32 bit and if not available
944 then look in the higher range.
945 strict [Default Off]
946 With this option on every unmap_single operation will
947 result in a hardware IOTLB flush operation as opposed
948 to batching them for performance.
950 io_delay= [X86-32,X86-64] I/O delay method
951 0x80
952 Standard port 0x80 based delay
953 0xed
954 Alternate port 0xed based delay (needed on some systems)
955 udelay
956 Simple two microseconds delay
957 none
958 No delay
960 io7= [HW] IO7 for Marvel based alpha systems
961 See comment before marvel_specify_io7 in
962 arch/alpha/kernel/core_marvel.c.
964 ip= [IP_PNP]
965 See Documentation/filesystems/nfsroot.txt.
967 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
968 See comment before ip2_setup() in
969 drivers/char/ip2/ip2base.c.
971 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
972 See header of drivers/scsi/ips.c.
974 ports= [IP_VS_FTP] IPVS ftp helper module
975 Default is 21.
976 Up to 8 (IP_VS_APP_MAX_PORTS) ports
977 may be specified.
978 Format: <port>,<port>....
980 irqfixup [HW]
981 When an interrupt is not handled search all handlers
982 for it. Intended to get systems with badly broken
983 firmware running.
985 irqpoll [HW]
986 When an interrupt is not handled search all handlers
987 for it. Also check all handlers each timer
988 interrupt. Intended to get systems with badly broken
989 firmware running.
991 isapnp= [ISAPNP]
992 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
994 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
995 Format:
996 <cpu number>,...,<cpu number>
997 or
998 <cpu number>-<cpu number>
999 (must be a positive range in ascending order)
1000 or a mixture
1001 <cpu number>,...,<cpu number>-<cpu number>
1003 This option can be used to specify one or more CPUs
1004 to isolate from the general SMP balancing and scheduling
1005 algorithms. You can move a process onto or off an
1006 "isolated" CPU via the CPU affinity syscalls or cpuset.
1007 <cpu number> begins at 0 and the maximum value is
1008 "number of CPUs in system - 1".
1010 This option is the preferred way to isolate CPUs. The
1011 alternative -- manually setting the CPU mask of all
1012 tasks in the system -- can cause problems and
1013 suboptimal load balancer performance.
1015 iucv= [HW,NET]
1017 js= [HW,JOY] Analog joystick
1018 See Documentation/input/joystick.txt.
1020 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1021 specifies the amount of memory usable by the kernel
1022 for non-movable allocations. The requested amount is
1023 spread evenly throughout all nodes in the system. The
1024 remaining memory in each node is used for Movable
1025 pages. In the event, a node is too small to have both
1026 kernelcore and Movable pages, kernelcore pages will
1027 take priority and other nodes will have a larger number
1028 of kernelcore pages. The Movable zone is used for the
1029 allocation of pages that may be reclaimed or moved
1030 by the page migration subsystem. This means that
1031 HugeTLB pages may not be allocated from this zone.
1032 Note that allocations like PTEs-from-HighMem still
1033 use the HighMem zone if it exists, and the Normal
1034 zone if it does not.
1036 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1037 is similar to kernelcore except it specifies the
1038 amount of memory used for migratable allocations.
1039 If both kernelcore and movablecore is specified,
1040 then kernelcore will be at *least* the specified
1041 value but may be more. If movablecore on its own
1042 is specified, the administrator must be careful
1043 that the amount of memory usable for all allocations
1044 is not too small.
1046 keepinitrd [HW,ARM]
1048 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1049 in oops dumps.
1051 kgdboc= [HW] kgdb over consoles.
1052 Requires a tty driver that supports console polling.
1053 (only serial suported for now)
1054 Format: <serial_device>[,baud]
1056 kmac= [MIPS] korina ethernet MAC address.
1057 Configure the RouterBoard 532 series on-chip
1058 Ethernet adapter MAC address.
1060 l2cr= [PPC]
1062 l3cr= [PPC]
1064 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1065 disabled it.
1067 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer in
1068 C2 power state.
1070 libata.dma= [LIBATA] DMA control
1071 libata.dma=0 Disable all PATA and SATA DMA
1072 libata.dma=1 PATA and SATA Disk DMA only
1073 libata.dma=2 ATAPI (CDROM) DMA only
1074 libata.dma=4 Compact Flash DMA only
1075 Combinations also work, so libata.dma=3 enables DMA
1076 for disks and CDROMs, but not CFs.
1078 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1079 when set.
1080 Format: <int>
1082 libata.force= [LIBATA] Force configurations. The format is comma
1083 separated list of "[ID:]VAL" where ID is
1084 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1085 matching port, link or device. Basically, it matches
1086 the ATA ID string printed on console by libata. If
1087 the whole ID part is omitted, the last PORT and DEVICE
1088 values are used. If ID hasn't been specified yet, the
1089 configuration applies to all ports, links and devices.
1091 If only DEVICE is omitted, the parameter applies to
1092 the port and all links and devices behind it. DEVICE
1093 number of 0 either selects the first device or the
1094 first fan-out link behind PMP device. It does not
1095 select the host link. DEVICE number of 15 selects the
1096 host link and device attached to it.
1098 The VAL specifies the configuration to force. As long
1099 as there's no ambiguity shortcut notation is allowed.
1100 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1101 The following configurations can be forced.
1103 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1104 Any ID with matching PORT is used.
1106 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1108 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1109 udma[/][16,25,33,44,66,100,133] notation is also
1110 allowed.
1112 * [no]ncq: Turn on or off NCQ.
1114 * nohrst, nosrst, norst: suppress hard, soft
1115 and both resets.
1117 If there are multiple matching configurations changing
1118 the same attribute, the last one is used.
1120 load_ramdisk= [RAM] List of ramdisks to load from floppy
1121 See Documentation/blockdev/ramdisk.txt.
1123 lockd.nlm_grace_period=P [NFS] Assign grace period.
1124 Format: <integer>
1126 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1127 Format: <integer>
1129 lockd.nlm_timeout=T [NFS] Assign timeout value.
1130 Format: <integer>
1132 lockd.nlm_udpport=M [NFS] Assign UDP port.
