| blob | c3d1cea3fc6e599c92a1244c418951817558dca8 |
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 GCOV GCOV profiling is enabled.
52 HW Appropriate hardware is enabled.
53 IA-64 IA-64 architecture is enabled.
54 IMA Integrity measurement architecture is enabled.
55 IOSCHED More than one I/O scheduler is enabled.
56 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
57 IPV6 IPv6 support is enabled.
58 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
61 KVM Kernel Virtual Machine support is enabled.
62 LIBATA Libata driver is enabled
63 LP Printer support is enabled.
64 LOOP Loopback device support is enabled.
65 M68k M68k architecture is enabled.
66 These options have more detailed description inside of
67 Documentation/m68k/kernel-options.txt.
68 MCA MCA bus support is enabled.
69 MDA MDA console support is enabled.
70 MOUSE Appropriate mouse support is enabled.
71 MSI Message Signaled Interrupts (PCI).
72 MTD MTD (Memory Technology Device) support is enabled.
73 NET Appropriate network support is enabled.
74 NUMA NUMA support is enabled.
75 GENERIC_TIME The generic timeofday code is enabled.
76 NFS Appropriate NFS support is enabled.
77 OSS OSS sound support is enabled.
78 PV_OPS A paravirtualized kernel is enabled.
79 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
80 PARISC The PA-RISC architecture is enabled.
81 PCI PCI bus support is enabled.
82 PCIE PCI Express support is enabled.
83 PCMCIA The PCMCIA subsystem is enabled.
84 PNP Plug & Play support is enabled.
85 PPC PowerPC architecture is enabled.
86 PPT Parallel port support is enabled.
87 PS2 Appropriate PS/2 support is enabled.
88 RAM RAM disk support is enabled.
89 S390 S390 architecture is enabled.
90 SCSI Appropriate SCSI support is enabled.
91 A lot of drivers has their options described inside of
92 Documentation/scsi/.
93 SECURITY Different security models are enabled.
94 SELINUX SELinux support is enabled.
95 SERIAL Serial support is enabled.
96 SH SuperH architecture is enabled.
97 SMP The kernel is an SMP kernel.
98 SPARC Sparc architecture is enabled.
99 SWSUSP Software suspend (hibernation) is enabled.
100 SUSPEND System suspend states are enabled.
101 FTRACE Function tracing enabled.
102 TS Appropriate touchscreen support is enabled.
103 UMS USB Mass Storage support is enabled.
104 USB USB support is enabled.
105 USBHID USB Human Interface Device support is enabled.
106 V4L Video For Linux support is enabled.
107 VGA The VGA console has been enabled.
108 VT Virtual terminal support is enabled.
109 WDT Watchdog support is enabled.
110 XT IBM PC/XT MFM hard disk support is enabled.
111 X86-32 X86-32, aka i386 architecture is enabled.
112 X86-64 X86-64 architecture is enabled.
113 More X86-64 boot options can be found in
114 Documentation/x86/x86_64/boot-options.txt .
115 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
117 In addition, the following text indicates that the option:
119 BUGS= Relates to possible processor bugs on the said processor.
120 KNL Is a kernel start-up parameter.
121 BOOT Is a boot loader parameter.
123 Parameters denoted with BOOT are actually interpreted by the boot
124 loader, and have no meaning to the kernel directly.
125 Do not modify the syntax of boot loader parameters without extreme
126 need or coordination with <Documentation/x86/boot.txt>.
128 There are also arch-specific kernel-parameters not documented here.
129 See for example <Documentation/x86/x86_64/boot-options.txt>.
131 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
132 a trailing = on the name of any parameter states that that parameter will
133 be entered as an environment variable, whereas its absence indicates that
134 it will appear as a kernel argument readable via /proc/cmdline by programs
135 running once the system is up.
137 The number of kernel parameters is not limited, but the length of the
138 complete command line (parameters including spaces etc.) is limited to
139 a fixed number of characters. This limit depends on the architecture
140 and is between 256 and 4096 characters. It is defined in the file
141 ./include/asm/setup.h as COMMAND_LINE_SIZE.
144 acpi= [HW,ACPI,X86]
145 Advanced Configuration and Power Interface
146 Format: { force | off | ht | strict | noirq | rsdt }
147 force -- enable ACPI if default was off
148 off -- disable ACPI if default was on
149 noirq -- do not use ACPI for IRQ routing
150 ht -- run only enough ACPI to enable Hyper Threading
151 strict -- Be less tolerant of platforms that are not
152 strictly ACPI specification compliant.
153 rsdt -- prefer RSDT over (default) XSDT
155 See also Documentation/power/pm.txt, pci=noacpi
157 acpi_apic_instance= [ACPI, IOAPIC]
158 Format: <int>
159 2: use 2nd APIC table, if available
160 1,0: use 1st APIC table
161 default: 0
163 acpi_backlight= [HW,ACPI]
164 acpi_backlight=vendor
165 acpi_backlight=video
166 If set to vendor, prefer vendor specific driver
167 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
168 of the ACPI video.ko driver.
170 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
171 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
172 Format: <int>
173 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
174 debug output. Bits in debug_layer correspond to a
175 _COMPONENT in an ACPI source file, e.g.,
176 #define _COMPONENT ACPI_PCI_COMPONENT
177 Bits in debug_level correspond to a level in
178 ACPI_DEBUG_PRINT statements, e.g.,
179 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
180 The debug_level mask defaults to "info". See
181 Documentation/acpi/debug.txt for more information about
182 debug layers and levels.
184 Enable processor driver info messages:
185 acpi.debug_layer=0x20000000
186 Enable PCI/PCI interrupt routing info messages:
187 acpi.debug_layer=0x400000
188 Enable AML "Debug" output, i.e., stores to the Debug
189 object while interpreting AML:
190 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
191 Enable all messages related to ACPI hardware:
192 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
194 Some values produce so much output that the system is
195 unusable. The "log_buf_len" parameter may be useful
196 if you need to capture more output.
198 acpi_display_output= [HW,ACPI]
199 acpi_display_output=vendor
200 acpi_display_output=video
201 See above.
203 acpi_irq_balance [HW,ACPI]
204 ACPI will balance active IRQs
205 default in APIC mode
207 acpi_irq_nobalance [HW,ACPI]
208 ACPI will not move active IRQs (default)
209 default in PIC mode
211 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
212 Format: <irq>,<irq>...
214 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
215 use by PCI
216 Format: <irq>,<irq>...
218 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
220 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
221 Format: To spoof as Windows 98: ="Microsoft Windows"
223 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
224 acpi_osi="string1" # add string1 -- only one string
225 acpi_osi="!string2" # remove built-in string2
226 acpi_osi= # disable all strings
228 acpi_pm_good [X86]
229 Override the pmtimer bug detection: force the kernel
230 to assume that this machine's pmtimer latches its value
231 and always returns good values.
233 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
234 Format: { level | edge | high | low }
236 acpi_serialize [HW,ACPI] force serialization of AML methods
238 acpi_skip_timer_override [HW,ACPI]
239 Recognize and ignore IRQ0/pin2 Interrupt Override.
240 For broken nForce2 BIOS resulting in XT-PIC timer.
242 acpi_sleep= [HW,ACPI] Sleep options
243 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
244 old_ordering, s4_nonvs, sci_force_enable }
245 See Documentation/power/video.txt for information on
246 s3_bios and s3_mode.
247 s3_beep is for debugging; it makes the PC's speaker beep
248 as soon as the kernel's real-mode entry point is called.
249 s4_nohwsig prevents ACPI hardware signature from being
250 used during resume from hibernation.
251 old_ordering causes the ACPI 1.0 ordering of the _PTS
252 control method, with respect to putting devices into
253 low power states, to be enforced (the ACPI 2.0 ordering
254 of _PTS is used by default).
255 s4_nonvs prevents the kernel from saving/restoring the
256 ACPI NVS memory during hibernation.
257 sci_force_enable causes the kernel to set SCI_EN directly
258 on resume from S1/S3 (which is against the ACPI spec,
259 but some broken systems don't work without it).
261 acpi_use_timer_override [HW,ACPI]
262 Use timer override. For some broken Nvidia NF5 boards
263 that require a timer override, but don't have HPET
265 acpi_enforce_resources= [ACPI]
266 { strict | lax | no }
267 Check for resource conflicts between native drivers
268 and ACPI OperationRegions (SystemIO and SystemMemory
269 only). IO ports and memory declared in ACPI might be
270 used by the ACPI subsystem in arbitrary AML code and
271 can interfere with legacy drivers.
272 strict (default): access to resources claimed by ACPI
273 is denied; legacy drivers trying to access reserved
274 resources will fail to bind to device using them.
275 lax: access to resources claimed by ACPI is allowed;
276 legacy drivers trying to access reserved resources
277 will bind successfully but a warning message is logged.
278 no: ACPI OperationRegions are not marked as reserved,
279 no further checks are performed.
281 ad1848= [HW,OSS]
282 Format: <io>,<irq>,<dma>,<dma2>,<type>
284 add_efi_memmap [EFI; X86] Include EFI memory map in
285 kernel's map of available physical RAM.
287 advansys= [HW,SCSI]
288 See header of drivers/scsi/advansys.c.
290 advwdt= [HW,WDT] Advantech WDT
291 Format: <iostart>,<iostop>
293 aedsp16= [HW,OSS] Audio Excel DSP 16
294 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
295 See also header of sound/oss/aedsp16.c.
297 agp= [AGP]
298 { off | try_unsupported }
299 off: disable AGP support
300 try_unsupported: try to drive unsupported chipsets
301 (may crash computer or cause data corruption)
303 aha152x= [HW,SCSI]
304 See Documentation/scsi/aha152x.txt.
306 aha1542= [HW,SCSI]
307 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
309 aic7xxx= [HW,SCSI]
310 See Documentation/scsi/aic7xxx.txt.
312 aic79xx= [HW,SCSI]
313 See Documentation/scsi/aic79xx.txt.
315 alignment= [KNL,ARM]
316 Allow the default userspace alignment fault handler
317 behaviour to be specified. Bit 0 enables warnings,
318 bit 1 enables fixups, and bit 2 sends a segfault.
320 amd_iommu= [HW,X86-84]
321 Pass parameters to the AMD IOMMU driver in the system.
322 Possible values are:
323 fullflush - enable flushing of IO/TLB entries when
324 they are unmapped. Otherwise they are
325 flushed before they will be reused, which
326 is a lot of faster
328 amijoy.map= [HW,JOY] Amiga joystick support
329 Map of devices attached to JOY0DAT and JOY1DAT
330 Format: <a>,<b>
331 See also Documentation/kernel/input/joystick.txt
333 analog.map= [HW,JOY] Analog joystick and gamepad support
334 Specifies type or capabilities of an analog joystick
335 connected to one of 16 gameports
336 Format: <type1>,<type2>,..<type16>
338 apc= [HW,SPARC]
339 Power management functions (SPARCstation-4/5 + deriv.)
340 Format: noidle
341 Disable APC CPU standby support. SPARCstation-Fox does
342 not play well with APC CPU idle - disable it if you have
343 APC and your system crashes randomly.
345 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
346 Change the output verbosity whilst booting
347 Format: { quiet (default) | verbose | debug }
348 Change the amount of debugging information output
349 when initialising the APIC and IO-APIC components.
351 autoconf= [IPV6]
352 See Documentation/networking/ipv6.txt.
354 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
355 Limit apic dumping. The parameter defines the maximal
356 number of local apics being dumped. Also it is possible
357 to set it to "all" by meaning -- no limit here.
358 Format: { 1 (default) | 2 | ... | all }.
359 The parameter valid if only apic=debug or
360 apic=verbose is specified.
