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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 APPARMOR AppArmor support is enabled.
97 SERIAL Serial support is enabled.
98 SH SuperH architecture is enabled.
99 SMP The kernel is an SMP kernel.
100 SPARC Sparc architecture is enabled.
101 SWSUSP Software suspend (hibernation) is enabled.
102 SUSPEND System suspend states are enabled.
103 FTRACE Function tracing enabled.
104 TPM TPM drivers are enabled.
105 TS Appropriate touchscreen support is enabled.
106 UMS USB Mass Storage support is enabled.
107 USB USB support is enabled.
108 USBHID USB Human Interface Device support is enabled.
109 V4L Video For Linux support is enabled.
110 VGA The VGA console has been enabled.
111 VT Virtual terminal support is enabled.
112 WDT Watchdog support is enabled.
113 XT IBM PC/XT MFM hard disk support is enabled.
114 X86-32 X86-32, aka i386 architecture is enabled.
115 X86-64 X86-64 architecture is enabled.
116 More X86-64 boot options can be found in
117 Documentation/x86/x86_64/boot-options.txt .
118 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
120 In addition, the following text indicates that the option:
122 BUGS= Relates to possible processor bugs on the said processor.
123 KNL Is a kernel start-up parameter.
124 BOOT Is a boot loader parameter.
126 Parameters denoted with BOOT are actually interpreted by the boot
127 loader, and have no meaning to the kernel directly.
128 Do not modify the syntax of boot loader parameters without extreme
129 need or coordination with <Documentation/x86/boot.txt>.
131 There are also arch-specific kernel-parameters not documented here.
132 See for example <Documentation/x86/x86_64/boot-options.txt>.
134 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
135 a trailing = on the name of any parameter states that that parameter will
136 be entered as an environment variable, whereas its absence indicates that
137 it will appear as a kernel argument readable via /proc/cmdline by programs
138 running once the system is up.
140 The number of kernel parameters is not limited, but the length of the
141 complete command line (parameters including spaces etc.) is limited to
142 a fixed number of characters. This limit depends on the architecture
143 and is between 256 and 4096 characters. It is defined in the file
144 ./include/asm/setup.h as COMMAND_LINE_SIZE.
147 acpi= [HW,ACPI,X86]
148 Advanced Configuration and Power Interface
149 Format: { force | off | strict | noirq | rsdt }
150 force -- enable ACPI if default was off
151 off -- disable ACPI if default was on
152 noirq -- do not use ACPI for IRQ routing
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 nonvs prevents the kernel from saving/restoring the
259 ACPI NVS memory during suspend/hibernation and resume.
260 sci_force_enable causes the kernel to set SCI_EN directly
261 on resume from S1/S3 (which is against the ACPI spec,
262 but some broken systems don't work without it).
264 acpi_use_timer_override [HW,ACPI]
265 Use timer override. For some broken Nvidia NF5 boards
266 that require a timer override, but don't have HPET
268 acpi_enforce_resources= [ACPI]
269 { strict | lax | no }
270 Check for resource conflicts between native drivers
271 and ACPI OperationRegions (SystemIO and SystemMemory
272 only). IO ports and memory declared in ACPI might be
273 used by the ACPI subsystem in arbitrary AML code and
274 can interfere with legacy drivers.
275 strict (default): access to resources claimed by ACPI
276 is denied; legacy drivers trying to access reserved
277 resources will fail to bind to device using them.
278 lax: access to resources claimed by ACPI is allowed;
279 legacy drivers trying to access reserved resources
280 will bind successfully but a warning message is logged.
281 no: ACPI OperationRegions are not marked as reserved,
282 no further checks are performed.
284 ad1848= [HW,OSS]
285 Format: <io>,<irq>,<dma>,<dma2>,<type>
287 add_efi_memmap [EFI; X86] Include EFI memory map in
288 kernel's map of available physical RAM.
290 advansys= [HW,SCSI]
291 See header of drivers/scsi/advansys.c.
293 aedsp16= [HW,OSS] Audio Excel DSP 16
294 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
295 See also header of sound/oss/aedsp16.c.
297 agp= [AGP]
298 { off | try_unsupported }
299 off: disable AGP support
300 try_unsupported: try to drive unsupported chipsets
301 (may crash computer or cause data corruption)
303 aha152x= [HW,SCSI]
304 See Documentation/scsi/aha152x.txt.
306 aha1542= [HW,SCSI]
307 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
309 aic7xxx= [HW,SCSI]
310 See Documentation/scsi/aic7xxx.txt.
312 aic79xx= [HW,SCSI]
313 See Documentation/scsi/aic79xx.txt.
315 alignment= [KNL,ARM]
316 Allow the default userspace alignment fault handler
317 behaviour to be specified. Bit 0 enables warnings,
318 bit 1 enables fixups, and bit 2 sends a segfault.
320 amd_iommu= [HW,X86-84]
321 Pass parameters to the AMD IOMMU driver in the system.
322 Possible values are:
323 fullflush - enable flushing of IO/TLB entries when
324 they are unmapped. Otherwise they are
325 flushed before they will be reused, which
326 is a lot of faster
327 off - do not initialize any AMD IOMMU found in
328 the system
330 amijoy.map= [HW,JOY] Amiga joystick support
331 Map of devices attached to JOY0DAT and JOY1DAT
332 Format: <a>,<b>
333 See also Documentation/kernel/input/joystick.txt
335 analog.map= [HW,JOY] Analog joystick and gamepad support
336 Specifies type or capabilities of an analog joystick
337 connected to one of 16 gameports
338 Format: <type1>,<type2>,..<type16>
340 apc= [HW,SPARC]
341 Power management functions (SPARCstation-4/5 + deriv.)
342 Format: noidle
343 Disable APC CPU standby support. SPARCstation-Fox does
344 not play well with APC CPU idle - disable it if you have
345 APC and your system crashes randomly.
347 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
348 Change the output verbosity whilst booting
349 Format: { quiet (default) | verbose | debug }
350 Change the amount of debugging information output
351 when initialising the APIC and IO-APIC components.
353 autoconf= [IPV6]
354 See Documentation/networking/ipv6.txt.
356 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
357 Limit apic dumping. The parameter defines the maximal
358 number of local apics being dumped. Also it is possible
359 to set it to "all" by meaning -- no limit here.
360 Format: { 1 (default) | 2 | ... | all }.
361 The parameter valid if only apic=debug or
362 apic=verbose is specified.
363 Example: apic=debug show_lapic=all
365 apm= [APM] Advanced Power Management
366 See header of arch/x86/kernel/apm_32.c.
368 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
369 Format: <io>,<irq>,<nodeID>
371 ataflop= [HW,M68k]
373 atarimouse= [HW,MOUSE] Atari Mouse
375 atascsi= [HW,SCSI] Atari SCSI
377 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
378 EzKey and similar keyboards
380 atkbd.reset= [HW] Reset keyboard during initialization
382 atkbd.set= [HW] Select keyboard code set
383 Format: <int> (2 = AT (default), 3 = PS/2)
385 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
386 keyboards
388 atkbd.softraw= [HW] Choose between synthetic and real raw mode
389 Format: <bool> (0 = real, 1 = synthetic (default))
391 atkbd.softrepeat= [HW]
392 Use software keyboard repeat
394 autotest [IA64]
396 baycom_epp= [HW,AX25]
397 Format: <io>,<mode>
399 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
400 Format: <io>,<mode>
401 See header of drivers/net/hamradio/baycom_par.c.
403 baycom_ser_fdx= [HW,AX25]
404 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
405 Format: <io>,<irq>,<mode>[,<baud>]
406 See header of drivers/net/hamradio/baycom_ser_fdx.c.
408 baycom_ser_hdx= [HW,AX25]
409 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
410 Format: <io>,<irq>,<mode>
411 See header of drivers/net/hamradio/baycom_ser_hdx.c.
413 boot_delay= Milliseconds to delay each printk during boot.
414 Values larger than 10 seconds (10000) are changed to
415 no delay (0).
416 Format: integer
418 bootmem_debug [KNL] Enable bootmem allocator debug messages.
420 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
421 bttv.radio= Most important insmod options are available as
422 kernel args too.
423 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
424 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
426 BusLogic= [HW,SCSI]
427 See drivers/scsi/BusLogic.c, comment before function
428 BusLogic_ParseDriverOptions().
430 c101= [NET] Moxa C101 synchronous serial card
432 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
433 Sometimes CPU hardware bugs make them report the cache
434 size incorrectly. The kernel will attempt work arounds
435 to fix known problems, but for some CPUs it is not
436 possible to determine what the correct size should be.
437 This option provides an override for these situations.
439 capability.disable=
440 [SECURITY] Disable capabilities. This would normally
441 be used only if an alternative security model is to be
442 configured. Potentially dangerous and should only be
443 used if you are entirely sure of the consequences.
445 ccw_timeout_log [S390]
446 See Documentation/s390/CommonIO for details.
448 cgroup_disable= [KNL] Disable a particular controller
449 Format: {name of the controller(s) to disable}
450 {Currently supported controllers - "memory"}
452 checkreqprot [SELINUX] Set initial checkreqprot flag value.
453 Format: { "0" | "1" }
454 See security/selinux/Kconfig help text.
455 0 -- check protection applied by kernel (includes
456 any implied execute protection).
457 1 -- check protection requested by application.
458 Default value is set via a kernel config option.
459 Value can be changed at runtime via
460 /selinux/checkreqprot.
462 cio_ignore= [S390]
463 See Documentation/s390/CommonIO for details.
465 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
466 [Deprecated]
467 Forces specified clocksource (if available) to be used
468 when calculating gettimeofday(). If specified
469 clocksource is not available, it defaults to PIT.
470 Format: { pit | tsc | cyclone | pmtmr }
472 clocksource= [GENERIC_TIME] Override the default clocksource
473 Format: <string>
474 Override the default clocksource and use the clocksource
475 with the name specified.
476 Some clocksource names to choose from, depending on
477 the platform:
478 [all] jiffies (this is the base, fallback clocksource)
479 [ACPI] acpi_pm
480 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
481 pxa_timer,timer3,32k_counter,timer0_1
482 [AVR32] avr32
483 [X86-32] pit,hpet,tsc,vmi-timer;
484 scx200_hrt on Geode; cyclone on IBM x440
485 [MIPS] MIPS
486 [PARISC] cr16
487 [S390] tod
488 [SH] SuperH
489 [SPARC64] tick
490 [X86-64] hpet,tsc
492 clearcpuid=BITNUM [X86]
493 Disable CPUID feature X for the kernel. See
494 arch/x86/include/asm/cpufeature.h for the valid bit
495 numbers. Note the Linux specific bits are not necessarily
496 stable over kernel options, but the vendor specific
497 ones should be.
498 Also note that user programs calling CPUID directly
499 or using the feature without checking anything
500 will still see it. This just prevents it from
501 being used by the kernel or shown in /proc/cpuinfo.
502 Also note the kernel might malfunction if you disable
503 some critical bits.
505 cmo_free_hint= [PPC] Format: { yes | no }
506 Specify whether pages are marked as being inactive
507 when they are freed. This is used in CMO environments
508 to determine OS memory pressure for page stealing by
509 a hypervisor.
510 Default: yes
512 code_bytes [X86] How many bytes of object code to print
513 in an oops report.
