| blob | d9a24a04cfb1720515f7809d6cbcd3aef084bb29 |
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.power_nocheck= [HW,ACPI]
233 Format: 1/0 enable/disable the check of power state.
234 On some bogus BIOS the _PSC object/_STA object of
235 power resource can't return the correct device power
236 state. In such case it is unneccessary to check its
237 power state again in power transition.
238 1 : disable the power state check
240 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
241 Format: { level | edge | high | low }
243 acpi_serialize [HW,ACPI] force serialization of AML methods
245 acpi_skip_timer_override [HW,ACPI]
246 Recognize and ignore IRQ0/pin2 Interrupt Override.
247 For broken nForce2 BIOS resulting in XT-PIC timer.
249 acpi_sleep= [HW,ACPI] Sleep options
250 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
251 old_ordering, s4_nonvs }
252 See Documentation/power/video.txt for information on
253 s3_bios and s3_mode.
254 s3_beep is for debugging; it makes the PC's speaker beep
255 as soon as the kernel's real-mode entry point is called.
256 s4_nohwsig prevents ACPI hardware signature from being
257 used during resume from hibernation.
258 old_ordering causes the ACPI 1.0 ordering of the _PTS
259 control method, with respect to putting devices into
260 low power states, to be enforced (the ACPI 2.0 ordering
261 of _PTS is used by default).
262 s4_nonvs prevents the kernel from saving/restoring the
263 ACPI NVS memory during hibernation.
265 acpi_use_timer_override [HW,ACPI]
266 Use timer override. For some broken Nvidia NF5 boards
267 that require a timer override, but don't have HPET
269 acpi_enforce_resources= [ACPI]
270 { strict | lax | no }
271 Check for resource conflicts between native drivers
272 and ACPI OperationRegions (SystemIO and SystemMemory
273 only). IO ports and memory declared in ACPI might be
274 used by the ACPI subsystem in arbitrary AML code and
275 can interfere with legacy drivers.
276 strict (default): access to resources claimed by ACPI
277 is denied; legacy drivers trying to access reserved
278 resources will fail to bind to device using them.
279 lax: access to resources claimed by ACPI is allowed;
280 legacy drivers trying to access reserved resources
281 will bind successfully but a warning message is logged.
282 no: ACPI OperationRegions are not marked as reserved,
283 no further checks are performed.
285 ad1848= [HW,OSS]
286 Format: <io>,<irq>,<dma>,<dma2>,<type>
288 add_efi_memmap [EFI; X86] Include EFI memory map in
289 kernel's map of available physical RAM.
291 advansys= [HW,SCSI]
292 See header of drivers/scsi/advansys.c.
294 advwdt= [HW,WDT] Advantech WDT
295 Format: <iostart>,<iostop>
297 aedsp16= [HW,OSS] Audio Excel DSP 16
298 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
299 See also header of sound/oss/aedsp16.c.
301 agp= [AGP]
302 { off | try_unsupported }
303 off: disable AGP support
304 try_unsupported: try to drive unsupported chipsets
305 (may crash computer or cause data corruption)
307 aha152x= [HW,SCSI]
308 See Documentation/scsi/aha152x.txt.
310 aha1542= [HW,SCSI]
311 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
313 aic7xxx= [HW,SCSI]
314 See Documentation/scsi/aic7xxx.txt.
316 aic79xx= [HW,SCSI]
317 See Documentation/scsi/aic79xx.txt.
319 amd_iommu= [HW,X86-84]
320 Pass parameters to the AMD IOMMU driver in the system.
321 Possible values are:
322 isolate - enable device isolation (each device, as far
323 as possible, will get its own protection
324 domain) [default]
325 share - put every device behind one IOMMU into the
326 same protection domain
327 fullflush - enable flushing of IO/TLB entries when
328 they are unmapped. Otherwise they are
329 flushed before they will be reused, which
330 is a lot of faster
332 amd_iommu_size= [HW,X86-64]
333 Define the size of the aperture for the AMD IOMMU
334 driver. Possible values are:
335 '32M', '64M' (default), '128M', '256M', '512M', '1G'
337 amijoy.map= [HW,JOY] Amiga joystick support
338 Map of devices attached to JOY0DAT and JOY1DAT
339 Format: <a>,<b>
340 See also Documentation/kernel/input/joystick.txt
342 analog.map= [HW,JOY] Analog joystick and gamepad support
343 Specifies type or capabilities of an analog joystick
344 connected to one of 16 gameports
345 Format: <type1>,<type2>,..<type16>
347 apc= [HW,SPARC]
348 Power management functions (SPARCstation-4/5 + deriv.)
349 Format: noidle
350 Disable APC CPU standby support. SPARCstation-Fox does
351 not play well with APC CPU idle - disable it if you have
352 APC and your system crashes randomly.
354 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
355 Change the output verbosity whilst booting
356 Format: { quiet (default) | verbose | debug }
357 Change the amount of debugging information output
358 when initialising the APIC and IO-APIC components.
360 apm= [APM] Advanced Power Management
361 See header of arch/x86/kernel/apm_32.c.
363 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
364 Format: <io>,<irq>,<nodeID>
366 ataflop= [HW,M68k]
368 atarimouse= [HW,MOUSE] Atari Mouse
370 atascsi= [HW,SCSI] Atari SCSI
372 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
373 EzKey and similar keyboards
375 atkbd.reset= [HW] Reset keyboard during initialization
377 atkbd.set= [HW] Select keyboard code set
378 Format: <int> (2 = AT (default), 3 = PS/2)
380 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
381 keyboards
383 atkbd.softraw= [HW] Choose between synthetic and real raw mode
384 Format: <bool> (0 = real, 1 = synthetic (default))
386 atkbd.softrepeat= [HW]
387 Use software keyboard repeat
389 autotest [IA64]
391 baycom_epp= [HW,AX25]
392 Format: <io>,<mode>
394 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
395 Format: <io>,<mode>
396 See header of drivers/net/hamradio/baycom_par.c.
398 baycom_ser_fdx= [HW,AX25]
399 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
400 Format: <io>,<irq>,<mode>[,<baud>]
401 See header of drivers/net/hamradio/baycom_ser_fdx.c.
403 baycom_ser_hdx= [HW,AX25]
404 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
405 Format: <io>,<irq>,<mode>
406 See header of drivers/net/hamradio/baycom_ser_hdx.c.
408 boot_delay= Milliseconds to delay each printk during boot.
409 Values larger than 10 seconds (10000) are changed to
410 no delay (0).
411 Format: integer
413 bootmem_debug [KNL] Enable bootmem allocator debug messages.
415 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
416 bttv.radio= Most important insmod options are available as
417 kernel args too.
418 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
419 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
421 BusLogic= [HW,SCSI]
422 See drivers/scsi/BusLogic.c, comment before function
423 BusLogic_ParseDriverOptions().
425 c101= [NET] Moxa C101 synchronous serial card
427 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
428 Sometimes CPU hardware bugs make them report the cache
429 size incorrectly. The kernel will attempt work arounds
430 to fix known problems, but for some CPUs it is not
431 possible to determine what the correct size should be.
432 This option provides an override for these situations.
434 capability.disable=
435 [SECURITY] Disable capabilities. This would normally
436 be used only if an alternative security model is to be
437 configured. Potentially dangerous and should only be
438 used if you are entirely sure of the consequences.
440 ccw_timeout_log [S390]
441 See Documentation/s390/CommonIO for details.
443 cgroup_disable= [KNL] Disable a particular controller
444 Format: {name of the controller(s) to disable}
445 {Currently supported controllers - "memory"}
447 checkreqprot [SELINUX] Set initial checkreqprot flag value.
448 Format: { "0" | "1" }
449 See security/selinux/Kconfig help text.
450 0 -- check protection applied by kernel (includes
451 any implied execute protection).
452 1 -- check protection requested by application.
453 Default value is set via a kernel config option.
454 Value can be changed at runtime via
455 /selinux/checkreqprot.
457 cio_ignore= [S390]
458 See Documentation/s390/CommonIO for details.
460 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
461 [Deprecated]
462 Forces specified clocksource (if available) to be used
463 when calculating gettimeofday(). If specified
464 clocksource is not available, it defaults to PIT.
465 Format: { pit | tsc | cyclone | pmtmr }
467 clocksource= [GENERIC_TIME] Override the default clocksource
468 Format: <string>
469 Override the default clocksource and use the clocksource
470 with the name specified.
471 Some clocksource names to choose from, depending on
472 the platform:
473 [all] jiffies (this is the base, fallback clocksource)
474 [ACPI] acpi_pm
475 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
476 pxa_timer,timer3,32k_counter,timer0_1
477 [AVR32] avr32
478 [X86-32] pit,hpet,tsc,vmi-timer;
479 scx200_hrt on Geode; cyclone on IBM x440
480 [MIPS] MIPS
481 [PARISC] cr16
482 [S390] tod
483 [SH] SuperH
484 [SPARC64] tick
485 [X86-64] hpet,tsc
487 clearcpuid=BITNUM [X86]
488 Disable CPUID feature X for the kernel. See
489 arch/x86/include/asm/cpufeature.h for the valid bit
490 numbers. Note the Linux specific bits are not necessarily
491 stable over kernel options, but the vendor specific
492 ones should be.
493 Also note that user programs calling CPUID directly
494 or using the feature without checking anything
495 will still see it. This just prevents it from
496 being used by the kernel or shown in /proc/cpuinfo.
497 Also note the kernel might malfunction if you disable
498 some critical bits.
500 code_bytes [X86] How many bytes of object code to print
501 in an oops report.
502 Range: 0 - 8192
503 Default: 64
505 com20020= [HW,NET] ARCnet - COM20020 chipset
506 Format:
507 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
509 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
510 Format: <io>[,<irq>]
512 com90xx= [HW,NET]
513 ARCnet - COM90xx chipset (memory-mapped buffers)
514 Format: <io>[,<irq>[,<memstart>]]
516 condev= [HW,S390] console device
517 conmode=
519 console= [KNL] Output console device and options.
