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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/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 | rsdt }
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-core.nodma= [HW] (E)IDE subsystem
872 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
873 .vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom
874 .chs .ignore_cable are additional options
875 See Documentation/ide/ide.txt.
877 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
878 See Documentation/ide/ide.txt.
880 idle= [X86]
881 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
882 Poll forces a polling idle loop that can slightly
883 improve the performance of waking up a idle CPU, but
884 will use a lot of power and make the system run hot.
885 Not recommended.
886 idle=mwait: On systems which support MONITOR/MWAIT but
887 the kernel chose to not use it because it doesn't save
888 as much power as a normal idle loop, use the
889 MONITOR/MWAIT idle loop anyways. Performance should be
890 the same as idle=poll.
891 idle=halt: Halt is forced to be used for CPU idle.
892 In such case C2/C3 won't be used again.
893 idle=nomwait: Disable mwait for CPU C-states
895 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
896 Claim all unknown PCI IDE storage controllers.
898 ignore_loglevel [KNL]
899 Ignore loglevel setting - this will print /all/
900 kernel messages to the console. Useful for debugging.
902 ihash_entries= [KNL]
903 Set number of hash buckets for inode cache.
905 in2000= [HW,SCSI]
906 See header of drivers/scsi/in2000.c.
908 init= [KNL]
909 Format: <full_path>
910 Run specified binary instead of /sbin/init as init
911 process.
913 initcall_debug [KNL] Trace initcalls as they are executed. Useful
914 for working out where the kernel is dying during
915 startup.
917 initrd= [BOOT] Specify the location of the initial ramdisk
919 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
920 Format: <irq>
922 inttest= [IA64]
924 iomem= Disable strict checking of access to MMIO memory
925 strict regions from userspace.
926 relaxed
928 iommu= [x86]
929 off
930 force
931 noforce
932 biomerge
933 panic
934 nopanic
935 merge
936 nomerge
937 forcesac
938 soft
941 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
942 on
943 Enable intel iommu driver.
944 off
945 Disable intel iommu driver.
946 igfx_off [Default Off]
947 By default, gfx is mapped as normal device. If a gfx
948 device has a dedicated DMAR unit, the DMAR unit is
949 bypassed by not enabling DMAR with this option. In
950 this case, gfx device will use physical address for
951 DMA.
952 forcedac [x86_64]
953 With this option iommu will not optimize to look
954 for io virtual address below 32 bit forcing dual
955 address cycle on pci bus for cards supporting greater
956 than 32 bit addressing. The default is to look
957 for translation below 32 bit and if not available
958 then look in the higher range.
959 strict [Default Off]
960 With this option on every unmap_single operation will
961 result in a hardware IOTLB flush operation as opposed
962 to batching them for performance.
964 io_delay= [X86-32,X86-64] I/O delay method
965 0x80
966 Standard port 0x80 based delay
967 0xed
968 Alternate port 0xed based delay (needed on some systems)
969 udelay
970 Simple two microseconds delay
971 none
972 No delay
974 io7= [HW] IO7 for Marvel based alpha systems
975 See comment before marvel_specify_io7 in
976 arch/alpha/kernel/core_marvel.c.
978 ip= [IP_PNP]
979 See Documentation/filesystems/nfsroot.txt.
981 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
982 See comment before ip2_setup() in
983 drivers/char/ip2/ip2base.c.
985 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
986 See header of drivers/scsi/ips.c.
988 ports= [IP_VS_FTP] IPVS ftp helper module
989 Default is 21.
990 Up to 8 (IP_VS_APP_MAX_PORTS) ports
991 may be specified.
992 Format: <port>,<port>....
994 irqfixup [HW]
995 When an interrupt is not handled search all handlers
996 for it. Intended to get systems with badly broken
997 firmware running.
999 irqpoll [HW]
1000 When an interrupt is not handled search all handlers
1001 for it. Also check all handlers each timer
1002 interrupt. Intended to get systems with badly broken
1003 firmware running.
1005 isapnp= [ISAPNP]
1006 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1008 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1009 Format:
1010 <cpu number>,...,<cpu number>
1011 or
1012 <cpu number>-<cpu number>
1013 (must be a positive range in ascending order)
1014 or a mixture
1015 <cpu number>,...,<cpu number>-<cpu number>
1017 This option can be used to specify one or more CPUs
1018 to isolate from the general SMP balancing and scheduling
1019 algorithms. You can move a process onto or off an
1020 "isolated" CPU via the CPU affinity syscalls or cpuset.
1021 <cpu number> begins at 0 and the maximum value is
1022 "number of CPUs in system - 1".
1024 This option is the preferred way to isolate CPUs. The
1025 alternative -- manually setting the CPU mask of all
1026 tasks in the system -- can cause problems and
1027 suboptimal load balancer performance.
1029 iucv= [HW,NET]
1031 js= [HW,JOY] Analog joystick
1032 See Documentation/input/joystick.txt.
1034 kernelcore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1035 specifies the amount of memory usable by the kernel
1036 for non-movable allocations. The requested amount is
1037 spread evenly throughout all nodes in the system. The
1038 remaining memory in each node is used for Movable
1039 pages. In the event, a node is too small to have both
1040 kernelcore and Movable pages, kernelcore pages will
1041 take priority and other nodes will have a larger number
1042 of kernelcore pages. The Movable zone is used for the
1043 allocation of pages that may be reclaimed or moved
1044 by the page migration subsystem. This means that
1045 HugeTLB pages may not be allocated from this zone.
1046 Note that allocations like PTEs-from-HighMem still
1047 use the HighMem zone if it exists, and the Normal
1048 zone if it does not.
1050 movablecore=nn[KMG] [KNL,X86-32,IA-64,PPC,X86-64] This parameter
1051 is similar to kernelcore except it specifies the
1052 amount of memory used for migratable allocations.
1053 If both kernelcore and movablecore is specified,
1054 then kernelcore will be at *least* the specified
1055 value but may be more. If movablecore on its own
1056 is specified, the administrator must be careful
1057 that the amount of memory usable for all allocations
1058 is not too small.
1060 keepinitrd [HW,ARM]
1062 kstack=N [X86-32,X86-64] Print N words from the kernel stack
1063 in oops dumps.
1065 kgdboc= [HW] kgdb over consoles.
1066 Requires a tty driver that supports console polling.
1067 (only serial suported for now)
1068 Format: <serial_device>[,baud]
1070 kmac= [MIPS] korina ethernet MAC address.
1071 Configure the RouterBoard 532 series on-chip
1072 Ethernet adapter MAC address.
1074 l2cr= [PPC]
1076 l3cr= [PPC]
1078 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1079 disabled it.
1081 lapic_timer_c2_ok [X86-32,x86-64,APIC] trust the local apic timer
1082 in C2 power state.