361 Example: apic=debug show_lapic=all
363 apm= [APM] Advanced Power Management
364 See header of arch/x86/kernel/apm_32.c.
366 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
367 Format: <io>,<irq>,<nodeID>
369 ataflop= [HW,M68k]
371 atarimouse= [HW,MOUSE] Atari Mouse
373 atascsi= [HW,SCSI] Atari SCSI
375 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
376 EzKey and similar keyboards
378 atkbd.reset= [HW] Reset keyboard during initialization
380 atkbd.set= [HW] Select keyboard code set
381 Format: <int> (2 = AT (default), 3 = PS/2)
383 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
384 keyboards
386 atkbd.softraw= [HW] Choose between synthetic and real raw mode
387 Format: <bool> (0 = real, 1 = synthetic (default))
389 atkbd.softrepeat= [HW]
390 Use software keyboard repeat
392 autotest [IA64]
394 baycom_epp= [HW,AX25]
395 Format: <io>,<mode>
397 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
398 Format: <io>,<mode>
399 See header of drivers/net/hamradio/baycom_par.c.
401 baycom_ser_fdx= [HW,AX25]
402 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
403 Format: <io>,<irq>,<mode>[,<baud>]
404 See header of drivers/net/hamradio/baycom_ser_fdx.c.
406 baycom_ser_hdx= [HW,AX25]
407 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
408 Format: <io>,<irq>,<mode>
409 See header of drivers/net/hamradio/baycom_ser_hdx.c.
411 boot_delay= Milliseconds to delay each printk during boot.
412 Values larger than 10 seconds (10000) are changed to
413 no delay (0).
414 Format: integer
416 bootmem_debug [KNL] Enable bootmem allocator debug messages.
418 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
419 bttv.radio= Most important insmod options are available as
420 kernel args too.
421 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
422 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
424 BusLogic= [HW,SCSI]
425 See drivers/scsi/BusLogic.c, comment before function
426 BusLogic_ParseDriverOptions().
428 c101= [NET] Moxa C101 synchronous serial card
430 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
431 Sometimes CPU hardware bugs make them report the cache
432 size incorrectly. The kernel will attempt work arounds
433 to fix known problems, but for some CPUs it is not
434 possible to determine what the correct size should be.
435 This option provides an override for these situations.
437 capability.disable=
438 [SECURITY] Disable capabilities. This would normally
439 be used only if an alternative security model is to be
440 configured. Potentially dangerous and should only be
441 used if you are entirely sure of the consequences.
443 ccw_timeout_log [S390]
444 See Documentation/s390/CommonIO for details.
446 cgroup_disable= [KNL] Disable a particular controller
447 Format: {name of the controller(s) to disable}
448 {Currently supported controllers - "memory"}
450 checkreqprot [SELINUX] Set initial checkreqprot flag value.
451 Format: { "0" | "1" }
452 See security/selinux/Kconfig help text.
453 0 -- check protection applied by kernel (includes
454 any implied execute protection).
455 1 -- check protection requested by application.
456 Default value is set via a kernel config option.
457 Value can be changed at runtime via
458 /selinux/checkreqprot.
460 cio_ignore= [S390]
461 See Documentation/s390/CommonIO for details.
463 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
464 [Deprecated]
465 Forces specified clocksource (if available) to be used
466 when calculating gettimeofday(). If specified
467 clocksource is not available, it defaults to PIT.
468 Format: { pit | tsc | cyclone | pmtmr }
470 clocksource= [GENERIC_TIME] Override the default clocksource
471 Format: <string>
472 Override the default clocksource and use the clocksource
473 with the name specified.
474 Some clocksource names to choose from, depending on
475 the platform:
476 [all] jiffies (this is the base, fallback clocksource)
477 [ACPI] acpi_pm
478 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
479 pxa_timer,timer3,32k_counter,timer0_1
480 [AVR32] avr32
481 [X86-32] pit,hpet,tsc,vmi-timer;
482 scx200_hrt on Geode; cyclone on IBM x440
483 [MIPS] MIPS
484 [PARISC] cr16
485 [S390] tod
486 [SH] SuperH
487 [SPARC64] tick
488 [X86-64] hpet,tsc
490 clearcpuid=BITNUM [X86]
491 Disable CPUID feature X for the kernel. See
492 arch/x86/include/asm/cpufeature.h for the valid bit
493 numbers. Note the Linux specific bits are not necessarily
494 stable over kernel options, but the vendor specific
495 ones should be.
496 Also note that user programs calling CPUID directly
497 or using the feature without checking anything
498 will still see it. This just prevents it from
499 being used by the kernel or shown in /proc/cpuinfo.
500 Also note the kernel might malfunction if you disable
501 some critical bits.
503 cmo_free_hint= [PPC] Format: { yes | no }
504 Specify whether pages are marked as being inactive
505 when they are freed. This is used in CMO environments
506 to determine OS memory pressure for page stealing by
507 a hypervisor.
508 Default: yes
510 code_bytes [X86] How many bytes of object code to print
511 in an oops report.
512 Range: 0 - 8192
513 Default: 64
515 com20020= [HW,NET] ARCnet - COM20020 chipset
516 Format:
517 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
519 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
520 Format: <io>[,<irq>]
522 com90xx= [HW,NET]
523 ARCnet - COM90xx chipset (memory-mapped buffers)
524 Format: <io>[,<irq>[,<memstart>]]
526 condev= [HW,S390] console device
527 conmode=
529 console= [KNL] Output console device and options.
531 tty<n> Use the virtual console device <n>.
533 ttyS<n>[,options]
534 ttyUSB0[,options]
535 Use the specified serial port. The options are of
536 the form "bbbbpnf", where "bbbb" is the baud rate,
537 "p" is parity ("n", "o", or "e"), "n" is number of
538 bits, and "f" is flow control ("r" for RTS or
539 omit it). Default is "9600n8".
541 See Documentation/serial-console.txt for more
542 information. See
543 Documentation/networking/netconsole.txt for an
544 alternative.
546 uart[8250],io,<addr>[,options]
547 uart[8250],mmio,<addr>[,options]
548 Start an early, polled-mode console on the 8250/16550
549 UART at the specified I/O port or MMIO address,
550 switching to the matching ttyS device later. The
551 options are the same as for ttyS, above.
553 If the device connected to the port is not a TTY but a braille
554 device, prepend "brl," before the device type, for instance
555 console=brl,ttyS0
556 For now, only VisioBraille is supported.
558 consoleblank= [KNL] The console blank (screen saver) timeout in
559 seconds. Defaults to 10*60 = 10mins. A value of 0
560 disables the blank timer.
562 coredump_filter=
563 [KNL] Change the default value for
564 /proc/<pid>/coredump_filter.
565 See also Documentation/filesystems/proc.txt.
567 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
568 Format:
569 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
571 crashkernel=nn[KMG]@ss[KMG]
572 [KNL] Reserve a chunk of physical memory to
573 hold a kernel to switch to with kexec on panic.
575 crashkernel=range1:size1[,range2:size2,...][@offset]
576 [KNL] Same as above, but depends on the memory
577 in the running system. The syntax of range is
578 start-[end] where start and end are both
579 a memory unit (amount[KMG]). See also
580 Documentation/kdump/kdump.txt for a example.
582 cs89x0_dma= [HW,NET]
583 Format: <dma>
585 cs89x0_media= [HW,NET]
586 Format: { rj45 | aui | bnc }
588 dasd= [HW,NET]
589 See header of drivers/s390/block/dasd_devmap.c.
591 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
592 (one device per port)
593 Format: <port#>,<type>
594 See also Documentation/input/joystick-parport.txt
596 debug [KNL] Enable kernel debugging (events log level).
598 debug_locks_verbose=
599 [KNL] verbose self-tests
600 Format=<0|1>
601 Print debugging info while doing the locking API
602 self-tests.
603 We default to 0 (no extra messages), setting it to
604 1 will print _a lot_ more information - normally
605 only useful to kernel developers.
607 debug_objects [KNL] Enable object debugging
609 no_debug_objects
610 [KNL] Disable object debugging
612 debugpat [X86] Enable PAT debugging
614 decnet.addr= [HW,NET]
615 Format: <area>[,<node>]
616 See also Documentation/networking/decnet.txt.
618 default_hugepagesz=
619 [same as hugepagesz=] The size of the default
620 HugeTLB page size. This is the size represented by
621 the legacy /proc/ hugepages APIs, used for SHM, and
622 default size when mounting hugetlbfs filesystems.
623 Defaults to the default architecture's huge page size
624 if not specified.
626 dhash_entries= [KNL]
627 Set number of hash buckets for dentry cache.
629 digi= [HW,SERIAL]
630 IO parameters + enable/disable command.
632 digiepca= [HW,SERIAL]
633 See drivers/char/README.epca and
634 Documentation/serial/digiepca.txt.
636 disable= [IPV6]
637 See Documentation/networking/ipv6.txt.
639 disable_ipv6= [IPV6]
640 See Documentation/networking/ipv6.txt.
642 disable_mtrr_cleanup [X86]
643 The kernel tries to adjust MTRR layout from continuous
644 to discrete, to make X server driver able to add WB
645 entry later. This parameter disables that.
647 disable_mtrr_trim [X86, Intel and AMD only]
648 By default the kernel will trim any uncacheable
649 memory out of your available memory pool based on
650 MTRR settings. This parameter disables that behavior,
651 possibly causing your machine to run very slowly.
653 disable_timer_pin_1 [X86]
654 Disable PIN 1 of APIC timer
655 Can be useful to work around chipset bugs.
657 dmasound= [HW,OSS] Sound subsystem buffers
659 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
660 this option disables the debugging code at boot.
662 dma_debug_entries=<number>
663 This option allows to tune the number of preallocated
664 entries for DMA-API debugging code. One entry is
665 required per DMA-API allocation. Use this if the
666 DMA-API debugging code disables itself because the
667 architectural default is too low.
669 dma_debug_driver=<driver_name>
670 With this option the DMA-API debugging driver
671 filter feature can be enabled at boot time. Just
672 pass the driver to filter for as the parameter.
673 The filter can be disabled or changed to another
674 driver later using sysfs.
676 dscc4.setup= [NET]
678 dtc3181e= [HW,SCSI]
680 dynamic_printk Enables pr_debug()/dev_dbg() calls if
681 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
682 These can also be switched on/off via
683 <debugfs>/dynamic_printk/modules
685 earlycon= [KNL] Output early console device and options.
686 uart[8250],io,<addr>[,options]
687 uart[8250],mmio,<addr>[,options]
688 Start an early, polled-mode console on the 8250/16550
689 UART at the specified I/O port or MMIO address.
690 The options are the same as for ttyS, above.
692 earlyprintk= [X86,SH,BLACKFIN]
693 earlyprintk=vga
694 earlyprintk=serial[,ttySn[,baudrate]]
695 earlyprintk=ttySn[,baudrate]
696 earlyprintk=dbgp[debugController#]
698 Append ",keep" to not disable it when the real console
699 takes over.
701 Only vga or serial or usb debug port at a time.
703 Currently only ttyS0 and ttyS1 are supported.
705 Interaction with the standard serial driver is not
706 very good.
708 The VGA output is eventually overwritten by the real
709 console.
711 eata= [HW,SCSI]
713 edd= [EDD]
714 Format: {"off" | "on" | "skip[mbr]"}
716 eisa_irq_edge= [PARISC,HW]
717 See header of drivers/parisc/eisa.c.
719 elanfreq= [X86-32]
720 See comment before function elanfreq_setup() in
721 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
723 elevator= [IOSCHED]
724 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
725 See Documentation/block/as-iosched.txt and
726 Documentation/block/deadline-iosched.txt for details.
728 elfcorehdr= [IA64,PPC,SH,X86]
729 Specifies physical address of start of kernel core
730 image elf header. Generally kexec loader will
731 pass this option to capture kernel.