1133 Format: <integer>
1135 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1136 Format: <irq>
1138 loglevel= All Kernel Messages with a loglevel smaller than the
1139 console loglevel will be printed to the console. It can
1140 also be changed with klogd or other programs. The
1141 loglevels are defined as follows:
1143 0 (KERN_EMERG) system is unusable
1144 1 (KERN_ALERT) action must be taken immediately
1145 2 (KERN_CRIT) critical conditions
1146 3 (KERN_ERR) error conditions
1147 4 (KERN_WARNING) warning conditions
1148 5 (KERN_NOTICE) normal but significant condition
1149 6 (KERN_INFO) informational
1150 7 (KERN_DEBUG) debug-level messages
1152 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1153 Format: { n | nk | nM }
1154 n must be a power of two. The default size
1155 is set in the kernel config file.
1157 logo.nologo [FB] Disables display of the built-in Linux logo.
1158 This may be used to provide more screen space for
1159 kernel log messages and is useful when debugging
1160 kernel boot problems.
1162 lp=0 [LP] Specify parallel ports to use, e.g,
1163 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1164 lp=reset first parallel port). 'lp=0' disables the
1165 lp=auto printer driver. 'lp=reset' (which can be
1166 specified in addition to the ports) causes
1167 attached printers to be reset. Using
1168 lp=port1,port2,... specifies the parallel ports
1169 to associate lp devices with, starting with
1170 lp0. A port specification may be 'none' to skip
1171 that lp device, or a parport name such as
1172 'parport0'. Specifying 'lp=auto' instead of a
1173 port specification list means that device IDs
1174 from each port should be examined, to see if
1175 an IEEE 1284-compliant printer is attached; if
1176 so, the driver will manage that printer.
1177 See also header of drivers/char/lp.c.
1179 lpj=n [KNL]
1180 Sets loops_per_jiffy to given constant, thus avoiding
1181 time-consuming boot-time autodetection (up to 250 ms per
1182 CPU). 0 enables autodetection (default). To determine
1183 the correct value for your kernel, boot with normal
1184 autodetection and see what value is printed. Note that
1185 on SMP systems the preset will be applied to all CPUs,
1186 which is likely to cause problems if your CPUs need
1187 significantly divergent settings. An incorrect value
1188 will cause delays in the kernel to be wrong, leading to
1189 unpredictable I/O errors and other breakage. Although
1190 unlikely, in the extreme case this might damage your
1191 hardware.
1193 ltpc= [NET]
1194 Format: <io>,<irq>,<dma>
1196 mac5380= [HW,SCSI] Format:
1197 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1199 machvec= [IA64] Force the use of a particular machine-vector
1200 (machvec) in a generic kernel.
1201 Example: machvec=hpzx1_swiotlb
1203 max_loop= [LOOP] Maximum number of loopback devices that can
1204 be mounted
1205 Format: <1-256>
1207 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1208 should make use of. maxcpus=n : n >= 0 limits the
1209 kernel to using 'n' processors. n=0 is a special case,
1210 it is equivalent to "nosmp", which also disables
1211 the IO APIC.
1213 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than
1214 or equal to this physical address is ignored.
1216 max_luns= [SCSI] Maximum number of LUNs to probe.
1217 Should be between 1 and 2^32-1.
1219 max_report_luns=
1220 [SCSI] Maximum number of LUNs received.
1221 Should be between 1 and 16384.
1223 mcatest= [IA-64]
1225 mce [X86-32] Machine Check Exception
1227 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1229 md= [HW] RAID subsystems devices and level
1230 See Documentation/md.txt.
1232 mdacon= [MDA]
1233 Format: <first>,<last>
1234 Specifies range of consoles to be captured by the MDA.
1236 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1237 Amount of memory to be used when the kernel is not able
1238 to see the whole system memory or for test.
1239 [X86-32] Use together with memmap= to avoid physical
1240 address space collisions. Without memmap= PCI devices
1241 could be placed at addresses belonging to unused RAM.
1243 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1244 memory.
1246 memchunk=nn[KMG]
1247 [KNL,SH] Allow user to override the default size for
1248 per-device physically contiguous DMA buffers.
1250 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1251 E820 memory map, as specified by the user.
1252 Such memmap=exactmap lines can be constructed based on
1253 BIOS output or other requirements. See the memmap=nn@ss
1254 option description.
1256 memmap=nn[KMG]@ss[KMG]
1257 [KNL] Force usage of a specific region of memory
1258 Region of memory to be used, from ss to ss+nn.
1260 memmap=nn[KMG]#ss[KMG]
1261 [KNL,ACPI] Mark specific memory as ACPI data.
1262 Region of memory to be used, from ss to ss+nn.
1264 memmap=nn[KMG]$ss[KMG]
1265 [KNL,ACPI] Mark specific memory as reserved.
1266 Region of memory to be used, from ss to ss+nn.
1267 Example: Exclude memory from 0x18690000-0x1869ffff
1268 memmap=64K$0x18690000
1269 or
1270 memmap=0x10000$0x18690000
1272 memory_corruption_check=0/1 [X86]
1273 Some BIOSes seem to corrupt the first 64k of
1274 memory when doing things like suspend/resume.
1275 Setting this option will scan the memory
1276 looking for corruption. Enabling this will
1277 both detect corruption and prevent the kernel
1278 from using the memory being corrupted.
1279 However, its intended as a diagnostic tool; if
1280 repeatable BIOS-originated corruption always
1281 affects the same memory, you can use memmap=
1282 to prevent the kernel from using that memory.
1284 memory_corruption_check_size=size [X86]
1285 By default it checks for corruption in the low
1286 64k, making this memory unavailable for normal
1287 use. Use this parameter to scan for
1288 corruption in more or less memory.
1290 memory_corruption_check_period=seconds [X86]
1291 By default it checks for corruption every 60
1292 seconds. Use this parameter to check at some
1293 other rate. 0 disables periodic checking.
1295 memtest= [KNL,X86] Enable memtest
1296 Format: <integer>
1297 range: 0,4 : pattern number
1298 default : 0 <disable>
1300 meye.*= [HW] Set MotionEye Camera parameters
1301 See Documentation/video4linux/meye.txt.
1303 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1304 Multi-Function General Purpose Timers on AMD Geode
1305 platforms.
