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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 IMA Integrity measurement architecture is enabled.
48 IOSCHED More than one I/O scheduler is enabled.
49 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
50 ISAPNP ISA PnP code is enabled.
51 ISDN Appropriate ISDN support is enabled.
52 JOY Appropriate joystick support is enabled.
53 KMEMTRACE kmemtrace is enabled.
54 LIBATA Libata driver is enabled
55 LP Printer support is enabled.
56 LOOP Loopback device support is enabled.
57 M68k M68k architecture is enabled.
58 These options have more detailed description inside of
59 Documentation/m68k/kernel-options.txt.
60 MCA MCA bus support is enabled.
61 MDA MDA console support is enabled.
62 MOUSE Appropriate mouse support is enabled.
63 MSI Message Signaled Interrupts (PCI).
64 MTD MTD (Memory Technology Device) support is enabled.
65 NET Appropriate network support is enabled.
66 NUMA NUMA support is enabled.
67 GENERIC_TIME The generic timeofday code is enabled.
68 NFS Appropriate NFS support is enabled.
69 OSS OSS sound support is enabled.
70 PV_OPS A paravirtualized kernel is enabled.
71 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
72 PARISC The PA-RISC architecture is enabled.
73 PCI PCI bus support is enabled.
74 PCIE PCI Express support is enabled.
75 PCMCIA The PCMCIA subsystem is enabled.
76 PNP Plug & Play support is enabled.
77 PPC PowerPC architecture is enabled.
78 PPT Parallel port support is enabled.
79 PS2 Appropriate PS/2 support is enabled.
80 RAM RAM disk support is enabled.
81 ROOTPLUG The example Root Plug LSM is enabled.
82 S390 S390 architecture is enabled.
83 SCSI Appropriate SCSI support is enabled.
84 A lot of drivers has their options described inside of
85 Documentation/scsi/.
86 SECURITY Different security models are enabled.
87 SELINUX SELinux support is enabled.
88 SERIAL Serial support is enabled.
89 SH SuperH architecture is enabled.
90 SMP The kernel is an SMP kernel.
91 SPARC Sparc architecture is enabled.
92 SWSUSP Software suspend (hibernation) is enabled.
93 SUSPEND System suspend states are enabled.
94 FTRACE Function tracing enabled.
95 TS Appropriate touchscreen support is enabled.
96 UMS USB Mass Storage support is enabled.
97 USB USB support is enabled.
98 USBHID USB Human Interface Device support is enabled.
99 V4L Video For Linux support is enabled.
100 VGA The VGA console has been enabled.
101 VT Virtual terminal support is enabled.
102 WDT Watchdog support is enabled.
103 XT IBM PC/XT MFM hard disk support is enabled.
104 X86-32 X86-32, aka i386 architecture is enabled.
105 X86-64 X86-64 architecture is enabled.
106 More X86-64 boot options can be found in
107 Documentation/x86/x86_64/boot-options.txt .
108 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
110 In addition, the following text indicates that the option:
112 BUGS= Relates to possible processor bugs on the said processor.
113 KNL Is a kernel start-up parameter.
114 BOOT Is a boot loader parameter.
116 Parameters denoted with BOOT are actually interpreted by the boot
117 loader, and have no meaning to the kernel directly.
118 Do not modify the syntax of boot loader parameters without extreme
119 need or coordination with <Documentation/x86/boot.txt>.
121 There are also arch-specific kernel-parameters not documented here.
122 See for example <Documentation/x86/x86_64/boot-options.txt>.
124 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
125 a trailing = on the name of any parameter states that that parameter will
126 be entered as an environment variable, whereas its absence indicates that
127 it will appear as a kernel argument readable via /proc/cmdline by programs
128 running once the system is up.
130 The number of kernel parameters is not limited, but the length of the
131 complete command line (parameters including spaces etc.) is limited to
132 a fixed number of characters. This limit depends on the architecture
133 and is between 256 and 4096 characters. It is defined in the file
134 ./include/asm/setup.h as COMMAND_LINE_SIZE.
137 acpi= [HW,ACPI,X86]
138 Advanced Configuration and Power Interface
139 Format: { force | off | ht | strict | noirq | rsdt }
140 force -- enable ACPI if default was off
141 off -- disable ACPI if default was on
142 noirq -- do not use ACPI for IRQ routing
143 ht -- run only enough ACPI to enable Hyper Threading
144 strict -- Be less tolerant of platforms that are not
145 strictly ACPI specification compliant.
146 rsdt -- prefer RSDT over (default) XSDT
148 See also Documentation/power/pm.txt, pci=noacpi
150 acpi_apic_instance= [ACPI, IOAPIC]
151 Format: <int>
152 2: use 2nd APIC table, if available
153 1,0: use 1st APIC table
154 default: 0
156 acpi_backlight= [HW,ACPI]
157 acpi_backlight=vendor
158 acpi_backlight=video
159 If set to vendor, prefer vendor specific driver
160 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
161 of the ACPI video.ko driver.
163 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
164 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
165 Format: <int>
166 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
167 debug output. Bits in debug_layer correspond to a
168 _COMPONENT in an ACPI source file, e.g.,
169 #define _COMPONENT ACPI_PCI_COMPONENT
170 Bits in debug_level correspond to a level in
171 ACPI_DEBUG_PRINT statements, e.g.,
172 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
173 The debug_level mask defaults to "info". See
174 Documentation/acpi/debug.txt for more information about
175 debug layers and levels.
177 Enable processor driver info messages:
178 acpi.debug_layer=0x20000000
179 Enable PCI/PCI interrupt routing info messages:
180 acpi.debug_layer=0x400000
181 Enable AML "Debug" output, i.e., stores to the Debug
182 object while interpreting AML:
183 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
184 Enable all messages related to ACPI hardware:
185 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
187 Some values produce so much output that the system is
188 unusable. The "log_buf_len" parameter may be useful
189 if you need to capture more output.
191 acpi_display_output= [HW,ACPI]
192 acpi_display_output=vendor
193 acpi_display_output=video
194 See above.
196 acpi_irq_balance [HW,ACPI]
197 ACPI will balance active IRQs
198 default in APIC mode
200 acpi_irq_nobalance [HW,ACPI]
201 ACPI will not move active IRQs (default)
202 default in PIC mode
204 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
205 Format: <irq>,<irq>...
207 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
208 use by PCI
209 Format: <irq>,<irq>...
211 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
213 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
214 Format: To spoof as Windows 98: ="Microsoft Windows"
216 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
217 acpi_osi="string1" # add string1 -- only one string
218 acpi_osi="!string2" # remove built-in string2
219 acpi_osi= # disable all strings
221 acpi_pm_good [X86]
222 Override the pmtimer bug detection: force the kernel
223 to assume that this machine's pmtimer latches its value
224 and always returns good values.
226 acpi.power_nocheck= [HW,ACPI]
227 Format: 1/0 enable/disable the check of power state.
228 On some bogus BIOS the _PSC object/_STA object of
229 power resource can't return the correct device power
230 state. In such case it is unneccessary to check its
231 power state again in power transition.
232 1 : disable the power state check
234 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
235 Format: { level | edge | high | low }
237 acpi_serialize [HW,ACPI] force serialization of AML methods
239 acpi_skip_timer_override [HW,ACPI]
240 Recognize and ignore IRQ0/pin2 Interrupt Override.
241 For broken nForce2 BIOS resulting in XT-PIC timer.
243 acpi_sleep= [HW,ACPI] Sleep options
244 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
245 old_ordering, s4_nonvs }
246 See Documentation/power/video.txt for information on
247 s3_bios and s3_mode.
248 s3_beep is for debugging; it makes the PC's speaker beep
249 as soon as the kernel's real-mode entry point is called.
250 s4_nohwsig prevents ACPI hardware signature from being
251 used during resume from hibernation.
252 old_ordering causes the ACPI 1.0 ordering of the _PTS
253 control method, with respect to putting devices into
254 low power states, to be enforced (the ACPI 2.0 ordering
255 of _PTS is used by default).
256 s4_nonvs prevents the kernel from saving/restoring the
257 ACPI NVS memory during hibernation.
259 acpi_use_timer_override [HW,ACPI]
260 Use timer override. For some broken Nvidia NF5 boards
261 that require a timer override, but don't have HPET
263 acpi_enforce_resources= [ACPI]
264 { strict | lax | no }
265 Check for resource conflicts between native drivers
266 and ACPI OperationRegions (SystemIO and SystemMemory
267 only). IO ports and memory declared in ACPI might be
268 used by the ACPI subsystem in arbitrary AML code and
269 can interfere with legacy drivers.
270 strict (default): access to resources claimed by ACPI
271 is denied; legacy drivers trying to access reserved
272 resources will fail to bind to device using them.
273 lax: access to resources claimed by ACPI is allowed;
274 legacy drivers trying to access reserved resources
275 will bind successfully but a warning message is logged.
276 no: ACPI OperationRegions are not marked as reserved,
277 no further checks are performed.
279 ad1848= [HW,OSS]
280 Format: <io>,<irq>,<dma>,<dma2>,<type>
282 add_efi_memmap [EFI; X86] Include EFI memory map in
283 kernel's map of available physical RAM.