521 tty<n> Use the virtual console device <n>.
523 ttyS<n>[,options]
524 ttyUSB0[,options]
525 Use the specified serial port. The options are of
526 the form "bbbbpnf", where "bbbb" is the baud rate,
527 "p" is parity ("n", "o", or "e"), "n" is number of
528 bits, and "f" is flow control ("r" for RTS or
529 omit it). Default is "9600n8".
531 See Documentation/serial-console.txt for more
532 information. See
533 Documentation/networking/netconsole.txt for an
534 alternative.
536 uart[8250],io,<addr>[,options]
537 uart[8250],mmio,<addr>[,options]
538 Start an early, polled-mode console on the 8250/16550
539 UART at the specified I/O port or MMIO address,
540 switching to the matching ttyS device later. The
541 options are the same as for ttyS, above.
543 If the device connected to the port is not a TTY but a braille
544 device, prepend "brl," before the device type, for instance
545 console=brl,ttyS0
546 For now, only VisioBraille is supported.
548 coredump_filter=
549 [KNL] Change the default value for
550 /proc/<pid>/coredump_filter.
551 See also Documentation/filesystems/proc.txt.
553 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
554 Format:
555 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
557 crashkernel=nn[KMG]@ss[KMG]
558 [KNL] Reserve a chunk of physical memory to
559 hold a kernel to switch to with kexec on panic.
561 crashkernel=range1:size1[,range2:size2,...][@offset]
562 [KNL] Same as above, but depends on the memory
563 in the running system. The syntax of range is
564 start-[end] where start and end are both
565 a memory unit (amount[KMG]). See also
566 Documentation/kdump/kdump.txt for a example.
568 cs89x0_dma= [HW,NET]
569 Format: <dma>
571 cs89x0_media= [HW,NET]
572 Format: { rj45 | aui | bnc }
574 dasd= [HW,NET]
575 See header of drivers/s390/block/dasd_devmap.c.
577 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
578 (one device per port)
579 Format: <port#>,<type>
580 See also Documentation/input/joystick-parport.txt
582 debug [KNL] Enable kernel debugging (events log level).
584 debug_locks_verbose=
585 [KNL] verbose self-tests
586 Format=<0|1>
587 Print debugging info while doing the locking API
588 self-tests.
589 We default to 0 (no extra messages), setting it to
590 1 will print _a lot_ more information - normally
591 only useful to kernel developers.
593 debug_objects [KNL] Enable object debugging
595 no_debug_objects
596 [KNL] Disable object debugging
598 debugpat [X86] Enable PAT debugging
600 decnet.addr= [HW,NET]
601 Format: <area>[,<node>]
602 See also Documentation/networking/decnet.txt.
604 default_hugepagesz=
605 [same as hugepagesz=] The size of the default
606 HugeTLB page size. This is the size represented by
607 the legacy /proc/ hugepages APIs, used for SHM, and
608 default size when mounting hugetlbfs filesystems.
609 Defaults to the default architecture's huge page size
610 if not specified.
612 dhash_entries= [KNL]
613 Set number of hash buckets for dentry cache.
615 digi= [HW,SERIAL]
616 IO parameters + enable/disable command.
618 digiepca= [HW,SERIAL]
619 See drivers/char/README.epca and
620 Documentation/serial/digiepca.txt.
622 disable_mtrr_cleanup [X86]
623 The kernel tries to adjust MTRR layout from continuous
624 to discrete, to make X server driver able to add WB
625 entry later. This parameter disables that.
627 disable_mtrr_trim [X86, Intel and AMD only]
628 By default the kernel will trim any uncacheable
629 memory out of your available memory pool based on
630 MTRR settings. This parameter disables that behavior,
631 possibly causing your machine to run very slowly.
633 disable_timer_pin_1 [X86]
634 Disable PIN 1 of APIC timer
635 Can be useful to work around chipset bugs.
637 dmasound= [HW,OSS] Sound subsystem buffers
639 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
640 this option disables the debugging code at boot.
642 dma_debug_entries=<number>
643 This option allows to tune the number of preallocated
644 entries for DMA-API debugging code. One entry is
645 required per DMA-API allocation. Use this if the
646 DMA-API debugging code disables itself because the
647 architectural default is too low.
649 dscc4.setup= [NET]
651 dtc3181e= [HW,SCSI]
653 dynamic_printk Enables pr_debug()/dev_dbg() calls if
654 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
655 These can also be switched on/off via
656 <debugfs>/dynamic_printk/modules
658 earlycon= [KNL] Output early console device and options.
659 uart[8250],io,<addr>[,options]
660 uart[8250],mmio,<addr>[,options]
661 Start an early, polled-mode console on the 8250/16550
662 UART at the specified I/O port or MMIO address.
663 The options are the same as for ttyS, above.
665 earlyprintk= [X86,SH,BLACKFIN]
666 earlyprintk=vga
667 earlyprintk=serial[,ttySn[,baudrate]]
668 earlyprintk=dbgp
670 Append ",keep" to not disable it when the real console
671 takes over.
673 Only vga or serial or usb debug port at a time.
675 Currently only ttyS0 and ttyS1 are supported.
677 Interaction with the standard serial driver is not
678 very good.
680 The VGA output is eventually overwritten by the real
681 console.
683 eata= [HW,SCSI]
685 edd= [EDD]
686 Format: {"off" | "on" | "skip[mbr]"}
688 eisa_irq_edge= [PARISC,HW]
689 See header of drivers/parisc/eisa.c.
691 elanfreq= [X86-32]
692 See comment before function elanfreq_setup() in
693 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
695 elevator= [IOSCHED]
696 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
697 See Documentation/block/as-iosched.txt and
698 Documentation/block/deadline-iosched.txt for details.
700 elfcorehdr= [IA64,PPC,SH,X86]
701 Specifies physical address of start of kernel core
702 image elf header. Generally kexec loader will
703 pass this option to capture kernel.
704 See Documentation/kdump/kdump.txt for details.
706 enable_mtrr_cleanup [X86]
707 The kernel tries to adjust MTRR layout from continuous
708 to discrete, to make X server driver able to add WB
709 entry later. This parameter enables that.
711 enable_timer_pin_1 [X86]
712 Enable PIN 1 of APIC timer
713 Can be useful to work around chipset bugs
714 (in particular on some ATI chipsets).
715 The kernel tries to set a reasonable default.
717 enforcing [SELINUX] Set initial enforcing status.
718 Format: {"0" | "1"}
719 See security/selinux/Kconfig help text.
720 0 -- permissive (log only, no denials).
721 1 -- enforcing (deny and log).
722 Default value is 0.
723 Value can be changed at runtime via /selinux/enforce.
725 ether= [HW,NET] Ethernet cards parameters
726 This option is obsoleted by the "netdev=" option, which
727 has equivalent usage. See its documentation for details.
729 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
730 Format: <io>[,<irq>]
732 failslab=
733 fail_page_alloc=
734 fail_make_request=[KNL]
735 General fault injection mechanism.
736 Format: <interval>,<probability>,<space>,<times>
737 See also /Documentation/fault-injection/.
739 fd_mcs= [HW,SCSI]
740 See header of drivers/scsi/fd_mcs.c.
742 fdomain= [HW,SCSI]
743 See header of drivers/scsi/fdomain.c.
745 floppy= [HW]
746 See Documentation/blockdev/floppy.txt.
748 force_pal_cache_flush
749 [IA-64] Avoid check_sal_cache_flush which may hang on
750 buggy SAL_CACHE_FLUSH implementations. Using this
751 parameter will force ia64_sal_cache_flush to call
752 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
754 ftrace=[tracer]
755 [ftrace] will set and start the specified tracer
756 as early as possible in order to facilitate early
757 boot debugging.
759 ftrace_dump_on_oops
760 [ftrace] will dump the trace buffers on oops.
762 gamecon.map[2|3]=
763 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
764 support via parallel port (up to 5 devices per port)
765 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
766 See also Documentation/input/joystick-parport.txt
768 gamma= [HW,DRM]
770 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
771 Format: off | on
772 default: on
774 gdth= [HW,SCSI]
775 See header of drivers/scsi/gdth.c.
777 gpt [EFI] Forces disk with valid GPT signature but
778 invalid Protective MBR to be treated as GPT.
780 gvp11= [HW,SCSI]
782 hashdist= [KNL,NUMA] Large hashes allocated during boot
783 are distributed across NUMA nodes. Defaults on
784 for 64bit NUMA, off otherwise.
785 Format: 0 | 1 (for off | on)
787 hcl= [IA-64] SGI's Hardware Graph compatibility layer
789 hd= [EIDE] (E)IDE hard drive subsystem geometry
790 Format: <cyl>,<head>,<sect>
792 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
793 size of <nn>. This works even on boxes that have no
794 highmem otherwise. This also works to reduce highmem
795 size on bigger boxes.
797 highres= [KNL] Enable/disable high resolution timer mode.
798 Valid parameters: "on", "off"
799 Default: "on"
801 hisax= [HW,ISDN]
802 See Documentation/isdn/README.HiSax.
804 hlt [BUGS=ARM,SH]
806 hpet= [X86-32,HPET] option to control HPET usage
807 Format: { enable (default) | disable | force |
808 verbose }
809 disable: disable HPET and use PIT instead
810 force: allow force enabled of undocumented chips (ICH4,
811 VIA, nVidia)
812 verbose: show contents of HPET registers during setup
814 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
815 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
816 On x86-64 and powerpc, this option can be specified
817 multiple times interleaved with hugepages= to reserve
818 huge pages of different sizes. Valid pages sizes on
819 x86-64 are 2M (when the CPU supports "pse") and 1G
820 (when the CPU supports the "pdpe1gb" cpuinfo flag)
821 Note that 1GB pages can only be allocated at boot time
822 using hugepages= and not freed afterwards.
