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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 This document may not be entirely up to date and comprehensive. The command
21 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
22 module. Loadable modules, after being loaded into the running kernel, also
23 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
24 parameters may be changed at runtime by the command
25 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
27 The parameters listed below are only valid if certain kernel build options were
28 enabled and if respective hardware is present. The text in square brackets at
29 the beginning of each description states the restrictions within which a
30 parameter is applicable:
32 ACPI ACPI support is enabled.
33 AGP AGP (Accelerated Graphics Port) is enabled.
34 ALSA ALSA sound support is enabled.
35 APIC APIC support is enabled.
36 APM Advanced Power Management support is enabled.
37 AVR32 AVR32 architecture is enabled.
38 AX25 Appropriate AX.25 support is enabled.
39 BLACKFIN Blackfin architecture is enabled.
40 DRM Direct Rendering Management support is enabled.
41 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
42 EFI EFI Partitioning (GPT) is enabled
43 EIDE EIDE/ATAPI support is enabled.
44 FB The frame buffer device is enabled.
45 HW Appropriate hardware is enabled.
46 IA-64 IA-64 architecture is enabled.
47 IOSCHED More than one I/O scheduler is enabled.
48 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
49 ISAPNP ISA PnP code is enabled.
50 ISDN Appropriate ISDN support is enabled.
51 JOY Appropriate joystick support is enabled.
52 LIBATA Libata driver is enabled
53 LP Printer support is enabled.
54 LOOP Loopback device support is enabled.
55 M68k M68k architecture is enabled.
56 These options have more detailed description inside of
57 Documentation/m68k/kernel-options.txt.
58 MCA MCA bus support is enabled.
59 MDA MDA console support is enabled.
60 MOUSE Appropriate mouse support is enabled.
61 MSI Message Signaled Interrupts (PCI).
62 MTD MTD (Memory Technology Device) support is enabled.
63 NET Appropriate network support is enabled.
64 NUMA NUMA support is enabled.
65 GENERIC_TIME The generic timeofday code is enabled.
66 NFS Appropriate NFS support is enabled.
67 OSS OSS sound support is enabled.
68 PV_OPS A paravirtualized kernel is enabled.
69 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
70 PARISC The PA-RISC architecture is enabled.
71 PCI PCI bus support is enabled.
72 PCIE PCI Express support is enabled.
73 PCMCIA The PCMCIA subsystem is enabled.
74 PNP Plug & Play support is enabled.
75 PPC PowerPC architecture is enabled.
76 PPT Parallel port support is enabled.
77 PS2 Appropriate PS/2 support is enabled.
78 RAM RAM disk support is enabled.
79 ROOTPLUG The example Root Plug LSM is enabled.
80 S390 S390 architecture is enabled.
81 SCSI Appropriate SCSI support is enabled.
82 A lot of drivers has their options described inside of
83 Documentation/scsi/.
84 SECURITY Different security models are enabled.
85 SELINUX SELinux support is enabled.
86 SERIAL Serial support is enabled.
87 SH SuperH architecture is enabled.
88 SMP The kernel is an SMP kernel.
89 SPARC Sparc architecture is enabled.
90 SWSUSP Software suspend (hibernation) is enabled.
91 SUSPEND System suspend states are enabled.
92 FTRACE Function tracing enabled.
93 TS Appropriate touchscreen support is enabled.
94 UMS USB Mass Storage support is enabled.
95 USB USB support is enabled.
96 USBHID USB Human Interface Device support is enabled.
97 V4L Video For Linux support is enabled.
98 VGA The VGA console has been enabled.
99 VT Virtual terminal support is enabled.
100 WDT Watchdog support is enabled.
101 XT IBM PC/XT MFM hard disk support is enabled.
102 X86-32 X86-32, aka i386 architecture is enabled.
103 X86-64 X86-64 architecture is enabled.
104 More X86-64 boot options can be found in
105 Documentation/x86/x86_64/boot-options.txt .
106 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
108 In addition, the following text indicates that the option:
110 BUGS= Relates to possible processor bugs on the said processor.
111 KNL Is a kernel start-up parameter.
112 BOOT Is a boot loader parameter.
114 Parameters denoted with BOOT are actually interpreted by the boot
115 loader, and have no meaning to the kernel directly.
116 Do not modify the syntax of boot loader parameters without extreme
117 need or coordination with <Documentation/x86/i386/boot.txt>.
119 There are also arch-specific kernel-parameters not documented here.
120 See for example <Documentation/x86/x86_64/boot-options.txt>.
122 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
123 a trailing = on the name of any parameter states that that parameter will
124 be entered as an environment variable, whereas its absence indicates that
125 it will appear as a kernel argument readable via /proc/cmdline by programs
126 running once the system is up.
128 The number of kernel parameters is not limited, but the length of the
129 complete command line (parameters including spaces etc.) is limited to
130 a fixed number of characters. This limit depends on the architecture
131 and is between 256 and 4096 characters. It is defined in the file
132 ./include/asm/setup.h as COMMAND_LINE_SIZE.
135 acpi= [HW,ACPI,X86-64,i386]
136 Advanced Configuration and Power Interface
137 Format: { force | off | ht | strict | noirq }
138 force -- enable ACPI if default was off
139 off -- disable ACPI if default was on
140 noirq -- do not use ACPI for IRQ routing
141 ht -- run only enough ACPI to enable Hyper Threading
142 strict -- Be less tolerant of platforms that are not
143 strictly ACPI specification compliant.
144 rsdt -- prefer RSDT over (default) XSDT
146 See also Documentation/power/pm.txt, pci=noacpi
148 acpi_apic_instance= [ACPI, IOAPIC]
149 Format: <int>
150 2: use 2nd APIC table, if available
151 1,0: use 1st APIC table
152 default: 0
154 acpi_sleep= [HW,ACPI] Sleep options
155 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
156 old_ordering, s4_nonvs }
157 See Documentation/power/video.txt for information on
158 s3_bios and s3_mode.
159 s3_beep is for debugging; it makes the PC's speaker beep
160 as soon as the kernel's real-mode entry point is called.
161 s4_nohwsig prevents ACPI hardware signature from being
162 used during resume from hibernation.
163 old_ordering causes the ACPI 1.0 ordering of the _PTS
164 control method, with respect to putting devices into
165 low power states, to be enforced (the ACPI 2.0 ordering
166 of _PTS is used by default).
167 s4_nonvs prevents the kernel from saving/restoring the
168 ACPI NVS memory during hibernation.
170 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
171 Format: { level | edge | high | low }
173 acpi_irq_balance [HW,ACPI]
174 ACPI will balance active IRQs
175 default in APIC mode
177 acpi_irq_nobalance [HW,ACPI]
178 ACPI will not move active IRQs (default)
179 default in PIC mode
181 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
182 use by PCI
183 Format: <irq>,<irq>...
185 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
186 Format: <irq>,<irq>...
188 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
190 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
191 Format: To spoof as Windows 98: ="Microsoft Windows"
193 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
194 acpi_osi="string1" # add string1 -- only one string
195 acpi_osi="!string2" # remove built-in string2
196 acpi_osi= # disable all strings
198 acpi_serialize [HW,ACPI] force serialization of AML methods
200 acpi_skip_timer_override [HW,ACPI]
201 Recognize and ignore IRQ0/pin2 Interrupt Override.
202 For broken nForce2 BIOS resulting in XT-PIC timer.
203 acpi_use_timer_override [HW,ACPI]
204 Use timer override. For some broken Nvidia NF5 boards
205 that require a timer override, but don't have
206 HPET
208 acpi_backlight= [HW,ACPI]
209 acpi_backlight=vendor
210 acpi_backlight=video
211 If set to vendor, prefer vendor specific driver
212 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
213 of the ACPI video.ko driver.
215 acpi_display_output= [HW,ACPI]
216 acpi_display_output=vendor
217 acpi_display_output=video
218 See above.
220 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
221 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
222 Format: <int>
223 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
224 debug output. Bits in debug_layer correspond to a
225 _COMPONENT in an ACPI source file, e.g.,
226 #define _COMPONENT ACPI_PCI_COMPONENT
227 Bits in debug_level correspond to a level in
228 ACPI_DEBUG_PRINT statements, e.g.,
229 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
230 The debug_level mask defaults to "info". See
231 Documentation/acpi/debug.txt for more information about
232 debug layers and levels.
234 Enable processor driver info messages:
235 acpi.debug_layer=0x20000000
236 Enable PCI/PCI interrupt routing info messages:
237 acpi.debug_layer=0x400000
238 Enable AML "Debug" output, i.e., stores to the Debug
239 object while interpreting AML:
240 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
241 Enable all messages related to ACPI hardware:
242 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
244 Some values produce so much output that the system is
245 unusable. The "log_buf_len" parameter may be useful
246 if you need to capture more output.
248 acpi.power_nocheck= [HW,ACPI]
249 Format: 1/0 enable/disable the check of power state.
250 On some bogus BIOS the _PSC object/_STA object of
251 power resource can't return the correct device power
252 state. In such case it is unneccessary to check its
253 power state again in power transition.
254 1 : disable the power state check
256 acpi_pm_good [X86-32,X86-64]
257 Override the pmtimer bug detection: force the kernel
258 to assume that this machine's pmtimer latches its value
259 and always returns good values.
261 agp= [AGP]
262 { off | try_unsupported }
263 off: disable AGP support
264 try_unsupported: try to drive unsupported chipsets
265 (may crash computer or cause data corruption)
267 enable_timer_pin_1 [i386,x86-64]
268 Enable PIN 1 of APIC timer
269 Can be useful to work around chipset bugs
270 (in particular on some ATI chipsets).