285 advansys= [HW,SCSI]
286 See header of drivers/scsi/advansys.c.
288 advwdt= [HW,WDT] Advantech WDT
289 Format: <iostart>,<iostop>
291 aedsp16= [HW,OSS] Audio Excel DSP 16
292 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
293 See also header of sound/oss/aedsp16.c.
295 agp= [AGP]
296 { off | try_unsupported }
297 off: disable AGP support
298 try_unsupported: try to drive unsupported chipsets
299 (may crash computer or cause data corruption)
301 aha152x= [HW,SCSI]
302 See Documentation/scsi/aha152x.txt.
304 aha1542= [HW,SCSI]
305 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
307 aic7xxx= [HW,SCSI]
308 See Documentation/scsi/aic7xxx.txt.
310 aic79xx= [HW,SCSI]
311 See Documentation/scsi/aic79xx.txt.
313 amd_iommu= [HW,X86-84]
314 Pass parameters to the AMD IOMMU driver in the system.
315 Possible values are:
316 isolate - enable device isolation (each device, as far
317 as possible, will get its own protection
318 domain) [default]
319 share - put every device behind one IOMMU into the
320 same protection domain
321 fullflush - enable flushing of IO/TLB entries when
322 they are unmapped. Otherwise they are
323 flushed before they will be reused, which
324 is a lot of faster
326 amd_iommu_size= [HW,X86-64]
327 Define the size of the aperture for the AMD IOMMU
328 driver. Possible values are:
329 '32M', '64M' (default), '128M', '256M', '512M', '1G'
331 amijoy.map= [HW,JOY] Amiga joystick support
332 Map of devices attached to JOY0DAT and JOY1DAT
333 Format: <a>,<b>
334 See also Documentation/kernel/input/joystick.txt
336 analog.map= [HW,JOY] Analog joystick and gamepad support
337 Specifies type or capabilities of an analog joystick
338 connected to one of 16 gameports
339 Format: <type1>,<type2>,..<type16>
341 apc= [HW,SPARC]
342 Power management functions (SPARCstation-4/5 + deriv.)
343 Format: noidle
344 Disable APC CPU standby support. SPARCstation-Fox does
345 not play well with APC CPU idle - disable it if you have
346 APC and your system crashes randomly.
348 apic= [APIC,i386] Advanced Programmable Interrupt Controller
349 Change the output verbosity whilst booting
350 Format: { quiet (default) | verbose | debug }
351 Change the amount of debugging information output
352 when initialising the APIC and IO-APIC components.
354 apm= [APM] Advanced Power Management
355 See header of arch/x86/kernel/apm_32.c.
357 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
358 Format: <io>,<irq>,<nodeID>
360 ataflop= [HW,M68k]
362 atarimouse= [HW,MOUSE] Atari Mouse
364 atascsi= [HW,SCSI] Atari SCSI
366 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
367 EzKey and similar keyboards
369 atkbd.reset= [HW] Reset keyboard during initialization
371 atkbd.set= [HW] Select keyboard code set
372 Format: <int> (2 = AT (default), 3 = PS/2)
374 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
375 keyboards
377 atkbd.softraw= [HW] Choose between synthetic and real raw mode
378 Format: <bool> (0 = real, 1 = synthetic (default))
380 atkbd.softrepeat= [HW]
381 Use software keyboard repeat
383 autotest [IA64]
385 baycom_epp= [HW,AX25]
386 Format: <io>,<mode>
388 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
389 Format: <io>,<mode>
390 See header of drivers/net/hamradio/baycom_par.c.
392 baycom_ser_fdx= [HW,AX25]
393 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
394 Format: <io>,<irq>,<mode>[,<baud>]
395 See header of drivers/net/hamradio/baycom_ser_fdx.c.
397 baycom_ser_hdx= [HW,AX25]
398 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
399 Format: <io>,<irq>,<mode>
400 See header of drivers/net/hamradio/baycom_ser_hdx.c.
402 boot_delay= Milliseconds to delay each printk during boot.
403 Values larger than 10 seconds (10000) are changed to
404 no delay (0).
405 Format: integer
407 bootmem_debug [KNL] Enable bootmem allocator debug messages.
409 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
410 bttv.radio= Most important insmod options are available as
411 kernel args too.
412 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
413 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
415 BusLogic= [HW,SCSI]
416 See drivers/scsi/BusLogic.c, comment before function
417 BusLogic_ParseDriverOptions().
419 c101= [NET] Moxa C101 synchronous serial card
421 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
422 Sometimes CPU hardware bugs make them report the cache
423 size incorrectly. The kernel will attempt work arounds
424 to fix known problems, but for some CPUs it is not
425 possible to determine what the correct size should be.
426 This option provides an override for these situations.
428 capability.disable=
429 [SECURITY] Disable capabilities. This would normally
430 be used only if an alternative security model is to be
431 configured. Potentially dangerous and should only be
432 used if you are entirely sure of the consequences.
434 ccw_timeout_log [S390]
435 See Documentation/s390/CommonIO for details.
437 cgroup_disable= [KNL] Disable a particular controller
438 Format: {name of the controller(s) to disable}
439 {Currently supported controllers - "memory"}
441 checkreqprot [SELINUX] Set initial checkreqprot flag value.
442 Format: { "0" | "1" }
443 See security/selinux/Kconfig help text.
444 0 -- check protection applied by kernel (includes
445 any implied execute protection).
446 1 -- check protection requested by application.
447 Default value is set via a kernel config option.
448 Value can be changed at runtime via
449 /selinux/checkreqprot.
451 cio_ignore= [S390]
452 See Documentation/s390/CommonIO for details.
454 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
455 [Deprecated]
456 Forces specified clocksource (if available) to be used
457 when calculating gettimeofday(). If specified
458 clocksource is not available, it defaults to PIT.
459 Format: { pit | tsc | cyclone | pmtmr }
461 clocksource= [GENERIC_TIME] Override the default clocksource
462 Format: <string>
463 Override the default clocksource and use the clocksource
464 with the name specified.
465 Some clocksource names to choose from, depending on
466 the platform:
467 [all] jiffies (this is the base, fallback clocksource)
468 [ACPI] acpi_pm
469 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
470 pxa_timer,timer3,32k_counter,timer0_1
471 [AVR32] avr32
472 [X86-32] pit,hpet,tsc,vmi-timer;
473 scx200_hrt on Geode; cyclone on IBM x440
474 [MIPS] MIPS
475 [PARISC] cr16
476 [S390] tod
477 [SH] SuperH
478 [SPARC64] tick
479 [X86-64] hpet,tsc
481 clearcpuid=BITNUM [X86]
482 Disable CPUID feature X for the kernel. See
483 arch/x86/include/asm/cpufeature.h for the valid bit
484 numbers. Note the Linux specific bits are not necessarily
485 stable over kernel options, but the vendor specific
486 ones should be.
487 Also note that user programs calling CPUID directly
488 or using the feature without checking anything
489 will still see it. This just prevents it from
490 being used by the kernel or shown in /proc/cpuinfo.
491 Also note the kernel might malfunction if you disable
492 some critical bits.
494 code_bytes [X86] How many bytes of object code to print
495 in an oops report.
496 Range: 0 - 8192
497 Default: 64
499 com20020= [HW,NET] ARCnet - COM20020 chipset
500 Format:
501 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
503 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
504 Format: <io>[,<irq>]
506 com90xx= [HW,NET]
507 ARCnet - COM90xx chipset (memory-mapped buffers)
508 Format: <io>[,<irq>[,<memstart>]]
510 condev= [HW,S390] console device
511 conmode=
513 console= [KNL] Output console device and options.
515 tty<n> Use the virtual console device <n>.
517 ttyS<n>[,options]
518 ttyUSB0[,options]
519 Use the specified serial port. The options are of
520 the form "bbbbpnf", where "bbbb" is the baud rate,
521 "p" is parity ("n", "o", or "e"), "n" is number of
522 bits, and "f" is flow control ("r" for RTS or
523 omit it). Default is "9600n8".
525 See Documentation/serial-console.txt for more
526 information. See
527 Documentation/networking/netconsole.txt for an
528 alternative.
530 uart[8250],io,<addr>[,options]
531 uart[8250],mmio,<addr>[,options]
532 Start an early, polled-mode console on the 8250/16550
533 UART at the specified I/O port or MMIO address,
534 switching to the matching ttyS device later. The
535 options are the same as for ttyS, above.
537 If the device connected to the port is not a TTY but a braille
538 device, prepend "brl," before the device type, for instance
539 console=brl,ttyS0
540 For now, only VisioBraille is supported.
542 coredump_filter=
543 [KNL] Change the default value for
544 /proc/<pid>/coredump_filter.
545 See also Documentation/filesystems/proc.txt.
547 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
548 Format:
549 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
551 crashkernel=nn[KMG]@ss[KMG]
552 [KNL] Reserve a chunk of physical memory to
553 hold a kernel to switch to with kexec on panic.
555 crashkernel=range1:size1[,range2:size2,...][@offset]
556 [KNL] Same as above, but depends on the memory
557 in the running system. The syntax of range is
558 start-[end] where start and end are both
559 a memory unit (amount[KMG]). See also
560 Documentation/kdump/kdump.txt for a example.
562 cs89x0_dma= [HW,NET]
563 Format: <dma>
565 cs89x0_media= [HW,NET]
566 Format: { rj45 | aui | bnc }
568 dasd= [HW,NET]
569 See header of drivers/s390/block/dasd_devmap.c.
571 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
572 (one device per port)
573 Format: <port#>,<type>
574 See also Documentation/input/joystick-parport.txt
576 debug [KNL] Enable kernel debugging (events log level).
578 debug_locks_verbose=
579 [KNL] verbose self-tests
580 Format=<0|1>
581 Print debugging info while doing the locking API
582 self-tests.
