Kernel Parameters ~~~~~~~~~~~~~~~~~The following is a consolidated list of the kernel parameters as implemented(mostly) by the __setup() macro and sorted into English Dictionary order(defined as ignoring all punctuation and sorting digits before letters in acase insensitive manner), and with descriptions where known.Module parameters for loadable modules are specified only as theparameter name with optional '=' and value as appropriate, such as:modprobe usbcore blinkenlights=1Module parameters for modules that are built into the kernel imageare specified on the kernel command line with the module name plus'.' plus parameter name, with '=' and value if appropriate, such as:usbcore.blinkenlights=1Hyphens (dashes) and underscores are equivalent in parameter names, solog_buf_len=1M print-fatal-signals=1can also be entered aslog-buf-len=1M print_fatal_signals=1This document may not be entirely up to date and comprehensive. The command"modinfo -p ${modulename}" shows a current list of all parameters of a loadablemodule. Loadable modules, after being loaded into the running kernel, alsoreveal their parameters in /sys/module/${modulename}/parameters/. Some of theseparameters may be changed at runtime by the command"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".The parameters listed below are only valid if certain kernel build options wereenabled and if respective hardware is present. The text in square brackets atthe beginning of each description states the restrictions within which aparameter is applicable:ACPIACPI support is enabled.AGPAGP (Accelerated Graphics Port) is enabled.ALSAALSA sound support is enabled.APICAPIC support is enabled.APMAdvanced Power Management support is enabled.AVR32AVR32 architecture is enabled.AX25Appropriate AX.25 support is enabled.BLACKFIN Blackfin architecture is enabled.DRMDirect Rendering Management support is enabled.DYNAMIC_DEBUG Build in debug messages and enable them at runtimeEDDBIOS Enhanced Disk Drive Services (EDD) is enabledEFIEFI Partitioning (GPT) is enabledEIDEEIDE/ATAPI support is enabled.FBThe frame buffer device is enabled.GCOVGCOV profiling is enabled.HWAppropriate hardware is enabled.IA-64IA-64 architecture is enabled.IMA Integrity measurement architecture is enabled.IOSCHEDMore than one I/O scheduler is enabled.IP_PNPIP DHCP, BOOTP, or RARP is enabled.IPV6IPv6 support is enabled.ISAPNPISA PnP code is enabled.ISDNAppropriate ISDN support is enabled.JOYAppropriate joystick support is enabled.KGDBKernel debugger support is enabled.KVMKernel Virtual Machine support is enabled.LIBATA Libata driver is enabledLPPrinter support is enabled.LOOPLoopback device support is enabled.M68kM68k architecture is enabled.These options have more detailed description inside ofDocumentation/m68k/kernel-options.txt.MCAMCA bus support is enabled.MDAMDA console support is enabled.MOUSEAppropriate mouse support is enabled.MSIMessage Signaled Interrupts (PCI).MTDMTD (Memory Technology Device) support is enabled.NETAppropriate network support is enabled.NUMANUMA support is enabled.NFSAppropriate NFS support is enabled.OSSOSS sound support is enabled.PV_OPSA paravirtualized kernel is enabled.PARIDEThe ParIDE (parallel port IDE) subsystem is enabled.PARISCThe PA-RISC architecture is enabled.PCIPCI bus support is enabled.PCIEPCI Express support is enabled.PCMCIAThe PCMCIA subsystem is enabled.PNPPlug & Play support is enabled.PPCPowerPC architecture is enabled.PPTParallel port support is enabled.PS2Appropriate PS/2 support is enabled.RAMRAM disk support is enabled.S390S390 architecture is enabled.SCSIAppropriate SCSI support is enabled.A lot of drivers have their options described insidethe Documentation/scsi/ sub-directory.SECURITY Different security models are enabled.SELINUX SELinux support is enabled.APPARMOR AppArmor support is enabled.SERIALSerial support is enabled.SHSuperH architecture is enabled.SMPThe kernel is an SMP kernel.SPARCSparc architecture is enabled.SWSUSPSoftware suspend (hibernation) is enabled.SUSPENDSystem suspend states are enabled.FTRACEFunction tracing enabled.TPMTPM drivers are enabled.TSAppropriate touchscreen support is enabled.UMSUSB Mass Storage support is enabled.USBUSB support is enabled.USBHIDUSB Human Interface Device support is enabled.V4LVideo For Linux support is enabled.VGAThe VGA console has been enabled.VTVirtual terminal support is enabled.WDTWatchdog support is enabled.XTIBM PC/XT MFM hard disk support is enabled.X86-32X86-32, aka i386 architecture is enabled.X86-64X86-64 architecture is enabled.More X86-64 boot options can be found inDocumentation/x86/x86_64/boot-options.txt .X86Either 32bit or 64bit x86 (same as X86-32+X86-64)XENXen support is enabledIn addition, the following text indicates that the option:BUGS=Relates to possible processor bugs on the said processor.KNLIs a kernel start-up parameter.BOOTIs a boot loader parameter.Parameters denoted with BOOT are actually interpreted by the bootloader, and have no meaning to the kernel directly.Do not modify the syntax of boot loader parameters without extremeneed or coordination with <Documentation/x86/boot.txt>.There are also arch-specific kernel-parameters not documented here.See for example <Documentation/x86/x86_64/boot-options.txt>.Note