271 The kernel tries to set a reasonable default.
273 disable_timer_pin_1 [i386,x86-64]
274 Disable PIN 1 of APIC timer
275 Can be useful to work around chipset bugs.
277 ad1848= [HW,OSS]
278 Format: <io>,<irq>,<dma>,<dma2>,<type>
280 advansys= [HW,SCSI]
281 See header of drivers/scsi/advansys.c.
283 advwdt= [HW,WDT] Advantech WDT
284 Format: <iostart>,<iostop>
286 aedsp16= [HW,OSS] Audio Excel DSP 16
287 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
288 See also header of sound/oss/aedsp16.c.
290 aha152x= [HW,SCSI]
291 See Documentation/scsi/aha152x.txt.
293 aha1542= [HW,SCSI]
294 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
296 aic7xxx= [HW,SCSI]
297 See Documentation/scsi/aic7xxx.txt.
299 aic79xx= [HW,SCSI]
300 See Documentation/scsi/aic79xx.txt.
302 amd_iommu= [HW,X86-84]
303 Pass parameters to the AMD IOMMU driver in the system.
304 Possible values are:
305 isolate - enable device isolation (each device, as far
306 as possible, will get its own protection
307 domain) [default]
308 share - put every device behind one IOMMU into the
309 same protection domain
310 fullflush - enable flushing of IO/TLB entries when
311 they are unmapped. Otherwise they are
312 flushed before they will be reused, which
313 is a lot of faster
315 amd_iommu_size= [HW,X86-64]
316 Define the size of the aperture for the AMD IOMMU
317 driver. Possible values are:
318 '32M', '64M' (default), '128M', '256M', '512M', '1G'
320 amijoy.map= [HW,JOY] Amiga joystick support
321 Map of devices attached to JOY0DAT and JOY1DAT
322 Format: <a>,<b>
323 See also Documentation/kernel/input/joystick.txt
325 analog.map= [HW,JOY] Analog joystick and gamepad support
326 Specifies type or capabilities of an analog joystick
327 connected to one of 16 gameports
328 Format: <type1>,<type2>,..<type16>
330 apc= [HW,SPARC]
331 Power management functions (SPARCstation-4/5 + deriv.)
332 Format: noidle
333 Disable APC CPU standby support. SPARCstation-Fox does
334 not play well with APC CPU idle - disable it if you have
335 APC and your system crashes randomly.
337 apic= [APIC,i386] Advanced Programmable Interrupt Controller
338 Change the output verbosity whilst booting
339 Format: { quiet (default) | verbose | debug }
340 Change the amount of debugging information output
341 when initialising the APIC and IO-APIC components.
343 apm= [APM] Advanced Power Management
344 See header of arch/x86/kernel/apm_32.c.
346 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
347 Format: <io>,<irq>,<nodeID>
349 ataflop= [HW,M68k]
351 atarimouse= [HW,MOUSE] Atari Mouse
353 atascsi= [HW,SCSI] Atari SCSI
355 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
356 EzKey and similar keyboards
358 atkbd.reset= [HW] Reset keyboard during initialization
360 atkbd.set= [HW] Select keyboard code set
361 Format: <int> (2 = AT (default), 3 = PS/2)
363 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
364 keyboards
366 atkbd.softraw= [HW] Choose between synthetic and real raw mode
367 Format: <bool> (0 = real, 1 = synthetic (default))
369 atkbd.softrepeat= [HW]
370 Use software keyboard repeat
372 autotest [IA64]
374 baycom_epp= [HW,AX25]
375 Format: <io>,<mode>
377 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
378 Format: <io>,<mode>
379 See header of drivers/net/hamradio/baycom_par.c.
381 baycom_ser_fdx= [HW,AX25]
382 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
383 Format: <io>,<irq>,<mode>[,<baud>]
384 See header of drivers/net/hamradio/baycom_ser_fdx.c.
386 baycom_ser_hdx= [HW,AX25]
387 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
388 Format: <io>,<irq>,<mode>
389 See header of drivers/net/hamradio/baycom_ser_hdx.c.
391 boot_delay= Milliseconds to delay each printk during boot.
392 Values larger than 10 seconds (10000) are changed to
393 no delay (0).
394 Format: integer
396 bootmem_debug [KNL] Enable bootmem allocator debug messages.
398 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
399 bttv.radio= Most important insmod options are available as
400 kernel args too.
401 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
402 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
404 BusLogic= [HW,SCSI]
405 See drivers/scsi/BusLogic.c, comment before function
406 BusLogic_ParseDriverOptions().
408 c101= [NET] Moxa C101 synchronous serial card
410 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
411 Sometimes CPU hardware bugs make them report the cache
412 size incorrectly. The kernel will attempt work arounds
413 to fix known problems, but for some CPUs it is not
414 possible to determine what the correct size should be.
415 This option provides an override for these situations.
417 security= [SECURITY] Choose a security module to enable at boot.
418 If this boot parameter is not specified, only the first
419 security module asking for security registration will be
420 loaded. An invalid security module name will be treated
421 as if no module has been chosen.
423 capability.disable=
424 [SECURITY] Disable capabilities. This would normally
425 be used only if an alternative security model is to be
426 configured. Potentially dangerous and should only be
427 used if you are entirely sure of the consequences.
429 ccw_timeout_log [S390]
430 See Documentation/s390/CommonIO for details.
432 cgroup_disable= [KNL] Disable a particular controller
433 Format: {name of the controller(s) to disable}
434 {Currently supported controllers - "memory"}
436 checkreqprot [SELINUX] Set initial checkreqprot flag value.
437 Format: { "0" | "1" }
438 See security/selinux/Kconfig help text.
439 0 -- check protection applied by kernel (includes
440 any implied execute protection).
441 1 -- check protection requested by application.
442 Default value is set via a kernel config option.
443 Value can be changed at runtime via
444 /selinux/checkreqprot.
446 cio_ignore= [S390]
447 See Documentation/s390/CommonIO for details.
449 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
450 [Deprecated]
451 Forces specified clocksource (if available) to be used
452 when calculating gettimeofday(). If specified
453 clocksource is not available, it defaults to PIT.
454 Format: { pit | tsc | cyclone | pmtmr }
456 clocksource= [GENERIC_TIME] Override the default clocksource
457 Format: <string>
458 Override the default clocksource and use the clocksource
459 with the name specified.
460 Some clocksource names to choose from, depending on
461 the platform:
462 [all] jiffies (this is the base, fallback clocksource)
463 [ACPI] acpi_pm
464 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
465 pxa_timer,timer3,32k_counter,timer0_1
466 [AVR32] avr32
467 [X86-32] pit,hpet,tsc,vmi-timer;
468 scx200_hrt on Geode; cyclone on IBM x440
469 [MIPS] MIPS
470 [PARISC] cr16
471 [S390] tod
472 [SH] SuperH
473 [SPARC64] tick
474 [X86-64] hpet,tsc
476 clearcpuid=BITNUM [X86]
477 Disable CPUID feature X for the kernel. See
478 arch/x86/include/asm/cpufeature.h for the valid bit
479 numbers. Note the Linux specific bits are not necessarily
480 stable over kernel options, but the vendor specific
481 ones should be.
482 Also note that user programs calling CPUID directly
483 or using the feature without checking anything
484 will still see it. This just prevents it from
485 being used by the kernel or shown in /proc/cpuinfo.
486 Also note the kernel might malfunction if you disable
487 some critical bits.
489 code_bytes [IA32/X86_64] How many bytes of object code to print
490 in an oops report.
491 Range: 0 - 8192
492 Default: 64
494 hpet= [X86-32,HPET] option to control HPET usage
495 Format: { enable (default) | disable | force }
496 disable: disable HPET and use PIT instead
497 force: allow force enabled of undocumented chips (ICH4,
498 VIA, nVidia)
500 com20020= [HW,NET] ARCnet - COM20020 chipset
501 Format:
502 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
504 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
505 Format: <io>[,<irq>]
507 com90xx= [HW,NET]
508 ARCnet - COM90xx chipset (memory-mapped buffers)
509 Format: <io>[,<irq>[,<memstart>]]
511 condev= [HW,S390] console device
512 conmode=
514 console= [KNL] Output console device and options.
516 tty<n> Use the virtual console device <n>.
518 ttyS<n>[,options]
519 ttyUSB0[,options]
520 Use the specified serial port. The options are of
521 the form "bbbbpnf", where "bbbb" is the baud rate,
522 "p" is parity ("n", "o", or "e"), "n" is number of
523 bits, and "f" is flow control ("r" for RTS or
524 omit it). Default is "9600n8".
526 See Documentation/serial-console.txt for more
527 information. See
528 Documentation/networking/netconsole.txt for an
529 alternative.
531 uart[8250],io,<addr>[,options]
532 uart[8250],mmio,<addr>[,options]
533 Start an early, polled-mode console on the 8250/16550
534 UART at the specified I/O port or MMIO address,
535 switching to the matching ttyS device later. The
536 options are the same as for ttyS, above.
538 If the device connected to the port is not a TTY but a braille
539 device, prepend "brl," before the device type, for instance
540 console=brl,ttyS0
541 For now, only VisioBraille is supported.
543 earlycon= [KNL] Output early console device and options.
544 uart[8250],io,<addr>[,options]
545 uart[8250],mmio,<addr>[,options]
546 Start an early, polled-mode console on the 8250/16550
547 UART at the specified I/O port or MMIO address.
548 The options are the same as for ttyS, above.
550 no_console_suspend
551 [HW] Never suspend the console
552 Disable suspending of consoles during suspend and
553 hibernate operations. Once disabled, debugging
554 messages can reach various consoles while the rest
555 of the system is being put to sleep (ie, while
556 debugging driver suspend/resume hooks). This may
557 not work reliably with all consoles, but is known
558 to work with serial and VGA consoles.
560 coredump_filter=
561 [KNL] Change the default value for
562 /proc/<pid>/coredump_filter.
563 See also Documentation/filesystems/proc.txt.
565 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
566 Format:
567 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
569 crashkernel=nn[KMG]@ss[KMG]
570 [KNL] Reserve a chunk of physical memory to
571 hold a kernel to switch to with kexec on panic.
573 crashkernel=range1:size1[,range2:size2,...][@offset]
574 [KNL] Same as above, but depends on the memory
575 in the running system. The syntax of range is
576 start-[end] where start and end are both
577 a memory unit (amount[KMG]). See also
578 Documentation/kdump/kdump.txt for a example.
580 cs89x0_dma= [HW,NET]
581 Format: <dma>
583 cs89x0_media= [HW,NET]
584 Format: { rj45 | aui | bnc }
586 dasd= [HW,NET]
587 See header of drivers/s390/block/dasd_devmap.c.
589 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
590 (one device per port)
591 Format: <port#>,<type>
592 See also Documentation/input/joystick-parport.txt
594 debug [KNL] Enable kernel debugging (events log level).
596 debug_locks_verbose=
597 [KNL] verbose self-tests
598 Format=<0|1>
599 Print debugging info while doing the locking API
600 self-tests.
