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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 advwdt= [HW,WDT] Advantech WDT
294 Format: <iostart>,<iostop>
296 aedsp16= [HW,OSS] Audio Excel DSP 16
297 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
298 See also header of sound/oss/aedsp16.c.
300 agp= [AGP]
301 { off | try_unsupported }
302 off: disable AGP support
303 try_unsupported: try to drive unsupported chipsets
304 (may crash computer or cause data corruption)
306 aha152x= [HW,SCSI]
307 See Documentation/scsi/aha152x.txt.
309 aha1542= [HW,SCSI]
310 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
312 aic7xxx= [HW,SCSI]
313 See Documentation/scsi/aic7xxx.txt.
315 aic79xx= [HW,SCSI]
316 See Documentation/scsi/aic79xx.txt.
318 alignment= [KNL,ARM]
319 Allow the default userspace alignment fault handler
320 behaviour to be specified. Bit 0 enables warnings,
321 bit 1 enables fixups, and bit 2 sends a segfault.
323 amd_iommu= [HW,X86-84]
324 Pass parameters to the AMD IOMMU driver in the system.
325 Possible values are:
326 fullflush - enable flushing of IO/TLB entries when
327 they are unmapped. Otherwise they are
328 flushed before they will be reused, which
329 is a lot of faster
330 off - do not initialize any AMD IOMMU found in
331 the system
333 amijoy.map= [HW,JOY] Amiga joystick support
334 Map of devices attached to JOY0DAT and JOY1DAT
335 Format: <a>,<b>
336 See also Documentation/kernel/input/joystick.txt
338 analog.map= [HW,JOY] Analog joystick and gamepad support
339 Specifies type or capabilities of an analog joystick
340 connected to one of 16 gameports
341 Format: <type1>,<type2>,..<type16>
343 apc= [HW,SPARC]
344 Power management functions (SPARCstation-4/5 + deriv.)
345 Format: noidle
346 Disable APC CPU standby support. SPARCstation-Fox does
347 not play well with APC CPU idle - disable it if you have
348 APC and your system crashes randomly.
350 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
351 Change the output verbosity whilst booting
352 Format: { quiet (default) | verbose | debug }
353 Change the amount of debugging information output
354 when initialising the APIC and IO-APIC components.
356 autoconf= [IPV6]
357 See Documentation/networking/ipv6.txt.
359 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
360 Limit apic dumping. The parameter defines the maximal
361 number of local apics being dumped. Also it is possible
362 to set it to "all" by meaning -- no limit here.
363 Format: { 1 (default) | 2 | ... | all }.
364 The parameter valid if only apic=debug or
365 apic=verbose is specified.
366 Example: apic=debug show_lapic=all
368 apm= [APM] Advanced Power Management
369 See header of arch/x86/kernel/apm_32.c.
371 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
372 Format: <io>,<irq>,<nodeID>
374 ataflop= [HW,M68k]
376 atarimouse= [HW,MOUSE] Atari Mouse
378 atascsi= [HW,SCSI] Atari SCSI
380 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
381 EzKey and similar keyboards
383 atkbd.reset= [HW] Reset keyboard during initialization
385 atkbd.set= [HW] Select keyboard code set
386 Format: <int> (2 = AT (default), 3 = PS/2)
388 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
389 keyboards
391 atkbd.softraw= [HW] Choose between synthetic and real raw mode
392 Format: <bool> (0 = real, 1 = synthetic (default))
394 atkbd.softrepeat= [HW]
395 Use software keyboard repeat
397 autotest [IA64]
399 baycom_epp= [HW,AX25]
400 Format: <io>,<mode>
402 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
403 Format: <io>,<mode>
404 See header of drivers/net/hamradio/baycom_par.c.
406 baycom_ser_fdx= [HW,AX25]
407 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
408 Format: <io>,<irq>,<mode>[,<baud>]
409 See header of drivers/net/hamradio/baycom_ser_fdx.c.
411 baycom_ser_hdx= [HW,AX25]
412 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
413 Format: <io>,<irq>,<mode>
414 See header of drivers/net/hamradio/baycom_ser_hdx.c.
416 boot_delay= Milliseconds to delay each printk during boot.
417 Values larger than 10 seconds (10000) are changed to
418 no delay (0).
419 Format: integer
421 bootmem_debug [KNL] Enable bootmem allocator debug messages.
423 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
424 bttv.radio= Most important insmod options are available as
425 kernel args too.
426 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
427 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
429 BusLogic= [HW,SCSI]
430 See drivers/scsi/BusLogic.c, comment before function
431 BusLogic_ParseDriverOptions().
433 c101= [NET] Moxa C101 synchronous serial card
435 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
436 Sometimes CPU hardware bugs make them report the cache
437 size incorrectly. The kernel will attempt work arounds
438 to fix known problems, but for some CPUs it is not
439 possible to determine what the correct size should be.
440 This option provides an override for these situations.
442 capability.disable=
443 [SECURITY] Disable capabilities. This would normally
444 be used only if an alternative security model is to be
445 configured. Potentially dangerous and should only be
446 used if you are entirely sure of the consequences.
448 ccw_timeout_log [S390]
449 See Documentation/s390/CommonIO for details.
451 cgroup_disable= [KNL] Disable a particular controller
452 Format: {name of the controller(s) to disable}
453 {Currently supported controllers - "memory"}
455 checkreqprot [SELINUX] Set initial checkreqprot flag value.
456 Format: { "0" | "1" }
457 See security/selinux/Kconfig help text.
458 0 -- check protection applied by kernel (includes
459 any implied execute protection).
460 1 -- check protection requested by application.
461 Default value is set via a kernel config option.
462 Value can be changed at runtime via
463 /selinux/checkreqprot.
465 cio_ignore= [S390]
466 See Documentation/s390/CommonIO for details.
468 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
469 [Deprecated]
470 Forces specified clocksource (if available) to be used
471 when calculating gettimeofday(). If specified
472 clocksource is not available, it defaults to PIT.
473 Format: { pit | tsc | cyclone | pmtmr }
475 clocksource= [GENERIC_TIME] Override the default clocksource
476 Format: <string>
477 Override the default clocksource and use the clocksource
478 with the name specified.
479 Some clocksource names to choose from, depending on
480 the platform:
481 [all] jiffies (this is the base, fallback clocksource)
482 [ACPI] acpi_pm
483 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
484 pxa_timer,timer3,32k_counter,timer0_1
485 [AVR32] avr32
486 [X86-32] pit,hpet,tsc,vmi-timer;
487 scx200_hrt on Geode; cyclone on IBM x440
488 [MIPS] MIPS
489 [PARISC] cr16
490 [S390] tod
491 [SH] SuperH
492 [SPARC64] tick
493 [X86-64] hpet,tsc
495 clearcpuid=BITNUM [X86]
496 Disable CPUID feature X for the kernel. See
497 arch/x86/include/asm/cpufeature.h for the valid bit
498 numbers. Note the Linux specific bits are not necessarily
499 stable over kernel options, but the vendor specific
500 ones should be.
501 Also note that user programs calling CPUID directly
502 or using the feature without checking anything
503 will still see it. This just prevents it from
504 being used by the kernel or shown in /proc/cpuinfo.
505 Also note the kernel might malfunction if you disable
506 some critical bits.
508 cmo_free_hint= [PPC] Format: { yes | no }
509 Specify whether pages are marked as being inactive
510 when they are freed. This is used in CMO environments
511 to determine OS memory pressure for page stealing by
512 a hypervisor.
513 Default: yes
515 code_bytes [X86] How many bytes of object code to print
516 in an oops report.
517 Range: 0 - 8192
518 Default: 64
520 com20020= [HW,NET] ARCnet - COM20020 chipset
521 Format:
522 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
524 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
525 Format: <io>[,<irq>]
527 com90xx= [HW,NET]
528 ARCnet - COM90xx chipset (memory-mapped buffers)
529 Format: <io>[,<irq>[,<memstart>]]
531 condev= [HW,S390] console device
532 conmode=
534 console= [KNL] Output console device and options.
536 tty<n> Use the virtual console device <n>.
538 ttyS<n>[,options]
539 ttyUSB0[,options]
540 Use the specified serial port. The options are of
541 the form "bbbbpnf", where "bbbb" is the baud rate,
542 "p" is parity ("n", "o", or "e"), "n" is number of
543 bits, and "f" is flow control ("r" for RTS or
544 omit it). Default is "9600n8".
546 See Documentation/serial-console.txt for more
547 information. See
548 Documentation/networking/netconsole.txt for an
549 alternative.
551 uart[8250],io,<addr>[,options]
552 uart[8250],mmio,<addr>[,options]
553 Start an early, polled-mode console on the 8250/16550
554 UART at the specified I/O port or MMIO address,
555 switching to the matching ttyS device later. The
556 options are the same as for ttyS, above.
558 If the device connected to the port is not a TTY but a braille
559 device, prepend "brl," before the device type, for instance
560 console=brl,ttyS0
561 For now, only VisioBraille is supported.
563 consoleblank= [KNL] The console blank (screen saver) timeout in
564 seconds. Defaults to 10*60 = 10mins. A value of 0
565 disables the blank timer.
567 coredump_filter=
568 [KNL] Change the default value for
569 /proc/<pid>/coredump_filter.
570 See also Documentation/filesystems/proc.txt.
572 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
573 Format:
574 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
576 crashkernel=nn[KMG]@ss[KMG]
577 [KNL] Reserve a chunk of physical memory to
578 hold a kernel to switch to with kexec on panic.
580 crashkernel=range1:size1[,range2:size2,...][@offset]
581 [KNL] Same as above, but depends on the memory
582 in the running system. The syntax of range is
583 start-[end] where start and end are both
584 a memory unit (amount[KMG]). See also
585 Documentation/kdump/kdump.txt for a example.
587 cs89x0_dma= [HW,NET]
588 Format: <dma>
590 cs89x0_media= [HW,NET]
591 Format: { rj45 | aui | bnc }
593 dasd= [HW,NET]
594 See header of drivers/s390/block/dasd_devmap.c.
596 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
597 (one device per port)
598 Format: <port#>,<type>
599 See also Documentation/input/joystick-parport.txt
601 debug [KNL] Enable kernel debugging (events log level).
603 debug_locks_verbose=
604 [KNL] verbose self-tests
605 Format=<0|1>
606 Print debugging info while doing the locking API
607 self-tests.
608 We default to 0 (no extra messages), setting it to
609 1 will print _a lot_ more information - normally
610 only useful to kernel developers.
612 debug_objects [KNL] Enable object debugging
614 no_debug_objects
615 [KNL] Disable object debugging
617 debugpat [X86] Enable PAT debugging
619 decnet.addr= [HW,NET]
620 Format: <area>[,<node>]
621 See also Documentation/networking/decnet.txt.
623 default_hugepagesz=
624 [same as hugepagesz=] The size of the default
625 HugeTLB page size. This is the size represented by
626 the legacy /proc/ hugepages APIs, used for SHM, and
627 default size when mounting hugetlbfs filesystems.