514 Range: 0 - 8192
515 Default: 64
517 com20020= [HW,NET] ARCnet - COM20020 chipset
518 Format:
519 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
521 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
522 Format: <io>[,<irq>]
524 com90xx= [HW,NET]
525 ARCnet - COM90xx chipset (memory-mapped buffers)
526 Format: <io>[,<irq>[,<memstart>]]
528 condev= [HW,S390] console device
529 conmode=
531 console= [KNL] Output console device and options.
533 tty<n> Use the virtual console device <n>.
535 ttyS<n>[,options]
536 ttyUSB0[,options]
537 Use the specified serial port. The options are of
538 the form "bbbbpnf", where "bbbb" is the baud rate,
539 "p" is parity ("n", "o", or "e"), "n" is number of
540 bits, and "f" is flow control ("r" for RTS or
541 omit it). Default is "9600n8".
543 See Documentation/serial-console.txt for more
544 information. See
545 Documentation/networking/netconsole.txt for an
546 alternative.
548 uart[8250],io,<addr>[,options]
549 uart[8250],mmio,<addr>[,options]
550 Start an early, polled-mode console on the 8250/16550
551 UART at the specified I/O port or MMIO address,
552 switching to the matching ttyS device later. The
553 options are the same as for ttyS, above.
555 If the device connected to the port is not a TTY but a braille
556 device, prepend "brl," before the device type, for instance
557 console=brl,ttyS0
558 For now, only VisioBraille is supported.
560 consoleblank= [KNL] The console blank (screen saver) timeout in
561 seconds. Defaults to 10*60 = 10mins. A value of 0
562 disables the blank timer.
564 coredump_filter=
565 [KNL] Change the default value for
566 /proc/<pid>/coredump_filter.
567 See also Documentation/filesystems/proc.txt.
569 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
570 Format:
571 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
573 crashkernel=nn[KMG]@ss[KMG]
574 [KNL] Reserve a chunk of physical memory to
575 hold a kernel to switch to with kexec on panic.
577 crashkernel=range1:size1[,range2:size2,...][@offset]
578 [KNL] Same as above, but depends on the memory
579 in the running system. The syntax of range is
580 start-[end] where start and end are both
581 a memory unit (amount[KMG]). See also
582 Documentation/kdump/kdump.txt for a example.
584 cs89x0_dma= [HW,NET]
585 Format: <dma>
587 cs89x0_media= [HW,NET]
588 Format: { rj45 | aui | bnc }
590 dasd= [HW,NET]
591 See header of drivers/s390/block/dasd_devmap.c.
593 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
594 (one device per port)
595 Format: <port#>,<type>
596 See also Documentation/input/joystick-parport.txt
598 debug [KNL] Enable kernel debugging (events log level).
600 debug_locks_verbose=
601 [KNL] verbose self-tests
602 Format=<0|1>
603 Print debugging info while doing the locking API
604 self-tests.
605 We default to 0 (no extra messages), setting it to
606 1 will print _a lot_ more information - normally
607 only useful to kernel developers.
609 debug_objects [KNL] Enable object debugging
611 no_debug_objects
612 [KNL] Disable object debugging
614 debugpat [X86] Enable PAT debugging
616 decnet.addr= [HW,NET]
617 Format: <area>[,<node>]
618 See also Documentation/networking/decnet.txt.
620 default_hugepagesz=
621 [same as hugepagesz=] The size of the default
622 HugeTLB page size. This is the size represented by
623 the legacy /proc/ hugepages APIs, used for SHM, and
624 default size when mounting hugetlbfs filesystems.
625 Defaults to the default architecture's huge page size
626 if not specified.
628 dhash_entries= [KNL]
629 Set number of hash buckets for dentry cache.
631 digi= [HW,SERIAL]
632 IO parameters + enable/disable command.
634 digiepca= [HW,SERIAL]
635 See drivers/char/README.epca and
636 Documentation/serial/digiepca.txt.
638 disable= [IPV6]
639 See Documentation/networking/ipv6.txt.
641 disable_ipv6= [IPV6]
642 See Documentation/networking/ipv6.txt.
644 disable_mtrr_cleanup [X86]
645 The kernel tries to adjust MTRR layout from continuous
646 to discrete, to make X server driver able to add WB
647 entry later. This parameter disables that.
649 disable_mtrr_trim [X86, Intel and AMD only]
650 By default the kernel will trim any uncacheable
651 memory out of your available memory pool based on
652 MTRR settings. This parameter disables that behavior,
653 possibly causing your machine to run very slowly.
655 disable_timer_pin_1 [X86]
656 Disable PIN 1 of APIC timer
657 Can be useful to work around chipset bugs.
659 dmasound= [HW,OSS] Sound subsystem buffers
661 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
662 this option disables the debugging code at boot.
664 dma_debug_entries=<number>
665 This option allows to tune the number of preallocated
666 entries for DMA-API debugging code. One entry is
667 required per DMA-API allocation. Use this if the
668 DMA-API debugging code disables itself because the
669 architectural default is too low.
671 dma_debug_driver=<driver_name>
672 With this option the DMA-API debugging driver
673 filter feature can be enabled at boot time. Just
674 pass the driver to filter for as the parameter.
675 The filter can be disabled or changed to another
676 driver later using sysfs.
678 dscc4.setup= [NET]
680 dtc3181e= [HW,SCSI]
682 dynamic_printk Enables pr_debug()/dev_dbg() calls if
683 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
684 These can also be switched on/off via
685 <debugfs>/dynamic_printk/modules
687 earlycon= [KNL] Output early console device and options.
688 uart[8250],io,<addr>[,options]
689 uart[8250],mmio,<addr>[,options]
690 Start an early, polled-mode console on the 8250/16550
691 UART at the specified I/O port or MMIO address.
692 The options are the same as for ttyS, above.
694 earlyprintk= [X86,SH,BLACKFIN]
695 earlyprintk=vga
696 earlyprintk=serial[,ttySn[,baudrate]]
697 earlyprintk=ttySn[,baudrate]
698 earlyprintk=dbgp[debugController#]
700 Append ",keep" to not disable it when the real console
701 takes over.
703 Only vga or serial or usb debug port at a time.
705 Currently only ttyS0 and ttyS1 are supported.
707 Interaction with the standard serial driver is not
708 very good.
710 The VGA output is eventually overwritten by the real
711 console.
713 ekgdboc= [X86,KGDB] Allow early kernel console debugging
714 ekgdboc=kbd
716 This is desgined to be used in conjunction with
717 the boot argument: earlyprintk=vga
719 eata= [HW,SCSI]
721 edd= [EDD]
722 Format: {"off" | "on" | "skip[mbr]"}
724 eisa_irq_edge= [PARISC,HW]
725 See header of drivers/parisc/eisa.c.
727 elanfreq= [X86-32]
728 See comment before function elanfreq_setup() in
729 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
731 elevator= [IOSCHED]
732 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
733 See Documentation/block/as-iosched.txt and
734 Documentation/block/deadline-iosched.txt for details.
736 elfcorehdr= [IA64,PPC,SH,X86]
737 Specifies physical address of start of kernel core
738 image elf header. Generally kexec loader will
739 pass this option to capture kernel.
740 See Documentation/kdump/kdump.txt for details.
742 enable_mtrr_cleanup [X86]
743 The kernel tries to adjust MTRR layout from continuous
744 to discrete, to make X server driver able to add WB
745 entry later. This parameter enables that.
747 enable_timer_pin_1 [X86]
748 Enable PIN 1 of APIC timer
749 Can be useful to work around chipset bugs
750 (in particular on some ATI chipsets).
751 The kernel tries to set a reasonable default.
753 enforcing [SELINUX] Set initial enforcing status.
754 Format: {"0" | "1"}
755 See security/selinux/Kconfig help text.
756 0 -- permissive (log only, no denials).
757 1 -- enforcing (deny and log).
758 Default value is 0.
759 Value can be changed at runtime via /selinux/enforce.
761 erst_disable [ACPI]
762 Disable Error Record Serialization Table (ERST)
763 support.
765 ether= [HW,NET] Ethernet cards parameters
766 This option is obsoleted by the "netdev=" option, which
767 has equivalent usage. See its documentation for details.
769 failslab=
770 fail_page_alloc=
771 fail_make_request=[KNL]
772 General fault injection mechanism.
773 Format: <interval>,<probability>,<space>,<times>
774 See also /Documentation/fault-injection/.
776 fd_mcs= [HW,SCSI]
777 See header of drivers/scsi/fd_mcs.c.
779 fdomain= [HW,SCSI]
780 See header of drivers/scsi/fdomain.c.
782 floppy= [HW]
783 See Documentation/blockdev/floppy.txt.
785 force_pal_cache_flush
786 [IA-64] Avoid check_sal_cache_flush which may hang on
787 buggy SAL_CACHE_FLUSH implementations. Using this
788 parameter will force ia64_sal_cache_flush to call
789 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
791 ftrace=[tracer]
792 [FTRACE] will set and start the specified tracer
793 as early as possible in order to facilitate early
794 boot debugging.
796 ftrace_dump_on_oops[=orig_cpu]
797 [FTRACE] will dump the trace buffers on oops.
798 If no parameter is passed, ftrace will dump
799 buffers of all CPUs, but if you pass orig_cpu, it will
800 dump only the buffer of the CPU that triggered the
801 oops.
803 ftrace_filter=[function-list]
804 [FTRACE] Limit the functions traced by the function
805 tracer at boot up. function-list is a comma separated
806 list of functions. This list can be changed at run
807 time by the set_ftrace_filter file in the debugfs
808 tracing directory.
810 ftrace_notrace=[function-list]
811 [FTRACE] Do not trace the functions specified in
812 function-list. This list can be changed at run time
813 by the set_ftrace_notrace file in the debugfs
814 tracing directory.
816 ftrace_graph_filter=[function-list]
817 [FTRACE] Limit the top level callers functions traced
818 by the function graph tracer at boot up.
819 function-list is a comma separated list of functions
820 that can be changed at run time by the
821 set_graph_function file in the debugfs tracing directory.
823 gamecon.map[2|3]=
824 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
825 support via parallel port (up to 5 devices per port)
826 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
827 See also Documentation/input/joystick-parport.txt
829 gamma= [HW,DRM]
831 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
832 Format: off | on
833 default: on
835 gcov_persist= [GCOV] When non-zero (default), profiling data for
836 kernel modules is saved and remains accessible via
837 debugfs, even when the module is unloaded/reloaded.
838 When zero, profiling data is discarded and associated
839 debugfs files are removed at module unload time.
841 gdth= [HW,SCSI]
842 See header of drivers/scsi/gdth.c.
844 gpt [EFI] Forces disk with valid GPT signature but
845 invalid Protective MBR to be treated as GPT.
847 gvp11= [HW,SCSI]
849 hashdist= [KNL,NUMA] Large hashes allocated during boot
850 are distributed across NUMA nodes. Defaults on
851 for 64bit NUMA, off otherwise.
852 Format: 0 | 1 (for off | on)
854 hcl= [IA-64] SGI's Hardware Graph compatibility layer
856 hd= [EIDE] (E)IDE hard drive subsystem geometry
857 Format: <cyl>,<head>,<sect>
859 hest_disable [ACPI]
860 Disable Hardware Error Source Table (HEST) support;
861 corresponding firmware-first mode error processing
862 logic will be disabled.