1307 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1308 the BIOS has incorrectly applied a workaround. TinyBIOS
1309 version 0.98 is known to be affected, 0.99 fixes the
1310 problem by letting the user disable the workaround.
1312 mga= [HW,DRM]
1314 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1315 physical address is ignored.
1317 mminit_loglevel=
1318 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1319 parameter allows control of the logging verbosity for
1320 the additional memory initialisation checks. A value
1321 of 0 disables mminit logging and a level of 4 will
1322 log everything. Information is printed at KERN_DEBUG
1323 so loglevel=8 may also need to be specified.
1325 mousedev.tap_time=
1326 [MOUSE] Maximum time between finger touching and
1327 leaving touchpad surface for touch to be considered
1328 a tap and be reported as a left button click (for
1329 touchpads working in absolute mode only).
1330 Format: <msecs>
1331 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1332 reporting absolute coordinates, such as tablets
1333 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1334 reporting absolute coordinates, such as tablets
1336 mpu401= [HW,OSS]
1337 Format: <io>,<irq>
1339 MTD_Partition= [MTD]
1340 Format: <name>,<region-number>,<size>,<offset>
1342 MTD_Region= [MTD] Format:
1343 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1345 mtdparts= [MTD]
1346 See drivers/mtd/cmdlinepart.c.
1348 mtdset= [ARM]
1349 ARM/S3C2412 JIVE boot control
1351 See arch/arm/mach-s3c2412/mach-jive.c
1353 mtouchusb.raw_coordinates=
1354 [HW] Make the MicroTouch USB driver use raw coordinates
1355 ('y', default) or cooked coordinates ('n')
1357 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1359 NCR_D700= [HW,SCSI]
1360 See header of drivers/scsi/NCR_D700.c.
1362 ncr5380= [HW,SCSI]
1364 ncr53c400= [HW,SCSI]
1366 ncr53c400a= [HW,SCSI]
1368 ncr53c406a= [HW,SCSI]
1370 ncr53c8xx= [HW,SCSI]
1372 netdev= [NET] Network devices parameters
1373 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1374 Note that mem_start is often overloaded to mean
1375 something different and driver-specific.
1376 This usage is only documented in each driver source
1377 file if at all.
1379 nf_conntrack.acct=
1380 [NETFILTER] Enable connection tracking flow accounting
1381 0 to disable accounting
1382 1 to enable accounting
1383 Default value depends on CONFIG_NF_CT_ACCT that is
1384 going to be removed in 2.6.29.
1386 nfsaddrs= [NFS]
1387 See Documentation/filesystems/nfsroot.txt.
1389 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1390 See Documentation/filesystems/nfsroot.txt.
1392 nfs.callback_tcpport=
1393 [NFS] set the TCP port on which the NFSv4 callback
1394 channel should listen.
1396 nfs.idmap_cache_timeout=
1397 [NFS] set the maximum lifetime for idmapper cache
1398 entries.
1400 nfs.enable_ino64=
1401 [NFS] enable 64-bit inode numbers.
1402 If zero, the NFS client will fake up a 32-bit inode
1403 number for the readdir() and stat() syscalls instead
1404 of returning the full 64-bit number.
1405 The default is to return 64-bit inode numbers.
1407 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1408 when a NMI is triggered.
1409 Format: [state][,regs][,debounce][,die]
1411 nmi_watchdog= [KNL,BUGS=X86-32,X86-64] Debugging features for SMP kernels
1412 Format: [panic,][num]
1413 Valid num: 0,1,2
1414 0 - turn nmi_watchdog off
1415 1 - use the IO-APIC timer for the NMI watchdog
1416 2 - use the local APIC for the NMI watchdog using
1417 a performance counter. Note: This will use one performance
1418 counter and the local APIC's performance vector.
1419 When panic is specified panic when an NMI watchdog timeout occurs.
1420 This is useful when you use a panic=... timeout and need the box
1421 quickly up again.
1422 Instead of 1 and 2 it is possible to use the following
1423 symbolic names: lapic and ioapic
1424 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1426 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1427 emulation library even if a 387 maths coprocessor
1428 is present.
1430 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1431 caches in the slab allocator. Saves per-node memory,
1432 but will impact performance.
1434 noalign [KNL,ARM]
1436 noapic [SMP,APIC] Tells the kernel to not make use of any
1437 IOAPICs that may be present in the system.
1439 nobats [PPC] Do not use BATs for mapping kernel lowmem
1440 on "Classic" PPC cores.
1442 nocache [ARM]
1444 nodelayacct [KNL] Disable per-task delay accounting
1446 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1448 nodsp [SH] Disable hardware DSP at boot time.
1450 noefi [X86-32,X86-64] Disable EFI runtime services support.
1452 noexec [IA-64]
1454 noexec [X86-32,X86-64]
1455 On X86-32 available only on PAE configured kernels.
1456 noexec=on: enable non-executable mappings (default)
1457 noexec=off: disable non-executable mappings
1459 noexec32 [X86-64]
1460 This affects only 32-bit executables.
1461 noexec32=on: enable non-executable mappings (default)
1462 read doesn't imply executable mappings
1463 noexec32=off: disable non-executable mappings
1464 read implies executable mappings
1466 nofpu [SH] Disable hardware FPU at boot time.
1468 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1469 register save and restore. The kernel will only save
1470 legacy floating-point registers on task switch.
1472 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1474 nohlt [BUGS=ARM,SH]
1476 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1477 instruction doesn't work correctly and not to
1478 use it.
1480 no_file_caps Tells the kernel not to honor file capabilities. The
1481 only way then for a file to be executed with privilege
1482 is to be setuid root or executed by root.
1484 nohalt [IA-64] Tells the kernel not to use the power saving
1485 function PAL_HALT_LIGHT when idle. This increases
1486 power-consumption. On the positive side, it reduces
1487 interrupt wake-up latency, which may improve performance
1488 in certain environments such as networked servers or
1489 real-time systems.
1491 nohz= [KNL] Boottime enable/disable dynamic ticks
1492 Valid arguments: on, off
1493 Default: on
1495 noirqdebug [X86-32] Disables the code which attempts to detect and
1496 disable unhandled interrupt sources.