824 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
825 terminal devices. Valid values: 0..8
826 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
827 If specified, z/VM IUCV HVC accepts connections
828 from listed z/VM user IDs only.
830 i2c_bus= [HW] Override the default board specific I2C bus speed
831 or register an additional I2C bus that is not
832 registered from board initialization code.
833 Format:
834 <bus_id>,<clkrate>
836 i8042.debug [HW] Toggle i8042 debug mode
837 i8042.direct [HW] Put keyboard port into non-translated mode
838 i8042.dumbkbd [HW] Pretend that controller can only read data from
839 keyboard and cannot control its state
840 (Don't attempt to blink the leds)
841 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
842 i8042.nokbd [HW] Don't check/create keyboard port
843 i8042.noloop [HW] Disable the AUX Loopback command while probing
844 for the AUX port
845 i8042.nomux [HW] Don't check presence of an active multiplexing
846 controller
847 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
848 controllers
849 i8042.panicblink=
850 [HW] Frequency with which keyboard LEDs should blink
851 when kernel panics (default is 0.5 sec)
852 i8042.reset [HW] Reset the controller during init and cleanup
853 i8042.unlock [HW] Unlock (ignore) the keylock
855 i810= [HW,DRM]
857 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
858 indicates that the driver is running on unsupported
859 hardware.
860 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
861 does not match list of supported models.
862 i8k.power_status
863 [HW] Report power status in /proc/i8k
864 (disabled by default)
865 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
866 capability is set.
868 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
869 See Documentation/mca.txt.
871 icn= [HW,ISDN]
872 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
874 ide-core.nodma= [HW] (E)IDE subsystem
875 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
876 .vlb_clock .pci_clock .noflush .noprobe .nowerr .cdrom
877 .chs .ignore_cable are additional options
878 See Documentation/ide/ide.txt.
880 idebus= [HW] (E)IDE subsystem - VLB/PCI bus speed
881 See Documentation/ide/ide.txt.
883 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
884 Claim all unknown PCI IDE storage controllers.
886 idle= [X86]
887 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
888 Poll forces a polling idle loop that can slightly
889 improve the performance of waking up a idle CPU, but
890 will use a lot of power and make the system run hot.
891 Not recommended.
892 idle=mwait: On systems which support MONITOR/MWAIT but
893 the kernel chose to not use it because it doesn't save
894 as much power as a normal idle loop, use the
895 MONITOR/MWAIT idle loop anyways. Performance should be
896 the same as idle=poll.
897 idle=halt: Halt is forced to be used for CPU idle.
898 In such case C2/C3 won't be used again.
899 idle=nomwait: Disable mwait for CPU C-states
901 ignore_loglevel [KNL]
902 Ignore loglevel setting - this will print /all/
903 kernel messages to the console. Useful for debugging.
905 ihash_entries= [KNL]
906 Set number of hash buckets for inode cache.
908 ima_audit= [IMA]
909 Format: { "0" | "1" }
910 0 -- integrity auditing messages. (Default)
911 1 -- enable informational integrity auditing messages.
913 ima_hash= [IMA]
914 Formt: { "sha1" | "md5" }
915 default: "sha1"
917 ima_tcb [IMA]
918 Load a policy which meets the needs of the Trusted
919 Computing Base. This means IMA will measure all
920 programs exec'd, files mmap'd for exec, and all files
921 opened for read by uid=0.
923 in2000= [HW,SCSI]
924 See header of drivers/scsi/in2000.c.
926 init= [KNL]
927 Format: <full_path>
928 Run specified binary instead of /sbin/init as init
929 process.
931 initcall_debug [KNL] Trace initcalls as they are executed. Useful
932 for working out where the kernel is dying during
933 startup.
935 initrd= [BOOT] Specify the location of the initial ramdisk
937 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
938 Format: <irq>
940 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
941 on
942 Enable intel iommu driver.
943 off
944 Disable intel iommu driver.
945 igfx_off [Default Off]
946 By default, gfx is mapped as normal device. If a gfx
947 device has a dedicated DMAR unit, the DMAR unit is
948 bypassed by not enabling DMAR with this option. In
949 this case, gfx device will use physical address for
950 DMA.
951 forcedac [x86_64]
952 With this option iommu will not optimize to look
953 for io virtual address below 32 bit forcing dual
954 address cycle on pci bus for cards supporting greater
955 than 32 bit addressing. The default is to look
956 for translation below 32 bit and if not available
957 then look in the higher range.
958 strict [Default Off]
959 With this option on every unmap_single operation will
960 result in a hardware IOTLB flush operation as opposed
961 to batching them for performance.
963 inttest= [IA64]
965 iomem= Disable strict checking of access to MMIO memory
966 strict regions from userspace.
967 relaxed
969 iommu= [x86]
970 off
971 force
972 noforce
973 biomerge
974 panic
975 nopanic
976 merge
977 nomerge
978 forcesac
979 soft
981 io7= [HW] IO7 for Marvel based alpha systems
982 See comment before marvel_specify_io7 in
983 arch/alpha/kernel/core_marvel.c.
985 io_delay= [X86] I/O delay method
986 0x80
987 Standard port 0x80 based delay
988 0xed
989 Alternate port 0xed based delay (needed on some systems)
990 udelay
991 Simple two microseconds delay
992 none
993 No delay
995 ip= [IP_PNP]
996 See Documentation/filesystems/nfsroot.txt.
998 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
999 See comment before ip2_setup() in
1000 drivers/char/ip2/ip2base.c.
1002 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1003 See header of drivers/scsi/ips.c.
1005 irqfixup [HW]
1006 When an interrupt is not handled search all handlers
1007 for it. Intended to get systems with badly broken
1008 firmware running.
1010 irqpoll [HW]
1011 When an interrupt is not handled search all handlers
1012 for it. Also check all handlers each timer
1013 interrupt. Intended to get systems with badly broken
1014 firmware running.
1016 isapnp= [ISAPNP]
1017 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1019 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1020 Format:
1021 <cpu number>,...,<cpu number>
1022 or
1023 <cpu number>-<cpu number>
1024 (must be a positive range in ascending order)
1025 or a mixture
1026 <cpu number>,...,<cpu number>-<cpu number>
1028 This option can be used to specify one or more CPUs
1029 to isolate from the general SMP balancing and scheduling
1030 algorithms. You can move a process onto or off an
1031 "isolated" CPU via the CPU affinity syscalls or cpuset.
1032 <cpu number> begins at 0 and the maximum value is
1033 "number of CPUs in system - 1".
1035 This option is the preferred way to isolate CPUs. The
1036 alternative -- manually setting the CPU mask of all
1037 tasks in the system -- can cause problems and
1038 suboptimal load balancer performance.
1040 iucv= [HW,NET]
1042 js= [HW,JOY] Analog joystick
1043 See Documentation/input/joystick.txt.
1045 keepinitrd [HW,ARM]
1047 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1048 specifies the amount of memory usable by the kernel
1049 for non-movable allocations. The requested amount is
1050 spread evenly throughout all nodes in the system. The
1051 remaining memory in each node is used for Movable
1052 pages. In the event, a node is too small to have both
1053 kernelcore and Movable pages, kernelcore pages will
1054 take priority and other nodes will have a larger number
1055 of kernelcore pages. The Movable zone is used for the
1056 allocation of pages that may be reclaimed or moved
1057 by the page migration subsystem. This means that
1058 HugeTLB pages may not be allocated from this zone.
1059 Note that allocations like PTEs-from-HighMem still
1060 use the HighMem zone if it exists, and the Normal
1061 zone if it does not.
1063 kmemtrace.enable= [KNL,KMEMTRACE] Format: { yes | no }
1064 Controls whether kmemtrace is enabled
1065 at boot-time.
1067 kmemtrace.subbufs=n [KNL,KMEMTRACE] Overrides the number of
1068 subbufs kmemtrace's relay channel has. Set this
1069 higher than default (KMEMTRACE_N_SUBBUFS in code) if
1070 you experience buffer overruns.
1072 kgdboc= [HW] kgdb over consoles.
1073 Requires a tty driver that supports console polling.
1074 (only serial suported for now)
1075 Format: <serial_device>[,baud]
1077 kmac= [MIPS] korina ethernet MAC address.
1078 Configure the RouterBoard 532 series on-chip
1079 Ethernet adapter MAC address.
1081 kstack=N [X86] Print N words from the kernel stack
1082 in oops dumps.
1084 l2cr= [PPC]
1086 l3cr= [PPC]
1088 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1089 disabled it.
1091 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1092 in C2 power state.
1094 libata.dma= [LIBATA] DMA control
1095 libata.dma=0 Disable all PATA and SATA DMA
1096 libata.dma=1 PATA and SATA Disk DMA only
1097 libata.dma=2 ATAPI (CDROM) DMA only
1098 libata.dma=4 Compact Flash DMA only
1099 Combinations also work, so libata.dma=3 enables DMA
1100 for disks and CDROMs, but not CFs.
1102 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1103 when set.
1104 Format: <int>
1106 libata.force= [LIBATA] Force configurations. The format is comma
1107 separated list of "[ID:]VAL" where ID is
1108 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1109 matching port, link or device. Basically, it matches
1110 the ATA ID string printed on console by libata. If
1111 the whole ID part is omitted, the last PORT and DEVICE
1112 values are used. If ID hasn't been specified yet, the
1113 configuration applies to all ports, links and devices.
1115 If only DEVICE is omitted, the parameter applies to
1116 the port and all links and devices behind it. DEVICE
1117 number of 0 either selects the first device or the
1118 first fan-out link behind PMP device. It does not
1119 select the host link. DEVICE number of 15 selects the
1120 host link and device attached to it.