1084 libata.dma= [LIBATA] DMA control
1085 libata.dma=0 Disable all PATA and SATA DMA
1086 libata.dma=1 PATA and SATA Disk DMA only
1087 libata.dma=2 ATAPI (CDROM) DMA only
1088 libata.dma=4 Compact Flash DMA only
1089 Combinations also work, so libata.dma=3 enables DMA
1090 for disks and CDROMs, but not CFs.
1092 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1093 when set.
1094 Format: <int>
1096 libata.force= [LIBATA] Force configurations. The format is comma
1097 separated list of "[ID:]VAL" where ID is
1098 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1099 matching port, link or device. Basically, it matches
1100 the ATA ID string printed on console by libata. If
1101 the whole ID part is omitted, the last PORT and DEVICE
1102 values are used. If ID hasn't been specified yet, the
1103 configuration applies to all ports, links and devices.
1105 If only DEVICE is omitted, the parameter applies to
1106 the port and all links and devices behind it. DEVICE
1107 number of 0 either selects the first device or the
1108 first fan-out link behind PMP device. It does not
1109 select the host link. DEVICE number of 15 selects the
1110 host link and device attached to it.
1112 The VAL specifies the configuration to force. As long
1113 as there's no ambiguity shortcut notation is allowed.
1114 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1115 The following configurations can be forced.
1117 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1118 Any ID with matching PORT is used.
1120 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1122 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1123 udma[/][16,25,33,44,66,100,133] notation is also
1124 allowed.
1126 * [no]ncq: Turn on or off NCQ.
1128 * nohrst, nosrst, norst: suppress hard, soft
1129 and both resets.
1131 If there are multiple matching configurations changing
1132 the same attribute, the last one is used.
1134 lmb=debug [KNL] Enable lmb debug messages.
1136 load_ramdisk= [RAM] List of ramdisks to load from floppy
1137 See Documentation/blockdev/ramdisk.txt.
1139 lockd.nlm_grace_period=P [NFS] Assign grace period.
1140 Format: <integer>
1142 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1143 Format: <integer>
1145 lockd.nlm_timeout=T [NFS] Assign timeout value.
1146 Format: <integer>
1148 lockd.nlm_udpport=M [NFS] Assign UDP port.
1149 Format: <integer>
1151 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1152 Format: <irq>
1154 loglevel= All Kernel Messages with a loglevel smaller than the
1155 console loglevel will be printed to the console. It can
1156 also be changed with klogd or other programs. The
1157 loglevels are defined as follows:
1159 0 (KERN_EMERG) system is unusable
1160 1 (KERN_ALERT) action must be taken immediately
1161 2 (KERN_CRIT) critical conditions
1162 3 (KERN_ERR) error conditions
1163 4 (KERN_WARNING) warning conditions
1164 5 (KERN_NOTICE) normal but significant condition
1165 6 (KERN_INFO) informational
1166 7 (KERN_DEBUG) debug-level messages
1168 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1169 Format: { n | nk | nM }
1170 n must be a power of two. The default size
1171 is set in the kernel config file.
1173 logo.nologo [FB] Disables display of the built-in Linux logo.
1174 This may be used to provide more screen space for
1175 kernel log messages and is useful when debugging
1176 kernel boot problems.
1178 lp=0 [LP] Specify parallel ports to use, e.g,
1179 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1180 lp=reset first parallel port). 'lp=0' disables the
1181 lp=auto printer driver. 'lp=reset' (which can be
1182 specified in addition to the ports) causes
1183 attached printers to be reset. Using
1184 lp=port1,port2,... specifies the parallel ports
1185 to associate lp devices with, starting with
1186 lp0. A port specification may be 'none' to skip
1187 that lp device, or a parport name such as
1188 'parport0'. Specifying 'lp=auto' instead of a
1189 port specification list means that device IDs
1190 from each port should be examined, to see if
1191 an IEEE 1284-compliant printer is attached; if
1192 so, the driver will manage that printer.
1193 See also header of drivers/char/lp.c.
1195 lpj=n [KNL]
1196 Sets loops_per_jiffy to given constant, thus avoiding
1197 time-consuming boot-time autodetection (up to 250 ms per
1198 CPU). 0 enables autodetection (default). To determine
1199 the correct value for your kernel, boot with normal
1200 autodetection and see what value is printed. Note that
1201 on SMP systems the preset will be applied to all CPUs,
1202 which is likely to cause problems if your CPUs need
1203 significantly divergent settings. An incorrect value
1204 will cause delays in the kernel to be wrong, leading to
1205 unpredictable I/O errors and other breakage. Although
1206 unlikely, in the extreme case this might damage your
1207 hardware.
1209 ltpc= [NET]
1210 Format: <io>,<irq>,<dma>
1212 mac5380= [HW,SCSI] Format:
1213 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1215 machvec= [IA64] Force the use of a particular machine-vector
1216 (machvec) in a generic kernel.
1217 Example: machvec=hpzx1_swiotlb
1219 max_loop= [LOOP] Maximum number of loopback devices that can
1220 be mounted
1221 Format: <1-256>
1223 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1224 should make use of. maxcpus=n : n >= 0 limits the
1225 kernel to using 'n' processors. n=0 is a special case,
1226 it is equivalent to "nosmp", which also disables
1227 the IO APIC.
1229 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater than
1230 or equal to this physical address is ignored.
1232 max_luns= [SCSI] Maximum number of LUNs to probe.
1233 Should be between 1 and 2^32-1.
1235 max_report_luns=
1236 [SCSI] Maximum number of LUNs received.
1237 Should be between 1 and 16384.
1239 mcatest= [IA-64]
1241 mce [X86-32] Machine Check Exception
1243 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1245 md= [HW] RAID subsystems devices and level
1246 See Documentation/md.txt.
1248 mdacon= [MDA]
1249 Format: <first>,<last>
1250 Specifies range of consoles to be captured by the MDA.
1252 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1253 Amount of memory to be used when the kernel is not able
1254 to see the whole system memory or for test.
1255 [X86-32] Use together with memmap= to avoid physical
1256 address space collisions. Without memmap= PCI devices
1257 could be placed at addresses belonging to unused RAM.
1259 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1260 memory.
1262 memchunk=nn[KMG]
1263 [KNL,SH] Allow user to override the default size for
1264 per-device physically contiguous DMA buffers.
1266 memmap=exactmap [KNL,X86-32,X86_64] Enable setting of an exact
1267 E820 memory map, as specified by the user.
1268 Such memmap=exactmap lines can be constructed based on
1269 BIOS output or other requirements. See the memmap=nn@ss
1270 option description.
1272 memmap=nn[KMG]@ss[KMG]
1273 [KNL] Force usage of a specific region of memory
1274 Region of memory to be used, from ss to ss+nn.
1276 memmap=nn[KMG]#ss[KMG]
1277 [KNL,ACPI] Mark specific memory as ACPI data.