1498 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1499 broken timer IRQ sources.
1501 noisapnp [ISAPNP] Disables ISA PnP code.
1503 noinitrd [RAM] Tells the kernel not to load any configured
1504 initial RAM disk.
1506 nointroute [IA-64]
1508 nojitter [IA64] Disables jitter checking for ITC timers.
1510 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1512 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1514 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1516 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
1517 default x2apic cluster mode on platforms
1518 supporting x2apic.
1520 noltlbs [PPC] Do not use large page/tlb entries for kernel
1521 lowmem mapping on PPC40x.
1523 nomca [IA-64] Disable machine check abort handling
1525 nomce [X86-32] Machine Check Exception
1527 nomfgpt [X86-32] Disable Multi-Function General Purpose
1528 Timer usage (for AMD Geode machines).
1530 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1532 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1533 with UP alternatives
1535 noresidual [PPC] Don't use residual data on PReP machines.
1537 noresume [SWSUSP] Disables resume and restores original swap
1538 space.
1540 no-scroll [VGA] Disables scrollback.
1541 This is required for the Braillex ib80-piezo Braille
1542 reader made by F.H. Papenmeier (Germany).
1544 nosbagart [IA-64]
1546 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1548 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1549 and disable the IO APIC. legacy for "maxcpus=0".
1551 nosoftlockup [KNL] Disable the soft-lockup detector.
1553 nosync [HW,M68K] Disables sync negotiation for all devices.
1555 notsc [BUGS=X86-32] Disable Time Stamp Counter
1557 nousb [USB] Disable the USB subsystem
1559 nowb [ARM]
1561 nptcg= [IA64] Override max number of concurrent global TLB
1562 purges which is reported from either PAL_VM_SUMMARY or
1563 SAL PALO.
1565 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1566 one of ['zone', 'node', 'default'] can be specified
1567 This can be set from sysctl after boot.
1568 See Documentation/sysctl/vm.txt for details.
1570 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1572 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1573 Rather than timing out after 20 ms if an EC
1574 command is not properly ACKed, override the length
1575 of the timeout. We have interrupts disabled while
1576 waiting for the ACK, so if this is set too high
1577 interrupts *may* be lost!
1579 opl3= [HW,OSS]
1580 Format: <io>
1582 oprofile.timer= [HW]
1583 Use timer interrupt instead of performance counters
1585 osst= [HW,SCSI] SCSI Tape Driver
1586 Format: <buffer_size>,<write_threshold>
1587 See also Documentation/scsi/st.txt.
1589 panic= [KNL] Kernel behaviour on panic
1590 Format: <timeout>
1592 parkbd.port= [HW] Parallel port number the keyboard adapter is
1593 connected to, default is 0.
1594 Format: <parport#>
1595 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1596 0 for XT, 1 for AT (default is AT).
1597 Format: <mode>
1599 parport= [HW,PPT] Specify parallel ports. 0 disables.
1600 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1601 Use 'auto' to force the driver to use any
1602 IRQ/DMA settings detected (the default is to
1603 ignore detected IRQ/DMA settings because of
1604 possible conflicts). You can specify the base
1605 address, IRQ, and DMA settings; IRQ and DMA
1606 should be numbers, or 'auto' (for using detected
1607 settings on that particular port), or 'nofifo'
1608 (to avoid using a FIFO even if it is detected).
1609 Parallel ports are assigned in the order they
1610 are specified on the command line, starting
1611 with parport0.
1613 parport_init_mode= [HW,PPT]
1614 Configure VIA parallel port to operate in
1615 a specific mode. This is necessary on Pegasos
1616 computer where firmware has no options for setting
1617 up parallel port mode and sets it to spp.
1618 Currently this function knows 686a and 8231 chips.
1619 Format: [spp|ps2|epp|ecp|ecpepp]
1621 pas2= [HW,OSS] Format:
1622 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1624 pas16= [HW,SCSI]
1625 See header of drivers/scsi/pas16.c.
1627 pause_on_oops=
1628 Halt all CPUs after the first oops has been printed for
1629 the specified number of seconds. This is to be used if
1630 your oopses keep scrolling off the screen.
1632 pcbit= [HW,ISDN]
1634 pcd. [PARIDE]
1635 See header of drivers/block/paride/pcd.c.
1636 See also Documentation/blockdev/paride.txt.
1638 pci=option[,option...] [PCI] various PCI subsystem options:
1639 off [X86] don't probe for the PCI bus
1640 bios [X86-32] force use of PCI BIOS, don't access
1641 the hardware directly. Use this if your machine
1642 has a non-standard PCI host bridge.
1643 nobios [X86-32] disallow use of PCI BIOS, only direct
1644 hardware access methods are allowed. Use this
1645 if you experience crashes upon bootup and you
1646 suspect they are caused by the BIOS.
1647 conf1 [X86] Force use of PCI Configuration
1648 Mechanism 1.
1649 conf2 [X86] Force use of PCI Configuration
1650 Mechanism 2.
1651 noaer [PCIE] If the PCIEAER kernel config parameter is
1652 enabled, this kernel boot option can be used to
1653 disable the use of PCIE advanced error reporting.
1654 nodomains [PCI] Disable support for multiple PCI
1655 root domains (aka PCI segments, in ACPI-speak).
1656 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1657 Configuration
1658 nomsi [MSI] If the PCI_MSI kernel config parameter is
1659 enabled, this kernel boot option can be used to
1660 disable the use of MSI interrupts system-wide.
1661 noioapicquirk [APIC] Disable all boot interrupt quirks.
1662 Safety option to keep boot IRQs enabled. This
1663 should never be necessary.
1664 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1665 primary IO-APIC for bridges that cannot disable
1666 boot IRQs. This fixes a source of spurious IRQs
1667 when the system masks IRQs.
1668 noioapicreroute [APIC] Disable workaround that uses the
1669 boot IRQ equivalent of an IRQ that connects to
1670 a chipset where boot IRQs cannot be disabled.