864 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
865 size of <nn>. This works even on boxes that have no
866 highmem otherwise. This also works to reduce highmem
867 size on bigger boxes.
869 highres= [KNL] Enable/disable high resolution timer mode.
870 Valid parameters: "on", "off"
871 Default: "on"
873 hisax= [HW,ISDN]
874 See Documentation/isdn/README.HiSax.
876 hlt [BUGS=ARM,SH]
878 hpet= [X86-32,HPET] option to control HPET usage
879 Format: { enable (default) | disable | force |
880 verbose }
881 disable: disable HPET and use PIT instead
882 force: allow force enabled of undocumented chips (ICH4,
883 VIA, nVidia)
884 verbose: show contents of HPET registers during setup
886 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
887 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
888 On x86-64 and powerpc, this option can be specified
889 multiple times interleaved with hugepages= to reserve
890 huge pages of different sizes. Valid pages sizes on
891 x86-64 are 2M (when the CPU supports "pse") and 1G
892 (when the CPU supports the "pdpe1gb" cpuinfo flag)
893 Note that 1GB pages can only be allocated at boot time
894 using hugepages= and not freed afterwards.
896 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
897 terminal devices. Valid values: 0..8
898 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
899 If specified, z/VM IUCV HVC accepts connections
900 from listed z/VM user IDs only.
902 i2c_bus= [HW] Override the default board specific I2C bus speed
903 or register an additional I2C bus that is not
904 registered from board initialization code.
905 Format:
906 <bus_id>,<clkrate>
908 i8042.debug [HW] Toggle i8042 debug mode
909 i8042.direct [HW] Put keyboard port into non-translated mode
910 i8042.dumbkbd [HW] Pretend that controller can only read data from
911 keyboard and cannot control its state
912 (Don't attempt to blink the leds)
913 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
914 i8042.nokbd [HW] Don't check/create keyboard port
915 i8042.noloop [HW] Disable the AUX Loopback command while probing
916 for the AUX port
917 i8042.nomux [HW] Don't check presence of an active multiplexing
918 controller
919 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
920 controllers
921 i8042.panicblink=
922 [HW] Frequency with which keyboard LEDs should blink
923 when kernel panics (default is 0.5 sec)
924 i8042.reset [HW] Reset the controller during init and cleanup
925 i8042.unlock [HW] Unlock (ignore) the keylock
927 i810= [HW,DRM]
929 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
930 indicates that the driver is running on unsupported
931 hardware.
932 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
933 does not match list of supported models.
934 i8k.power_status
935 [HW] Report power status in /proc/i8k
936 (disabled by default)
937 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
938 capability is set.
940 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
941 See Documentation/mca.txt.
943 icn= [HW,ISDN]
944 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
946 ide-core.nodma= [HW] (E)IDE subsystem
947 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
948 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
949 .cdrom .chs .ignore_cable are additional options
950 See Documentation/ide/ide.txt.
952 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
953 Claim all unknown PCI IDE storage controllers.
955 idle= [X86]
956 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
957 Poll forces a polling idle loop that can slightly
958 improve the performance of waking up a idle CPU, but
959 will use a lot of power and make the system run hot.
960 Not recommended.
961 idle=mwait: On systems which support MONITOR/MWAIT but
962 the kernel chose to not use it because it doesn't save
963 as much power as a normal idle loop, use the
964 MONITOR/MWAIT idle loop anyways. Performance should be
965 the same as idle=poll.
966 idle=halt: Halt is forced to be used for CPU idle.
967 In such case C2/C3 won't be used again.
968 idle=nomwait: Disable mwait for CPU C-states
970 ignore_loglevel [KNL]
971 Ignore loglevel setting - this will print /all/
972 kernel messages to the console. Useful for debugging.
974 ihash_entries= [KNL]
975 Set number of hash buckets for inode cache.
977 ima_audit= [IMA]
978 Format: { "0" | "1" }
979 0 -- integrity auditing messages. (Default)
980 1 -- enable informational integrity auditing messages.
982 ima_hash= [IMA]
983 Format: { "sha1" | "md5" }
984 default: "sha1"
986 ima_tcb [IMA]
987 Load a policy which meets the needs of the Trusted
988 Computing Base. This means IMA will measure all
989 programs exec'd, files mmap'd for exec, and all files
990 opened for read by uid=0.
992 in2000= [HW,SCSI]
993 See header of drivers/scsi/in2000.c.
995 init= [KNL]
996 Format: <full_path>
997 Run specified binary instead of /sbin/init as init
998 process.
1000 initcall_debug [KNL] Trace initcalls as they are executed. Useful
1001 for working out where the kernel is dying during
1002 startup.
1004 initrd= [BOOT] Specify the location of the initial ramdisk
1006 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1007 Format: <irq>
1009 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1010 on
1011 Enable intel iommu driver.
1012 off
1013 Disable intel iommu driver.
1014 igfx_off [Default Off]
1015 By default, gfx is mapped as normal device. If a gfx
1016 device has a dedicated DMAR unit, the DMAR unit is
1017 bypassed by not enabling DMAR with this option. In
1018 this case, gfx device will use physical address for
1019 DMA.
1020 forcedac [x86_64]
1021 With this option iommu will not optimize to look
1022 for io virtual address below 32 bit forcing dual
1023 address cycle on pci bus for cards supporting greater
1024 than 32 bit addressing. The default is to look
1025 for translation below 32 bit and if not available
1026 then look in the higher range.
1027 strict [Default Off]
1028 With this option on every unmap_single operation will
1029 result in a hardware IOTLB flush operation as opposed
1030 to batching them for performance.
1032 inttest= [IA64]
1034 iomem= Disable strict checking of access to MMIO memory
1035 strict regions from userspace.
1036 relaxed
1038 iommu= [x86]
1039 off
1040 force
1041 noforce
1042 biomerge
1043 panic
1044 nopanic
1045 merge
1046 nomerge
1047 forcesac
1048 soft
1049 pt [x86, IA64]
1051 io7= [HW] IO7 for Marvel based alpha systems
1052 See comment before marvel_specify_io7 in
1053 arch/alpha/kernel/core_marvel.c.
1055 io_delay= [X86] I/O delay method
1056 0x80
1057 Standard port 0x80 based delay
1058 0xed
1059 Alternate port 0xed based delay (needed on some systems)
1060 udelay
1061 Simple two microseconds delay
1062 none
1063 No delay
1065 ip= [IP_PNP]
1066 See Documentation/filesystems/nfs/nfsroot.txt.
1068 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1069 See comment before ip2_setup() in
1070 drivers/char/ip2/ip2base.c.
1072 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1073 See header of drivers/scsi/ips.c.
1075 irqfixup [HW]
1076 When an interrupt is not handled search all handlers
1077 for it. Intended to get systems with badly broken
1078 firmware running.
1080 irqpoll [HW]
1081 When an interrupt is not handled search all handlers
1082 for it. Also check all handlers each timer
1083 interrupt. Intended to get systems with badly broken
1084 firmware running.
1086 isapnp= [ISAPNP]
1087 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1089 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1090 Format:
1091 <cpu number>,...,<cpu number>
1092 or
1093 <cpu number>-<cpu number>
1094 (must be a positive range in ascending order)
1095 or a mixture
1096 <cpu number>,...,<cpu number>-<cpu number>
1098 This option can be used to specify one or more CPUs
1099 to isolate from the general SMP balancing and scheduling
1100 algorithms. You can move a process onto or off an
1101 "isolated" CPU via the CPU affinity syscalls or cpuset.
1102 <cpu number> begins at 0 and the maximum value is
1103 "number of CPUs in system - 1".
1105 This option is the preferred way to isolate CPUs. The
1106 alternative -- manually setting the CPU mask of all
1107 tasks in the system -- can cause problems and
1108 suboptimal load balancer performance.
1110 iucv= [HW,NET]
1112 js= [HW,JOY] Analog joystick
1113 See Documentation/input/joystick.txt.
1115 keepinitrd [HW,ARM]
1117 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1118 specifies the amount of memory usable by the kernel
1119 for non-movable allocations. The requested amount is
1120 spread evenly throughout all nodes in the system. The
1121 remaining memory in each node is used for Movable
1122 pages. In the event, a node is too small to have both
1123 kernelcore and Movable pages, kernelcore pages will
1124 take priority and other nodes will have a larger number
1125 of kernelcore pages. The Movable zone is used for the
1126 allocation of pages that may be reclaimed or moved
1127 by the page migration subsystem. This means that
1128 HugeTLB pages may not be allocated from this zone.
1129 Note that allocations like PTEs-from-HighMem still
1130 use the HighMem zone if it exists, and the Normal
1131 zone if it does not.
1133 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
1134 Format: <Controller#>[,poll interval]
1135 The controller # is the number of the ehci usb debug
1136 port as it is probed via PCI. The poll interval is
1137 optional and is the number seconds in between
1138 each poll cycle to the debug port in case you need
1139 the functionality for interrupting the kernel with
1140 gdb or control-c on the dbgp connection. When
1141 not using this parameter you use sysrq-g to break into
1142 the kernel debugger.
1144 kgdboc= [KGDB,HW] kgdb over consoles.
1145 Requires a tty driver that supports console polling,
1146 or a supported polling keyboard driver (non-usb).
1147 Serial only format: <serial_device>[,baud]
1148 keyboard only format: kbd
1149 keyboard and serial format: kbd,<serial_device>[,baud]
1151 kgdbwait [KGDB] Stop kernel execution and enter the
1152 kernel debugger at the earliest opportunity.
1154 kmac= [MIPS] korina ethernet MAC address.
1155 Configure the RouterBoard 532 series on-chip
1156 Ethernet adapter MAC address.
1158 kmemleak= [KNL] Boot-time kmemleak enable/disable
1159 Valid arguments: on, off
1160 Default: on
1162 kstack=N [X86] Print N words from the kernel stack
1163 in oops dumps.
1165 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1166 Default is 0 (don't ignore, but inject #GP)
1168 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1169 Default is 1 (enabled)
1171 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1172 Default is 0 (off)
1174 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1175 for all guests.
1176 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1178 kvm-intel.bypass_guest_pf=
1179 [KVM,Intel] Disables bypassing of guest page faults
1180 on Intel chips. Default is 1 (enabled)
1182 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1183 (virtualized MMU) support on capable Intel chips.
1184 Default is 1 (enabled)
1186 kvm-intel.emulate_invalid_guest_state=
1187 [KVM,Intel] Enable emulation of invalid guest states
1188 Default is 0 (disabled)
1190 kvm-intel.flexpriority=
1191 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1192 Default is 1 (enabled)
1194 kvm-intel.unrestricted_guest=
1195 [KVM,Intel] Disable unrestricted guest feature
1196 (virtualized real and unpaged mode) on capable
1197 Intel chips. Default is 1 (enabled)
1199 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1200 feature (tagged TLBs) on capable Intel chips.
1201 Default is 1 (enabled)
1203 l2cr= [PPC]
1205 l3cr= [PPC]
1207 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1208 disabled it.
1210 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1211 in C2 power state.
1213 libata.dma= [LIBATA] DMA control
1214 libata.dma=0 Disable all PATA and SATA DMA
1215 libata.dma=1 PATA and SATA Disk DMA only
1216 libata.dma=2 ATAPI (CDROM) DMA only
1217 libata.dma=4 Compact Flash DMA only
1218 Combinations also work, so libata.dma=3 enables DMA
1219 for disks and CDROMs, but not CFs.