601 We default to 0 (no extra messages), setting it to
602 1 will print _a lot_ more information - normally
603 only useful to kernel developers.
605 debug_objects [KNL] Enable object debugging
607 debugpat [X86] Enable PAT debugging
609 decnet.addr= [HW,NET]
610 Format: <area>[,<node>]
611 See also Documentation/networking/decnet.txt.
613 vt.default_blu= [VT]
614 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
615 Change the default blue palette of the console.
616 This is a 16-member array composed of values
617 ranging from 0-255.
619 vt.default_grn= [VT]
620 Format: <green0>,<green1>,<green2>,...,<green15>
621 Change the default green palette of the console.
622 This is a 16-member array composed of values
623 ranging from 0-255.
625 vt.default_red= [VT]
626 Format: <red0>,<red1>,<red2>,...,<red15>
627 Change the default red palette of the console.
628 This is a 16-member array composed of values
629 ranging from 0-255.
631 vt.default_utf8=
632 [VT]
633 Format=<0|1>
634 Set system-wide default UTF-8 mode for all tty's.
635 Default is 1, i.e. UTF-8 mode is enabled for all
636 newly opened terminals.
638 dhash_entries= [KNL]
639 Set number of hash buckets for dentry cache.
641 digi= [HW,SERIAL]
642 IO parameters + enable/disable command.
644 digiepca= [HW,SERIAL]
645 See drivers/char/README.epca and
646 Documentation/serial/digiepca.txt.
648 disable_mtrr_cleanup [X86]
649 enable_mtrr_cleanup [X86]
650 The kernel tries to adjust MTRR layout from continuous
651 to discrete, to make X server driver able to add WB
652 entry later. This parameter enables/disables that.
654 mtrr_chunk_size=nn[KMG] [X86]
655 used for mtrr cleanup. It is largest continous chunk
656 that could hold holes aka. UC entries.
658 mtrr_gran_size=nn[KMG] [X86]
659 Used for mtrr cleanup. It is granularity of mtrr block.
660 Default is 1.
661 Large value could prevent small alignment from
662 using up MTRRs.
664 mtrr_spare_reg_nr=n [X86]
665 Format: <integer>
666 Range: 0,7 : spare reg number
667 Default : 1
668 Used for mtrr cleanup. It is spare mtrr entries number.
669 Set to 2 or more if your graphical card needs more.
671 disable_mtrr_trim [X86, Intel and AMD only]
672 By default the kernel will trim any uncacheable
673 memory out of your available memory pool based on
674 MTRR settings. This parameter disables that behavior,
675 possibly causing your machine to run very slowly.
677 dmasound= [HW,OSS] Sound subsystem buffers
679 dscc4.setup= [NET]
681 dtc3181e= [HW,SCSI]
683 earlyprintk= [X86-32,X86-64,SH,BLACKFIN]
684 earlyprintk=vga
685 earlyprintk=serial[,ttySn[,baudrate]]
686 earlyprintk=dbgp
688 Append ",keep" to not disable it when the real console
689 takes over.
691 Only vga or serial or usb debug port at a time.
693 Currently only ttyS0 and ttyS1 are supported.
695 Interaction with the standard serial driver is not
696 very good.
698 The VGA output is eventually overwritten by the real
699 console.
701 eata= [HW,SCSI]
703 edd= [EDD]
704 Format: {"off" | "on" | "skip[mbr]"}
706 eisa_irq_edge= [PARISC,HW]
707 See header of drivers/parisc/eisa.c.
709 elanfreq= [X86-32]
710 See comment before function elanfreq_setup() in
711 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
713 elevator= [IOSCHED]
714 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
715 See Documentation/block/as-iosched.txt and
716 Documentation/block/deadline-iosched.txt for details.
718 elfcorehdr= [IA64,PPC,SH,X86-32,X86_64]
719 Specifies physical address of start of kernel core
720 image elf header. Generally kexec loader will
721 pass this option to capture kernel.
722 See Documentation/kdump/kdump.txt for details.
724 enforcing [SELINUX] Set initial enforcing status.
725 Format: {"0" | "1"}
726 See security/selinux/Kconfig help text.
727 0 -- permissive (log only, no denials).
728 1 -- enforcing (deny and log).
729 Default value is 0.
730 Value can be changed at runtime via /selinux/enforce.
732 ether= [HW,NET] Ethernet cards parameters
733 This option is obsoleted by the "netdev=" option, which
734 has equivalent usage. See its documentation for details.
736 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
737 Format: <io>[,<irq>]
739 failslab=
740 fail_page_alloc=
741 fail_make_request=[KNL]
742 General fault injection mechanism.
743 Format: <interval>,<probability>,<space>,<times>
744 See also /Documentation/fault-injection/.
746 fd_mcs= [HW,SCSI]
747 See header of drivers/scsi/fd_mcs.c.
749 fdomain= [HW,SCSI]
750 See header of drivers/scsi/fdomain.c.
752 floppy= [HW]
753 See Documentation/blockdev/floppy.txt.
755 force_pal_cache_flush
756 [IA-64] Avoid check_sal_cache_flush which may hang on
757 buggy SAL_CACHE_FLUSH implementations. Using this
758 parameter will force ia64_sal_cache_flush to call
759 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
761 ftrace=[tracer]
762 [ftrace] will set and start the specified tracer
763 as early as possible in order to facilitate early
764 boot debugging.
766 ftrace_dump_on_oops
767 [ftrace] will dump the trace buffers on oops.
769 gamecon.map[2|3]=
770 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
771 support via parallel port (up to 5 devices per port)
772 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
773 See also Documentation/input/joystick-parport.txt
775 gamma= [HW,DRM]
777 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
778 Format: off | on
779 default: on
781 gdth= [HW,SCSI]
782 See header of drivers/scsi/gdth.c.
784 gpt [EFI] Forces disk with valid GPT signature but
785 invalid Protective MBR to be treated as GPT.
787 gvp11= [HW,SCSI]
789 hashdist= [KNL,NUMA] Large hashes allocated during boot
790 are distributed across NUMA nodes. Defaults on
791 for IA-64, off otherwise.
792 Format: 0 | 1 (for off | on)
794 hcl= [IA-64] SGI's Hardware Graph compatibility layer
796 hd= [EIDE] (E)IDE hard drive subsystem geometry
797 Format: <cyl>,<head>,<sect>
799 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
800 size of <nn>. This works even on boxes that have no
801 highmem otherwise. This also works to reduce highmem
802 size on bigger boxes.
804 highres= [KNL] Enable/disable high resolution timer mode.
805 Valid parameters: "on", "off"
806 Default: "on"
808 hisax= [HW,ISDN]
809 See Documentation/isdn/README.HiSax.
811 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
812 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
813 On x86-64 and powerpc, this option can be specified
814 multiple times interleaved with hugepages= to reserve
815 huge pages of different sizes. Valid pages sizes on
816 x86-64 are 2M (when the CPU supports "pse") and 1G
817 (when the CPU supports the "pdpe1gb" cpuinfo flag)
818 Note that 1GB pages can only be allocated at boot time
819 using hugepages= and not freed afterwards.
820 default_hugepagesz=
821 [same as hugepagesz=] The size of the default
822 HugeTLB page size. This is the size represented by
823 the legacy /proc/ hugepages APIs, used for SHM, and
824 default size when mounting hugetlbfs filesystems.
825 Defaults to the default architecture's huge page size
826 if not specified.
828 hlt [BUGS=ARM,SH]
830 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
831 terminal devices. Valid values: 0..8
833 i8042.debug [HW] Toggle i8042 debug mode
834 i8042.direct [HW] Put keyboard port into non-translated mode
835 i8042.dumbkbd [HW] Pretend that controller can only read data from
836 keyboard and cannot control its state
837 (Don't attempt to blink the leds)
838 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
839 i8042.nokbd [HW] Don't check/create keyboard port
840 i8042.noloop [HW] Disable the AUX Loopback command while probing
841 for the AUX port
842 i8042.nomux [HW] Don't check presence of an active multiplexing
843 controller
844 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
845 controllers
846 i8042.panicblink=
847 [HW] Frequency with which keyboard LEDs should blink
848 when kernel panics (default is 0.5 sec)
849 i8042.reset [HW] Reset the controller during init and cleanup
850 i8042.unlock [HW] Unlock (ignore) the keylock
852 i810= [HW,DRM]
854 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
855 indicates that the driver is running on unsupported
856 hardware.
857 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
858 does not match list of supported models.
859 i8k.power_status
860 [HW] Report power status in /proc/i8k
861 (disabled by default)
862 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
863 capability is set.
865 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
866 See Documentation/mca.txt.
868 icn= [HW,ISDN]
869 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
871 ide= [HW] (E)IDE subsystem
872 Format: ide=nodma or ide=doubler
873 See Documentation/ide/ide.txt.
875 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
876 See Documentation/ide/ide.txt.
878 idle= [X86]
879 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
880 Poll forces a polling idle loop that can slightly
881 improve the performance of waking up a idle CPU, but
882 will use a lot of power and make the system run hot.
883 Not recommended.
884 idle=mwait: On systems which support MONITOR/MWAIT but
885 the kernel chose to not use it because it doesn't save
886 as much power as a normal idle loop, use the
887 MONITOR/MWAIT idle loop anyways. Performance should be
888 the same as idle=poll.
889 idle=halt: Halt is forced to be used for CPU idle.
890 In such case C2/C3 won't be used again.
891 idle=nomwait: Disable mwait for CPU C-states
893 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
894 Claim all unknown PCI IDE storage controllers.
896 ignore_loglevel [KNL]
897 Ignore loglevel setting - this will print /all/
898 kernel messages to the console. Useful for debugging.
900 ihash_entries= [KNL]
901 Set number of hash buckets for inode cache.
903 in2000= [HW,SCSI]
904 See header of drivers/scsi/in2000.c.
906 init= [KNL]
907 Format: <full_path>
908 Run specified binary instead of /sbin/init as init
909 process.
911 initcall_debug [KNL] Trace initcalls as they are executed. Useful
912 for working out where the kernel is dying during
913 startup.
915 initrd= [BOOT] Specify the location of the initial ramdisk
917 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
918 Format: <irq>
920 inttest= [IA64]
922 iomem= Disable strict checking of access to MMIO memory
923 strict regions from userspace.
