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1 Kernel Parameters
2 ~~~~~~~~~~~~~~~~~
4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 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 KGDB Kernel debugger support is enabled.
62 KVM Kernel Virtual Machine support is enabled.
63 LIBATA Libata driver is enabled
64 LP Printer support is enabled.
65 LOOP Loopback device support is enabled.
66 M68k M68k architecture is enabled.
67 These options have more detailed description inside of
68 Documentation/m68k/kernel-options.txt.
69 MCA MCA bus support is enabled.
70 MDA MDA console support is enabled.
71 MOUSE Appropriate mouse support is enabled.
72 MSI Message Signaled Interrupts (PCI).
73 MTD MTD (Memory Technology Device) support is enabled.
74 NET Appropriate network support is enabled.
75 NUMA NUMA support is enabled.
76 GENERIC_TIME The generic timeofday code is enabled.
77 NFS Appropriate NFS support is enabled.
78 OSS OSS sound support is enabled.
79 PV_OPS A paravirtualized kernel is enabled.
80 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
81 PARISC The PA-RISC architecture is enabled.
82 PCI PCI bus support is enabled.
83 PCIE PCI Express support is enabled.
84 PCMCIA The PCMCIA subsystem is enabled.
85 PNP Plug & Play support is enabled.
86 PPC PowerPC architecture is enabled.
87 PPT Parallel port support is enabled.
88 PS2 Appropriate PS/2 support is enabled.
89 RAM RAM disk support is enabled.
90 S390 S390 architecture is enabled.
91 SCSI Appropriate SCSI support is enabled.
92 A lot of drivers has their options described inside of
93 Documentation/scsi/.
94 SECURITY Different security models are enabled.
95 SELINUX SELinux support is enabled.
96 SERIAL Serial support is enabled.
97 SH SuperH architecture is enabled.
98 SMP The kernel is an SMP kernel.
99 SPARC Sparc architecture is enabled.
100 SWSUSP Software suspend (hibernation) is enabled.
101 SUSPEND System suspend states are enabled.
102 FTRACE Function tracing enabled.
103 TPM TPM drivers are enabled.
104 TS Appropriate touchscreen support is enabled.
105 UMS USB Mass Storage support is enabled.
106 USB USB support is enabled.
107 USBHID USB Human Interface Device support is enabled.
108 V4L Video For Linux support is enabled.
109 VGA The VGA console has been enabled.
110 VT Virtual terminal support is enabled.
111 WDT Watchdog support is enabled.
112 XT IBM PC/XT MFM hard disk support is enabled.
113 X86-32 X86-32, aka i386 architecture is enabled.
114 X86-64 X86-64 architecture is enabled.
115 More X86-64 boot options can be found in
116 Documentation/x86/x86_64/boot-options.txt .
117 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
119 In addition, the following text indicates that the option:
121 BUGS= Relates to possible processor bugs on the said processor.
122 KNL Is a kernel start-up parameter.
123 BOOT Is a boot loader parameter.
125 Parameters denoted with BOOT are actually interpreted by the boot
126 loader, and have no meaning to the kernel directly.
127 Do not modify the syntax of boot loader parameters without extreme
128 need or coordination with <Documentation/x86/boot.txt>.
130 There are also arch-specific kernel-parameters not documented here.
131 See for example <Documentation/x86/x86_64/boot-options.txt>.
133 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
134 a trailing = on the name of any parameter states that that parameter will
135 be entered as an environment variable, whereas its absence indicates that
136 it will appear as a kernel argument readable via /proc/cmdline by programs
137 running once the system is up.
139 The number of kernel parameters is not limited, but the length of the
140 complete command line (parameters including spaces etc.) is limited to
141 a fixed number of characters. This limit depends on the architecture
142 and is between 256 and 4096 characters. It is defined in the file
143 ./include/asm/setup.h as COMMAND_LINE_SIZE.
146 acpi= [HW,ACPI,X86]
147 Advanced Configuration and Power Interface
148 Format: { force | off | ht | strict | noirq | rsdt }
149 force -- enable ACPI if default was off
150 off -- disable ACPI if default was on
151 noirq -- do not use ACPI for IRQ routing
152 ht -- run only enough ACPI to enable Hyper Threading
153 strict -- Be less tolerant of platforms that are not
154 strictly ACPI specification compliant.
155 rsdt -- prefer RSDT over (default) XSDT
156 copy_dsdt -- copy DSDT to memory
158 See also Documentation/power/pm.txt, pci=noacpi
160 acpi_apic_instance= [ACPI, IOAPIC]
161 Format: <int>
162 2: use 2nd APIC table, if available
163 1,0: use 1st APIC table
164 default: 0
166 acpi_backlight= [HW,ACPI]
167 acpi_backlight=vendor
168 acpi_backlight=video
169 If set to vendor, prefer vendor specific driver
170 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
171 of the ACPI video.ko driver.
173 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
174 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
175 Format: <int>
176 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
177 debug output. Bits in debug_layer correspond to a
178 _COMPONENT in an ACPI source file, e.g.,
179 #define _COMPONENT ACPI_PCI_COMPONENT
180 Bits in debug_level correspond to a level in
181 ACPI_DEBUG_PRINT statements, e.g.,
182 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
183 The debug_level mask defaults to "info". See
184 Documentation/acpi/debug.txt for more information about
185 debug layers and levels.
187 Enable processor driver info messages:
188 acpi.debug_layer=0x20000000
189 Enable PCI/PCI interrupt routing info messages:
190 acpi.debug_layer=0x400000
191 Enable AML "Debug" output, i.e., stores to the Debug
192 object while interpreting AML:
193 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
194 Enable all messages related to ACPI hardware:
195 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
197 Some values produce so much output that the system is
198 unusable. The "log_buf_len" parameter may be useful
199 if you need to capture more output.
201 acpi_display_output= [HW,ACPI]
202 acpi_display_output=vendor
203 acpi_display_output=video
204 See above.
206 acpi_irq_balance [HW,ACPI]
207 ACPI will balance active IRQs
208 default in APIC mode
210 acpi_irq_nobalance [HW,ACPI]
211 ACPI will not move active IRQs (default)
212 default in PIC mode
214 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
215 Format: <irq>,<irq>...
217 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
218 use by PCI
219 Format: <irq>,<irq>...
221 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
223 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
224 Format: To spoof as Windows 98: ="Microsoft Windows"
226 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
227 acpi_osi="string1" # add string1 -- only one string
228 acpi_osi="!string2" # remove built-in string2
229 acpi_osi= # disable all strings
231 acpi_pm_good [X86]
232 Override the pmtimer bug detection: force the kernel
233 to assume that this machine's pmtimer latches its value
234 and always returns good values.
236 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
237 Format: { level | edge | high | low }
239 acpi_serialize [HW,ACPI] force serialization of AML methods
241 acpi_skip_timer_override [HW,ACPI]
242 Recognize and ignore IRQ0/pin2 Interrupt Override.
243 For broken nForce2 BIOS resulting in XT-PIC timer.
245 acpi_sleep= [HW,ACPI] Sleep options
246 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
247 old_ordering, s4_nonvs, sci_force_enable }
248 See Documentation/power/video.txt for information on
249 s3_bios and s3_mode.
250 s3_beep is for debugging; it makes the PC's speaker beep
251 as soon as the kernel's real-mode entry point is called.
252 s4_nohwsig prevents ACPI hardware signature from being
253 used during resume from hibernation.
254 old_ordering causes the ACPI 1.0 ordering of the _PTS
255 control method, with respect to putting devices into
256 low power states, to be enforced (the ACPI 2.0 ordering
257 of _PTS is used by default).
258 s4_nonvs prevents the kernel from saving/restoring the
259 ACPI NVS memory during hibernation.
260 sci_force_enable causes the kernel to set SCI_EN directly
261 on resume from S1/S3 (which is against the ACPI spec,
262 but some broken systems don't work without it).
264 acpi_use_timer_override [HW,ACPI]
265 Use timer override. For some broken Nvidia NF5 boards
266 that require a timer override, but don't have HPET
268 acpi_enforce_resources= [ACPI]
269 { strict | lax | no }
270 Check for resource conflicts between native drivers
271 and ACPI OperationRegions (SystemIO and SystemMemory
272 only). IO ports and memory declared in ACPI might be
273 used by the ACPI subsystem in arbitrary AML code and
274 can interfere with legacy drivers.
275 strict (default): access to resources claimed by ACPI
276 is denied; legacy drivers trying to access reserved
277 resources will fail to bind to device using them.
278 lax: access to resources claimed by ACPI is allowed;
279 legacy drivers trying to access reserved resources
280 will bind successfully but a warning message is logged.
281 no: ACPI OperationRegions are not marked as reserved,
282 no further checks are performed.
284 ad1848= [HW,OSS]
285 Format: <io>,<irq>,<dma>,<dma2>,<type>
287 add_efi_memmap [EFI; X86] Include EFI memory map in
288 kernel's map of available physical RAM.
290 advansys= [HW,SCSI]
291 See header of drivers/scsi/advansys.c.
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
327 off - do not initialize any AMD IOMMU found in
328 the system
330 amijoy.map= [HW,JOY] Amiga joystick support
331 Map of devices attached to JOY0DAT and JOY1DAT
332 Format: <a>,<b>
333 See also Documentation/kernel/input/joystick.txt
335 analog.map= [HW,JOY] Analog joystick and gamepad support
336 Specifies type or capabilities of an analog joystick
337 connected to one of 16 gameports
338 Format: <type1>,<type2>,..<type16>
340 apc= [HW,SPARC]
341 Power management functions (SPARCstation-4/5 + deriv.)
342 Format: noidle
343 Disable APC CPU standby support. SPARCstation-Fox does
344 not play well with APC CPU idle - disable it if you have
345 APC and your system crashes randomly.
347 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
348 Change the output verbosity whilst booting
349 Format: { quiet (default) | verbose | debug }
350 Change the amount of debugging information output
351 when initialising the APIC and IO-APIC components.
353 autoconf= [IPV6]
354 See Documentation/networking/ipv6.txt.
356 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
357 Limit apic dumping. The parameter defines the maximal
358 number of local apics being dumped. Also it is possible
359 to set it to "all" by meaning -- no limit here.
360 Format: { 1 (default) | 2 | ... | all }.
361 The parameter valid if only apic=debug or
362 apic=verbose is specified.
363 Example: apic=debug show_lapic=all
365 apm= [APM] Advanced Power Management
366 See header of arch/x86/kernel/apm_32.c.
368 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
369 Format: <io>,<irq>,<nodeID>
371 ataflop= [HW,M68k]
373 atarimouse= [HW,MOUSE] Atari Mouse
375 atascsi= [HW,SCSI] Atari SCSI
377 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
378 EzKey and similar keyboards
380 atkbd.reset= [HW] Reset keyboard during initialization
382 atkbd.set= [HW] Select keyboard code set
383 Format: <int> (2 = AT (default), 3 = PS/2)
385 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
386 keyboards
388 atkbd.softraw= [HW] Choose between synthetic and real raw mode
389 Format: <bool> (0 = real, 1 = synthetic (default))
391 atkbd.softrepeat= [HW]
392 Use software keyboard repeat
394 autotest [IA64]
396 baycom_epp= [HW,AX25]
397 Format: <io>,<mode>
399 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
400 Format: <io>,<mode>
401 See header of drivers/net/hamradio/baycom_par.c.
403 baycom_ser_fdx= [HW,AX25]
404 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
405 Format: <io>,<irq>,<mode>[,<baud>]
406 See header of drivers/net/hamradio/baycom_ser_fdx.c.
408 baycom_ser_hdx= [HW,AX25]
409 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
410 Format: <io>,<irq>,<mode>
411 See header of drivers/net/hamradio/baycom_ser_hdx.c.
413 boot_delay= Milliseconds to delay each printk during boot.