1221 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1222 libata.ignore_hpa=0 keep BIOS limits (default)
1223 libata.ignore_hpa=1 ignore limits, using full disk
1225 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1226 when set.
1227 Format: <int>
1229 libata.force= [LIBATA] Force configurations. The format is comma
1230 separated list of "[ID:]VAL" where ID is
1231 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
1232 matching port, link or device. Basically, it matches
1233 the ATA ID string printed on console by libata. If
1234 the whole ID part is omitted, the last PORT and DEVICE
1235 values are used. If ID hasn't been specified yet, the
1236 configuration applies to all ports, links and devices.
1238 If only DEVICE is omitted, the parameter applies to
1239 the port and all links and devices behind it. DEVICE
1240 number of 0 either selects the first device or the
1241 first fan-out link behind PMP device. It does not
1242 select the host link. DEVICE number of 15 selects the
1243 host link and device attached to it.
1245 The VAL specifies the configuration to force. As long
1246 as there's no ambiguity shortcut notation is allowed.
1247 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1248 The following configurations can be forced.
1250 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1251 Any ID with matching PORT is used.
1253 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1255 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1256 udma[/][16,25,33,44,66,100,133] notation is also
1257 allowed.
1259 * [no]ncq: Turn on or off NCQ.
1261 * nohrst, nosrst, norst: suppress hard, soft
1262 and both resets.
1264 * dump_id: dump IDENTIFY data.
1266 If there are multiple matching configurations changing
1267 the same attribute, the last one is used.
1269 memblock=debug [KNL] Enable memblock debug messages.
1271 load_ramdisk= [RAM] List of ramdisks to load from floppy
1272 See Documentation/blockdev/ramdisk.txt.
1274 lockd.nlm_grace_period=P [NFS] Assign grace period.
1275 Format: <integer>
1277 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1278 Format: <integer>
1280 lockd.nlm_timeout=T [NFS] Assign timeout value.
1281 Format: <integer>
1283 lockd.nlm_udpport=M [NFS] Assign UDP port.
1284 Format: <integer>
1286 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1287 Format: <irq>
1289 loglevel= All Kernel Messages with a loglevel smaller than the
1290 console loglevel will be printed to the console. It can
1291 also be changed with klogd or other programs. The
1292 loglevels are defined as follows:
1294 0 (KERN_EMERG) system is unusable
1295 1 (KERN_ALERT) action must be taken immediately
1296 2 (KERN_CRIT) critical conditions
1297 3 (KERN_ERR) error conditions
1298 4 (KERN_WARNING) warning conditions
1299 5 (KERN_NOTICE) normal but significant condition
1300 6 (KERN_INFO) informational
1301 7 (KERN_DEBUG) debug-level messages
1303 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1304 Format: { n | nk | nM }
1305 n must be a power of two. The default size
1306 is set in the kernel config file.
1308 logo.nologo [FB] Disables display of the built-in Linux logo.
1309 This may be used to provide more screen space for
1310 kernel log messages and is useful when debugging
1311 kernel boot problems.
1313 lp=0 [LP] Specify parallel ports to use, e.g,
1314 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1315 lp=reset first parallel port). 'lp=0' disables the
1316 lp=auto printer driver. 'lp=reset' (which can be
1317 specified in addition to the ports) causes
1318 attached printers to be reset. Using
1319 lp=port1,port2,... specifies the parallel ports
1320 to associate lp devices with, starting with
1321 lp0. A port specification may be 'none' to skip
1322 that lp device, or a parport name such as
1323 'parport0'. Specifying 'lp=auto' instead of a
1324 port specification list means that device IDs
1325 from each port should be examined, to see if
1326 an IEEE 1284-compliant printer is attached; if
1327 so, the driver will manage that printer.
1328 See also header of drivers/char/lp.c.
1330 lpj=n [KNL]
1331 Sets loops_per_jiffy to given constant, thus avoiding
1332 time-consuming boot-time autodetection (up to 250 ms per
1333 CPU). 0 enables autodetection (default). To determine
1334 the correct value for your kernel, boot with normal
1335 autodetection and see what value is printed. Note that
1336 on SMP systems the preset will be applied to all CPUs,
1337 which is likely to cause problems if your CPUs need
1338 significantly divergent settings. An incorrect value
1339 will cause delays in the kernel to be wrong, leading to
1340 unpredictable I/O errors and other breakage. Although
1341 unlikely, in the extreme case this might damage your
1342 hardware.
1344 ltpc= [NET]
1345 Format: <io>,<irq>,<dma>
1347 mac5380= [HW,SCSI] Format:
1348 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1350 machvec= [IA64] Force the use of a particular machine-vector
1351 (machvec) in a generic kernel.
1352 Example: machvec=hpzx1_swiotlb
1354 machtype= [Loongson] Share the same kernel image file between different
1355 yeeloong laptop.
1356 Example: machtype=lemote-yeeloong-2f-7inch
1358 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1359 than or equal to this physical address is ignored.
1361 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1362 should make use of. maxcpus=n : n >= 0 limits the
1363 kernel to using 'n' processors. n=0 is a special case,
1364 it is equivalent to "nosmp", which also disables
1365 the IO APIC.
1367 max_loop= [LOOP] Maximum number of loopback devices that can
1368 be mounted
1369 Format: <1-256>
1371 max_luns= [SCSI] Maximum number of LUNs to probe.
1372 Should be between 1 and 2^32-1.
1374 max_report_luns=
1375 [SCSI] Maximum number of LUNs received.
1376 Should be between 1 and 16384.
1378 mcatest= [IA-64]
1380 mce [X86-32] Machine Check Exception
1382 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1384 md= [HW] RAID subsystems devices and level
1385 See Documentation/md.txt.
1387 mdacon= [MDA]
1388 Format: <first>,<last>
1389 Specifies range of consoles to be captured by the MDA.
1391 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1392 Amount of memory to be used when the kernel is not able
1393 to see the whole system memory or for test.
1394 [X86-32] Use together with memmap= to avoid physical
1395 address space collisions. Without memmap= PCI devices
1396 could be placed at addresses belonging to unused RAM.
1398 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1399 memory.
1401 memchunk=nn[KMG]
1402 [KNL,SH] Allow user to override the default size for
1403 per-device physically contiguous DMA buffers.
1405 memmap=exactmap [KNL,X86] Enable setting of an exact
1406 E820 memory map, as specified by the user.
1407 Such memmap=exactmap lines can be constructed based on
1408 BIOS output or other requirements. See the memmap=nn@ss
1409 option description.
1411 memmap=nn[KMG]@ss[KMG]
1412 [KNL] Force usage of a specific region of memory
1413 Region of memory to be used, from ss to ss+nn.
1415 memmap=nn[KMG]#ss[KMG]
1416 [KNL,ACPI] Mark specific memory as ACPI data.
1417 Region of memory to be used, from ss to ss+nn.
1419 memmap=nn[KMG]$ss[KMG]
1420 [KNL,ACPI] Mark specific memory as reserved.
1421 Region of memory to be used, from ss to ss+nn.
1422 Example: Exclude memory from 0x18690000-0x1869ffff
1423 memmap=64K$0x18690000
1424 or
1425 memmap=0x10000$0x18690000
1427 memory_corruption_check=0/1 [X86]
1428 Some BIOSes seem to corrupt the first 64k of
1429 memory when doing things like suspend/resume.
1430 Setting this option will scan the memory
1431 looking for corruption. Enabling this will
1432 both detect corruption and prevent the kernel
1433 from using the memory being corrupted.
1434 However, its intended as a diagnostic tool; if
1435 repeatable BIOS-originated corruption always
1436 affects the same memory, you can use memmap=
1437 to prevent the kernel from using that memory.
1439 memory_corruption_check_size=size [X86]
1440 By default it checks for corruption in the low
1441 64k, making this memory unavailable for normal
1442 use. Use this parameter to scan for
1443 corruption in more or less memory.
1445 memory_corruption_check_period=seconds [X86]
1446 By default it checks for corruption every 60
1447 seconds. Use this parameter to check at some
1448 other rate. 0 disables periodic checking.
1450 memtest= [KNL,X86] Enable memtest
1451 Format: <integer>
1452 default : 0 <disable>
1453 Specifies the number of memtest passes to be
1454 performed. Each pass selects another test
1455 pattern from a given set of patterns. Memtest
1456 fills the memory with this pattern, validates
1457 memory contents and reserves bad memory
1458 regions that are detected.
1460 meye.*= [HW] Set MotionEye Camera parameters
1461 See Documentation/video4linux/meye.txt.
1463 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1464 Multi-Function General Purpose Timers on AMD Geode
1465 platforms.
1467 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1468 the BIOS has incorrectly applied a workaround. TinyBIOS
1469 version 0.98 is known to be affected, 0.99 fixes the
1470 problem by letting the user disable the workaround.
1472 mga= [HW,DRM]
1474 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1475 physical address is ignored.
1477 mini2440= [ARM,HW,KNL]
1478 Format:[0..2][b][c][t]
1479 Default: "0tb"
1480 MINI2440 configuration specification:
1481 0 - The attached screen is the 3.5" TFT
1482 1 - The attached screen is the 7" TFT
1483 2 - The VGA Shield is attached (1024x768)
1484 Leaving out the screen size parameter will not load
1485 the TFT driver, and the framebuffer will be left
1486 unconfigured.
1487 b - Enable backlight. The TFT backlight pin will be
1488 linked to the kernel VESA blanking code and a GPIO
1489 LED. This parameter is not necessary when using the
1490 VGA shield.
1491 c - Enable the s3c camera interface.
1492 t - Reserved for enabling touchscreen support. The
1493 touchscreen support is not enabled in the mainstream
1494 kernel as of 2.6.30, a preliminary port can be found
1495 in the "bleeding edge" mini2440 support kernel at
1496 http://repo.or.cz/w/linux-2.6/mini2440.git
1498 mminit_loglevel=
1499 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1500 parameter allows control of the logging verbosity for
1501 the additional memory initialisation checks. A value
1502 of 0 disables mminit logging and a level of 4 will
1503 log everything. Information is printed at KERN_DEBUG
1504 so loglevel=8 may also need to be specified.
1506 mousedev.tap_time=
1507 [MOUSE] Maximum time between finger touching and
1508 leaving touchpad surface for touch to be considered
1509 a tap and be reported as a left button click (for
1510 touchpads working in absolute mode only).
1511 Format: <msecs>
1512 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1513 reporting absolute coordinates, such as tablets
1514 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1515 reporting absolute coordinates, such as tablets
1517 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1518 is similar to kernelcore except it specifies the
1519 amount of memory used for migratable allocations.
1520 If both kernelcore and movablecore is specified,
1521 then kernelcore will be at *least* the specified
1522 value but may be more. If movablecore on its own
1523 is specified, the administrator must be careful
1524 that the amount of memory usable for all allocations
1525 is not too small.
1527 mpu401= [HW,OSS]
1528 Format: <io>,<irq>
1530 MTD_Partition= [MTD]
1531 Format: <name>,<region-number>,<size>,<offset>
1533 MTD_Region= [MTD] Format:
1534 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1536 mtdparts= [MTD]
1537 See drivers/mtd/cmdlinepart.c.
1539 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1541 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1543 boundary - index of last SLC block on Flex-OneNAND.
