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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 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 HW Appropriate hardware is enabled.
52 IA-64 IA-64 architecture is enabled.
53 IMA Integrity measurement architecture is enabled.
54 IOSCHED More than one I/O scheduler is enabled.
55 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
56 ISAPNP ISA PnP code is enabled.
57 ISDN Appropriate ISDN support is enabled.
58 JOY Appropriate joystick support is enabled.
59 KMEMTRACE kmemtrace is enabled.
60 LIBATA Libata driver is enabled
61 LP Printer support is enabled.
62 LOOP Loopback device support is enabled.
63 M68k M68k architecture is enabled.
64 These options have more detailed description inside of
65 Documentation/m68k/kernel-options.txt.
66 MCA MCA bus support is enabled.
67 MDA MDA console support is enabled.
68 MOUSE Appropriate mouse support is enabled.
69 MSI Message Signaled Interrupts (PCI).
70 MTD MTD (Memory Technology Device) support is enabled.
71 NET Appropriate network support is enabled.
72 NUMA NUMA support is enabled.
73 GENERIC_TIME The generic timeofday code is enabled.
74 NFS Appropriate NFS support is enabled.
75 OSS OSS sound support is enabled.
76 PV_OPS A paravirtualized kernel is enabled.
77 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
78 PARISC The PA-RISC architecture is enabled.
79 PCI PCI bus support is enabled.
80 PCIE PCI Express support is enabled.
81 PCMCIA The PCMCIA subsystem is enabled.
82 PNP Plug & Play support is enabled.
83 PPC PowerPC architecture is enabled.
84 PPT Parallel port support is enabled.
85 PS2 Appropriate PS/2 support is enabled.
86 RAM RAM disk support is enabled.
87 ROOTPLUG The example Root Plug LSM is enabled.
88 S390 S390 architecture is enabled.
89 SCSI Appropriate SCSI support is enabled.
90 A lot of drivers has their options described inside of
91 Documentation/scsi/.
92 SECURITY Different security models are enabled.
93 SELINUX SELinux support is enabled.
94 SERIAL Serial support is enabled.
95 SH SuperH architecture is enabled.
96 SMP The kernel is an SMP kernel.
97 SPARC Sparc architecture is enabled.
98 SWSUSP Software suspend (hibernation) is enabled.
99 SUSPEND System suspend states are enabled.
100 FTRACE Function tracing enabled.
101 TS Appropriate touchscreen support is enabled.
102 UMS USB Mass Storage support is enabled.
103 USB USB support is enabled.
104 USBHID USB Human Interface Device support is enabled.
105 V4L Video For Linux support is enabled.
106 VGA The VGA console has been enabled.
107 VT Virtual terminal support is enabled.
108 WDT Watchdog support is enabled.
109 XT IBM PC/XT MFM hard disk support is enabled.
110 X86-32 X86-32, aka i386 architecture is enabled.
111 X86-64 X86-64 architecture is enabled.
112 More X86-64 boot options can be found in
113 Documentation/x86/x86_64/boot-options.txt .
114 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
116 In addition, the following text indicates that the option:
118 BUGS= Relates to possible processor bugs on the said processor.
119 KNL Is a kernel start-up parameter.
120 BOOT Is a boot loader parameter.
122 Parameters denoted with BOOT are actually interpreted by the boot
123 loader, and have no meaning to the kernel directly.
124 Do not modify the syntax of boot loader parameters without extreme
125 need or coordination with <Documentation/x86/boot.txt>.
127 There are also arch-specific kernel-parameters not documented here.
128 See for example <Documentation/x86/x86_64/boot-options.txt>.
130 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
131 a trailing = on the name of any parameter states that that parameter will
132 be entered as an environment variable, whereas its absence indicates that
133 it will appear as a kernel argument readable via /proc/cmdline by programs
134 running once the system is up.
136 The number of kernel parameters is not limited, but the length of the
137 complete command line (parameters including spaces etc.) is limited to
138 a fixed number of characters. This limit depends on the architecture
139 and is between 256 and 4096 characters. It is defined in the file
140 ./include/asm/setup.h as COMMAND_LINE_SIZE.
143 acpi= [HW,ACPI,X86]
144 Advanced Configuration and Power Interface
145 Format: { force | off | ht | strict | noirq | rsdt }
146 force -- enable ACPI if default was off
147 off -- disable ACPI if default was on
148 noirq -- do not use ACPI for IRQ routing
149 ht -- run only enough ACPI to enable Hyper Threading
150 strict -- Be less tolerant of platforms that are not
151 strictly ACPI specification compliant.
152 rsdt -- prefer RSDT over (default) XSDT
154 See also Documentation/power/pm.txt, pci=noacpi
156 acpi_apic_instance= [ACPI, IOAPIC]
157 Format: <int>
158 2: use 2nd APIC table, if available
159 1,0: use 1st APIC table
160 default: 0
162 acpi_backlight= [HW,ACPI]
163 acpi_backlight=vendor
164 acpi_backlight=video
165 If set to vendor, prefer vendor specific driver
166 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
167 of the ACPI video.ko driver.
169 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
170 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
171 Format: <int>
172 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
173 debug output. Bits in debug_layer correspond to a
174 _COMPONENT in an ACPI source file, e.g.,
175 #define _COMPONENT ACPI_PCI_COMPONENT
176 Bits in debug_level correspond to a level in
177 ACPI_DEBUG_PRINT statements, e.g.,
178 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
179 The debug_level mask defaults to "info". See
180 Documentation/acpi/debug.txt for more information about
181 debug layers and levels.
183 Enable processor driver info messages:
184 acpi.debug_layer=0x20000000
185 Enable PCI/PCI interrupt routing info messages:
186 acpi.debug_layer=0x400000
187 Enable AML "Debug" output, i.e., stores to the Debug
188 object while interpreting AML:
189 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
190 Enable all messages related to ACPI hardware:
191 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
193 Some values produce so much output that the system is
194 unusable. The "log_buf_len" parameter may be useful
195 if you need to capture more output.
197 acpi_display_output= [HW,ACPI]
198 acpi_display_output=vendor
199 acpi_display_output=video
200 See above.
202 acpi_irq_balance [HW,ACPI]
203 ACPI will balance active IRQs
204 default in APIC mode
206 acpi_irq_nobalance [HW,ACPI]
207 ACPI will not move active IRQs (default)
208 default in PIC mode
210 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
211 Format: <irq>,<irq>...
213 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
214 use by PCI
215 Format: <irq>,<irq>...
217 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
219 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
220 Format: To spoof as Windows 98: ="Microsoft Windows"
222 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
223 acpi_osi="string1" # add string1 -- only one string
224 acpi_osi="!string2" # remove built-in string2
225 acpi_osi= # disable all strings
227 acpi_pm_good [X86]
228 Override the pmtimer bug detection: force the kernel
229 to assume that this machine's pmtimer latches its value
230 and always returns good values.
232 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
233 Format: { level | edge | high | low }
235 acpi_serialize [HW,ACPI] force serialization of AML methods
237 acpi_skip_timer_override [HW,ACPI]
238 Recognize and ignore IRQ0/pin2 Interrupt Override.
239 For broken nForce2 BIOS resulting in XT-PIC timer.
241 acpi_sleep= [HW,ACPI] Sleep options
242 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
243 old_ordering, s4_nonvs }
244 See Documentation/power/video.txt for information on
245 s3_bios and s3_mode.
246 s3_beep is for debugging; it makes the PC's speaker beep
247 as soon as the kernel's real-mode entry point is called.
248 s4_nohwsig prevents ACPI hardware signature from being
249 used during resume from hibernation.
250 old_ordering causes the ACPI 1.0 ordering of the _PTS
251 control method, with respect to putting devices into
252 low power states, to be enforced (the ACPI 2.0 ordering
253 of _PTS is used by default).
254 s4_nonvs prevents the kernel from saving/restoring the
255 ACPI NVS memory during hibernation.
257 acpi_use_timer_override [HW,ACPI]
258 Use timer override. For some broken Nvidia NF5 boards
259 that require a timer override, but don't have HPET
261 acpi_enforce_resources= [ACPI]
262 { strict | lax | no }
263 Check for resource conflicts between native drivers
264 and ACPI OperationRegions (SystemIO and SystemMemory
265 only). IO ports and memory declared in ACPI might be
266 used by the ACPI subsystem in arbitrary AML code and
267 can interfere with legacy drivers.
268 strict (default): access to resources claimed by ACPI
269 is denied; legacy drivers trying to access reserved
270 resources will fail to bind to device using them.
271 lax: access to resources claimed by ACPI is allowed;
272 legacy drivers trying to access reserved resources
273 will bind successfully but a warning message is logged.
274 no: ACPI OperationRegions are not marked as reserved,
275 no further checks are performed.
277 ad1848= [HW,OSS]
278 Format: <io>,<irq>,<dma>,<dma2>,<type>
280 add_efi_memmap [EFI; X86] Include EFI memory map in
281 kernel's map of available physical RAM.
283 advansys= [HW,SCSI]
284 See header of drivers/scsi/advansys.c.
286 advwdt= [HW,WDT] Advantech WDT
287 Format: <iostart>,<iostop>
289 aedsp16= [HW,OSS] Audio Excel DSP 16
290 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
291 See also header of sound/oss/aedsp16.c.
293 agp= [AGP]
294 { off | try_unsupported }
295 off: disable AGP support
296 try_unsupported: try to drive unsupported chipsets
297 (may crash computer or cause data corruption)
299 aha152x= [HW,SCSI]
300 See Documentation/scsi/aha152x.txt.
302 aha1542= [HW,SCSI]
303 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
305 aic7xxx= [HW,SCSI]
306 See Documentation/scsi/aic7xxx.txt.
308 aic79xx= [HW,SCSI]
309 See Documentation/scsi/aic79xx.txt.
311 amd_iommu= [HW,X86-84]
312 Pass parameters to the AMD IOMMU driver in the system.
313 Possible values are:
314 isolate - enable device isolation (each device, as far
315 as possible, will get its own protection
316 domain) [default]
317 share - put every device behind one IOMMU into the
318 same protection domain
319 fullflush - enable flushing of IO/TLB entries when
320 they are unmapped. Otherwise they are
321 flushed before they will be reused, which
322 is a lot of faster
324 amd_iommu_size= [HW,X86-64]
325 Define the size of the aperture for the AMD IOMMU
326 driver. Possible values are:
327 '32M', '64M' (default), '128M', '256M', '512M', '1G'
329 amijoy.map= [HW,JOY] Amiga joystick support
330 Map of devices attached to JOY0DAT and JOY1DAT
331 Format: <a>,<b>
332 See also Documentation/kernel/input/joystick.txt
334 analog.map= [HW,JOY] Analog joystick and gamepad support
335 Specifies type or capabilities of an analog joystick
336 connected to one of 16 gameports
337 Format: <type1>,<type2>,..<type16>
339 apc= [HW,SPARC]
340 Power management functions (SPARCstation-4/5 + deriv.)
341 Format: noidle
342 Disable APC CPU standby support. SPARCstation-Fox does
343 not play well with APC CPU idle - disable it if you have
344 APC and your system crashes randomly.
346 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
347 Change the output verbosity whilst booting
348 Format: { quiet (default) | verbose | debug }
349 Change the amount of debugging information output
350 when initialising the APIC and IO-APIC components.