414 Values larger than 10 seconds (10000) are changed to
415 no delay (0).
416 Format: integer
418 bootmem_debug [KNL] Enable bootmem allocator debug messages.
420 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
421 bttv.radio= Most important insmod options are available as
422 kernel args too.
423 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
424 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
426 BusLogic= [HW,SCSI]
427 See drivers/scsi/BusLogic.c, comment before function
428 BusLogic_ParseDriverOptions().
430 c101= [NET] Moxa C101 synchronous serial card
432 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
433 Sometimes CPU hardware bugs make them report the cache
434 size incorrectly. The kernel will attempt work arounds
435 to fix known problems, but for some CPUs it is not
436 possible to determine what the correct size should be.
437 This option provides an override for these situations.
439 capability.disable=
440 [SECURITY] Disable capabilities. This would normally
441 be used only if an alternative security model is to be
442 configured. Potentially dangerous and should only be
443 used if you are entirely sure of the consequences.
445 ccw_timeout_log [S390]
446 See Documentation/s390/CommonIO for details.
448 cgroup_disable= [KNL] Disable a particular controller
449 Format: {name of the controller(s) to disable}
450 {Currently supported controllers - "memory"}
452 checkreqprot [SELINUX] Set initial checkreqprot flag value.
453 Format: { "0" | "1" }
454 See security/selinux/Kconfig help text.
455 0 -- check protection applied by kernel (includes
456 any implied execute protection).
457 1 -- check protection requested by application.
458 Default value is set via a kernel config option.
459 Value can be changed at runtime via
460 /selinux/checkreqprot.
462 cio_ignore= [S390]
463 See Documentation/s390/CommonIO for details.
465 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
466 [Deprecated]
467 Forces specified clocksource (if available) to be used
468 when calculating gettimeofday(). If specified
469 clocksource is not available, it defaults to PIT.
470 Format: { pit | tsc | cyclone | pmtmr }
472 clocksource= [GENERIC_TIME] Override the default clocksource
473 Format: <string>
474 Override the default clocksource and use the clocksource
475 with the name specified.
476 Some clocksource names to choose from, depending on
477 the platform:
478 [all] jiffies (this is the base, fallback clocksource)
479 [ACPI] acpi_pm
480 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
481 pxa_timer,timer3,32k_counter,timer0_1
482 [AVR32] avr32
483 [X86-32] pit,hpet,tsc,vmi-timer;
484 scx200_hrt on Geode; cyclone on IBM x440
485 [MIPS] MIPS
486 [PARISC] cr16
487 [S390] tod
488 [SH] SuperH
489 [SPARC64] tick
490 [X86-64] hpet,tsc
492 clearcpuid=BITNUM [X86]
493 Disable CPUID feature X for the kernel. See
494 arch/x86/include/asm/cpufeature.h for the valid bit
495 numbers. Note the Linux specific bits are not necessarily
496 stable over kernel options, but the vendor specific
497 ones should be.
498 Also note that user programs calling CPUID directly
499 or using the feature without checking anything
500 will still see it. This just prevents it from
501 being used by the kernel or shown in /proc/cpuinfo.
502 Also note the kernel might malfunction if you disable
503 some critical bits.
505 cmo_free_hint= [PPC] Format: { yes | no }
506 Specify whether pages are marked as being inactive
507 when they are freed. This is used in CMO environments
508 to determine OS memory pressure for page stealing by
509 a hypervisor.
510 Default: yes
512 code_bytes [X86] How many bytes of object code to print
513 in an oops report.
514 Range: 0 - 8192
515 Default: 64
517 com20020= [HW,NET] ARCnet - COM20020 chipset
518 Format:
519 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
521 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
522 Format: <io>[,<irq>]
524 com90xx= [HW,NET]
525 ARCnet - COM90xx chipset (memory-mapped buffers)
526 Format: <io>[,<irq>[,<memstart>]]
528 condev= [HW,S390] console device
529 conmode=
531 console= [KNL] Output console device and options.
533 tty<n> Use the virtual console device <n>.
535 ttyS<n>[,options]
536 ttyUSB0[,options]
537 Use the specified serial port. The options are of
538 the form "bbbbpnf", where "bbbb" is the baud rate,
539 "p" is parity ("n", "o", or "e"), "n" is number of
540 bits, and "f" is flow control ("r" for RTS or
541 omit it). Default is "9600n8".
543 See Documentation/serial-console.txt for more
544 information. See
545 Documentation/networking/netconsole.txt for an
546 alternative.
548 uart[8250],io,<addr>[,options]
549 uart[8250],mmio,<addr>[,options]
550 Start an early, polled-mode console on the 8250/16550
551 UART at the specified I/O port or MMIO address,
552 switching to the matching ttyS device later. The
553 options are the same as for ttyS, above.
555 If the device connected to the port is not a TTY but a braille
556 device, prepend "brl," before the device type, for instance
557 console=brl,ttyS0
558 For now, only VisioBraille is supported.
560 consoleblank= [KNL] The console blank (screen saver) timeout in
561 seconds. Defaults to 10*60 = 10mins. A value of 0
562 disables the blank timer.
564 coredump_filter=
565 [KNL] Change the default value for
566 /proc/<pid>/coredump_filter.
567 See also Documentation/filesystems/proc.txt.
569 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
570 Format:
571 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
573 crashkernel=nn[KMG]@ss[KMG]
574 [KNL] Reserve a chunk of physical memory to
575 hold a kernel to switch to with kexec on panic.
577 crashkernel=range1:size1[,range2:size2,...][@offset]
578 [KNL] Same as above, but depends on the memory
579 in the running system. The syntax of range is
580 start-[end] where start and end are both
581 a memory unit (amount[KMG]). See also
582 Documentation/kdump/kdump.txt for a example.
584 cs89x0_dma= [HW,NET]
585 Format: <dma>
587 cs89x0_media= [HW,NET]
588 Format: { rj45 | aui | bnc }
590 dasd= [HW,NET]
591 See header of drivers/s390/block/dasd_devmap.c.
593 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
594 (one device per port)
595 Format: <port#>,<type>
596 See also Documentation/input/joystick-parport.txt
598 debug [KNL] Enable kernel debugging (events log level).
600 debug_locks_verbose=
601 [KNL] verbose self-tests
602 Format=<0|1>
603 Print debugging info while doing the locking API
604 self-tests.
605 We default to 0 (no extra messages), setting it to
606 1 will print _a lot_ more information - normally
607 only useful to kernel developers.
609 debug_objects [KNL] Enable object debugging
611 no_debug_objects
612 [KNL] Disable object debugging
614 debugpat [X86] Enable PAT debugging
616 decnet.addr= [HW,NET]
617 Format: <area>[,<node>]
618 See also Documentation/networking/decnet.txt.
620 default_hugepagesz=
621 [same as hugepagesz=] The size of the default
622 HugeTLB page size. This is the size represented by
623 the legacy /proc/ hugepages APIs, used for SHM, and
624 default size when mounting hugetlbfs filesystems.
625 Defaults to the default architecture's huge page size
626 if not specified.
628 dhash_entries= [KNL]
629 Set number of hash buckets for dentry cache.
631 digi= [HW,SERIAL]
632 IO parameters + enable/disable command.
634 digiepca= [HW,SERIAL]
635 See drivers/char/README.epca and
636 Documentation/serial/digiepca.txt.
638 disable= [IPV6]
639 See Documentation/networking/ipv6.txt.
641 disable_ipv6= [IPV6]
642 See Documentation/networking/ipv6.txt.
644 disable_mtrr_cleanup [X86]
645 The kernel tries to adjust MTRR layout from continuous
646 to discrete, to make X server driver able to add WB
647 entry later. This parameter disables that.
649 disable_mtrr_trim [X86, Intel and AMD only]
650 By default the kernel will trim any uncacheable
651 memory out of your available memory pool based on
652 MTRR settings. This parameter disables that behavior,
653 possibly causing your machine to run very slowly.
655 disable_timer_pin_1 [X86]
656 Disable PIN 1 of APIC timer
657 Can be useful to work around chipset bugs.
659 dmasound= [HW,OSS] Sound subsystem buffers
661 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
662 this option disables the debugging code at boot.
664 dma_debug_entries=<number>
665 This option allows to tune the number of preallocated
666 entries for DMA-API debugging code. One entry is
667 required per DMA-API allocation. Use this if the
668 DMA-API debugging code disables itself because the
669 architectural default is too low.
671 dma_debug_driver=<driver_name>
672 With this option the DMA-API debugging driver
673 filter feature can be enabled at boot time. Just
674 pass the driver to filter for as the parameter.
675 The filter can be disabled or changed to another
676 driver later using sysfs.
678 dscc4.setup= [NET]
680 dtc3181e= [HW,SCSI]
682 dynamic_printk Enables pr_debug()/dev_dbg() calls if
683 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
684 These can also be switched on/off via
685 <debugfs>/dynamic_printk/modules
687 earlycon= [KNL] Output early console device and options.
688 uart[8250],io,<addr>[,options]
689 uart[8250],mmio,<addr>[,options]
690 Start an early, polled-mode console on the 8250/16550
691 UART at the specified I/O port or MMIO address.
692 The options are the same as for ttyS, above.
694 earlyprintk= [X86,SH,BLACKFIN]
695 earlyprintk=vga
696 earlyprintk=serial[,ttySn[,baudrate]]
697 earlyprintk=ttySn[,baudrate]
698 earlyprintk=dbgp[debugController#]
700 Append ",keep" to not disable it when the real console
701 takes over.
703 Only vga or serial or usb debug port at a time.
705 Currently only ttyS0 and ttyS1 are supported.
707 Interaction with the standard serial driver is not
708 very good.
710 The VGA output is eventually overwritten by the real
711 console.
713 ekgdboc= [X86,KGDB] Allow early kernel console debugging
714 ekgdboc=kbd
716 This is desgined to be used in conjunction with
717 the boot argument: earlyprintk=vga
719 eata= [HW,SCSI]
721 edd= [EDD]
722 Format: {"off" | "on" | "skip[mbr]"}
724 eisa_irq_edge= [PARISC,HW]
725 See header of drivers/parisc/eisa.c.
727 elanfreq= [X86-32]
728 See comment before function elanfreq_setup() in
729 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
731 elevator= [IOSCHED]
732 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
733 See Documentation/block/as-iosched.txt and
734 Documentation/block/deadline-iosched.txt for details.
736 elfcorehdr= [IA64,PPC,SH,X86]
737 Specifies physical address of start of kernel core
738 image elf header. Generally kexec loader will
739 pass this option to capture kernel.
740 See Documentation/kdump/kdump.txt for details.
742 enable_mtrr_cleanup [X86]
743 The kernel tries to adjust MTRR layout from continuous
744 to discrete, to make X server driver able to add WB
745 entry later. This parameter enables that.
747 enable_timer_pin_1 [X86]
748 Enable PIN 1 of APIC timer
749 Can be useful to work around chipset bugs
750 (in particular on some ATI chipsets).
751 The kernel tries to set a reasonable default.
753 enforcing [SELINUX] Set initial enforcing status.
754 Format: {"0" | "1"}
755 See security/selinux/Kconfig help text.
756 0 -- permissive (log only, no denials).
757 1 -- enforcing (deny and log).
758 Default value is 0.
759 Value can be changed at runtime via /selinux/enforce.
761 ether= [HW,NET] Ethernet cards parameters
762 This option is obsoleted by the "netdev=" option, which
763 has equivalent usage. See its documentation for details.