1544 The remaining blocks are configured as MLC blocks.
1545 lock - Configure if Flex-OneNAND boundary should be locked.
1546 Once locked, the boundary cannot be changed.
1547 1 indicates lock status, 0 indicates unlock status.
1549 mtdset= [ARM]
1550 ARM/S3C2412 JIVE boot control
1552 See arch/arm/mach-s3c2412/mach-jive.c
1554 mtouchusb.raw_coordinates=
1555 [HW] Make the MicroTouch USB driver use raw coordinates
1556 ('y', default) or cooked coordinates ('n')
1558 mtrr_chunk_size=nn[KMG] [X86]
1559 used for mtrr cleanup. It is largest continuous chunk
1560 that could hold holes aka. UC entries.
1562 mtrr_gran_size=nn[KMG] [X86]
1563 Used for mtrr cleanup. It is granularity of mtrr block.
1564 Default is 1.
1565 Large value could prevent small alignment from
1566 using up MTRRs.
1568 mtrr_spare_reg_nr=n [X86]
1569 Format: <integer>
1570 Range: 0,7 : spare reg number
1571 Default : 1
1572 Used for mtrr cleanup. It is spare mtrr entries number.
1573 Set to 2 or more if your graphical card needs more.
1575 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1577 NCR_D700= [HW,SCSI]
1578 See header of drivers/scsi/NCR_D700.c.
1580 ncr5380= [HW,SCSI]
1582 ncr53c400= [HW,SCSI]
1584 ncr53c400a= [HW,SCSI]
1586 ncr53c406a= [HW,SCSI]
1588 ncr53c8xx= [HW,SCSI]
1590 netdev= [NET] Network devices parameters
1591 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1592 Note that mem_start is often overloaded to mean
1593 something different and driver-specific.
1594 This usage is only documented in each driver source
1595 file if at all.
1597 nf_conntrack.acct=
1598 [NETFILTER] Enable connection tracking flow accounting
1599 0 to disable accounting
1600 1 to enable accounting
1601 Default value is 0.
1603 nfsaddrs= [NFS]
1604 See Documentation/filesystems/nfs/nfsroot.txt.
1606 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1607 See Documentation/filesystems/nfs/nfsroot.txt.
1609 nfs.callback_tcpport=
1610 [NFS] set the TCP port on which the NFSv4 callback
1611 channel should listen.
1613 nfs.cache_getent=
1614 [NFS] sets the pathname to the program which is used
1615 to update the NFS client cache entries.
1617 nfs.cache_getent_timeout=
1618 [NFS] sets the timeout after which an attempt to
1619 update a cache entry is deemed to have failed.
1621 nfs.idmap_cache_timeout=
1622 [NFS] set the maximum lifetime for idmapper cache
1623 entries.
1625 nfs.enable_ino64=
1626 [NFS] enable 64-bit inode numbers.
1627 If zero, the NFS client will fake up a 32-bit inode
1628 number for the readdir() and stat() syscalls instead
1629 of returning the full 64-bit number.
1630 The default is to return 64-bit inode numbers.
1632 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1633 when a NMI is triggered.
1634 Format: [state][,regs][,debounce][,die]
1636 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1637 Format: [panic,][num]
1638 Valid num: 0,1,2
1639 0 - turn nmi_watchdog off
1640 1 - use the IO-APIC timer for the NMI watchdog
1641 2 - use the local APIC for the NMI watchdog using
1642 a performance counter. Note: This will use one
1643 performance counter and the local APIC's performance
1644 vector.
1645 When panic is specified, panic when an NMI watchdog
1646 timeout occurs.
1647 This is useful when you use a panic=... timeout and
1648 need the box quickly up again.
1649 Instead of 1 and 2 it is possible to use the following
1650 symbolic names: lapic and ioapic
1651 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1653 netpoll.carrier_timeout=
1654 [NET] Specifies amount of time (in seconds) that
1655 netpoll should wait for a carrier. By default netpoll
1656 waits 4 seconds.
1658 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1659 emulation library even if a 387 maths coprocessor
1660 is present.
1662 no_console_suspend
1663 [HW] Never suspend the console
1664 Disable suspending of consoles during suspend and
1665 hibernate operations. Once disabled, debugging
1666 messages can reach various consoles while the rest
1667 of the system is being put to sleep (ie, while
1668 debugging driver suspend/resume hooks). This may
1669 not work reliably with all consoles, but is known
1670 to work with serial and VGA consoles.
1672 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1673 caches in the slab allocator. Saves per-node memory,
1674 but will impact performance.
1676 noalign [KNL,ARM]
1678 noapic [SMP,APIC] Tells the kernel to not make use of any
1679 IOAPICs that may be present in the system.
1681 nobats [PPC] Do not use BATs for mapping kernel lowmem
1682 on "Classic" PPC cores.
1684 nocache [ARM]
1686 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1688 nodelayacct [KNL] Disable per-task delay accounting
1690 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1692 nodsp [SH] Disable hardware DSP at boot time.
1694 noefi [X86] Disable EFI runtime services support.
1696 noexec [IA-64]
1698 noexec [X86]
1699 On X86-32 available only on PAE configured kernels.
1700 noexec=on: enable non-executable mappings (default)
1701 noexec=off: disable non-executable mappings
1703 noexec32 [X86-64]
1704 This affects only 32-bit executables.
1705 noexec32=on: enable non-executable mappings (default)
1706 read doesn't imply executable mappings
1707 noexec32=off: disable non-executable mappings
1708 read implies executable mappings
1710 nofpu [SH] Disable hardware FPU at boot time.
1712 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1713 register save and restore. The kernel will only save
1714 legacy floating-point registers on task switch.
1716 noxsave [BUGS=X86] Disables x86 extended register state save
1717 and restore using xsave. The kernel will fallback to
1718 enabling legacy floating-point and sse state.
1720 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1721 wfi(ARM) instruction doesn't work correctly and not to
1722 use it. This is also useful when using JTAG debugger.
1724 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1725 instruction doesn't work correctly and not to
1726 use it.
1728 no_file_caps Tells the kernel not to honor file capabilities. The
1729 only way then for a file to be executed with privilege
1730 is to be setuid root or executed by root.
1732 nohalt [IA-64] Tells the kernel not to use the power saving
1733 function PAL_HALT_LIGHT when idle. This increases
1734 power-consumption. On the positive side, it reduces
1735 interrupt wake-up latency, which may improve performance
1736 in certain environments such as networked servers or
1737 real-time systems.
1739 nohz= [KNL] Boottime enable/disable dynamic ticks
1740 Valid arguments: on, off
1741 Default: on
1743 noiotrap [SH] Disables trapped I/O port accesses.
1745 noirqdebug [X86-32] Disables the code which attempts to detect and
1746 disable unhandled interrupt sources.
1748 no_timer_check [X86,APIC] Disables the code which tests for
1749 broken timer IRQ sources.
1751 noisapnp [ISAPNP] Disables ISA PnP code.
1753 noinitrd [RAM] Tells the kernel not to load any configured
1754 initial RAM disk.
1756 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1757 remapping.
1759 nointroute [IA-64]
1761 nojitter [IA64] Disables jitter checking for ITC timers.
1763 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1765 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1767 noltlbs [PPC] Do not use large page/tlb entries for kernel
1768 lowmem mapping on PPC40x.
1770 nomca [IA-64] Disable machine check abort handling
1772 nomce [X86-32] Machine Check Exception
1774 nomfgpt [X86-32] Disable Multi-Function General Purpose
1775 Timer usage (for AMD Geode machines).
1777 nopat [X86] Disable PAT (page attribute table extension of
1778 pagetables) support.
1780 norandmaps Don't use address space randomization. Equivalent to
1781 echo 0 > /proc/sys/kernel/randomize_va_space
1783 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1785 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1786 with UP alternatives
1788 noresidual [PPC] Don't use residual data on PReP machines.
1790 noresume [SWSUSP] Disables resume and restores original swap
1791 space.
1793 no-scroll [VGA] Disables scrollback.
1794 This is required for the Braillex ib80-piezo Braille
1795 reader made by F.H. Papenmeier (Germany).
1797 nosbagart [IA-64]
1799 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1801 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1802 and disable the IO APIC. legacy for "maxcpus=0".
1804 nosoftlockup [KNL] Disable the soft-lockup detector.
1806 noswapaccount [KNL] Disable accounting of swap in memory resource
1807 controller. (See Documentation/cgroups/memory.txt)
1809 nosync [HW,M68K] Disables sync negotiation for all devices.
1811 notsc [BUGS=X86-32] Disable Time Stamp Counter
1813 nousb [USB] Disable the USB subsystem
1815 nowb [ARM]
1817 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1819 nptcg= [IA64] Override max number of concurrent global TLB
1820 purges which is reported from either PAL_VM_SUMMARY or
1821 SAL PALO.
1823 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1824 could support. nr_cpus=n : n >= 1 limits the kernel to
1825 supporting 'n' processors. Later in runtime you can not
1826 use hotplug cpu feature to put more cpu back to online.
1827 just like you compile the kernel NR_CPUS=n
1829 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1831 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1832 one of ['zone', 'node', 'default'] can be specified
1833 This can be set from sysctl after boot.
1834 See Documentation/sysctl/vm.txt for details.
1836 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1837 See Documentation/debugging-via-ohci1394.txt for more
1838 info.
1840 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1841 Rather than timing out after 20 ms if an EC
1842 command is not properly ACKed, override the length
1843 of the timeout. We have interrupts disabled while
1844 waiting for the ACK, so if this is set too high
1845 interrupts *may* be lost!
1847 omap_mux= [OMAP] Override bootloader pin multiplexing.
1848 Format: <mux_mode0.mode_name=value>...
1849 For example, to override I2C bus2:
1850 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1852 opl3= [HW,OSS]
1853 Format: <io>
1855 oprofile.timer= [HW]
1856 Use timer interrupt instead of performance counters
1858 oprofile.cpu_type= Force an oprofile cpu type
1859 This might be useful if you have an older oprofile
1860 userland or if you want common events.
1861 Format: { arch_perfmon }
1862 arch_perfmon: [X86] Force use of architectural
1863 perfmon on Intel CPUs instead of the
1864 CPU specific event set.
1866 osst= [HW,SCSI] SCSI Tape Driver
1867 Format: <buffer_size>,<write_threshold>
1868 See also Documentation/scsi/st.txt.
1870 panic= [KNL] Kernel behaviour on panic
1871 Format: <timeout>
1873 parkbd.port= [HW] Parallel port number the keyboard adapter is
1874 connected to, default is 0.
1875 Format: <parport#>
1876 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1877 0 for XT, 1 for AT (default is AT).
1878 Format: <mode>
1880 parport= [HW,PPT] Specify parallel ports. 0 disables.
1881 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1882 Use 'auto' to force the driver to use any
1883 IRQ/DMA settings detected (the default is to
1884 ignore detected IRQ/DMA settings because of
1885 possible conflicts). You can specify the base
1886 address, IRQ, and DMA settings; IRQ and DMA
1887 should be numbers, or 'auto' (for using detected
1888 settings on that particular port), or 'nofifo'
1889 (to avoid using a FIFO even if it is detected).
1890 Parallel ports are assigned in the order they
1891 are specified on the command line, starting
1892 with parport0.