583 We default to 0 (no extra messages), setting it to
584 1 will print _a lot_ more information - normally
585 only useful to kernel developers.
587 debug_objects [KNL] Enable object debugging
589 no_debug_objects
590 [KNL] Disable object debugging
592 debugpat [X86] Enable PAT debugging
594 decnet.addr= [HW,NET]
595 Format: <area>[,<node>]
596 See also Documentation/networking/decnet.txt.
598 default_hugepagesz=
599 [same as hugepagesz=] The size of the default
600 HugeTLB page size. This is the size represented by
601 the legacy /proc/ hugepages APIs, used for SHM, and
602 default size when mounting hugetlbfs filesystems.
603 Defaults to the default architecture's huge page size
604 if not specified.
606 dhash_entries= [KNL]
607 Set number of hash buckets for dentry cache.
609 digi= [HW,SERIAL]
610 IO parameters + enable/disable command.
612 digiepca= [HW,SERIAL]
613 See drivers/char/README.epca and
614 Documentation/serial/digiepca.txt.
616 disable_mtrr_cleanup [X86]
617 The kernel tries to adjust MTRR layout from continuous
618 to discrete, to make X server driver able to add WB
619 entry later. This parameter disables that.
621 disable_mtrr_trim [X86, Intel and AMD only]
622 By default the kernel will trim any uncacheable
623 memory out of your available memory pool based on
624 MTRR settings. This parameter disables that behavior,
625 possibly causing your machine to run very slowly.
627 disable_timer_pin_1 [X86]
628 Disable PIN 1 of APIC timer
629 Can be useful to work around chipset bugs.
631 dmasound= [HW,OSS] Sound subsystem buffers
633 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
634 this option disables the debugging code at boot.
636 dma_debug_entries=<number>
637 This option allows to tune the number of preallocated
638 entries for DMA-API debugging code. One entry is
639 required per DMA-API allocation. Use this if the
640 DMA-API debugging code disables itself because the
641 architectural default is too low.
643 dscc4.setup= [NET]
645 dtc3181e= [HW,SCSI]
647 dynamic_printk Enables pr_debug()/dev_dbg() calls if
648 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
649 These can also be switched on/off via
650 <debugfs>/dynamic_printk/modules
652 earlycon= [KNL] Output early console device and options.
653 uart[8250],io,<addr>[,options]
654 uart[8250],mmio,<addr>[,options]
655 Start an early, polled-mode console on the 8250/16550
656 UART at the specified I/O port or MMIO address.
657 The options are the same as for ttyS, above.
659 earlyprintk= [X86,SH,BLACKFIN]
660 earlyprintk=vga
661 earlyprintk=serial[,ttySn[,baudrate]]
662 earlyprintk=dbgp
664 Append ",keep" to not disable it when the real console
665 takes over.
667 Only vga or serial or usb debug port at a time.
669 Currently only ttyS0 and ttyS1 are supported.
671 Interaction with the standard serial driver is not
672 very good.
674 The VGA output is eventually overwritten by the real
675 console.
677 eata= [HW,SCSI]
679 edd= [EDD]
680 Format: {"off" | "on" | "skip[mbr]"}
682 eisa_irq_edge= [PARISC,HW]
683 See header of drivers/parisc/eisa.c.
685 elanfreq= [X86-32]
686 See comment before function elanfreq_setup() in
687 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
689 elevator= [IOSCHED]
690 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
691 See Documentation/block/as-iosched.txt and
692 Documentation/block/deadline-iosched.txt for details.
694 elfcorehdr= [IA64,PPC,SH,X86]
695 Specifies physical address of start of kernel core
696 image elf header. Generally kexec loader will
697 pass this option to capture kernel.
698 See Documentation/kdump/kdump.txt for details.
700 enable_mtrr_cleanup [X86]
701 The kernel tries to adjust MTRR layout from continuous
702 to discrete, to make X server driver able to add WB
703 entry later. This parameter enables that.
705 enable_timer_pin_1 [i386,x86-64]
706 Enable PIN 1 of APIC timer
707 Can be useful to work around chipset bugs
708 (in particular on some ATI chipsets).
709 The kernel tries to set a reasonable default.
711 enforcing [SELINUX] Set initial enforcing status.
712 Format: {"0" | "1"}
713 See security/selinux/Kconfig help text.
714 0 -- permissive (log only, no denials).
715 1 -- enforcing (deny and log).
716 Default value is 0.
717 Value can be changed at runtime via /selinux/enforce.
719 ether= [HW,NET] Ethernet cards parameters
720 This option is obsoleted by the "netdev=" option, which
721 has equivalent usage. See its documentation for details.
723 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
724 Format: <io>[,<irq>]
726 failslab=
727 fail_page_alloc=
728 fail_make_request=[KNL]
729 General fault injection mechanism.
730 Format: <interval>,<probability>,<space>,<times>
731 See also /Documentation/fault-injection/.
733 fd_mcs= [HW,SCSI]
734 See header of drivers/scsi/fd_mcs.c.
736 fdomain= [HW,SCSI]
737 See header of drivers/scsi/fdomain.c.
739 floppy= [HW]
740 See Documentation/blockdev/floppy.txt.
742 force_pal_cache_flush
743 [IA-64] Avoid check_sal_cache_flush which may hang on
744 buggy SAL_CACHE_FLUSH implementations. Using this
745 parameter will force ia64_sal_cache_flush to call
746 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
748 ftrace=[tracer]
749 [ftrace] will set and start the specified tracer
750 as early as possible in order to facilitate early
751 boot debugging.
753 ftrace_dump_on_oops
754 [ftrace] will dump the trace buffers on oops.
756 gamecon.map[2|3]=
757 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
758 support via parallel port (up to 5 devices per port)
759 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
760 See also Documentation/input/joystick-parport.txt
762 gamma= [HW,DRM]
764 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
765 Format: off | on
766 default: on
768 gdth= [HW,SCSI]
769 See header of drivers/scsi/gdth.c.
771 gpt [EFI] Forces disk with valid GPT signature but
772 invalid Protective MBR to be treated as GPT.
774 gvp11= [HW,SCSI]
776 hashdist= [KNL,NUMA] Large hashes allocated during boot
777 are distributed across NUMA nodes. Defaults on
778 for 64bit NUMA, off otherwise.
779 Format: 0 | 1 (for off | on)
781 hcl= [IA-64] SGI's Hardware Graph compatibility layer
783 hd= [EIDE] (E)IDE hard drive subsystem geometry
784 Format: <cyl>,<head>,<sect>
786 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
787 size of <nn>. This works even on boxes that have no
788 highmem otherwise. This also works to reduce highmem
789 size on bigger boxes.
791 highres= [KNL] Enable/disable high resolution timer mode.
792 Valid parameters: "on", "off"
793 Default: "on"
795 hisax= [HW,ISDN]
796 See Documentation/isdn/README.HiSax.
798 hlt [BUGS=ARM,SH]
800 hpet= [X86-32,HPET] option to control HPET usage
801 Format: { enable (default) | disable | force |
802 verbose }
803 disable: disable HPET and use PIT instead
804 force: allow force enabled of undocumented chips (ICH4,
805 VIA, nVidia)
806 verbose: show contents of HPET registers during setup
808 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
809 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
810 On x86-64 and powerpc, this option can be specified
811 multiple times interleaved with hugepages= to reserve
812 huge pages of different sizes. Valid pages sizes on
813 x86-64 are 2M (when the CPU supports "pse") and 1G
814 (when the CPU supports the "pdpe1gb" cpuinfo flag)
815 Note that 1GB pages can only be allocated at boot time
816 using hugepages= and not freed afterwards.
818 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
819 terminal devices. Valid values: 0..8
820 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
821 If specified, z/VM IUCV HVC accepts connections
822 from listed z/VM user IDs only.
824 i2c_bus= [HW] Override the default board specific I2C bus speed
825 or register an additional I2C bus that is not
826 registered from board initialization code.
827 Format:
828 <bus_id>,<clkrate>
830 i8042.debug [HW] Toggle i8042 debug mode
831 i8042.direct [HW] Put keyboard port into non-translated mode
832 i8042.dumbkbd [HW] Pretend that controller can only read data from
833 keyboard and cannot control its state
834 (Don't attempt to blink the leds)
835 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
836 i8042.nokbd [HW] Don't check/create keyboard port
837 i8042.noloop [HW] Disable the AUX Loopback command while probing
838 for the AUX port
839 i8042.nomux [HW] Don't check presence of an active multiplexing
840 controller
841 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
842 controllers
843 i8042.panicblink=
844 [HW] Frequency with which keyboard LEDs should blink
845 when kernel panics (default is 0.5 sec)
846 i8042.reset [HW] Reset the controller during init and cleanup
847 i8042.unlock [HW] Unlock (ignore) the keylock
849 i810= [HW,DRM]
851 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
852 indicates that the driver is running on unsupported
853 hardware.
854 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
855 does not match list of supported models.
856 i8k.power_status
857 [HW] Report power status in /proc/i8k
858 (disabled by default)
859 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
860 capability is set.
862 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
863 See Documentation/mca.txt.
865 icn= [HW,ISDN]
866 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
868 ide-core.nodma= [HW] (E)IDE subsystem
869 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
870 .vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom
871 .chs .ignore_cable are additional options
872 See Documentation/ide/ide.txt.
874 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
875 See Documentation/ide/ide.txt.
877 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
878 Claim all unknown PCI IDE storage controllers.
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 ignore_loglevel [KNL]
896 Ignore loglevel setting - this will print /all/
897 kernel messages to the console. Useful for debugging.