924 relaxed
926 iommu= [x86]
927 off
928 force
929 noforce
930 biomerge
931 panic
932 nopanic
933 merge
934 nomerge
935 forcesac
936 soft
939 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
940 on
941 Enable intel iommu driver.
942 off
943 Disable intel iommu driver.
944 igfx_off [Default Off]
945 By default, gfx is mapped as normal device. If a gfx
946 device has a dedicated DMAR unit, the DMAR unit is
947 bypassed by not enabling DMAR with this option. In
948 this case, gfx device will use physical address for
949 DMA.
950 forcedac [x86_64]
951 With this option iommu will not optimize to look
952 for io virtual address below 32 bit forcing dual
953 address cycle on pci bus for cards supporting greater
954 than 32 bit addressing. The default is to look
955 for translation below 32 bit and if not available
956 then look in the higher range.
957 strict [Default Off]
958 With this option on every unmap_single operation will
959 result in a hardware IOTLB flush operation as opposed
960 to batching them for performance.
962 io_delay= [X86-32,X86-64] I/O delay method
963 0x80
964 Standard port 0x80 based delay
965 0xed
966 Alternate port 0xed based delay (needed on some systems)
967 udelay
968 Simple two microseconds delay
969 none
970 No delay
972 io7= [HW] IO7 for Marvel based alpha systems
973 See comment before marvel_specify_io7 in
974 arch/alpha/kernel/core_marvel.c.
976 ip= [IP_PNP]
977 See Documentation/filesystems/nfsroot.txt.
979 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
980 See comment before ip2_setup() in
981 drivers/char/ip2/ip2base.c.
983 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
984 See header of drivers/scsi/ips.c.
986 ports= [IP_VS_FTP] IPVS ftp helper module
987 Default is 21.
988 Up to 8 (IP_VS_APP_MAX_PORTS) ports
989 may be specified.
990 Format: <port>,<port>....
992 irqfixup [HW]
993 When an interrupt is not handled search all handlers
994 for it. Intended to get systems with badly broken
995 firmware running.
997 irqpoll [HW]
998 When an interrupt is not handled search all handlers
999 for it. Also check all handlers each timer
1000 interrupt. Intended to get systems with badly broken
1001 firmware running.
1003 isapnp= [ISAPNP]
1004 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1006 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1007 Format:
1008 <cpu number>,...,<cpu number>
1009 or
1010 <cpu number>-<cpu number>
1011 (must be a positive range in ascending order)
1012 or a mixture
1013 <cpu number>,...,<cpu number>-<cpu number>
1015 This option can be used to specify one or more CPUs
1016 to isolate from the general SMP balancing and scheduling
1017 algorithms. You can move a process onto or off an
1018 "isolated" CPU via the CPU affinity syscalls or cpuset.
1019 <cpu number> begins at 0 and the maximum value is
1020 "number of CPUs in system - 1".
1022 This option is the preferred way to isolate CPUs. The
1023 alternative -- manually setting the CPU mask of all
1024 tasks in the system -- can cause problems and
1025 suboptimal load balancer performance.
1027 iucv= [HW,NET]
1029 js= [HW,JOY] Analog joystick
1030 See Documentation/input/joystick.txt.
1032 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1033 specifies the amount of memory usable by the kernel
1034 for non-movable allocations. The requested amount is
1035 spread evenly throughout all nodes in the system. The
1036 remaining memory in each node is used for Movable
1037 pages. In the event, a node is too small to have both
1038 kernelcore and Movable pages, kernelcore pages will
1039 take priority and other nodes will have a larger number
1040 of kernelcore pages. The Movable zone is used for the
1041 allocation of pages that may be reclaimed or moved
1042 by the page migration subsystem. This means that
1043 HugeTLB pages may not be allocated from this zone.
1044 Note that allocations like PTEs-from-HighMem still
1045 use the HighMem zone if it exists, and the Normal
1046 zone if it does not.
1048 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1049 is similar to kernelcore except it specifies the
1050 amount of memory used for migratable allocations.
1051 If both kernelcore and movablecore is specified,
1052 then kernelcore will be at *least* the specified
1053 value but may be more. If movablecore on its own
1054 is specified, the administrator must be careful
1055 that the amount of memory usable for all allocations
1056 is not too small.
1058 keepinitrd [HW,ARM]
1060 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1061 in oops dumps.
1063 kgdboc= [HW] kgdb over consoles.
1064 Requires a tty driver that supports console polling.
1065 (only serial suported for now)
1066 Format: <serial_device>[,baud]
1068 kmac= [MIPS] korina ethernet MAC address.
1069 Configure the RouterBoard 532 series on-chip
1070 Ethernet adapter MAC address.
1072 l2cr= [PPC]
1074 l3cr= [PPC]
1076 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1077 disabled it.
1079 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer
1080 in C2 power state.
1082 libata.dma= [LIBATA] DMA control
1083 libata.dma=0 Disable all PATA and SATA DMA
1084 libata.dma=1 PATA and SATA Disk DMA only
1085 libata.dma=2 ATAPI (CDROM) DMA only
1086 libata.dma=4 Compact Flash DMA only
1087 Combinations also work, so libata.dma=3 enables DMA
1088 for disks and CDROMs, but not CFs.
1090 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1091 when set.
1092 Format: <int>
1094 libata.force= [LIBATA] Force configurations. The format is comma
1095 separated list of "[ID:]VAL" where ID is
1096 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1097 matching port, link or device. Basically, it matches
1098 the ATA ID string printed on console by libata. If
1099 the whole ID part is omitted, the last PORT and DEVICE
1100 values are used. If ID hasn't been specified yet, the
1101 configuration applies to all ports, links and devices.
1103 If only DEVICE is omitted, the parameter applies to
1104 the port and all links and devices behind it. DEVICE
1105 number of 0 either selects the first device or the
1106 first fan-out link behind PMP device. It does not
1107 select the host link. DEVICE number of 15 selects the
1108 host link and device attached to it.
1110 The VAL specifies the configuration to force. As long
1111 as there's no ambiguity shortcut notation is allowed.
1112 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1113 The following configurations can be forced.
1115 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1116 Any ID with matching PORT is used.
1118 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1120 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1121 udma[/][16,25,33,44,66,100,133] notation is also
1122 allowed.
1124 * [no]ncq: Turn on or off NCQ.
1126 * nohrst, nosrst, norst: suppress hard, soft
1127 and both resets.
1129 If there are multiple matching configurations changing
1130 the same attribute, the last one is used.
1132 lmb=debug [KNL] Enable lmb debug messages.
1134 load_ramdisk= [RAM] List of ramdisks to load from floppy
1135 See Documentation/blockdev/ramdisk.txt.
1137 lockd.nlm_grace_period=P [NFS] Assign grace period.
1138 Format: <integer>
1140 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1141 Format: <integer>
1143 lockd.nlm_timeout=T [NFS] Assign timeout value.
1144 Format: <integer>
1146 lockd.nlm_udpport=M [NFS] Assign UDP port.
1147 Format: <integer>
1149 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1150 Format: <irq>
1152 loglevel= All Kernel Messages with a loglevel smaller than the
1153 console loglevel will be printed to the console. It can
1154 also be changed with klogd or other programs. The
1155 loglevels are defined as follows:
1157 0 (KERN_EMERG) system is unusable
1158 1 (KERN_ALERT) action must be taken immediately
1159 2 (KERN_CRIT) critical conditions
1160 3 (KERN_ERR) error conditions
1161 4 (KERN_WARNING) warning conditions
1162 5 (KERN_NOTICE) normal but significant condition
1163 6 (KERN_INFO) informational
1164 7 (KERN_DEBUG) debug-level messages
1166 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1167 Format: { n | nk | nM }
1168 n must be a power of two. The default size
1169 is set in the kernel config file.
1171 logo.nologo [FB] Disables display of the built-in Linux logo.
1172 This may be used to provide more screen space for
1173 kernel log messages and is useful when debugging
1174 kernel boot problems.
1176 lp=0 [LP] Specify parallel ports to use, e.g,
1177 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1178 lp=reset first parallel port). 'lp=0' disables the
1179 lp=auto printer driver. 'lp=reset' (which can be
1180 specified in addition to the ports) causes
1181 attached printers to be reset. Using
1182 lp=port1,port2,... specifies the parallel ports
1183 to associate lp devices with, starting with
1184 lp0. A port specification may be 'none' to skip
1185 that lp device, or a parport name such as
1186 'parport0'. Specifying 'lp=auto' instead of a
1187 port specification list means that device IDs
1188 from each port should be examined, to see if
1189 an IEEE 1284-compliant printer is attached; if
1190 so, the driver will manage that printer.
1191 See also header of drivers/char/lp.c.
1193 lpj=n [KNL]
1194 Sets loops_per_jiffy to given constant, thus avoiding
1195 time-consuming boot-time autodetection (up to 250 ms per
1196 CPU). 0 enables autodetection (default). To determine
1197 the correct value for your kernel, boot with normal
1198 autodetection and see what value is printed. Note that
1199 on SMP systems the preset will be applied to all CPUs,
1200 which is likely to cause problems if your CPUs need
1201 significantly divergent settings. An incorrect value
1202 will cause delays in the kernel to be wrong, leading to
1203 unpredictable I/O errors and other breakage. Although
1204 unlikely, in the extreme case this might damage your
1205 hardware.
1207 ltpc= [NET]
1208 Format: <io>,<irq>,<dma>
1210 mac5380= [HW,SCSI] Format:
1211 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1213 machvec= [IA64] Force the use of a particular machine-vector
1214 (machvec) in a generic kernel.
1215 Example: machvec=hpzx1_swiotlb
1217 max_loop= [LOOP] Maximum number of loopback devices that can
1218 be mounted
1219 Format: <1-256>
1221 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1222 should make use of. maxcpus=n : n >= 0 limits the
1223 kernel to using 'n' processors. n=0 is a special case,
1224 it is equivalent to "nosmp", which also disables
1225 the IO APIC.
1227 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than
1228 or equal to this physical address is ignored.
1230 max_luns= [SCSI] Maximum number of LUNs to probe.
1231 Should be between 1 and 2^32-1.
1233 max_report_luns=
1234 [SCSI] Maximum number of LUNs received.