1278 Region of memory to be used, from ss to ss+nn.
1280 memmap=nn[KMG]$ss[KMG]
1281 [KNL,ACPI] Mark specific memory as reserved.
1282 Region of memory to be used, from ss to ss+nn.
1283 Example: Exclude memory from 0x18690000-0x1869ffff
1284 memmap=64K$0x18690000
1285 or
1286 memmap=0x10000$0x18690000
1288 memory_corruption_check=0/1 [X86]
1289 Some BIOSes seem to corrupt the first 64k of
1290 memory when doing things like suspend/resume.
1291 Setting this option will scan the memory
1292 looking for corruption. Enabling this will
1293 both detect corruption and prevent the kernel
1294 from using the memory being corrupted.
1295 However, its intended as a diagnostic tool; if
1296 repeatable BIOS-originated corruption always
1297 affects the same memory, you can use memmap=
1298 to prevent the kernel from using that memory.
1300 memory_corruption_check_size=size [X86]
1301 By default it checks for corruption in the low
1302 64k, making this memory unavailable for normal
1303 use. Use this parameter to scan for
1304 corruption in more or less memory.
1306 memory_corruption_check_period=seconds [X86]
1307 By default it checks for corruption every 60
1308 seconds. Use this parameter to check at some
1309 other rate. 0 disables periodic checking.
1311 memtest= [KNL,X86] Enable memtest
1312 Format: <integer>
1313 default : 0 <disable>
1314 Specifies the number of memtest passes to be
1315 performed. Each pass selects another test
1316 pattern from a given set of patterns. Memtest
1317 fills the memory with this pattern, validates
1318 memory contents and reserves bad memory
1319 regions that are detected.
1321 meye.*= [HW] Set MotionEye Camera parameters
1322 See Documentation/video4linux/meye.txt.
1324 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1325 Multi-Function General Purpose Timers on AMD Geode
1326 platforms.
1328 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1329 the BIOS has incorrectly applied a workaround. TinyBIOS
1330 version 0.98 is known to be affected, 0.99 fixes the
1331 problem by letting the user disable the workaround.
1333 mga= [HW,DRM]
1335 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1336 physical address is ignored.
1338 mminit_loglevel=
1339 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1340 parameter allows control of the logging verbosity for
1341 the additional memory initialisation checks. A value
1342 of 0 disables mminit logging and a level of 4 will
1343 log everything. Information is printed at KERN_DEBUG
1344 so loglevel=8 may also need to be specified.
1346 mousedev.tap_time=
1347 [MOUSE] Maximum time between finger touching and
1348 leaving touchpad surface for touch to be considered
1349 a tap and be reported as a left button click (for
1350 touchpads working in absolute mode only).
1351 Format: <msecs>
1352 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1353 reporting absolute coordinates, such as tablets
1354 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1355 reporting absolute coordinates, such as tablets
1357 mpu401= [HW,OSS]
1358 Format: <io>,<irq>
1360 MTD_Partition= [MTD]
1361 Format: <name>,<region-number>,<size>,<offset>
1363 MTD_Region= [MTD] Format:
1364 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1366 mtdparts= [MTD]
1367 See drivers/mtd/cmdlinepart.c.
1369 mtdset= [ARM]
1370 ARM/S3C2412 JIVE boot control
1372 See arch/arm/mach-s3c2412/mach-jive.c
1374 mtouchusb.raw_coordinates=
1375 [HW] Make the MicroTouch USB driver use raw coordinates
1376 ('y', default) or cooked coordinates ('n')
1378 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1380 NCR_D700= [HW,SCSI]
1381 See header of drivers/scsi/NCR_D700.c.
1383 ncr5380= [HW,SCSI]
1385 ncr53c400= [HW,SCSI]
1387 ncr53c400a= [HW,SCSI]
1389 ncr53c406a= [HW,SCSI]
1391 ncr53c8xx= [HW,SCSI]
1393 netdev= [NET] Network devices parameters
1394 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1395 Note that mem_start is often overloaded to mean
1396 something different and driver-specific.
1397 This usage is only documented in each driver source
1398 file if at all.
1400 nf_conntrack.acct=
1401 [NETFILTER] Enable connection tracking flow accounting
1402 0 to disable accounting
1403 1 to enable accounting
1404 Default value depends on CONFIG_NF_CT_ACCT that is
1405 going to be removed in 2.6.29.
1407 nfsaddrs= [NFS]
1408 See Documentation/filesystems/nfsroot.txt.
1410 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1411 See Documentation/filesystems/nfsroot.txt.
1413 nfs.callback_tcpport=
1414 [NFS] set the TCP port on which the NFSv4 callback
1415 channel should listen.
1417 nfs.idmap_cache_timeout=
1418 [NFS] set the maximum lifetime for idmapper cache
1419 entries.
1421 nfs.enable_ino64=
1422 [NFS] enable 64-bit inode numbers.
1423 If zero, the NFS client will fake up a 32-bit inode
1424 number for the readdir() and stat() syscalls instead
1425 of returning the full 64-bit number.
1426 The default is to return 64-bit inode numbers.
1428 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1429 when a NMI is triggered.
1430 Format: [state][,regs][,debounce][,die]
1432 nmi_watchdog= [KNL,BUGS=X86-32,X86-64] Debugging features for SMP kernels
1433 Format: [panic,][num]
1434 Valid num: 0,1,2
1435 0 - turn nmi_watchdog off
1436 1 - use the IO-APIC timer for the NMI watchdog
1437 2 - use the local APIC for the NMI watchdog using
1438 a performance counter. Note: This will use one performance
1439 counter and the local APIC's performance vector.
1440 When panic is specified panic when an NMI watchdog timeout occurs.
1441 This is useful when you use a panic=... timeout and need the box
1442 quickly up again.
1443 Instead of 1 and 2 it is possible to use the following
1444 symbolic names: lapic and ioapic
1445 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1447 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1448 emulation library even if a 387 maths coprocessor
1449 is present.
1451 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1452 caches in the slab allocator. Saves per-node memory,
1453 but will impact performance.
1455 noalign [KNL,ARM]
1457 noapic [SMP,APIC] Tells the kernel to not make use of any
1458 IOAPICs that may be present in the system.
1460 nobats [PPC] Do not use BATs for mapping kernel lowmem
1461 on "Classic" PPC cores.
1463 nocache [ARM]
1465 nodelayacct [KNL] Disable per-task delay accounting
1467 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1469 nodsp [SH] Disable hardware DSP at boot time.
1471 noefi [X86-32,X86-64] Disable EFI runtime services support.
