4 The following is a consolidated list of the kernel parameters as implemented
5 (mostly) by the __setup() macro and sorted into English Dictionary order
6 (defined as ignoring all punctuation and sorting digits before letters in a
7 case insensitive manner), and with descriptions where known.
9 Module parameters for loadable modules are specified only as the
10 parameter name with optional '=' and value as appropriate, such as:
12 modprobe usbcore blinkenlights=1
14 Module parameters for modules that are built into the kernel image
15 are specified on the kernel command line with the module name plus
16 '.' plus parameter name, with '=' and value if appropriate, such as:
18 usbcore.blinkenlights=1
20 Hyphens (dashes) and underscores are equivalent in parameter names, so
21 log_buf_len=1M print-fatal-signals=1
22 can also be entered as
23 log-buf-len=1M print_fatal_signals=1
26 This document may not be entirely up to date and comprehensive. The command
27 "modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28 module. Loadable modules, after being loaded into the running kernel, also
29 reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30 parameters may be changed at runtime by the command
31 "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
33 The parameters listed below are only valid if certain kernel build options were
34 enabled and if respective hardware is present. The text in square brackets at
35 the beginning of each description states the restrictions within which a
36 parameter is applicable:
38 ACPI ACPI support is enabled.
39 AGP AGP (Accelerated Graphics Port) is enabled.
40 ALSA ALSA sound support is enabled.
41 APIC APIC support is enabled.
42 APM Advanced Power Management support is enabled.
43 AVR32 AVR32 architecture is enabled.
44 AX25 Appropriate AX.25 support is enabled.
45 BLACKFIN Blackfin architecture is enabled.
46 DRM Direct Rendering Management support is enabled.
47 EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
48 EFI EFI Partitioning (GPT) is enabled
49 EIDE EIDE/ATAPI support is enabled.
50 FB The frame buffer device is enabled.
51 GCOV GCOV profiling is enabled.
52 HW Appropriate hardware is enabled.
53 IA-64 IA-64 architecture is enabled.
54 IMA Integrity measurement architecture is enabled.
55 IOSCHED More than one I/O scheduler is enabled.
56 IP_PNP IP DHCP, BOOTP, or RARP is enabled.
57 IPV6 IPv6 support is enabled.
58 ISAPNP ISA PnP code is enabled.
59 ISDN Appropriate ISDN support is enabled.
60 JOY Appropriate joystick support is enabled.
61 KVM Kernel Virtual Machine support is enabled.
62 LIBATA Libata driver is enabled
63 LP Printer support is enabled.
64 LOOP Loopback device support is enabled.
65 M68k M68k architecture is enabled.
66 These options have more detailed description inside of
67 Documentation/m68k/kernel-options.txt.
68 MCA MCA bus support is enabled.
69 MDA MDA console support is enabled.
70 MOUSE Appropriate mouse support is enabled.
71 MSI Message Signaled Interrupts (PCI).
72 MTD MTD (Memory Technology Device) support is enabled.
73 NET Appropriate network support is enabled.
74 NUMA NUMA support is enabled.
75 GENERIC_TIME The generic timeofday code is enabled.
76 NFS Appropriate NFS support is enabled.
77 OSS OSS sound support is enabled.
78 PV_OPS A paravirtualized kernel is enabled.
79 PARIDE The ParIDE (parallel port IDE) subsystem is enabled.
80 PARISC The PA-RISC architecture is enabled.
81 PCI PCI bus support is enabled.
82 PCIE PCI Express support is enabled.
83 PCMCIA The PCMCIA subsystem is enabled.
84 PNP Plug & Play support is enabled.
85 PPC PowerPC architecture is enabled.
86 PPT Parallel port support is enabled.
87 PS2 Appropriate PS/2 support is enabled.
88 RAM RAM disk support is enabled.
89 S390 S390 architecture is enabled.
90 SCSI Appropriate SCSI support is enabled.
91 A lot of drivers has their options described inside of
93 SECURITY Different security models are enabled.
94 SELINUX SELinux support is enabled.
95 SERIAL Serial support is enabled.
96 SH SuperH architecture is enabled.
97 SMP The kernel is an SMP kernel.
98 SPARC Sparc architecture is enabled.
99 SWSUSP Software suspend (hibernation) is enabled.
100 SUSPEND System suspend states are enabled.
101 FTRACE Function tracing enabled.
102 TPM TPM drivers are enabled.
103 TS Appropriate touchscreen support is enabled.
104 UMS USB Mass Storage support is enabled.
105 USB USB support is enabled.
106 USBHID USB Human Interface Device support is enabled.
107 V4L Video For Linux support is enabled.
108 VGA The VGA console has been enabled.
109 VT Virtual terminal support is enabled.
110 WDT Watchdog support is enabled.
111 XT IBM PC/XT MFM hard disk support is enabled.
112 X86-32 X86-32, aka i386 architecture is enabled.
113 X86-64 X86-64 architecture is enabled.
114 More X86-64 boot options can be found in
115 Documentation/x86/x86_64/boot-options.txt .
116 X86 Either 32bit or 64bit x86 (same as X86-32+X86-64)
118 In addition, the following text indicates that the option:
120 BUGS= Relates to possible processor bugs on the said processor.
121 KNL Is a kernel start-up parameter.
122 BOOT Is a boot loader parameter.
124 Parameters denoted with BOOT are actually interpreted by the boot
125 loader, and have no meaning to the kernel directly.
126 Do not modify the syntax of boot loader parameters without extreme
127 need or coordination with <Documentation/x86/boot.txt>.
129 There are also arch-specific kernel-parameters not documented here.
130 See for example <Documentation/x86/x86_64/boot-options.txt>.
132 Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
133 a trailing = on the name of any parameter states that that parameter will
134 be entered as an environment variable, whereas its absence indicates that
135 it will appear as a kernel argument readable via /proc/cmdline by programs
136 running once the system is up.
138 The number of kernel parameters is not limited, but the length of the
139 complete command line (parameters including spaces etc.) is limited to
140 a fixed number of characters. This limit depends on the architecture
141 and is between 256 and 4096 characters. It is defined in the file
142 ./include/asm/setup.h as COMMAND_LINE_SIZE.
146 Advanced Configuration and Power Interface
147 Format: { force | off | ht | strict | noirq | rsdt }
148 force -- enable ACPI if default was off
149 off -- disable ACPI if default was on
150 noirq -- do not use ACPI for IRQ routing
151 ht -- run only enough ACPI to enable Hyper Threading
152 strict -- Be less tolerant of platforms that are not
153 strictly ACPI specification compliant.
154 rsdt -- prefer RSDT over (default) XSDT
156 See also Documentation/power/pm.txt, pci=noacpi
158 acpi_apic_instance= [ACPI, IOAPIC]
160 2: use 2nd APIC table, if available
161 1,0: use 1st APIC table
164 acpi_backlight= [HW,ACPI]
165 acpi_backlight=vendor
167 If set to vendor, prefer vendor specific driver
168 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
169 of the ACPI video.ko driver.
171 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
172 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
174 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
175 debug output. Bits in debug_layer correspond to a
176 _COMPONENT in an ACPI source file, e.g.,
177 #define _COMPONENT ACPI_PCI_COMPONENT
178 Bits in debug_level correspond to a level in
179 ACPI_DEBUG_PRINT statements, e.g.,
180 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
181 The debug_level mask defaults to "info". See
182 Documentation/acpi/debug.txt for more information about
183 debug layers and levels.
185 Enable processor driver info messages:
186 acpi.debug_layer=0x20000000
187 Enable PCI/PCI interrupt routing info messages:
188 acpi.debug_layer=0x400000
189 Enable AML "Debug" output, i.e., stores to the Debug
190 object while interpreting AML:
191 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
192 Enable all messages related to ACPI hardware:
193 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
195 Some values produce so much output that the system is
196 unusable. The "log_buf_len" parameter may be useful
197 if you need to capture more output.
199 acpi_display_output= [HW,ACPI]
200 acpi_display_output=vendor
201 acpi_display_output=video
204 acpi_early_pdc_eval [HW,ACPI] Evaluate processor _PDC methods
205 early. Needed on some platforms to properly
208 acpi_irq_balance [HW,ACPI]
209 ACPI will balance active IRQs
212 acpi_irq_nobalance [HW,ACPI]
213 ACPI will not move active IRQs (default)
216 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
217 Format: <irq>,<irq>...
219 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
221 Format: <irq>,<irq>...
223 acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT
225 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
226 Format: To spoof as Windows 98: ="Microsoft Windows"
228 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
229 acpi_osi="string1" # add string1 -- only one string
230 acpi_osi="!string2" # remove built-in string2
231 acpi_osi= # disable all strings
234 Override the pmtimer bug detection: force the kernel
235 to assume that this machine's pmtimer latches its value
236 and always returns good values.
238 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
239 Format: { level | edge | high | low }
241 acpi_serialize [HW,ACPI] force serialization of AML methods
243 acpi_skip_timer_override [HW,ACPI]
244 Recognize and ignore IRQ0/pin2 Interrupt Override.
245 For broken nForce2 BIOS resulting in XT-PIC timer.
247 acpi_sleep= [HW,ACPI] Sleep options
248 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
249 old_ordering, s4_nonvs, sci_force_enable }
250 See Documentation/power/video.txt for information on
252 s3_beep is for debugging; it makes the PC's speaker beep
253 as soon as the kernel's real-mode entry point is called.
254 s4_nohwsig prevents ACPI hardware signature from being
255 used during resume from hibernation.
256 old_ordering causes the ACPI 1.0 ordering of the _PTS
257 control method, with respect to putting devices into
258 low power states, to be enforced (the ACPI 2.0 ordering
259 of _PTS is used by default).
260 s4_nonvs prevents the kernel from saving/restoring the
261 ACPI NVS memory during hibernation.
262 sci_force_enable causes the kernel to set SCI_EN directly
263 on resume from S1/S3 (which is against the ACPI spec,
264 but some broken systems don't work without it).
266 acpi_use_timer_override [HW,ACPI]
267 Use timer override. For some broken Nvidia NF5 boards
268 that require a timer override, but don't have HPET
270 acpi_enforce_resources= [ACPI]
271 { strict | lax | no }
272 Check for resource conflicts between native drivers
273 and ACPI OperationRegions (SystemIO and SystemMemory
274 only). IO ports and memory declared in ACPI might be
275 used by the ACPI subsystem in arbitrary AML code and
276 can interfere with legacy drivers.
277 strict (default): access to resources claimed by ACPI
278 is denied; legacy drivers trying to access reserved
279 resources will fail to bind to device using them.
280 lax: access to resources claimed by ACPI is allowed;
281 legacy drivers trying to access reserved resources
282 will bind successfully but a warning message is logged.
283 no: ACPI OperationRegions are not marked as reserved,
284 no further checks are performed.
287 Format: <io>,<irq>,<dma>,<dma2>,<type>
289 add_efi_memmap [EFI; X86] Include EFI memory map in
290 kernel's map of available physical RAM.