899 ihash_entries= [KNL]
900 Set number of hash buckets for inode cache.
902 ima_audit= [IMA]
903 Format: { "0" | "1" }
904 0 -- integrity auditing messages. (Default)
905 1 -- enable informational integrity auditing messages.
907 ima_hash= [IMA]
908 Formt: { "sha1" | "md5" }
909 default: "sha1"
911 in2000= [HW,SCSI]
912 See header of drivers/scsi/in2000.c.
914 init= [KNL]
915 Format: <full_path>
916 Run specified binary instead of /sbin/init as init
917 process.
919 initcall_debug [KNL] Trace initcalls as they are executed. Useful
920 for working out where the kernel is dying during
921 startup.
923 initrd= [BOOT] Specify the location of the initial ramdisk
925 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
926 Format: <irq>
928 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
929 on
930 Enable intel iommu driver.
931 off
932 Disable intel iommu driver.
933 igfx_off [Default Off]
934 By default, gfx is mapped as normal device. If a gfx
935 device has a dedicated DMAR unit, the DMAR unit is
936 bypassed by not enabling DMAR with this option. In
937 this case, gfx device will use physical address for
938 DMA.
939 forcedac [x86_64]
940 With this option iommu will not optimize to look
941 for io virtual address below 32 bit forcing dual
942 address cycle on pci bus for cards supporting greater
943 than 32 bit addressing. The default is to look
944 for translation below 32 bit and if not available
945 then look in the higher range.
946 strict [Default Off]
947 With this option on every unmap_single operation will
948 result in a hardware IOTLB flush operation as opposed
949 to batching them for performance.
951 inttest= [IA64]
953 iomem= Disable strict checking of access to MMIO memory
954 strict regions from userspace.
955 relaxed
957 iommu= [x86]
958 off
959 force
960 noforce
961 biomerge
962 panic
963 nopanic
964 merge
965 nomerge
966 forcesac
967 soft
969 io7= [HW] IO7 for Marvel based alpha systems
970 See comment before marvel_specify_io7 in
971 arch/alpha/kernel/core_marvel.c.
973 io_delay= [X86] I/O delay method
974 0x80
975 Standard port 0x80 based delay
976 0xed
977 Alternate port 0xed based delay (needed on some systems)
978 udelay
979 Simple two microseconds delay
980 none
981 No delay
983 ip= [IP_PNP]
984 See Documentation/filesystems/nfsroot.txt.
986 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
987 See comment before ip2_setup() in
988 drivers/char/ip2/ip2base.c.
990 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
991 See header of drivers/scsi/ips.c.
993 irqfixup [HW]
994 When an interrupt is not handled search all handlers
995 for it. Intended to get systems with badly broken
996 firmware running.
998 irqpoll [HW]
999 When an interrupt is not handled search all handlers
1000 for it. Also check all handlers each timer
1001 interrupt. Intended to get systems with badly broken
1002 firmware running.
1004 isapnp= [ISAPNP]
1005 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1007 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1008 Format:
1009 <cpu number>,...,<cpu number>
1010 or
1011 <cpu number>-<cpu number>
1012 (must be a positive range in ascending order)
1013 or a mixture
1014 <cpu number>,...,<cpu number>-<cpu number>
1016 This option can be used to specify one or more CPUs
1017 to isolate from the general SMP balancing and scheduling
1018 algorithms. You can move a process onto or off an
1019 "isolated" CPU via the CPU affinity syscalls or cpuset.
1020 <cpu number> begins at 0 and the maximum value is
1021 "number of CPUs in system - 1".
1023 This option is the preferred way to isolate CPUs. The
1024 alternative -- manually setting the CPU mask of all
1025 tasks in the system -- can cause problems and
1026 suboptimal load balancer performance.
1028 iucv= [HW,NET]
1030 js= [HW,JOY] Analog joystick
1031 See Documentation/input/joystick.txt.
1033 keepinitrd [HW,ARM]
1035 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1036 specifies the amount of memory usable by the kernel
1037 for non-movable allocations. The requested amount is
1038 spread evenly throughout all nodes in the system. The
1039 remaining memory in each node is used for Movable
1040 pages. In the event, a node is too small to have both
1041 kernelcore and Movable pages, kernelcore pages will
1042 take priority and other nodes will have a larger number
1043 of kernelcore pages. The Movable zone is used for the
1044 allocation of pages that may be reclaimed or moved
1045 by the page migration subsystem. This means that
1046 HugeTLB pages may not be allocated from this zone.
1047 Note that allocations like PTEs-from-HighMem still
1048 use the HighMem zone if it exists, and the Normal
1049 zone if it does not.
1051 kmemtrace.enable= [KNL,KMEMTRACE] Format: { yes | no }
1052 Controls whether kmemtrace is enabled
1053 at boot-time.
1055 kmemtrace.subbufs=n [KNL,KMEMTRACE] Overrides the number of
1056 subbufs kmemtrace's relay channel has. Set this
1057 higher than default (KMEMTRACE_N_SUBBUFS in code) if
1058 you experience buffer overruns.
1060 kgdboc= [HW] kgdb over consoles.
1061 Requires a tty driver that supports console polling.
1062 (only serial suported for now)
1063 Format: <serial_device>[,baud]
1065 kmac= [MIPS] korina ethernet MAC address.
1066 Configure the RouterBoard 532 series on-chip
1067 Ethernet adapter MAC address.
1069 kstack=N [X86] Print N words from the kernel stack
1070 in oops dumps.
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,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_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1218 than or equal to this physical address is ignored.
1220 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1221 should make use of. maxcpus=n : n >= 0 limits the
1222 kernel to using 'n' processors. n=0 is a special case,
1223 it is equivalent to "nosmp", which also disables
1224 the IO APIC.
1226 max_loop= [LOOP] Maximum number of loopback devices that can
1227 be mounted
1228 Format: <1-256>
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] 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 default : 0 <disable>
1312 Specifies the number of memtest passes to be
1313 performed. Each pass selects another test
1314 pattern from a given set of patterns. Memtest
1315 fills the memory with this pattern, validates
1316 memory contents and reserves bad memory
1317 regions that are detected.
1319 meye.*= [HW] Set MotionEye Camera parameters
1320 See Documentation/video4linux/meye.txt.
1322 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1323 Multi-Function General Purpose Timers on AMD Geode
1324 platforms.
1326 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1327 the BIOS has incorrectly applied a workaround. TinyBIOS
1328 version 0.98 is known to be affected, 0.99 fixes the
1329 problem by letting the user disable the workaround.
1331 mga= [HW,DRM]
1333 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1334 physical address is ignored.
1336 mminit_loglevel=
1337 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1338 parameter allows control of the logging verbosity for
1339 the additional memory initialisation checks. A value
1340 of 0 disables mminit logging and a level of 4 will
1341 log everything. Information is printed at KERN_DEBUG
1342 so loglevel=8 may also need to be specified.
1344 mousedev.tap_time=
1345 [MOUSE] Maximum time between finger touching and
1346 leaving touchpad surface for touch to be considered
1347 a tap and be reported as a left button click (for
1348 touchpads working in absolute mode only).
1349 Format: <msecs>
1350 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1351 reporting absolute coordinates, such as tablets
1352 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1353 reporting absolute coordinates, such as tablets
1355 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1356 is similar to kernelcore except it specifies the
1357 amount of memory used for migratable allocations.
1358 If both kernelcore and movablecore is specified,
1359 then kernelcore will be at *least* the specified
1360 value but may be more. If movablecore on its own
1361 is specified, the administrator must be careful
1362 that the amount of memory usable for all allocations
1363 is not too small.
1365 mpu401= [HW,OSS]
1366 Format: <io>,<irq>
1368 MTD_Partition= [MTD]
1369 Format: <name>,<region-number>,<size>,<offset>
1371 MTD_Region= [MTD] Format:
1372 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1374 mtdparts= [MTD]
1375 See drivers/mtd/cmdlinepart.c.
1377 mtdset= [ARM]
1378 ARM/S3C2412 JIVE boot control
1380 See arch/arm/mach-s3c2412/mach-jive.c
1382 mtouchusb.raw_coordinates=
1383 [HW] Make the MicroTouch USB driver use raw coordinates
1384 ('y', default) or cooked coordinates ('n')
1386 mtrr_chunk_size=nn[KMG] [X86]
1387 used for mtrr cleanup. It is largest continous chunk
1388 that could hold holes aka. UC entries.
1390 mtrr_gran_size=nn[KMG] [X86]
1391 Used for mtrr cleanup. It is granularity of mtrr block.
1392 Default is 1.
1393 Large value could prevent small alignment from
1394 using up MTRRs.
1396 mtrr_spare_reg_nr=n [X86]
1397 Format: <integer>
1398 Range: 0,7 : spare reg number
1399 Default : 1
1400 Used for mtrr cleanup. It is spare mtrr entries number.
1401 Set to 2 or more if your graphical card needs more.
1403 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1405 NCR_D700= [HW,SCSI]
1406 See header of drivers/scsi/NCR_D700.c.
1408 ncr5380= [HW,SCSI]
1410 ncr53c400= [HW,SCSI]
1412 ncr53c400a= [HW,SCSI]
1414 ncr53c406a= [HW,SCSI]
1416 ncr53c8xx= [HW,SCSI]
1418 netdev= [NET] Network devices parameters
1419 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1420 Note that mem_start is often overloaded to mean
1421 something different and driver-specific.
1422 This usage is only documented in each driver source
1423 file if at all.