1122 The VAL specifies the configuration to force. As long
1123 as there's no ambiguity shortcut notation is allowed.
1124 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1125 The following configurations can be forced.
1127 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1128 Any ID with matching PORT is used.
1130 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1132 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1133 udma[/][16,25,33,44,66,100,133] notation is also
1134 allowed.
1136 * [no]ncq: Turn on or off NCQ.
1138 * nohrst, nosrst, norst: suppress hard, soft
1139 and both resets.
1141 If there are multiple matching configurations changing
1142 the same attribute, the last one is used.
1144 lmb=debug [KNL] Enable lmb debug messages.
1146 load_ramdisk= [RAM] List of ramdisks to load from floppy
1147 See Documentation/blockdev/ramdisk.txt.
1149 lockd.nlm_grace_period=P [NFS] Assign grace period.
1150 Format: <integer>
1152 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1153 Format: <integer>
1155 lockd.nlm_timeout=T [NFS] Assign timeout value.
1156 Format: <integer>
1158 lockd.nlm_udpport=M [NFS] Assign UDP port.
1159 Format: <integer>
1161 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1162 Format: <irq>
1164 loglevel= All Kernel Messages with a loglevel smaller than the
1165 console loglevel will be printed to the console. It can
1166 also be changed with klogd or other programs. The
1167 loglevels are defined as follows:
1169 0 (KERN_EMERG) system is unusable
1170 1 (KERN_ALERT) action must be taken immediately
1171 2 (KERN_CRIT) critical conditions
1172 3 (KERN_ERR) error conditions
1173 4 (KERN_WARNING) warning conditions
1174 5 (KERN_NOTICE) normal but significant condition
1175 6 (KERN_INFO) informational
1176 7 (KERN_DEBUG) debug-level messages
1178 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1179 Format: { n | nk | nM }
1180 n must be a power of two. The default size
1181 is set in the kernel config file.
1183 logo.nologo [FB] Disables display of the built-in Linux logo.
1184 This may be used to provide more screen space for
1185 kernel log messages and is useful when debugging
1186 kernel boot problems.
1188 lp=0 [LP] Specify parallel ports to use, e.g,
1189 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1190 lp=reset first parallel port). 'lp=0' disables the
1191 lp=auto printer driver. 'lp=reset' (which can be
1192 specified in addition to the ports) causes
1193 attached printers to be reset. Using
1194 lp=port1,port2,... specifies the parallel ports
1195 to associate lp devices with, starting with
1196 lp0. A port specification may be 'none' to skip
1197 that lp device, or a parport name such as
1198 'parport0'. Specifying 'lp=auto' instead of a
1199 port specification list means that device IDs
1200 from each port should be examined, to see if
1201 an IEEE 1284-compliant printer is attached; if
1202 so, the driver will manage that printer.
1203 See also header of drivers/char/lp.c.
1205 lpj=n [KNL]
1206 Sets loops_per_jiffy to given constant, thus avoiding
1207 time-consuming boot-time autodetection (up to 250 ms per
1208 CPU). 0 enables autodetection (default). To determine
1209 the correct value for your kernel, boot with normal
1210 autodetection and see what value is printed. Note that
1211 on SMP systems the preset will be applied to all CPUs,
1212 which is likely to cause problems if your CPUs need
1213 significantly divergent settings. An incorrect value
1214 will cause delays in the kernel to be wrong, leading to
1215 unpredictable I/O errors and other breakage. Although
1216 unlikely, in the extreme case this might damage your
1217 hardware.
1219 ltpc= [NET]
1220 Format: <io>,<irq>,<dma>
1222 mac5380= [HW,SCSI] Format:
1223 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1225 machvec= [IA64] Force the use of a particular machine-vector
1226 (machvec) in a generic kernel.
1227 Example: machvec=hpzx1_swiotlb
1229 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1230 than or equal to this physical address is ignored.
1232 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1233 should make use of. maxcpus=n : n >= 0 limits the
1234 kernel to using 'n' processors. n=0 is a special case,
1235 it is equivalent to "nosmp", which also disables
1236 the IO APIC.
1238 max_loop= [LOOP] Maximum number of loopback devices that can
1239 be mounted
1240 Format: <1-256>
1242 max_luns= [SCSI] Maximum number of LUNs to probe.
1243 Should be between 1 and 2^32-1.
1245 max_report_luns=
1246 [SCSI] Maximum number of LUNs received.
1247 Should be between 1 and 16384.
1249 mcatest= [IA-64]
1251 mce [X86-32] Machine Check Exception
1253 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1255 md= [HW] RAID subsystems devices and level
1256 See Documentation/md.txt.
1258 mdacon= [MDA]
1259 Format: <first>,<last>
1260 Specifies range of consoles to be captured by the MDA.
1262 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1263 Amount of memory to be used when the kernel is not able
1264 to see the whole system memory or for test.
1265 [X86-32] Use together with memmap= to avoid physical
1266 address space collisions. Without memmap= PCI devices
1267 could be placed at addresses belonging to unused RAM.
1269 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1270 memory.
1272 memchunk=nn[KMG]
1273 [KNL,SH] Allow user to override the default size for
1274 per-device physically contiguous DMA buffers.
1276 memmap=exactmap [KNL,X86] Enable setting of an exact
1277 E820 memory map, as specified by the user.
1278 Such memmap=exactmap lines can be constructed based on
1279 BIOS output or other requirements. See the memmap=nn@ss
1280 option description.
1282 memmap=nn[KMG]@ss[KMG]
1283 [KNL] Force usage of a specific region of memory
1284 Region of memory to be used, from ss to ss+nn.
1286 memmap=nn[KMG]#ss[KMG]
1287 [KNL,ACPI] Mark specific memory as ACPI data.
1288 Region of memory to be used, from ss to ss+nn.
1290 memmap=nn[KMG]$ss[KMG]
1291 [KNL,ACPI] Mark specific memory as reserved.
1292 Region of memory to be used, from ss to ss+nn.
1293 Example: Exclude memory from 0x18690000-0x1869ffff
1294 memmap=64K$0x18690000
1295 or
1296 memmap=0x10000$0x18690000
1298 memory_corruption_check=0/1 [X86]
1299 Some BIOSes seem to corrupt the first 64k of
1300 memory when doing things like suspend/resume.
1301 Setting this option will scan the memory
1302 looking for corruption. Enabling this will
1303 both detect corruption and prevent the kernel
1304 from using the memory being corrupted.
1305 However, its intended as a diagnostic tool; if
1306 repeatable BIOS-originated corruption always
1307 affects the same memory, you can use memmap=
1308 to prevent the kernel from using that memory.
1310 memory_corruption_check_size=size [X86]
1311 By default it checks for corruption in the low
1312 64k, making this memory unavailable for normal
1313 use. Use this parameter to scan for
1314 corruption in more or less memory.
1316 memory_corruption_check_period=seconds [X86]
1317 By default it checks for corruption every 60
1318 seconds. Use this parameter to check at some
1319 other rate. 0 disables periodic checking.
1321 memtest= [KNL,X86] Enable memtest
1322 Format: <integer>
1323 default : 0 <disable>
1324 Specifies the number of memtest passes to be
1325 performed. Each pass selects another test
1326 pattern from a given set of patterns. Memtest
1327 fills the memory with this pattern, validates
1328 memory contents and reserves bad memory
1329 regions that are detected.
1331 meye.*= [HW] Set MotionEye Camera parameters
1332 See Documentation/video4linux/meye.txt.
1334 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1335 Multi-Function General Purpose Timers on AMD Geode
1336 platforms.
1338 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1339 the BIOS has incorrectly applied a workaround. TinyBIOS
1340 version 0.98 is known to be affected, 0.99 fixes the
1341 problem by letting the user disable the workaround.
1343 mga= [HW,DRM]
1345 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1346 physical address is ignored.
1348 mminit_loglevel=
1349 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1350 parameter allows control of the logging verbosity for
1351 the additional memory initialisation checks. A value
1352 of 0 disables mminit logging and a level of 4 will
1353 log everything. Information is printed at KERN_DEBUG
1354 so loglevel=8 may also need to be specified.
1356 mousedev.tap_time=
1357 [MOUSE] Maximum time between finger touching and
1358 leaving touchpad surface for touch to be considered
1359 a tap and be reported as a left button click (for
1360 touchpads working in absolute mode only).
1361 Format: <msecs>
1362 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1363 reporting absolute coordinates, such as tablets
1364 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1365 reporting absolute coordinates, such as tablets
1367 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1368 is similar to kernelcore except it specifies the
1369 amount of memory used for migratable allocations.
1370 If both kernelcore and movablecore is specified,
1371 then kernelcore will be at *least* the specified
1372 value but may be more. If movablecore on its own
1373 is specified, the administrator must be careful
1374 that the amount of memory usable for all allocations
1375 is not too small.
1377 mpu401= [HW,OSS]
1378 Format: <io>,<irq>
1380 MTD_Partition= [MTD]
1381 Format: <name>,<region-number>,<size>,<offset>
1383 MTD_Region= [MTD] Format:
1384 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1386 mtdparts= [MTD]
1387 See drivers/mtd/cmdlinepart.c.
1389 mtdset= [ARM]
1390 ARM/S3C2412 JIVE boot control
1392 See arch/arm/mach-s3c2412/mach-jive.c
1394 mtouchusb.raw_coordinates=
1395 [HW] Make the MicroTouch USB driver use raw coordinates
1396 ('y', default) or cooked coordinates ('n')
1398 mtrr_chunk_size=nn[KMG] [X86]
1399 used for mtrr cleanup. It is largest continous chunk
1400 that could hold holes aka. UC entries.