765 failslab=
766 fail_page_alloc=
767 fail_make_request=[KNL]
768 General fault injection mechanism.
769 Format: <interval>,<probability>,<space>,<times>
770 See also /Documentation/fault-injection/.
772 fd_mcs= [HW,SCSI]
773 See header of drivers/scsi/fd_mcs.c.
775 fdomain= [HW,SCSI]
776 See header of drivers/scsi/fdomain.c.
778 floppy= [HW]
779 See Documentation/blockdev/floppy.txt.
781 force_pal_cache_flush
782 [IA-64] Avoid check_sal_cache_flush which may hang on
783 buggy SAL_CACHE_FLUSH implementations. Using this
784 parameter will force ia64_sal_cache_flush to call
785 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
787 ftrace=[tracer]
788 [FTRACE] will set and start the specified tracer
789 as early as possible in order to facilitate early
790 boot debugging.
792 ftrace_dump_on_oops[=orig_cpu]
793 [FTRACE] will dump the trace buffers on oops.
794 If no parameter is passed, ftrace will dump
795 buffers of all CPUs, but if you pass orig_cpu, it will
796 dump only the buffer of the CPU that triggered the
797 oops.
799 ftrace_filter=[function-list]
800 [FTRACE] Limit the functions traced by the function
801 tracer at boot up. function-list is a comma separated
802 list of functions. This list can be changed at run
803 time by the set_ftrace_filter file in the debugfs
804 tracing directory.
806 ftrace_notrace=[function-list]
807 [FTRACE] Do not trace the functions specified in
808 function-list. This list can be changed at run time
809 by the set_ftrace_notrace file in the debugfs
810 tracing directory.
812 ftrace_graph_filter=[function-list]
813 [FTRACE] Limit the top level callers functions traced
814 by the function graph tracer at boot up.
815 function-list is a comma separated list of functions
816 that can be changed at run time by the
817 set_graph_function file in the debugfs tracing directory.
819 gamecon.map[2|3]=
820 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
821 support via parallel port (up to 5 devices per port)
822 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
823 See also Documentation/input/joystick-parport.txt
825 gamma= [HW,DRM]
827 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
828 Format: off | on
829 default: on
831 gcov_persist= [GCOV] When non-zero (default), profiling data for
832 kernel modules is saved and remains accessible via
833 debugfs, even when the module is unloaded/reloaded.
834 When zero, profiling data is discarded and associated
835 debugfs files are removed at module unload time.
837 gdth= [HW,SCSI]
838 See header of drivers/scsi/gdth.c.
840 gpt [EFI] Forces disk with valid GPT signature but
841 invalid Protective MBR to be treated as GPT.
843 gvp11= [HW,SCSI]
845 hashdist= [KNL,NUMA] Large hashes allocated during boot
846 are distributed across NUMA nodes. Defaults on
847 for 64bit NUMA, off otherwise.
848 Format: 0 | 1 (for off | on)
850 hcl= [IA-64] SGI's Hardware Graph compatibility layer
852 hd= [EIDE] (E)IDE hard drive subsystem geometry
853 Format: <cyl>,<head>,<sect>
855 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
856 size of <nn>. This works even on boxes that have no
857 highmem otherwise. This also works to reduce highmem
858 size on bigger boxes.
860 highres= [KNL] Enable/disable high resolution timer mode.
861 Valid parameters: "on", "off"
862 Default: "on"
864 hisax= [HW,ISDN]
865 See Documentation/isdn/README.HiSax.
867 hlt [BUGS=ARM,SH]
869 hpet= [X86-32,HPET] option to control HPET usage
870 Format: { enable (default) | disable | force |
871 verbose }
872 disable: disable HPET and use PIT instead
873 force: allow force enabled of undocumented chips (ICH4,
874 VIA, nVidia)
875 verbose: show contents of HPET registers during setup
877 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
878 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
879 On x86-64 and powerpc, this option can be specified
880 multiple times interleaved with hugepages= to reserve
881 huge pages of different sizes. Valid pages sizes on
882 x86-64 are 2M (when the CPU supports "pse") and 1G
883 (when the CPU supports the "pdpe1gb" cpuinfo flag)
884 Note that 1GB pages can only be allocated at boot time
885 using hugepages= and not freed afterwards.
887 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
888 terminal devices. Valid values: 0..8
889 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
890 If specified, z/VM IUCV HVC accepts connections
891 from listed z/VM user IDs only.
893 i2c_bus= [HW] Override the default board specific I2C bus speed
894 or register an additional I2C bus that is not
895 registered from board initialization code.
896 Format:
897 <bus_id>,<clkrate>
899 i8042.debug [HW] Toggle i8042 debug mode
900 i8042.direct [HW] Put keyboard port into non-translated mode
901 i8042.dumbkbd [HW] Pretend that controller can only read data from
902 keyboard and cannot control its state
903 (Don't attempt to blink the leds)
904 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
905 i8042.nokbd [HW] Don't check/create keyboard port
906 i8042.noloop [HW] Disable the AUX Loopback command while probing
907 for the AUX port
908 i8042.nomux [HW] Don't check presence of an active multiplexing
909 controller
910 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
911 controllers
912 i8042.panicblink=
913 [HW] Frequency with which keyboard LEDs should blink
914 when kernel panics (default is 0.5 sec)
915 i8042.reset [HW] Reset the controller during init and cleanup
916 i8042.unlock [HW] Unlock (ignore) the keylock
918 i810= [HW,DRM]
920 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
921 indicates that the driver is running on unsupported
922 hardware.
923 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
924 does not match list of supported models.
925 i8k.power_status
926 [HW] Report power status in /proc/i8k
927 (disabled by default)
928 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
929 capability is set.
931 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
932 See Documentation/mca.txt.
934 icn= [HW,ISDN]
935 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
937 ide-core.nodma= [HW] (E)IDE subsystem
938 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
939 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
940 .cdrom .chs .ignore_cable are additional options
941 See Documentation/ide/ide.txt.
943 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
944 Claim all unknown PCI IDE storage controllers.
946 idle= [X86]
947 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
948 Poll forces a polling idle loop that can slightly
949 improve the performance of waking up a idle CPU, but
950 will use a lot of power and make the system run hot.
951 Not recommended.
952 idle=mwait: On systems which support MONITOR/MWAIT but
953 the kernel chose to not use it because it doesn't save
954 as much power as a normal idle loop, use the
955 MONITOR/MWAIT idle loop anyways. Performance should be
956 the same as idle=poll.
957 idle=halt: Halt is forced to be used for CPU idle.
958 In such case C2/C3 won't be used again.
959 idle=nomwait: Disable mwait for CPU C-states
961 ignore_loglevel [KNL]
962 Ignore loglevel setting - this will print /all/
963 kernel messages to the console. Useful for debugging.
965 ihash_entries= [KNL]
966 Set number of hash buckets for inode cache.
968 ima_audit= [IMA]
969 Format: { "0" | "1" }
970 0 -- integrity auditing messages. (Default)
971 1 -- enable informational integrity auditing messages.
973 ima_hash= [IMA]
974 Format: { "sha1" | "md5" }
975 default: "sha1"
977 ima_tcb [IMA]
978 Load a policy which meets the needs of the Trusted
979 Computing Base. This means IMA will measure all
980 programs exec'd, files mmap'd for exec, and all files
981 opened for read by uid=0.
983 in2000= [HW,SCSI]
984 See header of drivers/scsi/in2000.c.
986 init= [KNL]
987 Format: <full_path>
988 Run specified binary instead of /sbin/init as init
989 process.
991 initcall_debug [KNL] Trace initcalls as they are executed. Useful
992 for working out where the kernel is dying during
993 startup.
995 initrd= [BOOT] Specify the location of the initial ramdisk
997 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
998 Format: <irq>
1000 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1001 on
1002 Enable intel iommu driver.
1003 off
1004 Disable intel iommu driver.
1005 igfx_off [Default Off]
1006 By default, gfx is mapped as normal device. If a gfx
1007 device has a dedicated DMAR unit, the DMAR unit is
1008 bypassed by not enabling DMAR with this option. In
1009 this case, gfx device will use physical address for
1010 DMA.
1011 forcedac [x86_64]
1012 With this option iommu will not optimize to look
1013 for io virtual address below 32 bit forcing dual
1014 address cycle on pci bus for cards supporting greater
1015 than 32 bit addressing. The default is to look
1016 for translation below 32 bit and if not available
1017 then look in the higher range.
1018 strict [Default Off]
1019 With this option on every unmap_single operation will
1020 result in a hardware IOTLB flush operation as opposed
1021 to batching them for performance.
1023 inttest= [IA64]
1025 iomem= Disable strict checking of access to MMIO memory
1026 strict regions from userspace.
1027 relaxed
1029 iommu= [x86]
1030 off
1031 force
1032 noforce
1033 biomerge
1034 panic
1035 nopanic
1036 merge
1037 nomerge
1038 forcesac
1039 soft
1040 pt [x86, IA64]
1042 io7= [HW] IO7 for Marvel based alpha systems
1043 See comment before marvel_specify_io7 in
1044 arch/alpha/kernel/core_marvel.c.
1046 io_delay= [X86] I/O delay method
1047 0x80
1048 Standard port 0x80 based delay
1049 0xed
1050 Alternate port 0xed based delay (needed on some systems)
1051 udelay
1052 Simple two microseconds delay
1053 none
1054 No delay
1056 ip= [IP_PNP]
1057 See Documentation/filesystems/nfs/nfsroot.txt.
1059 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1060 See comment before ip2_setup() in
1061 drivers/char/ip2/ip2base.c.
1063 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1064 See header of drivers/scsi/ips.c.
1066 irqfixup [HW]
1067 When an interrupt is not handled search all handlers
1068 for it. Intended to get systems with badly broken
1069 firmware running.
1071 irqpoll [HW]
1072 When an interrupt is not handled search all handlers
1073 for it. Also check all handlers each timer
1074 interrupt. Intended to get systems with badly broken
1075 firmware running.
1077 isapnp= [ISAPNP]
1078 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1080 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1081 Format:
1082 <cpu number>,...,<cpu number>
1083 or
1084 <cpu number>-<cpu number>
1085 (must be a positive range in ascending order)
1086 or a mixture
1087 <cpu number>,...,<cpu number>-<cpu number>
1089 This option can be used to specify one or more CPUs
1090 to isolate from the general SMP balancing and scheduling
1091 algorithms. You can move a process onto or off an
1092 "isolated" CPU via the CPU affinity syscalls or cpuset.
1093 <cpu number> begins at 0 and the maximum value is
1094 "number of CPUs in system - 1".
1096 This option is the preferred way to isolate CPUs. The
1097 alternative -- manually setting the CPU mask of all
1098 tasks in the system -- can cause problems and
1099 suboptimal load balancer performance.
1101 iucv= [HW,NET]
1103 js= [HW,JOY] Analog joystick
1104 See Documentation/input/joystick.txt.
1106 keepinitrd [HW,ARM]
1108 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1109 specifies the amount of memory usable by the kernel
1110 for non-movable allocations. The requested amount is
1111 spread evenly throughout all nodes in the system. The
1112 remaining memory in each node is used for Movable
1113 pages. In the event, a node is too small to have both
1114 kernelcore and Movable pages, kernelcore pages will
1115 take priority and other nodes will have a larger number
1116 of kernelcore pages. The Movable zone is used for the
1117 allocation of pages that may be reclaimed or moved
1118 by the page migration subsystem. This means that
1119 HugeTLB pages may not be allocated from this zone.
1120 Note that allocations like PTEs-from-HighMem still
1121 use the HighMem zone if it exists, and the Normal
1122 zone if it does not.
1124 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1125 Format: <Controller#>[,poll interval]
1126 The controller # is the number of the ehci usb debug
1127 port as it is probed via PCI. The poll interval is
1128 optional and is the number seconds in between
1129 each poll cycle to the debug port in case you need
1130 the functionality for interrupting the kernel with
1131 gdb or control-c on the dbgp connection. When
1132 not using this parameter you use sysrq-g to break into
1133 the kernel debugger.