1671 The opposite of ioapicreroute.
1672 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1673 routing table. These calls are known to be buggy
1674 on several machines and they hang the machine
1675 when used, but on other computers it's the only
1676 way to get the interrupt routing table. Try
1677 this option if the kernel is unable to allocate
1678 IRQs or discover secondary PCI buses on your
1679 motherboard.
1680 rom [X86] Assign address space to expansion ROMs.
1681 Use with caution as certain devices share
1682 address decoders between ROMs and other
1683 resources.
1684 norom [X86] Do not assign address space to
1685 expansion ROMs that do not already have
1686 BIOS assigned address ranges.
1687 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1688 assigned automatically to PCI devices. You can
1689 make the kernel exclude IRQs of your ISA cards
1690 this way.
1691 pirqaddr=0xAAAAA [X86] Specify the physical address
1692 of the PIRQ table (normally generated
1693 by the BIOS) if it is outside the
1694 F0000h-100000h range.
1695 lastbus=N [X86] Scan all buses thru bus #N. Can be
1696 useful if the kernel is unable to find your
1697 secondary buses and you want to tell it
1698 explicitly which ones they are.
1699 assign-busses [X86] Always assign all PCI bus
1700 numbers ourselves, overriding
1701 whatever the firmware may have done.
1702 usepirqmask [X86] Honor the possible IRQ mask stored
1703 in the BIOS $PIR table. This is needed on
1704 some systems with broken BIOSes, notably
1705 some HP Pavilion N5400 and Omnibook XE3
1706 notebooks. This will have no effect if ACPI
1707 IRQ routing is enabled.
1708 noacpi [X86] Do not use ACPI for IRQ routing
1709 or for PCI scanning.
1710 use_crs [X86] Use _CRS for PCI resource
1711 allocation.
1712 routeirq Do IRQ routing for all PCI devices.
1713 This is normally done in pci_enable_device(),
1714 so this option is a temporary workaround
1715 for broken drivers that don't call it.
1716 skip_isa_align [X86] do not align io start addr, so can
1717 handle more pci cards
1718 firmware [ARM] Do not re-enumerate the bus but instead
1719 just use the configuration from the
1720 bootloader. This is currently used on
1721 IXP2000 systems where the bus has to be
1722 configured a certain way for adjunct CPUs.
1723 noearly [X86] Don't do any early type 1 scanning.
1724 This might help on some broken boards which
1725 machine check when some devices' config space
1726 is read. But various workarounds are disabled
1727 and some IOMMU drivers will not work.
1728 bfsort Sort PCI devices into breadth-first order.
1729 This sorting is done to get a device
1730 order compatible with older (<= 2.4) kernels.
1731 nobfsort Don't sort PCI devices into breadth-first order.
1732 cbiosize=nn[KMG] The fixed amount of bus space which is
1733 reserved for the CardBus bridge's IO window.
1734 The default value is 256 bytes.
1735 cbmemsize=nn[KMG] The fixed amount of bus space which is
1736 reserved for the CardBus bridge's memory
1737 window. The default value is 64 megabytes.
1739 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1740 Management.
1741 off Disable ASPM.
1742 force Enable ASPM even on devices that claim not to support it.
1743 WARNING: Forcing ASPM on may cause system lockups.
1745 pcmv= [HW,PCMCIA] BadgePAD 4
1747 pd. [PARIDE]
1748 See Documentation/blockdev/paride.txt.
1750 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1751 boot time.
1752 Format: { 0 | 1 }
1753 See arch/parisc/kernel/pdc_chassis.c
1755 pf. [PARIDE]
1756 See Documentation/blockdev/paride.txt.
1758 pg. [PARIDE]
1759 See Documentation/blockdev/paride.txt.
1761 pirq= [SMP,APIC] Manual mp-table setup
1762 See Documentation/x86/i386/IO-APIC.txt.
1764 plip= [PPT,NET] Parallel port network link
1765 Format: { parport<nr> | timid | 0 }
1766 See also Documentation/parport.txt.
1768 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1769 Override pmtimer IOPort with a hex value.
1770 e.g. pmtmr=0x508
1772 pnp.debug [PNP]
1773 Enable PNP debug messages. This depends on the
1774 CONFIG_PNP_DEBUG_MESSAGES option.
1776 pnpacpi= [ACPI]
1777 { off }
1779 pnpbios= [ISAPNP]
1780 { on | off | curr | res | no-curr | no-res }
1782 pnp_reserve_irq=
1783 [ISAPNP] Exclude IRQs for the autoconfiguration
1785 pnp_reserve_dma=
1786 [ISAPNP] Exclude DMAs for the autoconfiguration
1788 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1789 Ranges are in pairs (I/O port base and size).
1791 pnp_reserve_mem=
1792 [ISAPNP] Exclude memory regions for the
1793 autoconfiguration.
1794 Ranges are in pairs (memory base and size).
1796 dynamic_printk
1797 Enables pr_debug()/dev_dbg() calls if
1798 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled. These can also
1799 be switched on/off via <debugfs>/dynamic_printk/modules
1801 print-fatal-signals=
1802 [KNL] debug: print fatal signals
1803 print-fatal-signals=1: print segfault info to
1804 the kernel console.
1805 default: off.
1807 printk.time= Show timing data prefixed to each printk message line
1808 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1810 profile= [KNL] Enable kernel profiling via /proc/profile
1811 Format: [schedule,]<number>
1812 Param: "schedule" - profile schedule points.
1813 Param: <number> - step/bucket size as a power of 2 for
1814 statistical time based profiling.
1815 Param: "sleep" - profile D-state sleeping (millisecs).
1816 Requires CONFIG_SCHEDSTATS
1817 Param: "kvm" - profile VM exits.
1819 processor.max_cstate= [HW,ACPI]
1820 Limit processor to maximum C-state
1821 max_cstate=9 overrides any DMI blacklist limit.
1823 processor.nocst [HW,ACPI]
1824 Ignore the _CST method to determine C-states,
1825 instead using the legacy FADT method
1827 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1828 before loading.
1829 See Documentation/blockdev/ramdisk.txt.
1831 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1832 probe for; one of (bare|imps|exps|lifebook|any).
1833 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1834 per second.
1835 psmouse.resetafter= [HW,MOUSE]
1836 Try to reset the device after so many bad packets
1837 (0 = never).