352 apm= [APM] Advanced Power Management
353 See header of arch/x86/kernel/apm_32.c.
355 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
356 Format: <io>,<irq>,<nodeID>
358 ataflop= [HW,M68k]
360 atarimouse= [HW,MOUSE] Atari Mouse
362 atascsi= [HW,SCSI] Atari SCSI
364 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
365 EzKey and similar keyboards
367 atkbd.reset= [HW] Reset keyboard during initialization
369 atkbd.set= [HW] Select keyboard code set
370 Format: <int> (2 = AT (default), 3 = PS/2)
372 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
373 keyboards
375 atkbd.softraw= [HW] Choose between synthetic and real raw mode
376 Format: <bool> (0 = real, 1 = synthetic (default))
378 atkbd.softrepeat= [HW]
379 Use software keyboard repeat
381 autotest [IA64]
383 baycom_epp= [HW,AX25]
384 Format: <io>,<mode>
386 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
387 Format: <io>,<mode>
388 See header of drivers/net/hamradio/baycom_par.c.
390 baycom_ser_fdx= [HW,AX25]
391 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
392 Format: <io>,<irq>,<mode>[,<baud>]
393 See header of drivers/net/hamradio/baycom_ser_fdx.c.
395 baycom_ser_hdx= [HW,AX25]
396 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
397 Format: <io>,<irq>,<mode>
398 See header of drivers/net/hamradio/baycom_ser_hdx.c.
400 boot_delay= Milliseconds to delay each printk during boot.
401 Values larger than 10 seconds (10000) are changed to
402 no delay (0).
403 Format: integer
405 bootmem_debug [KNL] Enable bootmem allocator debug messages.
407 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
408 bttv.radio= Most important insmod options are available as
409 kernel args too.
410 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
411 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
413 BusLogic= [HW,SCSI]
414 See drivers/scsi/BusLogic.c, comment before function
415 BusLogic_ParseDriverOptions().
417 c101= [NET] Moxa C101 synchronous serial card
419 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
420 Sometimes CPU hardware bugs make them report the cache
421 size incorrectly. The kernel will attempt work arounds
422 to fix known problems, but for some CPUs it is not
423 possible to determine what the correct size should be.
424 This option provides an override for these situations.
426 capability.disable=
427 [SECURITY] Disable capabilities. This would normally
428 be used only if an alternative security model is to be
429 configured. Potentially dangerous and should only be
430 used if you are entirely sure of the consequences.
432 ccw_timeout_log [S390]
433 See Documentation/s390/CommonIO for details.
435 cgroup_disable= [KNL] Disable a particular controller
436 Format: {name of the controller(s) to disable}
437 {Currently supported controllers - "memory"}
439 checkreqprot [SELINUX] Set initial checkreqprot flag value.
440 Format: { "0" | "1" }
441 See security/selinux/Kconfig help text.
442 0 -- check protection applied by kernel (includes
443 any implied execute protection).
444 1 -- check protection requested by application.
445 Default value is set via a kernel config option.
446 Value can be changed at runtime via
447 /selinux/checkreqprot.
449 cio_ignore= [S390]
450 See Documentation/s390/CommonIO for details.
452 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
453 [Deprecated]
454 Forces specified clocksource (if available) to be used
455 when calculating gettimeofday(). If specified
456 clocksource is not available, it defaults to PIT.
457 Format: { pit | tsc | cyclone | pmtmr }
459 clocksource= [GENERIC_TIME] Override the default clocksource
460 Format: <string>
461 Override the default clocksource and use the clocksource
462 with the name specified.
463 Some clocksource names to choose from, depending on
464 the platform:
465 [all] jiffies (this is the base, fallback clocksource)
466 [ACPI] acpi_pm
467 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
468 pxa_timer,timer3,32k_counter,timer0_1
469 [AVR32] avr32
470 [X86-32] pit,hpet,tsc,vmi-timer;
471 scx200_hrt on Geode; cyclone on IBM x440
472 [MIPS] MIPS
473 [PARISC] cr16
474 [S390] tod
475 [SH] SuperH
476 [SPARC64] tick
477 [X86-64] hpet,tsc
479 clearcpuid=BITNUM [X86]
480 Disable CPUID feature X for the kernel. See
481 arch/x86/include/asm/cpufeature.h for the valid bit
482 numbers. Note the Linux specific bits are not necessarily
483 stable over kernel options, but the vendor specific
484 ones should be.
485 Also note that user programs calling CPUID directly
486 or using the feature without checking anything
487 will still see it. This just prevents it from
488 being used by the kernel or shown in /proc/cpuinfo.
489 Also note the kernel might malfunction if you disable
490 some critical bits.
492 code_bytes [X86] How many bytes of object code to print
493 in an oops report.
494 Range: 0 - 8192
495 Default: 64
497 com20020= [HW,NET] ARCnet - COM20020 chipset
498 Format:
499 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
501 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
502 Format: <io>[,<irq>]
504 com90xx= [HW,NET]
505 ARCnet - COM90xx chipset (memory-mapped buffers)
506 Format: <io>[,<irq>[,<memstart>]]
508 condev= [HW,S390] console device
509 conmode=
511 console= [KNL] Output console device and options.
513 tty<n> Use the virtual console device <n>.
515 ttyS<n>[,options]
516 ttyUSB0[,options]
517 Use the specified serial port. The options are of
518 the form "bbbbpnf", where "bbbb" is the baud rate,
519 "p" is parity ("n", "o", or "e"), "n" is number of
520 bits, and "f" is flow control ("r" for RTS or
521 omit it). Default is "9600n8".
523 See Documentation/serial-console.txt for more
524 information. See
525 Documentation/networking/netconsole.txt for an
526 alternative.
528 uart[8250],io,<addr>[,options]
529 uart[8250],mmio,<addr>[,options]
530 Start an early, polled-mode console on the 8250/16550
531 UART at the specified I/O port or MMIO address,
532 switching to the matching ttyS device later. The
533 options are the same as for ttyS, above.
535 If the device connected to the port is not a TTY but a braille
536 device, prepend "brl," before the device type, for instance
537 console=brl,ttyS0
538 For now, only VisioBraille is supported.
540 coredump_filter=
541 [KNL] Change the default value for
542 /proc/<pid>/coredump_filter.
543 See also Documentation/filesystems/proc.txt.
545 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
546 Format:
547 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
549 crashkernel=nn[KMG]@ss[KMG]
550 [KNL] Reserve a chunk of physical memory to
551 hold a kernel to switch to with kexec on panic.
553 crashkernel=range1:size1[,range2:size2,...][@offset]
554 [KNL] Same as above, but depends on the memory
555 in the running system. The syntax of range is
556 start-[end] where start and end are both
557 a memory unit (amount[KMG]). See also
558 Documentation/kdump/kdump.txt for a example.
560 cs89x0_dma= [HW,NET]
561 Format: <dma>
563 cs89x0_media= [HW,NET]
564 Format: { rj45 | aui | bnc }
566 dasd= [HW,NET]
567 See header of drivers/s390/block/dasd_devmap.c.
569 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
570 (one device per port)
571 Format: <port#>,<type>
572 See also Documentation/input/joystick-parport.txt
574 debug [KNL] Enable kernel debugging (events log level).
576 debug_locks_verbose=
577 [KNL] verbose self-tests
578 Format=<0|1>
579 Print debugging info while doing the locking API
580 self-tests.
581 We default to 0 (no extra messages), setting it to
582 1 will print _a lot_ more information - normally
583 only useful to kernel developers.
585 debug_objects [KNL] Enable object debugging
587 no_debug_objects
588 [KNL] Disable object debugging
590 debugpat [X86] Enable PAT debugging
592 decnet.addr= [HW,NET]
593 Format: <area>[,<node>]
594 See also Documentation/networking/decnet.txt.
596 default_hugepagesz=
597 [same as hugepagesz=] The size of the default
598 HugeTLB page size. This is the size represented by
599 the legacy /proc/ hugepages APIs, used for SHM, and
600 default size when mounting hugetlbfs filesystems.
601 Defaults to the default architecture's huge page size
602 if not specified.
604 dhash_entries= [KNL]
605 Set number of hash buckets for dentry cache.
607 digi= [HW,SERIAL]
608 IO parameters + enable/disable command.
610 digiepca= [HW,SERIAL]
611 See drivers/char/README.epca and
612 Documentation/serial/digiepca.txt.
614 disable_mtrr_cleanup [X86]
615 The kernel tries to adjust MTRR layout from continuous
616 to discrete, to make X server driver able to add WB
617 entry later. This parameter disables that.
619 disable_mtrr_trim [X86, Intel and AMD only]
620 By default the kernel will trim any uncacheable
621 memory out of your available memory pool based on
622 MTRR settings. This parameter disables that behavior,
623 possibly causing your machine to run very slowly.
625 disable_timer_pin_1 [X86]
626 Disable PIN 1 of APIC timer
627 Can be useful to work around chipset bugs.
629 dmasound= [HW,OSS] Sound subsystem buffers
631 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
632 this option disables the debugging code at boot.
634 dma_debug_entries=<number>
635 This option allows to tune the number of preallocated
636 entries for DMA-API debugging code. One entry is
637 required per DMA-API allocation. Use this if the
638 DMA-API debugging code disables itself because the
639 architectural default is too low.
641 dscc4.setup= [NET]
643 dtc3181e= [HW,SCSI]
645 dynamic_printk Enables pr_debug()/dev_dbg() calls if
646 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
647 These can also be switched on/off via
648 <debugfs>/dynamic_printk/modules
650 earlycon= [KNL] Output early console device and options.