1135 kgdboc= [KGDB,HW] kgdb over consoles.
1136 Requires a tty driver that supports console polling,
1137 or a supported polling keyboard driver (non-usb).
1138 Serial only format: <serial_device>[,baud]
1139 keyboard only format: kbd
1140 keyboard and serial format: kbd,<serial_device>[,baud]
1142 kgdbwait [KGDB] Stop kernel execution and enter the
1143 kernel debugger at the earliest opportunity.
1145 kmac= [MIPS] korina ethernet MAC address.
1146 Configure the RouterBoard 532 series on-chip
1147 Ethernet adapter MAC address.
1149 kmemleak= [KNL] Boot-time kmemleak enable/disable
1150 Valid arguments: on, off
1151 Default: on
1153 kstack=N [X86] Print N words from the kernel stack
1154 in oops dumps.
1156 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1157 Default is 0 (don't ignore, but inject #GP)
1159 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1160 Default is 1 (enabled)
1162 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1163 Default is 0 (off)
1165 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1166 for all guests.
1167 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1169 kvm-intel.bypass_guest_pf=
1170 [KVM,Intel] Disables bypassing of guest page faults
1171 on Intel chips. Default is 1 (enabled)
1173 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1174 (virtualized MMU) support on capable Intel chips.
1175 Default is 1 (enabled)
1177 kvm-intel.emulate_invalid_guest_state=
1178 [KVM,Intel] Enable emulation of invalid guest states
1179 Default is 0 (disabled)
1181 kvm-intel.flexpriority=
1182 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1183 Default is 1 (enabled)
1185 kvm-intel.unrestricted_guest=
1186 [KVM,Intel] Disable unrestricted guest feature
1187 (virtualized real and unpaged mode) on capable
1188 Intel chips. Default is 1 (enabled)
1190 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1191 feature (tagged TLBs) on capable Intel chips.
1192 Default is 1 (enabled)
1194 l2cr= [PPC]
1196 l3cr= [PPC]
1198 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1199 disabled it.
1201 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1202 in C2 power state.
1204 libata.dma= [LIBATA] DMA control
1205 libata.dma=0 Disable all PATA and SATA DMA
1206 libata.dma=1 PATA and SATA Disk DMA only
1207 libata.dma=2 ATAPI (CDROM) DMA only
1208 libata.dma=4 Compact Flash DMA only
1209 Combinations also work, so libata.dma=3 enables DMA
1210 for disks and CDROMs, but not CFs.
1212 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1213 libata.ignore_hpa=0 keep BIOS limits (default)
1214 libata.ignore_hpa=1 ignore limits, using full disk
1216 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1217 when set.
1218 Format: <int>
1220 libata.force= [LIBATA] Force configurations. The format is comma
1221 separated list of "[ID:]VAL" where ID is
1222 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1223 matching port, link or device. Basically, it matches
1224 the ATA ID string printed on console by libata. If
1225 the whole ID part is omitted, the last PORT and DEVICE
1226 values are used. If ID hasn't been specified yet, the
1227 configuration applies to all ports, links and devices.
1229 If only DEVICE is omitted, the parameter applies to
1230 the port and all links and devices behind it. DEVICE
1231 number of 0 either selects the first device or the
1232 first fan-out link behind PMP device. It does not
1233 select the host link. DEVICE number of 15 selects the
1234 host link and device attached to it.
1236 The VAL specifies the configuration to force. As long
1237 as there's no ambiguity shortcut notation is allowed.
1238 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1239 The following configurations can be forced.
1241 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1242 Any ID with matching PORT is used.
1244 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1246 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1247 udma[/][16,25,33,44,66,100,133] notation is also
1248 allowed.
1250 * [no]ncq: Turn on or off NCQ.
1252 * nohrst, nosrst, norst: suppress hard, soft
1253 and both resets.
1255 If there are multiple matching configurations changing
1256 the same attribute, the last one is used.
1258 lmb=debug [KNL] Enable lmb debug messages.
1260 load_ramdisk= [RAM] List of ramdisks to load from floppy
1261 See Documentation/blockdev/ramdisk.txt.
1263 lockd.nlm_grace_period=P [NFS] Assign grace period.
1264 Format: <integer>
1266 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1267 Format: <integer>
1269 lockd.nlm_timeout=T [NFS] Assign timeout value.
1270 Format: <integer>
1272 lockd.nlm_udpport=M [NFS] Assign UDP port.
1273 Format: <integer>
1275 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1276 Format: <irq>
1278 loglevel= All Kernel Messages with a loglevel smaller than the
1279 console loglevel will be printed to the console. It can
1280 also be changed with klogd or other programs. The
1281 loglevels are defined as follows:
1283 0 (KERN_EMERG) system is unusable
1284 1 (KERN_ALERT) action must be taken immediately
1285 2 (KERN_CRIT) critical conditions
1286 3 (KERN_ERR) error conditions
1287 4 (KERN_WARNING) warning conditions
1288 5 (KERN_NOTICE) normal but significant condition
1289 6 (KERN_INFO) informational
1290 7 (KERN_DEBUG) debug-level messages
1292 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1293 Format: { n | nk | nM }
1294 n must be a power of two. The default size
1295 is set in the kernel config file.
1297 logo.nologo [FB] Disables display of the built-in Linux logo.
1298 This may be used to provide more screen space for
1299 kernel log messages and is useful when debugging
1300 kernel boot problems.
1302 lp=0 [LP] Specify parallel ports to use, e.g,
1303 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1304 lp=reset first parallel port). 'lp=0' disables the
1305 lp=auto printer driver. 'lp=reset' (which can be
1306 specified in addition to the ports) causes
1307 attached printers to be reset. Using
1308 lp=port1,port2,... specifies the parallel ports
1309 to associate lp devices with, starting with
1310 lp0. A port specification may be 'none' to skip
1311 that lp device, or a parport name such as
1312 'parport0'. Specifying 'lp=auto' instead of a
1313 port specification list means that device IDs
1314 from each port should be examined, to see if
1315 an IEEE 1284-compliant printer is attached; if
1316 so, the driver will manage that printer.
1317 See also header of drivers/char/lp.c.
1319 lpj=n [KNL]
1320 Sets loops_per_jiffy to given constant, thus avoiding
1321 time-consuming boot-time autodetection (up to 250 ms per
1322 CPU). 0 enables autodetection (default). To determine
1323 the correct value for your kernel, boot with normal
1324 autodetection and see what value is printed. Note that
1325 on SMP systems the preset will be applied to all CPUs,
1326 which is likely to cause problems if your CPUs need
1327 significantly divergent settings. An incorrect value
1328 will cause delays in the kernel to be wrong, leading to
1329 unpredictable I/O errors and other breakage. Although
1330 unlikely, in the extreme case this might damage your
1331 hardware.
1333 ltpc= [NET]
1334 Format: <io>,<irq>,<dma>
1336 mac5380= [HW,SCSI] Format:
1337 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1339 machvec= [IA64] Force the use of a particular machine-vector
1340 (machvec) in a generic kernel.
1341 Example: machvec=hpzx1_swiotlb
1343 machtype= [Loongson] Share the same kernel image file between different
1344 yeeloong laptop.
1345 Example: machtype=lemote-yeeloong-2f-7inch
1347 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1348 than or equal to this physical address is ignored.
1350 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1351 should make use of. maxcpus=n : n >= 0 limits the
1352 kernel to using 'n' processors. n=0 is a special case,
1353 it is equivalent to "nosmp", which also disables
1354 the IO APIC.
1356 max_loop= [LOOP] Maximum number of loopback devices that can
1357 be mounted
1358 Format: <1-256>
1360 max_luns= [SCSI] Maximum number of LUNs to probe.
1361 Should be between 1 and 2^32-1.
1363 max_report_luns=
1364 [SCSI] Maximum number of LUNs received.
1365 Should be between 1 and 16384.
1367 mcatest= [IA-64]
1369 mce [X86-32] Machine Check Exception
1371 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1373 md= [HW] RAID subsystems devices and level
1374 See Documentation/md.txt.
1376 mdacon= [MDA]
1377 Format: <first>,<last>
1378 Specifies range of consoles to be captured by the MDA.
1380 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1381 Amount of memory to be used when the kernel is not able
1382 to see the whole system memory or for test.
1383 [X86-32] Use together with memmap= to avoid physical
1384 address space collisions. Without memmap= PCI devices
1385 could be placed at addresses belonging to unused RAM.
1387 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1388 memory.
1390 memchunk=nn[KMG]
1391 [KNL,SH] Allow user to override the default size for
1392 per-device physically contiguous DMA buffers.
1394 memmap=exactmap [KNL,X86] Enable setting of an exact
1395 E820 memory map, as specified by the user.
1396 Such memmap=exactmap lines can be constructed based on
1397 BIOS output or other requirements. See the memmap=nn@ss
1398 option description.
1400 memmap=nn[KMG]@ss[KMG]
1401 [KNL] Force usage of a specific region of memory
1402 Region of memory to be used, from ss to ss+nn.
1404 memmap=nn[KMG]#ss[KMG]
1405 [KNL,ACPI] Mark specific memory as ACPI data.
1406 Region of memory to be used, from ss to ss+nn.
1408 memmap=nn[KMG]$ss[KMG]
1409 [KNL,ACPI] Mark specific memory as reserved.
1410 Region of memory to be used, from ss to ss+nn.
1411 Example: Exclude memory from 0x18690000-0x1869ffff
1412 memmap=64K$0x18690000
1413 or
1414 memmap=0x10000$0x18690000
1416 memory_corruption_check=0/1 [X86]
1417 Some BIOSes seem to corrupt the first 64k of
1418 memory when doing things like suspend/resume.
1419 Setting this option will scan the memory
1420 looking for corruption. Enabling this will
1421 both detect corruption and prevent the kernel
1422 from using the memory being corrupted.
1423 However, its intended as a diagnostic tool; if
1424 repeatable BIOS-originated corruption always
1425 affects the same memory, you can use memmap=
1426 to prevent the kernel from using that memory.
1428 memory_corruption_check_size=size [X86]
1429 By default it checks for corruption in the low
1430 64k, making this memory unavailable for normal
1431 use. Use this parameter to scan for
1432 corruption in more or less memory.
1434 memory_corruption_check_period=seconds [X86]
1435 By default it checks for corruption every 60
1436 seconds. Use this parameter to check at some
1437 other rate. 0 disables periodic checking.
1439 memtest= [KNL,X86] Enable memtest
1440 Format: <integer>
1441 default : 0 <disable>
1442 Specifies the number of memtest passes to be
1443 performed. Each pass selects another test
1444 pattern from a given set of patterns. Memtest
1445 fills the memory with this pattern, validates
1446 memory contents and reserves bad memory
1447 regions that are detected.
1449 meye.*= [HW] Set MotionEye Camera parameters
1450 See Documentation/video4linux/meye.txt.
1452 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1453 Multi-Function General Purpose Timers on AMD Geode
1454 platforms.
1456 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1457 the BIOS has incorrectly applied a workaround. TinyBIOS
1458 version 0.98 is known to be affected, 0.99 fixes the
1459 problem by letting the user disable the workaround.
1461 mga= [HW,DRM]
1463 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1464 physical address is ignored.
1466 mini2440= [ARM,HW,KNL]
1467 Format:[0..2][b][c][t]
1468 Default: "0tb"
1469 MINI2440 configuration specification:
1470 0 - The attached screen is the 3.5" TFT
1471 1 - The attached screen is the 7" TFT
1472 2 - The VGA Shield is attached (1024x768)
1473 Leaving out the screen size parameter will not load
1474 the TFT driver, and the framebuffer will be left
1475 unconfigured.