1402 mtrr_gran_size=nn[KMG] [X86]
1403 Used for mtrr cleanup. It is granularity of mtrr block.
1404 Default is 1.
1405 Large value could prevent small alignment from
1406 using up MTRRs.
1408 mtrr_spare_reg_nr=n [X86]
1409 Format: <integer>
1410 Range: 0,7 : spare reg number
1411 Default : 1
1412 Used for mtrr cleanup. It is spare mtrr entries number.
1413 Set to 2 or more if your graphical card needs more.
1415 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1417 NCR_D700= [HW,SCSI]
1418 See header of drivers/scsi/NCR_D700.c.
1420 ncr5380= [HW,SCSI]
1422 ncr53c400= [HW,SCSI]
1424 ncr53c400a= [HW,SCSI]
1426 ncr53c406a= [HW,SCSI]
1428 ncr53c8xx= [HW,SCSI]
1430 netdev= [NET] Network devices parameters
1431 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1432 Note that mem_start is often overloaded to mean
1433 something different and driver-specific.
1434 This usage is only documented in each driver source
1435 file if at all.
1437 nf_conntrack.acct=
1438 [NETFILTER] Enable connection tracking flow accounting
1439 0 to disable accounting
1440 1 to enable accounting
1441 Default value depends on CONFIG_NF_CT_ACCT that is
1442 going to be removed in 2.6.29.
1444 nfsaddrs= [NFS]
1445 See Documentation/filesystems/nfsroot.txt.
1447 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1448 See Documentation/filesystems/nfsroot.txt.
1450 nfs.callback_tcpport=
1451 [NFS] set the TCP port on which the NFSv4 callback
1452 channel should listen.
1454 nfs.idmap_cache_timeout=
1455 [NFS] set the maximum lifetime for idmapper cache
1456 entries.
1458 nfs.enable_ino64=
1459 [NFS] enable 64-bit inode numbers.
1460 If zero, the NFS client will fake up a 32-bit inode
1461 number for the readdir() and stat() syscalls instead
1462 of returning the full 64-bit number.
1463 The default is to return 64-bit inode numbers.
1465 nmi_debug= [KNL,AVR32] Specify one or more actions to take
1466 when a NMI is triggered.
1467 Format: [state][,regs][,debounce][,die]
1469 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1470 Format: [panic,][num]
1471 Valid num: 0,1,2
1472 0 - turn nmi_watchdog off
1473 1 - use the IO-APIC timer for the NMI watchdog
1474 2 - use the local APIC for the NMI watchdog using
1475 a performance counter. Note: This will use one
1476 performance counter and the local APIC's performance
1477 vector.
1478 When panic is specified, panic when an NMI watchdog
1479 timeout occurs.
1480 This is useful when you use a panic=... timeout and
1481 need the box quickly up again.
1482 Instead of 1 and 2 it is possible to use the following
1483 symbolic names: lapic and ioapic
1484 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1486 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1487 emulation library even if a 387 maths coprocessor
1488 is present.
1490 no_console_suspend
1491 [HW] Never suspend the console
1492 Disable suspending of consoles during suspend and
1493 hibernate operations. Once disabled, debugging
1494 messages can reach various consoles while the rest
1495 of the system is being put to sleep (ie, while
1496 debugging driver suspend/resume hooks). This may
1497 not work reliably with all consoles, but is known
1498 to work with serial and VGA consoles.
1500 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1501 caches in the slab allocator. Saves per-node memory,
1502 but will impact performance.
1504 noalign [KNL,ARM]
1506 noapic [SMP,APIC] Tells the kernel to not make use of any
1507 IOAPICs that may be present in the system.
1509 nobats [PPC] Do not use BATs for mapping kernel lowmem
1510 on "Classic" PPC cores.
1512 nocache [ARM]
1514 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1516 nodelayacct [KNL] Disable per-task delay accounting
1518 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1520 nodsp [SH] Disable hardware DSP at boot time.
1522 noefi [X86] Disable EFI runtime services support.
1524 noexec [IA-64]
1526 noexec [X86]
1527 On X86-32 available only on PAE configured kernels.
1528 noexec=on: enable non-executable mappings (default)
1529 noexec=off: disable non-executable mappings
1531 noexec32 [X86-64]
1532 This affects only 32-bit executables.
1533 noexec32=on: enable non-executable mappings (default)
1534 read doesn't imply executable mappings
1535 noexec32=off: disable non-executable mappings
1536 read implies executable mappings
1538 nofpu [SH] Disable hardware FPU at boot time.
1540 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1541 register save and restore. The kernel will only save
1542 legacy floating-point registers on task switch.
1544 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1545 wfi(ARM) instruction doesn't work correctly and not to
1546 use it. This is also useful when using JTAG debugger.
1548 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1549 instruction doesn't work correctly and not to
1550 use it.
1552 no_file_caps Tells the kernel not to honor file capabilities. The
1553 only way then for a file to be executed with privilege
1554 is to be setuid root or executed by root.
1556 nohalt [IA-64] Tells the kernel not to use the power saving
1557 function PAL_HALT_LIGHT when idle. This increases
1558 power-consumption. On the positive side, it reduces
1559 interrupt wake-up latency, which may improve performance
1560 in certain environments such as networked servers or
1561 real-time systems.
1563 nohz= [KNL] Boottime enable/disable dynamic ticks
1564 Valid arguments: on, off
1565 Default: on
1567 noiotrap [SH] Disables trapped I/O port accesses.
1569 noirqdebug [X86-32] Disables the code which attempts to detect and
1570 disable unhandled interrupt sources.
1572 no_timer_check [X86,APIC] Disables the code which tests for
1573 broken timer IRQ sources.
1575 noisapnp [ISAPNP] Disables ISA PnP code.
1577 noinitrd [RAM] Tells the kernel not to load any configured
1578 initial RAM disk.
1580 nointroute [IA-64]
1582 nojitter [IA64] Disables jitter checking for ITC timers.
1584 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1586 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1588 noltlbs [PPC] Do not use large page/tlb entries for kernel
1589 lowmem mapping on PPC40x.
1591 nomca [IA-64] Disable machine check abort handling
1593 nomce [X86-32] Machine Check Exception
1595 nomfgpt [X86-32] Disable Multi-Function General Purpose
1596 Timer usage (for AMD Geode machines).
1598 norandmaps Don't use address space randomization. Equivalent to
1599 echo 0 > /proc/sys/kernel/randomize_va_space
1601 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1603 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1604 with UP alternatives
1606 noresidual [PPC] Don't use residual data on PReP machines.
1608 noresume [SWSUSP] Disables resume and restores original swap
1609 space.
1611 no-scroll [VGA] Disables scrollback.
1612 This is required for the Braillex ib80-piezo Braille
1613 reader made by F.H. Papenmeier (Germany).
1615 nosbagart [IA-64]
1617 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1619 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1620 and disable the IO APIC. legacy for "maxcpus=0".
1622 nosoftlockup [KNL] Disable the soft-lockup detector.
1624 noswapaccount [KNL] Disable accounting of swap in memory resource
1625 controller. (See Documentation/cgroups/memory.txt)
1627 nosync [HW,M68K] Disables sync negotiation for all devices.
1629 notsc [BUGS=X86-32] Disable Time Stamp Counter
1631 nousb [USB] Disable the USB subsystem
1633 nowb [ARM]
1635 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1637 nptcg= [IA64] Override max number of concurrent global TLB
1638 purges which is reported from either PAL_VM_SUMMARY or
1639 SAL PALO.
1641 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1643 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1644 one of ['zone', 'node', 'default'] can be specified
1645 This can be set from sysctl after boot.
1646 See Documentation/sysctl/vm.txt for details.
1648 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1649 See Documentation/debugging-via-ohci1394.txt for more
1650 info.
1652 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1653 Rather than timing out after 20 ms if an EC
1654 command is not properly ACKed, override the length
1655 of the timeout. We have interrupts disabled while
1656 waiting for the ACK, so if this is set too high
1657 interrupts *may* be lost!
1659 opl3= [HW,OSS]
1660 Format: <io>
1662 oprofile.timer= [HW]
1663 Use timer interrupt instead of performance counters
1665 osst= [HW,SCSI] SCSI Tape Driver
1666 Format: <buffer_size>,<write_threshold>
1667 See also Documentation/scsi/st.txt.
1669 panic= [KNL] Kernel behaviour on panic
1670 Format: <timeout>
1672 parkbd.port= [HW] Parallel port number the keyboard adapter is
1673 connected to, default is 0.
1674 Format: <parport#>
1675 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1676 0 for XT, 1 for AT (default is AT).
1677 Format: <mode>
1679 parport= [HW,PPT] Specify parallel ports. 0 disables.
1680 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1681 Use 'auto' to force the driver to use any
1682 IRQ/DMA settings detected (the default is to
1683 ignore detected IRQ/DMA settings because of
1684 possible conflicts). You can specify the base
1685 address, IRQ, and DMA settings; IRQ and DMA
1686 should be numbers, or 'auto' (for using detected
1687 settings on that particular port), or 'nofifo'
1688 (to avoid using a FIFO even if it is detected).
1689 Parallel ports are assigned in the order they
1690 are specified on the command line, starting
1691 with parport0.
1693 parport_init_mode= [HW,PPT]
1694 Configure VIA parallel port to operate in
1695 a specific mode. This is necessary on Pegasos
1696 computer where firmware has no options for setting
1697 up parallel port mode and sets it to spp.
1698 Currently this function knows 686a and 8231 chips.
1699 Format: [spp|ps2|epp|ecp|ecpepp]
1701 pas2= [HW,OSS] Format:
1702 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1704 pas16= [HW,SCSI]
1705 See header of drivers/scsi/pas16.c.
1707 pause_on_oops=
1708 Halt all CPUs after the first oops has been printed for
1709 the specified number of seconds. This is to be used if
1710 your oopses keep scrolling off the screen.