628 Defaults to the default architecture's huge page size
629 if not specified.
631 dhash_entries= [KNL]
632 Set number of hash buckets for dentry cache.
634 digi= [HW,SERIAL]
635 IO parameters + enable/disable command.
637 digiepca= [HW,SERIAL]
638 See drivers/char/README.epca and
639 Documentation/serial/digiepca.txt.
641 disable= [IPV6]
642 See Documentation/networking/ipv6.txt.
644 disable_ipv6= [IPV6]
645 See Documentation/networking/ipv6.txt.
647 disable_mtrr_cleanup [X86]
648 The kernel tries to adjust MTRR layout from continuous
649 to discrete, to make X server driver able to add WB
650 entry later. This parameter disables that.
652 disable_mtrr_trim [X86, Intel and AMD only]
653 By default the kernel will trim any uncacheable
654 memory out of your available memory pool based on
655 MTRR settings. This parameter disables that behavior,
656 possibly causing your machine to run very slowly.
658 disable_timer_pin_1 [X86]
659 Disable PIN 1 of APIC timer
660 Can be useful to work around chipset bugs.
662 dmasound= [HW,OSS] Sound subsystem buffers
664 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
665 this option disables the debugging code at boot.
667 dma_debug_entries=<number>
668 This option allows to tune the number of preallocated
669 entries for DMA-API debugging code. One entry is
670 required per DMA-API allocation. Use this if the
671 DMA-API debugging code disables itself because the
672 architectural default is too low.
674 dma_debug_driver=<driver_name>
675 With this option the DMA-API debugging driver
676 filter feature can be enabled at boot time. Just
677 pass the driver to filter for as the parameter.
678 The filter can be disabled or changed to another
679 driver later using sysfs.
681 dscc4.setup= [NET]
683 dtc3181e= [HW,SCSI]
685 dynamic_printk Enables pr_debug()/dev_dbg() calls if
686 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
687 These can also be switched on/off via
688 <debugfs>/dynamic_printk/modules
690 earlycon= [KNL] Output early console device and options.
691 uart[8250],io,<addr>[,options]
692 uart[8250],mmio,<addr>[,options]
693 Start an early, polled-mode console on the 8250/16550
694 UART at the specified I/O port or MMIO address.
695 The options are the same as for ttyS, above.
697 earlyprintk= [X86,SH,BLACKFIN]
698 earlyprintk=vga
699 earlyprintk=serial[,ttySn[,baudrate]]
700 earlyprintk=ttySn[,baudrate]
701 earlyprintk=dbgp[debugController#]
703 Append ",keep" to not disable it when the real console
704 takes over.
706 Only vga or serial or usb debug port at a time.
708 Currently only ttyS0 and ttyS1 are supported.
710 Interaction with the standard serial driver is not
711 very good.
713 The VGA output is eventually overwritten by the real
714 console.
716 ekgdboc= [X86,KGDB] Allow early kernel console debugging
717 ekgdboc=kbd
719 This is desgined to be used in conjunction with
720 the boot argument: earlyprintk=vga
722 eata= [HW,SCSI]
724 edd= [EDD]
725 Format: {"off" | "on" | "skip[mbr]"}
727 eisa_irq_edge= [PARISC,HW]
728 See header of drivers/parisc/eisa.c.
730 elanfreq= [X86-32]
731 See comment before function elanfreq_setup() in
732 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
734 elevator= [IOSCHED]
735 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
736 See Documentation/block/as-iosched.txt and
737 Documentation/block/deadline-iosched.txt for details.
739 elfcorehdr= [IA64,PPC,SH,X86]
740 Specifies physical address of start of kernel core
741 image elf header. Generally kexec loader will
742 pass this option to capture kernel.
743 See Documentation/kdump/kdump.txt for details.
745 enable_mtrr_cleanup [X86]
746 The kernel tries to adjust MTRR layout from continuous
747 to discrete, to make X server driver able to add WB
748 entry later. This parameter enables that.
750 enable_timer_pin_1 [X86]
751 Enable PIN 1 of APIC timer
752 Can be useful to work around chipset bugs
753 (in particular on some ATI chipsets).
754 The kernel tries to set a reasonable default.
756 enforcing [SELINUX] Set initial enforcing status.
757 Format: {"0" | "1"}
758 See security/selinux/Kconfig help text.
759 0 -- permissive (log only, no denials).
760 1 -- enforcing (deny and log).
761 Default value is 0.
762 Value can be changed at runtime via /selinux/enforce.
764 ether= [HW,NET] Ethernet cards parameters
765 This option is obsoleted by the "netdev=" option, which
766 has equivalent usage. See its documentation for details.
768 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
769 Format: <io>[,<irq>]
771 failslab=
772 fail_page_alloc=
773 fail_make_request=[KNL]
774 General fault injection mechanism.
775 Format: <interval>,<probability>,<space>,<times>
776 See also /Documentation/fault-injection/.
778 fd_mcs= [HW,SCSI]
779 See header of drivers/scsi/fd_mcs.c.
781 fdomain= [HW,SCSI]
782 See header of drivers/scsi/fdomain.c.
784 floppy= [HW]
785 See Documentation/blockdev/floppy.txt.
787 force_pal_cache_flush
788 [IA-64] Avoid check_sal_cache_flush which may hang on
789 buggy SAL_CACHE_FLUSH implementations. Using this
790 parameter will force ia64_sal_cache_flush to call
791 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
793 ftrace=[tracer]
794 [FTRACE] will set and start the specified tracer
795 as early as possible in order to facilitate early
796 boot debugging.
798 ftrace_dump_on_oops[=orig_cpu]
799 [FTRACE] will dump the trace buffers on oops.
800 If no parameter is passed, ftrace will dump
801 buffers of all CPUs, but if you pass orig_cpu, it will
802 dump only the buffer of the CPU that triggered the
803 oops.
805 ftrace_filter=[function-list]
806 [FTRACE] Limit the functions traced by the function
807 tracer at boot up. function-list is a comma separated
808 list of functions. This list can be changed at run
809 time by the set_ftrace_filter file in the debugfs
810 tracing directory.
812 ftrace_notrace=[function-list]
813 [FTRACE] Do not trace the functions specified in
814 function-list. This list can be changed at run time
815 by the set_ftrace_notrace file in the debugfs
816 tracing directory.
818 ftrace_graph_filter=[function-list]
819 [FTRACE] Limit the top level callers functions traced
820 by the function graph tracer at boot up.
821 function-list is a comma separated list of functions
822 that can be changed at run time by the
823 set_graph_function file in the debugfs tracing directory.
825 gamecon.map[2|3]=
826 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
827 support via parallel port (up to 5 devices per port)
828 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
829 See also Documentation/input/joystick-parport.txt
831 gamma= [HW,DRM]
833 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
834 Format: off | on
835 default: on
837 gcov_persist= [GCOV] When non-zero (default), profiling data for
838 kernel modules is saved and remains accessible via
839 debugfs, even when the module is unloaded/reloaded.
840 When zero, profiling data is discarded and associated
841 debugfs files are removed at module unload time.
843 gdth= [HW,SCSI]
844 See header of drivers/scsi/gdth.c.
846 gpt [EFI] Forces disk with valid GPT signature but
847 invalid Protective MBR to be treated as GPT.
849 gvp11= [HW,SCSI]
851 hashdist= [KNL,NUMA] Large hashes allocated during boot
852 are distributed across NUMA nodes. Defaults on
853 for 64bit NUMA, off otherwise.
854 Format: 0 | 1 (for off | on)
856 hcl= [IA-64] SGI's Hardware Graph compatibility layer
858 hd= [EIDE] (E)IDE hard drive subsystem geometry
859 Format: <cyl>,<head>,<sect>
861 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
862 size of <nn>. This works even on boxes that have no
863 highmem otherwise. This also works to reduce highmem
864 size on bigger boxes.
866 highres= [KNL] Enable/disable high resolution timer mode.
867 Valid parameters: "on", "off"
868 Default: "on"
870 hisax= [HW,ISDN]
871 See Documentation/isdn/README.HiSax.
873 hlt [BUGS=ARM,SH]
875 hpet= [X86-32,HPET] option to control HPET usage
876 Format: { enable (default) | disable | force |
877 verbose }
878 disable: disable HPET and use PIT instead
879 force: allow force enabled of undocumented chips (ICH4,
880 VIA, nVidia)
881 verbose: show contents of HPET registers during setup
883 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
884 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
885 On x86-64 and powerpc, this option can be specified
886 multiple times interleaved with hugepages= to reserve
887 huge pages of different sizes. Valid pages sizes on
888 x86-64 are 2M (when the CPU supports "pse") and 1G
889 (when the CPU supports the "pdpe1gb" cpuinfo flag)
890 Note that 1GB pages can only be allocated at boot time
891 using hugepages= and not freed afterwards.
893 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
894 terminal devices. Valid values: 0..8
895 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
896 If specified, z/VM IUCV HVC accepts connections
897 from listed z/VM user IDs only.
899 i2c_bus= [HW] Override the default board specific I2C bus speed
900 or register an additional I2C bus that is not
901 registered from board initialization code.
902 Format:
903 <bus_id>,<clkrate>
905 i8042.debug [HW] Toggle i8042 debug mode
906 i8042.direct [HW] Put keyboard port into non-translated mode
907 i8042.dumbkbd [HW] Pretend that controller can only read data from
908 keyboard and cannot control its state
909 (Don't attempt to blink the leds)
910 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
911 i8042.nokbd [HW] Don't check/create keyboard port
912 i8042.noloop [HW] Disable the AUX Loopback command while probing
913 for the AUX port
914 i8042.nomux [HW] Don't check presence of an active multiplexing
915 controller
916 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
917 controllers
918 i8042.panicblink=
919 [HW] Frequency with which keyboard LEDs should blink
920 when kernel panics (default is 0.5 sec)
921 i8042.reset [HW] Reset the controller during init and cleanup
922 i8042.unlock [HW] Unlock (ignore) the keylock
924 i810= [HW,DRM]
926 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
927 indicates that the driver is running on unsupported
928 hardware.
929 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
930 does not match list of supported models.
931 i8k.power_status
932 [HW] Report power status in /proc/i8k
933 (disabled by default)
934 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
935 capability is set.
937 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
938 See Documentation/mca.txt.
940 icn= [HW,ISDN]
941 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
943 ide-core.nodma= [HW] (E)IDE subsystem
944 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
945 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
946 .cdrom .chs .ignore_cable are additional options
947 See Documentation/ide/ide.txt.
949 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
950 Claim all unknown PCI IDE storage controllers.
952 idle= [X86]
953 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
954 Poll forces a polling idle loop that can slightly
955 improve the performance of waking up a idle CPU, but
956 will use a lot of power and make the system run hot.