1476 b - Enable backlight. The TFT backlight pin will be
1477 linked to the kernel VESA blanking code and a GPIO
1478 LED. This parameter is not necessary when using the
1479 VGA shield.
1480 c - Enable the s3c camera interface.
1481 t - Reserved for enabling touchscreen support. The
1482 touchscreen support is not enabled in the mainstream
1483 kernel as of 2.6.30, a preliminary port can be found
1484 in the "bleeding edge" mini2440 support kernel at
1485 http://repo.or.cz/w/linux-2.6/mini2440.git
1487 mminit_loglevel=
1488 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1489 parameter allows control of the logging verbosity for
1490 the additional memory initialisation checks. A value
1491 of 0 disables mminit logging and a level of 4 will
1492 log everything. Information is printed at KERN_DEBUG
1493 so loglevel=8 may also need to be specified.
1495 mousedev.tap_time=
1496 [MOUSE] Maximum time between finger touching and
1497 leaving touchpad surface for touch to be considered
1498 a tap and be reported as a left button click (for
1499 touchpads working in absolute mode only).
1500 Format: <msecs>
1501 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1502 reporting absolute coordinates, such as tablets
1503 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1504 reporting absolute coordinates, such as tablets
1506 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1507 is similar to kernelcore except it specifies the
1508 amount of memory used for migratable allocations.
1509 If both kernelcore and movablecore is specified,
1510 then kernelcore will be at *least* the specified
1511 value but may be more. If movablecore on its own
1512 is specified, the administrator must be careful
1513 that the amount of memory usable for all allocations
1514 is not too small.
1516 mpu401= [HW,OSS]
1517 Format: <io>,<irq>
1519 MTD_Partition= [MTD]
1520 Format: <name>,<region-number>,<size>,<offset>
1522 MTD_Region= [MTD] Format:
1523 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1525 mtdparts= [MTD]
1526 See drivers/mtd/cmdlinepart.c.
1528 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1530 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1532 boundary - index of last SLC block on Flex-OneNAND.
1533 The remaining blocks are configured as MLC blocks.
1534 lock - Configure if Flex-OneNAND boundary should be locked.
1535 Once locked, the boundary cannot be changed.
1536 1 indicates lock status, 0 indicates unlock status.
1538 mtdset= [ARM]
1539 ARM/S3C2412 JIVE boot control
1541 See arch/arm/mach-s3c2412/mach-jive.c
1543 mtouchusb.raw_coordinates=
1544 [HW] Make the MicroTouch USB driver use raw coordinates
1545 ('y', default) or cooked coordinates ('n')
1547 mtrr_chunk_size=nn[KMG] [X86]
1548 used for mtrr cleanup. It is largest continuous chunk
1549 that could hold holes aka. UC entries.
1551 mtrr_gran_size=nn[KMG] [X86]
1552 Used for mtrr cleanup. It is granularity of mtrr block.
1553 Default is 1.
1554 Large value could prevent small alignment from
1555 using up MTRRs.
1557 mtrr_spare_reg_nr=n [X86]
1558 Format: <integer>
1559 Range: 0,7 : spare reg number
1560 Default : 1
1561 Used for mtrr cleanup. It is spare mtrr entries number.
1562 Set to 2 or more if your graphical card needs more.
1564 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1566 NCR_D700= [HW,SCSI]
1567 See header of drivers/scsi/NCR_D700.c.
1569 ncr5380= [HW,SCSI]
1571 ncr53c400= [HW,SCSI]
1573 ncr53c400a= [HW,SCSI]
1575 ncr53c406a= [HW,SCSI]
1577 ncr53c8xx= [HW,SCSI]
1579 netdev= [NET] Network devices parameters
1580 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1581 Note that mem_start is often overloaded to mean
1582 something different and driver-specific.
1583 This usage is only documented in each driver source
1584 file if at all.
1586 nf_conntrack.acct=
1587 [NETFILTER] Enable connection tracking flow accounting
1588 0 to disable accounting
1589 1 to enable accounting
1590 Default value depends on CONFIG_NF_CT_ACCT that is
1591 going to be removed in 2.6.29.
1593 nfsaddrs= [NFS]
1594 See Documentation/filesystems/nfs/nfsroot.txt.
1596 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1597 See Documentation/filesystems/nfs/nfsroot.txt.
1599 nfs.callback_tcpport=
1600 [NFS] set the TCP port on which the NFSv4 callback
1601 channel should listen.
1603 nfs.cache_getent=
1604 [NFS] sets the pathname to the program which is used
1605 to update the NFS client cache entries.
1607 nfs.cache_getent_timeout=
1608 [NFS] sets the timeout after which an attempt to
1609 update a cache entry is deemed to have failed.
1611 nfs.idmap_cache_timeout=
1612 [NFS] set the maximum lifetime for idmapper cache
1613 entries.
1615 nfs.enable_ino64=
1616 [NFS] enable 64-bit inode numbers.
1617 If zero, the NFS client will fake up a 32-bit inode
1618 number for the readdir() and stat() syscalls instead
1619 of returning the full 64-bit number.
1620 The default is to return 64-bit inode numbers.
1622 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1623 when a NMI is triggered.
1624 Format: [state][,regs][,debounce][,die]
1626 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1627 Format: [panic,][num]
1628 Valid num: 0,1,2
1629 0 - turn nmi_watchdog off
1630 1 - use the IO-APIC timer for the NMI watchdog
1631 2 - use the local APIC for the NMI watchdog using
1632 a performance counter. Note: This will use one
1633 performance counter and the local APIC's performance
1634 vector.
1635 When panic is specified, panic when an NMI watchdog
1636 timeout occurs.
1637 This is useful when you use a panic=... timeout and
1638 need the box quickly up again.
1639 Instead of 1 and 2 it is possible to use the following
1640 symbolic names: lapic and ioapic
1641 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1643 netpoll.carrier_timeout=
1644 [NET] Specifies amount of time (in seconds) that
1645 netpoll should wait for a carrier. By default netpoll
1646 waits 4 seconds.
1648 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1649 emulation library even if a 387 maths coprocessor
1650 is present.
1652 no_console_suspend
1653 [HW] Never suspend the console
1654 Disable suspending of consoles during suspend and
1655 hibernate operations. Once disabled, debugging
1656 messages can reach various consoles while the rest
1657 of the system is being put to sleep (ie, while
1658 debugging driver suspend/resume hooks). This may
1659 not work reliably with all consoles, but is known
1660 to work with serial and VGA consoles.
1662 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1663 caches in the slab allocator. Saves per-node memory,
1664 but will impact performance.
1666 noalign [KNL,ARM]
1668 noapic [SMP,APIC] Tells the kernel to not make use of any
1669 IOAPICs that may be present in the system.
1671 nobats [PPC] Do not use BATs for mapping kernel lowmem
1672 on "Classic" PPC cores.
1674 nocache [ARM]
1676 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1678 nodelayacct [KNL] Disable per-task delay accounting
1680 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1682 nodsp [SH] Disable hardware DSP at boot time.
1684 noefi [X86] Disable EFI runtime services support.
1686 noexec [IA-64]
1688 noexec [X86]
1689 On X86-32 available only on PAE configured kernels.
1690 noexec=on: enable non-executable mappings (default)
1691 noexec=off: disable non-executable mappings
1693 noexec32 [X86-64]
1694 This affects only 32-bit executables.
1695 noexec32=on: enable non-executable mappings (default)
1696 read doesn't imply executable mappings
1697 noexec32=off: disable non-executable mappings
1698 read implies executable mappings
1700 nofpu [SH] Disable hardware FPU at boot time.
1702 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1703 register save and restore. The kernel will only save
1704 legacy floating-point registers on task switch.
1706 noxsave [BUGS=X86] Disables x86 extended register state save
1707 and restore using xsave. The kernel will fallback to
1708 enabling legacy floating-point and sse state.
1710 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1711 wfi(ARM) instruction doesn't work correctly and not to
1712 use it. This is also useful when using JTAG debugger.
1714 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1715 instruction doesn't work correctly and not to
1716 use it.
1718 no_file_caps Tells the kernel not to honor file capabilities. The
1719 only way then for a file to be executed with privilege
1720 is to be setuid root or executed by root.
1722 nohalt [IA-64] Tells the kernel not to use the power saving
1723 function PAL_HALT_LIGHT when idle. This increases
1724 power-consumption. On the positive side, it reduces
1725 interrupt wake-up latency, which may improve performance
1726 in certain environments such as networked servers or
1727 real-time systems.
1729 nohz= [KNL] Boottime enable/disable dynamic ticks
1730 Valid arguments: on, off
1731 Default: on
1733 noiotrap [SH] Disables trapped I/O port accesses.
1735 noirqdebug [X86-32] Disables the code which attempts to detect and
1736 disable unhandled interrupt sources.
1738 no_timer_check [X86,APIC] Disables the code which tests for
1739 broken timer IRQ sources.
1741 noisapnp [ISAPNP] Disables ISA PnP code.
1743 noinitrd [RAM] Tells the kernel not to load any configured
1744 initial RAM disk.
1746 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1747 remapping.
1749 nointroute [IA-64]
1751 nojitter [IA64] Disables jitter checking for ITC timers.
1753 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1755 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1757 noltlbs [PPC] Do not use large page/tlb entries for kernel
1758 lowmem mapping on PPC40x.
1760 nomca [IA-64] Disable machine check abort handling
1762 nomce [X86-32] Machine Check Exception
1764 nomfgpt [X86-32] Disable Multi-Function General Purpose
1765 Timer usage (for AMD Geode machines).
1767 nopat [X86] Disable PAT (page attribute table extension of
1768 pagetables) support.
1770 norandmaps Don't use address space randomization. Equivalent to
1771 echo 0 > /proc/sys/kernel/randomize_va_space
1773 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1775 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1776 with UP alternatives
1778 noresidual [PPC] Don't use residual data on PReP machines.
1780 noresume [SWSUSP] Disables resume and restores original swap
1781 space.
1783 no-scroll [VGA] Disables scrollback.
1784 This is required for the Braillex ib80-piezo Braille
1785 reader made by F.H. Papenmeier (Germany).
1787 nosbagart [IA-64]
1789 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1791 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1792 and disable the IO APIC. legacy for "maxcpus=0".
1794 nosoftlockup [KNL] Disable the soft-lockup detector.
1796 noswapaccount [KNL] Disable accounting of swap in memory resource
1797 controller. (See Documentation/cgroups/memory.txt)
1799 nosync [HW,M68K] Disables sync negotiation for all devices.
1801 notsc [BUGS=X86-32] Disable Time Stamp Counter
1803 nousb [USB] Disable the USB subsystem
1805 nowb [ARM]
1807 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1809 nptcg= [IA64] Override max number of concurrent global TLB
1810 purges which is reported from either PAL_VM_SUMMARY or
1811 SAL PALO.
1813 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1814 could support. nr_cpus=n : n >= 1 limits the kernel to
1815 supporting 'n' processors. Later in runtime you can not
1816 use hotplug cpu feature to put more cpu back to online.
1817 just like you compile the kernel NR_CPUS=n
1819 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1821 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1822 one of ['zone', 'node', 'default'] can be specified
1823 This can be set from sysctl after boot.
1824 See Documentation/sysctl/vm.txt for details.
1826 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1827 See Documentation/debugging-via-ohci1394.txt for more
1828 info.
1830 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1831 Rather than timing out after 20 ms if an EC
1832 command is not properly ACKed, override the length
1833 of the timeout. We have interrupts disabled while
1834 waiting for the ACK, so if this is set too high
1835 interrupts *may* be lost!
1837 omap_mux= [OMAP] Override bootloader pin multiplexing.