1235 Should be between 1 and 16384.
1237 mcatest= [IA-64]
1239 mce [X86-32] Machine Check Exception
1241 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1243 md= [HW] RAID subsystems devices and level
1244 See Documentation/md.txt.
1246 mdacon= [MDA]
1247 Format: <first>,<last>
1248 Specifies range of consoles to be captured by the MDA.
1250 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1251 Amount of memory to be used when the kernel is not able
1252 to see the whole system memory or for test.
1253 [X86-32] Use together with memmap= to avoid physical
1254 address space collisions. Without memmap= PCI devices
1255 could be placed at addresses belonging to unused RAM.
1257 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1258 memory.
1260 memchunk=nn[KMG]
1261 [KNL,SH] Allow user to override the default size for
1262 per-device physically contiguous DMA buffers.
1264 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1265 E820 memory map, as specified by the user.
1266 Such memmap=exactmap lines can be constructed based on
1267 BIOS output or other requirements. See the memmap=nn@ss
1268 option description.
1270 memmap=nn[KMG]@ss[KMG]
1271 [KNL] Force usage of a specific region of memory
1272 Region of memory to be used, from ss to ss+nn.
1274 memmap=nn[KMG]#ss[KMG]
1275 [KNL,ACPI] Mark specific memory as ACPI data.
1276 Region of memory to be used, from ss to ss+nn.
1278 memmap=nn[KMG]$ss[KMG]
1279 [KNL,ACPI] Mark specific memory as reserved.
1280 Region of memory to be used, from ss to ss+nn.
1281 Example: Exclude memory from 0x18690000-0x1869ffff
1282 memmap=64K$0x18690000
1283 or
1284 memmap=0x10000$0x18690000
1286 memory_corruption_check=0/1 [X86]
1287 Some BIOSes seem to corrupt the first 64k of
1288 memory when doing things like suspend/resume.
1289 Setting this option will scan the memory
1290 looking for corruption. Enabling this will
1291 both detect corruption and prevent the kernel
1292 from using the memory being corrupted.
1293 However, its intended as a diagnostic tool; if
1294 repeatable BIOS-originated corruption always
1295 affects the same memory, you can use memmap=
1296 to prevent the kernel from using that memory.
1298 memory_corruption_check_size=size [X86]
1299 By default it checks for corruption in the low
1300 64k, making this memory unavailable for normal
1301 use. Use this parameter to scan for
1302 corruption in more or less memory.
1304 memory_corruption_check_period=seconds [X86]
1305 By default it checks for corruption every 60
1306 seconds. Use this parameter to check at some
1307 other rate. 0 disables periodic checking.
1309 memtest= [KNL,X86] Enable memtest
1310 Format: <integer>
1311 range: 0,4 : pattern number
1312 default : 0 <disable>
1314 meye.*= [HW] Set MotionEye Camera parameters
1315 See Documentation/video4linux/meye.txt.
1317 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1318 Multi-Function General Purpose Timers on AMD Geode
1319 platforms.
1321 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1322 the BIOS has incorrectly applied a workaround. TinyBIOS
1323 version 0.98 is known to be affected, 0.99 fixes the
1324 problem by letting the user disable the workaround.
1326 mga= [HW,DRM]
1328 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1329 physical address is ignored.
1331 mminit_loglevel=
1332 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1333 parameter allows control of the logging verbosity for
1334 the additional memory initialisation checks. A value
1335 of 0 disables mminit logging and a level of 4 will
1336 log everything. Information is printed at KERN_DEBUG
1337 so loglevel=8 may also need to be specified.
1339 mousedev.tap_time=
1340 [MOUSE] Maximum time between finger touching and
1341 leaving touchpad surface for touch to be considered
1342 a tap and be reported as a left button click (for
1343 touchpads working in absolute mode only).
1344 Format: <msecs>
1345 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1346 reporting absolute coordinates, such as tablets
1347 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1348 reporting absolute coordinates, such as tablets
1350 mpu401= [HW,OSS]
1351 Format: <io>,<irq>
1353 MTD_Partition= [MTD]
1354 Format: <name>,<region-number>,<size>,<offset>
1356 MTD_Region= [MTD] Format:
1357 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1359 mtdparts= [MTD]
1360 See drivers/mtd/cmdlinepart.c.
1362 mtdset= [ARM]
1363 ARM/S3C2412 JIVE boot control
1365 See arch/arm/mach-s3c2412/mach-jive.c
1367 mtouchusb.raw_coordinates=
1368 [HW] Make the MicroTouch USB driver use raw coordinates
1369 ('y', default) or cooked coordinates ('n')
1371 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1373 NCR_D700= [HW,SCSI]
1374 See header of drivers/scsi/NCR_D700.c.
1376 ncr5380= [HW,SCSI]
1378 ncr53c400= [HW,SCSI]
1380 ncr53c400a= [HW,SCSI]
1382 ncr53c406a= [HW,SCSI]
1384 ncr53c8xx= [HW,SCSI]
1386 netdev= [NET] Network devices parameters
1387 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1388 Note that mem_start is often overloaded to mean
1389 something different and driver-specific.
1390 This usage is only documented in each driver source
1391 file if at all.
1393 nf_conntrack.acct=
1394 [NETFILTER] Enable connection tracking flow accounting
1395 0 to disable accounting
1396 1 to enable accounting
1397 Default value depends on CONFIG_NF_CT_ACCT that is
1398 going to be removed in 2.6.29.
1400 nfsaddrs= [NFS]
1401 See Documentation/filesystems/nfsroot.txt.
1403 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1404 See Documentation/filesystems/nfsroot.txt.
1406 nfs.callback_tcpport=
1407 [NFS] set the TCP port on which the NFSv4 callback
1408 channel should listen.
1410 nfs.idmap_cache_timeout=
1411 [NFS] set the maximum lifetime for idmapper cache
1412 entries.
1414 nfs.enable_ino64=
1415 [NFS] enable 64-bit inode numbers.
1416 If zero, the NFS client will fake up a 32-bit inode
1417 number for the readdir() and stat() syscalls instead
1418 of returning the full 64-bit number.
1419 The default is to return 64-bit inode numbers.
1421 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1422 when a NMI is triggered.
1423 Format: [state][,regs][,debounce][,die]
1425 nmi_watchdog= [KNL,BUGS=X86-32,X86-64] Debugging features for SMP kernels
1426 Format: [panic,][num]
1427 Valid num: 0,1,2
1428 0 - turn nmi_watchdog off
1429 1 - use the IO-APIC timer for the NMI watchdog
1430 2 - use the local APIC for the NMI watchdog using
1431 a performance counter. Note: This will use one performance
1432 counter and the local APIC's performance vector.
1433 When panic is specified panic when an NMI watchdog timeout occurs.
1434 This is useful when you use a panic=... timeout and need the box
1435 quickly up again.
1436 Instead of 1 and 2 it is possible to use the following
1437 symbolic names: lapic and ioapic
1438 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1440 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1441 emulation library even if a 387 maths coprocessor
1442 is present.
1444 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1445 caches in the slab allocator. Saves per-node memory,
1446 but will impact performance.
1448 noalign [KNL,ARM]
1450 noapic [SMP,APIC] Tells the kernel to not make use of any
1451 IOAPICs that may be present in the system.
1453 nobats [PPC] Do not use BATs for mapping kernel lowmem
1454 on "Classic" PPC cores.
1456 nocache [ARM]
1458 nodelayacct [KNL] Disable per-task delay accounting
1460 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1462 nodsp [SH] Disable hardware DSP at boot time.
1464 noefi [X86-32,X86-64] Disable EFI runtime services support.
1466 noexec [IA-64]
1468 noexec [X86-32,X86-64]
1469 On X86-32 available only on PAE configured kernels.
1470 noexec=on: enable non-executable mappings (default)
1471 noexec=off: disable non-executable mappings
1473 noexec32 [X86-64]
1474 This affects only 32-bit executables.
1475 noexec32=on: enable non-executable mappings (default)
1476 read doesn't imply executable mappings
1477 noexec32=off: disable non-executable mappings
1478 read implies executable mappings
1480 nofpu [SH] Disable hardware FPU at boot time.
1482 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1483 register save and restore. The kernel will only save
1484 legacy floating-point registers on task switch.
1486 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1488 nohlt [BUGS=ARM,SH]
1490 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1491 instruction doesn't work correctly and not to
1492 use it.
1494 no_file_caps Tells the kernel not to honor file capabilities. The
1495 only way then for a file to be executed with privilege
1496 is to be setuid root or executed by root.
1498 nohalt [IA-64] Tells the kernel not to use the power saving
1499 function PAL_HALT_LIGHT when idle. This increases
1500 power-consumption. On the positive side, it reduces
1501 interrupt wake-up latency, which may improve performance
1502 in certain environments such as networked servers or
1503 real-time systems.
1505 nohz= [KNL] Boottime enable/disable dynamic ticks
1506 Valid arguments: on, off
1507 Default: on
1509 noirqdebug [X86-32] Disables the code which attempts to detect and
1510 disable unhandled interrupt sources.
1512 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1513 broken timer IRQ sources.
1515 noisapnp [ISAPNP] Disables ISA PnP code.
1517 noinitrd [RAM] Tells the kernel not to load any configured
1518 initial RAM disk.
1520 nointroute [IA-64]
1522 nojitter [IA64] Disables jitter checking for ITC timers.
1524 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1526 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1528 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1530 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
1531 default x2apic cluster mode on platforms
1532 supporting x2apic.
1534 noltlbs [PPC] Do not use large page/tlb entries for kernel
1535 lowmem mapping on PPC40x.
1537 nomca [IA-64] Disable machine check abort handling
1539 nomce [X86-32] Machine Check Exception
1541 nomfgpt [X86-32] Disable Multi-Function General Purpose
1542 Timer usage (for AMD Geode machines).
1544 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1546 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1547 with UP alternatives
1549 noresidual [PPC] Don't use residual data on PReP machines.
1551 noresume [SWSUSP] Disables resume and restores original swap
1552 space.
1554 no-scroll [VGA] Disables scrollback.
1555 This is required for the Braillex ib80-piezo Braille
1556 reader made by F.H. Papenmeier (Germany).
1558 nosbagart [IA-64]
1560 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1562 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1563 and disable the IO APIC. legacy for "maxcpus=0".
1565 nosoftlockup [KNL] Disable the soft-lockup detector.