293 See header of drivers/scsi/advansys.c.
295 advwdt= [HW,WDT] Advantech WDT
296 Format: <iostart>,<iostop>
298 aedsp16= [HW,OSS] Audio Excel DSP 16
299 Format: <io>,<irq>,<dma>,<mss_io>,<mpu_io>,<mpu_irq>
300 See also header of sound/oss/aedsp16.c.
303 { off | try_unsupported }
304 off: disable AGP support
305 try_unsupported: try to drive unsupported chipsets
306 (may crash computer or cause data corruption)
309 See Documentation/scsi/aha152x.txt.
312 Format: <portbase>[,<buson>,<busoff>[,<dmaspeed>]]
315 See Documentation/scsi/aic7xxx.txt.
318 See Documentation/scsi/aic79xx.txt.
321 Allow the default userspace alignment fault handler
322 behaviour to be specified. Bit 0 enables warnings,
323 bit 1 enables fixups, and bit 2 sends a segfault.
325 amd_iommu= [HW,X86-84]
326 Pass parameters to the AMD IOMMU driver in the system.
328 isolate - enable device isolation (each device, as far
329 as possible, will get its own protection
331 share - put every device behind one IOMMU into the
332 same protection domain
333 fullflush - enable flushing of IO/TLB entries when
334 they are unmapped. Otherwise they are
335 flushed before they will be reused, which
338 amijoy.map= [HW,JOY] Amiga joystick support
339 Map of devices attached to JOY0DAT and JOY1DAT
341 See also Documentation/kernel/input/joystick.txt
343 analog.map= [HW,JOY] Analog joystick and gamepad support
344 Specifies type or capabilities of an analog joystick
345 connected to one of 16 gameports
346 Format: <type1>,<type2>,..<type16>
349 Power management functions (SPARCstation-4/5 + deriv.)
351 Disable APC CPU standby support. SPARCstation-Fox does
352 not play well with APC CPU idle - disable it if you have
353 APC and your system crashes randomly.
355 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
356 Change the output verbosity whilst booting
357 Format: { quiet (default) | verbose | debug }
358 Change the amount of debugging information output
359 when initialising the APIC and IO-APIC components.
362 See Documentation/networking/ipv6.txt.
364 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
365 Limit apic dumping. The parameter defines the maximal
366 number of local apics being dumped. Also it is possible
367 to set it to "all" by meaning -- no limit here.
368 Format: { 1 (default) | 2 | ... | all }.
369 The parameter valid if only apic=debug or
370 apic=verbose is specified.
371 Example: apic=debug show_lapic=all
373 apm= [APM] Advanced Power Management
374 See header of arch/x86/kernel/apm_32.c.
376 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
377 Format: <io>,<irq>,<nodeID>
381 atarimouse= [HW,MOUSE] Atari Mouse
383 atascsi= [HW,SCSI] Atari SCSI
385 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
386 EzKey and similar keyboards
388 atkbd.reset= [HW] Reset keyboard during initialization
390 atkbd.set= [HW] Select keyboard code set
391 Format: <int> (2 = AT (default), 3 = PS/2)
393 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
396 atkbd.softraw= [HW] Choose between synthetic and real raw mode
397 Format: <bool> (0 = real, 1 = synthetic (default))
399 atkbd.softrepeat= [HW]
400 Use software keyboard repeat
404 baycom_epp= [HW,AX25]
407 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
409 See header of drivers/net/hamradio/baycom_par.c.
411 baycom_ser_fdx= [HW,AX25]
412 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
413 Format: <io>,<irq>,<mode>[,<baud>]
414 See header of drivers/net/hamradio/baycom_ser_fdx.c.
416 baycom_ser_hdx= [HW,AX25]
417 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
418 Format: <io>,<irq>,<mode>
419 See header of drivers/net/hamradio/baycom_ser_hdx.c.
421 boot_delay= Milliseconds to delay each printk during boot.
422 Values larger than 10 seconds (10000) are changed to
426 bootmem_debug [KNL] Enable bootmem allocator debug messages.
428 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
429 bttv.radio= Most important insmod options are available as
431 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
432 bttv.tuner= and Documentation/video4linux/bttv/CARDLIST
435 See drivers/scsi/BusLogic.c, comment before function
436 BusLogic_ParseDriverOptions().
438 c101= [NET] Moxa C101 synchronous serial card
440 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
441 Sometimes CPU hardware bugs make them report the cache
442 size incorrectly. The kernel will attempt work arounds
443 to fix known problems, but for some CPUs it is not
444 possible to determine what the correct size should be.
445 This option provides an override for these situations.
448 [SECURITY] Disable capabilities. This would normally
449 be used only if an alternative security model is to be
450 configured. Potentially dangerous and should only be
451 used if you are entirely sure of the consequences.
453 ccw_timeout_log [S390]
454 See Documentation/s390/CommonIO for details.
456 cgroup_disable= [KNL] Disable a particular controller
457 Format: {name of the controller(s) to disable}
458 {Currently supported controllers - "memory"}
460 checkreqprot [SELINUX] Set initial checkreqprot flag value.
461 Format: { "0" | "1" }
462 See security/selinux/Kconfig help text.
463 0 -- check protection applied by kernel (includes
464 any implied execute protection).
465 1 -- check protection requested by application.
466 Default value is set via a kernel config option.
467 Value can be changed at runtime via
468 /selinux/checkreqprot.
471 See Documentation/s390/CommonIO for details.
473 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
475 Forces specified clocksource (if available) to be used
476 when calculating gettimeofday(). If specified
477 clocksource is not available, it defaults to PIT.
478 Format: { pit | tsc | cyclone | pmtmr }
480 clocksource= [GENERIC_TIME] Override the default clocksource
482 Override the default clocksource and use the clocksource
483 with the name specified.
484 Some clocksource names to choose from, depending on
486 [all] jiffies (this is the base, fallback clocksource)
488 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
489 pxa_timer,timer3,32k_counter,timer0_1
491 [X86-32] pit,hpet,tsc,vmi-timer;
492 scx200_hrt on Geode; cyclone on IBM x440
500 clearcpuid=BITNUM [X86]
501 Disable CPUID feature X for the kernel. See
502 arch/x86/include/asm/cpufeature.h for the valid bit
503 numbers. Note the Linux specific bits are not necessarily
504 stable over kernel options, but the vendor specific
506 Also note that user programs calling CPUID directly
507 or using the feature without checking anything
508 will still see it. This just prevents it from
509 being used by the kernel or shown in /proc/cpuinfo.
510 Also note the kernel might malfunction if you disable
513 cmo_free_hint= [PPC] Format: { yes | no }
514 Specify whether pages are marked as being inactive
515 when they are freed. This is used in CMO environments
516 to determine OS memory pressure for page stealing by
520 code_bytes [X86] How many bytes of object code to print
525 com20020= [HW,NET] ARCnet - COM20020 chipset
527 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
529 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
533 ARCnet - COM90xx chipset (memory-mapped buffers)
534 Format: <io>[,<irq>[,<memstart>]]
536 condev= [HW,S390] console device
539 console= [KNL] Output console device and options.
541 tty<n> Use the virtual console device <n>.
545 Use the specified serial port. The options are of
546 the form "bbbbpnf", where "bbbb" is the baud rate,
547 "p" is parity ("n", "o", or "e"), "n" is number of
548 bits, and "f" is flow control ("r" for RTS or
549 omit it). Default is "9600n8".
551 See Documentation/serial-console.txt for more
553 Documentation/networking/netconsole.txt for an
556 uart[8250],io,<addr>[,options]
557 uart[8250],mmio,<addr>[,options]
558 Start an early, polled-mode console on the 8250/16550
559 UART at the specified I/O port or MMIO address,
560 switching to the matching ttyS device later. The
561 options are the same as for ttyS, above.
563 If the device connected to the port is not a TTY but a braille
564 device, prepend "brl," before the device type, for instance
566 For now, only VisioBraille is supported.
568 consoleblank= [KNL] The console blank (screen saver) timeout in
569 seconds. Defaults to 10*60 = 10mins. A value of 0
570 disables the blank timer.
573 [KNL] Change the default value for
574 /proc/<pid>/coredump_filter.
575 See also Documentation/filesystems/proc.txt.
577 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
579 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
581 crashkernel=nn[KMG]@ss[KMG]
582 [KNL] Reserve a chunk of physical memory to
583 hold a kernel to switch to with kexec on panic.
585 crashkernel=range1:size1[,range2:size2,...][@offset]
586 [KNL] Same as above, but depends on the memory
587 in the running system. The syntax of range is
588 start-[end] where start and end are both
589 a memory unit (amount[KMG]). See also
590 Documentation/kdump/kdump.txt for a example.
595 cs89x0_media= [HW,NET]
596 Format: { rj45 | aui | bnc }
599 See header of drivers/s390/block/dasd_devmap.c.
601 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
602 (one device per port)
603 Format: <port#>,<type>
604 See also Documentation/input/joystick-parport.txt
606 debug [KNL] Enable kernel debugging (events log level).
609 [KNL] verbose self-tests
611 Print debugging info while doing the locking API
613 We default to 0 (no extra messages), setting it to
614 1 will print _a lot_ more information - normally
615 only useful to kernel developers.
617 debug_objects [KNL] Enable object debugging
620 [KNL] Disable object debugging
622 debugpat [X86] Enable PAT debugging
624 decnet.addr= [HW,NET]
625 Format: <area>[,<node>]
626 See also Documentation/networking/decnet.txt.
629 [same as hugepagesz=] The size of the default
630 HugeTLB page size. This is the size represented by
631 the legacy /proc/ hugepages APIs, used for SHM, and
632 default size when mounting hugetlbfs filesystems.
633 Defaults to the default architecture's huge page size
637 Set number of hash buckets for dentry cache.
640 IO parameters + enable/disable command.
642 digiepca= [HW,SERIAL]
643 See drivers/char/README.epca and
644 Documentation/serial/digiepca.txt.
647 See Documentation/networking/ipv6.txt.
650 See Documentation/networking/ipv6.txt.
652 disable_mtrr_cleanup [X86]
653 The kernel tries to adjust MTRR layout from continuous
654 to discrete, to make X server driver able to add WB
655 entry later. This parameter disables that.
657 disable_mtrr_trim [X86, Intel and AMD only]
658 By default the kernel will trim any uncacheable
659 memory out of your available memory pool based on
660 MTRR settings. This parameter disables that behavior,
661 possibly causing your machine to run very slowly.
663 disable_timer_pin_1 [X86]
664 Disable PIN 1 of APIC timer
665 Can be useful to work around chipset bugs.
667 dmasound= [HW,OSS] Sound subsystem buffers
669 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
670 this option disables the debugging code at boot.
672 dma_debug_entries=<number>
673 This option allows to tune the number of preallocated
674 entries for DMA-API debugging code. One entry is
675 required per DMA-API allocation. Use this if the
676 DMA-API debugging code disables itself because the
677 architectural default is too low.
679 dma_debug_driver=<driver_name>
680 With this option the DMA-API debugging driver
681 filter feature can be enabled at boot time. Just
682 pass the driver to filter for as the parameter.