732 See Documentation/kdump/kdump.txt for details.
734 enable_mtrr_cleanup [X86]
735 The kernel tries to adjust MTRR layout from continuous
736 to discrete, to make X server driver able to add WB
737 entry later. This parameter enables that.
739 enable_timer_pin_1 [X86]
740 Enable PIN 1 of APIC timer
741 Can be useful to work around chipset bugs
742 (in particular on some ATI chipsets).
743 The kernel tries to set a reasonable default.
745 enforcing [SELINUX] Set initial enforcing status.
746 Format: {"0" | "1"}
747 See security/selinux/Kconfig help text.
748 0 -- permissive (log only, no denials).
749 1 -- enforcing (deny and log).
750 Default value is 0.
751 Value can be changed at runtime via /selinux/enforce.
753 ether= [HW,NET] Ethernet cards parameters
754 This option is obsoleted by the "netdev=" option, which
755 has equivalent usage. See its documentation for details.
757 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
758 Format: <io>[,<irq>]
760 failslab=
761 fail_page_alloc=
762 fail_make_request=[KNL]
763 General fault injection mechanism.
764 Format: <interval>,<probability>,<space>,<times>
765 See also /Documentation/fault-injection/.
767 fd_mcs= [HW,SCSI]
768 See header of drivers/scsi/fd_mcs.c.
770 fdomain= [HW,SCSI]
771 See header of drivers/scsi/fdomain.c.
773 floppy= [HW]
774 See Documentation/blockdev/floppy.txt.
776 force_pal_cache_flush
777 [IA-64] Avoid check_sal_cache_flush which may hang on
778 buggy SAL_CACHE_FLUSH implementations. Using this
779 parameter will force ia64_sal_cache_flush to call
780 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
782 ftrace=[tracer]
783 [FTRACE] will set and start the specified tracer
784 as early as possible in order to facilitate early
785 boot debugging.
787 ftrace_dump_on_oops
788 [FTRACE] will dump the trace buffers on oops.
790 ftrace_filter=[function-list]
791 [FTRACE] Limit the functions traced by the function
792 tracer at boot up. function-list is a comma separated
793 list of functions. This list can be changed at run
794 time by the set_ftrace_filter file in the debugfs
795 tracing directory.
797 ftrace_notrace=[function-list]
798 [FTRACE] Do not trace the functions specified in
799 function-list. This list can be changed at run time
800 by the set_ftrace_notrace file in the debugfs
801 tracing directory.
803 ftrace_graph_filter=[function-list]
804 [FTRACE] Limit the top level callers functions traced
805 by the function graph tracer at boot up.
806 function-list is a comma separated list of functions
807 that can be changed at run time by the
808 set_graph_function file in the debugfs tracing directory.
810 gamecon.map[2|3]=
811 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
812 support via parallel port (up to 5 devices per port)
813 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
814 See also Documentation/input/joystick-parport.txt
816 gamma= [HW,DRM]
818 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
819 Format: off | on
820 default: on
822 gcov_persist= [GCOV] When non-zero (default), profiling data for
823 kernel modules is saved and remains accessible via
824 debugfs, even when the module is unloaded/reloaded.
825 When zero, profiling data is discarded and associated
826 debugfs files are removed at module unload time.
828 gdth= [HW,SCSI]
829 See header of drivers/scsi/gdth.c.
831 gpt [EFI] Forces disk with valid GPT signature but
832 invalid Protective MBR to be treated as GPT.
834 gvp11= [HW,SCSI]
836 hashdist= [KNL,NUMA] Large hashes allocated during boot
837 are distributed across NUMA nodes. Defaults on
838 for 64bit NUMA, off otherwise.
839 Format: 0 | 1 (for off | on)
841 hcl= [IA-64] SGI's Hardware Graph compatibility layer
843 hd= [EIDE] (E)IDE hard drive subsystem geometry
844 Format: <cyl>,<head>,<sect>
846 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
847 size of <nn>. This works even on boxes that have no
848 highmem otherwise. This also works to reduce highmem
849 size on bigger boxes.
851 highres= [KNL] Enable/disable high resolution timer mode.
852 Valid parameters: "on", "off"
853 Default: "on"
855 hisax= [HW,ISDN]
856 See Documentation/isdn/README.HiSax.
858 hlt [BUGS=ARM,SH]
860 hpet= [X86-32,HPET] option to control HPET usage
861 Format: { enable (default) | disable | force |
862 verbose }
863 disable: disable HPET and use PIT instead
864 force: allow force enabled of undocumented chips (ICH4,
865 VIA, nVidia)
866 verbose: show contents of HPET registers during setup
868 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
869 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
870 On x86-64 and powerpc, this option can be specified
871 multiple times interleaved with hugepages= to reserve
872 huge pages of different sizes. Valid pages sizes on
873 x86-64 are 2M (when the CPU supports "pse") and 1G
874 (when the CPU supports the "pdpe1gb" cpuinfo flag)
875 Note that 1GB pages can only be allocated at boot time
876 using hugepages= and not freed afterwards.
878 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
879 terminal devices. Valid values: 0..8
880 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
881 If specified, z/VM IUCV HVC accepts connections
882 from listed z/VM user IDs only.
884 i2c_bus= [HW] Override the default board specific I2C bus speed
885 or register an additional I2C bus that is not
886 registered from board initialization code.
887 Format:
888 <bus_id>,<clkrate>
890 i8042.debug [HW] Toggle i8042 debug mode
891 i8042.direct [HW] Put keyboard port into non-translated mode
892 i8042.dumbkbd [HW] Pretend that controller can only read data from
893 keyboard and cannot control its state
894 (Don't attempt to blink the leds)
895 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
896 i8042.nokbd [HW] Don't check/create keyboard port
897 i8042.noloop [HW] Disable the AUX Loopback command while probing
898 for the AUX port
899 i8042.nomux [HW] Don't check presence of an active multiplexing
900 controller
901 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
902 controllers
903 i8042.panicblink=
904 [HW] Frequency with which keyboard LEDs should blink
905 when kernel panics (default is 0.5 sec)
906 i8042.reset [HW] Reset the controller during init and cleanup
907 i8042.unlock [HW] Unlock (ignore) the keylock
909 i810= [HW,DRM]
911 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
912 indicates that the driver is running on unsupported
913 hardware.
914 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
915 does not match list of supported models.
916 i8k.power_status
917 [HW] Report power status in /proc/i8k
918 (disabled by default)
919 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
920 capability is set.
922 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
923 See Documentation/mca.txt.
925 icn= [HW,ISDN]
926 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
928 ide-core.nodma= [HW] (E)IDE subsystem
929 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
930 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
931 .cdrom .chs .ignore_cable are additional options
932 See Documentation/ide/ide.txt.
934 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
935 Claim all unknown PCI IDE storage controllers.
937 idle= [X86]
938 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
939 Poll forces a polling idle loop that can slightly
940 improve the performance of waking up a idle CPU, but
941 will use a lot of power and make the system run hot.
942 Not recommended.
943 idle=mwait: On systems which support MONITOR/MWAIT but
944 the kernel chose to not use it because it doesn't save
945 as much power as a normal idle loop, use the
946 MONITOR/MWAIT idle loop anyways. Performance should be
947 the same as idle=poll.
948 idle=halt: Halt is forced to be used for CPU idle.
949 In such case C2/C3 won't be used again.
950 idle=nomwait: Disable mwait for CPU C-states
952 ignore_loglevel [KNL]
953 Ignore loglevel setting - this will print /all/
954 kernel messages to the console. Useful for debugging.
956 ihash_entries= [KNL]
957 Set number of hash buckets for inode cache.
959 ima_audit= [IMA]
960 Format: { "0" | "1" }
961 0 -- integrity auditing messages. (Default)
962 1 -- enable informational integrity auditing messages.
964 ima_hash= [IMA]
965 Format: { "sha1" | "md5" }
966 default: "sha1"
968 ima_tcb [IMA]
969 Load a policy which meets the needs of the Trusted
970 Computing Base. This means IMA will measure all
971 programs exec'd, files mmap'd for exec, and all files
972 opened for read by uid=0.
974 in2000= [HW,SCSI]
975 See header of drivers/scsi/in2000.c.
977 init= [KNL]
978 Format: <full_path>
979 Run specified binary instead of /sbin/init as init
980 process.
982 initcall_debug [KNL] Trace initcalls as they are executed. Useful
983 for working out where the kernel is dying during
984 startup.
986 initrd= [BOOT] Specify the location of the initial ramdisk
988 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
989 Format: <irq>
991 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
992 on
993 Enable intel iommu driver.
994 off
995 Disable intel iommu driver.
996 igfx_off [Default Off]
997 By default, gfx is mapped as normal device. If a gfx
998 device has a dedicated DMAR unit, the DMAR unit is
999 bypassed by not enabling DMAR with this option. In
1000 this case, gfx device will use physical address for
1001 DMA.
1002 forcedac [x86_64]
1003 With this option iommu will not optimize to look
1004 for io virtual address below 32 bit forcing dual
1005 address cycle on pci bus for cards supporting greater
1006 than 32 bit addressing. The default is to look
1007 for translation below 32 bit and if not available
1008 then look in the higher range.
1009 strict [Default Off]
1010 With this option on every unmap_single operation will
1011 result in a hardware IOTLB flush operation as opposed
1012 to batching them for performance.
1014 inttest= [IA64]
1016 iomem= Disable strict checking of access to MMIO memory
1017 strict regions from userspace.
1018 relaxed
1020 iommu= [x86]
1021 off
1022 force
1023 noforce
1024 biomerge
1025 panic
1026 nopanic
1027 merge
1028 nomerge
1029 forcesac
1030 soft
1031 pt [x86, IA64]
1033 io7= [HW] IO7 for Marvel based alpha systems
1034 See comment before marvel_specify_io7 in
1035 arch/alpha/kernel/core_marvel.c.
1037 io_delay= [X86] I/O delay method
1038 0x80
1039 Standard port 0x80 based delay
1040 0xed
1041 Alternate port 0xed based delay (needed on some systems)
1042 udelay
1043 Simple two microseconds delay
1044 none
1045 No delay
1047 ip= [IP_PNP]
1048 See Documentation/filesystems/nfs/nfsroot.txt.
1050 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1051 See comment before ip2_setup() in
1052 drivers/char/ip2/ip2base.c.
1054 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1055 See header of drivers/scsi/ips.c.
1057 irqfixup [HW]
1058 When an interrupt is not handled search all handlers
1059 for it. Intended to get systems with badly broken
1060 firmware running.
1062 irqpoll [HW]
1063 When an interrupt is not handled search all handlers
1064 for it. Also check all handlers each timer
1065 interrupt. Intended to get systems with badly broken
1066 firmware running.
1068 isapnp= [ISAPNP]
1069 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1071 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1072 Format:
1073 <cpu number>,...,<cpu number>
1074 or
1075 <cpu number>-<cpu number>
1076 (must be a positive range in ascending order)
1077 or a mixture
1078 <cpu number>,...,<cpu number>-<cpu number>
1080 This option can be used to specify one or more CPUs
1081 to isolate from the general SMP balancing and scheduling
1082 algorithms. You can move a process onto or off an
1083 "isolated" CPU via the CPU affinity syscalls or cpuset.
1084 <cpu number> begins at 0 and the maximum value is
1085 "number of CPUs in system - 1".
1087 This option is the preferred way to isolate CPUs. The
1088 alternative -- manually setting the CPU mask of all
1089 tasks in the system -- can cause problems and
1090 suboptimal load balancer performance.