1425 nf_conntrack.acct=
1426 [NETFILTER] Enable connection tracking flow accounting
1427 0 to disable accounting
1428 1 to enable accounting
1429 Default value depends on CONFIG_NF_CT_ACCT that is
1430 going to be removed in 2.6.29.
1432 nfsaddrs= [NFS]
1433 See Documentation/filesystems/nfsroot.txt.
1435 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1436 See Documentation/filesystems/nfsroot.txt.
1438 nfs.callback_tcpport=
1439 [NFS] set the TCP port on which the NFSv4 callback
1440 channel should listen.
1442 nfs.idmap_cache_timeout=
1443 [NFS] set the maximum lifetime for idmapper cache
1444 entries.
1446 nfs.enable_ino64=
1447 [NFS] enable 64-bit inode numbers.
1448 If zero, the NFS client will fake up a 32-bit inode
1449 number for the readdir() and stat() syscalls instead
1450 of returning the full 64-bit number.
1451 The default is to return 64-bit inode numbers.
1453 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1454 when a NMI is triggered.
1455 Format: [state][,regs][,debounce][,die]
1457 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1458 Format: [panic,][num]
1459 Valid num: 0,1,2
1460 0 - turn nmi_watchdog off
1461 1 - use the IO-APIC timer for the NMI watchdog
1462 2 - use the local APIC for the NMI watchdog using
1463 a performance counter. Note: This will use one
1464 performance counter and the local APIC's performance
1465 vector.
1466 When panic is specified, panic when an NMI watchdog
1467 timeout occurs.
1468 This is useful when you use a panic=... timeout and
1469 need the box quickly up again.
1470 Instead of 1 and 2 it is possible to use the following
1471 symbolic names: lapic and ioapic
1472 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1474 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1475 emulation library even if a 387 maths coprocessor
1476 is present.
1478 no_console_suspend
1479 [HW] Never suspend the console
1480 Disable suspending of consoles during suspend and
1481 hibernate operations. Once disabled, debugging
1482 messages can reach various consoles while the rest
1483 of the system is being put to sleep (ie, while
1484 debugging driver suspend/resume hooks). This may
1485 not work reliably with all consoles, but is known
1486 to work with serial and VGA consoles.
1488 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1489 caches in the slab allocator. Saves per-node memory,
1490 but will impact performance.
1492 noalign [KNL,ARM]
1494 noapic [SMP,APIC] Tells the kernel to not make use of any
1495 IOAPICs that may be present in the system.
1497 nobats [PPC] Do not use BATs for mapping kernel lowmem
1498 on "Classic" PPC cores.
1500 nocache [ARM]
1502 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1504 nodelayacct [KNL] Disable per-task delay accounting
1506 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1508 nodsp [SH] Disable hardware DSP at boot time.
1510 noefi [X86] Disable EFI runtime services support.
1512 noexec [IA-64]
1514 noexec [X86]
1515 On X86-32 available only on PAE configured kernels.
1516 noexec=on: enable non-executable mappings (default)
1517 noexec=off: disable non-executable mappings
1519 noexec32 [X86-64]
1520 This affects only 32-bit executables.
1521 noexec32=on: enable non-executable mappings (default)
1522 read doesn't imply executable mappings
1523 noexec32=off: disable non-executable mappings
1524 read implies executable mappings
1526 nofpu [SH] Disable hardware FPU at boot time.
1528 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1529 register save and restore. The kernel will only save
1530 legacy floating-point registers on task switch.
1532 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1533 wfi(ARM) instruction doesn't work correctly and not to
1534 use it. This is also useful when using JTAG debugger.
1536 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1537 instruction doesn't work correctly and not to
1538 use it.
1540 no_file_caps Tells the kernel not to honor file capabilities. The
1541 only way then for a file to be executed with privilege
1542 is to be setuid root or executed by root.
1544 nohalt [IA-64] Tells the kernel not to use the power saving
1545 function PAL_HALT_LIGHT when idle. This increases
1546 power-consumption. On the positive side, it reduces
1547 interrupt wake-up latency, which may improve performance
1548 in certain environments such as networked servers or
1549 real-time systems.
1551 nohz= [KNL] Boottime enable/disable dynamic ticks
1552 Valid arguments: on, off
1553 Default: on
1555 noiotrap [SH] Disables trapped I/O port accesses.
1557 noirqdebug [X86-32] Disables the code which attempts to detect and
1558 disable unhandled interrupt sources.
1560 no_timer_check [X86,APIC] Disables the code which tests for
1561 broken timer IRQ sources.
1563 noisapnp [ISAPNP] Disables ISA PnP code.
1565 noinitrd [RAM] Tells the kernel not to load any configured
1566 initial RAM disk.
1568 nointroute [IA-64]
1570 nojitter [IA64] Disables jitter checking for ITC timers.
1572 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1574 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1576 noltlbs [PPC] Do not use large page/tlb entries for kernel
1577 lowmem mapping on PPC40x.
1579 nomca [IA-64] Disable machine check abort handling
1581 nomce [X86-32] Machine Check Exception
1583 nomfgpt [X86-32] Disable Multi-Function General Purpose
1584 Timer usage (for AMD Geode machines).
1586 norandmaps Don't use address space randomization. Equivalent to
1587 echo 0 > /proc/sys/kernel/randomize_va_space
1589 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1591 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1592 with UP alternatives
1594 noresidual [PPC] Don't use residual data on PReP machines.
1596 noresume [SWSUSP] Disables resume and restores original swap
1597 space.
1599 no-scroll [VGA] Disables scrollback.
1600 This is required for the Braillex ib80-piezo Braille
1601 reader made by F.H. Papenmeier (Germany).
1603 nosbagart [IA-64]
1605 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1607 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1608 and disable the IO APIC. legacy for "maxcpus=0".
1610 nosoftlockup [KNL] Disable the soft-lockup detector.
1612 noswapaccount [KNL] Disable accounting of swap in memory resource
1613 controller. (See Documentation/cgroups/memory.txt)
1615 nosync [HW,M68K] Disables sync negotiation for all devices.
1617 notsc [BUGS=X86-32] Disable Time Stamp Counter
1619 nousb [USB] Disable the USB subsystem
1621 nowb [ARM]
1623 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1625 nptcg= [IA64] Override max number of concurrent global TLB
1626 purges which is reported from either PAL_VM_SUMMARY or
1627 SAL PALO.
1629 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1631 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1632 one of ['zone', 'node', 'default'] can be specified
1633 This can be set from sysctl after boot.
1634 See Documentation/sysctl/vm.txt for details.
1636 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1637 See Documentation/debugging-via-ohci1394.txt for more
1638 info.
1640 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1641 Rather than timing out after 20 ms if an EC
1642 command is not properly ACKed, override the length
1643 of the timeout. We have interrupts disabled while
1644 waiting for the ACK, so if this is set too high
1645 interrupts *may* be lost!
1647 opl3= [HW,OSS]
1648 Format: <io>
1650 oprofile.timer= [HW]
1651 Use timer interrupt instead of performance counters
1653 osst= [HW,SCSI] SCSI Tape Driver
1654 Format: <buffer_size>,<write_threshold>
1655 See also Documentation/scsi/st.txt.
1657 panic= [KNL] Kernel behaviour on panic
1658 Format: <timeout>
1660 parkbd.port= [HW] Parallel port number the keyboard adapter is
1661 connected to, default is 0.
1662 Format: <parport#>
1663 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1664 0 for XT, 1 for AT (default is AT).
1665 Format: <mode>
1667 parport= [HW,PPT] Specify parallel ports. 0 disables.
1668 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1669 Use 'auto' to force the driver to use any
1670 IRQ/DMA settings detected (the default is to
1671 ignore detected IRQ/DMA settings because of
1672 possible conflicts). You can specify the base
1673 address, IRQ, and DMA settings; IRQ and DMA
1674 should be numbers, or 'auto' (for using detected
1675 settings on that particular port), or 'nofifo'
1676 (to avoid using a FIFO even if it is detected).
1677 Parallel ports are assigned in the order they
1678 are specified on the command line, starting
1679 with parport0.
1681 parport_init_mode= [HW,PPT]
1682 Configure VIA parallel port to operate in
1683 a specific mode. This is necessary on Pegasos
1684 computer where firmware has no options for setting
1685 up parallel port mode and sets it to spp.
1686 Currently this function knows 686a and 8231 chips.
1687 Format: [spp|ps2|epp|ecp|ecpepp]
1689 pas2= [HW,OSS] Format:
1690 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1692 pas16= [HW,SCSI]
1693 See header of drivers/scsi/pas16.c.
1695 pause_on_oops=
1696 Halt all CPUs after the first oops has been printed for
1697 the specified number of seconds. This is to be used if
1698 your oopses keep scrolling off the screen.
1700 pcbit= [HW,ISDN]
1702 pcd. [PARIDE]
1703 See header of drivers/block/paride/pcd.c.
1704 See also Documentation/blockdev/paride.txt.
1706 pci=option[,option...] [PCI] various PCI subsystem options:
1707 earlydump [X86] dump PCI config space before the kernel
1708 changes anything
1709 off [X86] don't probe for the PCI bus
1710 bios [X86-32] force use of PCI BIOS, don't access
1711 the hardware directly. Use this if your machine
1712 has a non-standard PCI host bridge.
1713 nobios [X86-32] disallow use of PCI BIOS, only direct
1714 hardware access methods are allowed. Use this
1715 if you experience crashes upon bootup and you
1716 suspect they are caused by the BIOS.