1473 noexec [IA-64]
1475 noexec [X86-32,X86-64]
1476 On X86-32 available only on PAE configured kernels.
1477 noexec=on: enable non-executable mappings (default)
1478 noexec=off: disable non-executable mappings
1480 noexec32 [X86-64]
1481 This affects only 32-bit executables.
1482 noexec32=on: enable non-executable mappings (default)
1483 read doesn't imply executable mappings
1484 noexec32=off: disable non-executable mappings
1485 read implies executable mappings
1487 nofpu [SH] Disable hardware FPU at boot time.
1489 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1490 register save and restore. The kernel will only save
1491 legacy floating-point registers on task switch.
1493 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1495 nohlt [BUGS=ARM,SH]
1497 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1498 instruction doesn't work correctly and not to
1499 use it.
1501 no_file_caps Tells the kernel not to honor file capabilities. The
1502 only way then for a file to be executed with privilege
1503 is to be setuid root or executed by root.
1505 nohalt [IA-64] Tells the kernel not to use the power saving
1506 function PAL_HALT_LIGHT when idle. This increases
1507 power-consumption. On the positive side, it reduces
1508 interrupt wake-up latency, which may improve performance
1509 in certain environments such as networked servers or
1510 real-time systems.
1512 nohz= [KNL] Boottime enable/disable dynamic ticks
1513 Valid arguments: on, off
1514 Default: on
1516 noirqdebug [X86-32] Disables the code which attempts to detect and
1517 disable unhandled interrupt sources.
1519 no_timer_check [X86-32,X86_64,APIC] Disables the code which tests for
1520 broken timer IRQ sources.
1522 noisapnp [ISAPNP] Disables ISA PnP code.
1524 noinitrd [RAM] Tells the kernel not to load any configured
1525 initial RAM disk.
1527 nointroute [IA-64]
1529 nojitter [IA64] Disables jitter checking for ITC timers.
1531 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1533 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1535 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1537 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
1538 default x2apic cluster mode on platforms
1539 supporting x2apic.
1541 noltlbs [PPC] Do not use large page/tlb entries for kernel
1542 lowmem mapping on PPC40x.
1544 nomca [IA-64] Disable machine check abort handling
1546 nomce [X86-32] Machine Check Exception
1548 nomfgpt [X86-32] Disable Multi-Function General Purpose
1549 Timer usage (for AMD Geode machines).
1551 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1553 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1554 with UP alternatives
1556 noresidual [PPC] Don't use residual data on PReP machines.
1558 noresume [SWSUSP] Disables resume and restores original swap
1559 space.
1561 no-scroll [VGA] Disables scrollback.
1562 This is required for the Braillex ib80-piezo Braille
1563 reader made by F.H. Papenmeier (Germany).
1565 nosbagart [IA-64]
1567 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1569 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1570 and disable the IO APIC. legacy for "maxcpus=0".
1572 nosoftlockup [KNL] Disable the soft-lockup detector.
1574 noswapaccount [KNL] Disable accounting of swap in memory resource
1575 controller. (See Documentation/controllers/memory.txt)
1577 nosync [HW,M68K] Disables sync negotiation for all devices.
1579 notsc [BUGS=X86-32] Disable Time Stamp Counter
1581 nousb [USB] Disable the USB subsystem
1583 nowb [ARM]
1585 nptcg= [IA64] Override max number of concurrent global TLB
1586 purges which is reported from either PAL_VM_SUMMARY or
1587 SAL PALO.
1589 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1590 one of ['zone', 'node', 'default'] can be specified
1591 This can be set from sysctl after boot.
1592 See Documentation/sysctl/vm.txt for details.
1594 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1596 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1597 See Documentation/debugging-via-ohci1394.txt for more
1598 info.
1600 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1601 Rather than timing out after 20 ms if an EC
1602 command is not properly ACKed, override the length
1603 of the timeout. We have interrupts disabled while
1604 waiting for the ACK, so if this is set too high
1605 interrupts *may* be lost!
1607 opl3= [HW,OSS]
1608 Format: <io>
1610 oprofile.timer= [HW]
1611 Use timer interrupt instead of performance counters
1613 osst= [HW,SCSI] SCSI Tape Driver
1614 Format: <buffer_size>,<write_threshold>
1615 See also Documentation/scsi/st.txt.
1617 panic= [KNL] Kernel behaviour on panic
1618 Format: <timeout>
1620 parkbd.port= [HW] Parallel port number the keyboard adapter is
1621 connected to, default is 0.
1622 Format: <parport#>
1623 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1624 0 for XT, 1 for AT (default is AT).
1625 Format: <mode>
1627 parport= [HW,PPT] Specify parallel ports. 0 disables.
1628 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1629 Use 'auto' to force the driver to use any
1630 IRQ/DMA settings detected (the default is to
1631 ignore detected IRQ/DMA settings because of
1632 possible conflicts). You can specify the base
1633 address, IRQ, and DMA settings; IRQ and DMA
1634 should be numbers, or 'auto' (for using detected
1635 settings on that particular port), or 'nofifo'
1636 (to avoid using a FIFO even if it is detected).
1637 Parallel ports are assigned in the order they
1638 are specified on the command line, starting
1639 with parport0.
1641 parport_init_mode= [HW,PPT]
1642 Configure VIA parallel port to operate in
1643 a specific mode. This is necessary on Pegasos
1644 computer where firmware has no options for setting
1645 up parallel port mode and sets it to spp.
1646 Currently this function knows 686a and 8231 chips.
1647 Format: [spp|ps2|epp|ecp|ecpepp]
1649 pas2= [HW,OSS] Format:
1650 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1652 pas16= [HW,SCSI]
1653 See header of drivers/scsi/pas16.c.
1655 pause_on_oops=
1656 Halt all CPUs after the first oops has been printed for
1657 the specified number of seconds. This is to be used if
1658 your oopses keep scrolling off the screen.
1660 pcbit= [HW,ISDN]
1662 pcd. [PARIDE]
1663 See header of drivers/block/paride/pcd.c.
1664 See also Documentation/blockdev/paride.txt.
1666 pci=option[,option...] [PCI] various PCI subsystem options:
1667 off [X86] don't probe for the PCI bus
1668 bios [X86-32] force use of PCI BIOS, don't access
1669 the hardware directly. Use this if your machine
1670 has a non-standard PCI host bridge.
1671 nobios [X86-32] disallow use of PCI BIOS, only direct
1672 hardware access methods are allowed. Use this
1673 if you experience crashes upon bootup and you
1674 suspect they are caused by the BIOS.
1675 conf1 [X86] Force use of PCI Configuration
1676 Mechanism 1.
1677 conf2 [X86] Force use of PCI Configuration
1678 Mechanism 2.
1679 noaer [PCIE] If the PCIEAER kernel config parameter is
1680 enabled, this kernel boot option can be used to
1681 disable the use of PCIE advanced error reporting.
1682 nodomains [PCI] Disable support for multiple PCI
1683 root domains (aka PCI segments, in ACPI-speak).