1894 parport_init_mode= [HW,PPT]
1895 Configure VIA parallel port to operate in
1896 a specific mode. This is necessary on Pegasos
1897 computer where firmware has no options for setting
1898 up parallel port mode and sets it to spp.
1899 Currently this function knows 686a and 8231 chips.
1900 Format: [spp|ps2|epp|ecp|ecpepp]
1902 pas2= [HW,OSS] Format:
1903 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1905 pas16= [HW,SCSI]
1906 See header of drivers/scsi/pas16.c.
1908 pause_on_oops=
1909 Halt all CPUs after the first oops has been printed for
1910 the specified number of seconds. This is to be used if
1911 your oopses keep scrolling off the screen.
1913 pcbit= [HW,ISDN]
1915 pcd. [PARIDE]
1916 See header of drivers/block/paride/pcd.c.
1917 See also Documentation/blockdev/paride.txt.
1919 pci=option[,option...] [PCI] various PCI subsystem options:
1920 earlydump [X86] dump PCI config space before the kernel
1921 changes anything
1922 off [X86] don't probe for the PCI bus
1923 bios [X86-32] force use of PCI BIOS, don't access
1924 the hardware directly. Use this if your machine
1925 has a non-standard PCI host bridge.
1926 nobios [X86-32] disallow use of PCI BIOS, only direct
1927 hardware access methods are allowed. Use this
1928 if you experience crashes upon bootup and you
1929 suspect they are caused by the BIOS.
1930 conf1 [X86] Force use of PCI Configuration
1931 Mechanism 1.
1932 conf2 [X86] Force use of PCI Configuration
1933 Mechanism 2.
1934 noaer [PCIE] If the PCIEAER kernel config parameter is
1935 enabled, this kernel boot option can be used to
1936 disable the use of PCIE advanced error reporting.
1937 nodomains [PCI] Disable support for multiple PCI
1938 root domains (aka PCI segments, in ACPI-speak).
1939 nommconf [X86] Disable use of MMCONFIG for PCI
1940 Configuration
1941 check_enable_amd_mmconf [X86] check for and enable
1942 properly configured MMIO access to PCI
1943 config space on AMD family 10h CPU
1944 nomsi [MSI] If the PCI_MSI kernel config parameter is
1945 enabled, this kernel boot option can be used to
1946 disable the use of MSI interrupts system-wide.
1947 noioapicquirk [APIC] Disable all boot interrupt quirks.
1948 Safety option to keep boot IRQs enabled. This
1949 should never be necessary.
1950 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1951 primary IO-APIC for bridges that cannot disable
1952 boot IRQs. This fixes a source of spurious IRQs
1953 when the system masks IRQs.
1954 noioapicreroute [APIC] Disable workaround that uses the
1955 boot IRQ equivalent of an IRQ that connects to
1956 a chipset where boot IRQs cannot be disabled.
1957 The opposite of ioapicreroute.
1958 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1959 routing table. These calls are known to be buggy
1960 on several machines and they hang the machine
1961 when used, but on other computers it's the only
1962 way to get the interrupt routing table. Try
1963 this option if the kernel is unable to allocate
1964 IRQs or discover secondary PCI buses on your
1965 motherboard.
1966 rom [X86] Assign address space to expansion ROMs.
1967 Use with caution as certain devices share
1968 address decoders between ROMs and other
1969 resources.
1970 norom [X86] Do not assign address space to
1971 expansion ROMs that do not already have
1972 BIOS assigned address ranges.
1973 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1974 assigned automatically to PCI devices. You can
1975 make the kernel exclude IRQs of your ISA cards
1976 this way.
1977 pirqaddr=0xAAAAA [X86] Specify the physical address
1978 of the PIRQ table (normally generated
1979 by the BIOS) if it is outside the
1980 F0000h-100000h range.
1981 lastbus=N [X86] Scan all buses thru bus #N. Can be
1982 useful if the kernel is unable to find your
1983 secondary buses and you want to tell it
1984 explicitly which ones they are.
1985 assign-busses [X86] Always assign all PCI bus
1986 numbers ourselves, overriding
1987 whatever the firmware may have done.
1988 usepirqmask [X86] Honor the possible IRQ mask stored
1989 in the BIOS $PIR table. This is needed on
1990 some systems with broken BIOSes, notably
1991 some HP Pavilion N5400 and Omnibook XE3
1992 notebooks. This will have no effect if ACPI
1993 IRQ routing is enabled.
1994 noacpi [X86] Do not use ACPI for IRQ routing
1995 or for PCI scanning.
1996 use_crs [X86] Use PCI host bridge window information
1997 from ACPI. On BIOSes from 2008 or later, this
1998 is enabled by default. If you need to use this,
1999 please report a bug.
2000 nocrs [X86] Ignore PCI host bridge windows from ACPI.
2001 If you need to use this, please report a bug.
2002 routeirq Do IRQ routing for all PCI devices.
2003 This is normally done in pci_enable_device(),
2004 so this option is a temporary workaround
2005 for broken drivers that don't call it.
2006 skip_isa_align [X86] do not align io start addr, so can
2007 handle more pci cards
2008 firmware [ARM] Do not re-enumerate the bus but instead
2009 just use the configuration from the
2010 bootloader. This is currently used on
2011 IXP2000 systems where the bus has to be
2012 configured a certain way for adjunct CPUs.
2013 noearly [X86] Don't do any early type 1 scanning.
2014 This might help on some broken boards which
2015 machine check when some devices' config space
2016 is read. But various workarounds are disabled
2017 and some IOMMU drivers will not work.
2018 bfsort Sort PCI devices into breadth-first order.
2019 This sorting is done to get a device
2020 order compatible with older (<= 2.4) kernels.
2021 nobfsort Don't sort PCI devices into breadth-first order.
2022 cbiosize=nn[KMG] The fixed amount of bus space which is
2023 reserved for the CardBus bridge's IO window.
2024 The default value is 256 bytes.
2025 cbmemsize=nn[KMG] The fixed amount of bus space which is
2026 reserved for the CardBus bridge's memory
2027 window. The default value is 64 megabytes.
2028 resource_alignment=
2029 Format:
2030 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2031 Specifies alignment and device to reassign
2032 aligned memory resources.
2033 If <order of align> is not specified,
2034 PAGE_SIZE is used as alignment.
2035 PCI-PCI bridge can be specified, if resource
2036 windows need to be expanded.
2037 ecrc= Enable/disable PCIe ECRC (transaction layer
2038 end-to-end CRC checking).
2039 bios: Use BIOS/firmware settings. This is the
2040 the default.
2041 off: Turn ECRC off
2042 on: Turn ECRC on.
2044 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2045 Management.
2046 off Disable ASPM.
2047 force Enable ASPM even on devices that claim not to support it.
2048 WARNING: Forcing ASPM on may cause system lockups.
2050 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2051 Format: {auto|force}[,nomsi]
2052 auto Use native PCIe PME signaling if the BIOS allows the
2053 kernel to control PCIe config registers of root ports.
2054 force Use native PCIe PME signaling even if the BIOS refuses
2055 to allow the kernel to control the relevant PCIe config
2056 registers.
2057 nomsi Do not use MSI for native PCIe PME signaling (this makes
2058 all PCIe root ports use INTx for everything).
2060 pcmv= [HW,PCMCIA] BadgePAD 4
2062 pd. [PARIDE]
2063 See Documentation/blockdev/paride.txt.
2065 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2066 boot time.
2067 Format: { 0 | 1 }
2068 See arch/parisc/kernel/pdc_chassis.c
2070 percpu_alloc= Select which percpu first chunk allocator to use.
2071 Currently supported values are "embed" and "page".
2072 Archs may support subset or none of the selections.
2073 See comments in mm/percpu.c for details on each
2074 allocator. This parameter is primarily for debugging
2075 and performance comparison.
2077 pf. [PARIDE]
2078 See Documentation/blockdev/paride.txt.
2080 pg. [PARIDE]
2081 See Documentation/blockdev/paride.txt.
2083 pirq= [SMP,APIC] Manual mp-table setup
2084 See Documentation/x86/i386/IO-APIC.txt.
2086 plip= [PPT,NET] Parallel port network link
2087 Format: { parport<nr> | timid | 0 }
2088 See also Documentation/parport.txt.
2090 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2091 Override pmtimer IOPort with a hex value.
2092 e.g. pmtmr=0x508
2094 pnp.debug [PNP]
2095 Enable PNP debug messages. This depends on the
2096 CONFIG_PNP_DEBUG_MESSAGES option.
2098 pnpacpi= [ACPI]
2099 { off }
2101 pnpbios= [ISAPNP]
2102 { on | off | curr | res | no-curr | no-res }
2104 pnp_reserve_irq=
2105 [ISAPNP] Exclude IRQs for the autoconfiguration
2107 pnp_reserve_dma=
2108 [ISAPNP] Exclude DMAs for the autoconfiguration
2110 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2111 Ranges are in pairs (I/O port base and size).
2113 pnp_reserve_mem=
2114 [ISAPNP] Exclude memory regions for the
2115 autoconfiguration.
2116 Ranges are in pairs (memory base and size).
2118 ports= [IP_VS_FTP] IPVS ftp helper module
2119 Default is 21.
2120 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2121 may be specified.
2122 Format: <port>,<port>....
2124 print-fatal-signals=
2125 [KNL] debug: print fatal signals
2127 If enabled, warn about various signal handling
2128 related application anomalies: too many signals,
2129 too many POSIX.1 timers, fatal signals causing a
2130 coredump - etc.
2132 If you hit the warning due to signal overflow,
2133 you might want to try "ulimit -i unlimited".
2135 default: off.
2137 printk.time= Show timing data prefixed to each printk message line
2138 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2140 processor.max_cstate= [HW,ACPI]
2141 Limit processor to maximum C-state
2142 max_cstate=9 overrides any DMI blacklist limit.
2144 processor.nocst [HW,ACPI]
2145 Ignore the _CST method to determine C-states,
2146 instead using the legacy FADT method
2148 profile= [KNL] Enable kernel profiling via /proc/profile
2149 Format: [schedule,]<number>
2150 Param: "schedule" - profile schedule points.
2151 Param: <number> - step/bucket size as a power of 2 for
2152 statistical time based profiling.
2153 Param: "sleep" - profile D-state sleeping (millisecs).
2154 Requires CONFIG_SCHEDSTATS
2155 Param: "kvm" - profile VM exits.
2157 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2158 before loading.
2159 See Documentation/blockdev/ramdisk.txt.
2161 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2162 probe for; one of (bare|imps|exps|lifebook|any).
2163 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2164 per second.
2165 psmouse.resetafter= [HW,MOUSE]
2166 Try to reset the device after so many bad packets
2167 (0 = never).
2168 psmouse.resolution=
2169 [HW,MOUSE] Set desired mouse resolution, in dpi.
2170 psmouse.smartscroll=
2171 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2172 0 = disabled, 1 = enabled (default).
2174 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2175 Format:
2176 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2178 pt. [PARIDE]
2179 See Documentation/blockdev/paride.txt.
2181 pty.legacy_count=
2182 [KNL] Number of legacy pty's. Overwrites compiled-in
2183 default number.