1567 noswapaccount [KNL] Disable accounting of swap in memory resource
1568 controller. (See Documentation/controllers/memory.txt)
1570 nosync [HW,M68K] Disables sync negotiation for all devices.
1572 notsc [BUGS=X86-32] Disable Time Stamp Counter
1574 nousb [USB] Disable the USB subsystem
1576 nowb [ARM]
1578 nptcg= [IA64] Override max number of concurrent global TLB
1579 purges which is reported from either PAL_VM_SUMMARY or
1580 SAL PALO.
1582 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1583 one of ['zone', 'node', 'default'] can be specified
1584 This can be set from sysctl after boot.
1585 See Documentation/sysctl/vm.txt for details.
1587 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1589 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1590 See Documentation/debugging-via-ohci1394.txt for more
1591 info.
1593 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1594 Rather than timing out after 20 ms if an EC
1595 command is not properly ACKed, override the length
1596 of the timeout. We have interrupts disabled while
1597 waiting for the ACK, so if this is set too high
1598 interrupts *may* be lost!
1600 opl3= [HW,OSS]
1601 Format: <io>
1603 oprofile.timer= [HW]
1604 Use timer interrupt instead of performance counters
1606 osst= [HW,SCSI] SCSI Tape Driver
1607 Format: <buffer_size>,<write_threshold>
1608 See also Documentation/scsi/st.txt.
1610 panic= [KNL] Kernel behaviour on panic
1611 Format: <timeout>
1613 parkbd.port= [HW] Parallel port number the keyboard adapter is
1614 connected to, default is 0.
1615 Format: <parport#>
1616 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1617 0 for XT, 1 for AT (default is AT).
1618 Format: <mode>
1620 parport= [HW,PPT] Specify parallel ports. 0 disables.
1621 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1622 Use 'auto' to force the driver to use any
1623 IRQ/DMA settings detected (the default is to
1624 ignore detected IRQ/DMA settings because of
1625 possible conflicts). You can specify the base
1626 address, IRQ, and DMA settings; IRQ and DMA
1627 should be numbers, or 'auto' (for using detected
1628 settings on that particular port), or 'nofifo'
1629 (to avoid using a FIFO even if it is detected).
1630 Parallel ports are assigned in the order they
1631 are specified on the command line, starting
1632 with parport0.
1634 parport_init_mode= [HW,PPT]
1635 Configure VIA parallel port to operate in
1636 a specific mode. This is necessary on Pegasos
1637 computer where firmware has no options for setting
1638 up parallel port mode and sets it to spp.
1639 Currently this function knows 686a and 8231 chips.
1640 Format: [spp|ps2|epp|ecp|ecpepp]
1642 pas2= [HW,OSS] Format:
1643 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1645 pas16= [HW,SCSI]
1646 See header of drivers/scsi/pas16.c.
1648 pause_on_oops=
1649 Halt all CPUs after the first oops has been printed for
1650 the specified number of seconds. This is to be used if
1651 your oopses keep scrolling off the screen.
1653 pcbit= [HW,ISDN]
1655 pcd. [PARIDE]
1656 See header of drivers/block/paride/pcd.c.
1657 See also Documentation/blockdev/paride.txt.
1659 pci=option[,option...] [PCI] various PCI subsystem options:
1660 off [X86] don't probe for the PCI bus
1661 bios [X86-32] force use of PCI BIOS, don't access
1662 the hardware directly. Use this if your machine
1663 has a non-standard PCI host bridge.
1664 nobios [X86-32] disallow use of PCI BIOS, only direct
1665 hardware access methods are allowed. Use this
1666 if you experience crashes upon bootup and you
1667 suspect they are caused by the BIOS.
1668 conf1 [X86] Force use of PCI Configuration
1669 Mechanism 1.
1670 conf2 [X86] Force use of PCI Configuration
1671 Mechanism 2.
1672 noaer [PCIE] If the PCIEAER kernel config parameter is
1673 enabled, this kernel boot option can be used to
1674 disable the use of PCIE advanced error reporting.
1675 nodomains [PCI] Disable support for multiple PCI
1676 root domains (aka PCI segments, in ACPI-speak).
1677 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1678 Configuration
1679 nomsi [MSI] If the PCI_MSI kernel config parameter is
1680 enabled, this kernel boot option can be used to
1681 disable the use of MSI interrupts system-wide.
1682 noioapicquirk [APIC] Disable all boot interrupt quirks.
1683 Safety option to keep boot IRQs enabled. This
1684 should never be necessary.
1685 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1686 primary IO-APIC for bridges that cannot disable
1687 boot IRQs. This fixes a source of spurious IRQs
1688 when the system masks IRQs.
1689 noioapicreroute [APIC] Disable workaround that uses the
1690 boot IRQ equivalent of an IRQ that connects to
1691 a chipset where boot IRQs cannot be disabled.
1692 The opposite of ioapicreroute.
1693 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1694 routing table. These calls are known to be buggy
1695 on several machines and they hang the machine
1696 when used, but on other computers it's the only
1697 way to get the interrupt routing table. Try
1698 this option if the kernel is unable to allocate
1699 IRQs or discover secondary PCI buses on your
1700 motherboard.
1701 rom [X86] Assign address space to expansion ROMs.
1702 Use with caution as certain devices share
1703 address decoders between ROMs and other
1704 resources.
1705 norom [X86] Do not assign address space to
1706 expansion ROMs that do not already have
1707 BIOS assigned address ranges.
1708 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1709 assigned automatically to PCI devices. You can
1710 make the kernel exclude IRQs of your ISA cards
1711 this way.
1712 pirqaddr=0xAAAAA [X86] Specify the physical address
1713 of the PIRQ table (normally generated
1714 by the BIOS) if it is outside the
1715 F0000h-100000h range.
1716 lastbus=N [X86] Scan all buses thru bus #N. Can be
1717 useful if the kernel is unable to find your
1718 secondary buses and you want to tell it
1719 explicitly which ones they are.
1720 assign-busses [X86] Always assign all PCI bus
1721 numbers ourselves, overriding
1722 whatever the firmware may have done.
1723 usepirqmask [X86] Honor the possible IRQ mask stored
1724 in the BIOS $PIR table. This is needed on
1725 some systems with broken BIOSes, notably
1726 some HP Pavilion N5400 and Omnibook XE3
1727 notebooks. This will have no effect if ACPI
1728 IRQ routing is enabled.
1729 noacpi [X86] Do not use ACPI for IRQ routing
1730 or for PCI scanning.
1731 use_crs [X86] Use _CRS for PCI resource
1732 allocation.
1733 routeirq Do IRQ routing for all PCI devices.
1734 This is normally done in pci_enable_device(),
1735 so this option is a temporary workaround
1736 for broken drivers that don't call it.
1737 skip_isa_align [X86] do not align io start addr, so can
1738 handle more pci cards
1739 firmware [ARM] Do not re-enumerate the bus but instead
1740 just use the configuration from the
1741 bootloader. This is currently used on
1742 IXP2000 systems where the bus has to be
1743 configured a certain way for adjunct CPUs.
1744 noearly [X86] Don't do any early type 1 scanning.
1745 This might help on some broken boards which
1746 machine check when some devices' config space
1747 is read. But various workarounds are disabled
1748 and some IOMMU drivers will not work.
1749 bfsort Sort PCI devices into breadth-first order.
1750 This sorting is done to get a device
1751 order compatible with older (<= 2.4) kernels.
1752 nobfsort Don't sort PCI devices into breadth-first order.
1753 cbiosize=nn[KMG] The fixed amount of bus space which is
1754 reserved for the CardBus bridge's IO window.
1755 The default value is 256 bytes.
1756 cbmemsize=nn[KMG] The fixed amount of bus space which is
1757 reserved for the CardBus bridge's memory
1758 window. The default value is 64 megabytes.
1760 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1761 Management.
1762 off Disable ASPM.
1763 force Enable ASPM even on devices that claim not to support it.
1764 WARNING: Forcing ASPM on may cause system lockups.
1766 pcmv= [HW,PCMCIA] BadgePAD 4
1768 pd. [PARIDE]
1769 See Documentation/blockdev/paride.txt.
1771 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1772 boot time.
1773 Format: { 0 | 1 }
1774 See arch/parisc/kernel/pdc_chassis.c
1776 pf. [PARIDE]
1777 See Documentation/blockdev/paride.txt.
1779 pg. [PARIDE]
1780 See Documentation/blockdev/paride.txt.
1782 pirq= [SMP,APIC] Manual mp-table setup
1783 See Documentation/x86/i386/IO-APIC.txt.
1785 plip= [PPT,NET] Parallel port network link
1786 Format: { parport<nr> | timid | 0 }
1787 See also Documentation/parport.txt.
1789 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1790 Override pmtimer IOPort with a hex value.
1791 e.g. pmtmr=0x508
1793 pnp.debug [PNP]
1794 Enable PNP debug messages. This depends on the
1795 CONFIG_PNP_DEBUG_MESSAGES option.
1797 pnpacpi= [ACPI]
1798 { off }
1800 pnpbios= [ISAPNP]
1801 { on | off | curr | res | no-curr | no-res }
1803 pnp_reserve_irq=
1804 [ISAPNP] Exclude IRQs for the autoconfiguration
1806 pnp_reserve_dma=
1807 [ISAPNP] Exclude DMAs for the autoconfiguration
1809 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1810 Ranges are in pairs (I/O port base and size).
1812 pnp_reserve_mem=
1813 [ISAPNP] Exclude memory regions for the
1814 autoconfiguration.
1815 Ranges are in pairs (memory base and size).
1817 dynamic_printk Enables pr_debug()/dev_dbg() calls if
1818 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
1819 These can also be switched on/off via
1820 <debugfs>/dynamic_printk/modules
1822 print-fatal-signals=
1823 [KNL] debug: print fatal signals
1824 print-fatal-signals=1: print segfault info to
1825 the kernel console.
1826 default: off.
1828 printk.time= Show timing data prefixed to each printk message line
1829 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1831 profile= [KNL] Enable kernel profiling via /proc/profile
1832 Format: [schedule,]<number>
1833 Param: "schedule" - profile schedule points.
1834 Param: <number> - step/bucket size as a power of 2 for
1835 statistical time based profiling.