683 The filter can be disabled or changed to another
684 driver later using sysfs.
690 dynamic_printk Enables pr_debug()/dev_dbg() calls if
691 CONFIG_DYNAMIC_PRINTK_DEBUG has been enabled.
692 These can also be switched on/off via
693 <debugfs>/dynamic_printk/modules
695 earlycon= [KNL] Output early console device and options.
696 uart[8250],io,<addr>[,options]
697 uart[8250],mmio,<addr>[,options]
698 Start an early, polled-mode console on the 8250/16550
699 UART at the specified I/O port or MMIO address.
700 The options are the same as for ttyS, above.
702 earlyprintk= [X86,SH,BLACKFIN]
704 earlyprintk=serial[,ttySn[,baudrate]]
705 earlyprintk=ttySn[,baudrate]
706 earlyprintk=dbgp[debugController#]
708 Append ",keep" to not disable it when the real console
711 Only vga or serial or usb debug port at a time.
713 Currently only ttyS0 and ttyS1 are supported.
715 Interaction with the standard serial driver is not
718 The VGA output is eventually overwritten by the real
724 Format: {"off" | "on" | "skip[mbr]"}
726 eisa_irq_edge= [PARISC,HW]
727 See header of drivers/parisc/eisa.c.
730 See comment before function elanfreq_setup() in
731 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
734 Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
735 See Documentation/block/as-iosched.txt and
736 Documentation/block/deadline-iosched.txt for details.
738 elfcorehdr= [IA64,PPC,SH,X86]
739 Specifies physical address of start of kernel core
740 image elf header. Generally kexec loader will
741 pass this option to capture kernel.
742 See Documentation/kdump/kdump.txt for details.
744 enable_mtrr_cleanup [X86]
745 The kernel tries to adjust MTRR layout from continuous
746 to discrete, to make X server driver able to add WB
747 entry later. This parameter enables that.
749 enable_timer_pin_1 [X86]
750 Enable PIN 1 of APIC timer
751 Can be useful to work around chipset bugs
752 (in particular on some ATI chipsets).
753 The kernel tries to set a reasonable default.
755 enforcing [SELINUX] Set initial enforcing status.
757 See security/selinux/Kconfig help text.
758 0 -- permissive (log only, no denials).
759 1 -- enforcing (deny and log).
761 Value can be changed at runtime via /selinux/enforce.
763 ether= [HW,NET] Ethernet cards parameters
764 This option is obsoleted by the "netdev=" option, which
765 has equivalent usage. See its documentation for details.
767 eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
772 fail_make_request=[KNL]
773 General fault injection mechanism.
774 Format: <interval>,<probability>,<space>,<times>
775 See also /Documentation/fault-injection/.
778 See header of drivers/scsi/fd_mcs.c.
781 See header of drivers/scsi/fdomain.c.
784 See Documentation/blockdev/floppy.txt.
786 force_pal_cache_flush
787 [IA-64] Avoid check_sal_cache_flush which may hang on
788 buggy SAL_CACHE_FLUSH implementations. Using this
789 parameter will force ia64_sal_cache_flush to call
790 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
793 [FTRACE] will set and start the specified tracer
794 as early as possible in order to facilitate early
798 [FTRACE] will dump the trace buffers on oops.
800 ftrace_filter=[function-list]
801 [FTRACE] Limit the functions traced by the function
802 tracer at boot up. function-list is a comma separated
803 list of functions. This list can be changed at run
804 time by the set_ftrace_filter file in the debugfs
807 ftrace_notrace=[function-list]
808 [FTRACE] Do not trace the functions specified in
809 function-list. This list can be changed at run time
810 by the set_ftrace_notrace file in the debugfs
813 ftrace_graph_filter=[function-list]
814 [FTRACE] Limit the top level callers functions traced
815 by the function graph tracer at boot up.
816 function-list is a comma separated list of functions
817 that can be changed at run time by the
818 set_graph_function file in the debugfs tracing directory.
821 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
822 support via parallel port (up to 5 devices per port)
823 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
824 See also Documentation/input/joystick-parport.txt
828 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
832 gcov_persist= [GCOV] When non-zero (default), profiling data for
833 kernel modules is saved and remains accessible via
834 debugfs, even when the module is unloaded/reloaded.
835 When zero, profiling data is discarded and associated
836 debugfs files are removed at module unload time.
839 See header of drivers/scsi/gdth.c.
841 gpt [EFI] Forces disk with valid GPT signature but
842 invalid Protective MBR to be treated as GPT.
846 hashdist= [KNL,NUMA] Large hashes allocated during boot
847 are distributed across NUMA nodes. Defaults on
848 for 64bit NUMA, off otherwise.
849 Format: 0 | 1 (for off | on)
851 hcl= [IA-64] SGI's Hardware Graph compatibility layer
853 hd= [EIDE] (E)IDE hard drive subsystem geometry
854 Format: <cyl>,<head>,<sect>
856 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
857 size of <nn>. This works even on boxes that have no
858 highmem otherwise. This also works to reduce highmem
859 size on bigger boxes.
861 highres= [KNL] Enable/disable high resolution timer mode.
862 Valid parameters: "on", "off"
866 See Documentation/isdn/README.HiSax.
870 hpet= [X86-32,HPET] option to control HPET usage
871 Format: { enable (default) | disable | force |
873 disable: disable HPET and use PIT instead
874 force: allow force enabled of undocumented chips (ICH4,
876 verbose: show contents of HPET registers during setup
878 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
879 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
880 On x86-64 and powerpc, this option can be specified
881 multiple times interleaved with hugepages= to reserve
882 huge pages of different sizes. Valid pages sizes on
883 x86-64 are 2M (when the CPU supports "pse") and 1G
884 (when the CPU supports the "pdpe1gb" cpuinfo flag)
885 Note that 1GB pages can only be allocated at boot time
886 using hugepages= and not freed afterwards.
888 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
889 terminal devices. Valid values: 0..8
890 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
891 If specified, z/VM IUCV HVC accepts connections
892 from listed z/VM user IDs only.
894 i2c_bus= [HW] Override the default board specific I2C bus speed
895 or register an additional I2C bus that is not
896 registered from board initialization code.
900 i8042.debug [HW] Toggle i8042 debug mode
901 i8042.direct [HW] Put keyboard port into non-translated mode
902 i8042.dumbkbd [HW] Pretend that controller can only read data from
903 keyboard and cannot control its state
904 (Don't attempt to blink the leds)
905 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
906 i8042.nokbd [HW] Don't check/create keyboard port
907 i8042.noloop [HW] Disable the AUX Loopback command while probing
909 i8042.nomux [HW] Don't check presence of an active multiplexing
911 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
914 [HW] Frequency with which keyboard LEDs should blink
915 when kernel panics (default is 0.5 sec)
916 i8042.reset [HW] Reset the controller during init and cleanup
917 i8042.unlock [HW] Unlock (ignore) the keylock
921 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
922 indicates that the driver is running on unsupported
924 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
925 does not match list of supported models.
927 [HW] Report power status in /proc/i8k
928 (disabled by default)
929 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
932 ibmmcascsi= [HW,MCA,SCSI] IBM MicroChannel SCSI adapter
933 See Documentation/mca.txt.
936 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
938 ide-core.nodma= [HW] (E)IDE subsystem
939 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
940 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
941 .cdrom .chs .ignore_cable are additional options
942 See Documentation/ide/ide.txt.
944 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
945 Claim all unknown PCI IDE storage controllers.
948 Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
949 Poll forces a polling idle loop that can slightly
950 improve the performance of waking up a idle CPU, but
951 will use a lot of power and make the system run hot.
953 idle=mwait: On systems which support MONITOR/MWAIT but
954 the kernel chose to not use it because it doesn't save
955 as much power as a normal idle loop, use the
956 MONITOR/MWAIT idle loop anyways. Performance should be
957 the same as idle=poll.
958 idle=halt: Halt is forced to be used for CPU idle.
959 In such case C2/C3 won't be used again.
960 idle=nomwait: Disable mwait for CPU C-states
962 ignore_loglevel [KNL]
963 Ignore loglevel setting - this will print /all/
964 kernel messages to the console. Useful for debugging.
967 Set number of hash buckets for inode cache.
970 Format: { "0" | "1" }
971 0 -- integrity auditing messages. (Default)
972 1 -- enable informational integrity auditing messages.
975 Format: { "sha1" | "md5" }
979 Load a policy which meets the needs of the Trusted
980 Computing Base. This means IMA will measure all
981 programs exec'd, files mmap'd for exec, and all files
982 opened for read by uid=0.
985 See header of drivers/scsi/in2000.c.
989 Run specified binary instead of /sbin/init as init
992 initcall_debug [KNL] Trace initcalls as they are executed. Useful
993 for working out where the kernel is dying during
996 initrd= [BOOT] Specify the location of the initial ramdisk
998 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
1001 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
1003 Enable intel iommu driver.
1005 Disable intel iommu driver.
1006 igfx_off [Default Off]
1007 By default, gfx is mapped as normal device. If a gfx
1008 device has a dedicated DMAR unit, the DMAR unit is
1009 bypassed by not enabling DMAR with this option. In
1010 this case, gfx device will use physical address for
1013 With this option iommu will not optimize to look
1014 for io virtual address below 32 bit forcing dual
1015 address cycle on pci bus for cards supporting greater
1016 than 32 bit addressing. The default is to look
1017 for translation below 32 bit and if not available
1018 then look in the higher range.
1019 strict [Default Off]
1020 With this option on every unmap_single operation will
1021 result in a hardware IOTLB flush operation as opposed
1022 to batching them for performance.
1026 iomem= Disable strict checking of access to MMIO memory
1027 strict regions from userspace.
1043 io7= [HW] IO7 for Marvel based alpha systems
1044 See comment before marvel_specify_io7 in
1045 arch/alpha/kernel/core_marvel.c.
1047 io_delay= [X86] I/O delay method
1049 Standard port 0x80 based delay
1051 Alternate port 0xed based delay (needed on some systems)
1053 Simple two microseconds delay
1058 See Documentation/filesystems/nfs/nfsroot.txt.
1060 ip2= [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1061 See comment before ip2_setup() in
1062 drivers/char/ip2/ip2base.c.
1064 ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
1065 See header of drivers/scsi/ips.c.
1068 When an interrupt is not handled search all handlers
1069 for it. Intended to get systems with badly broken
1073 When an interrupt is not handled search all handlers
1074 for it. Also check all handlers each timer
1075 interrupt. Intended to get systems with badly broken
1079 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1081 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
1083 <cpu number>,...,<cpu number>
1085 <cpu number>-<cpu number>
1086 (must be a positive range in ascending order)
1088 <cpu number>,...,<cpu number>-<cpu number>
1090 This option can be used to specify one or more CPUs
1091 to isolate from the general SMP balancing and scheduling
1092 algorithms. You can move a process onto or off an
1093 "isolated" CPU via the CPU affinity syscalls or cpuset.
1094 <cpu number> begins at 0 and the maximum value is
1095 "number of CPUs in system - 1".