1092 iucv= [HW,NET]
1094 js= [HW,JOY] Analog joystick
1095 See Documentation/input/joystick.txt.
1097 keepinitrd [HW,ARM]
1099 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1100 specifies the amount of memory usable by the kernel
1101 for non-movable allocations. The requested amount is
1102 spread evenly throughout all nodes in the system. The
1103 remaining memory in each node is used for Movable
1104 pages. In the event, a node is too small to have both
1105 kernelcore and Movable pages, kernelcore pages will
1106 take priority and other nodes will have a larger number
1107 of kernelcore pages. The Movable zone is used for the
1108 allocation of pages that may be reclaimed or moved
1109 by the page migration subsystem. This means that
1110 HugeTLB pages may not be allocated from this zone.
1111 Note that allocations like PTEs-from-HighMem still
1112 use the HighMem zone if it exists, and the Normal
1113 zone if it does not.
1115 kgdboc= [HW] kgdb over consoles.
1116 Requires a tty driver that supports console polling.
1117 (only serial supported for now)
1118 Format: <serial_device>[,baud]
1120 kmac= [MIPS] korina ethernet MAC address.
1121 Configure the RouterBoard 532 series on-chip
1122 Ethernet adapter MAC address.
1124 kmemleak= [KNL] Boot-time kmemleak enable/disable
1125 Valid arguments: on, off
1126 Default: on
1128 kstack=N [X86] Print N words from the kernel stack
1129 in oops dumps.
1131 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1132 Default is 0 (don't ignore, but inject #GP)
1134 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1135 Default is 1 (enabled)
1137 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1138 Default is 0 (off)
1140 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1141 for all guests.
1142 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1144 kvm-intel.bypass_guest_pf=
1145 [KVM,Intel] Disables bypassing of guest page faults
1146 on Intel chips. Default is 1 (enabled)
1148 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1149 (virtualized MMU) support on capable Intel chips.
1150 Default is 1 (enabled)
1152 kvm-intel.emulate_invalid_guest_state=
1153 [KVM,Intel] Enable emulation of invalid guest states
1154 Default is 0 (disabled)
1156 kvm-intel.flexpriority=
1157 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1158 Default is 1 (enabled)
1160 kvm-intel.unrestricted_guest=
1161 [KVM,Intel] Disable unrestricted guest feature
1162 (virtualized real and unpaged mode) on capable
1163 Intel chips. Default is 1 (enabled)
1165 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1166 feature (tagged TLBs) on capable Intel chips.
1167 Default is 1 (enabled)
1169 l2cr= [PPC]
1171 l3cr= [PPC]
1173 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1174 disabled it.
1176 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1177 in C2 power state.
1179 libata.dma= [LIBATA] DMA control
1180 libata.dma=0 Disable all PATA and SATA DMA
1181 libata.dma=1 PATA and SATA Disk DMA only
1182 libata.dma=2 ATAPI (CDROM) DMA only
1183 libata.dma=4 Compact Flash DMA only
1184 Combinations also work, so libata.dma=3 enables DMA
1185 for disks and CDROMs, but not CFs.
1187 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1188 libata.ignore_hpa=0 keep BIOS limits (default)
1189 libata.ignore_hpa=1 ignore limits, using full disk
1191 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1192 when set.
1193 Format: <int>
1195 libata.force= [LIBATA] Force configurations. The format is comma
1196 separated list of "[ID:]VAL" where ID is
1197 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1198 matching port, link or device. Basically, it matches
1199 the ATA ID string printed on console by libata. If
1200 the whole ID part is omitted, the last PORT and DEVICE
1201 values are used. If ID hasn't been specified yet, the
1202 configuration applies to all ports, links and devices.
1204 If only DEVICE is omitted, the parameter applies to
1205 the port and all links and devices behind it. DEVICE
1206 number of 0 either selects the first device or the
1207 first fan-out link behind PMP device. It does not
1208 select the host link. DEVICE number of 15 selects the
1209 host link and device attached to it.
1211 The VAL specifies the configuration to force. As long
1212 as there's no ambiguity shortcut notation is allowed.
1213 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1214 The following configurations can be forced.
1216 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1217 Any ID with matching PORT is used.
1219 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1221 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1222 udma[/][16,25,33,44,66,100,133] notation is also
1223 allowed.
1225 * [no]ncq: Turn on or off NCQ.
1227 * nohrst, nosrst, norst: suppress hard, soft
1228 and both resets.
1230 If there are multiple matching configurations changing
1231 the same attribute, the last one is used.
1233 lmb=debug [KNL] Enable lmb debug messages.
1235 load_ramdisk= [RAM] List of ramdisks to load from floppy
1236 See Documentation/blockdev/ramdisk.txt.
1238 lockd.nlm_grace_period=P [NFS] Assign grace period.
1239 Format: <integer>
1241 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1242 Format: <integer>
1244 lockd.nlm_timeout=T [NFS] Assign timeout value.
1245 Format: <integer>
1247 lockd.nlm_udpport=M [NFS] Assign UDP port.
1248 Format: <integer>
1250 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1251 Format: <irq>
1253 loglevel= All Kernel Messages with a loglevel smaller than the
1254 console loglevel will be printed to the console. It can
1255 also be changed with klogd or other programs. The
1256 loglevels are defined as follows:
1258 0 (KERN_EMERG) system is unusable
1259 1 (KERN_ALERT) action must be taken immediately
1260 2 (KERN_CRIT) critical conditions
1261 3 (KERN_ERR) error conditions
1262 4 (KERN_WARNING) warning conditions
1263 5 (KERN_NOTICE) normal but significant condition
1264 6 (KERN_INFO) informational
1265 7 (KERN_DEBUG) debug-level messages
1267 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1268 Format: { n | nk | nM }
1269 n must be a power of two. The default size
1270 is set in the kernel config file.
1272 logo.nologo [FB] Disables display of the built-in Linux logo.
1273 This may be used to provide more screen space for
1274 kernel log messages and is useful when debugging
1275 kernel boot problems.
1277 lp=0 [LP] Specify parallel ports to use, e.g,
1278 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1279 lp=reset first parallel port). 'lp=0' disables the
1280 lp=auto printer driver. 'lp=reset' (which can be
1281 specified in addition to the ports) causes
1282 attached printers to be reset. Using
1283 lp=port1,port2,... specifies the parallel ports
1284 to associate lp devices with, starting with
1285 lp0. A port specification may be 'none' to skip
1286 that lp device, or a parport name such as
1287 'parport0'. Specifying 'lp=auto' instead of a
1288 port specification list means that device IDs
1289 from each port should be examined, to see if
1290 an IEEE 1284-compliant printer is attached; if
1291 so, the driver will manage that printer.
1292 See also header of drivers/char/lp.c.
1294 lpj=n [KNL]
1295 Sets loops_per_jiffy to given constant, thus avoiding
1296 time-consuming boot-time autodetection (up to 250 ms per
1297 CPU). 0 enables autodetection (default). To determine
1298 the correct value for your kernel, boot with normal
1299 autodetection and see what value is printed. Note that
1300 on SMP systems the preset will be applied to all CPUs,
1301 which is likely to cause problems if your CPUs need
1302 significantly divergent settings. An incorrect value
1303 will cause delays in the kernel to be wrong, leading to
1304 unpredictable I/O errors and other breakage. Although
1305 unlikely, in the extreme case this might damage your
1306 hardware.
1308 ltpc= [NET]
1309 Format: <io>,<irq>,<dma>
1311 mac5380= [HW,SCSI] Format:
1312 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1314 machvec= [IA64] Force the use of a particular machine-vector
1315 (machvec) in a generic kernel.
1316 Example: machvec=hpzx1_swiotlb
1318 machtype= [Loongson] Share the same kernel image file between different
1319 yeeloong laptop.
1320 Example: machtype=lemote-yeeloong-2f-7inch
1322 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1323 than or equal to this physical address is ignored.
1325 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1326 should make use of. maxcpus=n : n >= 0 limits the
1327 kernel to using 'n' processors. n=0 is a special case,
1328 it is equivalent to "nosmp", which also disables
1329 the IO APIC.
1331 max_loop= [LOOP] Maximum number of loopback devices that can
1332 be mounted
1333 Format: <1-256>
1335 max_luns= [SCSI] Maximum number of LUNs to probe.
1336 Should be between 1 and 2^32-1.
1338 max_report_luns=
1339 [SCSI] Maximum number of LUNs received.
1340 Should be between 1 and 16384.
1342 mcatest= [IA-64]
1344 mce [X86-32] Machine Check Exception
1346 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1348 md= [HW] RAID subsystems devices and level
1349 See Documentation/md.txt.
1351 mdacon= [MDA]
1352 Format: <first>,<last>
1353 Specifies range of consoles to be captured by the MDA.
1355 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1356 Amount of memory to be used when the kernel is not able
1357 to see the whole system memory or for test.
1358 [X86-32] Use together with memmap= to avoid physical
1359 address space collisions. Without memmap= PCI devices
1360 could be placed at addresses belonging to unused RAM.
1362 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1363 memory.
1365 memchunk=nn[KMG]
1366 [KNL,SH] Allow user to override the default size for
1367 per-device physically contiguous DMA buffers.
1369 memmap=exactmap [KNL,X86] Enable setting of an exact
1370 E820 memory map, as specified by the user.
1371 Such memmap=exactmap lines can be constructed based on
1372 BIOS output or other requirements. See the memmap=nn@ss
1373 option description.
1375 memmap=nn[KMG]@ss[KMG]
1376 [KNL] Force usage of a specific region of memory
1377 Region of memory to be used, from ss to ss+nn.
1379 memmap=nn[KMG]#ss[KMG]
1380 [KNL,ACPI] Mark specific memory as ACPI data.
1381 Region of memory to be used, from ss to ss+nn.
1383 memmap=nn[KMG]$ss[KMG]
1384 [KNL,ACPI] Mark specific memory as reserved.
1385 Region of memory to be used, from ss to ss+nn.
1386 Example: Exclude memory from 0x18690000-0x1869ffff
1387 memmap=64K$0x18690000
1388 or
1389 memmap=0x10000$0x18690000
1391 memory_corruption_check=0/1 [X86]
1392 Some BIOSes seem to corrupt the first 64k of
1393 memory when doing things like suspend/resume.
1394 Setting this option will scan the memory
1395 looking for corruption. Enabling this will
1396 both detect corruption and prevent the kernel
1397 from using the memory being corrupted.
1398 However, its intended as a diagnostic tool; if
1399 repeatable BIOS-originated corruption always
1400 affects the same memory, you can use memmap=
1401 to prevent the kernel from using that memory.
1403 memory_corruption_check_size=size [X86]
1404 By default it checks for corruption in the low
1405 64k, making this memory unavailable for normal
1406 use. Use this parameter to scan for
1407 corruption in more or less memory.
1409 memory_corruption_check_period=seconds [X86]
1410 By default it checks for corruption every 60
1411 seconds. Use this parameter to check at some
1412 other rate. 0 disables periodic checking.
1414 memtest= [KNL,X86] Enable memtest
1415 Format: <integer>
1416 default : 0 <disable>
1417 Specifies the number of memtest passes to be
1418 performed. Each pass selects another test
1419 pattern from a given set of patterns. Memtest
1420 fills the memory with this pattern, validates
1421 memory contents and reserves bad memory
1422 regions that are detected.
1424 meye.*= [HW] Set MotionEye Camera parameters
1425 See Documentation/video4linux/meye.txt.
1427 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1428 Multi-Function General Purpose Timers on AMD Geode
1429 platforms.
1431 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1432 the BIOS has incorrectly applied a workaround. TinyBIOS
1433 version 0.98 is known to be affected, 0.99 fixes the
1434 problem by letting the user disable the workaround.
1436 mga= [HW,DRM]
1438 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1439 physical address is ignored.