957 Not recommended.
958 idle=mwait: On systems which support MONITOR/MWAIT but
959 the kernel chose to not use it because it doesn't save
960 as much power as a normal idle loop, use the
961 MONITOR/MWAIT idle loop anyways. Performance should be
962 the same as idle=poll.
963 idle=halt: Halt is forced to be used for CPU idle.
964 In such case C2/C3 won't be used again.
965 idle=nomwait: Disable mwait for CPU C-states
967 ignore_loglevel [KNL]
968 Ignore loglevel setting - this will print /all/
969 kernel messages to the console. Useful for debugging.
971 ihash_entries= [KNL]
972 Set number of hash buckets for inode cache.
974 ima_audit= [IMA]
975 Format: { "0" | "1" }
976 0 -- integrity auditing messages. (Default)
977 1 -- enable informational integrity auditing messages.
979 ima_hash= [IMA]
980 Format: { "sha1" | "md5" }
981 default: "sha1"
983 ima_tcb [IMA]
984 Load a policy which meets the needs of the Trusted
985 Computing Base. This means IMA will measure all
986 programs exec'd, files mmap'd for exec, and all files
987 opened for read by uid=0.
989 in2000= [HW,SCSI]
990 See header of drivers/scsi/in2000.c.
992 init= [KNL]
993 Format: <full_path>
994 Run specified binary instead of /sbin/init as init
995 process.
997 initcall_debug [KNL] Trace initcalls as they are executed. Useful
998 for working out where the kernel is dying during
999 startup.
1001 initrd= [BOOT] Specify the location of the initial ramdisk
1003 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1004 Format: <irq>
1006 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1007 on
1008 Enable intel iommu driver.
1009 off
1010 Disable intel iommu driver.
1011 igfx_off [Default Off]
1012 By default, gfx is mapped as normal device. If a gfx
1013 device has a dedicated DMAR unit, the DMAR unit is
1014 bypassed by not enabling DMAR with this option. In
1015 this case, gfx device will use physical address for
1016 DMA.
1017 forcedac [x86_64]
1018 With this option iommu will not optimize to look
1019 for io virtual address below 32 bit forcing dual
1020 address cycle on pci bus for cards supporting greater
1021 than 32 bit addressing. The default is to look
1022 for translation below 32 bit and if not available
1023 then look in the higher range.
1024 strict [Default Off]
1025 With this option on every unmap_single operation will
1026 result in a hardware IOTLB flush operation as opposed
1027 to batching them for performance.
1029 inttest= [IA64]
1031 iomem= Disable strict checking of access to MMIO memory
1032 strict regions from userspace.
1033 relaxed
1035 iommu= [x86]
1036 off
1037 force
1038 noforce
1039 biomerge
1040 panic
1041 nopanic
1042 merge
1043 nomerge
1044 forcesac
1045 soft
1046 pt [x86, IA64]
1048 io7= [HW] IO7 for Marvel based alpha systems
1049 See comment before marvel_specify_io7 in
1050 arch/alpha/kernel/core_marvel.c.
1052 io_delay= [X86] I/O delay method
1053 0x80
1054 Standard port 0x80 based delay
1055 0xed
1056 Alternate port 0xed based delay (needed on some systems)
1057 udelay
1058 Simple two microseconds delay
1059 none
1060 No delay
1062 ip= [IP_PNP]
1063 See Documentation/filesystems/nfs/nfsroot.txt.
1065 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1066 See comment before ip2_setup() in
1067 drivers/char/ip2/ip2base.c.
1069 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1070 See header of drivers/scsi/ips.c.
1072 irqfixup [HW]
1073 When an interrupt is not handled search all handlers
1074 for it. Intended to get systems with badly broken
1075 firmware running.
1077 irqpoll [HW]
1078 When an interrupt is not handled search all handlers
1079 for it. Also check all handlers each timer
1080 interrupt. Intended to get systems with badly broken
1081 firmware running.
1083 isapnp= [ISAPNP]
1084 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1086 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1087 Format:
1088 <cpu number>,...,<cpu number>
1089 or
1090 <cpu number>-<cpu number>
1091 (must be a positive range in ascending order)
1092 or a mixture
1093 <cpu number>,...,<cpu number>-<cpu number>
1095 This option can be used to specify one or more CPUs
1096 to isolate from the general SMP balancing and scheduling
1097 algorithms. You can move a process onto or off an
1098 "isolated" CPU via the CPU affinity syscalls or cpuset.
1099 <cpu number> begins at 0 and the maximum value is
1100 "number of CPUs in system - 1".
1102 This option is the preferred way to isolate CPUs. The
1103 alternative -- manually setting the CPU mask of all
1104 tasks in the system -- can cause problems and
1105 suboptimal load balancer performance.
1107 iucv= [HW,NET]
1109 js= [HW,JOY] Analog joystick
1110 See Documentation/input/joystick.txt.
1112 keepinitrd [HW,ARM]
1114 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1115 specifies the amount of memory usable by the kernel
1116 for non-movable allocations. The requested amount is
1117 spread evenly throughout all nodes in the system. The
1118 remaining memory in each node is used for Movable
1119 pages. In the event, a node is too small to have both
1120 kernelcore and Movable pages, kernelcore pages will
1121 take priority and other nodes will have a larger number
1122 of kernelcore pages. The Movable zone is used for the
1123 allocation of pages that may be reclaimed or moved
1124 by the page migration subsystem. This means that
1125 HugeTLB pages may not be allocated from this zone.
1126 Note that allocations like PTEs-from-HighMem still
1127 use the HighMem zone if it exists, and the Normal
1128 zone if it does not.
1130 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1131 Format: <Controller#>[,poll interval]
1132 The controller # is the number of the ehci usb debug
1133 port as it is probed via PCI. The poll interval is
1134 optional and is the number seconds in between
1135 each poll cycle to the debug port in case you need
1136 the functionality for interrupting the kernel with
1137 gdb or control-c on the dbgp connection. When
1138 not using this parameter you use sysrq-g to break into
1139 the kernel debugger.
1141 kgdboc= [KGDB,HW] kgdb over consoles.
1142 Requires a tty driver that supports console polling,
1143 or a supported polling keyboard driver (non-usb).
1144 Serial only format: <serial_device>[,baud]
1145 keyboard only format: kbd
1146 keyboard and serial format: kbd,<serial_device>[,baud]
1148 kgdbwait [KGDB] Stop kernel execution and enter the
1149 kernel debugger at the earliest opportunity.
1151 kmac= [MIPS] korina ethernet MAC address.
1152 Configure the RouterBoard 532 series on-chip
1153 Ethernet adapter MAC address.
1155 kmemleak= [KNL] Boot-time kmemleak enable/disable
1156 Valid arguments: on, off
1157 Default: on
1159 kstack=N [X86] Print N words from the kernel stack
1160 in oops dumps.
1162 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1163 Default is 0 (don't ignore, but inject #GP)
1165 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1166 Default is 1 (enabled)
1168 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1169 Default is 0 (off)
1171 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1172 for all guests.
1173 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1175 kvm-intel.bypass_guest_pf=
1176 [KVM,Intel] Disables bypassing of guest page faults
1177 on Intel chips. Default is 1 (enabled)
1179 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1180 (virtualized MMU) support on capable Intel chips.
1181 Default is 1 (enabled)
1183 kvm-intel.emulate_invalid_guest_state=
1184 [KVM,Intel] Enable emulation of invalid guest states
1185 Default is 0 (disabled)
1187 kvm-intel.flexpriority=
1188 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1189 Default is 1 (enabled)
1191 kvm-intel.unrestricted_guest=
1192 [KVM,Intel] Disable unrestricted guest feature
1193 (virtualized real and unpaged mode) on capable
1194 Intel chips. Default is 1 (enabled)
1196 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1197 feature (tagged TLBs) on capable Intel chips.
1198 Default is 1 (enabled)
1200 l2cr= [PPC]
1202 l3cr= [PPC]
1204 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1205 disabled it.
1207 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1208 in C2 power state.
1210 libata.dma= [LIBATA] DMA control
1211 libata.dma=0 Disable all PATA and SATA DMA
1212 libata.dma=1 PATA and SATA Disk DMA only
1213 libata.dma=2 ATAPI (CDROM) DMA only
1214 libata.dma=4 Compact Flash DMA only
1215 Combinations also work, so libata.dma=3 enables DMA
1216 for disks and CDROMs, but not CFs.
1218 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1219 libata.ignore_hpa=0 keep BIOS limits (default)
1220 libata.ignore_hpa=1 ignore limits, using full disk
1222 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1223 when set.
1224 Format: <int>
1226 libata.force= [LIBATA] Force configurations. The format is comma
1227 separated list of "[ID:]VAL" where ID is
1228 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1229 matching port, link or device. Basically, it matches
1230 the ATA ID string printed on console by libata. If
1231 the whole ID part is omitted, the last PORT and DEVICE
1232 values are used. If ID hasn't been specified yet, the
1233 configuration applies to all ports, links and devices.
1235 If only DEVICE is omitted, the parameter applies to
1236 the port and all links and devices behind it. DEVICE
1237 number of 0 either selects the first device or the
1238 first fan-out link behind PMP device. It does not
1239 select the host link. DEVICE number of 15 selects the
1240 host link and device attached to it.
1242 The VAL specifies the configuration to force. As long
1243 as there's no ambiguity shortcut notation is allowed.
1244 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1245 The following configurations can be forced.
1247 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1248 Any ID with matching PORT is used.
1250 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1252 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1253 udma[/][16,25,33,44,66,100,133] notation is also
1254 allowed.
1256 * [no]ncq: Turn on or off NCQ.
1258 * nohrst, nosrst, norst: suppress hard, soft
1259 and both resets.
1261 If there are multiple matching configurations changing
1262 the same attribute, the last one is used.
1264 lmb=debug [KNL] Enable lmb debug messages.
1266 load_ramdisk= [RAM] List of ramdisks to load from floppy
1267 See Documentation/blockdev/ramdisk.txt.
1269 lockd.nlm_grace_period=P [NFS] Assign grace period.
1270 Format: <integer>
1272 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1273 Format: <integer>
1275 lockd.nlm_timeout=T [NFS] Assign timeout value.
1276 Format: <integer>
1278 lockd.nlm_udpport=M [NFS] Assign UDP port.