651 uart[8250],io,<addr>[,options]
652 uart[8250],mmio,<addr>[,options]
653 Start an early, polled-mode console on the 8250/16550
654 UART at the specified I/O port or MMIO address.
655 The options are the same as for ttyS, above.
657 earlyprintk= [X86,SH,BLACKFIN]
658 earlyprintk=vga
659 earlyprintk=serial[,ttySn[,baudrate]]
660 earlyprintk=dbgp
662 Append ",keep" to not disable it when the real console
663 takes over.
665 Only vga or serial or usb debug port at a time.
667 Currently only ttyS0 and ttyS1 are supported.
669 Interaction with the standard serial driver is not
670 very good.
672 The VGA output is eventually overwritten by the real
673 console.
675 eata= [HW,SCSI]
677 edd= [EDD]
678 Format: {"off" | "on" | "skip[mbr]"}
680 eisa_irq_edge= [PARISC,HW]
681 See header of drivers/parisc/eisa.c.
683 elanfreq= [X86-32]
684 See comment before function elanfreq_setup() in
685 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
687 elevator= [IOSCHED]
688 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
689 See Documentation/block/as-iosched.txt and
690 Documentation/block/deadline-iosched.txt for details.
692 elfcorehdr= [IA64,PPC,SH,X86]
693 Specifies physical address of start of kernel core
694 image elf header. Generally kexec loader will
695 pass this option to capture kernel.
696 See Documentation/kdump/kdump.txt for details.
698 enable_mtrr_cleanup [X86]
699 The kernel tries to adjust MTRR layout from continuous
700 to discrete, to make X server driver able to add WB
701 entry later. This parameter enables that.
703 enable_timer_pin_1 [X86]
704 Enable PIN 1 of APIC timer
705 Can be useful to work around chipset bugs
706 (in particular on some ATI chipsets).
707 The kernel tries to set a reasonable default.
709 enforcing [SELINUX] Set initial enforcing status.
710 Format: {"0" | "1"}
711 See security/selinux/Kconfig help text.
712 0 -- permissive (log only, no denials).
713 1 -- enforcing (deny and log).
714 Default value is 0.
715 Value can be changed at runtime via /selinux/enforce.
717 ether= [HW,NET] Ethernet cards parameters
718 This option is obsoleted by the "netdev=" option, which
719 has equivalent usage. See its documentation for details.
721 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
722 Format: <io>[,<irq>]
724 failslab=
725 fail_page_alloc=
726 fail_make_request=[KNL]
727 General fault injection mechanism.
728 Format: <interval>,<probability>,<space>,<times>
729 See also /Documentation/fault-injection/.
731 fd_mcs= [HW,SCSI]
732 See header of drivers/scsi/fd_mcs.c.
734 fdomain= [HW,SCSI]
735 See header of drivers/scsi/fdomain.c.
737 floppy= [HW]
738 See Documentation/blockdev/floppy.txt.
740 force_pal_cache_flush
741 [IA-64] Avoid check_sal_cache_flush which may hang on
742 buggy SAL_CACHE_FLUSH implementations. Using this
743 parameter will force ia64_sal_cache_flush to call
744 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
746 ftrace=[tracer]
747 [ftrace] will set and start the specified tracer
748 as early as possible in order to facilitate early
749 boot debugging.
751 ftrace_dump_on_oops
752 [ftrace] will dump the trace buffers on oops.
754 gamecon.map[2|3]=
755 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
756 support via parallel port (up to 5 devices per port)
757 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
758 See also Documentation/input/joystick-parport.txt
760 gamma= [HW,DRM]
762 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
763 Format: off | on
764 default: on
766 gdth= [HW,SCSI]
767 See header of drivers/scsi/gdth.c.
769 gpt [EFI] Forces disk with valid GPT signature but
770 invalid Protective MBR to be treated as GPT.
772 gvp11= [HW,SCSI]
774 hashdist= [KNL,NUMA] Large hashes allocated during boot
775 are distributed across NUMA nodes. Defaults on
776 for 64bit NUMA, off otherwise.
777 Format: 0 | 1 (for off | on)
779 hcl= [IA-64] SGI's Hardware Graph compatibility layer
781 hd= [EIDE] (E)IDE hard drive subsystem geometry
782 Format: <cyl>,<head>,<sect>
784 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
785 size of <nn>. This works even on boxes that have no
786 highmem otherwise. This also works to reduce highmem
787 size on bigger boxes.
789 highres= [KNL] Enable/disable high resolution timer mode.
790 Valid parameters: "on", "off"
791 Default: "on"
793 hisax= [HW,ISDN]
794 See Documentation/isdn/README.HiSax.
796 hlt [BUGS=ARM,SH]
798 hpet= [X86-32,HPET] option to control HPET usage
799 Format: { enable (default) | disable | force |
800 verbose }
801 disable: disable HPET and use PIT instead
802 force: allow force enabled of undocumented chips (ICH4,
803 VIA, nVidia)
804 verbose: show contents of HPET registers during setup
806 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
807 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
808 On x86-64 and powerpc, this option can be specified
809 multiple times interleaved with hugepages= to reserve
810 huge pages of different sizes. Valid pages sizes on
811 x86-64 are 2M (when the CPU supports "pse") and 1G
812 (when the CPU supports the "pdpe1gb" cpuinfo flag)
813 Note that 1GB pages can only be allocated at boot time
814 using hugepages= and not freed afterwards.
816 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
817 terminal devices. Valid values: 0..8
818 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
819 If specified, z/VM IUCV HVC accepts connections
820 from listed z/VM user IDs only.
822 i2c_bus= [HW] Override the default board specific I2C bus speed
823 or register an additional I2C bus that is not
824 registered from board initialization code.
825 Format:
826 <bus_id>,<clkrate>
828 i8042.debug [HW] Toggle i8042 debug mode
829 i8042.direct [HW] Put keyboard port into non-translated mode
830 i8042.dumbkbd [HW] Pretend that controller can only read data from
831 keyboard and cannot control its state
832 (Don't attempt to blink the leds)
833 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
834 i8042.nokbd [HW] Don't check/create keyboard port
835 i8042.noloop [HW] Disable the AUX Loopback command while probing
836 for the AUX port
837 i8042.nomux [HW] Don't check presence of an active multiplexing
838 controller
839 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
840 controllers
841 i8042.panicblink=
842 [HW] Frequency with which keyboard LEDs should blink
843 when kernel panics (default is 0.5 sec)
844 i8042.reset [HW] Reset the controller during init and cleanup
845 i8042.unlock [HW] Unlock (ignore) the keylock
847 i810= [HW,DRM]
849 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
850 indicates that the driver is running on unsupported
851 hardware.
852 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
853 does not match list of supported models.
854 i8k.power_status
855 [HW] Report power status in /proc/i8k
856 (disabled by default)
857 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
858 capability is set.
860 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
861 See Documentation/mca.txt.
863 icn= [HW,ISDN]
864 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
866 ide-core.nodma= [HW] (E)IDE subsystem
867 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
868 .vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom
869 .chs .ignore_cable are additional options
870 See Documentation/ide/ide.txt.
872 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
873 See Documentation/ide/ide.txt.
875 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
876 Claim all unknown PCI IDE storage controllers.
878 idle= [X86]
879 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
880 Poll forces a polling idle loop that can slightly
881 improve the performance of waking up a idle CPU, but
882 will use a lot of power and make the system run hot.
883 Not recommended.
884 idle=mwait: On systems which support MONITOR/MWAIT but
885 the kernel chose to not use it because it doesn't save
886 as much power as a normal idle loop, use the
887 MONITOR/MWAIT idle loop anyways. Performance should be
888 the same as idle=poll.
889 idle=halt: Halt is forced to be used for CPU idle.
890 In such case C2/C3 won't be used again.
891 idle=nomwait: Disable mwait for CPU C-states
893 ignore_loglevel [KNL]
894 Ignore loglevel setting - this will print /all/
895 kernel messages to the console. Useful for debugging.
897 ihash_entries= [KNL]
898 Set number of hash buckets for inode cache.
900 ima_audit= [IMA]
901 Format: { "0" | "1" }
902 0 -- integrity auditing messages. (Default)
903 1 -- enable informational integrity auditing messages.
905 ima_hash= [IMA]
906 Formt: { "sha1" | "md5" }
907 default: "sha1"
909 in2000= [HW,SCSI]
910 See header of drivers/scsi/in2000.c.
912 init= [KNL]
913 Format: <full_path>
914 Run specified binary instead of /sbin/init as init
915 process.
917 initcall_debug [KNL] Trace initcalls as they are executed. Useful
918 for working out where the kernel is dying during
919 startup.
921 initrd= [BOOT] Specify the location of the initial ramdisk
923 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
924 Format: <irq>
926 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
927 on
928 Enable intel iommu driver.
929 off
930 Disable intel iommu driver.
931 igfx_off [Default Off]
932 By default, gfx is mapped as normal device. If a gfx
933 device has a dedicated DMAR unit, the DMAR unit is
934 bypassed by not enabling DMAR with this option. In
935 this case, gfx device will use physical address for
936 DMA.
937 forcedac [x86_64]
938 With this option iommu will not optimize to look
939 for io virtual address below 32 bit forcing dual
940 address cycle on pci bus for cards supporting greater
941 than 32 bit addressing. The default is to look
942 for translation below 32 bit and if not available
943 then look in the higher range.
944 strict [Default Off]
945 With this option on every unmap_single operation will
946 result in a hardware IOTLB flush operation as opposed
947 to batching them for performance.
949 inttest= [IA64]
951 iomem= Disable strict checking of access to MMIO memory
952 strict regions from userspace.
953 relaxed
955 iommu= [x86]
956 off
957 force
958 noforce
959 biomerge
960 panic
961 nopanic
962 merge
963 nomerge
964 forcesac
965 soft
967 io7= [HW] IO7 for Marvel based alpha systems
968 See comment before marvel_specify_io7 in
969 arch/alpha/kernel/core_marvel.c.
971 io_delay= [X86] I/O delay method
972 0x80
973 Standard port 0x80 based delay
974 0xed
975 Alternate port 0xed based delay (needed on some systems)
976 udelay
977 Simple two microseconds delay
978 none
979 No delay
981 ip= [IP_PNP]
982 See Documentation/filesystems/nfsroot.txt.
984 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
985 See comment before ip2_setup() in
986 drivers/char/ip2/ip2base.c.
988 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
989 See header of drivers/scsi/ips.c.
991 irqfixup [HW]
992 When an interrupt is not handled search all handlers
993 for it. Intended to get systems with badly broken
994 firmware running.