1097 This option is the preferred way to isolate CPUs. The
1098 alternative -- manually setting the CPU mask of all
1099 tasks in the system -- can cause problems and
1100 suboptimal load balancer performance.
1104 js= [HW,JOY] Analog joystick
1105 See Documentation/input/joystick.txt.
1109 kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1110 specifies the amount of memory usable by the kernel
1111 for non-movable allocations. The requested amount is
1112 spread evenly throughout all nodes in the system. The
1113 remaining memory in each node is used for Movable
1114 pages. In the event, a node is too small to have both
1115 kernelcore and Movable pages, kernelcore pages will
1116 take priority and other nodes will have a larger number
1117 of kernelcore pages. The Movable zone is used for the
1118 allocation of pages that may be reclaimed or moved
1119 by the page migration subsystem. This means that
1120 HugeTLB pages may not be allocated from this zone.
1121 Note that allocations like PTEs-from-HighMem still
1122 use the HighMem zone if it exists, and the Normal
1123 zone if it does not.
1125 kgdboc= [HW] kgdb over consoles.
1126 Requires a tty driver that supports console polling.
1127 (only serial supported for now)
1128 Format: <serial_device>[,baud]
1130 kmac= [MIPS] korina ethernet MAC address.
1131 Configure the RouterBoard 532 series on-chip
1132 Ethernet adapter MAC address.
1134 kmemleak= [KNL] Boot-time kmemleak enable/disable
1135 Valid arguments: on, off
1138 kstack=N [X86] Print N words from the kernel stack
1141 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1142 Default is 0 (don't ignore, but inject #GP)
1144 kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
1145 Default is 1 (enabled)
1147 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1150 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
1152 Default is 1 (enabled) if in 64bit or 32bit-PAE mode
1154 kvm-intel.bypass_guest_pf=
1155 [KVM,Intel] Disables bypassing of guest page faults
1156 on Intel chips. Default is 1 (enabled)
1158 kvm-intel.ept= [KVM,Intel] Disable extended page tables
1159 (virtualized MMU) support on capable Intel chips.
1160 Default is 1 (enabled)
1162 kvm-intel.emulate_invalid_guest_state=
1163 [KVM,Intel] Enable emulation of invalid guest states
1164 Default is 0 (disabled)
1166 kvm-intel.flexpriority=
1167 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1168 Default is 1 (enabled)
1170 kvm-intel.unrestricted_guest=
1171 [KVM,Intel] Disable unrestricted guest feature
1172 (virtualized real and unpaged mode) on capable
1173 Intel chips. Default is 1 (enabled)
1175 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1176 feature (tagged TLBs) on capable Intel chips.
1177 Default is 1 (enabled)
1183 lapic [X86-32,APIC] Enable the local APIC even if BIOS
1186 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
1189 libata.dma= [LIBATA] DMA control
1190 libata.dma=0 Disable all PATA and SATA DMA
1191 libata.dma=1 PATA and SATA Disk DMA only
1192 libata.dma=2 ATAPI (CDROM) DMA only
1193 libata.dma=4 Compact Flash DMA only
1194 Combinations also work, so libata.dma=3 enables DMA
1195 for disks and CDROMs, but not CFs.
1197 libata.ignore_hpa= [LIBATA] Ignore HPA limit
1198 libata.ignore_hpa=0 keep BIOS limits (default)
1199 libata.ignore_hpa=1 ignore limits, using full disk
1201 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
1205 libata.force= [LIBATA] Force configurations. The format is comma
1206 separated list of "[ID:]VAL" where ID is
1207 PORT[:DEVICE]. PORT and DEVICE are decimal numbers
1208 matching port, link or device. Basically, it matches
1209 the ATA ID string printed on console by libata. If
1210 the whole ID part is omitted, the last PORT and DEVICE
1211 values are used. If ID hasn't been specified yet, the
1212 configuration applies to all ports, links and devices.
1214 If only DEVICE is omitted, the parameter applies to
1215 the port and all links and devices behind it. DEVICE
1216 number of 0 either selects the first device or the
1217 first fan-out link behind PMP device. It does not
1218 select the host link. DEVICE number of 15 selects the
1219 host link and device attached to it.
1221 The VAL specifies the configuration to force. As long
1222 as there's no ambiguity shortcut notation is allowed.
1223 For example, both 1.5 and 1.5G would work for 1.5Gbps.
1224 The following configurations can be forced.
1226 * Cable type: 40c, 80c, short40c, unk, ign or sata.
1227 Any ID with matching PORT is used.
1229 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1231 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1232 udma[/][16,25,33,44,66,100,133] notation is also
1235 * [no]ncq: Turn on or off NCQ.
1237 * nohrst, nosrst, norst: suppress hard, soft
1240 If there are multiple matching configurations changing
1241 the same attribute, the last one is used.
1243 lmb=debug [KNL] Enable lmb debug messages.
1245 load_ramdisk= [RAM] List of ramdisks to load from floppy
1246 See Documentation/blockdev/ramdisk.txt.
1248 lockd.nlm_grace_period=P [NFS] Assign grace period.
1251 lockd.nlm_tcpport=N [NFS] Assign TCP port.
1254 lockd.nlm_timeout=T [NFS] Assign timeout value.
1257 lockd.nlm_udpport=M [NFS] Assign UDP port.
1260 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
1263 loglevel= All Kernel Messages with a loglevel smaller than the
1264 console loglevel will be printed to the console. It can
1265 also be changed with klogd or other programs. The
1266 loglevels are defined as follows:
1268 0 (KERN_EMERG) system is unusable
1269 1 (KERN_ALERT) action must be taken immediately
1270 2 (KERN_CRIT) critical conditions
1271 3 (KERN_ERR) error conditions
1272 4 (KERN_WARNING) warning conditions
1273 5 (KERN_NOTICE) normal but significant condition
1274 6 (KERN_INFO) informational
1275 7 (KERN_DEBUG) debug-level messages
1277 log_buf_len=n Sets the size of the printk ring buffer, in bytes.
1278 Format: { n | nk | nM }
1279 n must be a power of two. The default size
1280 is set in the kernel config file.
1282 logo.nologo [FB] Disables display of the built-in Linux logo.
1283 This may be used to provide more screen space for
1284 kernel log messages and is useful when debugging
1285 kernel boot problems.
1287 lp=0 [LP] Specify parallel ports to use, e.g,
1288 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
1289 lp=reset first parallel port). 'lp=0' disables the
1290 lp=auto printer driver. 'lp=reset' (which can be
1291 specified in addition to the ports) causes
1292 attached printers to be reset. Using
1293 lp=port1,port2,... specifies the parallel ports
1294 to associate lp devices with, starting with
1295 lp0. A port specification may be 'none' to skip
1296 that lp device, or a parport name such as
1297 'parport0'. Specifying 'lp=auto' instead of a
1298 port specification list means that device IDs
1299 from each port should be examined, to see if
1300 an IEEE 1284-compliant printer is attached; if
1301 so, the driver will manage that printer.
1302 See also header of drivers/char/lp.c.
1305 Sets loops_per_jiffy to given constant, thus avoiding
1306 time-consuming boot-time autodetection (up to 250 ms per
1307 CPU). 0 enables autodetection (default). To determine
1308 the correct value for your kernel, boot with normal
1309 autodetection and see what value is printed. Note that
1310 on SMP systems the preset will be applied to all CPUs,
1311 which is likely to cause problems if your CPUs need
1312 significantly divergent settings. An incorrect value
1313 will cause delays in the kernel to be wrong, leading to
1314 unpredictable I/O errors and other breakage. Although
1315 unlikely, in the extreme case this might damage your
1319 Format: <io>,<irq>,<dma>
1321 mac5380= [HW,SCSI] Format:
1322 <can_queue>,<cmd_per_lun>,<sg_tablesize>,<hostid>,<use_tags>
1324 machvec= [IA64] Force the use of a particular machine-vector
1325 (machvec) in a generic kernel.
1326 Example: machvec=hpzx1_swiotlb
1328 machtype= [Loongson] Share the same kernel image file between different
1330 Example: machtype=lemote-yeeloong-2f-7inch
1332 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
1333 than or equal to this physical address is ignored.
1335 maxcpus= [SMP] Maximum number of processors that an SMP kernel
1336 should make use of. maxcpus=n : n >= 0 limits the
1337 kernel to using 'n' processors. n=0 is a special case,
1338 it is equivalent to "nosmp", which also disables
1341 max_loop= [LOOP] Maximum number of loopback devices that can
1345 max_luns= [SCSI] Maximum number of LUNs to probe.
1346 Should be between 1 and 2^32-1.
1349 [SCSI] Maximum number of LUNs received.
1350 Should be between 1 and 16384.
1354 mce [X86-32] Machine Check Exception
1356 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
1358 md= [HW] RAID subsystems devices and level
1359 See Documentation/md.txt.
1362 Format: <first>,<last>
1363 Specifies range of consoles to be captured by the MDA.
1365 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
1366 Amount of memory to be used when the kernel is not able
1367 to see the whole system memory or for test.
1368 [X86-32] Use together with memmap= to avoid physical
1369 address space collisions. Without memmap= PCI devices
1370 could be placed at addresses belonging to unused RAM.
1372 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
1376 [KNL,SH] Allow user to override the default size for
1377 per-device physically contiguous DMA buffers.
1379 memmap=exactmap [KNL,X86] Enable setting of an exact
1380 E820 memory map, as specified by the user.
1381 Such memmap=exactmap lines can be constructed based on
1382 BIOS output or other requirements. See the memmap=nn@ss
1385 memmap=nn[KMG]@ss[KMG]
1386 [KNL] Force usage of a specific region of memory
1387 Region of memory to be used, from ss to ss+nn.
1389 memmap=nn[KMG]#ss[KMG]
1390 [KNL,ACPI] Mark specific memory as ACPI data.
1391 Region of memory to be used, from ss to ss+nn.
1393 memmap=nn[KMG]$ss[KMG]
1394 [KNL,ACPI] Mark specific memory as reserved.
1395 Region of memory to be used, from ss to ss+nn.
1396 Example: Exclude memory from 0x18690000-0x1869ffff
1397 memmap=64K$0x18690000
1399 memmap=0x10000$0x18690000
1401 memory_corruption_check=0/1 [X86]
1402 Some BIOSes seem to corrupt the first 64k of
1403 memory when doing things like suspend/resume.
1404 Setting this option will scan the memory
1405 looking for corruption. Enabling this will
1406 both detect corruption and prevent the kernel
1407 from using the memory being corrupted.
1408 However, its intended as a diagnostic tool; if
1409 repeatable BIOS-originated corruption always
1410 affects the same memory, you can use memmap=
1411 to prevent the kernel from using that memory.
1413 memory_corruption_check_size=size [X86]
1414 By default it checks for corruption in the low
1415 64k, making this memory unavailable for normal
1416 use. Use this parameter to scan for
1417 corruption in more or less memory.
1419 memory_corruption_check_period=seconds [X86]
1420 By default it checks for corruption every 60
1421 seconds. Use this parameter to check at some
1422 other rate. 0 disables periodic checking.