that ALL kernel parameters listed below are CASE SENSITIVE, and thata trailing = on the name of any parameter states that that parameter willbe entered as an environment variable, whereas its absence indicates thatit will appear as a kernel argument readable via /proc/cmdline by programsrunning once the system is up.The number of kernel parameters is not limited, but the length of thecomplete command line (parameters including spaces etc.) is limited toa fixed number of characters. This limit depends on the architectureand is between 256 and 4096 characters. It is defined in the file./include/asm/setup.h as COMMAND_LINE_SIZE.Finally, the [KMG] suffix is commonly described after a number of kernelparameter values. These 'K', 'M', and 'G' letters represent the _binary_multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30bytes respectively. Such letter suffixes can also be entirely omitted.acpi=[HW,ACPI,X86]Advanced Configuration and Power InterfaceFormat: { force | off | strict | noirq | rsdt }force -- enable ACPI if default was offoff -- disable ACPI if default was onnoirq -- do not use ACPI for IRQ routingstrict -- Be less tolerant of platforms that are notstrictly ACPI specification compliant.rsdt -- prefer RSDT over (default) XSDTcopy_dsdt -- copy DSDT to memorySee also Documentation/power/pm.txt, pci=noacpiacpi_apic_instance=[ACPI, IOAPIC]Format: <int>2: use 2nd APIC table, if available1,0: use 1st APIC tabledefault: 0acpi_backlight=[HW,ACPI]acpi_backlight=vendoracpi_backlight=videoIf set to vendor, prefer vendor specific driver(e.g. thinkpad_acpi, sony_acpi, etc.) insteadof the ACPI video.ko driver.acpi.debug_layer=[HW,ACPI,ACPI_DEBUG]acpi.debug_level=[HW,ACPI,ACPI_DEBUG]Format: <int>CONFIG_ACPI_DEBUG must be enabled to produce any ACPIdebug output. Bits in debug_layer correspond to a_COMPONENT in an ACPI source file, e.g., #define _COMPONENT ACPI_PCI_COMPONENTBits in debug_level correspond to a level inACPI_DEBUG_PRINT statements, e.g., ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...The debug_level mask defaults to "info". SeeDocumentation/acpi/debug.txt for more information aboutdebug layers and levels.Enable processor driver info messages: acpi.debug_layer=0x20000000Enable PCI/PCI interrupt routing info messages: acpi.debug_layer=0x400000Enable AML "Debug" output, i.e., stores to the Debugobject while interpreting AML: acpi.debug_layer=0xffffffff acpi.debug_level=0x2Enable all messages related to ACPI hardware: acpi.debug_layer=0x2 acpi.debug_level=0xffffffffSome values produce so much output that the system isunusable. The "log_buf_len" parameter may be usefulif you need to capture more output.acpi_irq_balance [HW,ACPI]ACPI will balance active IRQsdefault in APIC modeacpi_irq_nobalance [HW,ACPI]ACPI will not move active IRQs (default)default in PIC modeacpi_irq_isa=[HW,ACPI] If irq_balance, mark listed IRQs used by ISAFormat: <irq>,<irq>...acpi_irq_pci=[HW,ACPI] If irq_balance, clear listed IRQs foruse by PCIFormat: <irq>,<irq>...acpi_no_auto_ssdt[HW,ACPI] Disable automatic loading of SSDTacpi_os_name=[HW,ACPI] Tell ACPI BIOS the name of the OSFormat: To spoof as Windows 98: ="Microsoft Windows"acpi_osi=[HW,ACPI] Modify list of supported OS interface stringsacpi_osi="string1"# add string1 -- only one stringacpi_osi="!string2"# remove built-in string2acpi_osi=# disable all stringsacpi_pm_good[X86]Override the pmtimer bug detection: force the kernelto assume that this machine's pmtimer latches its valueand always returns good values.acpi_sci=[HW,ACPI] ACPI System Control Interrupt trigger modeFormat: { level | edge | high | low }acpi_serialize[HW,ACPI] force serialization of AML methodsacpi_skip_timer_override [HW,ACPI]Recognize and ignore IRQ0/pin2 Interrupt Override.For broken nForce2 BIOS resulting in XT-PIC timer.acpi_sleep=[HW,ACPI] Sleep optionsFormat: { s3_bios, s3_mode, s3_beep, s4_nohwsig, old_ordering, nonvs, sci_force_enable }See Documentation/power/video.txt for information ons3_bios and s3_mode.s3_beep is for debugging; it makes the PC's speaker beepas soon as the kernel's real-mode entry point is called.s4_nohwsig prevents ACPI hardware signature from beingused during resume from hibernation.old_ordering causes the ACPI 1.0 ordering of the _PTScontrol method, with respect to putting devices intolow power states, to be enforced (the ACPI 2.0 orderingof _PTS is used by default).nonvs prevents the kernel from saving/restoring theACPI NVS memory during suspend/hibernation and resume.sci_force_enable causes the kernel to set SCI_EN directlyon resume from S1/S3 (which is against the ACPI spec,but some broken systems don't work without it).acpi_use_timer_override [HW,ACPI]Use timer override. For some broken Nvidia NF5 boardsthat require a timer override, but don't have HPETacpi_enforce_resources=[ACPI]{ strict | lax | no }Check for resource conflicts between native driversand ACPI OperationRegions (SystemIO and SystemMemoryonly). IO ports and memory declared in ACPI might beused by the ACPI subsystem in arbitrary AML code andcan interfere with legacy drivers.strict (default): access to resources claimed by ACPIis denied; legacy drivers trying to access reservedresources will fail to bind to device using them.lax: access to resources