1279 Format: <integer>
1281 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1282 Format: <irq>
1284 loglevel= All Kernel Messages with a loglevel smaller than the
1285 console loglevel will be printed to the console. It can
1286 also be changed with klogd or other programs. The
1287 loglevels are defined as follows:
1289 0 (KERN_EMERG) system is unusable
1290 1 (KERN_ALERT) action must be taken immediately
1291 2 (KERN_CRIT) critical conditions
1292 3 (KERN_ERR) error conditions
1293 4 (KERN_WARNING) warning conditions
1294 5 (KERN_NOTICE) normal but significant condition
1295 6 (KERN_INFO) informational
1296 7 (KERN_DEBUG) debug-level messages
1298 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1299 Format: { n | nk | nM }
1300 n must be a power of two. The default size
1301 is set in the kernel config file.
1303 logo.nologo [FB] Disables display of the built-in Linux logo.
1304 This may be used to provide more screen space for
1305 kernel log messages and is useful when debugging
1306 kernel boot problems.
1308 lp=0 [LP] Specify parallel ports to use, e.g,
1309 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1310 lp=reset first parallel port). 'lp=0' disables the
1311 lp=auto printer driver. 'lp=reset' (which can be
1312 specified in addition to the ports) causes
1313 attached printers to be reset. Using
1314 lp=port1,port2,... specifies the parallel ports
1315 to associate lp devices with, starting with
1316 lp0. A port specification may be 'none' to skip
1317 that lp device, or a parport name such as
1318 'parport0'. Specifying 'lp=auto' instead of a
1319 port specification list means that device IDs
1320 from each port should be examined, to see if
1321 an IEEE 1284-compliant printer is attached; if
1322 so, the driver will manage that printer.
1323 See also header of drivers/char/lp.c.
1325 lpj=n [KNL]
1326 Sets loops_per_jiffy to given constant, thus avoiding
1327 time-consuming boot-time autodetection (up to 250 ms per
1328 CPU). 0 enables autodetection (default). To determine
1329 the correct value for your kernel, boot with normal
1330 autodetection and see what value is printed. Note that
1331 on SMP systems the preset will be applied to all CPUs,
1332 which is likely to cause problems if your CPUs need
1333 significantly divergent settings. An incorrect value
1334 will cause delays in the kernel to be wrong, leading to
1335 unpredictable I/O errors and other breakage. Although
1336 unlikely, in the extreme case this might damage your
1337 hardware.
1339 ltpc= [NET]
1340 Format: <io>,<irq>,<dma>
1342 mac5380= [HW,SCSI] Format:
1343 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1345 machvec= [IA64] Force the use of a particular machine-vector
1346 (machvec) in a generic kernel.
1347 Example: machvec=hpzx1_swiotlb
1349 machtype= [Loongson] Share the same kernel image file between different
1350 yeeloong laptop.
1351 Example: machtype=lemote-yeeloong-2f-7inch
1353 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1354 than or equal to this physical address is ignored.
1356 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1357 should make use of. maxcpus=n : n >= 0 limits the
1358 kernel to using 'n' processors. n=0 is a special case,
1359 it is equivalent to "nosmp", which also disables
1360 the IO APIC.
1362 max_loop= [LOOP] Maximum number of loopback devices that can
1363 be mounted
1364 Format: <1-256>
1366 max_luns= [SCSI] Maximum number of LUNs to probe.
1367 Should be between 1 and 2^32-1.
1369 max_report_luns=
1370 [SCSI] Maximum number of LUNs received.
1371 Should be between 1 and 16384.
1373 mcatest= [IA-64]
1375 mce [X86-32] Machine Check Exception
1377 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1379 md= [HW] RAID subsystems devices and level
1380 See Documentation/md.txt.
1382 mdacon= [MDA]
1383 Format: <first>,<last>
1384 Specifies range of consoles to be captured by the MDA.
1386 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1387 Amount of memory to be used when the kernel is not able
1388 to see the whole system memory or for test.
1389 [X86-32] Use together with memmap= to avoid physical
1390 address space collisions. Without memmap= PCI devices
1391 could be placed at addresses belonging to unused RAM.
1393 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1394 memory.
1396 memchunk=nn[KMG]
1397 [KNL,SH] Allow user to override the default size for
1398 per-device physically contiguous DMA buffers.
1400 memmap=exactmap [KNL,X86] Enable setting of an exact
1401 E820 memory map, as specified by the user.
1402 Such memmap=exactmap lines can be constructed based on
1403 BIOS output or other requirements. See the memmap=nn@ss
1404 option description.
1406 memmap=nn[KMG]@ss[KMG]
1407 [KNL] Force usage of a specific region of memory
1408 Region of memory to be used, from ss to ss+nn.
1410 memmap=nn[KMG]#ss[KMG]
1411 [KNL,ACPI] Mark specific memory as ACPI data.
1412 Region of memory to be used, from ss to ss+nn.
1414 memmap=nn[KMG]$ss[KMG]
1415 [KNL,ACPI] Mark specific memory as reserved.
1416 Region of memory to be used, from ss to ss+nn.
1417 Example: Exclude memory from 0x18690000-0x1869ffff
1418 memmap=64K$0x18690000
1419 or
1420 memmap=0x10000$0x18690000
1422 memory_corruption_check=0/1 [X86]
1423 Some BIOSes seem to corrupt the first 64k of
1424 memory when doing things like suspend/resume.
1425 Setting this option will scan the memory
1426 looking for corruption. Enabling this will
1427 both detect corruption and prevent the kernel
1428 from using the memory being corrupted.
1429 However, its intended as a diagnostic tool; if
1430 repeatable BIOS-originated corruption always
1431 affects the same memory, you can use memmap=
1432 to prevent the kernel from using that memory.
1434 memory_corruption_check_size=size [X86]
1435 By default it checks for corruption in the low
1436 64k, making this memory unavailable for normal
1437 use. Use this parameter to scan for
1438 corruption in more or less memory.
1440 memory_corruption_check_period=seconds [X86]
1441 By default it checks for corruption every 60
1442 seconds. Use this parameter to check at some
1443 other rate. 0 disables periodic checking.
1445 memtest= [KNL,X86] Enable memtest
1446 Format: <integer>
1447 default : 0 <disable>
1448 Specifies the number of memtest passes to be
1449 performed. Each pass selects another test
1450 pattern from a given set of patterns. Memtest
1451 fills the memory with this pattern, validates
1452 memory contents and reserves bad memory
1453 regions that are detected.
1455 meye.*= [HW] Set MotionEye Camera parameters
1456 See Documentation/video4linux/meye.txt.
1458 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1459 Multi-Function General Purpose Timers on AMD Geode
1460 platforms.
1462 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1463 the BIOS has incorrectly applied a workaround. TinyBIOS
1464 version 0.98 is known to be affected, 0.99 fixes the
1465 problem by letting the user disable the workaround.
1467 mga= [HW,DRM]
1469 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1470 physical address is ignored.
1472 mini2440= [ARM,HW,KNL]
1473 Format:[0..2][b][c][t]
1474 Default: "0tb"
1475 MINI2440 configuration specification:
1476 0 - The attached screen is the 3.5" TFT
1477 1 - The attached screen is the 7" TFT
1478 2 - The VGA Shield is attached (1024x768)
1479 Leaving out the screen size parameter will not load
1480 the TFT driver, and the framebuffer will be left
1481 unconfigured.
1482 b - Enable backlight. The TFT backlight pin will be
1483 linked to the kernel VESA blanking code and a GPIO
1484 LED. This parameter is not necessary when using the
1485 VGA shield.
1486 c - Enable the s3c camera interface.
1487 t - Reserved for enabling touchscreen support. The
1488 touchscreen support is not enabled in the mainstream
1489 kernel as of 2.6.30, a preliminary port can be found
1490 in the "bleeding edge" mini2440 support kernel at
1491 http://repo.or.cz/w/linux-2.6/mini2440.git
1493 mminit_loglevel=
1494 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1495 parameter allows control of the logging verbosity for
1496 the additional memory initialisation checks. A value
1497 of 0 disables mminit logging and a level of 4 will
1498 log everything. Information is printed at KERN_DEBUG
1499 so loglevel=8 may also need to be specified.
1501 mousedev.tap_time=
1502 [MOUSE] Maximum time between finger touching and
1503 leaving touchpad surface for touch to be considered
1504 a tap and be reported as a left button click (for
1505 touchpads working in absolute mode only).
1506 Format: <msecs>
1507 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1508 reporting absolute coordinates, such as tablets
1509 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1510 reporting absolute coordinates, such as tablets
1512 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1513 is similar to kernelcore except it specifies the
1514 amount of memory used for migratable allocations.
1515 If both kernelcore and movablecore is specified,
1516 then kernelcore will be at *least* the specified
1517 value but may be more. If movablecore on its own
1518 is specified, the administrator must be careful
1519 that the amount of memory usable for all allocations
1520 is not too small.
1522 mpu401= [HW,OSS]
1523 Format: <io>,<irq>
1525 MTD_Partition= [MTD]
1526 Format: <name>,<region-number>,<size>,<offset>
1528 MTD_Region= [MTD] Format:
1529 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1531 mtdparts= [MTD]
1532 See drivers/mtd/cmdlinepart.c.
1534 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1536 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1538 boundary - index of last SLC block on Flex-OneNAND.
1539 The remaining blocks are configured as MLC blocks.
1540 lock - Configure if Flex-OneNAND boundary should be locked.
1541 Once locked, the boundary cannot be changed.
1542 1 indicates lock status, 0 indicates unlock status.
1544 mtdset= [ARM]
1545 ARM/S3C2412 JIVE boot control
1547 See arch/arm/mach-s3c2412/mach-jive.c
1549 mtouchusb.raw_coordinates=
1550 [HW] Make the MicroTouch USB driver use raw coordinates
1551 ('y', default) or cooked coordinates ('n')
1553 mtrr_chunk_size=nn[KMG] [X86]
1554 used for mtrr cleanup. It is largest continuous chunk
1555 that could hold holes aka. UC entries.
1557 mtrr_gran_size=nn[KMG] [X86]
1558 Used for mtrr cleanup. It is granularity of mtrr block.
1559 Default is 1.
1560 Large value could prevent small alignment from
1561 using up MTRRs.
1563 mtrr_spare_reg_nr=n [X86]
1564 Format: <integer>
1565 Range: 0,7 : spare reg number
1566 Default : 1
1567 Used for mtrr cleanup. It is spare mtrr entries number.
1568 Set to 2 or more if your graphical card needs more.
1570 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1572 NCR_D700= [HW,SCSI]
1573 See header of drivers/scsi/NCR_D700.c.
1575 ncr5380= [HW,SCSI]
1577 ncr53c400= [HW,SCSI]
1579 ncr53c400a= [HW,SCSI]
1581 ncr53c406a= [HW,SCSI]
1583 ncr53c8xx= [HW,SCSI]
1585 netdev= [NET] Network devices parameters
1586 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1587 Note that mem_start is often overloaded to mean
1588 something different and driver-specific.