1836 Param: "sleep" - profile D-state sleeping (millisecs).
1837 Requires CONFIG_SCHEDSTATS
1838 Param: "kvm" - profile VM exits.
1840 processor.max_cstate= [HW,ACPI]
1841 Limit processor to maximum C-state
1842 max_cstate=9 overrides any DMI blacklist limit.
1844 processor.nocst [HW,ACPI]
1845 Ignore the _CST method to determine C-states,
1846 instead using the legacy FADT method
1848 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1849 before loading.
1850 See Documentation/blockdev/ramdisk.txt.
1852 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1853 probe for; one of (bare|imps|exps|lifebook|any).
1854 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1855 per second.
1856 psmouse.resetafter= [HW,MOUSE]
1857 Try to reset the device after so many bad packets
1858 (0 = never).
1859 psmouse.resolution=
1860 [HW,MOUSE] Set desired mouse resolution, in dpi.
1861 psmouse.smartscroll=
1862 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1863 0 = disabled, 1 = enabled (default).
1865 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1866 Format:
1867 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1869 pt. [PARIDE]
1870 See Documentation/blockdev/paride.txt.
1872 pty.legacy_count=
1873 [KNL] Number of legacy pty's. Overwrites compiled-in
1874 default number.
1876 quiet [KNL] Disable most log messages
1878 r128= [HW,DRM]
1880 raid= [HW,RAID]
1881 See Documentation/md.txt.
1883 ramdisk_blocksize= [RAM]
1884 See Documentation/blockdev/ramdisk.txt.
1886 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1887 See Documentation/blockdev/ramdisk.txt.
1889 rcupdate.blimit= [KNL,BOOT]
1890 Set maximum number of finished RCU callbacks to process
1891 in one batch.
1893 rcupdate.qhimark= [KNL,BOOT]
1894 Set threshold of queued
1895 RCU callbacks over which batch limiting is disabled.
1897 rcupdate.qlowmark= [KNL,BOOT]
1898 Set threshold of queued RCU callbacks below which
1899 batch limiting is re-enabled.
1901 rdinit= [KNL]
1902 Format: <full_path>
1903 Run specified binary instead of /init from the ramdisk,
1904 used for early userspace startup. See initrd.
1906 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1907 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1908 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1910 relax_domain_level=
1911 [KNL, SMP] Set scheduler's default relax_domain_level.
1912 See Documentation/cpusets.txt.
1914 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1916 reservetop= [X86-32]
1917 Format: nn[KMG]
1918 Reserves a hole at the top of the kernel virtual
1919 address space.
1921 reset_devices [KNL] Force drivers to reset the underlying device
1922 during initialization.
1924 resume= [SWSUSP]
1925 Specify the partition device for software suspend
1927 resume_offset= [SWSUSP]
1928 Specify the offset from the beginning of the partition
1929 given by "resume=" at which the swap header is located,
1930 in <PAGE_SIZE> units (needed only for swap files).
1931 See Documentation/power/swsusp-and-swap-files.txt
1933 retain_initrd [RAM] Keep initrd memory after extraction
1935 rhash_entries= [KNL,NET]
1936 Set number of hash buckets for route cache
1938 riscom8= [HW,SERIAL]
1939 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1941 ro [KNL] Mount root device read-only on boot
1943 root= [KNL] Root filesystem
1945 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1946 mount the root filesystem
1948 rootflags= [KNL] Set root filesystem mount option string
1950 rootfstype= [KNL] Set root filesystem type
1952 rootwait [KNL] Wait (indefinitely) for root device to show up.
1953 Useful for devices that are detected asynchronously
1954 (e.g. USB and MMC devices).
1956 root_plug.vendor_id=
1957 [ROOTPLUG] Override the default vendor ID
1959 root_plug.product_id=
1960 [ROOTPLUG] Override the default product ID
1962 root_plug.debug=
1963 [ROOTPLUG] Enable debugging output
1965 rw [KNL] Mount root device read-write on boot
1967 S [KNL] Run init in single mode
1969 sa1100ir [NET]
1970 See drivers/net/irda/sa1100_ir.c.
1972 sbni= [NET] Granch SBNI12 leased line adapter
1974 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1975 Format: <io>[,<timeout>[,<isapnp>]]
1977 scsi_debug_*= [SCSI]
1978 See drivers/scsi/scsi_debug.c.
1980 scsi_default_dev_flags=
1981 [SCSI] SCSI default device flags
1982 Format: <integer>
1984 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1985 Format: <vendor>:<model>:<flags>
1986 (flags are integer value)
1988 scsi_logging_level= [SCSI] a bit mask of logging levels
1989 See drivers/scsi/scsi_logging.h for bits. Also
1990 settable via sysctl at dev.scsi.logging_level
1991 (/proc/sys/dev/scsi/logging_level).
1992 There is also a nice 'scsi_logging_level' script in the
1993 S390-tools package, available for download at
1994 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
1996 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
1997 discovered. async scans them in kernel threads,
1998 allowing boot to proceed. none ignores them, expecting
1999 user space to do the scan.
2001 selinux [SELINUX] Disable or enable SELinux at boot time.
2002 Format: { "0" | "1" }
2003 See security/selinux/Kconfig help text.
2004 0 -- disable.
2005 1 -- enable.
2006 Default value is set via kernel config option.
2007 If enabled at boot time, /selinux/disable can be used
2008 later to disable prior to initial policy load.
2010 selinux_compat_net =
2011 [SELINUX] Set initial selinux_compat_net flag value.
2012 Format: { "0" | "1" }
2013 0 -- use new secmark-based packet controls
2014 1 -- use legacy packet controls
2015 Default value is 0 (preferred).
2016 Value can be changed at runtime via
2017 /selinux/compat_net.
2019 serialnumber [BUGS=X86-32]
2021 shapers= [NET]
2022 Maximal number of shapers.
2024 show_msr= [x86] show boot-time MSR settings
2025 Format: { <integer> }
2026 Show boot-time (BIOS-initialized) MSR settings.
2027 The parameter means the number of CPUs to show,
2028 for example 1 means boot CPU only.
2030 sim710= [SCSI,HW]
2031 See header of drivers/scsi/sim710.c.
2033 simeth= [IA-64]
2034 simscsi=
2036 slram= [HW,MTD]
2038 slub_debug[=options[,slabs]] [MM, SLUB]
2039 Enabling slub_debug allows one to determine the
2040 culprit if slab objects become corrupted. Enabling
2041 slub_debug can create guard zones around objects and
2042 may poison objects when not in use. Also tracks the
2043 last alloc / free. For more information see
2044 Documentation/vm/slub.txt.
2046 slub_max_order= [MM, SLUB]
2047 Determines the maximum allowed order for slabs.
2048 A high setting may cause OOMs due to memory
2049 fragmentation. For more information see
2050 Documentation/vm/slub.txt.
2052 slub_min_objects= [MM, SLUB]
2053 The minimum number of objects per slab. SLUB will
2054 increase the slab order up to slub_max_order to
2055 generate a sufficiently large slab able to contain
2056 the number of objects indicated. The higher the number
2057 of objects the smaller the overhead of tracking slabs
2058 and the less frequently locks need to be acquired.
2059 For more information see Documentation/vm/slub.txt.
2061 slub_min_order= [MM, SLUB]
2062 Determines the mininum page order for slabs. Must be
2063 lower than slub_max_order.
2064 For more information see Documentation/vm/slub.txt.
2066 slub_nomerge [MM, SLUB]
2067 Disable merging of slabs with similar size. May be
2068 necessary if there is some reason to distinguish
2069 allocs to different slabs. Debug options disable
2070 merging on their own.
2071 For more information see Documentation/vm/slub.txt.
2073 smart2= [HW]
2074 Format: <io1>[,<io2>[,...,<io8>]]
2076 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2077 attempt to substitute SMP alternatives once at boot.
2079 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2080 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2081 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2082 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2083 smsc-ircc2.ircc_irq= [HW] IRQ line
2084 smsc-ircc2.ircc_dma= [HW] DMA channel
2085 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2086 0: Toshiba Satellite 1800 (GP data pin select)
2087 1: Fast pin select (default)
2088 2: ATC IRMode
2090 snd-ad1816a= [HW,ALSA]
2092 snd-ad1848= [HW,ALSA]
2094 snd-ali5451= [HW,ALSA]
2096 snd-als100= [HW,ALSA]
2098 snd-als4000= [HW,ALSA]
2100 snd-azt2320= [HW,ALSA]
2102 snd-cmi8330= [HW,ALSA]
2104 snd-cmipci= [HW,ALSA]
2106 snd-cs4231= [HW,ALSA]
2108 snd-cs4232= [HW,ALSA]
2110 snd-cs4236= [HW,ALSA]
2112 snd-cs4281= [HW,ALSA]
2114 snd-cs46xx= [HW,ALSA]
2116 snd-dt019x= [HW,ALSA]
2118 snd-dummy= [HW,ALSA]
2120 snd-emu10k1= [HW,ALSA]
2122 snd-ens1370= [HW,ALSA]
2124 snd-ens1371= [HW,ALSA]
2126 snd-es968= [HW,ALSA]
2128 snd-es1688= [HW,ALSA]
2130 snd-es18xx= [HW,ALSA]
2132 snd-es1938= [HW,ALSA]
2134 snd-es1968= [HW,ALSA]
2136 snd-fm801= [HW,ALSA]
2138 snd-gusclassic= [HW,ALSA]
2140 snd-gusextreme= [HW,ALSA]
2142 snd-gusmax= [HW,ALSA]
2144 snd-hdsp= [HW,ALSA]
2146 snd-ice1712= [HW,ALSA]
2148 snd-intel8x0= [HW,ALSA]
2150 snd-interwave= [HW,ALSA]
2152 snd-interwave-stb=
2153 [HW,ALSA]
2155 snd-korg1212= [HW,ALSA]
2157 snd-maestro3= [HW,ALSA]
2159 snd-mpu401= [HW,ALSA]
2161 snd-mtpav= [HW,ALSA]
2163 snd-nm256= [HW,ALSA]
2165 snd-opl3sa2= [HW,ALSA]
2167 snd-opti92x-ad1848=
2168 [HW,ALSA]
2170 snd-opti92x-cs4231=
2171 [HW,ALSA]
2173 snd-opti93x= [HW,ALSA]
2175 snd-pmac= [HW,ALSA]
2177 snd-rme32= [HW,ALSA]
2179 snd-rme96= [HW,ALSA]
2181 snd-rme9652= [HW,ALSA]
2183 snd-sb8= [HW,ALSA]
2185 snd-sb16= [HW,ALSA]
2187 snd-sbawe= [HW,ALSA]
2189 snd-serial= [HW,ALSA]
2191 snd-sgalaxy= [HW,ALSA]
2193 snd-sonicvibes= [HW,ALSA]
2195 snd-sun-amd7930=
2196 [HW,ALSA]
2198 snd-sun-cs4231= [HW,ALSA]
2200 snd-trident= [HW,ALSA]
2202 snd-usb-audio= [HW,ALSA,USB]
2204 snd-via82xx= [HW,ALSA]
2206 snd-virmidi= [HW,ALSA]
2208 snd-wavefront= [HW,ALSA]
2210 snd-ymfpci= [HW,ALSA]
2212 softlockup_panic=
2213 [KNL] Should the soft-lockup detector generate panics.