1424 memtest= [KNL,X86] Enable memtest
1426 default : 0 <disable>
1427 Specifies the number of memtest passes to be
1428 performed. Each pass selects another test
1429 pattern from a given set of patterns. Memtest
1430 fills the memory with this pattern, validates
1431 memory contents and reserves bad memory
1432 regions that are detected.
1434 meye.*= [HW] Set MotionEye Camera parameters
1435 See Documentation/video4linux/meye.txt.
1437 mfgpt_irq= [IA-32] Specify the IRQ to use for the
1438 Multi-Function General Purpose Timers on AMD Geode
1441 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
1442 the BIOS has incorrectly applied a workaround. TinyBIOS
1443 version 0.98 is known to be affected, 0.99 fixes the
1444 problem by letting the user disable the workaround.
1448 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
1449 physical address is ignored.
1451 mini2440= [ARM,HW,KNL]
1452 Format:[0..2][b][c][t]
1454 MINI2440 configuration specification:
1455 0 - The attached screen is the 3.5" TFT
1456 1 - The attached screen is the 7" TFT
1457 2 - The VGA Shield is attached (1024x768)
1458 Leaving out the screen size parameter will not load
1459 the TFT driver, and the framebuffer will be left
1461 b - Enable backlight. The TFT backlight pin will be
1462 linked to the kernel VESA blanking code and a GPIO
1463 LED. This parameter is not necessary when using the
1465 c - Enable the s3c camera interface.
1466 t - Reserved for enabling touchscreen support. The
1467 touchscreen support is not enabled in the mainstream
1468 kernel as of 2.6.30, a preliminary port can be found
1469 in the "bleeding edge" mini2440 support kernel at
1470 http://repo.or.cz/w/linux-2.6/mini2440.git
1473 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1474 parameter allows control of the logging verbosity for
1475 the additional memory initialisation checks. A value
1476 of 0 disables mminit logging and a level of 4 will
1477 log everything. Information is printed at KERN_DEBUG
1478 so loglevel=8 may also need to be specified.
1481 [MOUSE] Maximum time between finger touching and
1482 leaving touchpad surface for touch to be considered
1483 a tap and be reported as a left button click (for
1484 touchpads working in absolute mode only).
1486 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
1487 reporting absolute coordinates, such as tablets
1488 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
1489 reporting absolute coordinates, such as tablets
1491 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
1492 is similar to kernelcore except it specifies the
1493 amount of memory used for migratable allocations.
1494 If both kernelcore and movablecore is specified,
1495 then kernelcore will be at *least* the specified
1496 value but may be more. If movablecore on its own
1497 is specified, the administrator must be careful
1498 that the amount of memory usable for all allocations
1504 MTD_Partition= [MTD]
1505 Format: <name>,<region-number>,<size>,<offset>
1507 MTD_Region= [MTD] Format:
1508 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1511 See drivers/mtd/cmdlinepart.c.
1513 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
1515 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1517 boundary - index of last SLC block on Flex-OneNAND.
1518 The remaining blocks are configured as MLC blocks.
1519 lock - Configure if Flex-OneNAND boundary should be locked.
1520 Once locked, the boundary cannot be changed.
1521 1 indicates lock status, 0 indicates unlock status.
1524 ARM/S3C2412 JIVE boot control
1526 See arch/arm/mach-s3c2412/mach-jive.c
1528 mtouchusb.raw_coordinates=
1529 [HW] Make the MicroTouch USB driver use raw coordinates
1530 ('y', default) or cooked coordinates ('n')
1532 mtrr_chunk_size=nn[KMG] [X86]
1533 used for mtrr cleanup. It is largest continuous chunk
1534 that could hold holes aka. UC entries.
1536 mtrr_gran_size=nn[KMG] [X86]
1537 Used for mtrr cleanup. It is granularity of mtrr block.
1539 Large value could prevent small alignment from
1542 mtrr_spare_reg_nr=n [X86]
1544 Range: 0,7 : spare reg number
1546 Used for mtrr cleanup. It is spare mtrr entries number.
1547 Set to 2 or more if your graphical card needs more.
1549 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
1552 See header of drivers/scsi/NCR_D700.c.
1556 ncr53c400= [HW,SCSI]
1558 ncr53c400a= [HW,SCSI]
1560 ncr53c406a= [HW,SCSI]
1562 ncr53c8xx= [HW,SCSI]
1564 netdev= [NET] Network devices parameters
1565 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1566 Note that mem_start is often overloaded to mean
1567 something different and driver-specific.
1568 This usage is only documented in each driver source
1572 [NETFILTER] Enable connection tracking flow accounting
1573 0 to disable accounting
1574 1 to enable accounting
1575 Default value depends on CONFIG_NF_CT_ACCT that is
1576 going to be removed in 2.6.29.
1579 See Documentation/filesystems/nfs/nfsroot.txt.
1581 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
1582 See Documentation/filesystems/nfs/nfsroot.txt.
1584 nfs.callback_tcpport=
1585 [NFS] set the TCP port on which the NFSv4 callback
1586 channel should listen.
1589 [NFS] sets the pathname to the program which is used
1590 to update the NFS client cache entries.
1592 nfs.cache_getent_timeout=
1593 [NFS] sets the timeout after which an attempt to
1594 update a cache entry is deemed to have failed.
1596 nfs.idmap_cache_timeout=
1597 [NFS] set the maximum lifetime for idmapper cache
1601 [NFS] enable 64-bit inode numbers.
1602 If zero, the NFS client will fake up a 32-bit inode
1603 number for the readdir() and stat() syscalls instead
1604 of returning the full 64-bit number.
1605 The default is to return 64-bit inode numbers.
1607 nmi_debug= [KNL,AVR32,SH] Specify one or more actions to take
1608 when a NMI is triggered.
1609 Format: [state][,regs][,debounce][,die]
1611 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
1612 Format: [panic,][num]
1614 0 - turn nmi_watchdog off
1615 1 - use the IO-APIC timer for the NMI watchdog
1616 2 - use the local APIC for the NMI watchdog using
1617 a performance counter. Note: This will use one
1618 performance counter and the local APIC's performance
1620 When panic is specified, panic when an NMI watchdog
1622 This is useful when you use a panic=... timeout and
1623 need the box quickly up again.
1624 Instead of 1 and 2 it is possible to use the following
1625 symbolic names: lapic and ioapic
1626 Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
1628 netpoll.carrier_timeout=
1629 [NET] Specifies amount of time (in seconds) that
1630 netpoll should wait for a carrier. By default netpoll
1633 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
1634 emulation library even if a 387 maths coprocessor
1638 [HW] Never suspend the console
1639 Disable suspending of consoles during suspend and
1640 hibernate operations. Once disabled, debugging
1641 messages can reach various consoles while the rest
1642 of the system is being put to sleep (ie, while
1643 debugging driver suspend/resume hooks). This may
1644 not work reliably with all consoles, but is known
1645 to work with serial and VGA consoles.
1647 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
1648 caches in the slab allocator. Saves per-node memory,
1649 but will impact performance.
1653 noapic [SMP,APIC] Tells the kernel to not make use of any
1654 IOAPICs that may be present in the system.
1656 nobats [PPC] Do not use BATs for mapping kernel lowmem
1657 on "Classic" PPC cores.
1661 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
1663 nodelayacct [KNL] Disable per-task delay accounting
1665 nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
1667 nodsp [SH] Disable hardware DSP at boot time.
1669 noefi [X86] Disable EFI runtime services support.
1674 On X86-32 available only on PAE configured kernels.
1675 noexec=on: enable non-executable mappings (default)
1676 noexec=off: disable non-executable mappings
1679 This affects only 32-bit executables.
1680 noexec32=on: enable non-executable mappings (default)
1681 read doesn't imply executable mappings
1682 noexec32=off: disable non-executable mappings
1683 read implies executable mappings
1685 nofpu [SH] Disable hardware FPU at boot time.
1687 nofxsr [BUGS=X86-32] Disables x86 floating point extended
1688 register save and restore. The kernel will only save
1689 legacy floating-point registers on task switch.
1691 noxsave [BUGS=X86] Disables x86 extended register state save
1692 and restore using xsave. The kernel will fallback to
1693 enabling legacy floating-point and sse state.
1695 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1696 wfi(ARM) instruction doesn't work correctly and not to
1697 use it. This is also useful when using JTAG debugger.
1699 no-hlt [BUGS=X86-32] Tells the kernel that the hlt
1700 instruction doesn't work correctly and not to
1703 no_file_caps Tells the kernel not to honor file capabilities. The
1704 only way then for a file to be executed with privilege
1705 is to be setuid root or executed by root.
1707 nohalt [IA-64] Tells the kernel not to use the power saving
1708 function PAL_HALT_LIGHT when idle. This increases
1709 power-consumption. On the positive side, it reduces
1710 interrupt wake-up latency, which may improve performance
1711 in certain environments such as networked servers or
1714 nohz= [KNL] Boottime enable/disable dynamic ticks
1715 Valid arguments: on, off
1718 noiotrap [SH] Disables trapped I/O port accesses.
1720 noirqdebug [X86-32] Disables the code which attempts to detect and
1721 disable unhandled interrupt sources.
1723 no_timer_check [X86,APIC] Disables the code which tests for
1724 broken timer IRQ sources.
1726 noisapnp [ISAPNP] Disables ISA PnP code.
1728 noinitrd [RAM] Tells the kernel not to load any configured
1731 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
1736 nojitter [IA64] Disables jitter checking for ITC timers.
1738 nolapic [X86-32,APIC] Do not enable or use the local APIC.
1740 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
1742 noltlbs [PPC] Do not use large page/tlb entries for kernel
1743 lowmem mapping on PPC40x.
1745 nomca [IA-64] Disable machine check abort handling
1747 nomce [X86-32] Machine Check Exception
1749 nomfgpt [X86-32] Disable Multi-Function General Purpose
1750 Timer usage (for AMD Geode machines).
1752 nopat [X86] Disable PAT (page attribute table extension of
1753 pagetables) support.
1755 norandmaps Don't use address space randomization. Equivalent to
1756 echo 0 > /proc/sys/kernel/randomize_va_space
1758 noreplace-paravirt [X86-32,PV_OPS] Don't patch paravirt_ops
1760 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
1761 with UP alternatives
1763 noresidual [PPC] Don't use residual data on PReP machines.
1765 noresume [SWSUSP] Disables resume and restores original swap
1768 no-scroll [VGA] Disables scrollback.
1769 This is required for the Braillex ib80-piezo Braille
1770 reader made by F.H. Papenmeier (Germany).
1774 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1776 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
1777 and disable the IO APIC. legacy for "maxcpus=0".
1779 nosoftlockup [KNL] Disable the soft-lockup detector.
1781 noswapaccount [KNL] Disable accounting of swap in memory resource
1782 controller. (See Documentation/cgroups/memory.txt)
1784 nosync [HW,M68K] Disables sync negotiation for all devices.