2185 quiet [KNL] Disable most log messages
2187 r128= [HW,DRM]
2189 raid= [HW,RAID]
2190 See Documentation/md.txt.
2192 ramdisk_blocksize= [RAM]
2193 See Documentation/blockdev/ramdisk.txt.
2195 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2196 See Documentation/blockdev/ramdisk.txt.
2198 rcupdate.blimit= [KNL,BOOT]
2199 Set maximum number of finished RCU callbacks to process
2200 in one batch.
2202 rcupdate.qhimark= [KNL,BOOT]
2203 Set threshold of queued
2204 RCU callbacks over which batch limiting is disabled.
2206 rcupdate.qlowmark= [KNL,BOOT]
2207 Set threshold of queued RCU callbacks below which
2208 batch limiting is re-enabled.
2210 rdinit= [KNL]
2211 Format: <full_path>
2212 Run specified binary instead of /init from the ramdisk,
2213 used for early userspace startup. See initrd.
2215 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2216 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2217 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2219 relax_domain_level=
2220 [KNL, SMP] Set scheduler's default relax_domain_level.
2221 See Documentation/cgroups/cpusets.txt.
2223 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2225 reservetop= [X86-32]
2226 Format: nn[KMG]
2227 Reserves a hole at the top of the kernel virtual
2228 address space.
2230 reset_devices [KNL] Force drivers to reset the underlying device
2231 during initialization.
2233 resume= [SWSUSP]
2234 Specify the partition device for software suspend
2236 resume_offset= [SWSUSP]
2237 Specify the offset from the beginning of the partition
2238 given by "resume=" at which the swap header is located,
2239 in <PAGE_SIZE> units (needed only for swap files).
2240 See Documentation/power/swsusp-and-swap-files.txt
2242 retain_initrd [RAM] Keep initrd memory after extraction
2244 rhash_entries= [KNL,NET]
2245 Set number of hash buckets for route cache
2247 riscom8= [HW,SERIAL]
2248 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2250 ro [KNL] Mount root device read-only on boot
2252 root= [KNL] Root filesystem
2254 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2255 mount the root filesystem
2257 rootflags= [KNL] Set root filesystem mount option string
2259 rootfstype= [KNL] Set root filesystem type
2261 rootwait [KNL] Wait (indefinitely) for root device to show up.
2262 Useful for devices that are detected asynchronously
2263 (e.g. USB and MMC devices).
2265 rw [KNL] Mount root device read-write on boot
2267 S [KNL] Run init in single mode
2269 sa1100ir [NET]
2270 See drivers/net/irda/sa1100_ir.c.
2272 sbni= [NET] Granch SBNI12 leased line adapter
2274 sched_debug [KNL] Enables verbose scheduler debug messages.
2276 scsi_debug_*= [SCSI]
2277 See drivers/scsi/scsi_debug.c.
2279 scsi_default_dev_flags=
2280 [SCSI] SCSI default device flags
2281 Format: <integer>
2283 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2284 Format: <vendor>:<model>:<flags>
2285 (flags are integer value)
2287 scsi_logging_level= [SCSI] a bit mask of logging levels
2288 See drivers/scsi/scsi_logging.h for bits. Also
2289 settable via sysctl at dev.scsi.logging_level
2290 (/proc/sys/dev/scsi/logging_level).
2291 There is also a nice 'scsi_logging_level' script in the
2292 S390-tools package, available for download at
2293 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2295 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2296 discovered. async scans them in kernel threads,
2297 allowing boot to proceed. none ignores them, expecting
2298 user space to do the scan.
2300 security= [SECURITY] Choose a security module to enable at boot.
2301 If this boot parameter is not specified, only the first
2302 security module asking for security registration will be
2303 loaded. An invalid security module name will be treated
2304 as if no module has been chosen.
2306 selinux= [SELINUX] Disable or enable SELinux at boot time.
2307 Format: { "0" | "1" }
2308 See security/selinux/Kconfig help text.
2309 0 -- disable.
2310 1 -- enable.
2311 Default value is set via kernel config option.
2312 If enabled at boot time, /selinux/disable can be used
2313 later to disable prior to initial policy load.
2315 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
2316 Format: { "0" | "1" }
2317 See security/apparmor/Kconfig help text
2318 0 -- disable.
2319 1 -- enable.
2320 Default value is set via kernel config option.
2322 serialnumber [BUGS=X86-32]
2324 shapers= [NET]
2325 Maximal number of shapers.
2327 show_msr= [x86] show boot-time MSR settings
2328 Format: { <integer> }
2329 Show boot-time (BIOS-initialized) MSR settings.
2330 The parameter means the number of CPUs to show,
2331 for example 1 means boot CPU only.
2333 sim710= [SCSI,HW]
2334 See header of drivers/scsi/sim710.c.
2336 simeth= [IA-64]
2337 simscsi=
2339 slram= [HW,MTD]
2341 slub_debug[=options[,slabs]] [MM, SLUB]
2342 Enabling slub_debug allows one to determine the
2343 culprit if slab objects become corrupted. Enabling
2344 slub_debug can create guard zones around objects and
2345 may poison objects when not in use. Also tracks the
2346 last alloc / free. For more information see
2347 Documentation/vm/slub.txt.
2349 slub_max_order= [MM, SLUB]
2350 Determines the maximum allowed order for slabs.
2351 A high setting may cause OOMs due to memory
2352 fragmentation. For more information see
2353 Documentation/vm/slub.txt.
2355 slub_min_objects= [MM, SLUB]
2356 The minimum number of objects per slab. SLUB will
2357 increase the slab order up to slub_max_order to
2358 generate a sufficiently large slab able to contain
2359 the number of objects indicated. The higher the number
2360 of objects the smaller the overhead of tracking slabs
2361 and the less frequently locks need to be acquired.
2362 For more information see Documentation/vm/slub.txt.
2364 slub_min_order= [MM, SLUB]
2365 Determines the mininum page order for slabs. Must be
2366 lower than slub_max_order.
2367 For more information see Documentation/vm/slub.txt.
2369 slub_nomerge [MM, SLUB]
2370 Disable merging of slabs with similar size. May be
2371 necessary if there is some reason to distinguish
2372 allocs to different slabs. Debug options disable
2373 merging on their own.
2374 For more information see Documentation/vm/slub.txt.
2376 smart2= [HW]
2377 Format: <io1>[,<io2>[,...,<io8>]]
2379 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2380 attempt to substitute SMP alternatives once at boot.
2382 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2383 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2384 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2385 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2386 smsc-ircc2.ircc_irq= [HW] IRQ line
2387 smsc-ircc2.ircc_dma= [HW] DMA channel
2388 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2389 0: Toshiba Satellite 1800 (GP data pin select)
2390 1: Fast pin select (default)
2391 2: ATC IRMode
2393 snd-ad1816a= [HW,ALSA]
2395 snd-ad1848= [HW,ALSA]
2397 snd-ali5451= [HW,ALSA]
2399 snd-als100= [HW,ALSA]
2401 snd-als4000= [HW,ALSA]
2403 snd-azt2320= [HW,ALSA]
2405 snd-cmi8330= [HW,ALSA]
2407 snd-cmipci= [HW,ALSA]
2409 snd-cs4231= [HW,ALSA]
2411 snd-cs4232= [HW,ALSA]
2413 snd-cs4236= [HW,ALSA]
2415 snd-cs4281= [HW,ALSA]
2417 snd-cs46xx= [HW,ALSA]
2419 snd-dt019x= [HW,ALSA]
2421 snd-dummy= [HW,ALSA]
2423 snd-emu10k1= [HW,ALSA]
2425 snd-ens1370= [HW,ALSA]
2427 snd-ens1371= [HW,ALSA]
2429 snd-es968= [HW,ALSA]
2431 snd-es1688= [HW,ALSA]
2433 snd-es18xx= [HW,ALSA]
2435 snd-es1938= [HW,ALSA]
2437 snd-es1968= [HW,ALSA]
2439 snd-fm801= [HW,ALSA]
2441 snd-gusclassic= [HW,ALSA]
2443 snd-gusextreme= [HW,ALSA]
2445 snd-gusmax= [HW,ALSA]
2447 snd-hdsp= [HW,ALSA]
2449 snd-ice1712= [HW,ALSA]
2451 snd-intel8x0= [HW,ALSA]
2453 snd-interwave= [HW,ALSA]
2455 snd-interwave-stb=
2456 [HW,ALSA]
2458 snd-korg1212= [HW,ALSA]
2460 snd-maestro3= [HW,ALSA]
2462 snd-mpu401= [HW,ALSA]
2464 snd-mtpav= [HW,ALSA]
2466 snd-nm256= [HW,ALSA]
2468 snd-opl3sa2= [HW,ALSA]
2470 snd-opti92x-ad1848=
2471 [HW,ALSA]
2473 snd-opti92x-cs4231=
2474 [HW,ALSA]
2476 snd-opti93x= [HW,ALSA]
2478 snd-pmac= [HW,ALSA]
2480 snd-rme32= [HW,ALSA]
2482 snd-rme96= [HW,ALSA]
2484 snd-rme9652= [HW,ALSA]
2486 snd-sb8= [HW,ALSA]
2488 snd-sb16= [HW,ALSA]
2490 snd-sbawe= [HW,ALSA]
2492 snd-serial= [HW,ALSA]
2494 snd-sgalaxy= [HW,ALSA]
2496 snd-sonicvibes= [HW,ALSA]
2498 snd-sun-amd7930=
2499 [HW,ALSA]
2501 snd-sun-cs4231= [HW,ALSA]
2503 snd-trident= [HW,ALSA]
2505 snd-usb-audio= [HW,ALSA,USB]
2507 snd-via82xx= [HW,ALSA]
2509 snd-virmidi= [HW,ALSA]
2511 snd-wavefront= [HW,ALSA]
2513 snd-ymfpci= [HW,ALSA]
2515 softlockup_panic=
2516 [KNL] Should the soft-lockup detector generate panics.
2518 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2519 See Documentation/sonypi.txt
2521 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2522 See Documentation/serial/specialix.txt.
2524 spia_io_base= [HW,MTD]
2525 spia_fio_base=
2526 spia_pedr=
2527 spia_peddr=
2529 sscape= [HW,OSS]
2530 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2532 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2533 See Documentation/scsi/st.txt.
2535 stacktrace [FTRACE]
2536 Enabled the stack tracer on boot up.
2538 sti= [PARISC,HW]
2539 Format: <num>
2540 Set the STI (builtin display/keyboard on the HP-PARISC
2541 machines) console (graphic card) which should be used
2542 as the initial boot-console.
2543 See also comment in drivers/video/console/sticore.c.
2545 sti_font= [HW]
2546 See comment in drivers/video/console/sticore.c.
2548 stifb= [HW]
2549 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2551 sunrpc.min_resvport=
2552 sunrpc.max_resvport=
2553 [NFS,SUNRPC]
2554 SunRPC servers often require that client requests
2555 originate from a privileged port (i.e. a port in the
2556 range 0 < portnr < 1024).
2557 An administrator who wishes to reserve some of these
2558 ports for other uses may adjust the range that the
2559 kernel's sunrpc client considers to be privileged
2560 using these two parameters to set the minimum and
2561 maximum port values.
2563 sunrpc.pool_mode=
2564 [NFS]
2565 Control how the NFS server code allocates CPUs to
2566 service thread pools. Depending on how many NICs
2567 you have and where their interrupts are bound, this
2568 option will affect which CPUs will do NFS serving.