claimed by ACPI is allowed;legacy drivers trying to access reserved resourceswill bind successfully but a warning message is logged.no: ACPI OperationRegions are not marked as reserved,no further checks are performed.add_efi_memmap[EFI; X86] Include EFI memory map inkernel's map of available physical RAM.agp=[AGP]{ off | try_unsupported }off: disable AGP supporttry_unsupported: try to drive unsupported chipsets(may crash computer or cause data corruption)ALSA[HW,ALSA]See Documentation/sound/alsa/alsa-parameters.txtalignment=[KNL,ARM]Allow the default userspace alignment fault handlerbehaviour to be specified. Bit 0 enables warnings,bit 1 enables fixups, and bit 2 sends a segfault.amd_iommu=[HW,X86-84]Pass parameters to the AMD IOMMU driver in the system.Possible values are:fullflush - enable flushing of IO/TLB entries when they are unmapped. Otherwise they are flushed before they will be reused, which is a lot of fasteroff - do not initialize any AMD IOMMU found in the systemamijoy.map=[HW,JOY] Amiga joystick supportMap of devices attached to JOY0DAT and JOY1DATFormat: <a>,<b>See also Documentation/kernel/input/joystick.txtanalog.map=[HW,JOY] Analog joystick and gamepad supportSpecifies type or capabilities of an analog joystickconnected to one of 16 gameportsFormat: <type1>,<type2>,..<type16>apc=[HW,SPARC]Power management functions (SPARCstation-4/5 + deriv.)Format: noidleDisable APC CPU standby support. SPARCstation-Fox doesnot play well with APC CPU idle - disable it if you haveAPC and your system crashes randomly.apic=[APIC,X86-32] Advanced Programmable Interrupt ControllerChange the output verbosity whilst bootingFormat: { quiet (default) | verbose | debug }Change the amount of debugging information outputwhen initialising the APIC and IO-APIC components.autoconf=[IPV6]See Documentation/networking/ipv6.txt.show_lapic=[APIC,X86] Advanced Programmable Interrupt ControllerLimit apic dumping. The parameter defines the maximalnumber of local apics being dumped. Also it is possibleto set it to "all" by meaning -- no limit here.Format: { 1 (default) | 2 | ... | all }.The parameter valid if only apic=debug orapic=verbose is specified.Example: apic=debug show_lapic=allapm=[APM] Advanced Power ManagementSee header of arch/x86/kernel/apm_32.c.arcrimi=[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cardsFormat: <io>,<irq>,<nodeID>ataflop=[HW,M68k]atarimouse=[HW,MOUSE] Atari Mouseatkbd.extra=[HW] Enable extra LEDs and keys on IBM RapidAccess,EzKey and similar keyboardsatkbd.reset=[HW] Reset keyboard during initializationatkbd.set=[HW] Select keyboard code setFormat: <int> (2 = AT (default), 3 = PS/2)atkbd.scroll=[HW] Enable scroll wheel on MS Office and similarkeyboardsatkbd.softraw=[HW] Choose between synthetic and real raw modeFormat: <bool> (0 = real, 1 = synthetic (default))atkbd.softrepeat= [HW]Use software keyboard repeatautotest[IA64]baycom_epp=[HW,AX25]Format: <io>,<mode>baycom_par=[HW,AX25] BayCom Parallel Port AX.25 ModemFormat: <io>,<mode>See header of drivers/net/hamradio/baycom_par.c.baycom_ser_fdx=[HW,AX25]BayCom Serial Port AX.25 Modem (Full Duplex Mode)Format: <io>,<irq>,<mode>[,<baud>]See header of drivers/net/hamradio/baycom_ser_fdx.c.baycom_ser_hdx=[HW,AX25]BayCom Serial Port AX.25 Modem (Half Duplex Mode)Format: <io>,<irq>,<mode>See header of drivers/net/hamradio/baycom_ser_hdx.c.boot_delay=Milliseconds to delay each printk during boot.Values larger than 10 seconds (10000) are changed tono delay (0).Format: integerbootmem_debug[KNL] Enable bootmem allocator debug messages.bttv.card=[HW,V4L] bttv (bt848 + bt878 based grabber cards)bttv.radio=Most important insmod options are available askernel args too.bttv.pll=See Documentation/video4linux/bttv/Insmod-optionsbttv.tuner=and Documentation/video4linux/bttv/CARDLISTbulk_remove=off[PPC] This parameter disables the use of the pSeriesfirmware feature for flushing multiple hpte entriesat a time.c101=[NET] Moxa C101 synchronous serial cardcachesize=[BUGS=X86-32] Override level 2 CPU cache size detection.Sometimes CPU hardware bugs make them report the cachesize incorrectly. The kernel will attempt work aroundsto fix known problems, but for some CPUs it is notpossible to determine what the correct size should be.This option provides an override for these situations.capability.disable=[SECURITY] Disable capabilities. This would normallybe used only if an alternative security model is to beconfigured. Potentially dangerous and should only beused if you are entirely sure of the consequences.ccw_timeout_log [S390]See Documentation/s390/CommonIO for details.cgroup_disable= [KNL] Disable a particular controllerFormat: {name of the controller(s) to disable}{Currently supported controllers - "memory"}checkreqprot[SELINUX] Set initial checkreqprot flag value.Format: { "0" | "1" }See security/selinux/Kconfig help text.0 -- check protection applied by kernel (includesany implied execute protection).1 -- check protection requested by application.Default value is set via a kernel config option.Value can be changed at runtime via/selinux/checkreqprot.cio_ignore=[S390]See Documentation/s390/CommonIO for details.clock=[BUGS=X86-32, HW] gettimeofday clocksource override.