996 irqpoll [HW]
997 When an interrupt is not handled search all handlers
998 for it. Also check all handlers each timer
999 interrupt. Intended to get systems with badly broken
1000 firmware running.
1002 isapnp= [ISAPNP]
1003 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1005 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1006 Format:
1007 <cpu number>,...,<cpu number>
1008 or
1009 <cpu number>-<cpu number>
1010 (must be a positive range in ascending order)
1011 or a mixture
1012 <cpu number>,...,<cpu number>-<cpu number>
1014 This option can be used to specify one or more CPUs
1015 to isolate from the general SMP balancing and scheduling
1016 algorithms. You can move a process onto or off an
1017 "isolated" CPU via the CPU affinity syscalls or cpuset.
1018 <cpu number> begins at 0 and the maximum value is
1019 "number of CPUs in system - 1".
1021 This option is the preferred way to isolate CPUs. The
1022 alternative -- manually setting the CPU mask of all
1023 tasks in the system -- can cause problems and
1024 suboptimal load balancer performance.
1026 iucv= [HW,NET]
1028 js= [HW,JOY] Analog joystick
1029 See Documentation/input/joystick.txt.
1031 keepinitrd [HW,ARM]
1033 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1034 specifies the amount of memory usable by the kernel
1035 for non-movable allocations. The requested amount is
1036 spread evenly throughout all nodes in the system. The
1037 remaining memory in each node is used for Movable
1038 pages. In the event, a node is too small to have both
1039 kernelcore and Movable pages, kernelcore pages will
1040 take priority and other nodes will have a larger number
1041 of kernelcore pages. The Movable zone is used for the
1042 allocation of pages that may be reclaimed or moved
1043 by the page migration subsystem. This means that
1044 HugeTLB pages may not be allocated from this zone.
1045 Note that allocations like PTEs-from-HighMem still
1046 use the HighMem zone if it exists, and the Normal
1047 zone if it does not.
1049 kmemtrace.enable= [KNL,KMEMTRACE] Format: { yes | no }
1050 Controls whether kmemtrace is enabled
1051 at boot-time.
1053 kmemtrace.subbufs=n [KNL,KMEMTRACE] Overrides the number of
1054 subbufs kmemtrace's relay channel has. Set this
1055 higher than default (KMEMTRACE_N_SUBBUFS in code) if
1056 you experience buffer overruns.
1058 kgdboc= [HW] kgdb over consoles.
1059 Requires a tty driver that supports console polling.
1060 (only serial suported for now)
1061 Format: <serial_device>[,baud]
1063 kmac= [MIPS] korina ethernet MAC address.
1064 Configure the RouterBoard 532 series on-chip
1065 Ethernet adapter MAC address.
1067 kstack=N [X86] Print N words from the kernel stack
1068 in oops dumps.
1070 l2cr= [PPC]
1072 l3cr= [PPC]
1074 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1075 disabled it.
1077 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1078 in C2 power state.
1080 libata.dma= [LIBATA] DMA control
1081 libata.dma=0 Disable all PATA and SATA DMA
1082 libata.dma=1 PATA and SATA Disk DMA only
1083 libata.dma=2 ATAPI (CDROM) DMA only
1084 libata.dma=4 Compact Flash DMA only
1085 Combinations also work, so libata.dma=3 enables DMA
1086 for disks and CDROMs, but not CFs.
1088 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1089 when set.
1090 Format: <int>
1092 libata.force= [LIBATA] Force configurations. The format is comma
1093 separated list of "[ID:]VAL" where ID is
1094 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1095 matching port, link or device. Basically, it matches
1096 the ATA ID string printed on console by libata. If
1097 the whole ID part is omitted, the last PORT and DEVICE
1098 values are used. If ID hasn't been specified yet, the
1099 configuration applies to all ports, links and devices.
1101 If only DEVICE is omitted, the parameter applies to
1102 the port and all links and devices behind it. DEVICE
1103 number of 0 either selects the first device or the
1104 first fan-out link behind PMP device. It does not
1105 select the host link. DEVICE number of 15 selects the
1106 host link and device attached to it.
1108 The VAL specifies the configuration to force. As long
1109 as there's no ambiguity shortcut notation is allowed.
1110 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1111 The following configurations can be forced.
1113 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1114 Any ID with matching PORT is used.
1116 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1118 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1119 udma[/][16,25,33,44,66,100,133] notation is also
1120 allowed.
1122 * [no]ncq: Turn on or off NCQ.
1124 * nohrst, nosrst, norst: suppress hard, soft
1125 and both resets.
1127 If there are multiple matching configurations changing
1128 the same attribute, the last one is used.
1130 lmb=debug [KNL] Enable lmb debug messages.
1132 load_ramdisk= [RAM] List of ramdisks to load from floppy
1133 See Documentation/blockdev/ramdisk.txt.
1135 lockd.nlm_grace_period=P [NFS] Assign grace period.
1136 Format: <integer>
1138 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1139 Format: <integer>
1141 lockd.nlm_timeout=T [NFS] Assign timeout value.
1142 Format: <integer>
1144 lockd.nlm_udpport=M [NFS] Assign UDP port.
1145 Format: <integer>
1147 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1148 Format: <irq>
1150 loglevel= All Kernel Messages with a loglevel smaller than the
1151 console loglevel will be printed to the console. It can
1152 also be changed with klogd or other programs. The
1153 loglevels are defined as follows:
1155 0 (KERN_EMERG) system is unusable
1156 1 (KERN_ALERT) action must be taken immediately
1157 2 (KERN_CRIT) critical conditions
1158 3 (KERN_ERR) error conditions
1159 4 (KERN_WARNING) warning conditions
1160 5 (KERN_NOTICE) normal but significant condition
1161 6 (KERN_INFO) informational
1162 7 (KERN_DEBUG) debug-level messages
1164 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1165 Format: { n | nk | nM }
1166 n must be a power of two. The default size
1167 is set in the kernel config file.
1169 logo.nologo [FB] Disables display of the built-in Linux logo.
1170 This may be used to provide more screen space for
1171 kernel log messages and is useful when debugging
1172 kernel boot problems.
1174 lp=0 [LP] Specify parallel ports to use, e.g,
1175 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1176 lp=reset first parallel port). 'lp=0' disables the
1177 lp=auto printer driver. 'lp=reset' (which can be
1178 specified in addition to the ports) causes
1179 attached printers to be reset. Using
1180 lp=port1,port2,... specifies the parallel ports
1181 to associate lp devices with, starting with
1182 lp0. A port specification may be 'none' to skip
1183 that lp device, or a parport name such as
1184 'parport0'. Specifying 'lp=auto' instead of a
1185 port specification list means that device IDs
1186 from each port should be examined, to see if
1187 an IEEE 1284-compliant printer is attached; if
1188 so, the driver will manage that printer.
1189 See also header of drivers/char/lp.c.
1191 lpj=n [KNL]
1192 Sets loops_per_jiffy to given constant, thus avoiding
1193 time-consuming boot-time autodetection (up to 250 ms per
1194 CPU). 0 enables autodetection (default). To determine
1195 the correct value for your kernel, boot with normal
1196 autodetection and see what value is printed. Note that
1197 on SMP systems the preset will be applied to all CPUs,
1198 which is likely to cause problems if your CPUs need
1199 significantly divergent settings. An incorrect value
1200 will cause delays in the kernel to be wrong, leading to
1201 unpredictable I/O errors and other breakage. Although
1202 unlikely, in the extreme case this might damage your
1203 hardware.
1205 ltpc= [NET]
1206 Format: <io>,<irq>,<dma>
1208 mac5380= [HW,SCSI] Format:
1209 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1211 machvec= [IA64] Force the use of a particular machine-vector
1212 (machvec) in a generic kernel.
1213 Example: machvec=hpzx1_swiotlb
1215 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1216 than or equal to this physical address is ignored.
1218 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1219 should make use of. maxcpus=n : n >= 0 limits the
1220 kernel to using 'n' processors. n=0 is a special case,
1221 it is equivalent to "nosmp", which also disables
1222 the IO APIC.
1224 max_loop= [LOOP] Maximum number of loopback devices that can
1225 be mounted
1226 Format: <1-256>
1228 max_luns= [SCSI] Maximum number of LUNs to probe.
1229 Should be between 1 and 2^32-1.
1231 max_report_luns=
1232 [SCSI] Maximum number of LUNs received.
1233 Should be between 1 and 16384.
1235 mcatest= [IA-64]
1237 mce [X86-32] Machine Check Exception
1239 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1241 md= [HW] RAID subsystems devices and level
1242 See Documentation/md.txt.
1244 mdacon= [MDA]
1245 Format: <first>,<last>
1246 Specifies range of consoles to be captured by the MDA.
1248 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1249 Amount of memory to be used when the kernel is not able
1250 to see the whole system memory or for test.
1251 [X86-32] Use together with memmap= to avoid physical
1252 address space collisions. Without memmap= PCI devices
1253 could be placed at addresses belonging to unused RAM.
1255 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1256 memory.
1258 memchunk=nn[KMG]
1259 [KNL,SH] Allow user to override the default size for
1260 per-device physically contiguous DMA buffers.
1262 memmap=exactmap [KNL,X86] Enable setting of an exact
1263 E820 memory map, as specified by the user.
1264 Such memmap=exactmap lines can be constructed based on
1265 BIOS output or other requirements. See the memmap=nn@ss
1266 option description.
1268 memmap=nn[KMG]@ss[KMG]
1269 [KNL] Force usage of a specific region of memory
1270 Region of memory to be used, from ss to ss+nn.
1272 memmap=nn[KMG]#ss[KMG]
1273 [KNL,ACPI] Mark specific memory as ACPI data.
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 reserved.
1278 Region of memory to be used, from ss to ss+nn.
1279 Example: Exclude memory from 0x18690000-0x1869ffff
1280 memmap=64K$0x18690000
1281 or
1282 memmap=0x10000$0x18690000
1284 memory_corruption_check=0/1 [X86]
1285 Some BIOSes seem to corrupt the first 64k of
1286 memory when doing things like suspend/resume.
1287 Setting this option will scan the memory
1288 looking for corruption. Enabling this will
1289 both detect corruption and prevent the kernel
1290 from using the memory being corrupted.
1291 However, its intended as a diagnostic tool; if
1292 repeatable BIOS-originated corruption always
1293 affects the same memory, you can use memmap=
1294 to prevent the kernel from using that memory.
1296 memory_corruption_check_size=size [X86]
1297 By default it checks for corruption in the low
1298 64k, making this memory unavailable for normal
1299 use. Use this parameter to scan for
1300 corruption in more or less memory.