1712 pcbit= [HW,ISDN]
1714 pcd. [PARIDE]
1715 See header of drivers/block/paride/pcd.c.
1716 See also Documentation/blockdev/paride.txt.
1718 pci=option[,option...] [PCI] various PCI subsystem options:
1719 earlydump [X86] dump PCI config space before the kernel
1720 changes anything
1721 off [X86] don't probe for the PCI bus
1722 bios [X86-32] force use of PCI BIOS, don't access
1723 the hardware directly. Use this if your machine
1724 has a non-standard PCI host bridge.
1725 nobios [X86-32] disallow use of PCI BIOS, only direct
1726 hardware access methods are allowed. Use this
1727 if you experience crashes upon bootup and you
1728 suspect they are caused by the BIOS.
1729 conf1 [X86] Force use of PCI Configuration
1730 Mechanism 1.
1731 conf2 [X86] Force use of PCI Configuration
1732 Mechanism 2.
1733 noaer [PCIE] If the PCIEAER kernel config parameter is
1734 enabled, this kernel boot option can be used to
1735 disable the use of PCIE advanced error reporting.
1736 nodomains [PCI] Disable support for multiple PCI
1737 root domains (aka PCI segments, in ACPI-speak).
1738 nommconf [X86] Disable use of MMCONFIG for PCI
1739 Configuration
1740 nomsi [MSI] If the PCI_MSI kernel config parameter is
1741 enabled, this kernel boot option can be used to
1742 disable the use of MSI interrupts system-wide.
1743 noioapicquirk [APIC] Disable all boot interrupt quirks.
1744 Safety option to keep boot IRQs enabled. This
1745 should never be necessary.
1746 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1747 primary IO-APIC for bridges that cannot disable
1748 boot IRQs. This fixes a source of spurious IRQs
1749 when the system masks IRQs.
1750 noioapicreroute [APIC] Disable workaround that uses the
1751 boot IRQ equivalent of an IRQ that connects to
1752 a chipset where boot IRQs cannot be disabled.
1753 The opposite of ioapicreroute.
1754 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1755 routing table. These calls are known to be buggy
1756 on several machines and they hang the machine
1757 when used, but on other computers it's the only
1758 way to get the interrupt routing table. Try
1759 this option if the kernel is unable to allocate
1760 IRQs or discover secondary PCI buses on your
1761 motherboard.
1762 rom [X86] Assign address space to expansion ROMs.
1763 Use with caution as certain devices share
1764 address decoders between ROMs and other
1765 resources.
1766 norom [X86] Do not assign address space to
1767 expansion ROMs that do not already have
1768 BIOS assigned address ranges.
1769 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1770 assigned automatically to PCI devices. You can
1771 make the kernel exclude IRQs of your ISA cards
1772 this way.
1773 pirqaddr=0xAAAAA [X86] Specify the physical address
1774 of the PIRQ table (normally generated
1775 by the BIOS) if it is outside the
1776 F0000h-100000h range.
1777 lastbus=N [X86] Scan all buses thru bus #N. Can be
1778 useful if the kernel is unable to find your
1779 secondary buses and you want to tell it
1780 explicitly which ones they are.
1781 assign-busses [X86] Always assign all PCI bus
1782 numbers ourselves, overriding
1783 whatever the firmware may have done.
1784 usepirqmask [X86] Honor the possible IRQ mask stored
1785 in the BIOS $PIR table. This is needed on
1786 some systems with broken BIOSes, notably
1787 some HP Pavilion N5400 and Omnibook XE3
1788 notebooks. This will have no effect if ACPI
1789 IRQ routing is enabled.
1790 noacpi [X86] Do not use ACPI for IRQ routing
1791 or for PCI scanning.
1792 use_crs [X86] Use _CRS for PCI resource
1793 allocation.
1794 routeirq Do IRQ routing for all PCI devices.
1795 This is normally done in pci_enable_device(),
1796 so this option is a temporary workaround
1797 for broken drivers that don't call it.
1798 skip_isa_align [X86] do not align io start addr, so can
1799 handle more pci cards
1800 firmware [ARM] Do not re-enumerate the bus but instead
1801 just use the configuration from the
1802 bootloader. This is currently used on
1803 IXP2000 systems where the bus has to be
1804 configured a certain way for adjunct CPUs.
1805 noearly [X86] Don't do any early type 1 scanning.
1806 This might help on some broken boards which
1807 machine check when some devices' config space
1808 is read. But various workarounds are disabled
1809 and some IOMMU drivers will not work.
1810 bfsort Sort PCI devices into breadth-first order.
1811 This sorting is done to get a device
1812 order compatible with older (<= 2.4) kernels.
1813 nobfsort Don't sort PCI devices into breadth-first order.
1814 cbiosize=nn[KMG] The fixed amount of bus space which is
1815 reserved for the CardBus bridge's IO window.
1816 The default value is 256 bytes.
1817 cbmemsize=nn[KMG] The fixed amount of bus space which is
1818 reserved for the CardBus bridge's memory
1819 window. The default value is 64 megabytes.
1820 resource_alignment=
1821 Format:
1822 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1823 Specifies alignment and device to reassign
1824 aligned memory resources.
1825 If <order of align> is not specified,
1826 PAGE_SIZE is used as alignment.
1827 PCI-PCI bridge can be specified, if resource
1828 windows need to be expanded.
1830 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
1831 Management.
1832 off Disable ASPM.
1833 force Enable ASPM even on devices that claim not to support it.
1834 WARNING: Forcing ASPM on may cause system lockups.
1836 pcmv= [HW,PCMCIA] BadgePAD 4
1838 pd. [PARIDE]
1839 See Documentation/blockdev/paride.txt.
1841 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
1842 boot time.
1843 Format: { 0 | 1 }
1844 See arch/parisc/kernel/pdc_chassis.c
1846 pf. [PARIDE]
1847 See Documentation/blockdev/paride.txt.
1849 pg. [PARIDE]
1850 See Documentation/blockdev/paride.txt.
1852 pirq= [SMP,APIC] Manual mp-table setup
1853 See Documentation/x86/i386/IO-APIC.txt.
1855 plip= [PPT,NET] Parallel port network link
1856 Format: { parport<nr> | timid | 0 }
1857 See also Documentation/parport.txt.
1859 pmtmr= [X86] Manual setup of pmtmr I/O Port.
1860 Override pmtimer IOPort with a hex value.
1861 e.g. pmtmr=0x508
1863 pnp.debug [PNP]
1864 Enable PNP debug messages. This depends on the
1865 CONFIG_PNP_DEBUG_MESSAGES option.
1867 pnpacpi= [ACPI]
1868 { off }
1870 pnpbios= [ISAPNP]
1871 { on | off | curr | res | no-curr | no-res }
1873 pnp_reserve_irq=
1874 [ISAPNP] Exclude IRQs for the autoconfiguration
1876 pnp_reserve_dma=
1877 [ISAPNP] Exclude DMAs for the autoconfiguration
1879 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
1880 Ranges are in pairs (I/O port base and size).
1882 pnp_reserve_mem=
1883 [ISAPNP] Exclude memory regions for the
1884 autoconfiguration.
1885 Ranges are in pairs (memory base and size).
1887 ports= [IP_VS_FTP] IPVS ftp helper module
1888 Default is 21.
1889 Up to 8 (IP_VS_APP_MAX_PORTS) ports
1890 may be specified.
1891 Format: <port>,<port>....
1893 print-fatal-signals=
1894 [KNL] debug: print fatal signals
1895 print-fatal-signals=1: print segfault info to
1896 the kernel console.
1897 default: off.
1899 printk.time= Show timing data prefixed to each printk message line
1900 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
1902 processor.max_cstate= [HW,ACPI]
1903 Limit processor to maximum C-state
1904 max_cstate=9 overrides any DMI blacklist limit.
1906 processor.nocst [HW,ACPI]
1907 Ignore the _CST method to determine C-states,
1908 instead using the legacy FADT method
1910 profile= [KNL] Enable kernel profiling via /proc/profile
1911 Format: [schedule,]<number>
1912 Param: "schedule" - profile schedule points.
1913 Param: <number> - step/bucket size as a power of 2 for
1914 statistical time based profiling.
1915 Param: "sleep" - profile D-state sleeping (millisecs).
1916 Requires CONFIG_SCHEDSTATS
1917 Param: "kvm" - profile VM exits.
1919 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
1920 before loading.
1921 See Documentation/blockdev/ramdisk.txt.
1923 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
1924 probe for; one of (bare|imps|exps|lifebook|any).
1925 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
1926 per second.
1927 psmouse.resetafter= [HW,MOUSE]
1928 Try to reset the device after so many bad packets
1929 (0 = never).
1930 psmouse.resolution=
1931 [HW,MOUSE] Set desired mouse resolution, in dpi.
1932 psmouse.smartscroll=
1933 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
1934 0 = disabled, 1 = enabled (default).
1936 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
1937 Format:
1938 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
1940 pt. [PARIDE]
1941 See Documentation/blockdev/paride.txt.
1943 pty.legacy_count=
1944 [KNL] Number of legacy pty's. Overwrites compiled-in
1945 default number.
1947 quiet [KNL] Disable most log messages
1949 r128= [HW,DRM]
1951 raid= [HW,RAID]
1952 See Documentation/md.txt.
1954 ramdisk_blocksize= [RAM]
1955 See Documentation/blockdev/ramdisk.txt.
1957 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
1958 See Documentation/blockdev/ramdisk.txt.
1960 rcupdate.blimit= [KNL,BOOT]
1961 Set maximum number of finished RCU callbacks to process
1962 in one batch.
1964 rcupdate.qhimark= [KNL,BOOT]
1965 Set threshold of queued
1966 RCU callbacks over which batch limiting is disabled.
1968 rcupdate.qlowmark= [KNL,BOOT]
1969 Set threshold of queued RCU callbacks below which
1970 batch limiting is re-enabled.