1786 notsc [BUGS=X86-32] Disable Time Stamp Counter
1788 nousb [USB] Disable the USB subsystem
1792 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
1794 nptcg= [IA64] Override max number of concurrent global TLB
1795 purges which is reported from either PAL_VM_SUMMARY or
1798 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
1799 could support. nr_cpus=n : n >= 1 limits the kernel to
1800 supporting 'n' processors. Later in runtime you can not
1801 use hotplug cpu feature to put more cpu back to online.
1802 just like you compile the kernel NR_CPUS=n
1804 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
1806 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1807 one of ['zone', 'node', 'default'] can be specified
1808 This can be set from sysctl after boot.
1809 See Documentation/sysctl/vm.txt for details.
1811 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
1812 See Documentation/debugging-via-ohci1394.txt for more
1815 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1816 Rather than timing out after 20 ms if an EC
1817 command is not properly ACKed, override the length
1818 of the timeout. We have interrupts disabled while
1819 waiting for the ACK, so if this is set too high
1820 interrupts *may* be lost!
1822 omap_mux= [OMAP] Override bootloader pin multiplexing.
1823 Format: <mux_mode0.mode_name=value>...
1824 For example, to override I2C bus2:
1825 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1830 oprofile.timer= [HW]
1831 Use timer interrupt instead of performance counters
1833 oprofile.cpu_type= Force an oprofile cpu type
1834 This might be useful if you have an older oprofile
1835 userland or if you want common events.
1836 Format: { arch_perfmon }
1837 arch_perfmon: [X86] Force use of architectural
1838 perfmon on Intel CPUs instead of the
1839 CPU specific event set.
1841 osst= [HW,SCSI] SCSI Tape Driver
1842 Format: <buffer_size>,<write_threshold>
1843 See also Documentation/scsi/st.txt.
1845 panic= [KNL] Kernel behaviour on panic
1848 parkbd.port= [HW] Parallel port number the keyboard adapter is
1849 connected to, default is 0.
1851 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
1852 0 for XT, 1 for AT (default is AT).
1855 parport= [HW,PPT] Specify parallel ports. 0 disables.
1856 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
1857 Use 'auto' to force the driver to use any
1858 IRQ/DMA settings detected (the default is to
1859 ignore detected IRQ/DMA settings because of
1860 possible conflicts). You can specify the base
1861 address, IRQ, and DMA settings; IRQ and DMA
1862 should be numbers, or 'auto' (for using detected
1863 settings on that particular port), or 'nofifo'
1864 (to avoid using a FIFO even if it is detected).
1865 Parallel ports are assigned in the order they
1866 are specified on the command line, starting
1869 parport_init_mode= [HW,PPT]
1870 Configure VIA parallel port to operate in
1871 a specific mode. This is necessary on Pegasos
1872 computer where firmware has no options for setting
1873 up parallel port mode and sets it to spp.
1874 Currently this function knows 686a and 8231 chips.
1875 Format: [spp|ps2|epp|ecp|ecpepp]
1877 pas2= [HW,OSS] Format:
1878 <io>,<irq>,<dma>,<dma16>,<sb_io>,<sb_irq>,<sb_dma>,<sb_dma16>
1881 See header of drivers/scsi/pas16.c.
1884 Halt all CPUs after the first oops has been printed for
1885 the specified number of seconds. This is to be used if
1886 your oopses keep scrolling off the screen.
1891 See header of drivers/block/paride/pcd.c.
1892 See also Documentation/blockdev/paride.txt.
1894 pci=option[,option...] [PCI] various PCI subsystem options:
1895 earlydump [X86] dump PCI config space before the kernel
1897 off [X86] don't probe for the PCI bus
1898 bios [X86-32] force use of PCI BIOS, don't access
1899 the hardware directly. Use this if your machine
1900 has a non-standard PCI host bridge.
1901 nobios [X86-32] disallow use of PCI BIOS, only direct
1902 hardware access methods are allowed. Use this
1903 if you experience crashes upon bootup and you
1904 suspect they are caused by the BIOS.
1905 conf1 [X86] Force use of PCI Configuration
1907 conf2 [X86] Force use of PCI Configuration
1909 noaer [PCIE] If the PCIEAER kernel config parameter is
1910 enabled, this kernel boot option can be used to
1911 disable the use of PCIE advanced error reporting.
1912 nodomains [PCI] Disable support for multiple PCI
1913 root domains (aka PCI segments, in ACPI-speak).
1914 nommconf [X86] Disable use of MMCONFIG for PCI
1916 check_enable_amd_mmconf [X86] check for and enable
1917 properly configured MMIO access to PCI
1918 config space on AMD family 10h CPU
1919 nomsi [MSI] If the PCI_MSI kernel config parameter is
1920 enabled, this kernel boot option can be used to
1921 disable the use of MSI interrupts system-wide.
1922 noioapicquirk [APIC] Disable all boot interrupt quirks.
1923 Safety option to keep boot IRQs enabled. This
1924 should never be necessary.
1925 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
1926 primary IO-APIC for bridges that cannot disable
1927 boot IRQs. This fixes a source of spurious IRQs
1928 when the system masks IRQs.
1929 noioapicreroute [APIC] Disable workaround that uses the
1930 boot IRQ equivalent of an IRQ that connects to
1931 a chipset where boot IRQs cannot be disabled.
1932 The opposite of ioapicreroute.
1933 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
1934 routing table. These calls are known to be buggy
1935 on several machines and they hang the machine
1936 when used, but on other computers it's the only
1937 way to get the interrupt routing table. Try
1938 this option if the kernel is unable to allocate
1939 IRQs or discover secondary PCI buses on your
1941 rom [X86] Assign address space to expansion ROMs.
1942 Use with caution as certain devices share
1943 address decoders between ROMs and other
1945 norom [X86] Do not assign address space to
1946 expansion ROMs that do not already have
1947 BIOS assigned address ranges.
1948 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
1949 assigned automatically to PCI devices. You can
1950 make the kernel exclude IRQs of your ISA cards
1952 pirqaddr=0xAAAAA [X86] Specify the physical address
1953 of the PIRQ table (normally generated
1954 by the BIOS) if it is outside the
1955 F0000h-100000h range.
1956 lastbus=N [X86] Scan all buses thru bus #N. Can be
1957 useful if the kernel is unable to find your
1958 secondary buses and you want to tell it
1959 explicitly which ones they are.
1960 assign-busses [X86] Always assign all PCI bus
1961 numbers ourselves, overriding
1962 whatever the firmware may have done.
1963 usepirqmask [X86] Honor the possible IRQ mask stored
1964 in the BIOS $PIR table. This is needed on
1965 some systems with broken BIOSes, notably
1966 some HP Pavilion N5400 and Omnibook XE3
1967 notebooks. This will have no effect if ACPI
1968 IRQ routing is enabled.
1969 noacpi [X86] Do not use ACPI for IRQ routing
1970 or for PCI scanning.
1971 use_crs [X86] Use PCI host bridge window information
1972 from ACPI. On BIOSes from 2008 or later, this
1973 is enabled by default. If you need to use this,
1974 please report a bug.
1975 nocrs [X86] Ignore PCI host bridge windows from ACPI.
1976 If you need to use this, please report a bug.
1977 routeirq Do IRQ routing for all PCI devices.
1978 This is normally done in pci_enable_device(),
1979 so this option is a temporary workaround
1980 for broken drivers that don't call it.
1981 skip_isa_align [X86] do not align io start addr, so can
1982 handle more pci cards
1983 firmware [ARM] Do not re-enumerate the bus but instead
1984 just use the configuration from the
1985 bootloader. This is currently used on
1986 IXP2000 systems where the bus has to be
1987 configured a certain way for adjunct CPUs.
1988 noearly [X86] Don't do any early type 1 scanning.
1989 This might help on some broken boards which
1990 machine check when some devices' config space
1991 is read. But various workarounds are disabled
1992 and some IOMMU drivers will not work.
1993 bfsort Sort PCI devices into breadth-first order.
1994 This sorting is done to get a device
1995 order compatible with older (<= 2.4) kernels.
1996 nobfsort Don't sort PCI devices into breadth-first order.
1997 cbiosize=nn[KMG] The fixed amount of bus space which is
1998 reserved for the CardBus bridge's IO window.
1999 The default value is 256 bytes.
2000 cbmemsize=nn[KMG] The fixed amount of bus space which is
2001 reserved for the CardBus bridge's memory
2002 window. The default value is 64 megabytes.
2005 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2006 Specifies alignment and device to reassign
2007 aligned memory resources.
2008 If <order of align> is not specified,
2009 PAGE_SIZE is used as alignment.
2010 PCI-PCI bridge can be specified, if resource
2011 windows need to be expanded.
2012 ecrc= Enable/disable PCIe ECRC (transaction layer
2013 end-to-end CRC checking).
2014 bios: Use BIOS/firmware settings. This is the
2019 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
2022 force Enable ASPM even on devices that claim not to support it.
2023 WARNING: Forcing ASPM on may cause system lockups.
2025 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
2026 off Do not use native PCIe PME signaling.
2027 force Use native PCIe PME signaling even if the BIOS refuses
2028 to allow the kernel to control the relevant PCIe config
2030 nomsi Do not use MSI for native PCIe PME signaling (this makes
2031 all PCIe root ports use INTx for everything).
2033 pcmv= [HW,PCMCIA] BadgePAD 4
2036 See Documentation/blockdev/paride.txt.
2038 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2041 See arch/parisc/kernel/pdc_chassis.c
2043 percpu_alloc= Select which percpu first chunk allocator to use.
2044 Currently supported values are "embed" and "page".
2045 Archs may support subset or none of the selections.
2046 See comments in mm/percpu.c for details on each
2047 allocator. This parameter is primarily for debugging
2048 and performance comparison.
2051 See Documentation/blockdev/paride.txt.
2054 See Documentation/blockdev/paride.txt.
2056 pirq= [SMP,APIC] Manual mp-table setup
2057 See Documentation/x86/i386/IO-APIC.txt.
2059 plip= [PPT,NET] Parallel port network link
2060 Format: { parport<nr> | timid | 0 }
2061 See also Documentation/parport.txt.
2063 pmtmr= [X86] Manual setup of pmtmr I/O Port.
2064 Override pmtimer IOPort with a hex value.
2068 Enable PNP debug messages. This depends on the
2069 CONFIG_PNP_DEBUG_MESSAGES option.
2075 { on | off | curr | res | no-curr | no-res }
2078 [ISAPNP] Exclude IRQs for the autoconfiguration
2081 [ISAPNP] Exclude DMAs for the autoconfiguration
2083 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2084 Ranges are in pairs (I/O port base and size).
2087 [ISAPNP] Exclude memory regions for the
2089 Ranges are in pairs (memory base and size).
2091 ports= [IP_VS_FTP] IPVS ftp helper module
2093 Up to 8 (IP_VS_APP_MAX_PORTS) ports
2095 Format: <port>,<port>....
2097 print-fatal-signals=
2098 [KNL] debug: print fatal signals
2100 If enabled, warn about various signal handling
2101 related application anomalies: too many signals,
2102 too many POSIX.1 timers, fatal signals causing a
2105 If you hit the warning due to signal overflow,
2106 you might want to try "ulimit -i unlimited".