1838 psmouse.resolution=
1839 [HW,MOUSE] Set desired mouse resolution, in dpi.
1840 psmouse.smartscroll=
1841 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1842 0 = disabled, 1 = enabled (default).
1844 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1845 Format:
1846 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1848 pt. [PARIDE]
1849 See Documentation/blockdev/paride.txt.
1851 pty.legacy_count=
1852 [KNL] Number of legacy pty's. Overwrites compiled-in
1853 default number.
1855 quiet [KNL] Disable most log messages
1857 r128= [HW,DRM]
1859 raid= [HW,RAID]
1860 See Documentation/md.txt.
1862 ramdisk_blocksize= [RAM]
1863 See Documentation/blockdev/ramdisk.txt.
1865 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1866 See Documentation/blockdev/ramdisk.txt.
1868 rcupdate.blimit= [KNL,BOOT]
1869 Set maximum number of finished RCU callbacks to process
1870 in one batch.
1872 rcupdate.qhimark= [KNL,BOOT]
1873 Set threshold of queued
1874 RCU callbacks over which batch limiting is disabled.
1876 rcupdate.qlowmark= [KNL,BOOT]
1877 Set threshold of queued RCU callbacks below which
1878 batch limiting is re-enabled.
1880 rdinit= [KNL]
1881 Format: <full_path>
1882 Run specified binary instead of /init from the ramdisk,
1883 used for early userspace startup. See initrd.
1885 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1886 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1887 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1889 relax_domain_level=
1890 [KNL, SMP] Set scheduler's default relax_domain_level.
1891 See Documentation/cpusets.txt.
1893 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1895 reservetop= [X86-32]
1896 Format: nn[KMG]
1897 Reserves a hole at the top of the kernel virtual
1898 address space.
1900 reset_devices [KNL] Force drivers to reset the underlying device
1901 during initialization.
1903 resume= [SWSUSP]
1904 Specify the partition device for software suspend
1906 resume_offset= [SWSUSP]
1907 Specify the offset from the beginning of the partition
1908 given by "resume=" at which the swap header is located,
1909 in <PAGE_SIZE> units (needed only for swap files).
1910 See Documentation/power/swsusp-and-swap-files.txt
1912 retain_initrd [RAM] Keep initrd memory after extraction
1914 rhash_entries= [KNL,NET]
1915 Set number of hash buckets for route cache
1917 riscom8= [HW,SERIAL]
1918 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1920 ro [KNL] Mount root device read-only on boot
1922 root= [KNL] Root filesystem
1924 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1925 mount the root filesystem
1927 rootflags= [KNL] Set root filesystem mount option string
1929 rootfstype= [KNL] Set root filesystem type
1931 rootwait [KNL] Wait (indefinitely) for root device to show up.
1932 Useful for devices that are detected asynchronously
1933 (e.g. USB and MMC devices).
1935 root_plug.vendor_id=
1936 [ROOTPLUG] Override the default vendor ID
1938 root_plug.product_id=
1939 [ROOTPLUG] Override the default product ID
1941 root_plug.debug=
1942 [ROOTPLUG] Enable debugging output
1944 rw [KNL] Mount root device read-write on boot
1946 S [KNL] Run init in single mode
1948 sa1100ir [NET]
1949 See drivers/net/irda/sa1100_ir.c.
1951 sbni= [NET] Granch SBNI12 leased line adapter
1953 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1954 Format: <io>[,<timeout>[,<isapnp>]]
1956 scsi_debug_*= [SCSI]
1957 See drivers/scsi/scsi_debug.c.
1959 scsi_default_dev_flags=
1960 [SCSI] SCSI default device flags
1961 Format: <integer>
1963 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1964 Format: <vendor>:<model>:<flags>
1965 (flags are integer value)
1967 scsi_logging_level= [SCSI] a bit mask of logging levels
1968 See drivers/scsi/scsi_logging.h for bits. Also
1969 settable via sysctl at dev.scsi.logging_level
1970 (/proc/sys/dev/scsi/logging_level).
1971 There is also a nice 'scsi_logging_level' script in the
1972 S390-tools package, available for download at
1973 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1975 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1976 discovered. async scans them in kernel threads,
1977 allowing boot to proceed. none ignores them, expecting
1978 user space to do the scan.
1980 selinux [SELINUX] Disable or enable SELinux at boot time.
1981 Format: { "0" | "1" }
1982 See security/selinux/Kconfig help text.
1983 0 -- disable.
1984 1 -- enable.
1985 Default value is set via kernel config option.
1986 If enabled at boot time, /selinux/disable can be used
1987 later to disable prior to initial policy load.
1989 selinux_compat_net =
1990 [SELINUX] Set initial selinux_compat_net flag value.
1991 Format: { "0" | "1" }
1992 0 -- use new secmark-based packet controls
1993 1 -- use legacy packet controls
1994 Default value is 0 (preferred).
1995 Value can be changed at runtime via
1996 /selinux/compat_net.
1998 serialnumber [BUGS=X86-32]
2000 shapers= [NET]
2001 Maximal number of shapers.
2003 show_msr= [x86] show boot-time MSR settings
2004 Format: { <integer> }
2005 Show boot-time (BIOS-initialized) MSR settings.
2006 The parameter means the number of CPUs to show,
2007 for example 1 means boot CPU only.
2009 sim710= [SCSI,HW]
2010 See header of drivers/scsi/sim710.c.
2012 simeth= [IA-64]
2013 simscsi=
2015 slram= [HW,MTD]
2017 slub_debug[=options[,slabs]] [MM, SLUB]
2018 Enabling slub_debug allows one to determine the
2019 culprit if slab objects become corrupted. Enabling
2020 slub_debug can create guard zones around objects and
2021 may poison objects when not in use. Also tracks the
2022 last alloc / free. For more information see
2023 Documentation/vm/slub.txt.
2025 slub_max_order= [MM, SLUB]
2026 Determines the maximum allowed order for slabs.
2027 A high setting may cause OOMs due to memory
2028 fragmentation. For more information see
2029 Documentation/vm/slub.txt.
2031 slub_min_objects= [MM, SLUB]
2032 The minimum number of objects per slab. SLUB will
2033 increase the slab order up to slub_max_order to
2034 generate a sufficiently large slab able to contain
2035 the number of objects indicated. The higher the number
2036 of objects the smaller the overhead of tracking slabs
2037 and the less frequently locks need to be acquired.