1838 Format: <mux_mode0.mode_name=value>...
1839 For example, to override I2C bus2:
1840 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1842 opl3= [HW,OSS]
1843 Format: <io>
1845 oprofile.timer= [HW]
1846 Use timer interrupt instead of performance counters
1848 oprofile.cpu_type= Force an oprofile cpu type
1849 This might be useful if you have an older oprofile
1850 userland or if you want common events.
1851 Format: { arch_perfmon }
1852 arch_perfmon: [X86] Force use of architectural
1853 perfmon on Intel CPUs instead of the
1854 CPU specific event set.
1856 osst= [HW,SCSI] SCSI Tape Driver
1857 Format: <buffer_size>,<write_threshold>
1858 See also Documentation/scsi/st.txt.
1860 panic= [KNL] Kernel behaviour on panic
1861 Format: <timeout>
1863 parkbd.port= [HW] Parallel port number the keyboard adapter is
1864 connected to, default is 0.
1865 Format: <parport#>
1866 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1867 0 for XT, 1 for AT (default is AT).
1868 Format: <mode>
1870 parport= [HW,PPT] Specify parallel ports. 0 disables.
1871 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1872 Use 'auto' to force the driver to use any
1873 IRQ/DMA settings detected (the default is to
1874 ignore detected IRQ/DMA settings because of
1875 possible conflicts). You can specify the base
1876 address, IRQ, and DMA settings; IRQ and DMA
1877 should be numbers, or 'auto' (for using detected
1878 settings on that particular port), or 'nofifo'
1879 (to avoid using a FIFO even if it is detected).
1880 Parallel ports are assigned in the order they
1881 are specified on the command line, starting
1882 with parport0.
1884 parport_init_mode= [HW,PPT]
1885 Configure VIA parallel port to operate in
1886 a specific mode. This is necessary on Pegasos
1887 computer where firmware has no options for setting
1888 up parallel port mode and sets it to spp.
1889 Currently this function knows 686a and 8231 chips.
1890 Format: [spp|ps2|epp|ecp|ecpepp]
1892 pas2= [HW,OSS] Format:
1893 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1895 pas16= [HW,SCSI]
1896 See header of drivers/scsi/pas16.c.
1898 pause_on_oops=
1899 Halt all CPUs after the first oops has been printed for
1900 the specified number of seconds. This is to be used if
1901 your oopses keep scrolling off the screen.
1903 pcbit= [HW,ISDN]
1905 pcd. [PARIDE]
1906 See header of drivers/block/paride/pcd.c.
1907 See also Documentation/blockdev/paride.txt.
1909 pci=option[,option...] [PCI] various PCI subsystem options:
1910 earlydump [X86] dump PCI config space before the kernel
1911 changes anything
1912 off [X86] don't probe for the PCI bus
1913 bios [X86-32] force use of PCI BIOS, don't access
1914 the hardware directly. Use this if your machine
1915 has a non-standard PCI host bridge.
1916 nobios [X86-32] disallow use of PCI BIOS, only direct
1917 hardware access methods are allowed. Use this
1918 if you experience crashes upon bootup and you
1919 suspect they are caused by the BIOS.
1920 conf1 [X86] Force use of PCI Configuration
1921 Mechanism 1.
1922 conf2 [X86] Force use of PCI Configuration
1923 Mechanism 2.
1924 noaer [PCIE] If the PCIEAER kernel config parameter is
1925 enabled, this kernel boot option can be used to
1926 disable the use of PCIE advanced error reporting.
1927 nodomains [PCI] Disable support for multiple PCI
1928 root domains (aka PCI segments, in ACPI-speak).
1929 nommconf [X86] Disable use of MMCONFIG for PCI
1930 Configuration
1931 check_enable_amd_mmconf [X86] check for and enable
1932 properly configured MMIO access to PCI
1933 config space on AMD family 10h CPU
1934 nomsi [MSI] If the PCI_MSI kernel config parameter is
1935 enabled, this kernel boot option can be used to
1936 disable the use of MSI interrupts system-wide.
1937 noioapicquirk [APIC] Disable all boot interrupt quirks.
1938 Safety option to keep boot IRQs enabled. This
1939 should never be necessary.
1940 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1941 primary IO-APIC for bridges that cannot disable
1942 boot IRQs. This fixes a source of spurious IRQs
1943 when the system masks IRQs.
1944 noioapicreroute [APIC] Disable workaround that uses the
1945 boot IRQ equivalent of an IRQ that connects to
1946 a chipset where boot IRQs cannot be disabled.
1947 The opposite of ioapicreroute.
1948 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1949 routing table. These calls are known to be buggy
1950 on several machines and they hang the machine
1951 when used, but on other computers it's the only
1952 way to get the interrupt routing table. Try
1953 this option if the kernel is unable to allocate
1954 IRQs or discover secondary PCI buses on your
1955 motherboard.
1956 rom [X86] Assign address space to expansion ROMs.
1957 Use with caution as certain devices share
1958 address decoders between ROMs and other
1959 resources.
1960 norom [X86] Do not assign address space to
1961 expansion ROMs that do not already have
1962 BIOS assigned address ranges.
1963 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1964 assigned automatically to PCI devices. You can
1965 make the kernel exclude IRQs of your ISA cards
1966 this way.
1967 pirqaddr=0xAAAAA [X86] Specify the physical address
1968 of the PIRQ table (normally generated
1969 by the BIOS) if it is outside the
1970 F0000h-100000h range.
1971 lastbus=N [X86] Scan all buses thru bus #N. Can be
1972 useful if the kernel is unable to find your
1973 secondary buses and you want to tell it
1974 explicitly which ones they are.
1975 assign-busses [X86] Always assign all PCI bus
1976 numbers ourselves, overriding
1977 whatever the firmware may have done.
1978 usepirqmask [X86] Honor the possible IRQ mask stored
1979 in the BIOS $PIR table. This is needed on
1980 some systems with broken BIOSes, notably
1981 some HP Pavilion N5400 and Omnibook XE3
1982 notebooks. This will have no effect if ACPI
1983 IRQ routing is enabled.
1984 noacpi [X86] Do not use ACPI for IRQ routing
1985 or for PCI scanning.
1986 use_crs [X86] Use PCI host bridge window information
1987 from ACPI. On BIOSes from 2008 or later, this
1988 is enabled by default. If you need to use this,
1989 please report a bug.
1990 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1991 If you need to use this, please report a bug.
1992 routeirq Do IRQ routing for all PCI devices.
1993 This is normally done in pci_enable_device(),
1994 so this option is a temporary workaround
1995 for broken drivers that don't call it.
1996 skip_isa_align [X86] do not align io start addr, so can
1997 handle more pci cards
1998 firmware [ARM] Do not re-enumerate the bus but instead
1999 just use the configuration from the
2000 bootloader. This is currently used on
2001 IXP2000 systems where the bus has to be
2002 configured a certain way for adjunct CPUs.
2003 noearly [X86] Don't do any early type 1 scanning.
2004 This might help on some broken boards which
2005 machine check when some devices' config space
2006 is read. But various workarounds are disabled
2007 and some IOMMU drivers will not work.
2008 bfsort Sort PCI devices into breadth-first order.
2009 This sorting is done to get a device
2010 order compatible with older (<= 2.4) kernels.
2011 nobfsort Don't sort PCI devices into breadth-first order.
2012 cbiosize=nn[KMG] The fixed amount of bus space which is
2013 reserved for the CardBus bridge's IO window.
2014 The default value is 256 bytes.
2015 cbmemsize=nn[KMG] The fixed amount of bus space which is
2016 reserved for the CardBus bridge's memory
2017 window. The default value is 64 megabytes.
2018 resource_alignment=
2019 Format:
2020 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2021 Specifies alignment and device to reassign
2022 aligned memory resources.
2023 If <order of align> is not specified,
2024 PAGE_SIZE is used as alignment.
2025 PCI-PCI bridge can be specified, if resource
2026 windows need to be expanded.
2027 ecrc= Enable/disable PCIe ECRC (transaction layer
2028 end-to-end CRC checking).
2029 bios: Use BIOS/firmware settings. This is the
2030 the default.
2031 off: Turn ECRC off
2032 on: Turn ECRC on.
2034 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2035 Management.
2036 off Disable ASPM.
2037 force Enable ASPM even on devices that claim not to support it.
2038 WARNING: Forcing ASPM on may cause system lockups.
2040 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2041 off Do not use native PCIe PME signaling.
2042 force Use native PCIe PME signaling even if the BIOS refuses
2043 to allow the kernel to control the relevant PCIe config
2044 registers.
2045 nomsi Do not use MSI for native PCIe PME signaling (this makes
2046 all PCIe root ports use INTx for everything).
2048 pcmv= [HW,PCMCIA] BadgePAD 4
2050 pd. [PARIDE]
2051 See Documentation/blockdev/paride.txt.
2053 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2054 boot time.
2055 Format: { 0 | 1 }
2056 See arch/parisc/kernel/pdc_chassis.c
2058 percpu_alloc= Select which percpu first chunk allocator to use.
2059 Currently supported values are "embed" and "page".
2060 Archs may support subset or none of the selections.
2061 See comments in mm/percpu.c for details on each
2062 allocator. This parameter is primarily for debugging
2063 and performance comparison.
2065 pf. [PARIDE]
2066 See Documentation/blockdev/paride.txt.
2068 pg. [PARIDE]
2069 See Documentation/blockdev/paride.txt.
2071 pirq= [SMP,APIC] Manual mp-table setup
2072 See Documentation/x86/i386/IO-APIC.txt.
2074 plip= [PPT,NET] Parallel port network link
2075 Format: { parport<nr> | timid | 0 }
2076 See also Documentation/parport.txt.
2078 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2079 Override pmtimer IOPort with a hex value.
2080 e.g. pmtmr=0x508
2082 pnp.debug [PNP]
2083 Enable PNP debug messages. This depends on the
2084 CONFIG_PNP_DEBUG_MESSAGES option.
2086 pnpacpi= [ACPI]
2087 { off }
2089 pnpbios= [ISAPNP]
2090 { on | off | curr | res | no-curr | no-res }
2092 pnp_reserve_irq=
2093 [ISAPNP] Exclude IRQs for the autoconfiguration
2095 pnp_reserve_dma=
2096 [ISAPNP] Exclude DMAs for the autoconfiguration
2098 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2099 Ranges are in pairs (I/O port base and size).
2101 pnp_reserve_mem=
2102 [ISAPNP] Exclude memory regions for the
2103 autoconfiguration.
2104 Ranges are in pairs (memory base and size).
2106 ports= [IP_VS_FTP] IPVS ftp helper module
2107 Default is 21.
2108 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2109 may be specified.
2110 Format: <port>,<port>....
2112 print-fatal-signals=
2113 [KNL] debug: print fatal signals
2115 If enabled, warn about various signal handling
2116 related application anomalies: too many signals,
2117 too many POSIX.1 timers, fatal signals causing a
2118 coredump - etc.
2120 If you hit the warning due to signal overflow,
2121 you might want to try "ulimit -i unlimited".
2123 default: off.
2125 printk.time= Show timing data prefixed to each printk message line
2126 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2128 processor.max_cstate= [HW,ACPI]
2129 Limit processor to maximum C-state
2130 max_cstate=9 overrides any DMI blacklist limit.
2132 processor.nocst [HW,ACPI]
2133 Ignore the _CST method to determine C-states,
2134 instead using the legacy FADT method
2136 profile= [KNL] Enable kernel profiling via /proc/profile
2137 Format: [schedule,]<number>
2138 Param: "schedule" - profile schedule points.
2139 Param: <number> - step/bucket size as a power of 2 for
2140 statistical time based profiling.