1302 memory_corruption_check_period=seconds [X86]
1303 By default it checks for corruption every 60
1304 seconds. Use this parameter to check at some
1305 other rate. 0 disables periodic checking.
1307 memtest= [KNL,X86] Enable memtest
1308 Format: <integer>
1309 default : 0 <disable>
1310 Specifies the number of memtest passes to be
1311 performed. Each pass selects another test
1312 pattern from a given set of patterns. Memtest
1313 fills the memory with this pattern, validates
1314 memory contents and reserves bad memory
1315 regions that are detected.
1317 meye.*= [HW] Set MotionEye Camera parameters
1318 See Documentation/video4linux/meye.txt.
1320 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1321 Multi-Function General Purpose Timers on AMD Geode
1322 platforms.
1324 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1325 the BIOS has incorrectly applied a workaround. TinyBIOS
1326 version 0.98 is known to be affected, 0.99 fixes the
1327 problem by letting the user disable the workaround.
1329 mga= [HW,DRM]
1331 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1332 physical address is ignored.
1334 mminit_loglevel=
1335 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1336 parameter allows control of the logging verbosity for
1337 the additional memory initialisation checks. A value
1338 of 0 disables mminit logging and a level of 4 will
1339 log everything. Information is printed at KERN_DEBUG
1340 so loglevel=8 may also need to be specified.
1342 mousedev.tap_time=
1343 [MOUSE] Maximum time between finger touching and
1344 leaving touchpad surface for touch to be considered
1345 a tap and be reported as a left button click (for
1346 touchpads working in absolute mode only).
1347 Format: <msecs>
1348 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1349 reporting absolute coordinates, such as tablets
1350 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1351 reporting absolute coordinates, such as tablets
1353 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1354 is similar to kernelcore except it specifies the
1355 amount of memory used for migratable allocations.
1356 If both kernelcore and movablecore is specified,
1357 then kernelcore will be at *least* the specified
1358 value but may be more. If movablecore on its own
1359 is specified, the administrator must be careful
1360 that the amount of memory usable for all allocations
1361 is not too small.
1363 mpu401= [HW,OSS]
1364 Format: <io>,<irq>
1366 MTD_Partition= [MTD]
1367 Format: <name>,<region-number>,<size>,<offset>
1369 MTD_Region= [MTD] Format:
1370 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1372 mtdparts= [MTD]
1373 See drivers/mtd/cmdlinepart.c.
1375 mtdset= [ARM]
1376 ARM/S3C2412 JIVE boot control
1378 See arch/arm/mach-s3c2412/mach-jive.c
1380 mtouchusb.raw_coordinates=
1381 [HW] Make the MicroTouch USB driver use raw coordinates
1382 ('y', default) or cooked coordinates ('n')
1384 mtrr_chunk_size=nn[KMG] [X86]
1385 used for mtrr cleanup. It is largest continous chunk
1386 that could hold holes aka. UC entries.
1388 mtrr_gran_size=nn[KMG] [X86]
1389 Used for mtrr cleanup. It is granularity of mtrr block.
1390 Default is 1.
1391 Large value could prevent small alignment from
1392 using up MTRRs.
1394 mtrr_spare_reg_nr=n [X86]
1395 Format: <integer>
1396 Range: 0,7 : spare reg number
1397 Default : 1
1398 Used for mtrr cleanup. It is spare mtrr entries number.
1399 Set to 2 or more if your graphical card needs more.
1401 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1403 NCR_D700= [HW,SCSI]
1404 See header of drivers/scsi/NCR_D700.c.
1406 ncr5380= [HW,SCSI]
1408 ncr53c400= [HW,SCSI]
1410 ncr53c400a= [HW,SCSI]
1412 ncr53c406a= [HW,SCSI]
1414 ncr53c8xx= [HW,SCSI]
1416 netdev= [NET] Network devices parameters
1417 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1418 Note that mem_start is often overloaded to mean
1419 something different and driver-specific.
1420 This usage is only documented in each driver source
1421 file if at all.
1423 nf_conntrack.acct=
1424 [NETFILTER] Enable connection tracking flow accounting
1425 0 to disable accounting
1426 1 to enable accounting
1427 Default value depends on CONFIG_NF_CT_ACCT that is
1428 going to be removed in 2.6.29.
1430 nfsaddrs= [NFS]
1431 See Documentation/filesystems/nfsroot.txt.
1433 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1434 See Documentation/filesystems/nfsroot.txt.
1436 nfs.callback_tcpport=
1437 [NFS] set the TCP port on which the NFSv4 callback
1438 channel should listen.
1440 nfs.idmap_cache_timeout=
1441 [NFS] set the maximum lifetime for idmapper cache
1442 entries.
1444 nfs.enable_ino64=
1445 [NFS] enable 64-bit inode numbers.
1446 If zero, the NFS client will fake up a 32-bit inode
1447 number for the readdir() and stat() syscalls instead
1448 of returning the full 64-bit number.
1449 The default is to return 64-bit inode numbers.
1451 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1452 when a NMI is triggered.
1453 Format: [state][,regs][,debounce][,die]
1455 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1456 Format: [panic,][num]
1457 Valid num: 0,1,2
1458 0 - turn nmi_watchdog off
1459 1 - use the IO-APIC timer for the NMI watchdog
1460 2 - use the local APIC for the NMI watchdog using
1461 a performance counter. Note: This will use one
1462 performance counter and the local APIC's performance
1463 vector.
1464 When panic is specified, panic when an NMI watchdog
1465 timeout occurs.
1466 This is useful when you use a panic=... timeout and
1467 need the box quickly up again.
1468 Instead of 1 and 2 it is possible to use the following
1469 symbolic names: lapic and ioapic
1470 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1472 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1473 emulation library even if a 387 maths coprocessor
1474 is present.
1476 no_console_suspend
1477 [HW] Never suspend the console
1478 Disable suspending of consoles during suspend and
1479 hibernate operations. Once disabled, debugging
1480 messages can reach various consoles while the rest
1481 of the system is being put to sleep (ie, while
1482 debugging driver suspend/resume hooks). This may
1483 not work reliably with all consoles, but is known
1484 to work with serial and VGA consoles.
1486 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1487 caches in the slab allocator. Saves per-node memory,
1488 but will impact performance.
1490 noalign [KNL,ARM]
1492 noapic [SMP,APIC] Tells the kernel to not make use of any
1493 IOAPICs that may be present in the system.
1495 nobats [PPC] Do not use BATs for mapping kernel lowmem
1496 on "Classic" PPC cores.
1498 nocache [ARM]
1500 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1502 nodelayacct [KNL] Disable per-task delay accounting
1504 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1506 nodsp [SH] Disable hardware DSP at boot time.
1508 noefi [X86] Disable EFI runtime services support.
1510 noexec [IA-64]
1512 noexec [X86]
1513 On X86-32 available only on PAE configured kernels.
1514 noexec=on: enable non-executable mappings (default)
1515 noexec=off: disable non-executable mappings
1517 noexec32 [X86-64]
1518 This affects only 32-bit executables.
1519 noexec32=on: enable non-executable mappings (default)
1520 read doesn't imply executable mappings
1521 noexec32=off: disable non-executable mappings
1522 read implies executable mappings
1524 nofpu [SH] Disable hardware FPU at boot time.
1526 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1527 register save and restore. The kernel will only save
1528 legacy floating-point registers on task switch.
1530 noxsave [BUGS=X86] Disables x86 extended register state save
1531 and restore using xsave. The kernel will fallback to
1532 enabling legacy floating-point and sse state.
1534 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1535 wfi(ARM) instruction doesn't work correctly and not to
1536 use it. This is also useful when using JTAG debugger.
1538 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1539 instruction doesn't work correctly and not to
1540 use it.
1542 no_file_caps Tells the kernel not to honor file capabilities. The
1543 only way then for a file to be executed with privilege
1544 is to be setuid root or executed by root.
1546 nohalt [IA-64] Tells the kernel not to use the power saving
1547 function PAL_HALT_LIGHT when idle. This increases
1548 power-consumption. On the positive side, it reduces
1549 interrupt wake-up latency, which may improve performance
1550 in certain environments such as networked servers or
1551 real-time systems.
1553 nohz= [KNL] Boottime enable/disable dynamic ticks
1554 Valid arguments: on, off
1555 Default: on
1557 noiotrap [SH] Disables trapped I/O port accesses.
1559 noirqdebug [X86-32] Disables the code which attempts to detect and
1560 disable unhandled interrupt sources.
1562 no_timer_check [X86,APIC] Disables the code which tests for
1563 broken timer IRQ sources.
1565 noisapnp [ISAPNP] Disables ISA PnP code.
1567 noinitrd [RAM] Tells the kernel not to load any configured
1568 initial RAM disk.
1570 nointroute [IA-64]
1572 nojitter [IA64] Disables jitter checking for ITC timers.
1574 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1576 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1578 noltlbs [PPC] Do not use large page/tlb entries for kernel
1579 lowmem mapping on PPC40x.
1581 nomca [IA-64] Disable machine check abort handling
1583 nomce [X86-32] Machine Check Exception
1585 nomfgpt [X86-32] Disable Multi-Function General Purpose
1586 Timer usage (for AMD Geode machines).
1588 norandmaps Don't use address space randomization. Equivalent to
1589 echo 0 > /proc/sys/kernel/randomize_va_space
1591 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1593 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1594 with UP alternatives
1596 noresidual [PPC] Don't use residual data on PReP machines.
1598 noresume [SWSUSP] Disables resume and restores original swap
1599 space.
1601 no-scroll [VGA] Disables scrollback.
1602 This is required for the Braillex ib80-piezo Braille
1603 reader made by F.H. Papenmeier (Germany).
1605 nosbagart [IA-64]
1607 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1609 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1610 and disable the IO APIC. legacy for "maxcpus=0".
1612 nosoftlockup [KNL] Disable the soft-lockup detector.
1614 noswapaccount [KNL] Disable accounting of swap in memory resource
1615 controller. (See Documentation/cgroups/memory.txt)
1617 nosync [HW,M68K] Disables sync negotiation for all devices.
1619 notsc [BUGS=X86-32] Disable Time Stamp Counter
1621 nousb [USB] Disable the USB subsystem
1623 nowb [ARM]
1625 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1627 nptcg= [IA64] Override max number of concurrent global TLB
1628 purges which is reported from either PAL_VM_SUMMARY or
1629 SAL PALO.
1631 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1633 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1634 one of ['zone', 'node', 'default'] can be specified
1635 This can be set from sysctl after boot.
1636 See Documentation/sysctl/vm.txt for details.
1638 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1639 See Documentation/debugging-via-ohci1394.txt for more
1640 info.