1972 rdinit= [KNL]
1973 Format: <full_path>
1974 Run specified binary instead of /init from the ramdisk,
1975 used for early userspace startup. See initrd.
1977 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
1978 Format: <reboot_mode>[,<reboot_mode2>[,...]]
1979 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
1981 relax_domain_level=
1982 [KNL, SMP] Set scheduler's default relax_domain_level.
1983 See Documentation/cgroups/cpusets.txt.
1985 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
1987 reservetop= [X86-32]
1988 Format: nn[KMG]
1989 Reserves a hole at the top of the kernel virtual
1990 address space.
1992 reset_devices [KNL] Force drivers to reset the underlying device
1993 during initialization.
1995 resume= [SWSUSP]
1996 Specify the partition device for software suspend
1998 resume_offset= [SWSUSP]
1999 Specify the offset from the beginning of the partition
2000 given by "resume=" at which the swap header is located,
2001 in <PAGE_SIZE> units (needed only for swap files).
2002 See Documentation/power/swsusp-and-swap-files.txt
2004 retain_initrd [RAM] Keep initrd memory after extraction
2006 rhash_entries= [KNL,NET]
2007 Set number of hash buckets for route cache
2009 riscom8= [HW,SERIAL]
2010 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2012 ro [KNL] Mount root device read-only on boot
2014 root= [KNL] Root filesystem
2016 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2017 mount the root filesystem
2019 rootflags= [KNL] Set root filesystem mount option string
2021 rootfstype= [KNL] Set root filesystem type
2023 rootwait [KNL] Wait (indefinitely) for root device to show up.
2024 Useful for devices that are detected asynchronously
2025 (e.g. USB and MMC devices).
2027 root_plug.vendor_id=
2028 [ROOTPLUG] Override the default vendor ID
2030 root_plug.product_id=
2031 [ROOTPLUG] Override the default product ID
2033 root_plug.debug=
2034 [ROOTPLUG] Enable debugging output
2036 rw [KNL] Mount root device read-write on boot
2038 S [KNL] Run init in single mode
2040 sa1100ir [NET]
2041 See drivers/net/irda/sa1100_ir.c.
2043 sbni= [NET] Granch SBNI12 leased line adapter
2045 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2046 Format: <io>[,<timeout>[,<isapnp>]]
2048 scsi_debug_*= [SCSI]
2049 See drivers/scsi/scsi_debug.c.
2051 scsi_default_dev_flags=
2052 [SCSI] SCSI default device flags
2053 Format: <integer>
2055 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2056 Format: <vendor>:<model>:<flags>
2057 (flags are integer value)
2059 scsi_logging_level= [SCSI] a bit mask of logging levels
2060 See drivers/scsi/scsi_logging.h for bits. Also
2061 settable via sysctl at dev.scsi.logging_level
2062 (/proc/sys/dev/scsi/logging_level).
2063 There is also a nice 'scsi_logging_level' script in the
2064 S390-tools package, available for download at
2065 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2067 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2068 discovered. async scans them in kernel threads,
2069 allowing boot to proceed. none ignores them, expecting
2070 user space to do the scan.
2072 security= [SECURITY] Choose a security module to enable at boot.
2073 If this boot parameter is not specified, only the first
2074 security module asking for security registration will be
2075 loaded. An invalid security module name will be treated
2076 as if no module has been chosen.
2078 selinux= [SELINUX] Disable or enable SELinux at boot time.
2079 Format: { "0" | "1" }
2080 See security/selinux/Kconfig help text.
2081 0 -- disable.
2082 1 -- enable.
2083 Default value is set via kernel config option.
2084 If enabled at boot time, /selinux/disable can be used
2085 later to disable prior to initial policy load.
2087 serialnumber [BUGS=X86-32]
2089 shapers= [NET]
2090 Maximal number of shapers.
2092 show_msr= [x86] show boot-time MSR settings
2093 Format: { <integer> }
2094 Show boot-time (BIOS-initialized) MSR settings.
2095 The parameter means the number of CPUs to show,
2096 for example 1 means boot CPU only.
2098 sim710= [SCSI,HW]
2099 See header of drivers/scsi/sim710.c.
2101 simeth= [IA-64]
2102 simscsi=
2104 slram= [HW,MTD]
2106 slub_debug[=options[,slabs]] [MM, SLUB]
2107 Enabling slub_debug allows one to determine the
2108 culprit if slab objects become corrupted. Enabling
2109 slub_debug can create guard zones around objects and
2110 may poison objects when not in use. Also tracks the
2111 last alloc / free. For more information see
2112 Documentation/vm/slub.txt.
2114 slub_max_order= [MM, SLUB]
2115 Determines the maximum allowed order for slabs.
2116 A high setting may cause OOMs due to memory
2117 fragmentation. For more information see
2118 Documentation/vm/slub.txt.
2120 slub_min_objects= [MM, SLUB]
2121 The minimum number of objects per slab. SLUB will
2122 increase the slab order up to slub_max_order to
2123 generate a sufficiently large slab able to contain
2124 the number of objects indicated. The higher the number
2125 of objects the smaller the overhead of tracking slabs
2126 and the less frequently locks need to be acquired.
2127 For more information see Documentation/vm/slub.txt.
2129 slub_min_order= [MM, SLUB]
2130 Determines the mininum page order for slabs. Must be
2131 lower than slub_max_order.
2132 For more information see Documentation/vm/slub.txt.
2134 slub_nomerge [MM, SLUB]
2135 Disable merging of slabs with similar size. May be
2136 necessary if there is some reason to distinguish
2137 allocs to different slabs. Debug options disable
2138 merging on their own.
2139 For more information see Documentation/vm/slub.txt.
2141 smart2= [HW]
2142 Format: <io1>[,<io2>[,...,<io8>]]
2144 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2145 attempt to substitute SMP alternatives once at boot.
2147 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2148 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2149 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2150 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2151 smsc-ircc2.ircc_irq= [HW] IRQ line
2152 smsc-ircc2.ircc_dma= [HW] DMA channel
2153 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2154 0: Toshiba Satellite 1800 (GP data pin select)
2155 1: Fast pin select (default)
2156 2: ATC IRMode
2158 snd-ad1816a= [HW,ALSA]
2160 snd-ad1848= [HW,ALSA]
2162 snd-ali5451= [HW,ALSA]
2164 snd-als100= [HW,ALSA]
2166 snd-als4000= [HW,ALSA]
2168 snd-azt2320= [HW,ALSA]
2170 snd-cmi8330= [HW,ALSA]
2172 snd-cmipci= [HW,ALSA]
2174 snd-cs4231= [HW,ALSA]
2176 snd-cs4232= [HW,ALSA]
2178 snd-cs4236= [HW,ALSA]
2180 snd-cs4281= [HW,ALSA]
2182 snd-cs46xx= [HW,ALSA]
2184 snd-dt019x= [HW,ALSA]
2186 snd-dummy= [HW,ALSA]
2188 snd-emu10k1= [HW,ALSA]
2190 snd-ens1370= [HW,ALSA]
2192 snd-ens1371= [HW,ALSA]
2194 snd-es968= [HW,ALSA]
2196 snd-es1688= [HW,ALSA]
2198 snd-es18xx= [HW,ALSA]
2200 snd-es1938= [HW,ALSA]
2202 snd-es1968= [HW,ALSA]
2204 snd-fm801= [HW,ALSA]
2206 snd-gusclassic= [HW,ALSA]
2208 snd-gusextreme= [HW,ALSA]
2210 snd-gusmax= [HW,ALSA]
2212 snd-hdsp= [HW,ALSA]
2214 snd-ice1712= [HW,ALSA]
2216 snd-intel8x0= [HW,ALSA]
2218 snd-interwave= [HW,ALSA]
2220 snd-interwave-stb=
2221 [HW,ALSA]
2223 snd-korg1212= [HW,ALSA]
2225 snd-maestro3= [HW,ALSA]
2227 snd-mpu401= [HW,ALSA]
2229 snd-mtpav= [HW,ALSA]
2231 snd-nm256= [HW,ALSA]
2233 snd-opl3sa2= [HW,ALSA]
2235 snd-opti92x-ad1848=
2236 [HW,ALSA]
2238 snd-opti92x-cs4231=
2239 [HW,ALSA]
2241 snd-opti93x= [HW,ALSA]
2243 snd-pmac= [HW,ALSA]
2245 snd-rme32= [HW,ALSA]
2247 snd-rme96= [HW,ALSA]
2249 snd-rme9652= [HW,ALSA]
2251 snd-sb8= [HW,ALSA]
2253 snd-sb16= [HW,ALSA]
2255 snd-sbawe= [HW,ALSA]
2257 snd-serial= [HW,ALSA]
2259 snd-sgalaxy= [HW,ALSA]
2261 snd-sonicvibes= [HW,ALSA]
2263 snd-sun-amd7930=
2264 [HW,ALSA]
2266 snd-sun-cs4231= [HW,ALSA]
2268 snd-trident= [HW,ALSA]
2270 snd-usb-audio= [HW,ALSA,USB]
2272 snd-via82xx= [HW,ALSA]
2274 snd-virmidi= [HW,ALSA]
2276 snd-wavefront= [HW,ALSA]
2278 snd-ymfpci= [HW,ALSA]
2280 softlockup_panic=
2281 [KNL] Should the soft-lockup detector generate panics.
2283 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2284 See Documentation/sonypi.txt
2286 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2287 See Documentation/serial/specialix.txt.
2289 spia_io_base= [HW,MTD]
2290 spia_fio_base=
2291 spia_pedr=
2292 spia_peddr=
2294 sscape= [HW,OSS]
2295 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2297 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2298 See Documentation/scsi/st.txt.