1589 This usage is only documented in each driver source
1590 file if at all.
1592 nf_conntrack.acct=
1593 [NETFILTER] Enable connection tracking flow accounting
1594 0 to disable accounting
1595 1 to enable accounting
1596 Default value depends on CONFIG_NF_CT_ACCT that is
1597 going to be removed in 2.6.29.
1599 nfsaddrs= [NFS]
1600 See Documentation/filesystems/nfs/nfsroot.txt.
1602 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1603 See Documentation/filesystems/nfs/nfsroot.txt.
1605 nfs.callback_tcpport=
1606 [NFS] set the TCP port on which the NFSv4 callback
1607 channel should listen.
1609 nfs.cache_getent=
1610 [NFS] sets the pathname to the program which is used
1611 to update the NFS client cache entries.
1613 nfs.cache_getent_timeout=
1614 [NFS] sets the timeout after which an attempt to
1615 update a cache entry is deemed to have failed.
1617 nfs.idmap_cache_timeout=
1618 [NFS] set the maximum lifetime for idmapper cache
1619 entries.
1621 nfs.enable_ino64=
1622 [NFS] enable 64-bit inode numbers.
1623 If zero, the NFS client will fake up a 32-bit inode
1624 number for the readdir() and stat() syscalls instead
1625 of returning the full 64-bit number.
1626 The default is to return 64-bit inode numbers.
1628 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1629 when a NMI is triggered.
1630 Format: [state][,regs][,debounce][,die]
1632 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1633 Format: [panic,][num]
1634 Valid num: 0,1,2
1635 0 - turn nmi_watchdog off
1636 1 - use the IO-APIC timer for the NMI watchdog
1637 2 - use the local APIC for the NMI watchdog using
1638 a performance counter. Note: This will use one
1639 performance counter and the local APIC's performance
1640 vector.
1641 When panic is specified, panic when an NMI watchdog
1642 timeout occurs.
1643 This is useful when you use a panic=... timeout and
1644 need the box quickly up again.
1645 Instead of 1 and 2 it is possible to use the following
1646 symbolic names: lapic and ioapic
1647 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1649 netpoll.carrier_timeout=
1650 [NET] Specifies amount of time (in seconds) that
1651 netpoll should wait for a carrier. By default netpoll
1652 waits 4 seconds.
1654 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1655 emulation library even if a 387 maths coprocessor
1656 is present.
1658 no_console_suspend
1659 [HW] Never suspend the console
1660 Disable suspending of consoles during suspend and
1661 hibernate operations. Once disabled, debugging
1662 messages can reach various consoles while the rest
1663 of the system is being put to sleep (ie, while
1664 debugging driver suspend/resume hooks). This may
1665 not work reliably with all consoles, but is known
1666 to work with serial and VGA consoles.
1668 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1669 caches in the slab allocator. Saves per-node memory,
1670 but will impact performance.
1672 noalign [KNL,ARM]
1674 noapic [SMP,APIC] Tells the kernel to not make use of any
1675 IOAPICs that may be present in the system.
1677 nobats [PPC] Do not use BATs for mapping kernel lowmem
1678 on "Classic" PPC cores.
1680 nocache [ARM]
1682 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1684 nodelayacct [KNL] Disable per-task delay accounting
1686 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1688 nodsp [SH] Disable hardware DSP at boot time.
1690 noefi [X86] Disable EFI runtime services support.
1692 noexec [IA-64]
1694 noexec [X86]
1695 On X86-32 available only on PAE configured kernels.
1696 noexec=on: enable non-executable mappings (default)
1697 noexec=off: disable non-executable mappings
1699 noexec32 [X86-64]
1700 This affects only 32-bit executables.
1701 noexec32=on: enable non-executable mappings (default)
1702 read doesn't imply executable mappings
1703 noexec32=off: disable non-executable mappings
1704 read implies executable mappings
1706 nofpu [SH] Disable hardware FPU at boot time.
1708 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1709 register save and restore. The kernel will only save
1710 legacy floating-point registers on task switch.
1712 noxsave [BUGS=X86] Disables x86 extended register state save
1713 and restore using xsave. The kernel will fallback to
1714 enabling legacy floating-point and sse state.
1716 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1717 wfi(ARM) instruction doesn't work correctly and not to
1718 use it. This is also useful when using JTAG debugger.
1720 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1721 instruction doesn't work correctly and not to
1722 use it.
1724 no_file_caps Tells the kernel not to honor file capabilities. The
1725 only way then for a file to be executed with privilege
1726 is to be setuid root or executed by root.
1728 nohalt [IA-64] Tells the kernel not to use the power saving
1729 function PAL_HALT_LIGHT when idle. This increases
1730 power-consumption. On the positive side, it reduces
1731 interrupt wake-up latency, which may improve performance
1732 in certain environments such as networked servers or
1733 real-time systems.
1735 nohz= [KNL] Boottime enable/disable dynamic ticks
1736 Valid arguments: on, off
1737 Default: on
1739 noiotrap [SH] Disables trapped I/O port accesses.
1741 noirqdebug [X86-32] Disables the code which attempts to detect and
1742 disable unhandled interrupt sources.
1744 no_timer_check [X86,APIC] Disables the code which tests for
1745 broken timer IRQ sources.
1747 noisapnp [ISAPNP] Disables ISA PnP code.
1749 noinitrd [RAM] Tells the kernel not to load any configured
1750 initial RAM disk.
1752 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1753 remapping.
1755 nointroute [IA-64]
1757 nojitter [IA64] Disables jitter checking for ITC timers.
1759 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1761 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1763 noltlbs [PPC] Do not use large page/tlb entries for kernel
1764 lowmem mapping on PPC40x.
1766 nomca [IA-64] Disable machine check abort handling
1768 nomce [X86-32] Machine Check Exception
1770 nomfgpt [X86-32] Disable Multi-Function General Purpose
1771 Timer usage (for AMD Geode machines).
1773 nopat [X86] Disable PAT (page attribute table extension of
1774 pagetables) support.
1776 norandmaps Don't use address space randomization. Equivalent to
1777 echo 0 > /proc/sys/kernel/randomize_va_space
1779 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1781 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1782 with UP alternatives
1784 noresidual [PPC] Don't use residual data on PReP machines.
1786 noresume [SWSUSP] Disables resume and restores original swap
1787 space.
1789 no-scroll [VGA] Disables scrollback.
1790 This is required for the Braillex ib80-piezo Braille
1791 reader made by F.H. Papenmeier (Germany).
1793 nosbagart [IA-64]
1795 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1797 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1798 and disable the IO APIC. legacy for "maxcpus=0".
1800 nosoftlockup [KNL] Disable the soft-lockup detector.
1802 noswapaccount [KNL] Disable accounting of swap in memory resource
1803 controller. (See Documentation/cgroups/memory.txt)
1805 nosync [HW,M68K] Disables sync negotiation for all devices.
1807 notsc [BUGS=X86-32] Disable Time Stamp Counter
1809 nousb [USB] Disable the USB subsystem
1811 nowb [ARM]
1813 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1815 nptcg= [IA64] Override max number of concurrent global TLB
1816 purges which is reported from either PAL_VM_SUMMARY or
1817 SAL PALO.
1819 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1820 could support. nr_cpus=n : n >= 1 limits the kernel to
1821 supporting 'n' processors. Later in runtime you can not
1822 use hotplug cpu feature to put more cpu back to online.
1823 just like you compile the kernel NR_CPUS=n
1825 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1827 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1828 one of ['zone', 'node', 'default'] can be specified
1829 This can be set from sysctl after boot.
1830 See Documentation/sysctl/vm.txt for details.
1832 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1833 See Documentation/debugging-via-ohci1394.txt for more
1834 info.
1836 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1837 Rather than timing out after 20 ms if an EC
1838 command is not properly ACKed, override the length
1839 of the timeout. We have interrupts disabled while
1840 waiting for the ACK, so if this is set too high
1841 interrupts *may* be lost!
1843 omap_mux= [OMAP] Override bootloader pin multiplexing.
1844 Format: <mux_mode0.mode_name=value>...
1845 For example, to override I2C bus2:
1846 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1848 opl3= [HW,OSS]
1849 Format: <io>
1851 oprofile.timer= [HW]
1852 Use timer interrupt instead of performance counters
1854 oprofile.cpu_type= Force an oprofile cpu type
1855 This might be useful if you have an older oprofile
1856 userland or if you want common events.
1857 Format: { arch_perfmon }
1858 arch_perfmon: [X86] Force use of architectural
1859 perfmon on Intel CPUs instead of the
1860 CPU specific event set.
1862 osst= [HW,SCSI] SCSI Tape Driver
1863 Format: <buffer_size>,<write_threshold>
1864 See also Documentation/scsi/st.txt.
1866 panic= [KNL] Kernel behaviour on panic
1867 Format: <timeout>
1869 parkbd.port= [HW] Parallel port number the keyboard adapter is
1870 connected to, default is 0.
1871 Format: <parport#>
1872 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1873 0 for XT, 1 for AT (default is AT).
1874 Format: <mode>
1876 parport= [HW,PPT] Specify parallel ports. 0 disables.
1877 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1878 Use 'auto' to force the driver to use any
1879 IRQ/DMA settings detected (the default is to
1880 ignore detected IRQ/DMA settings because of
1881 possible conflicts). You can specify the base
1882 address, IRQ, and DMA settings; IRQ and DMA
1883 should be numbers, or 'auto' (for using detected
1884 settings on that particular port), or 'nofifo'
1885 (to avoid using a FIFO even if it is detected).
1886 Parallel ports are assigned in the order they
1887 are specified on the command line, starting
1888 with parport0.
1890 parport_init_mode= [HW,PPT]
1891 Configure VIA parallel port to operate in
1892 a specific mode. This is necessary on Pegasos
1893 computer where firmware has no options for setting
1894 up parallel port mode and sets it to spp.
1895 Currently this function knows 686a and 8231 chips.
1896 Format: [spp|ps2|epp|ecp|ecpepp]
1898 pas2= [HW,OSS] Format:
1899 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1901 pas16= [HW,SCSI]
1902 See header of drivers/scsi/pas16.c.
1904 pause_on_oops=
1905 Halt all CPUs after the first oops has been printed for
1906 the specified number of seconds. This is to be used if
1907 your oopses keep scrolling off the screen.
1909 pcbit= [HW,ISDN]
1911 pcd. [PARIDE]
1912 See header of drivers/block/paride/pcd.c.
1913 See also Documentation/blockdev/paride.txt.
1915 pci=option[,option...] [PCI] various PCI subsystem options:
1916 earlydump [X86] dump PCI config space before the kernel
1917 changes anything
1918 off [X86] don't probe for the PCI bus
1919 bios [X86-32] force use of PCI BIOS, don't access
1920 the hardware directly. Use this if your machine
1921 has a non-standard PCI host bridge.