[Deprecated]Forces specified clocksource (if available) to be usedwhen calculating gettimeofday(). If specifiedclocksource is not available, it defaults to PIT.Format: { pit | tsc | cyclone | pmtmr }clocksource=Override the default clocksourceFormat: <string>Override the default clocksource and use the clocksourcewith the name specified.Some clocksource names to choose from, depending onthe platform:[all] jiffies (this is the base, fallback clocksource)[ACPI] acpi_pm[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,pxa_timer,timer3,32k_counter,timer0_1[AVR32] avr32[X86-32] pit,hpet,tsc;scx200_hrt on Geode; cyclone on IBM x440[MIPS] MIPS[PARISC] cr16[S390] tod[SH] SuperH[SPARC64] tick[X86-64] hpet,tscclearcpuid=BITNUM [X86]Disable CPUID feature X for the kernel. Seearch/x86/include/asm/cpufeature.h for the valid bitnumbers. Note the Linux specific bits are not necessarilystable over kernel options, but the vendor specificones should be.Also note that user programs calling CPUID directlyor using the feature without checking anythingwill still see it. This just prevents it frombeing used by the kernel or shown in /proc/cpuinfo.Also note the kernel might malfunction if you disablesome critical bits.cmo_free_hint=[PPC] Format: { yes | no }Specify whether pages are marked as being inactivewhen they are freed. This is used in CMO environmentsto determine OS memory pressure for page stealing bya hypervisor.Default: yescode_bytes[X86] How many bytes of object code to printin an oops report.Range: 0 - 8192Default: 64com20020=[HW,NET] ARCnet - COM20020 chipsetFormat:<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]com90io=[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)Format: <io>[,<irq>]com90xx=[HW,NET]ARCnet - COM90xx chipset (memory-mapped buffers)Format: <io>[,<irq>[,<memstart>]]condev=[HW,S390] console deviceconmode=console=[KNL] Output console device and options.tty<n>Use the virtual console device <n>.ttyS<n>[,options]ttyUSB0[,options]Use the specified serial port. The options are ofthe form "bbbbpnf", where "bbbb" is the baud rate,"p" is parity ("n", "o", or "e"), "n" is number ofbits, and "f" is flow control ("r" for RTS oromit it). Default is "9600n8".See Documentation/serial-console.txt for moreinformation. SeeDocumentation/networking/netconsole.txt for analternative.uart[8250],io,<addr>[,options]uart[8250],mmio,<addr>[,options]Start an early, polled-mode console on the 8250/16550UART at the specified I/O port or MMIO address,switching to the matching ttyS device later. Theoptions are the same as for ttyS, above. If the device connected to the port is not a TTY but a braille device, prepend "brl," before the device type, for instanceconsole=brl,ttyS0For now, only VisioBraille is supported.consoleblank=[KNL] The console blank (screen saver) timeout inseconds. Defaults to 10*60 = 10mins. A value of 0disables the blank timer.coredump_filter=[KNL] Change the default value for/proc/<pid>/coredump_filter.See also Documentation/filesystems/proc.txt.cpcihp_generic=[HW,PCI] Generic port I/O CompactPCI driverFormat:<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]crashkernel=size[KMG][@offset[KMG]][KNL] Using kexec, Linux can switch to a 'crash kernel'upon panic. This parameter reserves the physicalmemory region [offset, offset + size] for that kernelimage. If '@offset' is omitted, then a suitable offsetis selected automatically. CheckDocumentation/kdump/kdump.txt for further details.crashkernel=range1:size1[,range2:size2,...][@offset][KNL] Same as above, but depends on the memoryin the running system. The syntax of range isstart-[end] where start and end are botha memory unit (amount[KMG]). See alsoDocumentation/kdump/kdump.txt for an example.cs89x0_dma=[HW,NET]Format: <dma>cs89x0_media=[HW,NET]Format: { rj45 | aui | bnc }dasd=[HW,NET]See header of drivers/s390/block/dasd_devmap.c.db9.dev[2|3]=[HW,JOY] Multisystem joystick support via parallel port(one device per port)Format: <port#>,<type>See also Documentation/input/joystick-parport.txtddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boottime. See Documentation/dynamic-debug-howto.txt fordetails.debug[KNL] Enable kernel debugging (events log level).debug_locks_verbose=[KNL] verbose self-testsFormat=<0|1>Print debugging info while doing the locking APIself-tests.We default to 0 (no extra messages), setting it to1 will print _a lot_ more information - normallyonly useful to kernel developers.debug_objects[KNL] Enable object debuggingno_debug_objects[KNL] Disable object debuggingdebugpat[X86] Enable PAT debuggingdecnet.addr=[HW,NET]Format: <area>[,<node>]See also Documentation/networking/decnet.txt.default_hugepagesz=[same as hugepagesz=] The size of the defaultHugeTLB page size. This is the size represented bythe legacy /proc/ hugepages APIs, used for SHM, anddefault size when mounting hugetlbfs filesystems.Defaults to the default architecture's huge page sizeif not specified.dhash_entries=[KNL]Set number of hash buckets for dentry cache.digi=[HW,SERIAL]IO parameters + enable/disable command.digiepca=[HW,SERIAL]See drivers/char/README.epca andDocumentation/serial/digiepca.txt.disable=[IPV6]See Documentation/networking/ipv6.txt.disable_ddw [PPC/PSERIES]Disable Dynamic DMA Window support. Use this ifto workaround buggy firmware.disable_ipv6=[IPV6]See