2038 For more information see Documentation/vm/slub.txt.
2040 slub_min_order= [MM, SLUB]
2041 Determines the mininum page order for slabs. Must be
2042 lower than slub_max_order.
2043 For more information see Documentation/vm/slub.txt.
2045 slub_nomerge [MM, SLUB]
2046 Disable merging of slabs with similar size. May be
2047 necessary if there is some reason to distinguish
2048 allocs to different slabs. Debug options disable
2049 merging on their own.
2050 For more information see Documentation/vm/slub.txt.
2052 smart2= [HW]
2053 Format: <io1>[,<io2>[,...,<io8>]]
2055 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2056 attempt to substitute SMP alternatives once at boot.
2058 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2059 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2060 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2061 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2062 smsc-ircc2.ircc_irq= [HW] IRQ line
2063 smsc-ircc2.ircc_dma= [HW] DMA channel
2064 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2065 0: Toshiba Satellite 1800 (GP data pin select)
2066 1: Fast pin select (default)
2067 2: ATC IRMode
2069 snd-ad1816a= [HW,ALSA]
2071 snd-ad1848= [HW,ALSA]
2073 snd-ali5451= [HW,ALSA]
2075 snd-als100= [HW,ALSA]
2077 snd-als4000= [HW,ALSA]
2079 snd-azt2320= [HW,ALSA]
2081 snd-cmi8330= [HW,ALSA]
2083 snd-cmipci= [HW,ALSA]
2085 snd-cs4231= [HW,ALSA]
2087 snd-cs4232= [HW,ALSA]
2089 snd-cs4236= [HW,ALSA]
2091 snd-cs4281= [HW,ALSA]
2093 snd-cs46xx= [HW,ALSA]
2095 snd-dt019x= [HW,ALSA]
2097 snd-dummy= [HW,ALSA]
2099 snd-emu10k1= [HW,ALSA]
2101 snd-ens1370= [HW,ALSA]
2103 snd-ens1371= [HW,ALSA]
2105 snd-es968= [HW,ALSA]
2107 snd-es1688= [HW,ALSA]
2109 snd-es18xx= [HW,ALSA]
2111 snd-es1938= [HW,ALSA]
2113 snd-es1968= [HW,ALSA]
2115 snd-fm801= [HW,ALSA]
2117 snd-gusclassic= [HW,ALSA]
2119 snd-gusextreme= [HW,ALSA]
2121 snd-gusmax= [HW,ALSA]
2123 snd-hdsp= [HW,ALSA]
2125 snd-ice1712= [HW,ALSA]
2127 snd-intel8x0= [HW,ALSA]
2129 snd-interwave= [HW,ALSA]
2131 snd-interwave-stb=
2132 [HW,ALSA]
2134 snd-korg1212= [HW,ALSA]
2136 snd-maestro3= [HW,ALSA]
2138 snd-mpu401= [HW,ALSA]
2140 snd-mtpav= [HW,ALSA]
2142 snd-nm256= [HW,ALSA]
2144 snd-opl3sa2= [HW,ALSA]
2146 snd-opti92x-ad1848=
2147 [HW,ALSA]
2149 snd-opti92x-cs4231=
2150 [HW,ALSA]
2152 snd-opti93x= [HW,ALSA]
2154 snd-pmac= [HW,ALSA]
2156 snd-rme32= [HW,ALSA]
2158 snd-rme96= [HW,ALSA]
2160 snd-rme9652= [HW,ALSA]
2162 snd-sb8= [HW,ALSA]
2164 snd-sb16= [HW,ALSA]
2166 snd-sbawe= [HW,ALSA]
2168 snd-serial= [HW,ALSA]
2170 snd-sgalaxy= [HW,ALSA]
2172 snd-sonicvibes= [HW,ALSA]
2174 snd-sun-amd7930=
2175 [HW,ALSA]
2177 snd-sun-cs4231= [HW,ALSA]
2179 snd-trident= [HW,ALSA]
2181 snd-usb-audio= [HW,ALSA,USB]
2183 snd-via82xx= [HW,ALSA]
2185 snd-virmidi= [HW,ALSA]
2187 snd-wavefront= [HW,ALSA]
2189 snd-ymfpci= [HW,ALSA]
2191 softlockup_panic=
2192 [KNL] Should the soft-lockup detector generate panics.
2194 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2195 See Documentation/sonypi.txt
2197 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2198 See Documentation/serial/specialix.txt.
2200 spia_io_base= [HW,MTD]
2201 spia_fio_base=
2202 spia_pedr=
2203 spia_peddr=
2205 sscape= [HW,OSS]
2206 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2208 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2209 See Documentation/scsi/st.txt.
2211 stacktrace [FTRACE]
2212 Enabled the stack tracer on boot up.
2214 sti= [PARISC,HW]
2215 Format: <num>
2216 Set the STI (builtin display/keyboard on the HP-PARISC
2217 machines) console (graphic card) which should be used
2218 as the initial boot-console.
2219 See also comment in drivers/video/console/sticore.c.
2221 sti_font= [HW]
2222 See comment in drivers/video/console/sticore.c.
2224 stifb= [HW]
2225 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2227 sunrpc.pool_mode=
2228 [NFS]
2229 Control how the NFS server code allocates CPUs to
2230 service thread pools. Depending on how many NICs
2231 you have and where their interrupts are bound, this
2232 option will affect which CPUs will do NFS serving.
2233 Note: this parameter cannot be changed while the
2234 NFS server is running.
2236 auto the server chooses an appropriate mode
2237 automatically using heuristics
2238 global a single global pool contains all CPUs
2239 percpu one pool for each CPU
2240 pernode one pool for each NUMA node (equivalent
2241 to global on non-NUMA machines)
2243 swiotlb= [IA-64] Number of I/O TLB slabs
2245 switches= [HW,M68k]
2247 sym53c416= [HW,SCSI]
2248 See header of drivers/scsi/sym53c416.c.
2250 sysrq_always_enabled
2251 [KNL]
2252 Ignore sysrq setting - this boot parameter will
2253 neutralize any effect of /proc/sys/kernel/sysrq.