1441 mini2440= [ARM,HW,KNL]
1442 Format:[0..2][b][c][t]
1443 Default: "0tb"
1444 MINI2440 configuration specification:
1445 0 - The attached screen is the 3.5" TFT
1446 1 - The attached screen is the 7" TFT
1447 2 - The VGA Shield is attached (1024x768)
1448 Leaving out the screen size parameter will not load
1449 the TFT driver, and the framebuffer will be left
1450 unconfigured.
1451 b - Enable backlight. The TFT backlight pin will be
1452 linked to the kernel VESA blanking code and a GPIO
1453 LED. This parameter is not necessary when using the
1454 VGA shield.
1455 c - Enable the s3c camera interface.
1456 t - Reserved for enabling touchscreen support. The
1457 touchscreen support is not enabled in the mainstream
1458 kernel as of 2.6.30, a preliminary port can be found
1459 in the "bleeding edge" mini2440 support kernel at
1460 http://repo.or.cz/w/linux-2.6/mini2440.git
1462 mminit_loglevel=
1463 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1464 parameter allows control of the logging verbosity for
1465 the additional memory initialisation checks. A value
1466 of 0 disables mminit logging and a level of 4 will
1467 log everything. Information is printed at KERN_DEBUG
1468 so loglevel=8 may also need to be specified.
1470 mousedev.tap_time=
1471 [MOUSE] Maximum time between finger touching and
1472 leaving touchpad surface for touch to be considered
1473 a tap and be reported as a left button click (for
1474 touchpads working in absolute mode only).
1475 Format: <msecs>
1476 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1477 reporting absolute coordinates, such as tablets
1478 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1479 reporting absolute coordinates, such as tablets
1481 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1482 is similar to kernelcore except it specifies the
1483 amount of memory used for migratable allocations.
1484 If both kernelcore and movablecore is specified,
1485 then kernelcore will be at *least* the specified
1486 value but may be more. If movablecore on its own
1487 is specified, the administrator must be careful
1488 that the amount of memory usable for all allocations
1489 is not too small.
1491 mpu401= [HW,OSS]
1492 Format: <io>,<irq>
1494 MTD_Partition= [MTD]
1495 Format: <name>,<region-number>,<size>,<offset>
1497 MTD_Region= [MTD] Format:
1498 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1500 mtdparts= [MTD]
1501 See drivers/mtd/cmdlinepart.c.
1503 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1505 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1507 boundary - index of last SLC block on Flex-OneNAND.
1508 The remaining blocks are configured as MLC blocks.
1509 lock - Configure if Flex-OneNAND boundary should be locked.
1510 Once locked, the boundary cannot be changed.
1511 1 indicates lock status, 0 indicates unlock status.
1513 mtdset= [ARM]
1514 ARM/S3C2412 JIVE boot control
1516 See arch/arm/mach-s3c2412/mach-jive.c
1518 mtouchusb.raw_coordinates=
1519 [HW] Make the MicroTouch USB driver use raw coordinates
1520 ('y', default) or cooked coordinates ('n')
1522 mtrr_chunk_size=nn[KMG] [X86]
1523 used for mtrr cleanup. It is largest continuous chunk
1524 that could hold holes aka. UC entries.
1526 mtrr_gran_size=nn[KMG] [X86]
1527 Used for mtrr cleanup. It is granularity of mtrr block.
1528 Default is 1.
1529 Large value could prevent small alignment from
1530 using up MTRRs.
1532 mtrr_spare_reg_nr=n [X86]
1533 Format: <integer>
1534 Range: 0,7 : spare reg number
1535 Default : 1
1536 Used for mtrr cleanup. It is spare mtrr entries number.
1537 Set to 2 or more if your graphical card needs more.
1539 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1541 NCR_D700= [HW,SCSI]
1542 See header of drivers/scsi/NCR_D700.c.
1544 ncr5380= [HW,SCSI]
1546 ncr53c400= [HW,SCSI]
1548 ncr53c400a= [HW,SCSI]
1550 ncr53c406a= [HW,SCSI]
1552 ncr53c8xx= [HW,SCSI]
1554 netdev= [NET] Network devices parameters
1555 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1556 Note that mem_start is often overloaded to mean
1557 something different and driver-specific.
1558 This usage is only documented in each driver source
1559 file if at all.
1561 nf_conntrack.acct=
1562 [NETFILTER] Enable connection tracking flow accounting
1563 0 to disable accounting
1564 1 to enable accounting
1565 Default value depends on CONFIG_NF_CT_ACCT that is
1566 going to be removed in 2.6.29.
1568 nfsaddrs= [NFS]
1569 See Documentation/filesystems/nfs/nfsroot.txt.
1571 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1572 See Documentation/filesystems/nfs/nfsroot.txt.
1574 nfs.callback_tcpport=
1575 [NFS] set the TCP port on which the NFSv4 callback
1576 channel should listen.
1578 nfs.cache_getent=
1579 [NFS] sets the pathname to the program which is used
1580 to update the NFS client cache entries.
1582 nfs.cache_getent_timeout=
1583 [NFS] sets the timeout after which an attempt to
1584 update a cache entry is deemed to have failed.
1586 nfs.idmap_cache_timeout=
1587 [NFS] set the maximum lifetime for idmapper cache
1588 entries.
1590 nfs.enable_ino64=
1591 [NFS] enable 64-bit inode numbers.
1592 If zero, the NFS client will fake up a 32-bit inode
1593 number for the readdir() and stat() syscalls instead
1594 of returning the full 64-bit number.
1595 The default is to return 64-bit inode numbers.
1597 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1598 when a NMI is triggered.
1599 Format: [state][,regs][,debounce][,die]
1601 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1602 Format: [panic,][num]
1603 Valid num: 0,1,2
1604 0 - turn nmi_watchdog off
1605 1 - use the IO-APIC timer for the NMI watchdog
1606 2 - use the local APIC for the NMI watchdog using
1607 a performance counter. Note: This will use one
1608 performance counter and the local APIC's performance
1609 vector.
1610 When panic is specified, panic when an NMI watchdog
1611 timeout occurs.
1612 This is useful when you use a panic=... timeout and
1613 need the box quickly up again.
1614 Instead of 1 and 2 it is possible to use the following
1615 symbolic names: lapic and ioapic
1616 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1618 netpoll.carrier_timeout=
1619 [NET] Specifies amount of time (in seconds) that
1620 netpoll should wait for a carrier. By default netpoll
1621 waits 4 seconds.
1623 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1624 emulation library even if a 387 maths coprocessor
1625 is present.
1627 no_console_suspend
1628 [HW] Never suspend the console
1629 Disable suspending of consoles during suspend and
1630 hibernate operations. Once disabled, debugging
1631 messages can reach various consoles while the rest
1632 of the system is being put to sleep (ie, while
1633 debugging driver suspend/resume hooks). This may
1634 not work reliably with all consoles, but is known
1635 to work with serial and VGA consoles.
1637 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1638 caches in the slab allocator. Saves per-node memory,
1639 but will impact performance.
1641 noalign [KNL,ARM]
1643 noapic [SMP,APIC] Tells the kernel to not make use of any
1644 IOAPICs that may be present in the system.
1646 nobats [PPC] Do not use BATs for mapping kernel lowmem
1647 on "Classic" PPC cores.
1649 nocache [ARM]
1651 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1653 nodelayacct [KNL] Disable per-task delay accounting
1655 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1657 nodsp [SH] Disable hardware DSP at boot time.
1659 noefi [X86] Disable EFI runtime services support.
1661 noexec [IA-64]
1663 noexec [X86]
1664 On X86-32 available only on PAE configured kernels.
1665 noexec=on: enable non-executable mappings (default)
1666 noexec=off: disable non-executable mappings
1668 noexec32 [X86-64]
1669 This affects only 32-bit executables.
1670 noexec32=on: enable non-executable mappings (default)
1671 read doesn't imply executable mappings
1672 noexec32=off: disable non-executable mappings
1673 read implies executable mappings
1675 nofpu [SH] Disable hardware FPU at boot time.
1677 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1678 register save and restore. The kernel will only save
1679 legacy floating-point registers on task switch.
1681 noxsave [BUGS=X86] Disables x86 extended register state save
1682 and restore using xsave. The kernel will fallback to
1683 enabling legacy floating-point and sse state.
1685 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1686 wfi(ARM) instruction doesn't work correctly and not to
1687 use it. This is also useful when using JTAG debugger.
1689 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1690 instruction doesn't work correctly and not to
1691 use it.
1693 no_file_caps Tells the kernel not to honor file capabilities. The
1694 only way then for a file to be executed with privilege
1695 is to be setuid root or executed by root.
1697 nohalt [IA-64] Tells the kernel not to use the power saving
1698 function PAL_HALT_LIGHT when idle. This increases
1699 power-consumption. On the positive side, it reduces
1700 interrupt wake-up latency, which may improve performance
1701 in certain environments such as networked servers or
1702 real-time systems.
1704 nohz= [KNL] Boottime enable/disable dynamic ticks
1705 Valid arguments: on, off
1706 Default: on
1708 noiotrap [SH] Disables trapped I/O port accesses.
1710 noirqdebug [X86-32] Disables the code which attempts to detect and
1711 disable unhandled interrupt sources.
1713 no_timer_check [X86,APIC] Disables the code which tests for
1714 broken timer IRQ sources.
1716 noisapnp [ISAPNP] Disables ISA PnP code.
1718 noinitrd [RAM] Tells the kernel not to load any configured
1719 initial RAM disk.
1721 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1722 remapping.
1724 nointroute [IA-64]
1726 nojitter [IA64] Disables jitter checking for ITC timers.
1728 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1730 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1732 noltlbs [PPC] Do not use large page/tlb entries for kernel
1733 lowmem mapping on PPC40x.
1735 nomca [IA-64] Disable machine check abort handling
1737 nomce [X86-32] Machine Check Exception
1739 nomfgpt [X86-32] Disable Multi-Function General Purpose
1740 Timer usage (for AMD Geode machines).
1742 nopat [X86] Disable PAT (page attribute table extension of
1743 pagetables) support.
1745 norandmaps Don't use address space randomization. Equivalent to
1746 echo 0 > /proc/sys/kernel/randomize_va_space
1748 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1750 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1751 with UP alternatives
1753 noresidual [PPC] Don't use residual data on PReP machines.
1755 noresume [SWSUSP] Disables resume and restores original swap
1756 space.
1758 no-scroll [VGA] Disables scrollback.
1759 This is required for the Braillex ib80-piezo Braille
1760 reader made by F.H. Papenmeier (Germany).
1762 nosbagart [IA-64]
1764 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1766 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1767 and disable the IO APIC. legacy for "maxcpus=0".
1769 nosoftlockup [KNL] Disable the soft-lockup detector.
1771 noswapaccount [KNL] Disable accounting of swap in memory resource
1772 controller. (See Documentation/cgroups/memory.txt)
1774 nosync [HW,M68K] Disables sync negotiation for all devices.
1776 notsc [BUGS=X86-32] Disable Time Stamp Counter
1778 nousb [USB] Disable the USB subsystem
1780 nowb [ARM]
1782 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1784 nptcg= [IA64] Override max number of concurrent global TLB
1785 purges which is reported from either PAL_VM_SUMMARY or
1786 SAL PALO.
1788 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1789 could support. nr_cpus=n : n >= 1 limits the kernel to
1790 supporting 'n' processors. Later in runtime you can not
1791 use hotplug cpu feature to put more cpu back to online.
1792 just like you compile the kernel NR_CPUS=n
1794 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1796 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1797 one of ['zone', 'node', 'default'] can be specified
1798 This can be set from sysctl after boot.
1799 See Documentation/sysctl/vm.txt for details.
1801 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1802 See Documentation/debugging-via-ohci1394.txt for more
1803 info.