Documentation/networking/ipv6.txt.disable_mtrr_cleanup [X86]The kernel tries to adjust MTRR layout from continuousto discrete, to make X server driver able to add WBentry later. This parameter disables that.disable_mtrr_trim [X86, Intel and AMD only]By default the kernel will trim any uncacheablememory out of your available memory pool based onMTRR settings. This parameter disables that behavior,possibly causing your machine to run very slowly.disable_timer_pin_1 [X86]Disable PIN 1 of APIC timerCan be useful to work around chipset bugs.dma_debug=offIf the kernel is compiled with DMA_API_DEBUG support,this option disables the debugging code at boot.dma_debug_entries=<number>This option allows to tune the number of preallocatedentries for DMA-API debugging code. One entry isrequired per DMA-API allocation. Use this if theDMA-API debugging code disables itself because thearchitectural default is too low.dma_debug_driver=<driver_name>With this option the DMA-API debugging driverfilter feature can be enabled at boot time. Justpass the driver to filter for as the parameter.The filter can be disabled or changed to anotherdriver later using sysfs.dscc4.setup=[NET]earlycon=[KNL] Output early console device and options.uart[8250],io,<addr>[,options]uart[8250],mmio,<addr>[,options]uart[8250],mmio32,<addr>[,options]Start an early, polled-mode console on the 8250/16550UART at the specified I/O port or MMIO address.MMIO inter-register address stride is either 8bit (mmio) or 32bit (mmio32).The options are the same as for ttyS, above.earlyprintk=[X86,SH,BLACKFIN]earlyprintk=vgaearlyprintk=serial[,ttySn[,baudrate]]earlyprintk=ttySn[,baudrate]earlyprintk=dbgp[debugController#]Append ",keep" to not disable it when the real consoletakes over.Only vga or serial or usb debug port at a time.Currently only ttyS0 and ttyS1 are supported.Interaction with the standard serial driver is notvery good.The VGA output is eventually overwritten by the realconsole.ekgdboc=[X86,KGDB] Allow early kernel console debuggingekgdboc=kbdThis is designed to be used in conjunction withthe boot argument: earlyprintk=vgaedd=[EDD]Format: {"off" | "on" | "skip[mbr]"}eisa_irq_edge=[PARISC,HW]See header of drivers/parisc/eisa.c.elanfreq=[X86-32]See comment before function elanfreq_setup() inarch/x86/kernel/cpu/cpufreq/elanfreq.c.elevator=[IOSCHED]Format: {"cfq" | "deadline" | "noop"}See Documentation/block/as-iosched.txt andDocumentation/block/deadline-iosched.txt for details.elfcorehdr=[IA64,PPC,SH,X86]Specifies physical address of start of kernel coreimage elf header. Generally kexec loader willpass this option to capture kernel.See Documentation/kdump/kdump.txt for details.enable_mtrr_cleanup [X86]The kernel tries to adjust MTRR layout from continuousto discrete, to make X server driver able to add WBentry later. This parameter enables that.enable_timer_pin_1 [X86]Enable PIN 1 of APIC timerCan be useful to work around chipset bugs(in particular on some ATI chipsets).The kernel tries to set a reasonable default.enforcing[SELINUX] Set initial enforcing status.Format: {"0" | "1"}See security/selinux/Kconfig help text.0 -- permissive (log only, no denials).1 -- enforcing (deny and log).Default value is 0.Value can be changed at runtime via /selinux/enforce.erst_disable[ACPI]Disable Error Record Serialization Table (ERST)support.ether=[HW,NET] Ethernet cards parametersThis option is obsoleted by the "netdev=" option, whichhas equivalent usage. See its documentation for details.failslab=fail_page_alloc=fail_make_request=[KNL]General fault injection mechanism.Format: <interval>,<probability>,<space>,<times>See also /Documentation/fault-injection/.floppy=[HW]See Documentation/blockdev/floppy.txt.force_pal_cache_flush[IA-64] Avoid check_sal_cache_flush which may hang onbuggy SAL_CACHE_FLUSH implementations. Using thisparameter will force ia64_sal_cache_flush to callia64_pal_cache_flush instead of SAL_CACHE_FLUSH.ftrace=[tracer][FTRACE] will set and start the specified traceras early as possible in order to facilitate earlyboot debugging.ftrace_dump_on_oops[=orig_cpu][FTRACE] will dump the trace buffers on oops.If no parameter is passed, ftrace will dumpbuffers of all CPUs, but if you pass orig_cpu, it willdump only the buffer of the CPU that triggered theoops.ftrace_filter=[function-list][FTRACE] Limit the functions traced by the functiontracer at boot up. function-list is a comma separatedlist of functions. This list can be changed at runtime by the set_ftrace_filter file in the debugfstracing directory. ftrace_notrace=[function-list][FTRACE] Do not trace the functions specified infunction-list. This list can be changed at run timeby the set_ftrace_notrace file in the debugfstracing directory.ftrace_graph_filter=[function-list][FTRACE] Limit the top level callers functions tracedby the function graph tracer at boot up.function-list is a comma separated list of functionsthat can be changed at run time by theset_graph_function file in the debugfs tracing directory.gamecon.map[2|3]=[HW,JOY] Multisystem joystick and NES/SNES/PSX padsupport via parallel port (up to 5 devices per port)Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>See also Documentation/input/joystick-parport.txtgamma=[HW,DRM]gart_fix_e820= [X86_64] disable