1642 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1643 Rather than timing out after 20 ms if an EC
1644 command is not properly ACKed, override the length
1645 of the timeout. We have interrupts disabled while
1646 waiting for the ACK, so if this is set too high
1647 interrupts *may* be lost!
1649 opl3= [HW,OSS]
1650 Format: <io>
1652 oprofile.timer= [HW]
1653 Use timer interrupt instead of performance counters
1655 osst= [HW,SCSI] SCSI Tape Driver
1656 Format: <buffer_size>,<write_threshold>
1657 See also Documentation/scsi/st.txt.
1659 panic= [KNL] Kernel behaviour on panic
1660 Format: <timeout>
1662 parkbd.port= [HW] Parallel port number the keyboard adapter is
1663 connected to, default is 0.
1664 Format: <parport#>
1665 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1666 0 for XT, 1 for AT (default is AT).
1667 Format: <mode>
1669 parport= [HW,PPT] Specify parallel ports. 0 disables.
1670 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1671 Use 'auto' to force the driver to use any
1672 IRQ/DMA settings detected (the default is to
1673 ignore detected IRQ/DMA settings because of
1674 possible conflicts). You can specify the base
1675 address, IRQ, and DMA settings; IRQ and DMA
1676 should be numbers, or 'auto' (for using detected
1677 settings on that particular port), or 'nofifo'
1678 (to avoid using a FIFO even if it is detected).
1679 Parallel ports are assigned in the order they
1680 are specified on the command line, starting
1681 with parport0.
1683 parport_init_mode= [HW,PPT]
1684 Configure VIA parallel port to operate in
1685 a specific mode. This is necessary on Pegasos
1686 computer where firmware has no options for setting
1687 up parallel port mode and sets it to spp.
1688 Currently this function knows 686a and 8231 chips.
1689 Format: [spp|ps2|epp|ecp|ecpepp]
1691 pas2= [HW,OSS] Format:
1692 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1694 pas16= [HW,SCSI]
1695 See header of drivers/scsi/pas16.c.
1697 pause_on_oops=
1698 Halt all CPUs after the first oops has been printed for
1699 the specified number of seconds. This is to be used if
1700 your oopses keep scrolling off the screen.
1702 pcbit= [HW,ISDN]
1704 pcd. [PARIDE]
1705 See header of drivers/block/paride/pcd.c.
1706 See also Documentation/blockdev/paride.txt.
1708 pci=option[,option...] [PCI] various PCI subsystem options:
1709 earlydump [X86] dump PCI config space before the kernel
1710 changes anything
1711 off [X86] don't probe for the PCI bus
1712 bios [X86-32] force use of PCI BIOS, don't access
1713 the hardware directly. Use this if your machine
1714 has a non-standard PCI host bridge.
1715 nobios [X86-32] disallow use of PCI BIOS, only direct
1716 hardware access methods are allowed. Use this
1717 if you experience crashes upon bootup and you
1718 suspect they are caused by the BIOS.
1719 conf1 [X86] Force use of PCI Configuration
1720 Mechanism 1.
1721 conf2 [X86] Force use of PCI Configuration
1722 Mechanism 2.
1723 noaer [PCIE] If the PCIEAER kernel config parameter is
1724 enabled, this kernel boot option can be used to
1725 disable the use of PCIE advanced error reporting.
1726 nodomains [PCI] Disable support for multiple PCI
1727 root domains (aka PCI segments, in ACPI-speak).
1728 nommconf [X86] Disable use of MMCONFIG for PCI
1729 Configuration
1730 nomsi [MSI] If the PCI_MSI kernel config parameter is
1731 enabled, this kernel boot option can be used to
1732 disable the use of MSI interrupts system-wide.
1733 noioapicquirk [APIC] Disable all boot interrupt quirks.
1734 Safety option to keep boot IRQs enabled. This
1735 should never be necessary.
1736 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1737 primary IO-APIC for bridges that cannot disable
1738 boot IRQs. This fixes a source of spurious IRQs
1739 when the system masks IRQs.
1740 noioapicreroute [APIC] Disable workaround that uses the
1741 boot IRQ equivalent of an IRQ that connects to
1742 a chipset where boot IRQs cannot be disabled.
1743 The opposite of ioapicreroute.
1744 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1745 routing table. These calls are known to be buggy
1746 on several machines and they hang the machine
1747 when used, but on other computers it's the only
1748 way to get the interrupt routing table. Try
1749 this option if the kernel is unable to allocate
1750 IRQs or discover secondary PCI buses on your
1751 motherboard.
1752 rom [X86] Assign address space to expansion ROMs.
1753 Use with caution as certain devices share
1754 address decoders between ROMs and other
1755 resources.
1756 norom [X86] Do not assign address space to
1757 expansion ROMs that do not already have
1758 BIOS assigned address ranges.
1759 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1760 assigned automatically to PCI devices. You can
1761 make the kernel exclude IRQs of your ISA cards
1762 this way.
1763 pirqaddr=0xAAAAA [X86] Specify the physical address
1764 of the PIRQ table (normally generated
1765 by the BIOS) if it is outside the
1766 F0000h-100000h range.
1767 lastbus=N [X86] Scan all buses thru bus #N. Can be
1768 useful if the kernel is unable to find your
1769 secondary buses and you want to tell it
1770 explicitly which ones they are.
1771 assign-busses [X86] Always assign all PCI bus
1772 numbers ourselves, overriding
1773 whatever the firmware may have done.
1774 usepirqmask [X86] Honor the possible IRQ mask stored
1775 in the BIOS $PIR table. This is needed on
1776 some systems with broken BIOSes, notably
1777 some HP Pavilion N5400 and Omnibook XE3
1778 notebooks. This will have no effect if ACPI
1779 IRQ routing is enabled.
1780 noacpi [X86] Do not use ACPI for IRQ routing
1781 or for PCI scanning.
1782 use_crs [X86] Use _CRS for PCI resource
1783 allocation.
1784 routeirq Do IRQ routing for all PCI devices.
1785 This is normally done in pci_enable_device(),
1786 so this option is a temporary workaround
1787 for broken drivers that don't call it.
1788 skip_isa_align [X86] do not align io start addr, so can
1789 handle more pci cards
1790 firmware [ARM] Do not re-enumerate the bus but instead
1791 just use the configuration from the
1792 bootloader. This is currently used on
1793 IXP2000 systems where the bus has to be
1794 configured a certain way for adjunct CPUs.
1795 noearly [X86] Don't do any early type 1 scanning.
1796 This might help on some broken boards which
1797 machine check when some devices' config space
1798 is read. But various workarounds are disabled
1799 and some IOMMU drivers will not work.
1800 bfsort Sort PCI devices into breadth-first order.
1801 This sorting is done to get a device
1802 order compatible with older (<= 2.4) kernels.
1803 nobfsort Don't sort PCI devices into breadth-first order.
1804 cbiosize=nn[KMG] The fixed amount of bus space which is
1805 reserved for the CardBus bridge's IO window.
1806 The default value is 256 bytes.
1807 cbmemsize=nn[KMG] The fixed amount of bus space which is
1808 reserved for the CardBus bridge's memory
1809 window. The default value is 64 megabytes.
1810 resource_alignment=
1811 Format:
1812 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1813 Specifies alignment and device to reassign
1814 aligned memory resources.
1815 If <order of align> is not specified,
1816 PAGE_SIZE is used as alignment.
1817 PCI-PCI bridge can be specified, if resource
1818 windows need to be expanded.
1820 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1821 Management.
1822 off Disable ASPM.
1823 force Enable ASPM even on devices that claim not to support it.
1824 WARNING: Forcing ASPM on may cause system lockups.
1826 pcmv= [HW,PCMCIA] BadgePAD 4
1828 pd. [PARIDE]
1829 See Documentation/blockdev/paride.txt.
1831 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1832 boot time.
1833 Format: { 0 | 1 }
1834 See arch/parisc/kernel/pdc_chassis.c
1836 pf. [PARIDE]
1837 See Documentation/blockdev/paride.txt.
1839 pg. [PARIDE]
1840 See Documentation/blockdev/paride.txt.
1842 pirq= [SMP,APIC] Manual mp-table setup
1843 See Documentation/x86/i386/IO-APIC.txt.
1845 plip= [PPT,NET] Parallel port network link
1846 Format: { parport<nr> | timid | 0 }
1847 See also Documentation/parport.txt.
1849 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1850 Override pmtimer IOPort with a hex value.
1851 e.g. pmtmr=0x508
1853 pnp.debug [PNP]
1854 Enable PNP debug messages. This depends on the
1855 CONFIG_PNP_DEBUG_MESSAGES option.
1857 pnpacpi= [ACPI]
1858 { off }
1860 pnpbios= [ISAPNP]
1861 { on | off | curr | res | no-curr | no-res }
1863 pnp_reserve_irq=
1864 [ISAPNP] Exclude IRQs for the autoconfiguration
1866 pnp_reserve_dma=
1867 [ISAPNP] Exclude DMAs for the autoconfiguration
1869 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1870 Ranges are in pairs (I/O port base and size).
1872 pnp_reserve_mem=
1873 [ISAPNP] Exclude memory regions for the
1874 autoconfiguration.
1875 Ranges are in pairs (memory base and size).
1877 ports= [IP_VS_FTP] IPVS ftp helper module
1878 Default is 21.
1879 Up to 8 (IP_VS_APP_MAX_PORTS) ports
1880 may be specified.
1881 Format: <port>,<port>....
1883 print-fatal-signals=
1884 [KNL] debug: print fatal signals
1885 print-fatal-signals=1: print segfault info to
1886 the kernel console.
1887 default: off.
1889 printk.time= Show timing data prefixed to each printk message line
1890 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1892 processor.max_cstate= [HW,ACPI]
1893 Limit processor to maximum C-state
1894 max_cstate=9 overrides any DMI blacklist limit.
1896 processor.nocst [HW,ACPI]
1897 Ignore the _CST method to determine C-states,
1898 instead using the legacy FADT method
1900 profile= [KNL] Enable kernel profiling via /proc/profile
1901 Format: [schedule,]<number>
1902 Param: "schedule" - profile schedule points.
1903 Param: <number> - step/bucket size as a power of 2 for
1904 statistical time based profiling.