1805 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1806 Rather than timing out after 20 ms if an EC
1807 command is not properly ACKed, override the length
1808 of the timeout. We have interrupts disabled while
1809 waiting for the ACK, so if this is set too high
1810 interrupts *may* be lost!
1812 omap_mux= [OMAP] Override bootloader pin multiplexing.
1813 Format: <mux_mode0.mode_name=value>...
1814 For example, to override I2C bus2:
1815 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1817 opl3= [HW,OSS]
1818 Format: <io>
1820 oprofile.timer= [HW]
1821 Use timer interrupt instead of performance counters
1823 oprofile.cpu_type= Force an oprofile cpu type
1824 This might be useful if you have an older oprofile
1825 userland or if you want common events.
1826 Format: { arch_perfmon }
1827 arch_perfmon: [X86] Force use of architectural
1828 perfmon on Intel CPUs instead of the
1829 CPU specific event set.
1831 osst= [HW,SCSI] SCSI Tape Driver
1832 Format: <buffer_size>,<write_threshold>
1833 See also Documentation/scsi/st.txt.
1835 panic= [KNL] Kernel behaviour on panic
1836 Format: <timeout>
1838 parkbd.port= [HW] Parallel port number the keyboard adapter is
1839 connected to, default is 0.
1840 Format: <parport#>
1841 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1842 0 for XT, 1 for AT (default is AT).
1843 Format: <mode>
1845 parport= [HW,PPT] Specify parallel ports. 0 disables.
1846 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1847 Use 'auto' to force the driver to use any
1848 IRQ/DMA settings detected (the default is to
1849 ignore detected IRQ/DMA settings because of
1850 possible conflicts). You can specify the base
1851 address, IRQ, and DMA settings; IRQ and DMA
1852 should be numbers, or 'auto' (for using detected
1853 settings on that particular port), or 'nofifo'
1854 (to avoid using a FIFO even if it is detected).
1855 Parallel ports are assigned in the order they
1856 are specified on the command line, starting
1857 with parport0.
1859 parport_init_mode= [HW,PPT]
1860 Configure VIA parallel port to operate in
1861 a specific mode. This is necessary on Pegasos
1862 computer where firmware has no options for setting
1863 up parallel port mode and sets it to spp.
1864 Currently this function knows 686a and 8231 chips.
1865 Format: [spp|ps2|epp|ecp|ecpepp]
1867 pas2= [HW,OSS] Format:
1868 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1870 pas16= [HW,SCSI]
1871 See header of drivers/scsi/pas16.c.
1873 pause_on_oops=
1874 Halt all CPUs after the first oops has been printed for
1875 the specified number of seconds. This is to be used if
1876 your oopses keep scrolling off the screen.
1878 pcbit= [HW,ISDN]
1880 pcd. [PARIDE]
1881 See header of drivers/block/paride/pcd.c.
1882 See also Documentation/blockdev/paride.txt.
1884 pci=option[,option...] [PCI] various PCI subsystem options:
1885 earlydump [X86] dump PCI config space before the kernel
1886 changes anything
1887 off [X86] don't probe for the PCI bus
1888 bios [X86-32] force use of PCI BIOS, don't access
1889 the hardware directly. Use this if your machine
1890 has a non-standard PCI host bridge.
1891 nobios [X86-32] disallow use of PCI BIOS, only direct
1892 hardware access methods are allowed. Use this
1893 if you experience crashes upon bootup and you
1894 suspect they are caused by the BIOS.
1895 conf1 [X86] Force use of PCI Configuration
1896 Mechanism 1.
1897 conf2 [X86] Force use of PCI Configuration
1898 Mechanism 2.
1899 noaer [PCIE] If the PCIEAER kernel config parameter is
1900 enabled, this kernel boot option can be used to
1901 disable the use of PCIE advanced error reporting.
1902 nodomains [PCI] Disable support for multiple PCI
1903 root domains (aka PCI segments, in ACPI-speak).
1904 nommconf [X86] Disable use of MMCONFIG for PCI
1905 Configuration
1906 check_enable_amd_mmconf [X86] check for and enable
1907 properly configured MMIO access to PCI
1908 config space on AMD family 10h CPU
1909 nomsi [MSI] If the PCI_MSI kernel config parameter is
1910 enabled, this kernel boot option can be used to
1911 disable the use of MSI interrupts system-wide.
1912 noioapicquirk [APIC] Disable all boot interrupt quirks.
1913 Safety option to keep boot IRQs enabled. This
1914 should never be necessary.
1915 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1916 primary IO-APIC for bridges that cannot disable
1917 boot IRQs. This fixes a source of spurious IRQs
1918 when the system masks IRQs.
1919 noioapicreroute [APIC] Disable workaround that uses the
1920 boot IRQ equivalent of an IRQ that connects to
1921 a chipset where boot IRQs cannot be disabled.
1922 The opposite of ioapicreroute.
1923 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1924 routing table. These calls are known to be buggy
1925 on several machines and they hang the machine
1926 when used, but on other computers it's the only
1927 way to get the interrupt routing table. Try
1928 this option if the kernel is unable to allocate
1929 IRQs or discover secondary PCI buses on your
1930 motherboard.
1931 rom [X86] Assign address space to expansion ROMs.
1932 Use with caution as certain devices share
1933 address decoders between ROMs and other
1934 resources.
1935 norom [X86] Do not assign address space to
1936 expansion ROMs that do not already have
1937 BIOS assigned address ranges.
1938 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1939 assigned automatically to PCI devices. You can
1940 make the kernel exclude IRQs of your ISA cards
1941 this way.
1942 pirqaddr=0xAAAAA [X86] Specify the physical address
1943 of the PIRQ table (normally generated
1944 by the BIOS) if it is outside the
1945 F0000h-100000h range.
1946 lastbus=N [X86] Scan all buses thru bus #N. Can be
1947 useful if the kernel is unable to find your
1948 secondary buses and you want to tell it
1949 explicitly which ones they are.
1950 assign-busses [X86] Always assign all PCI bus
1951 numbers ourselves, overriding
1952 whatever the firmware may have done.
1953 usepirqmask [X86] Honor the possible IRQ mask stored
1954 in the BIOS $PIR table. This is needed on
1955 some systems with broken BIOSes, notably
1956 some HP Pavilion N5400 and Omnibook XE3
1957 notebooks. This will have no effect if ACPI
1958 IRQ routing is enabled.
1959 noacpi [X86] Do not use ACPI for IRQ routing
1960 or for PCI scanning.
1961 use_crs [X86] Use PCI host bridge window information
1962 from ACPI. On BIOSes from 2008 or later, this
1963 is enabled by default. If you need to use this,
1964 please report a bug.
1965 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1966 If you need to use this, please report a bug.
1967 routeirq Do IRQ routing for all PCI devices.
1968 This is normally done in pci_enable_device(),
1969 so this option is a temporary workaround
1970 for broken drivers that don't call it.
1971 skip_isa_align [X86] do not align io start addr, so can
1972 handle more pci cards
1973 firmware [ARM] Do not re-enumerate the bus but instead
1974 just use the configuration from the
1975 bootloader. This is currently used on
1976 IXP2000 systems where the bus has to be
1977 configured a certain way for adjunct CPUs.
1978 noearly [X86] Don't do any early type 1 scanning.
1979 This might help on some broken boards which
1980 machine check when some devices' config space
1981 is read. But various workarounds are disabled
1982 and some IOMMU drivers will not work.
1983 bfsort Sort PCI devices into breadth-first order.
1984 This sorting is done to get a device
1985 order compatible with older (<= 2.4) kernels.
1986 nobfsort Don't sort PCI devices into breadth-first order.
1987 cbiosize=nn[KMG] The fixed amount of bus space which is
1988 reserved for the CardBus bridge's IO window.
1989 The default value is 256 bytes.
1990 cbmemsize=nn[KMG] The fixed amount of bus space which is
1991 reserved for the CardBus bridge's memory
1992 window. The default value is 64 megabytes.
1993 resource_alignment=
1994 Format:
1995 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
1996 Specifies alignment and device to reassign
1997 aligned memory resources.
1998 If <order of align> is not specified,
1999 PAGE_SIZE is used as alignment.
2000 PCI-PCI bridge can be specified, if resource
2001 windows need to be expanded.
2002 ecrc= Enable/disable PCIe ECRC (transaction layer
2003 end-to-end CRC checking).
2004 bios: Use BIOS/firmware settings. This is the
2005 the default.
2006 off: Turn ECRC off
2007 on: Turn ECRC on.
2009 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2010 Management.
2011 off Disable ASPM.
2012 force Enable ASPM even on devices that claim not to support it.
2013 WARNING: Forcing ASPM on may cause system lockups.
2015 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2016 Format: {auto|force}[,nomsi]
2017 auto Use native PCIe PME signaling if the BIOS allows the
2018 kernel to control PCIe config registers of root ports.
2019 force Use native PCIe PME signaling even if the BIOS refuses
2020 to allow the kernel to control the relevant PCIe config
2021 registers.
2022 nomsi Do not use MSI for native PCIe PME signaling (this makes
2023 all PCIe root ports use INTx for everything).
2025 pcmv= [HW,PCMCIA] BadgePAD 4
2027 pd. [PARIDE]
2028 See Documentation/blockdev/paride.txt.
2030 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2031 boot time.
2032 Format: { 0 | 1 }
2033 See arch/parisc/kernel/pdc_chassis.c
2035 percpu_alloc= Select which percpu first chunk allocator to use.
2036 Currently supported values are "embed" and "page".
2037 Archs may support subset or none of the selections.
2038 See comments in mm/percpu.c for details on each
2039 allocator. This parameter is primarily for debugging
2040 and performance comparison.
2042 pf. [PARIDE]
2043 See Documentation/blockdev/paride.txt.
2045 pg. [PARIDE]
2046 See Documentation/blockdev/paride.txt.
2048 pirq= [SMP,APIC] Manual mp-table setup
2049 See Documentation/x86/i386/IO-APIC.txt.
2051 plip= [PPT,NET] Parallel port network link
2052 Format: { parport<nr> | timid | 0 }
2053 See also Documentation/parport.txt.
2055 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2056 Override pmtimer IOPort with a hex value.
2057 e.g. pmtmr=0x508
2059 pnp.debug [PNP]
2060 Enable PNP debug messages. This depends on the
2061 CONFIG_PNP_DEBUG_MESSAGES option.
2063 pnpacpi= [ACPI]
2064 { off }
2066 pnpbios= [ISAPNP]
2067 { on | off | curr | res | no-curr | no-res }
2069 pnp_reserve_irq=
2070 [ISAPNP] Exclude IRQs for the autoconfiguration
2072 pnp_reserve_dma=
2073 [ISAPNP] Exclude DMAs for the autoconfiguration
2075 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2076 Ranges are in pairs (I/O port base and size).
2078 pnp_reserve_mem=
2079 [ISAPNP] Exclude memory regions for the
2080 autoconfiguration.
2081 Ranges are in pairs (memory base and size).
2083 ports= [IP_VS_FTP] IPVS ftp helper module
2084 Default is 21.
2085 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2086 may be specified.
2087 Format: <port>,<port>....
2089 print-fatal-signals=
2090 [KNL] debug: print fatal signals
2092 If enabled, warn about various signal handling
2093 related application anomalies: too many signals,
2094 too many POSIX.1 timers, fatal signals causing a
2095 coredump - etc.
2097 If you hit the warning due to signal overflow,
2098 you might want to try "ulimit -i unlimited".
2100 default: off.
2102 printk.time= Show timing data prefixed to each printk message line
2103 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2105 processor.max_cstate= [HW,ACPI]
2106 Limit processor to maximum C-state
2107 max_cstate=9 overrides any DMI blacklist limit.