2254 Useful for debugging.
2256 t128= [HW,SCSI]
2257 See header of drivers/scsi/t128.c.
2259 tdfx= [HW,DRM]
2261 test_suspend= [SUSPEND]
2262 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2263 standby suspend) as the system sleep state to briefly
2264 enter during system startup. The system is woken from
2265 this state using a wakeup-capable RTC alarm.
2267 thash_entries= [KNL,NET]
2268 Set number of hash buckets for TCP connection
2270 thermal.act= [HW,ACPI]
2271 -1: disable all active trip points in all thermal zones
2272 <degrees C>: override all lowest active trip points
2274 thermal.crt= [HW,ACPI]
2275 -1: disable all critical trip points in all thermal zones
2276 <degrees C>: override all critical trip points
2278 thermal.nocrt= [HW,ACPI]
2279 Set to disable actions on ACPI thermal zone
2280 critical and hot trip points.
2282 thermal.off= [HW,ACPI]
2283 1: disable ACPI thermal control
2285 thermal.psv= [HW,ACPI]
2286 -1: disable all passive trip points
2287 <degrees C>: override all passive trip points to this value
2289 thermal.tzp= [HW,ACPI]
2290 Specify global default ACPI thermal zone polling rate
2291 <deci-seconds>: poll all this frequency
2292 0: no polling (default)
2294 tmscsim= [HW,SCSI]
2295 See comment before function dc390_setup() in
2296 drivers/scsi/tmscsim.c.
2298 topology= [S390]
2299 Format: {off | on}
2300 Specify if the kernel should make use of the cpu
2301 topology informations if the hardware supports these.
2302 The scheduler will make use of these informations and
2303 e.g. base its process migration decisions on it.
2304 Default is off.
2306 tp720= [HW,PS2]
2308 trix= [HW,OSS] MediaTrix AudioTrix Pro
2309 Format:
2310 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2312 tsc= Disable clocksource-must-verify flag for TSC.
2313 Format: <string>
2314 [x86] reliable: mark tsc clocksource as reliable, this
2315 disables clocksource verification at runtime.
2316 Used to enable high-resolution timer mode on older
2317 hardware, and in virtualized environment.
2319 turbografx.map[2|3]= [HW,JOY]
2320 TurboGraFX parallel port interface
2321 Format:
2322 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2323 See also Documentation/input/joystick-parport.txt
2325 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2326 See header of drivers/scsi/u14-34f.c.
2328 uart401= [HW,OSS]
2329 Format: <io>,<irq>
2331 uart6850= [HW,OSS]
2332 Format: <io>,<irq>
2334 uhci-hcd.ignore_oc=
2335 [USB] Ignore overcurrent events (default N).
2336 Some badly-designed motherboards generate lots of
2337 bogus events, for ports that aren't wired to
2338 anything. Set this parameter to avoid log spamming.
2339 Note that genuine overcurrent events won't be
2340 reported either.
2342 unknown_nmi_panic
2343 [X86-32,X86-64]
2344 Set unknown_nmi_panic=1 early on boot.
2346 usbcore.autosuspend=
2347 [USB] The autosuspend time delay (in seconds) used
2348 for newly-detected USB devices (default 2). This
2349 is the time required before an idle device will be
2350 autosuspended. Devices for which the delay is set
2351 to a negative value won't be autosuspended at all.
2353 usbcore.usbfs_snoop=
2354 [USB] Set to log all usbfs traffic (default 0 = off).
2356 usbcore.blinkenlights=
2357 [USB] Set to cycle leds on hubs (default 0 = off).
2359 usbcore.old_scheme_first=
2360 [USB] Start with the old device initialization
2361 scheme (default 0 = off).
2363 usbcore.use_both_schemes=
2364 [USB] Try the other device initialization scheme
2365 if the first one fails (default 1 = enabled).
2367 usbcore.initial_descriptor_timeout=
2368 [USB] Specifies timeout for the initial 64-byte
2369 USB_REQ_GET_DESCRIPTOR request in milliseconds
2370 (default 5000 = 5.0 seconds).
2372 usbhid.mousepoll=
2373 [USBHID] The interval which mice are to be polled at.
2375 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2376 kernel's map of available physical RAM.
2378 vdso= [X86-32,SH,x86-64]
2379 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2380 vdso=1: enable VDSO (default)
2381 vdso=0: disable VDSO mapping
2383 vdso32= [X86-32,X86-64]
2384 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2385 vdso32=1: enable 32-bit VDSO (default)
2386 vdso32=0: disable 32-bit VDSO mapping
2388 vector= [IA-64,SMP]
2389 vector=percpu: enable percpu vector domain
2391 video= [FB] Frame buffer configuration
2392 See Documentation/fb/modedb.txt.
2394 vga= [BOOT,X86-32] Select a particular video mode
2395 See Documentation/x86/i386/boot.txt and
2396 Documentation/svga.txt.
2397 Use vga=ask for menu.
2398 This is actually a boot loader parameter; the value is
2399 passed to the kernel using a special protocol.
2401 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2402 size of <nn>. This can be used to increase the
2403 minimum size (128MB on x86). It can also be used to
2404 decrease the size and leave more room for directly
2405 mapped kernel RAM.
2407 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2408 Format: <command>
2410 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2411 Format: <command>
2413 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2414 Format: <command>
2416 waveartist= [HW,OSS]
2417 Format: <io>,<irq>,<dma>,<dma2>
2419 wd33c93= [HW,SCSI]
2420 See header of drivers/scsi/wd33c93.c.
2422 wd7000= [HW,SCSI]
2423 See header of drivers/scsi/wd7000.c.
2425 wdt= [WDT] Watchdog
2426 See Documentation/watchdog/wdt.txt.
2428 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2429 xd_geo= See header of drivers/block/xd.c.
2431 xirc2ps_cs= [NET,PCMCIA]
2432 Format:
2433 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2435 norandmaps Don't use address space randomization
2436 Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
2438 ______________________________________________________________________
2440 TODO:
2442 Add documentation for ALSA options.
2443 Add more DRM drivers.