1684 nommconf [X86-32,X86_64] Disable use of MMCONFIG for PCI
1685 Configuration
1686 nomsi [MSI] If the PCI_MSI kernel config parameter is
1687 enabled, this kernel boot option can be used to
1688 disable the use of MSI interrupts system-wide.
1689 noioapicquirk [APIC] Disable all boot interrupt quirks.
1690 Safety option to keep boot IRQs enabled. This
1691 should never be necessary.
1692 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1693 primary IO-APIC for bridges that cannot disable
1694 boot IRQs. This fixes a source of spurious IRQs
1695 when the system masks IRQs.
1696 noioapicreroute [APIC] Disable workaround that uses the
1697 boot IRQ equivalent of an IRQ that connects to
1698 a chipset where boot IRQs cannot be disabled.
1699 The opposite of ioapicreroute.
1700 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1701 routing table. These calls are known to be buggy
1702 on several machines and they hang the machine
1703 when used, but on other computers it's the only
1704 way to get the interrupt routing table. Try
1705 this option if the kernel is unable to allocate
1706 IRQs or discover secondary PCI buses on your
1707 motherboard.
1708 rom [X86] Assign address space to expansion ROMs.
1709 Use with caution as certain devices share
1710 address decoders between ROMs and other
1711 resources.
1712 norom [X86] Do not assign address space to
1713 expansion ROMs that do not already have
1714 BIOS assigned address ranges.
1715 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1716 assigned automatically to PCI devices. You can
1717 make the kernel exclude IRQs of your ISA cards
1718 this way.
1719 pirqaddr=0xAAAAA [X86] Specify the physical address
1720 of the PIRQ table (normally generated
1721 by the BIOS) if it is outside the
1722 F0000h-100000h range.
1723 lastbus=N [X86] Scan all buses thru bus #N. Can be
1724 useful if the kernel is unable to find your
1725 secondary buses and you want to tell it
1726 explicitly which ones they are.
1727 assign-busses [X86] Always assign all PCI bus
1728 numbers ourselves, overriding
1729 whatever the firmware may have done.
1730 usepirqmask [X86] Honor the possible IRQ mask stored
1731 in the BIOS $PIR table. This is needed on
1732 some systems with broken BIOSes, notably
1733 some HP Pavilion N5400 and Omnibook XE3
1734 notebooks. This will have no effect if ACPI
1735 IRQ routing is enabled.
1736 noacpi [X86] Do not use ACPI for IRQ routing
1737 or for PCI scanning.
1738 use_crs [X86] Use _CRS for PCI resource
1739 allocation.
1740 routeirq Do IRQ routing for all PCI devices.
1741 This is normally done in pci_enable_device(),
1742 so this option is a temporary workaround
1743 for broken drivers that don't call it.
1744 skip_isa_align [X86] do not align io start addr, so can
1745 handle more pci cards
1746 firmware [ARM] Do not re-enumerate the bus but instead
1747 just use the configuration from the
1748 bootloader. This is currently used on
1749 IXP2000 systems where the bus has to be
1750 configured a certain way for adjunct CPUs.
1751 noearly [X86] Don't do any early type 1 scanning.
1752 This might help on some broken boards which
1753 machine check when some devices' config space
1754 is read. But various workarounds are disabled
1755 and some IOMMU drivers will not work.
1756 bfsort Sort PCI devices into breadth-first order.
1757 This sorting is done to get a device
1758 order compatible with older (<= 2.4) kernels.
1759 nobfsort Don't sort PCI devices into breadth-first order.
1760 cbiosize=nn[KMG] The fixed amount of bus space which is
1761 reserved for the CardBus bridge's IO window.
1762 The default value is 256 bytes.
1763 cbmemsize=nn[KMG] The fixed amount of bus space which is
1764 reserved for the CardBus bridge's memory
1765 window. The default value is 64 megabytes.
1767 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1768 Management.
1769 off Disable ASPM.
1770 force Enable ASPM even on devices that claim not to support it.
1771 WARNING: Forcing ASPM on may cause system lockups.
1773 pcmv= [HW,PCMCIA] BadgePAD 4
1775 pd. [PARIDE]
1776 See Documentation/blockdev/paride.txt.
1778 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1779 boot time.
1780 Format: { 0 | 1 }
1781 See arch/parisc/kernel/pdc_chassis.c
1783 pf. [PARIDE]
1784 See Documentation/blockdev/paride.txt.
1786 pg. [PARIDE]
1787 See Documentation/blockdev/paride.txt.
1789 pirq= [SMP,APIC] Manual mp-table setup
1790 See Documentation/x86/i386/IO-APIC.txt.
1792 plip= [PPT,NET] Parallel port network link
1793 Format: { parport<nr> | timid | 0 }
1794 See also Documentation/parport.txt.
1796 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1797 Override pmtimer IOPort with a hex value.
1798 e.g. pmtmr=0x508
1800 pnp.debug [PNP]
1801 Enable PNP debug messages. This depends on the
1802 CONFIG_PNP_DEBUG_MESSAGES option.
1804 pnpacpi= [ACPI]
1805 { off }
1807 pnpbios= [ISAPNP]
1808 { on | off | curr | res | no-curr | no-res }
1810 pnp_reserve_irq=
1811 [ISAPNP] Exclude IRQs for the autoconfiguration
1813 pnp_reserve_dma=
1814 [ISAPNP] Exclude DMAs for the autoconfiguration
1816 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1817 Ranges are in pairs (I/O port base and size).
1819 pnp_reserve_mem=
1820 [ISAPNP] Exclude memory regions for the
1821 autoconfiguration.
1822 Ranges are in pairs (memory base and size).
1824 dynamic_printk Enables pr_debug()/dev_dbg() calls if
1825 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
1826 These can also be switched on/off via
1827 <debugfs>/dynamic_printk/modules
1829 print-fatal-signals=
1830 [KNL] debug: print fatal signals
1831 print-fatal-signals=1: print segfault info to
1832 the kernel console.
1833 default: off.
1835 printk.time= Show timing data prefixed to each printk message line
1836 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1838 profile= [KNL] Enable kernel profiling via /proc/profile
1839 Format: [schedule,]<number>
1840 Param: "schedule" - profile schedule points.
1841 Param: <number> - step/bucket size as a power of 2 for
1842 statistical time based profiling.
1843 Param: "sleep" - profile D-state sleeping (millisecs).
1844 Requires CONFIG_SCHEDSTATS
1845 Param: "kvm" - profile VM exits.
1847 processor.max_cstate= [HW,ACPI]
1848 Limit processor to maximum C-state
1849 max_cstate=9 overrides any DMI blacklist limit.
1851 processor.nocst [HW,ACPI]
1852 Ignore the _CST method to determine C-states,
1853 instead using the legacy FADT method
1855 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1856 before loading.