1905 Param: "sleep" - profile D-state sleeping (millisecs).
1906 Requires CONFIG_SCHEDSTATS
1907 Param: "kvm" - profile VM exits.
1909 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1910 before loading.
1911 See Documentation/blockdev/ramdisk.txt.
1913 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1914 probe for; one of (bare|imps|exps|lifebook|any).
1915 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1916 per second.
1917 psmouse.resetafter= [HW,MOUSE]
1918 Try to reset the device after so many bad packets
1919 (0 = never).
1920 psmouse.resolution=
1921 [HW,MOUSE] Set desired mouse resolution, in dpi.
1922 psmouse.smartscroll=
1923 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1924 0 = disabled, 1 = enabled (default).
1926 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1927 Format:
1928 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1930 pt. [PARIDE]
1931 See Documentation/blockdev/paride.txt.
1933 pty.legacy_count=
1934 [KNL] Number of legacy pty's. Overwrites compiled-in
1935 default number.
1937 quiet [KNL] Disable most log messages
1939 r128= [HW,DRM]
1941 raid= [HW,RAID]
1942 See Documentation/md.txt.
1944 ramdisk_blocksize= [RAM]
1945 See Documentation/blockdev/ramdisk.txt.
1947 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1948 See Documentation/blockdev/ramdisk.txt.
1950 rcupdate.blimit= [KNL,BOOT]
1951 Set maximum number of finished RCU callbacks to process
1952 in one batch.
1954 rcupdate.qhimark= [KNL,BOOT]
1955 Set threshold of queued
1956 RCU callbacks over which batch limiting is disabled.
1958 rcupdate.qlowmark= [KNL,BOOT]
1959 Set threshold of queued RCU callbacks below which
1960 batch limiting is re-enabled.
1962 rdinit= [KNL]
1963 Format: <full_path>
1964 Run specified binary instead of /init from the ramdisk,
1965 used for early userspace startup. See initrd.
1967 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1968 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1969 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1971 relax_domain_level=
1972 [KNL, SMP] Set scheduler's default relax_domain_level.
1973 See Documentation/cgroups/cpusets.txt.
1975 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1977 reservetop= [X86-32]
1978 Format: nn[KMG]
1979 Reserves a hole at the top of the kernel virtual
1980 address space.
1982 reset_devices [KNL] Force drivers to reset the underlying device
1983 during initialization.
1985 resume= [SWSUSP]
1986 Specify the partition device for software suspend
1988 resume_offset= [SWSUSP]
1989 Specify the offset from the beginning of the partition
1990 given by "resume=" at which the swap header is located,
1991 in <PAGE_SIZE> units (needed only for swap files).
1992 See Documentation/power/swsusp-and-swap-files.txt
1994 retain_initrd [RAM] Keep initrd memory after extraction
1996 rhash_entries= [KNL,NET]
1997 Set number of hash buckets for route cache
1999 riscom8= [HW,SERIAL]
2000 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2002 ro [KNL] Mount root device read-only on boot
2004 root= [KNL] Root filesystem
2006 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2007 mount the root filesystem
2009 rootflags= [KNL] Set root filesystem mount option string
2011 rootfstype= [KNL] Set root filesystem type
2013 rootwait [KNL] Wait (indefinitely) for root device to show up.
2014 Useful for devices that are detected asynchronously
2015 (e.g. USB and MMC devices).
2017 root_plug.vendor_id=
2018 [ROOTPLUG] Override the default vendor ID
2020 root_plug.product_id=
2021 [ROOTPLUG] Override the default product ID
2023 root_plug.debug=
2024 [ROOTPLUG] Enable debugging output
2026 rw [KNL] Mount root device read-write on boot
2028 S [KNL] Run init in single mode
2030 sa1100ir [NET]
2031 See drivers/net/irda/sa1100_ir.c.
2033 sbni= [NET] Granch SBNI12 leased line adapter
2035 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2036 Format: <io>[,<timeout>[,<isapnp>]]
2038 scsi_debug_*= [SCSI]
2039 See drivers/scsi/scsi_debug.c.
2041 scsi_default_dev_flags=
2042 [SCSI] SCSI default device flags
2043 Format: <integer>
2045 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2046 Format: <vendor>:<model>:<flags>
2047 (flags are integer value)
2049 scsi_logging_level= [SCSI] a bit mask of logging levels
2050 See drivers/scsi/scsi_logging.h for bits. Also
2051 settable via sysctl at dev.scsi.logging_level
2052 (/proc/sys/dev/scsi/logging_level).
2053 There is also a nice 'scsi_logging_level' script in the
2054 S390-tools package, available for download at
2055 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2057 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2058 discovered. async scans them in kernel threads,
2059 allowing boot to proceed. none ignores them, expecting
2060 user space to do the scan.
2062 security= [SECURITY] Choose a security module to enable at boot.
2063 If this boot parameter is not specified, only the first
2064 security module asking for security registration will be
2065 loaded. An invalid security module name will be treated
2066 as if no module has been chosen.
2068 selinux= [SELINUX] Disable or enable SELinux at boot time.
2069 Format: { "0" | "1" }
2070 See security/selinux/Kconfig help text.
2071 0 -- disable.
2072 1 -- enable.
2073 Default value is set via kernel config option.
2074 If enabled at boot time, /selinux/disable can be used
2075 later to disable prior to initial policy load.
2077 serialnumber [BUGS=X86-32]
2079 shapers= [NET]
2080 Maximal number of shapers.
2082 show_msr= [x86] show boot-time MSR settings
2083 Format: { <integer> }
2084 Show boot-time (BIOS-initialized) MSR settings.
2085 The parameter means the number of CPUs to show,
2086 for example 1 means boot CPU only.
2088 sim710= [SCSI,HW]
2089 See header of drivers/scsi/sim710.c.
2091 simeth= [IA-64]
2092 simscsi=
2094 slram= [HW,MTD]
2096 slub_debug[=options[,slabs]] [MM, SLUB]
2097 Enabling slub_debug allows one to determine the
2098 culprit if slab objects become corrupted. Enabling
2099 slub_debug can create guard zones around objects and
2100 may poison objects when not in use. Also tracks the
2101 last alloc / free. For more information see
2102 Documentation/vm/slub.txt.
2104 slub_max_order= [MM, SLUB]
2105 Determines the maximum allowed order for slabs.
2106 A high setting may cause OOMs due to memory
2107 fragmentation. For more information see
2108 Documentation/vm/slub.txt.
2110 slub_min_objects= [MM, SLUB]
2111 The minimum number of objects per slab. SLUB will
2112 increase the slab order up to slub_max_order to
2113 generate a sufficiently large slab able to contain
2114 the number of objects indicated. The higher the number
2115 of objects the smaller the overhead of tracking slabs
2116 and the less frequently locks need to be acquired.
2117 For more information see Documentation/vm/slub.txt.
2119 slub_min_order= [MM, SLUB]
2120 Determines the mininum page order for slabs. Must be
2121 lower than slub_max_order.
2122 For more information see Documentation/vm/slub.txt.
2124 slub_nomerge [MM, SLUB]
2125 Disable merging of slabs with similar size. May be
2126 necessary if there is some reason to distinguish
2127 allocs to different slabs. Debug options disable
2128 merging on their own.
2129 For more information see Documentation/vm/slub.txt.
2131 smart2= [HW]
2132 Format: <io1>[,<io2>[,...,<io8>]]
2134 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2135 attempt to substitute SMP alternatives once at boot.
2137 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2138 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2139 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2140 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2141 smsc-ircc2.ircc_irq= [HW] IRQ line
2142 smsc-ircc2.ircc_dma= [HW] DMA channel
2143 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2144 0: Toshiba Satellite 1800 (GP data pin select)
2145 1: Fast pin select (default)
2146 2: ATC IRMode
2148 snd-ad1816a= [HW,ALSA]
2150 snd-ad1848= [HW,ALSA]
2152 snd-ali5451= [HW,ALSA]
2154 snd-als100= [HW,ALSA]
2156 snd-als4000= [HW,ALSA]
2158 snd-azt2320= [HW,ALSA]
2160 snd-cmi8330= [HW,ALSA]
2162 snd-cmipci= [HW,ALSA]
2164 snd-cs4231= [HW,ALSA]
2166 snd-cs4232= [HW,ALSA]
2168 snd-cs4236= [HW,ALSA]
2170 snd-cs4281= [HW,ALSA]
2172 snd-cs46xx= [HW,ALSA]
2174 snd-dt019x= [HW,ALSA]
2176 snd-dummy= [HW,ALSA]
2178 snd-emu10k1= [HW,ALSA]
2180 snd-ens1370= [HW,ALSA]
2182 snd-ens1371= [HW,ALSA]
2184 snd-es968= [HW,ALSA]
2186 snd-es1688= [HW,ALSA]
2188 snd-es18xx= [HW,ALSA]
2190 snd-es1938= [HW,ALSA]
2192 snd-es1968= [HW,ALSA]
2194 snd-fm801= [HW,ALSA]
2196 snd-gusclassic= [HW,ALSA]
2198 snd-gusextreme= [HW,ALSA]
2200 snd-gusmax= [HW,ALSA]
2202 snd-hdsp= [HW,ALSA]
2204 snd-ice1712= [HW,ALSA]
2206 snd-intel8x0= [HW,ALSA]
2208 snd-interwave= [HW,ALSA]
2210 snd-interwave-stb=
2211 [HW,ALSA]
2213 snd-korg1212= [HW,ALSA]
2215 snd-maestro3= [HW,ALSA]
2217 snd-mpu401= [HW,ALSA]
2219 snd-mtpav= [HW,ALSA]
2221 snd-nm256= [HW,ALSA]
2223 snd-opl3sa2= [HW,ALSA]
2225 snd-opti92x-ad1848=
2226 [HW,ALSA]
2228 snd-opti92x-cs4231=
2229 [HW,ALSA]
2231 snd-opti93x= [HW,ALSA]
2233 snd-pmac= [HW,ALSA]
2235 snd-rme32= [HW,ALSA]
2237 snd-rme96= [HW,ALSA]
2239 snd-rme9652= [HW,ALSA]
2241 snd-sb8= [HW,ALSA]
2243 snd-sb16= [HW,ALSA]
2245 snd-sbawe= [HW,ALSA]
2247 snd-serial= [HW,ALSA]
2249 snd-sgalaxy= [HW,ALSA]
2251 snd-sonicvibes= [HW,ALSA]
2253 snd-sun-amd7930=
2254 [HW,ALSA]
2256 snd-sun-cs4231= [HW,ALSA]
2258 snd-trident= [HW,ALSA]
2260 snd-usb-audio= [HW,ALSA,USB]
2262 snd-via82xx= [HW,ALSA]
2264 snd-virmidi= [HW,ALSA]
2266 snd-wavefront= [HW,ALSA]
2268 snd-ymfpci= [HW,ALSA]
2270 softlockup_panic=
2271 [KNL] Should the soft-lockup detector generate panics.