1922 nobios [X86-32] disallow use of PCI BIOS, only direct
1923 hardware access methods are allowed. Use this
1924 if you experience crashes upon bootup and you
1925 suspect they are caused by the BIOS.
1926 conf1 [X86] Force use of PCI Configuration
1927 Mechanism 1.
1928 conf2 [X86] Force use of PCI Configuration
1929 Mechanism 2.
1930 noaer [PCIE] If the PCIEAER kernel config parameter is
1931 enabled, this kernel boot option can be used to
1932 disable the use of PCIE advanced error reporting.
1933 nodomains [PCI] Disable support for multiple PCI
1934 root domains (aka PCI segments, in ACPI-speak).
1935 nommconf [X86] Disable use of MMCONFIG for PCI
1936 Configuration
1937 check_enable_amd_mmconf [X86] check for and enable
1938 properly configured MMIO access to PCI
1939 config space on AMD family 10h CPU
1940 nomsi [MSI] If the PCI_MSI kernel config parameter is
1941 enabled, this kernel boot option can be used to
1942 disable the use of MSI interrupts system-wide.
1943 noioapicquirk [APIC] Disable all boot interrupt quirks.
1944 Safety option to keep boot IRQs enabled. This
1945 should never be necessary.
1946 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1947 primary IO-APIC for bridges that cannot disable
1948 boot IRQs. This fixes a source of spurious IRQs
1949 when the system masks IRQs.
1950 noioapicreroute [APIC] Disable workaround that uses the
1951 boot IRQ equivalent of an IRQ that connects to
1952 a chipset where boot IRQs cannot be disabled.
1953 The opposite of ioapicreroute.
1954 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1955 routing table. These calls are known to be buggy
1956 on several machines and they hang the machine
1957 when used, but on other computers it's the only
1958 way to get the interrupt routing table. Try
1959 this option if the kernel is unable to allocate
1960 IRQs or discover secondary PCI buses on your
1961 motherboard.
1962 rom [X86] Assign address space to expansion ROMs.
1963 Use with caution as certain devices share
1964 address decoders between ROMs and other
1965 resources.
1966 norom [X86] Do not assign address space to
1967 expansion ROMs that do not already have
1968 BIOS assigned address ranges.
1969 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1970 assigned automatically to PCI devices. You can
1971 make the kernel exclude IRQs of your ISA cards
1972 this way.
1973 pirqaddr=0xAAAAA [X86] Specify the physical address
1974 of the PIRQ table (normally generated
1975 by the BIOS) if it is outside the
1976 F0000h-100000h range.
1977 lastbus=N [X86] Scan all buses thru bus #N. Can be
1978 useful if the kernel is unable to find your
1979 secondary buses and you want to tell it
1980 explicitly which ones they are.
1981 assign-busses [X86] Always assign all PCI bus
1982 numbers ourselves, overriding
1983 whatever the firmware may have done.
1984 usepirqmask [X86] Honor the possible IRQ mask stored
1985 in the BIOS $PIR table. This is needed on
1986 some systems with broken BIOSes, notably
1987 some HP Pavilion N5400 and Omnibook XE3
1988 notebooks. This will have no effect if ACPI
1989 IRQ routing is enabled.
1990 noacpi [X86] Do not use ACPI for IRQ routing
1991 or for PCI scanning.
1992 use_crs [X86] Use PCI host bridge window information
1993 from ACPI. On BIOSes from 2008 or later, this
1994 is enabled by default. If you need to use this,
1995 please report a bug.
1996 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1997 If you need to use this, please report a bug.
1998 routeirq Do IRQ routing for all PCI devices.
1999 This is normally done in pci_enable_device(),
2000 so this option is a temporary workaround
2001 for broken drivers that don't call it.
2002 skip_isa_align [X86] do not align io start addr, so can
2003 handle more pci cards
2004 firmware [ARM] Do not re-enumerate the bus but instead
2005 just use the configuration from the
2006 bootloader. This is currently used on
2007 IXP2000 systems where the bus has to be
2008 configured a certain way for adjunct CPUs.
2009 noearly [X86] Don't do any early type 1 scanning.
2010 This might help on some broken boards which
2011 machine check when some devices' config space
2012 is read. But various workarounds are disabled
2013 and some IOMMU drivers will not work.
2014 bfsort Sort PCI devices into breadth-first order.
2015 This sorting is done to get a device
2016 order compatible with older (<= 2.4) kernels.
2017 nobfsort Don't sort PCI devices into breadth-first order.
2018 cbiosize=nn[KMG] The fixed amount of bus space which is
2019 reserved for the CardBus bridge's IO window.
2020 The default value is 256 bytes.
2021 cbmemsize=nn[KMG] The fixed amount of bus space which is
2022 reserved for the CardBus bridge's memory
2023 window. The default value is 64 megabytes.
2024 resource_alignment=
2025 Format:
2026 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2027 Specifies alignment and device to reassign
2028 aligned memory resources.
2029 If <order of align> is not specified,
2030 PAGE_SIZE is used as alignment.
2031 PCI-PCI bridge can be specified, if resource
2032 windows need to be expanded.
2033 ecrc= Enable/disable PCIe ECRC (transaction layer
2034 end-to-end CRC checking).
2035 bios: Use BIOS/firmware settings. This is the
2036 the default.
2037 off: Turn ECRC off
2038 on: Turn ECRC on.
2040 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2041 Management.
2042 off Disable ASPM.
2043 force Enable ASPM even on devices that claim not to support it.
2044 WARNING: Forcing ASPM on may cause system lockups.
2046 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2047 off Do not use native PCIe PME signaling.
2048 force Use native PCIe PME signaling even if the BIOS refuses
2049 to allow the kernel to control the relevant PCIe config
2050 registers.
2051 nomsi Do not use MSI for native PCIe PME signaling (this makes
2052 all PCIe root ports use INTx for everything).
2054 pcmv= [HW,PCMCIA] BadgePAD 4
2056 pd. [PARIDE]
2057 See Documentation/blockdev/paride.txt.
2059 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2060 boot time.
2061 Format: { 0 | 1 }
2062 See arch/parisc/kernel/pdc_chassis.c
2064 percpu_alloc= Select which percpu first chunk allocator to use.
2065 Currently supported values are "embed" and "page".
2066 Archs may support subset or none of the selections.
2067 See comments in mm/percpu.c for details on each
2068 allocator. This parameter is primarily for debugging
2069 and performance comparison.
2071 pf. [PARIDE]
2072 See Documentation/blockdev/paride.txt.
2074 pg. [PARIDE]
2075 See Documentation/blockdev/paride.txt.
2077 pirq= [SMP,APIC] Manual mp-table setup
2078 See Documentation/x86/i386/IO-APIC.txt.
2080 plip= [PPT,NET] Parallel port network link
2081 Format: { parport<nr> | timid | 0 }
2082 See also Documentation/parport.txt.
2084 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2085 Override pmtimer IOPort with a hex value.
2086 e.g. pmtmr=0x508
2088 pnp.debug [PNP]
2089 Enable PNP debug messages. This depends on the
2090 CONFIG_PNP_DEBUG_MESSAGES option.
2092 pnpacpi= [ACPI]
2093 { off }
2095 pnpbios= [ISAPNP]
2096 { on | off | curr | res | no-curr | no-res }
2098 pnp_reserve_irq=
2099 [ISAPNP] Exclude IRQs for the autoconfiguration
2101 pnp_reserve_dma=
2102 [ISAPNP] Exclude DMAs for the autoconfiguration
2104 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2105 Ranges are in pairs (I/O port base and size).
2107 pnp_reserve_mem=
2108 [ISAPNP] Exclude memory regions for the
2109 autoconfiguration.
2110 Ranges are in pairs (memory base and size).
2112 ports= [IP_VS_FTP] IPVS ftp helper module
2113 Default is 21.
2114 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2115 may be specified.
2116 Format: <port>,<port>....
2118 print-fatal-signals=
2119 [KNL] debug: print fatal signals
2121 If enabled, warn about various signal handling
2122 related application anomalies: too many signals,
2123 too many POSIX.1 timers, fatal signals causing a
2124 coredump - etc.
2126 If you hit the warning due to signal overflow,
2127 you might want to try "ulimit -i unlimited".
2129 default: off.
2131 printk.time= Show timing data prefixed to each printk message line
2132 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2134 processor.max_cstate= [HW,ACPI]
2135 Limit processor to maximum C-state
2136 max_cstate=9 overrides any DMI blacklist limit.
2138 processor.nocst [HW,ACPI]
2139 Ignore the _CST method to determine C-states,
2140 instead using the legacy FADT method
2142 profile= [KNL] Enable kernel profiling via /proc/profile
2143 Format: [schedule,]<number>
2144 Param: "schedule" - profile schedule points.
2145 Param: <number> - step/bucket size as a power of 2 for
2146 statistical time based profiling.
2147 Param: "sleep" - profile D-state sleeping (millisecs).
2148 Requires CONFIG_SCHEDSTATS
2149 Param: "kvm" - profile VM exits.
2151 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2152 before loading.
2153 See Documentation/blockdev/ramdisk.txt.
2155 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2156 probe for; one of (bare|imps|exps|lifebook|any).
2157 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2158 per second.
2159 psmouse.resetafter= [HW,MOUSE]
2160 Try to reset the device after so many bad packets
2161 (0 = never).
2162 psmouse.resolution=
2163 [HW,MOUSE] Set desired mouse resolution, in dpi.
2164 psmouse.smartscroll=
2165 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2166 0 = disabled, 1 = enabled (default).
2168 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2169 Format:
2170 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2172 pt. [PARIDE]
2173 See Documentation/blockdev/paride.txt.
2175 pty.legacy_count=
2176 [KNL] Number of legacy pty's. Overwrites compiled-in
2177 default number.
2179 quiet [KNL] Disable most log messages
2181 r128= [HW,DRM]
2183 raid= [HW,RAID]
2184 See Documentation/md.txt.
2186 ramdisk_blocksize= [RAM]
2187 See Documentation/blockdev/ramdisk.txt.
2189 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2190 See Documentation/blockdev/ramdisk.txt.
2192 rcupdate.blimit= [KNL,BOOT]
2193 Set maximum number of finished RCU callbacks to process
2194 in one batch.
2196 rcupdate.qhimark= [KNL,BOOT]
2197 Set threshold of queued
2198 RCU callbacks over which batch limiting is disabled.
2200 rcupdate.qlowmark= [KNL,BOOT]
2201 Set threshold of queued RCU callbacks below which
2202 batch limiting is re-enabled.
2204 rdinit= [KNL]
2205 Format: <full_path>
2206 Run specified binary instead of /init from the ramdisk,
2207 used for early userspace startup. See initrd.