2110 printk.time= Show timing data prefixed to each printk message line
2111 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
2113 processor.max_cstate= [HW,ACPI]
2114 Limit processor to maximum C-state
2115 max_cstate=9 overrides any DMI blacklist limit.
2117 processor.nocst [HW,ACPI]
2118 Ignore the _CST method to determine C-states,
2119 instead using the legacy FADT method
2121 profile= [KNL] Enable kernel profiling via /proc/profile
2122 Format: [schedule,]<number>
2123 Param: "schedule" - profile schedule points.
2124 Param: <number> - step/bucket size as a power of 2 for
2125 statistical time based profiling.
2126 Param: "sleep" - profile D-state sleeping (millisecs).
2127 Requires CONFIG_SCHEDSTATS
2128 Param: "kvm" - profile VM exits.
2130 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2132 See Documentation/blockdev/ramdisk.txt.
2134 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
2135 probe for; one of (bare|imps|exps|lifebook|any).
2136 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
2138 psmouse.resetafter= [HW,MOUSE]
2139 Try to reset the device after so many bad packets
2142 [HW,MOUSE] Set desired mouse resolution, in dpi.
2143 psmouse.smartscroll=
2144 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2145 0 = disabled, 1 = enabled (default).
2147 pss= [HW,OSS] Personal Sound System (ECHO ESC614)
2149 <io>,<mss_io>,<mss_irq>,<mss_dma>,<mpu_io>,<mpu_irq>
2152 See Documentation/blockdev/paride.txt.
2155 [KNL] Number of legacy pty's. Overwrites compiled-in
2158 quiet [KNL] Disable most log messages
2163 See Documentation/md.txt.
2165 ramdisk_blocksize= [RAM]
2166 See Documentation/blockdev/ramdisk.txt.
2168 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
2169 See Documentation/blockdev/ramdisk.txt.
2171 rcupdate.blimit= [KNL,BOOT]
2172 Set maximum number of finished RCU callbacks to process
2175 rcupdate.qhimark= [KNL,BOOT]
2176 Set threshold of queued
2177 RCU callbacks over which batch limiting is disabled.
2179 rcupdate.qlowmark= [KNL,BOOT]
2180 Set threshold of queued RCU callbacks below which
2181 batch limiting is re-enabled.
2185 Run specified binary instead of /init from the ramdisk,
2186 used for early userspace startup. See initrd.
2188 reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2189 Format: <reboot_mode>[,<reboot_mode2>[,...]]
2190 See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2193 [KNL, SMP] Set scheduler's default relax_domain_level.
2194 See Documentation/cgroups/cpusets.txt.
2196 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
2198 reservetop= [X86-32]
2200 Reserves a hole at the top of the kernel virtual
2203 reset_devices [KNL] Force drivers to reset the underlying device
2204 during initialization.
2207 Specify the partition device for software suspend
2209 resume_offset= [SWSUSP]
2210 Specify the offset from the beginning of the partition
2211 given by "resume=" at which the swap header is located,
2212 in <PAGE_SIZE> units (needed only for swap files).
2213 See Documentation/power/swsusp-and-swap-files.txt
2215 retain_initrd [RAM] Keep initrd memory after extraction
2217 rhash_entries= [KNL,NET]
2218 Set number of hash buckets for route cache
2220 riscom8= [HW,SERIAL]
2221 Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2223 ro [KNL] Mount root device read-only on boot
2225 root= [KNL] Root filesystem
2227 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
2228 mount the root filesystem
2230 rootflags= [KNL] Set root filesystem mount option string
2232 rootfstype= [KNL] Set root filesystem type
2234 rootwait [KNL] Wait (indefinitely) for root device to show up.
2235 Useful for devices that are detected asynchronously
2236 (e.g. USB and MMC devices).
2238 rw [KNL] Mount root device read-write on boot
2240 S [KNL] Run init in single mode
2243 See drivers/net/irda/sa1100_ir.c.
2245 sbni= [NET] Granch SBNI12 leased line adapter
2247 sched_debug [KNL] Enables verbose scheduler debug messages.
2249 sc1200wdt= [HW,WDT] SC1200 WDT (watchdog) driver
2250 Format: <io>[,<timeout>[,<isapnp>]]
2252 scsi_debug_*= [SCSI]
2253 See drivers/scsi/scsi_debug.c.
2255 scsi_default_dev_flags=
2256 [SCSI] SCSI default device flags
2259 scsi_dev_flags= [SCSI] Black/white list entry for vendor and model
2260 Format: <vendor>:<model>:<flags>
2261 (flags are integer value)
2263 scsi_logging_level= [SCSI] a bit mask of logging levels
2264 See drivers/scsi/scsi_logging.h for bits. Also
2265 settable via sysctl at dev.scsi.logging_level
2266 (/proc/sys/dev/scsi/logging_level).
2267 There is also a nice 'scsi_logging_level' script in the
2268 S390-tools package, available for download at
2269 http://www-128.ibm.com/developerworks/linux/linux390/s390-tools-1.5.4.html
2271 scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
2272 discovered. async scans them in kernel threads,
2273 allowing boot to proceed. none ignores them, expecting
2274 user space to do the scan.
2276 security= [SECURITY] Choose a security module to enable at boot.
2277 If this boot parameter is not specified, only the first
2278 security module asking for security registration will be
2279 loaded. An invalid security module name will be treated
2280 as if no module has been chosen.
2282 selinux= [SELINUX] Disable or enable SELinux at boot time.
2283 Format: { "0" | "1" }
2284 See security/selinux/Kconfig help text.
2287 Default value is set via kernel config option.
2288 If enabled at boot time, /selinux/disable can be used
2289 later to disable prior to initial policy load.
2291 serialnumber [BUGS=X86-32]
2294 Maximal number of shapers.
2296 show_msr= [x86] show boot-time MSR settings
2297 Format: { <integer> }
2298 Show boot-time (BIOS-initialized) MSR settings.
2299 The parameter means the number of CPUs to show,
2300 for example 1 means boot CPU only.
2303 See header of drivers/scsi/sim710.c.
2310 slub_debug[=options[,slabs]] [MM, SLUB]
2311 Enabling slub_debug allows one to determine the
2312 culprit if slab objects become corrupted. Enabling
2313 slub_debug can create guard zones around objects and
2314 may poison objects when not in use. Also tracks the
2315 last alloc / free. For more information see
2316 Documentation/vm/slub.txt.
2318 slub_max_order= [MM, SLUB]
2319 Determines the maximum allowed order for slabs.
2320 A high setting may cause OOMs due to memory
2321 fragmentation. For more information see
2322 Documentation/vm/slub.txt.
2324 slub_min_objects= [MM, SLUB]
2325 The minimum number of objects per slab. SLUB will
2326 increase the slab order up to slub_max_order to
2327 generate a sufficiently large slab able to contain
2328 the number of objects indicated. The higher the number
2329 of objects the smaller the overhead of tracking slabs
2330 and the less frequently locks need to be acquired.
2331 For more information see Documentation/vm/slub.txt.
2333 slub_min_order= [MM, SLUB]
2334 Determines the mininum page order for slabs. Must be
2335 lower than slub_max_order.
2336 For more information see Documentation/vm/slub.txt.
2338 slub_nomerge [MM, SLUB]
2339 Disable merging of slabs with similar size. May be
2340 necessary if there is some reason to distinguish
2341 allocs to different slabs. Debug options disable
2342 merging on their own.
2343 For more information see Documentation/vm/slub.txt.
2346 Format: <io1>[,<io2>[,...,<io8>]]
2348 smp-alt-once [X86-32,SMP] On a hotplug CPU system, only
2349 attempt to substitute SMP alternatives once at boot.
2351 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
2352 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
2353 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
2354 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
2355 smsc-ircc2.ircc_irq= [HW] IRQ line
2356 smsc-ircc2.ircc_dma= [HW] DMA channel
2357 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2358 0: Toshiba Satellite 1800 (GP data pin select)
2359 1: Fast pin select (default)
2362 snd-ad1816a= [HW,ALSA]
2364 snd-ad1848= [HW,ALSA]
2366 snd-ali5451= [HW,ALSA]
2368 snd-als100= [HW,ALSA]
2370 snd-als4000= [HW,ALSA]
2372 snd-azt2320= [HW,ALSA]
2374 snd-cmi8330= [HW,ALSA]
2376 snd-cmipci= [HW,ALSA]
2378 snd-cs4231= [HW,ALSA]
2380 snd-cs4232= [HW,ALSA]
2382 snd-cs4236= [HW,ALSA]
2384 snd-cs4281= [HW,ALSA]
2386 snd-cs46xx= [HW,ALSA]
2388 snd-dt019x= [HW,ALSA]
2390 snd-dummy= [HW,ALSA]
2392 snd-emu10k1= [HW,ALSA]
2394 snd-ens1370= [HW,ALSA]
2396 snd-ens1371= [HW,ALSA]
2398 snd-es968= [HW,ALSA]
2400 snd-es1688= [HW,ALSA]
2402 snd-es18xx= [HW,ALSA]
2404 snd-es1938= [HW,ALSA]
2406 snd-es1968= [HW,ALSA]
2408 snd-fm801= [HW,ALSA]
2410 snd-gusclassic= [HW,ALSA]
2412 snd-gusextreme= [HW,ALSA]
2414 snd-gusmax= [HW,ALSA]
2418 snd-ice1712= [HW,ALSA]
2420 snd-intel8x0= [HW,ALSA]
2422 snd-interwave= [HW,ALSA]
2427 snd-korg1212= [HW,ALSA]
2429 snd-maestro3= [HW,ALSA]
2431 snd-mpu401= [HW,ALSA]
2433 snd-mtpav= [HW,ALSA]
2435 snd-nm256= [HW,ALSA]
2437 snd-opl3sa2= [HW,ALSA]
2445 snd-opti93x= [HW,ALSA]
2449 snd-rme32= [HW,ALSA]
2451 snd-rme96= [HW,ALSA]
2453 snd-rme9652= [HW,ALSA]
2459 snd-sbawe= [HW,ALSA]
2461 snd-serial= [HW,ALSA]
2463 snd-sgalaxy= [HW,ALSA]
2465 snd-sonicvibes= [HW,ALSA]
2470 snd-sun-cs4231= [HW,ALSA]
2472 snd-trident= [HW,ALSA]
2474 snd-usb-audio= [HW,ALSA,USB]
2476 snd-via82xx= [HW,ALSA]
2478 snd-virmidi= [HW,ALSA]
2480 snd-wavefront= [HW,ALSA]
2482 snd-ymfpci= [HW,ALSA]
2485 [KNL] Should the soft-lockup detector generate panics.
2487 sonypi.*= [HW] Sony Programmable I/O Control Device driver
2488 See Documentation/sonypi.txt
2490 specialix= [HW,SERIAL] Specialix multi-serial port adapter
2491 See Documentation/serial/specialix.txt.
2493 spia_io_base= [HW,MTD]
2499 Format: <io>,<irq>,<dma>,<mpu_io>,<mpu_irq>
2501 st= [HW,SCSI] SCSI tape parameters (buffers, etc.)