the fix e820 for K8 GARTFormat: off | ondefault: ongcov_persist=[GCOV] When non-zero (default), profiling data forkernel modules is saved and remains accessible viadebugfs, even when the module is unloaded/reloaded.When zero, profiling data is discarded and associateddebugfs files are removed at module unload time.gpt[EFI] Forces disk with valid GPT signature butinvalid Protective MBR to be treated as GPT.hashdist=[KNL,NUMA] Large hashes allocated during bootare distributed across NUMA nodes. Defaults onfor 64bit NUMA, off otherwise.Format: 0 | 1 (for off | on)hcl=[IA-64] SGI's Hardware Graph compatibility layerhd=[EIDE] (E)IDE hard drive subsystem geometryFormat: <cyl>,<head>,<sect>hest_disable[ACPI]Disable Hardware Error Source Table (HEST) support;corresponding firmware-first mode error processinglogic will be disabled.highmem=nn[KMG][KNL,BOOT] forces the highmem zone to have an exactsize of <nn>. This works even on boxes that have nohighmem otherwise. This also works to reduce highmemsize on bigger boxes.highres=[KNL] Enable/disable high resolution timer mode.Valid parameters: "on", "off"Default: "on"hisax=[HW,ISDN]See Documentation/isdn/README.HiSax.hlt[BUGS=ARM,SH]hpet=[X86-32,HPET] option to control HPET usageFormat: { enable (default) | disable | force |verbose }disable: disable HPET and use PIT insteadforce: allow force enabled of undocumented chips (ICH4,VIA, nVidia)verbose: show contents of HPET registers during setuphugepages=[HW,X86-32,IA-64] HugeTLB pages to allocate at boot.hugepagesz=[HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.On x86-64 and powerpc, this option can be specifiedmultiple times interleaved with hugepages= to reservehuge pages of different sizes. Valid pages sizes onx86-64 are 2M (when the CPU supports "pse") and 1G(when the CPU supports the "pdpe1gb" cpuinfo flag)Note that 1GB pages can only be allocated at boot timeusing hugepages= and not freed afterwards.hvc_iucv=[S390] Number of z/VM IUCV hypervisor console (HVC) terminal devices. Valid values: 0..8hvc_iucv_allow=[S390] Comma-separated list of z/VM user IDs. If specified, z/VM IUCV HVC accepts connections from listed z/VM user IDs only.keep_bootcon[KNL]Do not unregister boot console at start. This is onlyuseful for debugging when something happens in the windowbetween unregistering the boot console and initializingthe real console.i2c_bus=[HW] Override the default board specific I2C bus speed or register an additional I2C bus that is not registered from board initialization code. Format: <bus_id>,<clkrate>i8042.debug[HW] Toggle i8042 debug modei8042.direct[HW] Put keyboard port into non-translated modei8042.dumbkbd[HW] Pretend that controller can only read data from keyboard and cannot control its state (Don't attempt to blink the leds)i8042.noaux[HW] Don't check for auxiliary (== mouse) porti8042.nokbd[HW] Don't check/create keyboard porti8042.noloop[HW] Disable the AUX Loopback command while probing for the AUX porti8042.nomux[HW] Don't check presence of an active multiplexing controlleri8042.nopnp[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX controllersi8042.notimeout[HW] Ignore timeout condition signalled by conrolleri8042.reset[HW] Reset the controller during init and cleanupi8042.unlock[HW] Unlock (ignore) the keylocki810=[HW,DRM]i8k.ignore_dmi[HW] Continue probing hardware even if DMI dataindicates that the driver is running on unsupportedhardware.i8k.force[HW] Activate i8k driver even if SMM BIOS signaturedoes not match list of supported models.i8k.power_status[HW] Report power status in /proc/i8k(disabled by default)i8k.restricted[HW] Allow controlling fans only if SYS_ADMINcapability is set.icn=[HW,ISDN]Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]ide-core.nodma=[HW] (E)IDE subsystemFormat: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr.cdrom .chs .ignore_cable are additional optionsSee Documentation/ide/ide.txt.ide-pci-generic.all-generic-ide [HW] (E)IDE subsystemClaim all unknown PCI IDE storage controllers.idle=[X86]Format: idle=poll, idle=mwait, idle=halt, idle=nomwaitPoll forces a polling idle loop that can slightlyimprove the performance of waking up a idle CPU, butwill use a lot of power and make the system run hot.Not recommended.idle=mwait: On systems which support MONITOR/MWAIT butthe kernel chose to not use it because it doesn't saveas much power as a normal idle loop, use theMONITOR/MWAIT idle loop anyways. Performance should bethe same as idle=poll.idle=halt: Halt is forced to be used for CPU idle.In such case C2/C3 won't be used again.idle=nomwait: Disable mwait for CPU C-statesignore_loglevel[KNL]Ignore loglevel setting - this will print /all/kernel messages to the console. Useful for debugging.ihash_entries=[KNL]Set number of hash buckets for inode cache.ima_audit=[IMA]Format: { "0" | "1" }0 -- integrity auditing messages. (Default)1 -- enable informational integrity auditing messages.ima_hash=[IMA]Format: { "sha1" | "md5" }default: "sha1"ima_tcb[IMA]Load a policy which meets the needs of the TrustedComputing Base. This means IMA will measure allprograms exec'd, files mmap'd for exec, and all filesopened for read by uid=0.init=[KNL]Format: <full_path>Run specified binary instead of /sbin/init as