1717 conf1 [X86] Force use of PCI Configuration
1718 Mechanism 1.
1719 conf2 [X86] Force use of PCI Configuration
1720 Mechanism 2.
1721 noaer [PCIE] If the PCIEAER kernel config parameter is
1722 enabled, this kernel boot option can be used to
1723 disable the use of PCIE advanced error reporting.
1724 nodomains [PCI] Disable support for multiple PCI
1725 root domains (aka PCI segments, in ACPI-speak).
1726 nommconf [X86] Disable use of MMCONFIG for PCI
1727 Configuration
1728 nomsi [MSI] If the PCI_MSI kernel config parameter is
1729 enabled, this kernel boot option can be used to
1730 disable the use of MSI interrupts system-wide.
1731 noioapicquirk [APIC] Disable all boot interrupt quirks.
1732 Safety option to keep boot IRQs enabled. This
1733 should never be necessary.
1734 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1735 primary IO-APIC for bridges that cannot disable
1736 boot IRQs. This fixes a source of spurious IRQs
1737 when the system masks IRQs.
1738 noioapicreroute [APIC] Disable workaround that uses the
1739 boot IRQ equivalent of an IRQ that connects to
1740 a chipset where boot IRQs cannot be disabled.
1741 The opposite of ioapicreroute.
1742 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1743 routing table. These calls are known to be buggy
1744 on several machines and they hang the machine
1745 when used, but on other computers it's the only
1746 way to get the interrupt routing table. Try
1747 this option if the kernel is unable to allocate
1748 IRQs or discover secondary PCI buses on your
1749 motherboard.
1750 rom [X86] Assign address space to expansion ROMs.
1751 Use with caution as certain devices share
1752 address decoders between ROMs and other
1753 resources.
1754 norom [X86] Do not assign address space to
1755 expansion ROMs that do not already have
1756 BIOS assigned address ranges.
1757 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1758 assigned automatically to PCI devices. You can
1759 make the kernel exclude IRQs of your ISA cards
1760 this way.
1761 pirqaddr=0xAAAAA [X86] Specify the physical address
1762 of the PIRQ table (normally generated
1763 by the BIOS) if it is outside the
1764 F0000h-100000h range.
1765 lastbus=N [X86] Scan all buses thru bus #N. Can be
1766 useful if the kernel is unable to find your
1767 secondary buses and you want to tell it
1768 explicitly which ones they are.
1769 assign-busses [X86] Always assign all PCI bus
1770 numbers ourselves, overriding
1771 whatever the firmware may have done.
1772 usepirqmask [X86] Honor the possible IRQ mask stored
1773 in the BIOS $PIR table. This is needed on
1774 some systems with broken BIOSes, notably
1775 some HP Pavilion N5400 and Omnibook XE3
1776 notebooks. This will have no effect if ACPI
1777 IRQ routing is enabled.
1778 noacpi [X86] Do not use ACPI for IRQ routing
1779 or for PCI scanning.
1780 use_crs [X86] Use _CRS for PCI resource
1781 allocation.
1782 routeirq Do IRQ routing for all PCI devices.
1783 This is normally done in pci_enable_device(),
1784 so this option is a temporary workaround
1785 for broken drivers that don't call it.
1786 skip_isa_align [X86] do not align io start addr, so can
1787 handle more pci cards
1788 firmware [ARM] Do not re-enumerate the bus but instead
1789 just use the configuration from the
1790 bootloader. This is currently used on
1791 IXP2000 systems where the bus has to be
1792 configured a certain way for adjunct CPUs.
1793 noearly [X86] Don't do any early type 1 scanning.
1794 This might help on some broken boards which
1795 machine check when some devices' config space
1796 is read. But various workarounds are disabled
1797 and some IOMMU drivers will not work.
1798 bfsort Sort PCI devices into breadth-first order.
1799 This sorting is done to get a device
1800 order compatible with older (<= 2.4) kernels.
1801 nobfsort Don't sort PCI devices into breadth-first order.
1802 cbiosize=nn[KMG] The fixed amount of bus space which is
1803 reserved for the CardBus bridge's IO window.
1804 The default value is 256 bytes.
1805 cbmemsize=nn[KMG] The fixed amount of bus space which is
1806 reserved for the CardBus bridge's memory
1807 window. The default value is 64 megabytes.
1808 resource_alignment=
1809 Format:
1810 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1811 Specifies alignment and device to reassign
1812 aligned memory resources.
1813 If <order of align> is not specified,
1814 PAGE_SIZE is used as alignment.
1815 PCI-PCI bridge can be specified, if resource
1816 windows need to be expanded.
1818 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1819 Management.
1820 off Disable ASPM.
1821 force Enable ASPM even on devices that claim not to support it.
1822 WARNING: Forcing ASPM on may cause system lockups.
1824 pcmv= [HW,PCMCIA] BadgePAD 4
1826 pd. [PARIDE]
1827 See Documentation/blockdev/paride.txt.
1829 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1830 boot time.
1831 Format: { 0 | 1 }
1832 See arch/parisc/kernel/pdc_chassis.c
1834 pf. [PARIDE]
1835 See Documentation/blockdev/paride.txt.
1837 pg. [PARIDE]
1838 See Documentation/blockdev/paride.txt.
1840 pirq= [SMP,APIC] Manual mp-table setup
1841 See Documentation/x86/i386/IO-APIC.txt.
1843 plip= [PPT,NET] Parallel port network link
1844 Format: { parport<nr> | timid | 0 }
1845 See also Documentation/parport.txt.
1847 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1848 Override pmtimer IOPort with a hex value.
1849 e.g. pmtmr=0x508
1851 pnp.debug [PNP]
1852 Enable PNP debug messages. This depends on the
1853 CONFIG_PNP_DEBUG_MESSAGES option.
1855 pnpacpi= [ACPI]
1856 { off }
1858 pnpbios= [ISAPNP]
1859 { on | off | curr | res | no-curr | no-res }
1861 pnp_reserve_irq=
1862 [ISAPNP] Exclude IRQs for the autoconfiguration
1864 pnp_reserve_dma=
1865 [ISAPNP] Exclude DMAs for the autoconfiguration
1867 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1868 Ranges are in pairs (I/O port base and size).
1870 pnp_reserve_mem=
1871 [ISAPNP] Exclude memory regions for the
1872 autoconfiguration.
1873 Ranges are in pairs (memory base and size).
1875 ports= [IP_VS_FTP] IPVS ftp helper module
1876 Default is 21.
1877 Up to 8 (IP_VS_APP_MAX_PORTS) ports
1878 may be specified.
1879 Format: <port>,<port>....
1881 print-fatal-signals=
1882 [KNL] debug: print fatal signals
1883 print-fatal-signals=1: print segfault info to
1884 the kernel console.
1885 default: off.
1887 printk.time= Show timing data prefixed to each printk message line
1888 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1890 processor.max_cstate= [HW,ACPI]
1891 Limit processor to maximum C-state
1892 max_cstate=9 overrides any DMI blacklist limit.
1894 processor.nocst [HW,ACPI]
1895 Ignore the _CST method to determine C-states,
1896 instead using the legacy FADT method
1898 profile= [KNL] Enable kernel profiling via /proc/profile
1899 Format: [schedule,]<number>
1900 Param: "schedule" - profile schedule points.
1901 Param: <number> - step/bucket size as a power of 2 for
1902 statistical time based profiling.
1903 Param: "sleep" - profile D-state sleeping (millisecs).
1904 Requires CONFIG_SCHEDSTATS
1905 Param: "kvm" - profile VM exits.
1907 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1908 before loading.
1909 See Documentation/blockdev/ramdisk.txt.
1911 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1912 probe for; one of (bare|imps|exps|lifebook|any).
1913 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1914 per second.
1915 psmouse.resetafter= [HW,MOUSE]
1916 Try to reset the device after so many bad packets
1917 (0 = never).
1918 psmouse.resolution=
1919 [HW,MOUSE] Set desired mouse resolution, in dpi.
1920 psmouse.smartscroll=
1921 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1922 0 = disabled, 1 = enabled (default).
1924 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1925 Format:
1926 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1928 pt. [PARIDE]
1929 See Documentation/blockdev/paride.txt.
1931 pty.legacy_count=
1932 [KNL] Number of legacy pty's. Overwrites compiled-in
1933 default number.
1935 quiet [KNL] Disable most log messages
1937 r128= [HW,DRM]
1939 raid= [HW,RAID]
1940 See Documentation/md.txt.
1942 ramdisk_blocksize= [RAM]
1943 See Documentation/blockdev/ramdisk.txt.
1945 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1946 See Documentation/blockdev/ramdisk.txt.
1948 rcupdate.blimit= [KNL,BOOT]
1949 Set maximum number of finished RCU callbacks to process
1950 in one batch.
1952 rcupdate.qhimark= [KNL,BOOT]
1953 Set threshold of queued
1954 RCU callbacks over which batch limiting is disabled.
1956 rcupdate.qlowmark= [KNL,BOOT]
1957 Set threshold of queued RCU callbacks below which
1958 batch limiting is re-enabled.
1960 rdinit= [KNL]
1961 Format: <full_path>
1962 Run specified binary instead of /init from the ramdisk,
1963 used for early userspace startup. See initrd.
1965 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1966 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1967 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1969 relax_domain_level=
1970 [KNL, SMP] Set scheduler's default relax_domain_level.
1971 See Documentation/cgroups/cpusets.txt.
1973 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1975 reservetop= [X86-32]
1976 Format: nn[KMG]
1977 Reserves a hole at the top of the kernel virtual
1978 address space.