2502 See Documentation/scsi/st.txt.
2505 Enabled the stack tracer on boot up.
2509 Set the STI (builtin display/keyboard on the HP-PARISC
2510 machines) console (graphic card) which should be used
2511 as the initial boot-console.
2512 See also comment in drivers/video/console/sticore.c.
2515 See comment in drivers/video/console/sticore.c.
2518 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2520 sunrpc.min_resvport=
2521 sunrpc.max_resvport=
2523 SunRPC servers often require that client requests
2524 originate from a privileged port (i.e. a port in the
2525 range 0 < portnr < 1024).
2526 An administrator who wishes to reserve some of these
2527 ports for other uses may adjust the range that the
2528 kernel's sunrpc client considers to be privileged
2529 using these two parameters to set the minimum and
2530 maximum port values.
2534 Control how the NFS server code allocates CPUs to
2535 service thread pools. Depending on how many NICs
2536 you have and where their interrupts are bound, this
2537 option will affect which CPUs will do NFS serving.
2538 Note: this parameter cannot be changed while the
2539 NFS server is running.
2541 auto the server chooses an appropriate mode
2542 automatically using heuristics
2543 global a single global pool contains all CPUs
2544 percpu one pool for each CPU
2545 pernode one pool for each NUMA node (equivalent
2546 to global on non-NUMA machines)
2548 sunrpc.tcp_slot_table_entries=
2549 sunrpc.udp_slot_table_entries=
2551 Sets the upper limit on the number of simultaneous
2552 RPC calls that can be sent from the client to a
2553 server. Increasing these values may allow you to
2554 improve throughput, but will also increase the
2555 amount of memory reserved for use by the client.
2557 swiotlb= [IA-64] Number of I/O TLB slabs
2561 sym53c416= [HW,SCSI]
2562 See header of drivers/scsi/sym53c416.c.
2564 sysrq_always_enabled
2566 Ignore sysrq setting - this boot parameter will
2567 neutralize any effect of /proc/sys/kernel/sysrq.
2568 Useful for debugging.
2571 See header of drivers/scsi/t128.c.
2575 test_suspend= [SUSPEND]
2576 Specify "mem" (for Suspend-to-RAM) or "standby" (for
2577 standby suspend) as the system sleep state to briefly
2578 enter during system startup. The system is woken from
2579 this state using a wakeup-capable RTC alarm.
2581 thash_entries= [KNL,NET]
2582 Set number of hash buckets for TCP connection
2584 thermal.act= [HW,ACPI]
2585 -1: disable all active trip points in all thermal zones
2586 <degrees C>: override all lowest active trip points
2588 thermal.crt= [HW,ACPI]
2589 -1: disable all critical trip points in all thermal zones
2590 <degrees C>: override all critical trip points
2592 thermal.nocrt= [HW,ACPI]
2593 Set to disable actions on ACPI thermal zone
2594 critical and hot trip points.
2596 thermal.off= [HW,ACPI]
2597 1: disable ACPI thermal control
2599 thermal.psv= [HW,ACPI]
2600 -1: disable all passive trip points
2601 <degrees C>: override all passive trip points to this
2604 thermal.tzp= [HW,ACPI]
2605 Specify global default ACPI thermal zone polling rate
2606 <deci-seconds>: poll all this frequency
2607 0: no polling (default)
2610 See comment before function dc390_setup() in
2611 drivers/scsi/tmscsim.c.
2615 Specify if the kernel should make use of the cpu
2616 topology informations if the hardware supports these.
2617 The scheduler will make use of these informations and
2618 e.g. base its process migration decisions on it.
2623 tpm_suspend_pcr=[HW,TPM]
2624 Format: integer pcr id
2625 Specify that at suspend time, the tpm driver
2626 should extend the specified pcr with zeros,
2627 as a workaround for some chips which fail to
2628 flush the last written pcr on TPM_SaveState.
2629 This will guarantee that all the other pcrs
2632 trace_buf_size=nn[KMG]
2633 [FTRACE] will set tracing buffer size.
2635 trace_event=[event-list]
2636 [FTRACE] Set and start specified trace events in order
2637 to facilitate early boot debugging.
2638 See also Documentation/trace/events.txt
2640 trix= [HW,OSS] MediaTrix AudioTrix Pro
2642 <io>,<irq>,<dma>,<dma2>,<sb_io>,<sb_irq>,<sb_dma>,<mpu_io>,<mpu_irq>
2644 tsc= Disable clocksource-must-verify flag for TSC.
2646 [x86] reliable: mark tsc clocksource as reliable, this
2647 disables clocksource verification at runtime.
2648 Used to enable high-resolution timer mode on older
2649 hardware, and in virtualized environment.
2651 turbografx.map[2|3]= [HW,JOY]
2652 TurboGraFX parallel port interface
2654 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2655 See also Documentation/input/joystick-parport.txt
2657 u14-34f= [HW,SCSI] UltraStor 14F/34F SCSI host adapter
2658 See header of drivers/scsi/u14-34f.c.
2666 uhash_entries= [KNL,NET]
2667 Set number of hash buckets for UDP/UDP-Lite connections
2670 [USB] Ignore overcurrent events (default N).
2671 Some badly-designed motherboards generate lots of
2672 bogus events, for ports that aren't wired to
2673 anything. Set this parameter to avoid log spamming.
2674 Note that genuine overcurrent events won't be
2679 Set unknown_nmi_panic=1 early on boot.
2681 usbcore.autosuspend=
2682 [USB] The autosuspend time delay (in seconds) used
2683 for newly-detected USB devices (default 2). This
2684 is the time required before an idle device will be
2685 autosuspended. Devices for which the delay is set
2686 to a negative value won't be autosuspended at all.
2688 usbcore.usbfs_snoop=
2689 [USB] Set to log all usbfs traffic (default 0 = off).
2691 usbcore.blinkenlights=
2692 [USB] Set to cycle leds on hubs (default 0 = off).
2694 usbcore.old_scheme_first=
2695 [USB] Start with the old device initialization
2696 scheme (default 0 = off).
2698 usbcore.use_both_schemes=
2699 [USB] Try the other device initialization scheme
2700 if the first one fails (default 1 = enabled).
2702 usbcore.initial_descriptor_timeout=
2703 [USB] Specifies timeout for the initial 64-byte
2704 USB_REQ_GET_DESCRIPTOR request in milliseconds
2705 (default 5000 = 5.0 seconds).
2708 [USBHID] The interval which mice are to be polled at.
2710 usb-storage.delay_use=
2711 [UMS] The delay in seconds before a new device is
2712 scanned for Logical Units (default 5).
2715 [UMS] A list of quirks entries to supplement or
2716 override the built-in unusual_devs list. List
2717 entries are separated by commas. Each entry has
2718 the form VID:PID:Flags where VID and PID are Vendor
2719 and Product ID values (4-digit hex numbers) and
2720 Flags is a set of characters, each corresponding
2721 to a common usb-storage quirk flag as follows:
2722 a = SANE_SENSE (collect more than 18 bytes
2724 b = BAD_SENSE (don't collect more than 18
2725 bytes of sense data);
2726 c = FIX_CAPACITY (decrease the reported
2727 device capacity by one sector);
2728 h = CAPACITY_HEURISTICS (decrease the
2729 reported device capacity by one
2730 sector if the number is odd);
2731 i = IGNORE_DEVICE (don't bind to this
2733 l = NOT_LOCKABLE (don't try to lock and
2734 unlock ejectable media);
2735 m = MAX_SECTORS_64 (don't transfer more
2736 than 64 sectors = 32 KB at a time);
2737 o = CAPACITY_OK (accept the capacity
2738 reported by the device);
2739 r = IGNORE_RESIDUE (the device reports
2740 bogus residue values);
2741 s = SINGLE_LUN (the device has only one
2743 w = NO_WP_DETECT (don't test whether the
2744 medium is write-protected).
2745 Example: quirks=0419:aaf5:rl,0421:0433:rc
2748 [X86] Flags controlling user PTE allocations.
2750 nohigh = do not allocate PTE pages in
2751 HIGHMEM regardless of setting
2755 vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2756 vdso=1: enable VDSO (default)
2757 vdso=0: disable VDSO mapping
2760 vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2761 vdso32=1: enable 32-bit VDSO (default)
2762 vdso32=0: disable 32-bit VDSO mapping
2765 vector=percpu: enable percpu vector domain
2767 video= [FB] Frame buffer configuration
2768 See Documentation/fb/modedb.txt.
2770 vga= [BOOT,X86-32] Select a particular video mode
2771 See Documentation/x86/boot.txt and
2772 Documentation/svga.txt.
2773 Use vga=ask for menu.
2774 This is actually a boot loader parameter; the value is
2775 passed to the kernel using a special protocol.
2777 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
2778 size of <nn>. This can be used to increase the
2779 minimum size (128MB on x86). It can also be used to
2780 decrease the size and leave more room for directly
2783 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
2786 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
2789 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
2792 vt.cur_default= [VT] Default cursor shape.
2793 Format: 0xCCBBAA, where AA, BB, and CC are the same as
2794 the parameters of the <Esc>[?A;B;Cc escape sequence;
2795 see VGA-softcursor.txt. Default: 2 = underline.
2797 vt.default_blu= [VT]
2798 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
2799 Change the default blue palette of the console.
2800 This is a 16-member array composed of values
2803 vt.default_grn= [VT]
2804 Format: <green0>,<green1>,<green2>,...,<green15>
2805 Change the default green palette of the console.
2806 This is a 16-member array composed of values
2809 vt.default_red= [VT]
2810 Format: <red0>,<red1>,<red2>,...,<red15>
2811 Change the default red palette of the console.
2812 This is a 16-member array composed of values
2818 Set system-wide default UTF-8 mode for all tty's.
2819 Default is 1, i.e. UTF-8 mode is enabled for all
2820 newly opened terminals.
2822 vt.global_cursor_default=
2825 Set system-wide default for whether a cursor
2826 is shown on new VTs. Default is -1,
2827 i.e. cursors will be created by default unless
2828 overridden by individual drivers. 0 will hide
2829 cursors, 1 will display them.
2831 waveartist= [HW,OSS]
2832 Format: <io>,<irq>,<dma>,<dma2>
2835 See header of drivers/scsi/wd33c93.c.
2838 See header of drivers/scsi/wd7000.c.
2841 See Documentation/watchdog/wdt.txt.
2843 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
2844 default x2apic cluster mode on platforms
2847 xd= [HW,XT] Original XT pre-IDE (RLL encoded) disks.
2848 xd_geo= See header of drivers/block/xd.c.
2850 xirc2ps_cs= [NET,PCMCIA]
2852 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
2854 ______________________________________________________________________
2858 Add documentation for ALSA options.
2859 Add more DRM drivers.
git://ftp.safe.ca / safe / jmp / linux-2.6 / blob