2141 Param: "sleep" - profile D-state sleeping (millisecs).
2142 Requires CONFIG_SCHEDSTATS
2143 Param: "kvm" - profile VM exits.
2145 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2146 before loading.
2147 See Documentation/blockdev/ramdisk.txt.
2149 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2150 probe for; one of (bare|imps|exps|lifebook|any).
2151 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2152 per second.
2153 psmouse.resetafter= [HW,MOUSE]
2154 Try to reset the device after so many bad packets
2155 (0 = never).
2156 psmouse.resolution=
2157 [HW,MOUSE] Set desired mouse resolution, in dpi.
2158 psmouse.smartscroll=
2159 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2160 0 = disabled, 1 = enabled (default).
2162 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2163 Format:
2164 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2166 pt. [PARIDE]
2167 See Documentation/blockdev/paride.txt.
2169 pty.legacy_count=
2170 [KNL] Number of legacy pty's. Overwrites compiled-in
2171 default number.
2173 quiet [KNL] Disable most log messages
2175 r128= [HW,DRM]
2177 raid= [HW,RAID]
2178 See Documentation/md.txt.
2180 ramdisk_blocksize= [RAM]
2181 See Documentation/blockdev/ramdisk.txt.
2183 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2184 See Documentation/blockdev/ramdisk.txt.
2186 rcupdate.blimit= [KNL,BOOT]
2187 Set maximum number of finished RCU callbacks to process
2188 in one batch.
2190 rcupdate.qhimark= [KNL,BOOT]
2191 Set threshold of queued
2192 RCU callbacks over which batch limiting is disabled.
2194 rcupdate.qlowmark= [KNL,BOOT]
2195 Set threshold of queued RCU callbacks below which
2196 batch limiting is re-enabled.
2198 rdinit= [KNL]
2199 Format: <full_path>
2200 Run specified binary instead of /init from the ramdisk,
2201 used for early userspace startup. See initrd.
2203 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2204 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2205 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2207 relax_domain_level=
2208 [KNL, SMP] Set scheduler's default relax_domain_level.
2209 See Documentation/cgroups/cpusets.txt.
2211 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2213 reservetop= [X86-32]
2214 Format: nn[KMG]
2215 Reserves a hole at the top of the kernel virtual
2216 address space.
2218 reset_devices [KNL] Force drivers to reset the underlying device
2219 during initialization.
2221 resume= [SWSUSP]
2222 Specify the partition device for software suspend
2224 resume_offset= [SWSUSP]
2225 Specify the offset from the beginning of the partition
2226 given by "resume=" at which the swap header is located,
2227 in <PAGE_SIZE> units (needed only for swap files).
2228 See Documentation/power/swsusp-and-swap-files.txt
2230 retain_initrd [RAM] Keep initrd memory after extraction
2232 rhash_entries= [KNL,NET]
2233 Set number of hash buckets for route cache
2235 riscom8= [HW,SERIAL]
2236 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2238 ro [KNL] Mount root device read-only on boot
2240 root= [KNL] Root filesystem
2242 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2243 mount the root filesystem
2245 rootflags= [KNL] Set root filesystem mount option string
2247 rootfstype= [KNL] Set root filesystem type
2249 rootwait [KNL] Wait (indefinitely) for root device to show up.
2250 Useful for devices that are detected asynchronously
2251 (e.g. USB and MMC devices).
2253 rw [KNL] Mount root device read-write on boot
2255 S [KNL] Run init in single mode
2257 sa1100ir [NET]
2258 See drivers/net/irda/sa1100_ir.c.
2260 sbni= [NET] Granch SBNI12 leased line adapter
2262 sched_debug [KNL] Enables verbose scheduler debug messages.
2264 scsi_debug_*= [SCSI]
2265 See drivers/scsi/scsi_debug.c.
2267 scsi_default_dev_flags=
2268 [SCSI] SCSI default device flags
2269 Format: <integer>
2271 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2272 Format: <vendor>:<model>:<flags>
2273 (flags are integer value)
2275 scsi_logging_level= [SCSI] a bit mask of logging levels
2276 See drivers/scsi/scsi_logging.h for bits. Also
2277 settable via sysctl at dev.scsi.logging_level
2278 (/proc/sys/dev/scsi/logging_level).
2279 There is also a nice 'scsi_logging_level' script in the
2280 S390-tools package, available for download at
2281 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2283 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2284 discovered. async scans them in kernel threads,
2285 allowing boot to proceed. none ignores them, expecting
2286 user space to do the scan.
2288 security= [SECURITY] Choose a security module to enable at boot.
2289 If this boot parameter is not specified, only the first
2290 security module asking for security registration will be
2291 loaded. An invalid security module name will be treated
2292 as if no module has been chosen.
2294 selinux= [SELINUX] Disable or enable SELinux at boot time.
2295 Format: { "0" | "1" }
2296 See security/selinux/Kconfig help text.
2297 0 -- disable.
2298 1 -- enable.
2299 Default value is set via kernel config option.
2300 If enabled at boot time, /selinux/disable can be used
2301 later to disable prior to initial policy load.
2303 serialnumber [BUGS=X86-32]
2305 shapers= [NET]
2306 Maximal number of shapers.
2308 show_msr= [x86] show boot-time MSR settings
2309 Format: { <integer> }
2310 Show boot-time (BIOS-initialized) MSR settings.
2311 The parameter means the number of CPUs to show,
2312 for example 1 means boot CPU only.
2314 sim710= [SCSI,HW]
2315 See header of drivers/scsi/sim710.c.
2317 simeth= [IA-64]
2318 simscsi=
2320 slram= [HW,MTD]
2322 slub_debug[=options[,slabs]] [MM, SLUB]
2323 Enabling slub_debug allows one to determine the
2324 culprit if slab objects become corrupted. Enabling
2325 slub_debug can create guard zones around objects and
2326 may poison objects when not in use. Also tracks the
2327 last alloc / free. For more information see
2328 Documentation/vm/slub.txt.
2330 slub_max_order= [MM, SLUB]
2331 Determines the maximum allowed order for slabs.
2332 A high setting may cause OOMs due to memory
2333 fragmentation. For more information see
2334 Documentation/vm/slub.txt.
2336 slub_min_objects= [MM, SLUB]
2337 The minimum number of objects per slab. SLUB will
2338 increase the slab order up to slub_max_order to
2339 generate a sufficiently large slab able to contain
2340 the number of objects indicated. The higher the number
2341 of objects the smaller the overhead of tracking slabs
2342 and the less frequently locks need to be acquired.
2343 For more information see Documentation/vm/slub.txt.
2345 slub_min_order= [MM, SLUB]
2346 Determines the mininum page order for slabs. Must be
2347 lower than slub_max_order.
2348 For more information see Documentation/vm/slub.txt.
2350 slub_nomerge [MM, SLUB]
2351 Disable merging of slabs with similar size. May be
2352 necessary if there is some reason to distinguish
2353 allocs to different slabs. Debug options disable
2354 merging on their own.
2355 For more information see Documentation/vm/slub.txt.
2357 smart2= [HW]
2358 Format: <io1>[,<io2>[,...,<io8>]]
2360 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2361 attempt to substitute SMP alternatives once at boot.
2363 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2364 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2365 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2366 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2367 smsc-ircc2.ircc_irq= [HW] IRQ line
2368 smsc-ircc2.ircc_dma= [HW] DMA channel
2369 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2370 0: Toshiba Satellite 1800 (GP data pin select)
2371 1: Fast pin select (default)
2372 2: ATC IRMode
2374 snd-ad1816a= [HW,ALSA]
2376 snd-ad1848= [HW,ALSA]
2378 snd-ali5451= [HW,ALSA]
2380 snd-als100= [HW,ALSA]
2382 snd-als4000= [HW,ALSA]
2384 snd-azt2320= [HW,ALSA]
2386 snd-cmi8330= [HW,ALSA]
2388 snd-cmipci= [HW,ALSA]
2390 snd-cs4231= [HW,ALSA]
2392 snd-cs4232= [HW,ALSA]
2394 snd-cs4236= [HW,ALSA]
2396 snd-cs4281= [HW,ALSA]
2398 snd-cs46xx= [HW,ALSA]
2400 snd-dt019x= [HW,ALSA]
2402 snd-dummy= [HW,ALSA]
2404 snd-emu10k1= [HW,ALSA]
2406 snd-ens1370= [HW,ALSA]
2408 snd-ens1371= [HW,ALSA]
2410 snd-es968= [HW,ALSA]
2412 snd-es1688= [HW,ALSA]
2414 snd-es18xx= [HW,ALSA]
2416 snd-es1938= [HW,ALSA]
2418 snd-es1968= [HW,ALSA]
2420 snd-fm801= [HW,ALSA]
2422 snd-gusclassic= [HW,ALSA]
2424 snd-gusextreme= [HW,ALSA]
2426 snd-gusmax= [HW,ALSA]
2428 snd-hdsp= [HW,ALSA]
2430 snd-ice1712= [HW,ALSA]
2432 snd-intel8x0= [HW,ALSA]
2434 snd-interwave= [HW,ALSA]
2436 snd-interwave-stb=
2437 [HW,ALSA]
2439 snd-korg1212= [HW,ALSA]
2441 snd-maestro3= [HW,ALSA]
2443 snd-mpu401= [HW,ALSA]
2445 snd-mtpav= [HW,ALSA]
2447 snd-nm256= [HW,ALSA]
2449 snd-opl3sa2= [HW,ALSA]
2451 snd-opti92x-ad1848=
2452 [HW,ALSA]
2454 snd-opti92x-cs4231=
2455 [HW,ALSA]
2457 snd-opti93x= [HW,ALSA]
2459 snd-pmac= [HW,ALSA]
2461 snd-rme32= [HW,ALSA]
2463 snd-rme96= [HW,ALSA]
2465 snd-rme9652= [HW,ALSA]
2467 snd-sb8= [HW,ALSA]
2469 snd-sb16= [HW,ALSA]
2471 snd-sbawe= [HW,ALSA]
2473 snd-serial= [HW,ALSA]
2475 snd-sgalaxy= [HW,ALSA]
2477 snd-sonicvibes= [HW,ALSA]
2479 snd-sun-amd7930=
2480 [HW,ALSA]
2482 snd-sun-cs4231= [HW,ALSA]
2484 snd-trident= [HW,ALSA]
2486 snd-usb-audio= [HW,ALSA,USB]
2488 snd-via82xx= [HW,ALSA]
2490 snd-virmidi= [HW,ALSA]
2492 snd-wavefront= [HW,ALSA]
2494 snd-ymfpci= [HW,ALSA]
2496 softlockup_panic=
2497 [KNL] Should the soft-lockup detector generate panics.
2499 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2500 See Documentation/sonypi.txt
2502 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2503 See Documentation/serial/specialix.txt.
2505 spia_io_base= [HW,MTD]
2506 spia_fio_base=
2507 spia_pedr=
2508 spia_peddr=
2510 sscape= [HW,OSS]
2511 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2513 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2514 See Documentation/scsi/st.txt.
2516 stacktrace [FTRACE]
2517 Enabled the stack tracer on boot up.
2519 sti= [PARISC,HW]
2520 Format: <num>
2521 Set the STI (builtin display/keyboard on the HP-PARISC
2522 machines) console (graphic card) which should be used
2523 as the initial boot-console.
2524 See also comment in drivers/video/console/sticore.c.
2526 sti_font= [HW]
2527 See comment in drivers/video/console/sticore.c.
2529 stifb= [HW]
2530 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2532 sunrpc.min_resvport=
2533 sunrpc.max_resvport=
2534 [NFS,SUNRPC]
2535 SunRPC servers often require that client requests
2536 originate from a privileged port (i.e. a port in the
2537 range 0 < portnr < 1024).