2209 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2210 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2211 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2213 relax_domain_level=
2214 [KNL, SMP] Set scheduler's default relax_domain_level.
2215 See Documentation/cgroups/cpusets.txt.
2217 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2219 reservetop= [X86-32]
2220 Format: nn[KMG]
2221 Reserves a hole at the top of the kernel virtual
2222 address space.
2224 reset_devices [KNL] Force drivers to reset the underlying device
2225 during initialization.
2227 resume= [SWSUSP]
2228 Specify the partition device for software suspend
2230 resume_offset= [SWSUSP]
2231 Specify the offset from the beginning of the partition
2232 given by "resume=" at which the swap header is located,
2233 in <PAGE_SIZE> units (needed only for swap files).
2234 See Documentation/power/swsusp-and-swap-files.txt
2236 retain_initrd [RAM] Keep initrd memory after extraction
2238 rhash_entries= [KNL,NET]
2239 Set number of hash buckets for route cache
2241 riscom8= [HW,SERIAL]
2242 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2244 ro [KNL] Mount root device read-only on boot
2246 root= [KNL] Root filesystem
2248 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2249 mount the root filesystem
2251 rootflags= [KNL] Set root filesystem mount option string
2253 rootfstype= [KNL] Set root filesystem type
2255 rootwait [KNL] Wait (indefinitely) for root device to show up.
2256 Useful for devices that are detected asynchronously
2257 (e.g. USB and MMC devices).
2259 rw [KNL] Mount root device read-write on boot
2261 S [KNL] Run init in single mode
2263 sa1100ir [NET]
2264 See drivers/net/irda/sa1100_ir.c.
2266 sbni= [NET] Granch SBNI12 leased line adapter
2268 sched_debug [KNL] Enables verbose scheduler debug messages.
2270 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2271 Format: <io>[,<timeout>[,<isapnp>]]
2273 scsi_debug_*= [SCSI]
2274 See drivers/scsi/scsi_debug.c.
2276 scsi_default_dev_flags=
2277 [SCSI] SCSI default device flags
2278 Format: <integer>
2280 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2281 Format: <vendor>:<model>:<flags>
2282 (flags are integer value)
2284 scsi_logging_level= [SCSI] a bit mask of logging levels
2285 See drivers/scsi/scsi_logging.h for bits. Also
2286 settable via sysctl at dev.scsi.logging_level
2287 (/proc/sys/dev/scsi/logging_level).
2288 There is also a nice 'scsi_logging_level' script in the
2289 S390-tools package, available for download at
2290 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2292 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2293 discovered. async scans them in kernel threads,
2294 allowing boot to proceed. none ignores them, expecting
2295 user space to do the scan.
2297 security= [SECURITY] Choose a security module to enable at boot.
2298 If this boot parameter is not specified, only the first
2299 security module asking for security registration will be
2300 loaded. An invalid security module name will be treated
2301 as if no module has been chosen.
2303 selinux= [SELINUX] Disable or enable SELinux at boot time.
2304 Format: { "0" | "1" }
2305 See security/selinux/Kconfig help text.
2306 0 -- disable.
2307 1 -- enable.
2308 Default value is set via kernel config option.
2309 If enabled at boot time, /selinux/disable can be used
2310 later to disable prior to initial policy load.
2312 serialnumber [BUGS=X86-32]
2314 shapers= [NET]
2315 Maximal number of shapers.
2317 show_msr= [x86] show boot-time MSR settings
2318 Format: { <integer> }
2319 Show boot-time (BIOS-initialized) MSR settings.
2320 The parameter means the number of CPUs to show,
2321 for example 1 means boot CPU only.
2323 sim710= [SCSI,HW]
2324 See header of drivers/scsi/sim710.c.
2326 simeth= [IA-64]
2327 simscsi=
2329 slram= [HW,MTD]
2331 slub_debug[=options[,slabs]] [MM, SLUB]
2332 Enabling slub_debug allows one to determine the
2333 culprit if slab objects become corrupted. Enabling
2334 slub_debug can create guard zones around objects and
2335 may poison objects when not in use. Also tracks the
2336 last alloc / free. For more information see
2337 Documentation/vm/slub.txt.
2339 slub_max_order= [MM, SLUB]
2340 Determines the maximum allowed order for slabs.
2341 A high setting may cause OOMs due to memory
2342 fragmentation. For more information see
2343 Documentation/vm/slub.txt.
2345 slub_min_objects= [MM, SLUB]
2346 The minimum number of objects per slab. SLUB will
2347 increase the slab order up to slub_max_order to
2348 generate a sufficiently large slab able to contain
2349 the number of objects indicated. The higher the number
2350 of objects the smaller the overhead of tracking slabs
2351 and the less frequently locks need to be acquired.
2352 For more information see Documentation/vm/slub.txt.
2354 slub_min_order= [MM, SLUB]
2355 Determines the mininum page order for slabs. Must be
2356 lower than slub_max_order.
2357 For more information see Documentation/vm/slub.txt.
2359 slub_nomerge [MM, SLUB]
2360 Disable merging of slabs with similar size. May be
2361 necessary if there is some reason to distinguish
2362 allocs to different slabs. Debug options disable
2363 merging on their own.
2364 For more information see Documentation/vm/slub.txt.
2366 smart2= [HW]
2367 Format: <io1>[,<io2>[,...,<io8>]]
2369 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2370 attempt to substitute SMP alternatives once at boot.
2372 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2373 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2374 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2375 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2376 smsc-ircc2.ircc_irq= [HW] IRQ line
2377 smsc-ircc2.ircc_dma= [HW] DMA channel
2378 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2379 0: Toshiba Satellite 1800 (GP data pin select)
2380 1: Fast pin select (default)
2381 2: ATC IRMode
2383 snd-ad1816a= [HW,ALSA]
2385 snd-ad1848= [HW,ALSA]
2387 snd-ali5451= [HW,ALSA]
2389 snd-als100= [HW,ALSA]
2391 snd-als4000= [HW,ALSA]
2393 snd-azt2320= [HW,ALSA]
2395 snd-cmi8330= [HW,ALSA]
2397 snd-cmipci= [HW,ALSA]
2399 snd-cs4231= [HW,ALSA]
2401 snd-cs4232= [HW,ALSA]
2403 snd-cs4236= [HW,ALSA]
2405 snd-cs4281= [HW,ALSA]
2407 snd-cs46xx= [HW,ALSA]
2409 snd-dt019x= [HW,ALSA]
2411 snd-dummy= [HW,ALSA]
2413 snd-emu10k1= [HW,ALSA]
2415 snd-ens1370= [HW,ALSA]
2417 snd-ens1371= [HW,ALSA]
2419 snd-es968= [HW,ALSA]
2421 snd-es1688= [HW,ALSA]
2423 snd-es18xx= [HW,ALSA]
2425 snd-es1938= [HW,ALSA]
2427 snd-es1968= [HW,ALSA]
2429 snd-fm801= [HW,ALSA]
2431 snd-gusclassic= [HW,ALSA]
2433 snd-gusextreme= [HW,ALSA]
2435 snd-gusmax= [HW,ALSA]
2437 snd-hdsp= [HW,ALSA]
2439 snd-ice1712= [HW,ALSA]
2441 snd-intel8x0= [HW,ALSA]
2443 snd-interwave= [HW,ALSA]
2445 snd-interwave-stb=
2446 [HW,ALSA]
2448 snd-korg1212= [HW,ALSA]
2450 snd-maestro3= [HW,ALSA]
2452 snd-mpu401= [HW,ALSA]
2454 snd-mtpav= [HW,ALSA]
2456 snd-nm256= [HW,ALSA]
2458 snd-opl3sa2= [HW,ALSA]
2460 snd-opti92x-ad1848=
2461 [HW,ALSA]
2463 snd-opti92x-cs4231=
2464 [HW,ALSA]
2466 snd-opti93x= [HW,ALSA]
2468 snd-pmac= [HW,ALSA]
2470 snd-rme32= [HW,ALSA]
2472 snd-rme96= [HW,ALSA]
2474 snd-rme9652= [HW,ALSA]
2476 snd-sb8= [HW,ALSA]
2478 snd-sb16= [HW,ALSA]
2480 snd-sbawe= [HW,ALSA]
2482 snd-serial= [HW,ALSA]
2484 snd-sgalaxy= [HW,ALSA]
2486 snd-sonicvibes= [HW,ALSA]
2488 snd-sun-amd7930=
2489 [HW,ALSA]
2491 snd-sun-cs4231= [HW,ALSA]
2493 snd-trident= [HW,ALSA]
2495 snd-usb-audio= [HW,ALSA,USB]
2497 snd-via82xx= [HW,ALSA]
2499 snd-virmidi= [HW,ALSA]
2501 snd-wavefront= [HW,ALSA]
2503 snd-ymfpci= [HW,ALSA]
2505 softlockup_panic=
2506 [KNL] Should the soft-lockup detector generate panics.
2508 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2509 See Documentation/sonypi.txt
2511 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2512 See Documentation/serial/specialix.txt.
2514 spia_io_base= [HW,MTD]
2515 spia_fio_base=
2516 spia_pedr=
2517 spia_peddr=
2519 sscape= [HW,OSS]
2520 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2522 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2523 See Documentation/scsi/st.txt.
2525 stacktrace [FTRACE]
2526 Enabled the stack tracer on boot up.
2528 sti= [PARISC,HW]
2529 Format: <num>
2530 Set the STI (builtin display/keyboard on the HP-PARISC
2531 machines) console (graphic card) which should be used
2532 as the initial boot-console.
2533 See also comment in drivers/video/console/sticore.c.
2535 sti_font= [HW]
2536 See comment in drivers/video/console/sticore.c.
2538 stifb= [HW]
2539 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2541 sunrpc.min_resvport=
2542 sunrpc.max_resvport=
2543 [NFS,SUNRPC]
2544 SunRPC servers often require that client requests
2545 originate from a privileged port (i.e. a port in the
2546 range 0 < portnr < 1024).
2547 An administrator who wishes to reserve some of these
2548 ports for other uses may adjust the range that the
2549 kernel's sunrpc client considers to be privileged
2550 using these two parameters to set the minimum and
2551 maximum port values.
2553 sunrpc.pool_mode=
2554 [NFS]
2555 Control how the NFS server code allocates CPUs to
2556 service thread pools. Depending on how many NICs
2557 you have and where their interrupts are bound, this
2558 option will affect which CPUs will do NFS serving.
2559 Note: this parameter cannot be changed while the
2560 NFS server is running.
2562 auto the server chooses an appropriate mode
2563 automatically using heuristics
2564 global a single global pool contains all CPUs
2565 percpu one pool for each CPU
2566 pernode one pool for each NUMA node (equivalent
2567 to global on non-NUMA machines)
2569 sunrpc.tcp_slot_table_entries=
2570 sunrpc.udp_slot_table_entries=
2571 [NFS,SUNRPC]
2572 Sets the upper limit on the number of simultaneous
2573 RPC calls that can be sent from the client to a
2574 server. Increasing these values may allow you to
2575 improve throughput, but will also increase the
2576 amount of memory reserved for use by the client.