1980 reset_devices [KNL] Force drivers to reset the underlying device
1981 during initialization.
1983 resume= [SWSUSP]
1984 Specify the partition device for software suspend
1986 resume_offset= [SWSUSP]
1987 Specify the offset from the beginning of the partition
1988 given by "resume=" at which the swap header is located,
1989 in <PAGE_SIZE> units (needed only for swap files).
1990 See Documentation/power/swsusp-and-swap-files.txt
1992 retain_initrd [RAM] Keep initrd memory after extraction
1994 rhash_entries= [KNL,NET]
1995 Set number of hash buckets for route cache
1997 riscom8= [HW,SERIAL]
1998 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2000 ro [KNL] Mount root device read-only on boot
2002 root= [KNL] Root filesystem
2004 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2005 mount the root filesystem
2007 rootflags= [KNL] Set root filesystem mount option string
2009 rootfstype= [KNL] Set root filesystem type
2011 rootwait [KNL] Wait (indefinitely) for root device to show up.
2012 Useful for devices that are detected asynchronously
2013 (e.g. USB and MMC devices).
2015 root_plug.vendor_id=
2016 [ROOTPLUG] Override the default vendor ID
2018 root_plug.product_id=
2019 [ROOTPLUG] Override the default product ID
2021 root_plug.debug=
2022 [ROOTPLUG] Enable debugging output
2024 rw [KNL] Mount root device read-write on boot
2026 S [KNL] Run init in single mode
2028 sa1100ir [NET]
2029 See drivers/net/irda/sa1100_ir.c.
2031 sbni= [NET] Granch SBNI12 leased line adapter
2033 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2034 Format: <io>[,<timeout>[,<isapnp>]]
2036 scsi_debug_*= [SCSI]
2037 See drivers/scsi/scsi_debug.c.
2039 scsi_default_dev_flags=
2040 [SCSI] SCSI default device flags
2041 Format: <integer>
2043 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2044 Format: <vendor>:<model>:<flags>
2045 (flags are integer value)
2047 scsi_logging_level= [SCSI] a bit mask of logging levels
2048 See drivers/scsi/scsi_logging.h for bits. Also
2049 settable via sysctl at dev.scsi.logging_level
2050 (/proc/sys/dev/scsi/logging_level).
2051 There is also a nice 'scsi_logging_level' script in the
2052 S390-tools package, available for download at
2053 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2055 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2056 discovered. async scans them in kernel threads,
2057 allowing boot to proceed. none ignores them, expecting
2058 user space to do the scan.
2060 security= [SECURITY] Choose a security module to enable at boot.
2061 If this boot parameter is not specified, only the first
2062 security module asking for security registration will be
2063 loaded. An invalid security module name will be treated
2064 as if no module has been chosen.
2066 selinux= [SELINUX] Disable or enable SELinux at boot time.
2067 Format: { "0" | "1" }
2068 See security/selinux/Kconfig help text.
2069 0 -- disable.
2070 1 -- enable.
2071 Default value is set via kernel config option.
2072 If enabled at boot time, /selinux/disable can be used
2073 later to disable prior to initial policy load.
2075 serialnumber [BUGS=X86-32]
2077 shapers= [NET]
2078 Maximal number of shapers.
2080 show_msr= [x86] show boot-time MSR settings
2081 Format: { <integer> }
2082 Show boot-time (BIOS-initialized) MSR settings.
2083 The parameter means the number of CPUs to show,
2084 for example 1 means boot CPU only.
2086 sim710= [SCSI,HW]
2087 See header of drivers/scsi/sim710.c.
2089 simeth= [IA-64]
2090 simscsi=
2092 slram= [HW,MTD]
2094 slub_debug[=options[,slabs]] [MM, SLUB]
2095 Enabling slub_debug allows one to determine the
2096 culprit if slab objects become corrupted. Enabling
2097 slub_debug can create guard zones around objects and
2098 may poison objects when not in use. Also tracks the
2099 last alloc / free. For more information see
2100 Documentation/vm/slub.txt.
2102 slub_max_order= [MM, SLUB]
2103 Determines the maximum allowed order for slabs.
2104 A high setting may cause OOMs due to memory
2105 fragmentation. For more information see
2106 Documentation/vm/slub.txt.
2108 slub_min_objects= [MM, SLUB]
2109 The minimum number of objects per slab. SLUB will
2110 increase the slab order up to slub_max_order to
2111 generate a sufficiently large slab able to contain
2112 the number of objects indicated. The higher the number
2113 of objects the smaller the overhead of tracking slabs
2114 and the less frequently locks need to be acquired.
2115 For more information see Documentation/vm/slub.txt.
2117 slub_min_order= [MM, SLUB]
2118 Determines the mininum page order for slabs. Must be
2119 lower than slub_max_order.
2120 For more information see Documentation/vm/slub.txt.
2122 slub_nomerge [MM, SLUB]
2123 Disable merging of slabs with similar size. May be
2124 necessary if there is some reason to distinguish
2125 allocs to different slabs. Debug options disable
2126 merging on their own.
2127 For more information see Documentation/vm/slub.txt.
2129 smart2= [HW]
2130 Format: <io1>[,<io2>[,...,<io8>]]
2132 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2133 attempt to substitute SMP alternatives once at boot.
2135 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2136 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2137 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2138 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2139 smsc-ircc2.ircc_irq= [HW] IRQ line
2140 smsc-ircc2.ircc_dma= [HW] DMA channel
2141 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2142 0: Toshiba Satellite 1800 (GP data pin select)
2143 1: Fast pin select (default)
2144 2: ATC IRMode
2146 snd-ad1816a= [HW,ALSA]
2148 snd-ad1848= [HW,ALSA]
2150 snd-ali5451= [HW,ALSA]
2152 snd-als100= [HW,ALSA]
2154 snd-als4000= [HW,ALSA]
2156 snd-azt2320= [HW,ALSA]
2158 snd-cmi8330= [HW,ALSA]
2160 snd-cmipci= [HW,ALSA]
2162 snd-cs4231= [HW,ALSA]
2164 snd-cs4232= [HW,ALSA]
2166 snd-cs4236= [HW,ALSA]
2168 snd-cs4281= [HW,ALSA]
2170 snd-cs46xx= [HW,ALSA]
2172 snd-dt019x= [HW,ALSA]
2174 snd-dummy= [HW,ALSA]
2176 snd-emu10k1= [HW,ALSA]
2178 snd-ens1370= [HW,ALSA]
2180 snd-ens1371= [HW,ALSA]
2182 snd-es968= [HW,ALSA]
2184 snd-es1688= [HW,ALSA]
2186 snd-es18xx= [HW,ALSA]
2188 snd-es1938= [HW,ALSA]
2190 snd-es1968= [HW,ALSA]
2192 snd-fm801= [HW,ALSA]
2194 snd-gusclassic= [HW,ALSA]
2196 snd-gusextreme= [HW,ALSA]
2198 snd-gusmax= [HW,ALSA]
2200 snd-hdsp= [HW,ALSA]
2202 snd-ice1712= [HW,ALSA]
2204 snd-intel8x0= [HW,ALSA]
2206 snd-interwave= [HW,ALSA]
2208 snd-interwave-stb=
2209 [HW,ALSA]
2211 snd-korg1212= [HW,ALSA]
2213 snd-maestro3= [HW,ALSA]
2215 snd-mpu401= [HW,ALSA]
2217 snd-mtpav= [HW,ALSA]
2219 snd-nm256= [HW,ALSA]
2221 snd-opl3sa2= [HW,ALSA]
2223 snd-opti92x-ad1848=
2224 [HW,ALSA]
2226 snd-opti92x-cs4231=
2227 [HW,ALSA]
2229 snd-opti93x= [HW,ALSA]
2231 snd-pmac= [HW,ALSA]
2233 snd-rme32= [HW,ALSA]
2235 snd-rme96= [HW,ALSA]
2237 snd-rme9652= [HW,ALSA]
2239 snd-sb8= [HW,ALSA]
2241 snd-sb16= [HW,ALSA]
2243 snd-sbawe= [HW,ALSA]
2245 snd-serial= [HW,ALSA]
2247 snd-sgalaxy= [HW,ALSA]
2249 snd-sonicvibes= [HW,ALSA]
2251 snd-sun-amd7930=
2252 [HW,ALSA]
2254 snd-sun-cs4231= [HW,ALSA]
2256 snd-trident= [HW,ALSA]
2258 snd-usb-audio= [HW,ALSA,USB]
2260 snd-via82xx= [HW,ALSA]
2262 snd-virmidi= [HW,ALSA]
2264 snd-wavefront= [HW,ALSA]
2266 snd-ymfpci= [HW,ALSA]
2268 softlockup_panic=
2269 [KNL] Should the soft-lockup detector generate panics.
2271 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2272 See Documentation/sonypi.txt
2274 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2275 See Documentation/serial/specialix.txt.
2277 spia_io_base= [HW,MTD]
2278 spia_fio_base=
2279 spia_pedr=
2280 spia_peddr=
2282 sscape= [HW,OSS]
2283 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2285 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2286 See Documentation/scsi/st.txt.
2288 stacktrace [FTRACE]
2289 Enabled the stack tracer on boot up.
2291 sti= [PARISC,HW]
2292 Format: <num>
2293 Set the STI (builtin display/keyboard on the HP-PARISC
2294 machines) console (graphic card) which should be used
2295 as the initial boot-console.