2538 An administrator who wishes to reserve some of these
2539 ports for other uses may adjust the range that the
2540 kernel's sunrpc client considers to be privileged
2541 using these two parameters to set the minimum and
2542 maximum port values.
2544 sunrpc.pool_mode=
2545 [NFS]
2546 Control how the NFS server code allocates CPUs to
2547 service thread pools. Depending on how many NICs
2548 you have and where their interrupts are bound, this
2549 option will affect which CPUs will do NFS serving.
2550 Note: this parameter cannot be changed while the
2551 NFS server is running.
2553 auto the server chooses an appropriate mode
2554 automatically using heuristics
2555 global a single global pool contains all CPUs
2556 percpu one pool for each CPU
2557 pernode one pool for each NUMA node (equivalent
2558 to global on non-NUMA machines)
2560 sunrpc.tcp_slot_table_entries=
2561 sunrpc.udp_slot_table_entries=
2562 [NFS,SUNRPC]
2563 Sets the upper limit on the number of simultaneous
2564 RPC calls that can be sent from the client to a
2565 server. Increasing these values may allow you to
2566 improve throughput, but will also increase the
2567 amount of memory reserved for use by the client.
2569 swiotlb= [IA-64] Number of I/O TLB slabs
2571 switches= [HW,M68k]
2573 sym53c416= [HW,SCSI]
2574 See header of drivers/scsi/sym53c416.c.
2576 sysrq_always_enabled
2577 [KNL]
2578 Ignore sysrq setting - this boot parameter will
2579 neutralize any effect of /proc/sys/kernel/sysrq.
2580 Useful for debugging.
2582 t128= [HW,SCSI]
2583 See header of drivers/scsi/t128.c.
2585 tdfx= [HW,DRM]
2587 test_suspend= [SUSPEND]
2588 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2589 standby suspend) as the system sleep state to briefly
2590 enter during system startup. The system is woken from
2591 this state using a wakeup-capable RTC alarm.
2593 thash_entries= [KNL,NET]
2594 Set number of hash buckets for TCP connection
2596 thermal.act= [HW,ACPI]
2597 -1: disable all active trip points in all thermal zones
2598 <degrees C>: override all lowest active trip points
2600 thermal.crt= [HW,ACPI]
2601 -1: disable all critical trip points in all thermal zones
2602 <degrees C>: override all critical trip points
2604 thermal.nocrt= [HW,ACPI]
2605 Set to disable actions on ACPI thermal zone
2606 critical and hot trip points.
2608 thermal.off= [HW,ACPI]
2609 1: disable ACPI thermal control
2611 thermal.psv= [HW,ACPI]
2612 -1: disable all passive trip points
2613 <degrees C>: override all passive trip points to this
2614 value
2616 thermal.tzp= [HW,ACPI]
2617 Specify global default ACPI thermal zone polling rate
2618 <deci-seconds>: poll all this frequency
2619 0: no polling (default)
2621 tmscsim= [HW,SCSI]
2622 See comment before function dc390_setup() in
2623 drivers/scsi/tmscsim.c.
2625 topology= [S390]
2626 Format: {off | on}
2627 Specify if the kernel should make use of the cpu
2628 topology informations if the hardware supports these.
2629 The scheduler will make use of these informations and
2630 e.g. base its process migration decisions on it.
2631 Default is off.
2633 tp720= [HW,PS2]
2635 tpm_suspend_pcr=[HW,TPM]
2636 Format: integer pcr id
2637 Specify that at suspend time, the tpm driver
2638 should extend the specified pcr with zeros,
2639 as a workaround for some chips which fail to
2640 flush the last written pcr on TPM_SaveState.
2641 This will guarantee that all the other pcrs
2642 are saved.
2644 trace_buf_size=nn[KMG]
2645 [FTRACE] will set tracing buffer size.
2647 trace_event=[event-list]
2648 [FTRACE] Set and start specified trace events in order
2649 to facilitate early boot debugging.
2650 See also Documentation/trace/events.txt
2652 trix= [HW,OSS] MediaTrix AudioTrix Pro
2653 Format:
2654 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2656 tsc= Disable clocksource-must-verify flag for TSC.
2657 Format: <string>
2658 [x86] reliable: mark tsc clocksource as reliable, this
2659 disables clocksource verification at runtime.
2660 Used to enable high-resolution timer mode on older
2661 hardware, and in virtualized environment.
2663 turbografx.map[2|3]= [HW,JOY]
2664 TurboGraFX parallel port interface
2665 Format:
2666 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2667 See also Documentation/input/joystick-parport.txt
2669 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2670 See header of drivers/scsi/u14-34f.c.
2672 uart401= [HW,OSS]
2673 Format: <io>,<irq>
2675 uart6850= [HW,OSS]
2676 Format: <io>,<irq>
2678 uhash_entries= [KNL,NET]
2679 Set number of hash buckets for UDP/UDP-Lite connections
2681 uhci-hcd.ignore_oc=
2682 [USB] Ignore overcurrent events (default N).
2683 Some badly-designed motherboards generate lots of
2684 bogus events, for ports that aren't wired to
2685 anything. Set this parameter to avoid log spamming.
2686 Note that genuine overcurrent events won't be
2687 reported either.
2689 unknown_nmi_panic
2690 [X86]
2691 Set unknown_nmi_panic=1 early on boot.
2693 usbcore.autosuspend=
2694 [USB] The autosuspend time delay (in seconds) used
2695 for newly-detected USB devices (default 2). This
2696 is the time required before an idle device will be
2697 autosuspended. Devices for which the delay is set
2698 to a negative value won't be autosuspended at all.
2700 usbcore.usbfs_snoop=
2701 [USB] Set to log all usbfs traffic (default 0 = off).
2703 usbcore.blinkenlights=
2704 [USB] Set to cycle leds on hubs (default 0 = off).
2706 usbcore.old_scheme_first=
2707 [USB] Start with the old device initialization
2708 scheme (default 0 = off).
2710 usbcore.use_both_schemes=
2711 [USB] Try the other device initialization scheme
2712 if the first one fails (default 1 = enabled).
2714 usbcore.initial_descriptor_timeout=
2715 [USB] Specifies timeout for the initial 64-byte
2716 USB_REQ_GET_DESCRIPTOR request in milliseconds
2717 (default 5000 = 5.0 seconds).
2719 usbhid.mousepoll=
2720 [USBHID] The interval which mice are to be polled at.
2722 usb-storage.delay_use=
2723 [UMS] The delay in seconds before a new device is
2724 scanned for Logical Units (default 5).
2726 usb-storage.quirks=
2727 [UMS] A list of quirks entries to supplement or
2728 override the built-in unusual_devs list. List
2729 entries are separated by commas. Each entry has
2730 the form VID:PID:Flags where VID and PID are Vendor
2731 and Product ID values (4-digit hex numbers) and
2732 Flags is a set of characters, each corresponding
2733 to a common usb-storage quirk flag as follows:
2734 a = SANE_SENSE (collect more than 18 bytes
2735 of sense data);
2736 b = BAD_SENSE (don't collect more than 18
2737 bytes of sense data);
2738 c = FIX_CAPACITY (decrease the reported
2739 device capacity by one sector);
2740 h = CAPACITY_HEURISTICS (decrease the
2741 reported device capacity by one
2742 sector if the number is odd);
2743 i = IGNORE_DEVICE (don't bind to this
2744 device);
2745 l = NOT_LOCKABLE (don't try to lock and
2746 unlock ejectable media);
2747 m = MAX_SECTORS_64 (don't transfer more
2748 than 64 sectors = 32 KB at a time);
2749 o = CAPACITY_OK (accept the capacity
2750 reported by the device);
2751 r = IGNORE_RESIDUE (the device reports
2752 bogus residue values);
2753 s = SINGLE_LUN (the device has only one
2754 Logical Unit);
2755 w = NO_WP_DETECT (don't test whether the
2756 medium is write-protected).
2757 Example: quirks=0419:aaf5:rl,0421:0433:rc
2759 userpte=
2760 [X86] Flags controlling user PTE allocations.
2762 nohigh = do not allocate PTE pages in
2763 HIGHMEM regardless of setting
2764 of CONFIG_HIGHPTE.
2766 vdso= [X86,SH]
2767 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2768 vdso=1: enable VDSO (default)
2769 vdso=0: disable VDSO mapping
2771 vdso32= [X86]
2772 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2773 vdso32=1: enable 32-bit VDSO (default)
2774 vdso32=0: disable 32-bit VDSO mapping
2776 vector= [IA-64,SMP]
2777 vector=percpu: enable percpu vector domain
2779 video= [FB] Frame buffer configuration
2780 See Documentation/fb/modedb.txt.
2782 vga= [BOOT,X86-32] Select a particular video mode
2783 See Documentation/x86/boot.txt and
2784 Documentation/svga.txt.
2785 Use vga=ask for menu.
2786 This is actually a boot loader parameter; the value is
2787 passed to the kernel using a special protocol.
2789 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2790 size of <nn>. This can be used to increase the
2791 minimum size (128MB on x86). It can also be used to
2792 decrease the size and leave more room for directly
2793 mapped kernel RAM.
2795 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2796 Format: <command>
2798 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2799 Format: <command>
2801 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2802 Format: <command>
2804 vt.cur_default= [VT] Default cursor shape.
2805 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2806 the parameters of the <Esc>[?A;B;Cc escape sequence;
2807 see VGA-softcursor.txt. Default: 2 = underline.
2809 vt.default_blu= [VT]
2810 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2811 Change the default blue palette of the console.
2812 This is a 16-member array composed of values
2813 ranging from 0-255.
2815 vt.default_grn= [VT]
2816 Format: <green0>,<green1>,<green2>,...,<green15>
2817 Change the default green palette of the console.
2818 This is a 16-member array composed of values
2819 ranging from 0-255.
2821 vt.default_red= [VT]
2822 Format: <red0>,<red1>,<red2>,...,<red15>
2823 Change the default red palette of the console.
2824 This is a 16-member array composed of values
2825 ranging from 0-255.
2827 vt.default_utf8=
2828 [VT]
2829 Format=<0|1>
2830 Set system-wide default UTF-8 mode for all tty's.
2831 Default is 1, i.e. UTF-8 mode is enabled for all
2832 newly opened terminals.
2834 vt.global_cursor_default=
2835 [VT]
2836 Format=<-1|0|1>
2837 Set system-wide default for whether a cursor
2838 is shown on new VTs. Default is -1,
2839 i.e. cursors will be created by default unless
2840 overridden by individual drivers. 0 will hide
2841 cursors, 1 will display them.
2843 waveartist= [HW,OSS]
2844 Format: <io>,<irq>,<dma>,<dma2>
2846 wd33c93= [HW,SCSI]
2847 See header of drivers/scsi/wd33c93.c.
2849 wd7000= [HW,SCSI]
2850 See header of drivers/scsi/wd7000.c.
2852 watchdog timers [HW,WDT] For information on watchdog timers,
2853 see Documentation/watchdog/watchdog-parameters.txt
2854 or other driver-specific files in the
2855 Documentation/watchdog/ directory.
2857 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2858 default x2apic cluster mode on platforms
2859 supporting x2apic.
2861 x86_mrst_timer= [X86-32,APBT]
2862 Choose timer option for x86 Moorestown MID platform.
2863 Two valid options are apbt timer only and lapic timer
2864 plus one apbt timer for broadcast timer.
2865 x86_mrst_timer=apbt_only | lapic_and_apbt
2867 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2868 xd_geo= See header of drivers/block/xd.c.
2870 xirc2ps_cs= [NET,PCMCIA]
2871 Format:
2872 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2874 ______________________________________________________________________
2876 TODO:
2878 Add documentation for ALSA options.
2879 Add more DRM drivers.