2578 swiotlb= [IA-64] Number of I/O TLB slabs
2580 switches= [HW,M68k]
2582 sym53c416= [HW,SCSI]
2583 See header of drivers/scsi/sym53c416.c.
2585 sysrq_always_enabled
2586 [KNL]
2587 Ignore sysrq setting - this boot parameter will
2588 neutralize any effect of /proc/sys/kernel/sysrq.
2589 Useful for debugging.
2591 t128= [HW,SCSI]
2592 See header of drivers/scsi/t128.c.
2594 tdfx= [HW,DRM]
2596 test_suspend= [SUSPEND]
2597 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2598 standby suspend) as the system sleep state to briefly
2599 enter during system startup. The system is woken from
2600 this state using a wakeup-capable RTC alarm.
2602 thash_entries= [KNL,NET]
2603 Set number of hash buckets for TCP connection
2605 thermal.act= [HW,ACPI]
2606 -1: disable all active trip points in all thermal zones
2607 <degrees C>: override all lowest active trip points
2609 thermal.crt= [HW,ACPI]
2610 -1: disable all critical trip points in all thermal zones
2611 <degrees C>: override all critical trip points
2613 thermal.nocrt= [HW,ACPI]
2614 Set to disable actions on ACPI thermal zone
2615 critical and hot trip points.
2617 thermal.off= [HW,ACPI]
2618 1: disable ACPI thermal control
2620 thermal.psv= [HW,ACPI]
2621 -1: disable all passive trip points
2622 <degrees C>: override all passive trip points to this
2623 value
2625 thermal.tzp= [HW,ACPI]
2626 Specify global default ACPI thermal zone polling rate
2627 <deci-seconds>: poll all this frequency
2628 0: no polling (default)
2630 tmscsim= [HW,SCSI]
2631 See comment before function dc390_setup() in
2632 drivers/scsi/tmscsim.c.
2634 topology= [S390]
2635 Format: {off | on}
2636 Specify if the kernel should make use of the cpu
2637 topology informations if the hardware supports these.
2638 The scheduler will make use of these informations and
2639 e.g. base its process migration decisions on it.
2640 Default is off.
2642 tp720= [HW,PS2]
2644 tpm_suspend_pcr=[HW,TPM]
2645 Format: integer pcr id
2646 Specify that at suspend time, the tpm driver
2647 should extend the specified pcr with zeros,
2648 as a workaround for some chips which fail to
2649 flush the last written pcr on TPM_SaveState.
2650 This will guarantee that all the other pcrs
2651 are saved.
2653 trace_buf_size=nn[KMG]
2654 [FTRACE] will set tracing buffer size.
2656 trace_event=[event-list]
2657 [FTRACE] Set and start specified trace events in order
2658 to facilitate early boot debugging.
2659 See also Documentation/trace/events.txt
2661 trix= [HW,OSS] MediaTrix AudioTrix Pro
2662 Format:
2663 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2665 tsc= Disable clocksource-must-verify flag for TSC.
2666 Format: <string>
2667 [x86] reliable: mark tsc clocksource as reliable, this
2668 disables clocksource verification at runtime.
2669 Used to enable high-resolution timer mode on older
2670 hardware, and in virtualized environment.
2672 turbografx.map[2|3]= [HW,JOY]
2673 TurboGraFX parallel port interface
2674 Format:
2675 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2676 See also Documentation/input/joystick-parport.txt
2678 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2679 See header of drivers/scsi/u14-34f.c.
2681 uart401= [HW,OSS]
2682 Format: <io>,<irq>
2684 uart6850= [HW,OSS]
2685 Format: <io>,<irq>
2687 uhash_entries= [KNL,NET]
2688 Set number of hash buckets for UDP/UDP-Lite connections
2690 uhci-hcd.ignore_oc=
2691 [USB] Ignore overcurrent events (default N).
2692 Some badly-designed motherboards generate lots of
2693 bogus events, for ports that aren't wired to
2694 anything. Set this parameter to avoid log spamming.
2695 Note that genuine overcurrent events won't be
2696 reported either.
2698 unknown_nmi_panic
2699 [X86]
2700 Set unknown_nmi_panic=1 early on boot.
2702 usbcore.autosuspend=
2703 [USB] The autosuspend time delay (in seconds) used
2704 for newly-detected USB devices (default 2). This
2705 is the time required before an idle device will be
2706 autosuspended. Devices for which the delay is set
2707 to a negative value won't be autosuspended at all.
2709 usbcore.usbfs_snoop=
2710 [USB] Set to log all usbfs traffic (default 0 = off).
2712 usbcore.blinkenlights=
2713 [USB] Set to cycle leds on hubs (default 0 = off).
2715 usbcore.old_scheme_first=
2716 [USB] Start with the old device initialization
2717 scheme (default 0 = off).
2719 usbcore.use_both_schemes=
2720 [USB] Try the other device initialization scheme
2721 if the first one fails (default 1 = enabled).
2723 usbcore.initial_descriptor_timeout=
2724 [USB] Specifies timeout for the initial 64-byte
2725 USB_REQ_GET_DESCRIPTOR request in milliseconds
2726 (default 5000 = 5.0 seconds).
2728 usbhid.mousepoll=
2729 [USBHID] The interval which mice are to be polled at.
2731 usb-storage.delay_use=
2732 [UMS] The delay in seconds before a new device is
2733 scanned for Logical Units (default 5).
2735 usb-storage.quirks=
2736 [UMS] A list of quirks entries to supplement or
2737 override the built-in unusual_devs list. List
2738 entries are separated by commas. Each entry has
2739 the form VID:PID:Flags where VID and PID are Vendor
2740 and Product ID values (4-digit hex numbers) and
2741 Flags is a set of characters, each corresponding
2742 to a common usb-storage quirk flag as follows:
2743 a = SANE_SENSE (collect more than 18 bytes
2744 of sense data);
2745 b = BAD_SENSE (don't collect more than 18
2746 bytes of sense data);
2747 c = FIX_CAPACITY (decrease the reported
2748 device capacity by one sector);
2749 h = CAPACITY_HEURISTICS (decrease the
2750 reported device capacity by one
2751 sector if the number is odd);
2752 i = IGNORE_DEVICE (don't bind to this
2753 device);
2754 l = NOT_LOCKABLE (don't try to lock and
2755 unlock ejectable media);
2756 m = MAX_SECTORS_64 (don't transfer more
2757 than 64 sectors = 32 KB at a time);
2758 o = CAPACITY_OK (accept the capacity
2759 reported by the device);
2760 r = IGNORE_RESIDUE (the device reports
2761 bogus residue values);
2762 s = SINGLE_LUN (the device has only one
2763 Logical Unit);
2764 w = NO_WP_DETECT (don't test whether the
2765 medium is write-protected).
2766 Example: quirks=0419:aaf5:rl,0421:0433:rc
2768 userpte=
2769 [X86] Flags controlling user PTE allocations.
2771 nohigh = do not allocate PTE pages in
2772 HIGHMEM regardless of setting
2773 of CONFIG_HIGHPTE.
2775 vdso= [X86,SH]
2776 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2777 vdso=1: enable VDSO (default)
2778 vdso=0: disable VDSO mapping
2780 vdso32= [X86]
2781 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2782 vdso32=1: enable 32-bit VDSO (default)
2783 vdso32=0: disable 32-bit VDSO mapping
2785 vector= [IA-64,SMP]
2786 vector=percpu: enable percpu vector domain
2788 video= [FB] Frame buffer configuration
2789 See Documentation/fb/modedb.txt.
2791 vga= [BOOT,X86-32] Select a particular video mode
2792 See Documentation/x86/boot.txt and
2793 Documentation/svga.txt.
2794 Use vga=ask for menu.
2795 This is actually a boot loader parameter; the value is
2796 passed to the kernel using a special protocol.
2798 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2799 size of <nn>. This can be used to increase the
2800 minimum size (128MB on x86). It can also be used to
2801 decrease the size and leave more room for directly
2802 mapped kernel RAM.
2804 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2805 Format: <command>
2807 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2808 Format: <command>
2810 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2811 Format: <command>
2813 vt.cur_default= [VT] Default cursor shape.
2814 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2815 the parameters of the <Esc>[?A;B;Cc escape sequence;
2816 see VGA-softcursor.txt. Default: 2 = underline.
2818 vt.default_blu= [VT]
2819 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2820 Change the default blue palette of the console.
2821 This is a 16-member array composed of values
2822 ranging from 0-255.
2824 vt.default_grn= [VT]
2825 Format: <green0>,<green1>,<green2>,...,<green15>
2826 Change the default green palette of the console.
2827 This is a 16-member array composed of values
2828 ranging from 0-255.
2830 vt.default_red= [VT]
2831 Format: <red0>,<red1>,<red2>,...,<red15>
2832 Change the default red palette of the console.
2833 This is a 16-member array composed of values
2834 ranging from 0-255.
2836 vt.default_utf8=
2837 [VT]
2838 Format=<0|1>
2839 Set system-wide default UTF-8 mode for all tty's.
2840 Default is 1, i.e. UTF-8 mode is enabled for all
2841 newly opened terminals.
2843 vt.global_cursor_default=
2844 [VT]
2845 Format=<-1|0|1>
2846 Set system-wide default for whether a cursor
2847 is shown on new VTs. Default is -1,
2848 i.e. cursors will be created by default unless
2849 overridden by individual drivers. 0 will hide
2850 cursors, 1 will display them.
2852 waveartist= [HW,OSS]
2853 Format: <io>,<irq>,<dma>,<dma2>
2855 wd33c93= [HW,SCSI]
2856 See header of drivers/scsi/wd33c93.c.
2858 wd7000= [HW,SCSI]
2859 See header of drivers/scsi/wd7000.c.
2861 wdt= [WDT] Watchdog
2862 See Documentation/watchdog/wdt.txt.
2864 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2865 default x2apic cluster mode on platforms
2866 supporting x2apic.
2868 x86_mrst_timer= [X86-32,APBT]
2869 Choose timer option for x86 Moorestown MID platform.
2870 Two valid options are apbt timer only and lapic timer
2871 plus one apbt timer for broadcast timer.
2872 x86_mrst_timer=apbt_only | lapic_and_apbt
2874 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2875 xd_geo= See header of drivers/block/xd.c.
2877 xirc2ps_cs= [NET,PCMCIA]
2878 Format:
2879 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2881 ______________________________________________________________________
2883 TODO:
2885 Add documentation for ALSA options.
2886 Add more DRM drivers.