initprocess.initcall_debug[KNL] Trace initcalls as they are executed. Usefulfor working out where the kernel is dying duringstartup.initrd=[BOOT] Specify the location of the initial ramdiskinport.irq=[HW] Inport (ATI XL and Microsoft) busmouse driverFormat: <irq>intel_iommu=[DMAR] Intel IOMMU driver (DMAR) optiononEnable intel iommu driver.offDisable intel iommu driver.igfx_off [Default Off]By default, gfx is mapped as normal device. If a gfxdevice has a dedicated DMAR unit, the DMAR unit isbypassed by not enabling DMAR with this option. Inthis case, gfx device will use physical address forDMA.forcedac [x86_64]With this option iommu will not optimize to lookfor io virtual address below 32 bit forcing dualaddress cycle on pci bus for cards supporting greaterthan 32 bit addressing. The default is to lookfor translation below 32 bit and if not availablethen look in the higher range.strict [Default Off]With this option on every unmap_single operation willresult in a hardware IOTLB flush operation as opposedto batching them for performance.sp_off [Default Off]By default, super page will be supported if Intel IOMMUhas the capability. With this option, super page willnot be supported.intremap=[X86-64, Intel-IOMMU]Format: { on (default) | off | nosid }onenable Interrupt Remapping (default)offdisable Interrupt Remappingnosiddisable Source ID checkinginttest=[IA64]iomem=Disable strict checking of access to MMIO memorystrictregions from userspace.relaxediommu=[x86]offforcenoforcebiomergepanicnopanicmergenomergeforcesacsoftpt[x86, IA64]io7=[HW] IO7 for Marvel based alpha systemsSee comment before marvel_specify_io7 inarch/alpha/kernel/core_marvel.c.io_delay=[X86] I/O delay method0x80Standard port 0x80 based delay0xedAlternate port 0xed based delay (needed on some systems)udelaySimple two microseconds delaynoneNo delayip=[IP_PNP]See Documentation/filesystems/nfs/nfsroot.txt.ip2=[HW] Set IO/IRQ pairs for up to 4 IntelliPort boardsSee comment before ip2_setup() indrivers/char/ip2/ip2base.c.irqfixup[HW]When an interrupt is not handled search all handlersfor it. Intended to get systems with badly brokenfirmware running.irqpoll[HW]When an interrupt is not handled search all handlersfor it. Also check all handlers each timerinterrupt. Intended to get systems with badly brokenfirmware running.isapnp=[ISAPNP]Format: <RDP>,<reset>,<pci_scan>,<verbosity>isolcpus=[KNL,SMP] Isolate CPUs from the general scheduler.Format:<cpu number>,...,<cpu number>or<cpu number>-<cpu number>(must be a positive range in ascending order)or a mixture<cpu number>,...,<cpu number>-<cpu number>This option can be used to specify one or more CPUsto isolate from the general SMP balancing and schedulingalgorithms. You can move a process onto or off an"isolated" CPU via the CPU affinity syscalls or cpuset.<cpu number> begins at 0 and the maximum value is"number of CPUs in system - 1".This option is the preferred way to isolate CPUs. Thealternative -- manually setting the CPU mask of alltasks in the system -- can cause problems andsuboptimal load balancer performance.iucv=[HW,NET]js=[HW,JOY] Analog joystickSee Documentation/input/joystick.txt.keepinitrd[HW,ARM]kernelcore=nn[KMG][KNL,X86,IA-64,PPC] This parameterspecifies the amount of memory usable by the kernelfor non-movable allocations. The requested amount isspread evenly throughout all nodes in the system. Theremaining memory in each node is used for Movablepages. In the event, a node is too small to have bothkernelcore and Movable pages, kernelcore pages willtake priority and other nodes will have a larger numberof kernelcore pages. The Movable zone is used for theallocation of pages that may be reclaimed or movedby the page migration subsystem. This means thatHugeTLB pages may not be allocated from this zone.Note that allocations like PTEs-from-HighMem stilluse the HighMem zone if it exists, and the Normalzone if it does not.kgdbdbgp=[KGDB,HW] kgdb over EHCI usb debug port.Format: <Controller#>[,poll interval]The controller # is the number of the ehci usb debugport as it is probed via PCI. The poll interval isoptional and is the number seconds in betweeneach poll cycle to the debug port in case you needthe functionality for interrupting the kernel withgdb or control-c on the dbgp connection. Whennot using this parameter you use sysrq-g to break intothe kernel debugger.kgdboc=[KGDB,HW] kgdb over consoles.Requires a tty driver that supports console polling,or a supported polling keyboard driver (non-usb). Serial only format: <serial_device>[,baud] keyboard only format: kbd keyboard and serial format: kbd,<serial_device>[,baud]Optional Kernel mode setting: kms, kbd format: kms,kbd kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]kgdbwait[KGDB] Stop kernel execution and enter thekernel debugger at the earliest opportunity.kmac=[MIPS] korina ethernet MAC address.Configure the RouterBoard 532 series on-chipEthernet adapter MAC address.kmemleak=[KNL] Boot-time kmemleak enable/disableValid arguments: on, offDefault: onkstack=N[X86] Print N words from the kernel stackin oops dumps.kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.Default is 0 (don't ignore, but inject #GP)kvm.oos_shadow=[KVM] Disable out-of-sync shadow paging.Default is 1 (enabled)kvm.mmu_audit=[KVM] This