1857 See Documentation/blockdev/ramdisk.txt.
1859 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1860 probe for; one of (bare|imps|exps|lifebook|any).
1861 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1862 per second.
1863 psmouse.resetafter= [HW,MOUSE]
1864 Try to reset the device after so many bad packets
1865 (0 = never).
1866 psmouse.resolution=
1867 [HW,MOUSE] Set desired mouse resolution, in dpi.
1868 psmouse.smartscroll=
1869 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1870 0 = disabled, 1 = enabled (default).
1872 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1873 Format:
1874 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1876 pt. [PARIDE]
1877 See Documentation/blockdev/paride.txt.
1879 pty.legacy_count=
1880 [KNL] Number of legacy pty's. Overwrites compiled-in
1881 default number.
1883 quiet [KNL] Disable most log messages
1885 r128= [HW,DRM]
1887 raid= [HW,RAID]
1888 See Documentation/md.txt.
1890 ramdisk_blocksize= [RAM]
1891 See Documentation/blockdev/ramdisk.txt.
1893 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1894 See Documentation/blockdev/ramdisk.txt.
1896 rcupdate.blimit= [KNL,BOOT]
1897 Set maximum number of finished RCU callbacks to process
1898 in one batch.
1900 rcupdate.qhimark= [KNL,BOOT]
1901 Set threshold of queued
1902 RCU callbacks over which batch limiting is disabled.
1904 rcupdate.qlowmark= [KNL,BOOT]
1905 Set threshold of queued RCU callbacks below which
1906 batch limiting is re-enabled.
1908 rdinit= [KNL]
1909 Format: <full_path>
1910 Run specified binary instead of /init from the ramdisk,
1911 used for early userspace startup. See initrd.
1913 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1914 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1915 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1917 relax_domain_level=
1918 [KNL, SMP] Set scheduler's default relax_domain_level.
1919 See Documentation/cpusets.txt.
1921 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1923 reservetop= [X86-32]
1924 Format: nn[KMG]
1925 Reserves a hole at the top of the kernel virtual
1926 address space.
1928 reset_devices [KNL] Force drivers to reset the underlying device
1929 during initialization.
1931 resume= [SWSUSP]
1932 Specify the partition device for software suspend
1934 resume_offset= [SWSUSP]
1935 Specify the offset from the beginning of the partition
1936 given by "resume=" at which the swap header is located,
1937 in <PAGE_SIZE> units (needed only for swap files).
1938 See Documentation/power/swsusp-and-swap-files.txt
1940 retain_initrd [RAM] Keep initrd memory after extraction
1942 rhash_entries= [KNL,NET]
1943 Set number of hash buckets for route cache
1945 riscom8= [HW,SERIAL]
1946 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
1948 ro [KNL] Mount root device read-only on boot
1950 root= [KNL] Root filesystem
1952 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
1953 mount the root filesystem
1955 rootflags= [KNL] Set root filesystem mount option string
1957 rootfstype= [KNL] Set root filesystem type
1959 rootwait [KNL] Wait (indefinitely) for root device to show up.
1960 Useful for devices that are detected asynchronously
1961 (e.g. USB and MMC devices).
1963 root_plug.vendor_id=
1964 [ROOTPLUG] Override the default vendor ID
1966 root_plug.product_id=
1967 [ROOTPLUG] Override the default product ID
1969 root_plug.debug=
1970 [ROOTPLUG] Enable debugging output
1972 rw [KNL] Mount root device read-write on boot
1974 S [KNL] Run init in single mode
1976 sa1100ir [NET]
1977 See drivers/net/irda/sa1100_ir.c.
1979 sbni= [NET] Granch SBNI12 leased line adapter
1981 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
1982 Format: <io>[,<timeout>[,<isapnp>]]
1984 scsi_debug_*= [SCSI]
1985 See drivers/scsi/scsi_debug.c.
1987 scsi_default_dev_flags=
1988 [SCSI] SCSI default device flags
1989 Format: <integer>
1991 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
1992 Format: <vendor>:<model>:<flags>
1993 (flags are integer value)
1995 scsi_logging_level= [SCSI] a bit mask of logging levels
1996 See drivers/scsi/scsi_logging.h for bits. Also
1997 settable via sysctl at dev.scsi.logging_level
1998 (/proc/sys/dev/scsi/logging_level).
1999 There is also a nice 'scsi_logging_level' script in the
2000 S390-tools package, available for download at
2001 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2003 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2004 discovered. async scans them in kernel threads,
2005 allowing boot to proceed. none ignores them, expecting
2006 user space to do the scan.
2008 selinux [SELINUX] Disable or enable SELinux at boot time.
2009 Format: { "0" | "1" }
2010 See security/selinux/Kconfig help text.
2011 0 -- disable.
2012 1 -- enable.
2013 Default value is set via kernel config option.
2014 If enabled at boot time, /selinux/disable can be used
2015 later to disable prior to initial policy load.
2017 selinux_compat_net =
2018 [SELINUX] Set initial selinux_compat_net flag value.
2019 Format: { "0" | "1" }
2020 0 -- use new secmark-based packet controls
2021 1 -- use legacy packet controls
2022 Default value is 0 (preferred).
2023 Value can be changed at runtime via
2024 /selinux/compat_net.
2026 serialnumber [BUGS=X86-32]
2028 shapers= [NET]
2029 Maximal number of shapers.
2031 show_msr= [x86] show boot-time MSR settings
2032 Format: { <integer> }
2033 Show boot-time (BIOS-initialized) MSR settings.
2034 The parameter means the number of CPUs to show,
2035 for example 1 means boot CPU only.
2037 sim710= [SCSI,HW]
2038 See header of drivers/scsi/sim710.c.
2040 simeth= [IA-64]
2041 simscsi=
2043 slram= [HW,MTD]
2045 slub_debug[=options[,slabs]] [MM, SLUB]
2046 Enabling slub_debug allows one to determine the
2047 culprit if slab objects become corrupted. Enabling
2048 slub_debug can create guard zones around objects and
2049 may poison objects when not in use. Also tracks the
2050 last alloc / free. For more information see
2051 Documentation/vm/slub.txt.
2053 slub_max_order= [MM, SLUB]
2054 Determines the maximum allowed order for slabs.
2055 A high setting may cause OOMs due to memory
2056 fragmentation. For more information see
2057 Documentation/vm/slub.txt.
2059 slub_min_objects= [MM, SLUB]
2060 The minimum number of objects per slab. SLUB will
2061 increase the slab order up to slub_max_order to
2062 generate a sufficiently large slab able to contain
2063 the number of objects indicated. The higher the number
2064 of objects the smaller the overhead of tracking slabs
2065 and the less frequently locks need to be acquired.
2066 For more information see Documentation/vm/slub.txt.
2068 slub_min_order= [MM, SLUB]
2069 Determines the mininum page order for slabs. Must be
2070 lower than slub_max_order.