2300 stacktrace [FTRACE]
2301 Enabled the stack tracer on boot up.
2303 sti= [PARISC,HW]
2304 Format: <num>
2305 Set the STI (builtin display/keyboard on the HP-PARISC
2306 machines) console (graphic card) which should be used
2307 as the initial boot-console.
2308 See also comment in drivers/video/console/sticore.c.
2310 sti_font= [HW]
2311 See comment in drivers/video/console/sticore.c.
2313 stifb= [HW]
2314 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2316 sunrpc.pool_mode=
2317 [NFS]
2318 Control how the NFS server code allocates CPUs to
2319 service thread pools. Depending on how many NICs
2320 you have and where their interrupts are bound, this
2321 option will affect which CPUs will do NFS serving.
2322 Note: this parameter cannot be changed while the
2323 NFS server is running.
2325 auto the server chooses an appropriate mode
2326 automatically using heuristics
2327 global a single global pool contains all CPUs
2328 percpu one pool for each CPU
2329 pernode one pool for each NUMA node (equivalent
2330 to global on non-NUMA machines)
2332 swiotlb= [IA-64] Number of I/O TLB slabs
2334 switches= [HW,M68k]
2336 sym53c416= [HW,SCSI]
2337 See header of drivers/scsi/sym53c416.c.
2339 sysrq_always_enabled
2340 [KNL]
2341 Ignore sysrq setting - this boot parameter will
2342 neutralize any effect of /proc/sys/kernel/sysrq.
2343 Useful for debugging.
2345 t128= [HW,SCSI]
2346 See header of drivers/scsi/t128.c.
2348 tdfx= [HW,DRM]
2350 test_suspend= [SUSPEND]
2351 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2352 standby suspend) as the system sleep state to briefly
2353 enter during system startup. The system is woken from
2354 this state using a wakeup-capable RTC alarm.
2356 thash_entries= [KNL,NET]
2357 Set number of hash buckets for TCP connection
2359 thermal.act= [HW,ACPI]
2360 -1: disable all active trip points in all thermal zones
2361 <degrees C>: override all lowest active trip points
2363 thermal.crt= [HW,ACPI]
2364 -1: disable all critical trip points in all thermal zones
2365 <degrees C>: override all critical trip points
2367 thermal.nocrt= [HW,ACPI]
2368 Set to disable actions on ACPI thermal zone
2369 critical and hot trip points.
2371 thermal.off= [HW,ACPI]
2372 1: disable ACPI thermal control
2374 thermal.psv= [HW,ACPI]
2375 -1: disable all passive trip points
2376 <degrees C>: override all passive trip points to this
2377 value
2379 thermal.tzp= [HW,ACPI]
2380 Specify global default ACPI thermal zone polling rate
2381 <deci-seconds>: poll all this frequency
2382 0: no polling (default)
2384 tmscsim= [HW,SCSI]
2385 See comment before function dc390_setup() in
2386 drivers/scsi/tmscsim.c.
2388 topology= [S390]
2389 Format: {off | on}
2390 Specify if the kernel should make use of the cpu
2391 topology informations if the hardware supports these.
2392 The scheduler will make use of these informations and
2393 e.g. base its process migration decisions on it.
2394 Default is off.
2396 tp720= [HW,PS2]
2398 trace_buf_size=nn[KMG] [ftrace] will set tracing buffer size.
2400 trix= [HW,OSS] MediaTrix AudioTrix Pro
2401 Format:
2402 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2404 tsc= Disable clocksource-must-verify flag for TSC.
2405 Format: <string>
2406 [x86] reliable: mark tsc clocksource as reliable, this
2407 disables clocksource verification at runtime.
2408 Used to enable high-resolution timer mode on older
2409 hardware, and in virtualized environment.
2411 turbografx.map[2|3]= [HW,JOY]
2412 TurboGraFX parallel port interface
2413 Format:
2414 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2415 See also Documentation/input/joystick-parport.txt
2417 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2418 See header of drivers/scsi/u14-34f.c.
2420 uart401= [HW,OSS]
2421 Format: <io>,<irq>
2423 uart6850= [HW,OSS]
2424 Format: <io>,<irq>
2426 uhci-hcd.ignore_oc=
2427 [USB] Ignore overcurrent events (default N).
2428 Some badly-designed motherboards generate lots of
2429 bogus events, for ports that aren't wired to
2430 anything. Set this parameter to avoid log spamming.
2431 Note that genuine overcurrent events won't be
2432 reported either.
2434 unknown_nmi_panic
2435 [X86]
2436 Set unknown_nmi_panic=1 early on boot.
2438 usbcore.autosuspend=
2439 [USB] The autosuspend time delay (in seconds) used
2440 for newly-detected USB devices (default 2). This
2441 is the time required before an idle device will be
2442 autosuspended. Devices for which the delay is set
2443 to a negative value won't be autosuspended at all.
2445 usbcore.usbfs_snoop=
2446 [USB] Set to log all usbfs traffic (default 0 = off).
2448 usbcore.blinkenlights=
2449 [USB] Set to cycle leds on hubs (default 0 = off).
2451 usbcore.old_scheme_first=
2452 [USB] Start with the old device initialization
2453 scheme (default 0 = off).
2455 usbcore.use_both_schemes=
2456 [USB] Try the other device initialization scheme
2457 if the first one fails (default 1 = enabled).
2459 usbcore.initial_descriptor_timeout=
2460 [USB] Specifies timeout for the initial 64-byte
2461 USB_REQ_GET_DESCRIPTOR request in milliseconds
2462 (default 5000 = 5.0 seconds).
2464 usbhid.mousepoll=
2465 [USBHID] The interval which mice are to be polled at.
2467 usb-storage.delay_use=
2468 [UMS] The delay in seconds before a new device is
2469 scanned for Logical Units (default 5).
2471 usb-storage.quirks=
2472 [UMS] A list of quirks entries to supplement or
2473 override the built-in unusual_devs list. List
2474 entries are separated by commas. Each entry has
2475 the form VID:PID:Flags where VID and PID are Vendor
2476 and Product ID values (4-digit hex numbers) and
2477 Flags is a set of characters, each corresponding
2478 to a common usb-storage quirk flag as follows:
2479 a = SANE_SENSE (collect more than 18 bytes
2480 of sense data);
2481 c = FIX_CAPACITY (decrease the reported
2482 device capacity by one sector);
2483 h = CAPACITY_HEURISTICS (decrease the
2484 reported device capacity by one
2485 sector if the number is odd);
2486 i = IGNORE_DEVICE (don't bind to this
2487 device);
2488 l = NOT_LOCKABLE (don't try to lock and
2489 unlock ejectable media);
2490 m = MAX_SECTORS_64 (don't transfer more
2491 than 64 sectors = 32 KB at a time);
2492 o = CAPACITY_OK (accept the capacity
2493 reported by the device);
2494 r = IGNORE_RESIDUE (the device reports
2495 bogus residue values);
2496 s = SINGLE_LUN (the device has only one
2497 Logical Unit);
2498 w = NO_WP_DETECT (don't test whether the
2499 medium is write-protected).
2500 Example: quirks=0419:aaf5:rl,0421:0433:rc
2502 vdso= [X86,SH]
2503 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2504 vdso=1: enable VDSO (default)
2505 vdso=0: disable VDSO mapping
2507 vdso32= [X86]
2508 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2509 vdso32=1: enable 32-bit VDSO (default)
2510 vdso32=0: disable 32-bit VDSO mapping
2512 vector= [IA-64,SMP]
2513 vector=percpu: enable percpu vector domain
2515 video= [FB] Frame buffer configuration
2516 See Documentation/fb/modedb.txt.
2518 vga= [BOOT,X86-32] Select a particular video mode
2519 See Documentation/x86/boot.txt and
2520 Documentation/svga.txt.
2521 Use vga=ask for menu.
2522 This is actually a boot loader parameter; the value is
2523 passed to the kernel using a special protocol.
2525 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2526 size of <nn>. This can be used to increase the
2527 minimum size (128MB on x86). It can also be used to
2528 decrease the size and leave more room for directly
2529 mapped kernel RAM.
2531 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2532 Format: <command>
2534 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2535 Format: <command>
2537 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2538 Format: <command>
2540 vt.default_blu= [VT]
2541 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2542 Change the default blue palette of the console.
2543 This is a 16-member array composed of values
2544 ranging from 0-255.
2546 vt.default_grn= [VT]
2547 Format: <green0>,<green1>,<green2>,...,<green15>
2548 Change the default green palette of the console.
2549 This is a 16-member array composed of values
2550 ranging from 0-255.
2552 vt.default_red= [VT]
2553 Format: <red0>,<red1>,<red2>,...,<red15>
2554 Change the default red palette of the console.
2555 This is a 16-member array composed of values
2556 ranging from 0-255.
2558 vt.default_utf8=
2559 [VT]
2560 Format=<0|1>
2561 Set system-wide default UTF-8 mode for all tty's.
2562 Default is 1, i.e. UTF-8 mode is enabled for all
2563 newly opened terminals.
2565 waveartist= [HW,OSS]
2566 Format: <io>,<irq>,<dma>,<dma2>
2568 wd33c93= [HW,SCSI]
2569 See header of drivers/scsi/wd33c93.c.
2571 wd7000= [HW,SCSI]
2572 See header of drivers/scsi/wd7000.c.
2574 wdt= [WDT] Watchdog
2575 See Documentation/watchdog/wdt.txt.
2577 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2578 default x2apic cluster mode on platforms
2579 supporting x2apic.
2581 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2582 xd_geo= See header of drivers/block/xd.c.
2584 xirc2ps_cs= [NET,PCMCIA]
2585 Format:
2586 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2588 ______________________________________________________________________
2590 TODO:
2592 Add documentation for ALSA options.
2593 Add more DRM drivers.