2109 processor.nocst [HW,ACPI]
2110 Ignore the _CST method to determine C-states,
2111 instead using the legacy FADT method
2113 profile= [KNL] Enable kernel profiling via /proc/profile
2114 Format: [schedule,]<number>
2115 Param: "schedule" - profile schedule points.
2116 Param: <number> - step/bucket size as a power of 2 for
2117 statistical time based profiling.
2118 Param: "sleep" - profile D-state sleeping (millisecs).
2119 Requires CONFIG_SCHEDSTATS
2120 Param: "kvm" - profile VM exits.
2122 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2123 before loading.
2124 See Documentation/blockdev/ramdisk.txt.
2126 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2127 probe for; one of (bare|imps|exps|lifebook|any).
2128 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2129 per second.
2130 psmouse.resetafter= [HW,MOUSE]
2131 Try to reset the device after so many bad packets
2132 (0 = never).
2133 psmouse.resolution=
2134 [HW,MOUSE] Set desired mouse resolution, in dpi.
2135 psmouse.smartscroll=
2136 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2137 0 = disabled, 1 = enabled (default).
2139 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2140 Format:
2141 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2143 pt. [PARIDE]
2144 See Documentation/blockdev/paride.txt.
2146 pty.legacy_count=
2147 [KNL] Number of legacy pty's. Overwrites compiled-in
2148 default number.
2150 quiet [KNL] Disable most log messages
2152 r128= [HW,DRM]
2154 raid= [HW,RAID]
2155 See Documentation/md.txt.
2157 ramdisk_blocksize= [RAM]
2158 See Documentation/blockdev/ramdisk.txt.
2160 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2161 See Documentation/blockdev/ramdisk.txt.
2163 rcupdate.blimit= [KNL,BOOT]
2164 Set maximum number of finished RCU callbacks to process
2165 in one batch.
2167 rcupdate.qhimark= [KNL,BOOT]
2168 Set threshold of queued
2169 RCU callbacks over which batch limiting is disabled.
2171 rcupdate.qlowmark= [KNL,BOOT]
2172 Set threshold of queued RCU callbacks below which
2173 batch limiting is re-enabled.
2175 rdinit= [KNL]
2176 Format: <full_path>
2177 Run specified binary instead of /init from the ramdisk,
2178 used for early userspace startup. See initrd.
2180 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2181 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2182 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2184 relax_domain_level=
2185 [KNL, SMP] Set scheduler's default relax_domain_level.
2186 See Documentation/cgroups/cpusets.txt.
2188 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2190 reservetop= [X86-32]
2191 Format: nn[KMG]
2192 Reserves a hole at the top of the kernel virtual
2193 address space.
2195 reset_devices [KNL] Force drivers to reset the underlying device
2196 during initialization.
2198 resume= [SWSUSP]
2199 Specify the partition device for software suspend
2201 resume_offset= [SWSUSP]
2202 Specify the offset from the beginning of the partition
2203 given by "resume=" at which the swap header is located,
2204 in <PAGE_SIZE> units (needed only for swap files).
2205 See Documentation/power/swsusp-and-swap-files.txt
2207 retain_initrd [RAM] Keep initrd memory after extraction
2209 rhash_entries= [KNL,NET]
2210 Set number of hash buckets for route cache
2212 riscom8= [HW,SERIAL]
2213 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2215 ro [KNL] Mount root device read-only on boot
2217 root= [KNL] Root filesystem
2219 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2220 mount the root filesystem
2222 rootflags= [KNL] Set root filesystem mount option string
2224 rootfstype= [KNL] Set root filesystem type
2226 rootwait [KNL] Wait (indefinitely) for root device to show up.
2227 Useful for devices that are detected asynchronously
2228 (e.g. USB and MMC devices).
2230 rw [KNL] Mount root device read-write on boot
2232 S [KNL] Run init in single mode
2234 sa1100ir [NET]
2235 See drivers/net/irda/sa1100_ir.c.
2237 sbni= [NET] Granch SBNI12 leased line adapter
2239 sched_debug [KNL] Enables verbose scheduler debug messages.
2241 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2242 Format: <io>[,<timeout>[,<isapnp>]]
2244 scsi_debug_*= [SCSI]
2245 See drivers/scsi/scsi_debug.c.
2247 scsi_default_dev_flags=
2248 [SCSI] SCSI default device flags
2249 Format: <integer>
2251 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2252 Format: <vendor>:<model>:<flags>
2253 (flags are integer value)
2255 scsi_logging_level= [SCSI] a bit mask of logging levels
2256 See drivers/scsi/scsi_logging.h for bits. Also
2257 settable via sysctl at dev.scsi.logging_level
2258 (/proc/sys/dev/scsi/logging_level).
2259 There is also a nice 'scsi_logging_level' script in the
2260 S390-tools package, available for download at
2261 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2263 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2264 discovered. async scans them in kernel threads,
2265 allowing boot to proceed. none ignores them, expecting
2266 user space to do the scan.
2268 security= [SECURITY] Choose a security module to enable at boot.
2269 If this boot parameter is not specified, only the first
2270 security module asking for security registration will be
2271 loaded. An invalid security module name will be treated
2272 as if no module has been chosen.
2274 selinux= [SELINUX] Disable or enable SELinux at boot time.
2275 Format: { "0" | "1" }
2276 See security/selinux/Kconfig help text.
2277 0 -- disable.
2278 1 -- enable.
2279 Default value is set via kernel config option.
2280 If enabled at boot time, /selinux/disable can be used
2281 later to disable prior to initial policy load.
2283 serialnumber [BUGS=X86-32]
2285 shapers= [NET]
2286 Maximal number of shapers.
2288 show_msr= [x86] show boot-time MSR settings
2289 Format: { <integer> }
2290 Show boot-time (BIOS-initialized) MSR settings.
2291 The parameter means the number of CPUs to show,
2292 for example 1 means boot CPU only.
2294 sim710= [SCSI,HW]
2295 See header of drivers/scsi/sim710.c.
2297 simeth= [IA-64]
2298 simscsi=
2300 slram= [HW,MTD]
2302 slub_debug[=options[,slabs]] [MM, SLUB]
2303 Enabling slub_debug allows one to determine the
2304 culprit if slab objects become corrupted. Enabling
2305 slub_debug can create guard zones around objects and
2306 may poison objects when not in use. Also tracks the
2307 last alloc / free. For more information see
2308 Documentation/vm/slub.txt.
2310 slub_max_order= [MM, SLUB]
2311 Determines the maximum allowed order for slabs.
2312 A high setting may cause OOMs due to memory
2313 fragmentation. For more information see
2314 Documentation/vm/slub.txt.
2316 slub_min_objects= [MM, SLUB]
2317 The minimum number of objects per slab. SLUB will
2318 increase the slab order up to slub_max_order to
2319 generate a sufficiently large slab able to contain
2320 the number of objects indicated. The higher the number
2321 of objects the smaller the overhead of tracking slabs
2322 and the less frequently locks need to be acquired.
2323 For more information see Documentation/vm/slub.txt.
2325 slub_min_order= [MM, SLUB]
2326 Determines the mininum page order for slabs. Must be
2327 lower than slub_max_order.
2328 For more information see Documentation/vm/slub.txt.
2330 slub_nomerge [MM, SLUB]
2331 Disable merging of slabs with similar size. May be
2332 necessary if there is some reason to distinguish
2333 allocs to different slabs. Debug options disable
2334 merging on their own.
2335 For more information see Documentation/vm/slub.txt.
2337 smart2= [HW]
2338 Format: <io1>[,<io2>[,...,<io8>]]
2340 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2341 attempt to substitute SMP alternatives once at boot.
2343 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2344 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2345 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2346 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2347 smsc-ircc2.ircc_irq= [HW] IRQ line
2348 smsc-ircc2.ircc_dma= [HW] DMA channel
2349 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2350 0: Toshiba Satellite 1800 (GP data pin select)
2351 1: Fast pin select (default)
2352 2: ATC IRMode
2354 snd-ad1816a= [HW,ALSA]
2356 snd-ad1848= [HW,ALSA]
2358 snd-ali5451= [HW,ALSA]
2360 snd-als100= [HW,ALSA]
2362 snd-als4000= [HW,ALSA]
2364 snd-azt2320= [HW,ALSA]
2366 snd-cmi8330= [HW,ALSA]
2368 snd-cmipci= [HW,ALSA]
2370 snd-cs4231= [HW,ALSA]
2372 snd-cs4232= [HW,ALSA]
2374 snd-cs4236= [HW,ALSA]
2376 snd-cs4281= [HW,ALSA]
2378 snd-cs46xx= [HW,ALSA]
2380 snd-dt019x= [HW,ALSA]
2382 snd-dummy= [HW,ALSA]
2384 snd-emu10k1= [HW,ALSA]
2386 snd-ens1370= [HW,ALSA]
2388 snd-ens1371= [HW,ALSA]
2390 snd-es968= [HW,ALSA]
2392 snd-es1688= [HW,ALSA]
2394 snd-es18xx= [HW,ALSA]
2396 snd-es1938= [HW,ALSA]
2398 snd-es1968= [HW,ALSA]
2400 snd-fm801= [HW,ALSA]
2402 snd-gusclassic= [HW,ALSA]
2404 snd-gusextreme= [HW,ALSA]
2406 snd-gusmax= [HW,ALSA]
2408 snd-hdsp= [HW,ALSA]
2410 snd-ice1712= [HW,ALSA]
2412 snd-intel8x0= [HW,ALSA]
2414 snd-interwave= [HW,ALSA]
2416 snd-interwave-stb=
2417 [HW,ALSA]
2419 snd-korg1212= [HW,ALSA]
2421 snd-maestro3= [HW,ALSA]
2423 snd-mpu401= [HW,ALSA]
2425 snd-mtpav= [HW,ALSA]
2427 snd-nm256= [HW,ALSA]
2429 snd-opl3sa2= [HW,ALSA]
2431 snd-opti92x-ad1848=
2432 [HW,ALSA]
2434 snd-opti92x-cs4231=
2435 [HW,ALSA]
2437 snd-opti93x= [HW,ALSA]
2439 snd-pmac= [HW,ALSA]
2441 snd-rme32= [HW,ALSA]
2443 snd-rme96= [HW,ALSA]
2445 snd-rme9652= [HW,ALSA]
2447 snd-sb8= [HW,ALSA]
2449 snd-sb16= [HW,ALSA]
2451 snd-sbawe= [HW,ALSA]
2453 snd-serial= [HW,ALSA]
2455 snd-sgalaxy= [HW,ALSA]
2457 snd-sonicvibes= [HW,ALSA]
2459 snd-sun-amd7930=
2460 [HW,ALSA]
2462 snd-sun-cs4231= [HW,ALSA]
2464 snd-trident= [HW,ALSA]
2466 snd-usb-audio= [HW,ALSA,USB]
2468 snd-via82xx= [HW,ALSA]
2470 snd-virmidi= [HW,ALSA]
2472 snd-wavefront= [HW,ALSA]
2474 snd-ymfpci= [HW,ALSA]
2476 softlockup_panic=
2477 [KNL] Should the soft-lockup detector generate panics.
2479 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2480 See Documentation/sonypi.txt
2482 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2483 See Documentation/serial/specialix.txt.
2485 spia_io_base= [HW,MTD]
2486 spia_fio_base=
2487 spia_pedr=
2488 spia_peddr=
2490 sscape= [HW,OSS]
2491 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2493 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2494 See Documentation/scsi/st.txt.
2496 stacktrace [FTRACE]
2497 Enabled the stack tracer on boot up.
2499 sti= [PARISC,HW]
2500 Format: <num>
2501 Set the STI (builtin display/keyboard on the HP-PARISC
2502 machines) console (graphic card) which should be used
2503 as the initial boot-console.