2273 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2274 See Documentation/sonypi.txt
2276 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2277 See Documentation/serial/specialix.txt.
2279 spia_io_base= [HW,MTD]
2280 spia_fio_base=
2281 spia_pedr=
2282 spia_peddr=
2284 sscape= [HW,OSS]
2285 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2287 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2288 See Documentation/scsi/st.txt.
2290 stacktrace [FTRACE]
2291 Enabled the stack tracer on boot up.
2293 sti= [PARISC,HW]
2294 Format: <num>
2295 Set the STI (builtin display/keyboard on the HP-PARISC
2296 machines) console (graphic card) which should be used
2297 as the initial boot-console.
2298 See also comment in drivers/video/console/sticore.c.
2300 sti_font= [HW]
2301 See comment in drivers/video/console/sticore.c.
2303 stifb= [HW]
2304 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2306 sunrpc.pool_mode=
2307 [NFS]
2308 Control how the NFS server code allocates CPUs to
2309 service thread pools. Depending on how many NICs
2310 you have and where their interrupts are bound, this
2311 option will affect which CPUs will do NFS serving.
2312 Note: this parameter cannot be changed while the
2313 NFS server is running.
2315 auto the server chooses an appropriate mode
2316 automatically using heuristics
2317 global a single global pool contains all CPUs
2318 percpu one pool for each CPU
2319 pernode one pool for each NUMA node (equivalent
2320 to global on non-NUMA machines)
2322 swiotlb= [IA-64] Number of I/O TLB slabs
2324 switches= [HW,M68k]
2326 sym53c416= [HW,SCSI]
2327 See header of drivers/scsi/sym53c416.c.
2329 sysrq_always_enabled
2330 [KNL]
2331 Ignore sysrq setting - this boot parameter will
2332 neutralize any effect of /proc/sys/kernel/sysrq.
2333 Useful for debugging.
2335 t128= [HW,SCSI]
2336 See header of drivers/scsi/t128.c.
2338 tdfx= [HW,DRM]
2340 test_suspend= [SUSPEND]
2341 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2342 standby suspend) as the system sleep state to briefly
2343 enter during system startup. The system is woken from
2344 this state using a wakeup-capable RTC alarm.
2346 thash_entries= [KNL,NET]
2347 Set number of hash buckets for TCP connection
2349 thermal.act= [HW,ACPI]
2350 -1: disable all active trip points in all thermal zones
2351 <degrees C>: override all lowest active trip points
2353 thermal.crt= [HW,ACPI]
2354 -1: disable all critical trip points in all thermal zones
2355 <degrees C>: override all critical trip points
2357 thermal.nocrt= [HW,ACPI]
2358 Set to disable actions on ACPI thermal zone
2359 critical and hot trip points.
2361 thermal.off= [HW,ACPI]
2362 1: disable ACPI thermal control
2364 thermal.psv= [HW,ACPI]
2365 -1: disable all passive trip points
2366 <degrees C>: override all passive trip points to this
2367 value
2369 thermal.tzp= [HW,ACPI]
2370 Specify global default ACPI thermal zone polling rate
2371 <deci-seconds>: poll all this frequency
2372 0: no polling (default)
2374 tmscsim= [HW,SCSI]
2375 See comment before function dc390_setup() in
2376 drivers/scsi/tmscsim.c.
2378 topology= [S390]
2379 Format: {off | on}
2380 Specify if the kernel should make use of the cpu
2381 topology informations if the hardware supports these.
2382 The scheduler will make use of these informations and
2383 e.g. base its process migration decisions on it.
2384 Default is off.
2386 tp720= [HW,PS2]
2388 trace_buf_size=nn[KMG] [ftrace] will set tracing buffer size.
2390 trix= [HW,OSS] MediaTrix AudioTrix Pro
2391 Format:
2392 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2394 tsc= Disable clocksource-must-verify flag for TSC.
2395 Format: <string>
2396 [x86] reliable: mark tsc clocksource as reliable, this
2397 disables clocksource verification at runtime.
2398 Used to enable high-resolution timer mode on older
2399 hardware, and in virtualized environment.
2401 turbografx.map[2|3]= [HW,JOY]
2402 TurboGraFX parallel port interface
2403 Format:
2404 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2405 See also Documentation/input/joystick-parport.txt
2407 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2408 See header of drivers/scsi/u14-34f.c.
2410 uart401= [HW,OSS]
2411 Format: <io>,<irq>
2413 uart6850= [HW,OSS]
2414 Format: <io>,<irq>
2416 uhci-hcd.ignore_oc=
2417 [USB] Ignore overcurrent events (default N).
2418 Some badly-designed motherboards generate lots of
2419 bogus events, for ports that aren't wired to
2420 anything. Set this parameter to avoid log spamming.
2421 Note that genuine overcurrent events won't be
2422 reported either.
2424 unknown_nmi_panic
2425 [X86]
2426 Set unknown_nmi_panic=1 early on boot.
2428 usbcore.autosuspend=
2429 [USB] The autosuspend time delay (in seconds) used
2430 for newly-detected USB devices (default 2). This
2431 is the time required before an idle device will be
2432 autosuspended. Devices for which the delay is set
2433 to a negative value won't be autosuspended at all.
2435 usbcore.usbfs_snoop=
2436 [USB] Set to log all usbfs traffic (default 0 = off).
2438 usbcore.blinkenlights=
2439 [USB] Set to cycle leds on hubs (default 0 = off).
2441 usbcore.old_scheme_first=
2442 [USB] Start with the old device initialization
2443 scheme (default 0 = off).
2445 usbcore.use_both_schemes=
2446 [USB] Try the other device initialization scheme
2447 if the first one fails (default 1 = enabled).
2449 usbcore.initial_descriptor_timeout=
2450 [USB] Specifies timeout for the initial 64-byte
2451 USB_REQ_GET_DESCRIPTOR request in milliseconds
2452 (default 5000 = 5.0 seconds).
2454 usbhid.mousepoll=
2455 [USBHID] The interval which mice are to be polled at.
2457 usb-storage.delay_use=
2458 [UMS] The delay in seconds before a new device is
2459 scanned for Logical Units (default 5).
2461 usb-storage.quirks=
2462 [UMS] A list of quirks entries to supplement or
2463 override the built-in unusual_devs list. List
2464 entries are separated by commas. Each entry has
2465 the form VID:PID:Flags where VID and PID are Vendor
2466 and Product ID values (4-digit hex numbers) and
2467 Flags is a set of characters, each corresponding
2468 to a common usb-storage quirk flag as follows:
2469 a = SANE_SENSE (collect more than 18 bytes
2470 of sense data);
2471 c = FIX_CAPACITY (decrease the reported
2472 device capacity by one sector);
2473 h = CAPACITY_HEURISTICS (decrease the
2474 reported device capacity by one
2475 sector if the number is odd);
2476 i = IGNORE_DEVICE (don't bind to this
2477 device);
2478 l = NOT_LOCKABLE (don't try to lock and
2479 unlock ejectable media);
2480 m = MAX_SECTORS_64 (don't transfer more
2481 than 64 sectors = 32 KB at a time);
2482 o = CAPACITY_OK (accept the capacity
2483 reported by the device);
2484 r = IGNORE_RESIDUE (the device reports
2485 bogus residue values);
2486 s = SINGLE_LUN (the device has only one
2487 Logical Unit);
2488 w = NO_WP_DETECT (don't test whether the
2489 medium is write-protected).
2490 Example: quirks=0419:aaf5:rl,0421:0433:rc
2492 vdso= [X86,SH]
2493 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2494 vdso=1: enable VDSO (default)
2495 vdso=0: disable VDSO mapping
2497 vdso32= [X86]
2498 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2499 vdso32=1: enable 32-bit VDSO (default)
2500 vdso32=0: disable 32-bit VDSO mapping
2502 vector= [IA-64,SMP]
2503 vector=percpu: enable percpu vector domain
2505 video= [FB] Frame buffer configuration
2506 See Documentation/fb/modedb.txt.
2508 vga= [BOOT,X86-32] Select a particular video mode
2509 See Documentation/x86/boot.txt and
2510 Documentation/svga.txt.
2511 Use vga=ask for menu.
2512 This is actually a boot loader parameter; the value is
2513 passed to the kernel using a special protocol.
2515 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2516 size of <nn>. This can be used to increase the
2517 minimum size (128MB on x86). It can also be used to
2518 decrease the size and leave more room for directly
2519 mapped kernel RAM.
2521 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2522 Format: <command>
2524 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2525 Format: <command>
2527 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2528 Format: <command>
2530 vt.default_blu= [VT]
2531 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2532 Change the default blue palette of the console.
2533 This is a 16-member array composed of values
2534 ranging from 0-255.
2536 vt.default_grn= [VT]
2537 Format: <green0>,<green1>,<green2>,...,<green15>
2538 Change the default green palette of the console.
2539 This is a 16-member array composed of values
2540 ranging from 0-255.
2542 vt.default_red= [VT]
2543 Format: <red0>,<red1>,<red2>,...,<red15>
2544 Change the default red palette of the console.
2545 This is a 16-member array composed of values
2546 ranging from 0-255.
2548 vt.default_utf8=
2549 [VT]
2550 Format=<0|1>
2551 Set system-wide default UTF-8 mode for all tty's.
2552 Default is 1, i.e. UTF-8 mode is enabled for all
2553 newly opened terminals.
2555 waveartist= [HW,OSS]
2556 Format: <io>,<irq>,<dma>,<dma2>
2558 wd33c93= [HW,SCSI]
2559 See header of drivers/scsi/wd33c93.c.
2561 wd7000= [HW,SCSI]
2562 See header of drivers/scsi/wd7000.c.
2564 wdt= [WDT] Watchdog
2565 See Documentation/watchdog/wdt.txt.
2567 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2568 default x2apic cluster mode on platforms
2569 supporting x2apic.
2571 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2572 xd_geo= See header of drivers/block/xd.c.
2574 xirc2ps_cs= [NET,PCMCIA]
2575 Format:
2576 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2578 ______________________________________________________________________
2580 TODO:
2582 Add documentation for ALSA options.
2583 Add more DRM drivers.