2071 For more information see Documentation/vm/slub.txt.
2073 slub_nomerge [MM, SLUB]
2074 Disable merging of slabs with similar size. May be
2075 necessary if there is some reason to distinguish
2076 allocs to different slabs. Debug options disable
2077 merging on their own.
2078 For more information see Documentation/vm/slub.txt.
2080 smart2= [HW]
2081 Format: <io1>[,<io2>[,...,<io8>]]
2083 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2084 attempt to substitute SMP alternatives once at boot.
2086 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2087 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2088 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2089 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2090 smsc-ircc2.ircc_irq= [HW] IRQ line
2091 smsc-ircc2.ircc_dma= [HW] DMA channel
2092 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2093 0: Toshiba Satellite 1800 (GP data pin select)
2094 1: Fast pin select (default)
2095 2: ATC IRMode
2097 snd-ad1816a= [HW,ALSA]
2099 snd-ad1848= [HW,ALSA]
2101 snd-ali5451= [HW,ALSA]
2103 snd-als100= [HW,ALSA]
2105 snd-als4000= [HW,ALSA]
2107 snd-azt2320= [HW,ALSA]
2109 snd-cmi8330= [HW,ALSA]
2111 snd-cmipci= [HW,ALSA]
2113 snd-cs4231= [HW,ALSA]
2115 snd-cs4232= [HW,ALSA]
2117 snd-cs4236= [HW,ALSA]
2119 snd-cs4281= [HW,ALSA]
2121 snd-cs46xx= [HW,ALSA]
2123 snd-dt019x= [HW,ALSA]
2125 snd-dummy= [HW,ALSA]
2127 snd-emu10k1= [HW,ALSA]
2129 snd-ens1370= [HW,ALSA]
2131 snd-ens1371= [HW,ALSA]
2133 snd-es968= [HW,ALSA]
2135 snd-es1688= [HW,ALSA]
2137 snd-es18xx= [HW,ALSA]
2139 snd-es1938= [HW,ALSA]
2141 snd-es1968= [HW,ALSA]
2143 snd-fm801= [HW,ALSA]
2145 snd-gusclassic= [HW,ALSA]
2147 snd-gusextreme= [HW,ALSA]
2149 snd-gusmax= [HW,ALSA]
2151 snd-hdsp= [HW,ALSA]
2153 snd-ice1712= [HW,ALSA]
2155 snd-intel8x0= [HW,ALSA]
2157 snd-interwave= [HW,ALSA]
2159 snd-interwave-stb=
2160 [HW,ALSA]
2162 snd-korg1212= [HW,ALSA]
2164 snd-maestro3= [HW,ALSA]
2166 snd-mpu401= [HW,ALSA]
2168 snd-mtpav= [HW,ALSA]
2170 snd-nm256= [HW,ALSA]
2172 snd-opl3sa2= [HW,ALSA]
2174 snd-opti92x-ad1848=
2175 [HW,ALSA]
2177 snd-opti92x-cs4231=
2178 [HW,ALSA]
2180 snd-opti93x= [HW,ALSA]
2182 snd-pmac= [HW,ALSA]
2184 snd-rme32= [HW,ALSA]
2186 snd-rme96= [HW,ALSA]
2188 snd-rme9652= [HW,ALSA]
2190 snd-sb8= [HW,ALSA]
2192 snd-sb16= [HW,ALSA]
2194 snd-sbawe= [HW,ALSA]
2196 snd-serial= [HW,ALSA]
2198 snd-sgalaxy= [HW,ALSA]
2200 snd-sonicvibes= [HW,ALSA]
2202 snd-sun-amd7930=
2203 [HW,ALSA]
2205 snd-sun-cs4231= [HW,ALSA]
2207 snd-trident= [HW,ALSA]
2209 snd-usb-audio= [HW,ALSA,USB]
2211 snd-via82xx= [HW,ALSA]
2213 snd-virmidi= [HW,ALSA]
2215 snd-wavefront= [HW,ALSA]
2217 snd-ymfpci= [HW,ALSA]
2219 softlockup_panic=
2220 [KNL] Should the soft-lockup detector generate panics.
2222 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2223 See Documentation/sonypi.txt
2225 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2226 See Documentation/serial/specialix.txt.
2228 spia_io_base= [HW,MTD]
2229 spia_fio_base=
2230 spia_pedr=
2231 spia_peddr=
2233 sscape= [HW,OSS]
2234 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2236 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2237 See Documentation/scsi/st.txt.
2239 stacktrace [FTRACE]
2240 Enabled the stack tracer on boot up.
2242 sti= [PARISC,HW]
2243 Format: <num>
2244 Set the STI (builtin display/keyboard on the HP-PARISC
2245 machines) console (graphic card) which should be used
2246 as the initial boot-console.
2247 See also comment in drivers/video/console/sticore.c.
2249 sti_font= [HW]
2250 See comment in drivers/video/console/sticore.c.
2252 stifb= [HW]
2253 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2255 sunrpc.pool_mode=
2256 [NFS]
2257 Control how the NFS server code allocates CPUs to
2258 service thread pools. Depending on how many NICs
2259 you have and where their interrupts are bound, this
2260 option will affect which CPUs will do NFS serving.
2261 Note: this parameter cannot be changed while the
2262 NFS server is running.
2264 auto the server chooses an appropriate mode
2265 automatically using heuristics
2266 global a single global pool contains all CPUs
2267 percpu one pool for each CPU
2268 pernode one pool for each NUMA node (equivalent
2269 to global on non-NUMA machines)
2271 swiotlb= [IA-64] Number of I/O TLB slabs
2273 switches= [HW,M68k]
2275 sym53c416= [HW,SCSI]
2276 See header of drivers/scsi/sym53c416.c.
2278 sysrq_always_enabled
2279 [KNL]
2280 Ignore sysrq setting - this boot parameter will
2281 neutralize any effect of /proc/sys/kernel/sysrq.
2282 Useful for debugging.
2284 t128= [HW,SCSI]
2285 See header of drivers/scsi/t128.c.
2287 tdfx= [HW,DRM]
2289 test_suspend= [SUSPEND]
2290 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2291 standby suspend) as the system sleep state to briefly
2292 enter during system startup. The system is woken from
2293 this state using a wakeup-capable RTC alarm.
2295 thash_entries= [KNL,NET]
2296 Set number of hash buckets for TCP connection
2298 thermal.act= [HW,ACPI]
2299 -1: disable all active trip points in all thermal zones
2300 <degrees C>: override all lowest active trip points
2302 thermal.crt= [HW,ACPI]
2303 -1: disable all critical trip points in all thermal zones
2304 <degrees C>: override all critical trip points
2306 thermal.nocrt= [HW,ACPI]
2307 Set to disable actions on ACPI thermal zone
2308 critical and hot trip points.