2215 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2216 See Documentation/sonypi.txt
2218 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2219 See Documentation/serial/specialix.txt.
2221 spia_io_base= [HW,MTD]
2222 spia_fio_base=
2223 spia_pedr=
2224 spia_peddr=
2226 sscape= [HW,OSS]
2227 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2229 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2230 See Documentation/scsi/st.txt.
2232 stacktrace [FTRACE]
2233 Enabled the stack tracer on boot up.
2235 sti= [PARISC,HW]
2236 Format: <num>
2237 Set the STI (builtin display/keyboard on the HP-PARISC
2238 machines) console (graphic card) which should be used
2239 as the initial boot-console.
2240 See also comment in drivers/video/console/sticore.c.
2242 sti_font= [HW]
2243 See comment in drivers/video/console/sticore.c.
2245 stifb= [HW]
2246 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2248 sunrpc.pool_mode=
2249 [NFS]
2250 Control how the NFS server code allocates CPUs to
2251 service thread pools. Depending on how many NICs
2252 you have and where their interrupts are bound, this
2253 option will affect which CPUs will do NFS serving.
2254 Note: this parameter cannot be changed while the
2255 NFS server is running.
2257 auto the server chooses an appropriate mode
2258 automatically using heuristics
2259 global a single global pool contains all CPUs
2260 percpu one pool for each CPU
2261 pernode one pool for each NUMA node (equivalent
2262 to global on non-NUMA machines)
2264 swiotlb= [IA-64] Number of I/O TLB slabs
2266 switches= [HW,M68k]
2268 sym53c416= [HW,SCSI]
2269 See header of drivers/scsi/sym53c416.c.
2271 sysrq_always_enabled
2272 [KNL]
2273 Ignore sysrq setting - this boot parameter will
2274 neutralize any effect of /proc/sys/kernel/sysrq.
2275 Useful for debugging.
2277 t128= [HW,SCSI]
2278 See header of drivers/scsi/t128.c.
2280 tdfx= [HW,DRM]
2282 test_suspend= [SUSPEND]
2283 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2284 standby suspend) as the system sleep state to briefly
2285 enter during system startup. The system is woken from
2286 this state using a wakeup-capable RTC alarm.
2288 thash_entries= [KNL,NET]
2289 Set number of hash buckets for TCP connection
2291 thermal.act= [HW,ACPI]
2292 -1: disable all active trip points in all thermal zones
2293 <degrees C>: override all lowest active trip points
2295 thermal.crt= [HW,ACPI]
2296 -1: disable all critical trip points in all thermal zones
2297 <degrees C>: override all critical trip points
2299 thermal.nocrt= [HW,ACPI]
2300 Set to disable actions on ACPI thermal zone
2301 critical and hot trip points.
2303 thermal.off= [HW,ACPI]
2304 1: disable ACPI thermal control
2306 thermal.psv= [HW,ACPI]
2307 -1: disable all passive trip points
2308 <degrees C>: override all passive trip points to this
2309 value
2311 thermal.tzp= [HW,ACPI]
2312 Specify global default ACPI thermal zone polling rate
2313 <deci-seconds>: poll all this frequency
2314 0: no polling (default)
2316 tmscsim= [HW,SCSI]
2317 See comment before function dc390_setup() in
2318 drivers/scsi/tmscsim.c.
2320 topology= [S390]
2321 Format: {off | on}
2322 Specify if the kernel should make use of the cpu
2323 topology informations if the hardware supports these.
2324 The scheduler will make use of these informations and
2325 e.g. base its process migration decisions on it.
2326 Default is off.
2328 tp720= [HW,PS2]
2330 trix= [HW,OSS] MediaTrix AudioTrix Pro
2331 Format:
2332 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2334 tsc= Disable clocksource-must-verify flag for TSC.
2335 Format: <string>
2336 [x86] reliable: mark tsc clocksource as reliable, this
2337 disables clocksource verification at runtime.
2338 Used to enable high-resolution timer mode on older
2339 hardware, and in virtualized environment.
2341 turbografx.map[2|3]= [HW,JOY]
2342 TurboGraFX parallel port interface
2343 Format:
2344 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2345 See also Documentation/input/joystick-parport.txt
2347 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2348 See header of drivers/scsi/u14-34f.c.
2350 uart401= [HW,OSS]
2351 Format: <io>,<irq>
2353 uart6850= [HW,OSS]
2354 Format: <io>,<irq>
2356 uhci-hcd.ignore_oc=
2357 [USB] Ignore overcurrent events (default N).
2358 Some badly-designed motherboards generate lots of
2359 bogus events, for ports that aren't wired to
2360 anything. Set this parameter to avoid log spamming.
2361 Note that genuine overcurrent events won't be
2362 reported either.
2364 unknown_nmi_panic
2365 [X86-32,X86-64]
2366 Set unknown_nmi_panic=1 early on boot.
2368 usbcore.autosuspend=
2369 [USB] The autosuspend time delay (in seconds) used
2370 for newly-detected USB devices (default 2). This
2371 is the time required before an idle device will be
2372 autosuspended. Devices for which the delay is set
2373 to a negative value won't be autosuspended at all.
2375 usbcore.usbfs_snoop=
2376 [USB] Set to log all usbfs traffic (default 0 = off).
2378 usbcore.blinkenlights=
2379 [USB] Set to cycle leds on hubs (default 0 = off).
2381 usbcore.old_scheme_first=
2382 [USB] Start with the old device initialization
2383 scheme (default 0 = off).
2385 usbcore.use_both_schemes=
2386 [USB] Try the other device initialization scheme
2387 if the first one fails (default 1 = enabled).
2389 usbcore.initial_descriptor_timeout=
2390 [USB] Specifies timeout for the initial 64-byte
2391 USB_REQ_GET_DESCRIPTOR request in milliseconds
2392 (default 5000 = 5.0 seconds).
2394 usbhid.mousepoll=
2395 [USBHID] The interval which mice are to be polled at.
2397 usb-storage.delay_use=
2398 [UMS] The delay in seconds before a new device is
2399 scanned for Logical Units (default 5).
2401 usb-storage.quirks=
2402 [UMS] A list of quirks entries to supplement or
2403 override the built-in unusual_devs list. List
2404 entries are separated by commas. Each entry has
2405 the form VID:PID:Flags where VID and PID are Vendor
2406 and Product ID values (4-digit hex numbers) and
2407 Flags is a set of characters, each corresponding
2408 to a common usb-storage quirk flag as follows:
2409 a = SANE_SENSE (collect more than 18 bytes
2410 of sense data);
2411 c = FIX_CAPACITY (decrease the reported
2412 device capacity by one sector);
2413 h = CAPACITY_HEURISTICS (decrease the
2414 reported device capacity by one
2415 sector if the number is odd);
2416 i = IGNORE_DEVICE (don't bind to this
2417 device);
2418 l = NOT_LOCKABLE (don't try to lock and
2419 unlock ejectable media);
2420 m = MAX_SECTORS_64 (don't transfer more
2421 than 64 sectors = 32 KB at a time);
2422 o = CAPACITY_OK (accept the capacity
2423 reported by the device);
2424 r = IGNORE_RESIDUE (the device reports
2425 bogus residue values);
2426 s = SINGLE_LUN (the device has only one
2427 Logical Unit);
2428 w = NO_WP_DETECT (don't test whether the
2429 medium is write-protected).
2430 Example: quirks=0419:aaf5:rl,0421:0433:rc
2432 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2433 kernel's map of available physical RAM.
2435 vdso= [X86-32,SH,x86-64]
2436 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2437 vdso=1: enable VDSO (default)
2438 vdso=0: disable VDSO mapping
2440 vdso32= [X86-32,X86-64]
2441 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2442 vdso32=1: enable 32-bit VDSO (default)
2443 vdso32=0: disable 32-bit VDSO mapping
2445 vector= [IA-64,SMP]
2446 vector=percpu: enable percpu vector domain
2448 video= [FB] Frame buffer configuration
2449 See Documentation/fb/modedb.txt.
2451 vga= [BOOT,X86-32] Select a particular video mode
2452 See Documentation/x86/i386/boot.txt and
2453 Documentation/svga.txt.
2454 Use vga=ask for menu.
2455 This is actually a boot loader parameter; the value is
2456 passed to the kernel using a special protocol.
2458 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2459 size of <nn>. This can be used to increase the
2460 minimum size (128MB on x86). It can also be used to
2461 decrease the size and leave more room for directly
2462 mapped kernel RAM.
2464 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2465 Format: <command>
2467 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2468 Format: <command>
2470 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2471 Format: <command>
2473 waveartist= [HW,OSS]
2474 Format: <io>,<irq>,<dma>,<dma2>
2476 wd33c93= [HW,SCSI]
2477 See header of drivers/scsi/wd33c93.c.
2479 wd7000= [HW,SCSI]
2480 See header of drivers/scsi/wd7000.c.
2482 wdt= [WDT] Watchdog
2483 See Documentation/watchdog/wdt.txt.
2485 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2486 xd_geo= See header of drivers/block/xd.c.
2488 xirc2ps_cs= [NET,PCMCIA]
2489 Format:
2490 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2492 norandmaps Don't use address space randomization. Equivalent to
2493 echo 0 > /proc/sys/kernel/randomize_va_space
2495 ______________________________________________________________________
2497 TODO:
2499 Add documentation for ALSA options.
2500 Add more DRM drivers.