2569 Note: this parameter cannot be changed while the
2570 NFS server is running.
2572 auto the server chooses an appropriate mode
2573 automatically using heuristics
2574 global a single global pool contains all CPUs
2575 percpu one pool for each CPU
2576 pernode one pool for each NUMA node (equivalent
2577 to global on non-NUMA machines)
2579 sunrpc.tcp_slot_table_entries=
2580 sunrpc.udp_slot_table_entries=
2581 [NFS,SUNRPC]
2582 Sets the upper limit on the number of simultaneous
2583 RPC calls that can be sent from the client to a
2584 server. Increasing these values may allow you to
2585 improve throughput, but will also increase the
2586 amount of memory reserved for use by the client.
2588 swiotlb= [IA-64] Number of I/O TLB slabs
2590 switches= [HW,M68k]
2592 sym53c416= [HW,SCSI]
2593 See header of drivers/scsi/sym53c416.c.
2595 sysrq_always_enabled
2596 [KNL]
2597 Ignore sysrq setting - this boot parameter will
2598 neutralize any effect of /proc/sys/kernel/sysrq.
2599 Useful for debugging.
2601 t128= [HW,SCSI]
2602 See header of drivers/scsi/t128.c.
2604 tdfx= [HW,DRM]
2606 test_suspend= [SUSPEND]
2607 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2608 standby suspend) as the system sleep state to briefly
2609 enter during system startup. The system is woken from
2610 this state using a wakeup-capable RTC alarm.
2612 thash_entries= [KNL,NET]
2613 Set number of hash buckets for TCP connection
2615 thermal.act= [HW,ACPI]
2616 -1: disable all active trip points in all thermal zones
2617 <degrees C>: override all lowest active trip points
2619 thermal.crt= [HW,ACPI]
2620 -1: disable all critical trip points in all thermal zones
2621 <degrees C>: override all critical trip points
2623 thermal.nocrt= [HW,ACPI]
2624 Set to disable actions on ACPI thermal zone
2625 critical and hot trip points.
2627 thermal.off= [HW,ACPI]
2628 1: disable ACPI thermal control
2630 thermal.psv= [HW,ACPI]
2631 -1: disable all passive trip points
2632 <degrees C>: override all passive trip points to this
2633 value
2635 thermal.tzp= [HW,ACPI]
2636 Specify global default ACPI thermal zone polling rate
2637 <deci-seconds>: poll all this frequency
2638 0: no polling (default)
2640 tmscsim= [HW,SCSI]
2641 See comment before function dc390_setup() in
2642 drivers/scsi/tmscsim.c.
2644 topology= [S390]
2645 Format: {off | on}
2646 Specify if the kernel should make use of the cpu
2647 topology informations if the hardware supports these.
2648 The scheduler will make use of these informations and
2649 e.g. base its process migration decisions on it.
2650 Default is off.
2652 tp720= [HW,PS2]
2654 tpm_suspend_pcr=[HW,TPM]
2655 Format: integer pcr id
2656 Specify that at suspend time, the tpm driver
2657 should extend the specified pcr with zeros,
2658 as a workaround for some chips which fail to
2659 flush the last written pcr on TPM_SaveState.
2660 This will guarantee that all the other pcrs
2661 are saved.
2663 trace_buf_size=nn[KMG]
2664 [FTRACE] will set tracing buffer size.
2666 trace_event=[event-list]
2667 [FTRACE] Set and start specified trace events in order
2668 to facilitate early boot debugging.
2669 See also Documentation/trace/events.txt
2671 trix= [HW,OSS] MediaTrix AudioTrix Pro
2672 Format:
2673 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2675 tsc= Disable clocksource-must-verify flag for TSC.
2676 Format: <string>
2677 [x86] reliable: mark tsc clocksource as reliable, this
2678 disables clocksource verification at runtime.
2679 Used to enable high-resolution timer mode on older
2680 hardware, and in virtualized environment.
2682 turbografx.map[2|3]= [HW,JOY]
2683 TurboGraFX parallel port interface
2684 Format:
2685 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2686 See also Documentation/input/joystick-parport.txt
2688 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2689 See header of drivers/scsi/u14-34f.c.
2691 uart401= [HW,OSS]
2692 Format: <io>,<irq>
2694 uart6850= [HW,OSS]
2695 Format: <io>,<irq>
2697 uhash_entries= [KNL,NET]
2698 Set number of hash buckets for UDP/UDP-Lite connections
2700 uhci-hcd.ignore_oc=
2701 [USB] Ignore overcurrent events (default N).
2702 Some badly-designed motherboards generate lots of
2703 bogus events, for ports that aren't wired to
2704 anything. Set this parameter to avoid log spamming.
2705 Note that genuine overcurrent events won't be
2706 reported either.
2708 unknown_nmi_panic
2709 [X86]
2710 Set unknown_nmi_panic=1 early on boot.
2712 usbcore.autosuspend=
2713 [USB] The autosuspend time delay (in seconds) used
2714 for newly-detected USB devices (default 2). This
2715 is the time required before an idle device will be
2716 autosuspended. Devices for which the delay is set
2717 to a negative value won't be autosuspended at all.
2719 usbcore.usbfs_snoop=
2720 [USB] Set to log all usbfs traffic (default 0 = off).
2722 usbcore.blinkenlights=
2723 [USB] Set to cycle leds on hubs (default 0 = off).
2725 usbcore.old_scheme_first=
2726 [USB] Start with the old device initialization
2727 scheme (default 0 = off).
2729 usbcore.use_both_schemes=
2730 [USB] Try the other device initialization scheme
2731 if the first one fails (default 1 = enabled).
2733 usbcore.initial_descriptor_timeout=
2734 [USB] Specifies timeout for the initial 64-byte
2735 USB_REQ_GET_DESCRIPTOR request in milliseconds
2736 (default 5000 = 5.0 seconds).
2738 usbhid.mousepoll=
2739 [USBHID] The interval which mice are to be polled at.
2741 usb-storage.delay_use=
2742 [UMS] The delay in seconds before a new device is
2743 scanned for Logical Units (default 5).
2745 usb-storage.quirks=
2746 [UMS] A list of quirks entries to supplement or
2747 override the built-in unusual_devs list. List
2748 entries are separated by commas. Each entry has
2749 the form VID:PID:Flags where VID and PID are Vendor
2750 and Product ID values (4-digit hex numbers) and
2751 Flags is a set of characters, each corresponding
2752 to a common usb-storage quirk flag as follows:
2753 a = SANE_SENSE (collect more than 18 bytes
2754 of sense data);
2755 b = BAD_SENSE (don't collect more than 18
2756 bytes of sense data);
2757 c = FIX_CAPACITY (decrease the reported
2758 device capacity by one sector);
2759 h = CAPACITY_HEURISTICS (decrease the
2760 reported device capacity by one
2761 sector if the number is odd);
2762 i = IGNORE_DEVICE (don't bind to this
2763 device);
2764 l = NOT_LOCKABLE (don't try to lock and
2765 unlock ejectable media);
2766 m = MAX_SECTORS_64 (don't transfer more
2767 than 64 sectors = 32 KB at a time);
2768 o = CAPACITY_OK (accept the capacity
2769 reported by the device);
2770 r = IGNORE_RESIDUE (the device reports
2771 bogus residue values);
2772 s = SINGLE_LUN (the device has only one
2773 Logical Unit);
2774 w = NO_WP_DETECT (don't test whether the
2775 medium is write-protected).
2776 Example: quirks=0419:aaf5:rl,0421:0433:rc
2778 userpte=
2779 [X86] Flags controlling user PTE allocations.
2781 nohigh = do not allocate PTE pages in
2782 HIGHMEM regardless of setting
2783 of CONFIG_HIGHPTE.
2785 vdso= [X86,SH]
2786 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2787 vdso=1: enable VDSO (default)
2788 vdso=0: disable VDSO mapping
2790 vdso32= [X86]
2791 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2792 vdso32=1: enable 32-bit VDSO (default)
2793 vdso32=0: disable 32-bit VDSO mapping
2795 vector= [IA-64,SMP]
2796 vector=percpu: enable percpu vector domain
2798 video= [FB] Frame buffer configuration
2799 See Documentation/fb/modedb.txt.
2801 vga= [BOOT,X86-32] Select a particular video mode
2802 See Documentation/x86/boot.txt and
2803 Documentation/svga.txt.
2804 Use vga=ask for menu.
2805 This is actually a boot loader parameter; the value is
2806 passed to the kernel using a special protocol.
2808 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2809 size of <nn>. This can be used to increase the
2810 minimum size (128MB on x86). It can also be used to
2811 decrease the size and leave more room for directly
2812 mapped kernel RAM.
2814 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2815 Format: <command>
2817 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2818 Format: <command>
2820 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2821 Format: <command>
2823 vt.cur_default= [VT] Default cursor shape.
2824 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2825 the parameters of the <Esc>[?A;B;Cc escape sequence;
2826 see VGA-softcursor.txt. Default: 2 = underline.
2828 vt.default_blu= [VT]
2829 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2830 Change the default blue palette of the console.
2831 This is a 16-member array composed of values
2832 ranging from 0-255.
2834 vt.default_grn= [VT]
2835 Format: <green0>,<green1>,<green2>,...,<green15>
2836 Change the default green palette of the console.
2837 This is a 16-member array composed of values
2838 ranging from 0-255.
2840 vt.default_red= [VT]
2841 Format: <red0>,<red1>,<red2>,...,<red15>
2842 Change the default red palette of the console.
2843 This is a 16-member array composed of values
2844 ranging from 0-255.
2846 vt.default_utf8=
2847 [VT]
2848 Format=<0|1>
2849 Set system-wide default UTF-8 mode for all tty's.
2850 Default is 1, i.e. UTF-8 mode is enabled for all
2851 newly opened terminals.
2853 vt.global_cursor_default=
2854 [VT]
2855 Format=<-1|0|1>
2856 Set system-wide default for whether a cursor
2857 is shown on new VTs. Default is -1,
2858 i.e. cursors will be created by default unless
2859 overridden by individual drivers. 0 will hide
2860 cursors, 1 will display them.
2862 waveartist= [HW,OSS]
2863 Format: <io>,<irq>,<dma>,<dma2>
2865 wd33c93= [HW,SCSI]
2866 See header of drivers/scsi/wd33c93.c.
2868 wd7000= [HW,SCSI]
2869 See header of drivers/scsi/wd7000.c.
2871 watchdog timers [HW,WDT] For information on watchdog timers,
2872 see Documentation/watchdog/watchdog-parameters.txt
2873 or other driver-specific files in the
2874 Documentation/watchdog/ directory.
2876 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2877 default x2apic cluster mode on platforms
2878 supporting x2apic.
2880 x86_mrst_timer= [X86-32,APBT]
2881 Choose timer option for x86 Moorestown MID platform.
2882 Two valid options are apbt timer only and lapic timer
2883 plus one apbt timer for broadcast timer.
2884 x86_mrst_timer=apbt_only | lapic_and_apbt
2886 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2887 xd_geo= See header of drivers/block/xd.c.
2889 xirc2ps_cs= [NET,PCMCIA]
2890 Format:
2891 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2893 ______________________________________________________________________
2895 TODO:
2897 Add documentation for ALSA options.
2898 Add more DRM drivers.