2310 thermal.off= [HW,ACPI]
2311 1: disable ACPI thermal control
2313 thermal.psv= [HW,ACPI]
2314 -1: disable all passive trip points
2315 <degrees C>: override all passive trip points to this
2316 value
2318 thermal.tzp= [HW,ACPI]
2319 Specify global default ACPI thermal zone polling rate
2320 <deci-seconds>: poll all this frequency
2321 0: no polling (default)
2323 tmscsim= [HW,SCSI]
2324 See comment before function dc390_setup() in
2325 drivers/scsi/tmscsim.c.
2327 topology= [S390]
2328 Format: {off | on}
2329 Specify if the kernel should make use of the cpu
2330 topology informations if the hardware supports these.
2331 The scheduler will make use of these informations and
2332 e.g. base its process migration decisions on it.
2333 Default is off.
2335 tp720= [HW,PS2]
2337 trix= [HW,OSS] MediaTrix AudioTrix Pro
2338 Format:
2339 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2341 tsc= Disable clocksource-must-verify flag for TSC.
2342 Format: <string>
2343 [x86] reliable: mark tsc clocksource as reliable, this
2344 disables clocksource verification at runtime.
2345 Used to enable high-resolution timer mode on older
2346 hardware, and in virtualized environment.
2348 turbografx.map[2|3]= [HW,JOY]
2349 TurboGraFX parallel port interface
2350 Format:
2351 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2352 See also Documentation/input/joystick-parport.txt
2354 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2355 See header of drivers/scsi/u14-34f.c.
2357 uart401= [HW,OSS]
2358 Format: <io>,<irq>
2360 uart6850= [HW,OSS]
2361 Format: <io>,<irq>
2363 uhci-hcd.ignore_oc=
2364 [USB] Ignore overcurrent events (default N).
2365 Some badly-designed motherboards generate lots of
2366 bogus events, for ports that aren't wired to
2367 anything. Set this parameter to avoid log spamming.
2368 Note that genuine overcurrent events won't be
2369 reported either.
2371 unknown_nmi_panic
2372 [X86-32,X86-64]
2373 Set unknown_nmi_panic=1 early on boot.
2375 usbcore.autosuspend=
2376 [USB] The autosuspend time delay (in seconds) used
2377 for newly-detected USB devices (default 2). This
2378 is the time required before an idle device will be
2379 autosuspended. Devices for which the delay is set
2380 to a negative value won't be autosuspended at all.
2382 usbcore.usbfs_snoop=
2383 [USB] Set to log all usbfs traffic (default 0 = off).
2385 usbcore.blinkenlights=
2386 [USB] Set to cycle leds on hubs (default 0 = off).
2388 usbcore.old_scheme_first=
2389 [USB] Start with the old device initialization
2390 scheme (default 0 = off).
2392 usbcore.use_both_schemes=
2393 [USB] Try the other device initialization scheme
2394 if the first one fails (default 1 = enabled).
2396 usbcore.initial_descriptor_timeout=
2397 [USB] Specifies timeout for the initial 64-byte
2398 USB_REQ_GET_DESCRIPTOR request in milliseconds
2399 (default 5000 = 5.0 seconds).
2401 usbhid.mousepoll=
2402 [USBHID] The interval which mice are to be polled at.
2404 usb-storage.delay_use=
2405 [UMS] The delay in seconds before a new device is
2406 scanned for Logical Units (default 5).
2408 usb-storage.quirks=
2409 [UMS] A list of quirks entries to supplement or
2410 override the built-in unusual_devs list. List
2411 entries are separated by commas. Each entry has
2412 the form VID:PID:Flags where VID and PID are Vendor
2413 and Product ID values (4-digit hex numbers) and
2414 Flags is a set of characters, each corresponding
2415 to a common usb-storage quirk flag as follows:
2416 a = SANE_SENSE (collect more than 18 bytes
2417 of sense data);
2418 c = FIX_CAPACITY (decrease the reported
2419 device capacity by one sector);
2420 h = CAPACITY_HEURISTICS (decrease the
2421 reported device capacity by one
2422 sector if the number is odd);
2423 i = IGNORE_DEVICE (don't bind to this
2424 device);
2425 l = NOT_LOCKABLE (don't try to lock and
2426 unlock ejectable media);
2427 m = MAX_SECTORS_64 (don't transfer more
2428 than 64 sectors = 32 KB at a time);
2429 o = CAPACITY_OK (accept the capacity
2430 reported by the device);
2431 r = IGNORE_RESIDUE (the device reports
2432 bogus residue values);
2433 s = SINGLE_LUN (the device has only one
2434 Logical Unit);
2435 w = NO_WP_DETECT (don't test whether the
2436 medium is write-protected).
2437 Example: quirks=0419:aaf5:rl,0421:0433:rc
2439 add_efi_memmap [EFI; x86-32,X86-64] Include EFI memory map in
2440 kernel's map of available physical RAM.
2442 vdso= [X86-32,SH,x86-64]
2443 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2444 vdso=1: enable VDSO (default)
2445 vdso=0: disable VDSO mapping
2447 vdso32= [X86-32,X86-64]
2448 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2449 vdso32=1: enable 32-bit VDSO (default)
2450 vdso32=0: disable 32-bit VDSO mapping
2452 vector= [IA-64,SMP]
2453 vector=percpu: enable percpu vector domain
2455 video= [FB] Frame buffer configuration
2456 See Documentation/fb/modedb.txt.
2458 vga= [BOOT,X86-32] Select a particular video mode
2459 See Documentation/x86/boot.txt and
2460 Documentation/svga.txt.
2461 Use vga=ask for menu.
2462 This is actually a boot loader parameter; the value is
2463 passed to the kernel using a special protocol.
2465 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2466 size of <nn>. This can be used to increase the
2467 minimum size (128MB on x86). It can also be used to
2468 decrease the size and leave more room for directly
2469 mapped kernel RAM.
2471 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2472 Format: <command>
2474 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2475 Format: <command>
2477 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2478 Format: <command>
2480 waveartist= [HW,OSS]
2481 Format: <io>,<irq>,<dma>,<dma2>
2483 wd33c93= [HW,SCSI]
2484 See header of drivers/scsi/wd33c93.c.
2486 wd7000= [HW,SCSI]
2487 See header of drivers/scsi/wd7000.c.
2489 wdt= [WDT] Watchdog
2490 See Documentation/watchdog/wdt.txt.
2492 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2493 xd_geo= See header of drivers/block/xd.c.
2495 xirc2ps_cs= [NET,PCMCIA]
2496 Format:
2497 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2499 norandmaps Don't use address space randomization. Equivalent to
2500 echo 0 > /proc/sys/kernel/randomize_va_space
2502 ______________________________________________________________________
2504 TODO:
2506 Add documentation for ALSA options.
2507 Add more DRM drivers.