2504 See also comment in drivers/video/console/sticore.c.
2506 sti_font= [HW]
2507 See comment in drivers/video/console/sticore.c.
2509 stifb= [HW]
2510 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2512 sunrpc.min_resvport=
2513 sunrpc.max_resvport=
2514 [NFS,SUNRPC]
2515 SunRPC servers often require that client requests
2516 originate from a privileged port (i.e. a port in the
2517 range 0 < portnr < 1024).
2518 An administrator who wishes to reserve some of these
2519 ports for other uses may adjust the range that the
2520 kernel's sunrpc client considers to be privileged
2521 using these two parameters to set the minimum and
2522 maximum port values.
2524 sunrpc.pool_mode=
2525 [NFS]
2526 Control how the NFS server code allocates CPUs to
2527 service thread pools. Depending on how many NICs
2528 you have and where their interrupts are bound, this
2529 option will affect which CPUs will do NFS serving.
2530 Note: this parameter cannot be changed while the
2531 NFS server is running.
2533 auto the server chooses an appropriate mode
2534 automatically using heuristics
2535 global a single global pool contains all CPUs
2536 percpu one pool for each CPU
2537 pernode one pool for each NUMA node (equivalent
2538 to global on non-NUMA machines)
2540 sunrpc.tcp_slot_table_entries=
2541 sunrpc.udp_slot_table_entries=
2542 [NFS,SUNRPC]
2543 Sets the upper limit on the number of simultaneous
2544 RPC calls that can be sent from the client to a
2545 server. Increasing these values may allow you to
2546 improve throughput, but will also increase the
2547 amount of memory reserved for use by the client.
2549 swiotlb= [IA-64] Number of I/O TLB slabs
2551 switches= [HW,M68k]
2553 sym53c416= [HW,SCSI]
2554 See header of drivers/scsi/sym53c416.c.
2556 sysrq_always_enabled
2557 [KNL]
2558 Ignore sysrq setting - this boot parameter will
2559 neutralize any effect of /proc/sys/kernel/sysrq.
2560 Useful for debugging.
2562 t128= [HW,SCSI]
2563 See header of drivers/scsi/t128.c.
2565 tdfx= [HW,DRM]
2567 test_suspend= [SUSPEND]
2568 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2569 standby suspend) as the system sleep state to briefly
2570 enter during system startup. The system is woken from
2571 this state using a wakeup-capable RTC alarm.
2573 thash_entries= [KNL,NET]
2574 Set number of hash buckets for TCP connection
2576 thermal.act= [HW,ACPI]
2577 -1: disable all active trip points in all thermal zones
2578 <degrees C>: override all lowest active trip points
2580 thermal.crt= [HW,ACPI]
2581 -1: disable all critical trip points in all thermal zones
2582 <degrees C>: override all critical trip points
2584 thermal.nocrt= [HW,ACPI]
2585 Set to disable actions on ACPI thermal zone
2586 critical and hot trip points.
2588 thermal.off= [HW,ACPI]
2589 1: disable ACPI thermal control
2591 thermal.psv= [HW,ACPI]
2592 -1: disable all passive trip points
2593 <degrees C>: override all passive trip points to this
2594 value
2596 thermal.tzp= [HW,ACPI]
2597 Specify global default ACPI thermal zone polling rate
2598 <deci-seconds>: poll all this frequency
2599 0: no polling (default)
2601 tmscsim= [HW,SCSI]
2602 See comment before function dc390_setup() in
2603 drivers/scsi/tmscsim.c.
2605 topology= [S390]
2606 Format: {off | on}
2607 Specify if the kernel should make use of the cpu
2608 topology informations if the hardware supports these.
2609 The scheduler will make use of these informations and
2610 e.g. base its process migration decisions on it.
2611 Default is off.
2613 tp720= [HW,PS2]
2615 trace_buf_size=nn[KMG]
2616 [FTRACE] will set tracing buffer size.
2618 trace_event=[event-list]
2619 [FTRACE] Set and start specified trace events in order
2620 to facilitate early boot debugging.
2621 See also Documentation/trace/events.txt
2623 trix= [HW,OSS] MediaTrix AudioTrix Pro
2624 Format:
2625 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2627 tsc= Disable clocksource-must-verify flag for TSC.
2628 Format: <string>
2629 [x86] reliable: mark tsc clocksource as reliable, this
2630 disables clocksource verification at runtime.
2631 Used to enable high-resolution timer mode on older
2632 hardware, and in virtualized environment.
2634 turbografx.map[2|3]= [HW,JOY]
2635 TurboGraFX parallel port interface
2636 Format:
2637 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2638 See also Documentation/input/joystick-parport.txt
2640 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2641 See header of drivers/scsi/u14-34f.c.
2643 uart401= [HW,OSS]
2644 Format: <io>,<irq>
2646 uart6850= [HW,OSS]
2647 Format: <io>,<irq>
2649 uhash_entries= [KNL,NET]
2650 Set number of hash buckets for UDP/UDP-Lite connections
2652 uhci-hcd.ignore_oc=
2653 [USB] Ignore overcurrent events (default N).
2654 Some badly-designed motherboards generate lots of
2655 bogus events, for ports that aren't wired to
2656 anything. Set this parameter to avoid log spamming.
2657 Note that genuine overcurrent events won't be
2658 reported either.
2660 unknown_nmi_panic
2661 [X86]
2662 Set unknown_nmi_panic=1 early on boot.
2664 usbcore.autosuspend=
2665 [USB] The autosuspend time delay (in seconds) used
2666 for newly-detected USB devices (default 2). This
2667 is the time required before an idle device will be
2668 autosuspended. Devices for which the delay is set
2669 to a negative value won't be autosuspended at all.
2671 usbcore.usbfs_snoop=
2672 [USB] Set to log all usbfs traffic (default 0 = off).
2674 usbcore.blinkenlights=
2675 [USB] Set to cycle leds on hubs (default 0 = off).
2677 usbcore.old_scheme_first=
2678 [USB] Start with the old device initialization
2679 scheme (default 0 = off).
2681 usbcore.use_both_schemes=
2682 [USB] Try the other device initialization scheme
2683 if the first one fails (default 1 = enabled).
2685 usbcore.initial_descriptor_timeout=
2686 [USB] Specifies timeout for the initial 64-byte
2687 USB_REQ_GET_DESCRIPTOR request in milliseconds
2688 (default 5000 = 5.0 seconds).
2690 usbhid.mousepoll=
2691 [USBHID] The interval which mice are to be polled at.
2693 usb-storage.delay_use=
2694 [UMS] The delay in seconds before a new device is
2695 scanned for Logical Units (default 5).
2697 usb-storage.quirks=
2698 [UMS] A list of quirks entries to supplement or
2699 override the built-in unusual_devs list. List
2700 entries are separated by commas. Each entry has
2701 the form VID:PID:Flags where VID and PID are Vendor
2702 and Product ID values (4-digit hex numbers) and
2703 Flags is a set of characters, each corresponding
2704 to a common usb-storage quirk flag as follows:
2705 a = SANE_SENSE (collect more than 18 bytes
2706 of sense data);
2707 b = BAD_SENSE (don't collect more than 18
2708 bytes of sense data);
2709 c = FIX_CAPACITY (decrease the reported
2710 device capacity by one sector);
2711 h = CAPACITY_HEURISTICS (decrease the
2712 reported device capacity by one
2713 sector if the number is odd);
2714 i = IGNORE_DEVICE (don't bind to this
2715 device);
2716 l = NOT_LOCKABLE (don't try to lock and
2717 unlock ejectable media);
2718 m = MAX_SECTORS_64 (don't transfer more
2719 than 64 sectors = 32 KB at a time);
2720 o = CAPACITY_OK (accept the capacity
2721 reported by the device);
2722 r = IGNORE_RESIDUE (the device reports
2723 bogus residue values);
2724 s = SINGLE_LUN (the device has only one
2725 Logical Unit);
2726 w = NO_WP_DETECT (don't test whether the
2727 medium is write-protected).
2728 Example: quirks=0419:aaf5:rl,0421:0433:rc
2730 userpte=
2731 [X86] Flags controlling user PTE allocations.
2733 nohigh = do not allocate PTE pages in
2734 HIGHMEM regardless of setting
2735 of CONFIG_HIGHPTE.
2737 vdso= [X86,SH]
2738 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2739 vdso=1: enable VDSO (default)
2740 vdso=0: disable VDSO mapping
2742 vdso32= [X86]
2743 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2744 vdso32=1: enable 32-bit VDSO (default)
2745 vdso32=0: disable 32-bit VDSO mapping
2747 vector= [IA-64,SMP]
2748 vector=percpu: enable percpu vector domain
2750 video= [FB] Frame buffer configuration
2751 See Documentation/fb/modedb.txt.
2753 vga= [BOOT,X86-32] Select a particular video mode
2754 See Documentation/x86/boot.txt and
2755 Documentation/svga.txt.
2756 Use vga=ask for menu.
2757 This is actually a boot loader parameter; the value is
2758 passed to the kernel using a special protocol.
2760 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2761 size of <nn>. This can be used to increase the
2762 minimum size (128MB on x86). It can also be used to
2763 decrease the size and leave more room for directly
2764 mapped kernel RAM.
2766 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2767 Format: <command>
2769 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2770 Format: <command>
2772 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2773 Format: <command>
2775 vt.cur_default= [VT] Default cursor shape.
2776 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2777 the parameters of the <Esc>[?A;B;Cc escape sequence;
2778 see VGA-softcursor.txt. Default: 2 = underline.
2780 vt.default_blu= [VT]
2781 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2782 Change the default blue palette of the console.
2783 This is a 16-member array composed of values
2784 ranging from 0-255.
2786 vt.default_grn= [VT]
2787 Format: <green0>,<green1>,<green2>,...,<green15>
2788 Change the default green palette of the console.
2789 This is a 16-member array composed of values
2790 ranging from 0-255.
2792 vt.default_red= [VT]
2793 Format: <red0>,<red1>,<red2>,...,<red15>
2794 Change the default red palette of the console.
2795 This is a 16-member array composed of values
2796 ranging from 0-255.
2798 vt.default_utf8=
2799 [VT]
2800 Format=<0|1>
2801 Set system-wide default UTF-8 mode for all tty's.
2802 Default is 1, i.e. UTF-8 mode is enabled for all
2803 newly opened terminals.
2805 vt.global_cursor_default=
2806 [VT]
2807 Format=<-1|0|1>
2808 Set system-wide default for whether a cursor
2809 is shown on new VTs. Default is -1,
2810 i.e. cursors will be created by default unless
2811 overridden by individual drivers. 0 will hide
2812 cursors, 1 will display them.
2814 waveartist= [HW,OSS]
2815 Format: <io>,<irq>,<dma>,<dma2>
2817 wd33c93= [HW,SCSI]
2818 See header of drivers/scsi/wd33c93.c.
2820 wd7000= [HW,SCSI]
2821 See header of drivers/scsi/wd7000.c.
2823 wdt= [WDT] Watchdog
2824 See Documentation/watchdog/wdt.txt.
2826 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2827 default x2apic cluster mode on platforms
2828 supporting x2apic.
2830 x86_mrst_timer= [X86-32,APBT]
2831 Choose timer option for x86 Moorestown MID platform.
2832 Two valid options are apbt timer only and lapic timer
2833 plus one apbt timer for broadcast timer.
2834 x86_mrst_timer=apbt_only | lapic_and_apbt
2836 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2837 xd_geo= See header of drivers/block/xd.c.
2839 xirc2ps_cs= [NET,PCMCIA]
2840 Format:
2841 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2843 ______________________________________________________________________
2845 TODO:
2847 Add documentation for ALSA options.
2848 Add more DRM drivers.