2296 See also comment in drivers/video/console/sticore.c.
2298 sti_font= [HW]
2299 See comment in drivers/video/console/sticore.c.
2301 stifb= [HW]
2302 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2304 sunrpc.pool_mode=
2305 [NFS]
2306 Control how the NFS server code allocates CPUs to
2307 service thread pools. Depending on how many NICs
2308 you have and where their interrupts are bound, this
2309 option will affect which CPUs will do NFS serving.
2310 Note: this parameter cannot be changed while the
2311 NFS server is running.
2313 auto the server chooses an appropriate mode
2314 automatically using heuristics
2315 global a single global pool contains all CPUs
2316 percpu one pool for each CPU
2317 pernode one pool for each NUMA node (equivalent
2318 to global on non-NUMA machines)
2320 swiotlb= [IA-64] Number of I/O TLB slabs
2322 switches= [HW,M68k]
2324 sym53c416= [HW,SCSI]
2325 See header of drivers/scsi/sym53c416.c.
2327 sysrq_always_enabled
2328 [KNL]
2329 Ignore sysrq setting - this boot parameter will
2330 neutralize any effect of /proc/sys/kernel/sysrq.
2331 Useful for debugging.
2333 t128= [HW,SCSI]
2334 See header of drivers/scsi/t128.c.
2336 tdfx= [HW,DRM]
2338 test_suspend= [SUSPEND]
2339 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2340 standby suspend) as the system sleep state to briefly
2341 enter during system startup. The system is woken from
2342 this state using a wakeup-capable RTC alarm.
2344 thash_entries= [KNL,NET]
2345 Set number of hash buckets for TCP connection
2347 thermal.act= [HW,ACPI]
2348 -1: disable all active trip points in all thermal zones
2349 <degrees C>: override all lowest active trip points
2351 thermal.crt= [HW,ACPI]
2352 -1: disable all critical trip points in all thermal zones
2353 <degrees C>: override all critical trip points
2355 thermal.nocrt= [HW,ACPI]
2356 Set to disable actions on ACPI thermal zone
2357 critical and hot trip points.
2359 thermal.off= [HW,ACPI]
2360 1: disable ACPI thermal control
2362 thermal.psv= [HW,ACPI]
2363 -1: disable all passive trip points
2364 <degrees C>: override all passive trip points to this
2365 value
2367 thermal.tzp= [HW,ACPI]
2368 Specify global default ACPI thermal zone polling rate
2369 <deci-seconds>: poll all this frequency
2370 0: no polling (default)
2372 tmscsim= [HW,SCSI]
2373 See comment before function dc390_setup() in
2374 drivers/scsi/tmscsim.c.
2376 topology= [S390]
2377 Format: {off | on}
2378 Specify if the kernel should make use of the cpu
2379 topology informations if the hardware supports these.
2380 The scheduler will make use of these informations and
2381 e.g. base its process migration decisions on it.
2382 Default is off.
2384 tp720= [HW,PS2]
2386 trace_buf_size=nn[KMG] [ftrace] will set tracing buffer size.
2388 trix= [HW,OSS] MediaTrix AudioTrix Pro
2389 Format:
2390 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2392 tsc= Disable clocksource-must-verify flag for TSC.
2393 Format: <string>
2394 [x86] reliable: mark tsc clocksource as reliable, this
2395 disables clocksource verification at runtime.
2396 Used to enable high-resolution timer mode on older
2397 hardware, and in virtualized environment.
2399 turbografx.map[2|3]= [HW,JOY]
2400 TurboGraFX parallel port interface
2401 Format:
2402 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2403 See also Documentation/input/joystick-parport.txt
2405 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2406 See header of drivers/scsi/u14-34f.c.
2408 uart401= [HW,OSS]
2409 Format: <io>,<irq>
2411 uart6850= [HW,OSS]
2412 Format: <io>,<irq>
2414 uhci-hcd.ignore_oc=
2415 [USB] Ignore overcurrent events (default N).
2416 Some badly-designed motherboards generate lots of
2417 bogus events, for ports that aren't wired to
2418 anything. Set this parameter to avoid log spamming.
2419 Note that genuine overcurrent events won't be
2420 reported either.
2422 unknown_nmi_panic
2423 [X86]
2424 Set unknown_nmi_panic=1 early on boot.
2426 usbcore.autosuspend=
2427 [USB] The autosuspend time delay (in seconds) used
2428 for newly-detected USB devices (default 2). This
2429 is the time required before an idle device will be
2430 autosuspended. Devices for which the delay is set
2431 to a negative value won't be autosuspended at all.
2433 usbcore.usbfs_snoop=
2434 [USB] Set to log all usbfs traffic (default 0 = off).
2436 usbcore.blinkenlights=
2437 [USB] Set to cycle leds on hubs (default 0 = off).
2439 usbcore.old_scheme_first=
2440 [USB] Start with the old device initialization
2441 scheme (default 0 = off).
2443 usbcore.use_both_schemes=
2444 [USB] Try the other device initialization scheme
2445 if the first one fails (default 1 = enabled).
2447 usbcore.initial_descriptor_timeout=
2448 [USB] Specifies timeout for the initial 64-byte
2449 USB_REQ_GET_DESCRIPTOR request in milliseconds
2450 (default 5000 = 5.0 seconds).
2452 usbhid.mousepoll=
2453 [USBHID] The interval which mice are to be polled at.
2455 usb-storage.delay_use=
2456 [UMS] The delay in seconds before a new device is
2457 scanned for Logical Units (default 5).
2459 usb-storage.quirks=
2460 [UMS] A list of quirks entries to supplement or
2461 override the built-in unusual_devs list. List
2462 entries are separated by commas. Each entry has
2463 the form VID:PID:Flags where VID and PID are Vendor
2464 and Product ID values (4-digit hex numbers) and
2465 Flags is a set of characters, each corresponding
2466 to a common usb-storage quirk flag as follows:
2467 a = SANE_SENSE (collect more than 18 bytes
2468 of sense data);
2469 c = FIX_CAPACITY (decrease the reported
2470 device capacity by one sector);
2471 h = CAPACITY_HEURISTICS (decrease the
2472 reported device capacity by one
2473 sector if the number is odd);
2474 i = IGNORE_DEVICE (don't bind to this
2475 device);
2476 l = NOT_LOCKABLE (don't try to lock and
2477 unlock ejectable media);
2478 m = MAX_SECTORS_64 (don't transfer more
2479 than 64 sectors = 32 KB at a time);
2480 o = CAPACITY_OK (accept the capacity
2481 reported by the device);
2482 r = IGNORE_RESIDUE (the device reports
2483 bogus residue values);
2484 s = SINGLE_LUN (the device has only one
2485 Logical Unit);
2486 w = NO_WP_DETECT (don't test whether the
2487 medium is write-protected).
2488 Example: quirks=0419:aaf5:rl,0421:0433:rc
2490 vdso= [X86,SH]
2491 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2492 vdso=1: enable VDSO (default)
2493 vdso=0: disable VDSO mapping
2495 vdso32= [X86]
2496 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2497 vdso32=1: enable 32-bit VDSO (default)
2498 vdso32=0: disable 32-bit VDSO mapping
2500 vector= [IA-64,SMP]
2501 vector=percpu: enable percpu vector domain
2503 video= [FB] Frame buffer configuration
2504 See Documentation/fb/modedb.txt.
2506 vga= [BOOT,X86-32] Select a particular video mode
2507 See Documentation/x86/boot.txt and
2508 Documentation/svga.txt.
2509 Use vga=ask for menu.
2510 This is actually a boot loader parameter; the value is
2511 passed to the kernel using a special protocol.
2513 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2514 size of <nn>. This can be used to increase the
2515 minimum size (128MB on x86). It can also be used to
2516 decrease the size and leave more room for directly
2517 mapped kernel RAM.
2519 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2520 Format: <command>
2522 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2523 Format: <command>
2525 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2526 Format: <command>
2528 vt.default_blu= [VT]
2529 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2530 Change the default blue palette of the console.
2531 This is a 16-member array composed of values
2532 ranging from 0-255.
2534 vt.default_grn= [VT]
2535 Format: <green0>,<green1>,<green2>,...,<green15>
2536 Change the default green palette of the console.
2537 This is a 16-member array composed of values
2538 ranging from 0-255.
2540 vt.default_red= [VT]
2541 Format: <red0>,<red1>,<red2>,...,<red15>
2542 Change the default red palette of the console.
2543 This is a 16-member array composed of values
2544 ranging from 0-255.
2546 vt.default_utf8=
2547 [VT]
2548 Format=<0|1>
2549 Set system-wide default UTF-8 mode for all tty's.
2550 Default is 1, i.e. UTF-8 mode is enabled for all
2551 newly opened terminals.
2553 waveartist= [HW,OSS]
2554 Format: <io>,<irq>,<dma>,<dma2>
2556 wd33c93= [HW,SCSI]
2557 See header of drivers/scsi/wd33c93.c.
2559 wd7000= [HW,SCSI]
2560 See header of drivers/scsi/wd7000.c.
2562 wdt= [WDT] Watchdog
2563 See Documentation/watchdog/wdt.txt.
2565 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2566 default x2apic cluster mode on platforms
2567 supporting x2apic.
2569 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2570 xd_geo= See header of drivers/block/xd.c.
2572 xirc2ps_cs= [NET,PCMCIA]
2573 Format:
2574 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2576 ______________________________________________________________________
2578 TODO:
2580 Add documentation for ALSA options.
2581 Add more DRM drivers.