is a R/W parameter which allows auditKVM MMU at runtime.Default is 0 (off)kvm-amd.nested=[KVM,AMD] Allow nested virtualization in KVM/SVM.Default is 1 (enabled)kvm-amd.npt=[KVM,AMD] Disable nested paging (virtualized MMU)for all guests.Default is 1 (enabled) if in 64bit or 32bit-PAE modekvm-intel.bypass_guest_pf=[KVM,Intel] Disables bypassing of guest page faultson Intel chips. Default is 1 (enabled)kvm-intel.ept=[KVM,Intel] Disable extended page tables(virtualized MMU) support on capable Intel chips.Default is 1 (enabled)kvm-intel.emulate_invalid_guest_state=[KVM,Intel] Enable emulation of invalid guest statesDefault is 0 (disabled)kvm-intel.flexpriority=[KVM,Intel] Disable FlexPriority feature (TPR shadow).Default is 1 (enabled)kvm-intel.unrestricted_guest=[KVM,Intel] Disable unrestricted guest feature(virtualized real and unpaged mode) on capableIntel chips. Default is 1 (enabled)kvm-intel.vpid=[KVM,Intel] Disable Virtual Processor Identificationfeature (tagged TLBs) on capable Intel chips.Default is 1 (enabled)l2cr=[PPC]l3cr=[PPC]lapic[X86-32,APIC] Enable the local APIC even if BIOSdisabled it.lapic_timer_c2_ok[X86,APIC] trust the local apic timerin C2 power state.libata.dma=[LIBATA] DMA controllibata.dma=0 Disable all PATA and SATA DMAlibata.dma=1 PATA and SATA Disk DMA onlylibata.dma=2 ATAPI (CDROM) DMA onlylibata.dma=4 Compact Flash DMA only Combinations also work, so libata.dma=3 enables DMAfor disks and CDROMs, but not CFs.libata.ignore_hpa=[LIBATA] Ignore HPA limitlibata.ignore_hpa=0 keep BIOS limits (default)libata.ignore_hpa=1 ignore limits, using full disklibata.noacpi[LIBATA] Disables use of ACPI in libata suspend/resumewhen set.Format: <int>libata.force=[LIBATA] Force configurations. The format is commaseparated list of "[ID:]VAL" where ID isPORT[.DEVICE]. PORT and DEVICE are decimal numbersmatching port, link or device. Basically, it matchesthe ATA ID string printed on console by libata. Ifthe whole ID part is omitted, the last PORT and DEVICEvalues are used. If ID hasn't been specified yet, theconfiguration applies to all ports, links and devices.If only DEVICE is omitted, the parameter applies tothe port and all links and devices behind it. DEVICEnumber of 0 either selects the first device or thefirst fan-out link behind PMP device. It does notselect the host link. DEVICE number of 15 selects thehost link and device attached to it.The VAL specifies the configuration to force. As longas there's no ambiguity shortcut notation is allowed.For example, both 1.5 and 1.5G would work for 1.5Gbps.The following configurations can be forced.* Cable type: 40c, 80c, short40c, unk, ign or sata. Any ID with matching PORT is used.* SATA link speed limit: 1.5Gbps or 3.0Gbps.* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7]. udma[/][16,25,33,44,66,100,133] notation is also allowed.* [no]ncq: Turn on or off NCQ.* nohrst, nosrst, norst: suppress hard, soft and both resets.* dump_id: dump IDENTIFY data.If there are multiple matching configurations changingthe same attribute, the last one is used.memblock=debug[KNL] Enable memblock debug messages.load_ramdisk=[RAM] List of ramdisks to load from floppySee Documentation/blockdev/ramdisk.txt.lockd.nlm_grace_period=P [NFS] Assign grace period.Format: <integer>lockd.nlm_tcpport=N[NFS] Assign TCP port.Format: <integer>lockd.nlm_timeout=T[NFS] Assign timeout value.Format: <integer>lockd.nlm_udpport=M[NFS] Assign UDP port.Format: <integer>logibm.irq=[HW,MOUSE] Logitech Bus Mouse DriverFormat: <irq>loglevel=All Kernel Messages with a loglevel smaller than theconsole loglevel will be printed to the console. It canalso be changed with klogd or other programs. Theloglevels are defined as follows:0 (KERN_EMERG)system is unusable1 (KERN_ALERT)action must be taken immediately2 (KERN_CRIT)critical conditions3 (KERN_ERR)error conditions4 (KERN_WARNING)warning conditions5 (KERN_NOTICE)normal but significant condition6 (KERN_INFO)informational7 (KERN_DEBUG)debug-level messageslog_buf_len=n[KMG]Sets the size of the printk ring buffer,in bytes. n must be a power of two. The defaultsize is set in the kernel config file.logo.nologo[FB] Disables display of the built-in Linux logo.This may be used to provide more screen space forkernel log messages and is useful when debuggingkernel boot problems.lp=0[LP]Specify parallel ports to use, e.g,lp=port[,port...]lp=none,parport0 (lp0 not configured, lp1 useslp=resetfirst parallel port). 'lp=0' disables thelp=autoprinter driver. 'lp=reset' (which can bespecified in addition to the ports) causesattached printers to be reset. Usinglp=port1,port2,... specifies the parallel portsto associate lp devices with, starting withlp0. A port specification may be 'none' to skipthat lp device, or a parport name such as'parport0'. Specifying 'lp=auto' instead of aport specification list means that device IDsfrom each port should be examined, to see ifan IEEE 1284-compliant printer is attached; ifso, the driver will manage that printer.See also header of drivers/char/lp.c.lpj=n[KNL]Sets loops_per_jiffy to given constant, thus avoidingtime-consuming boot-time autodetection (up to 250 ms perCPU). 0 enables autodetection (default). To determinethe correct value for your kernel, boot with normalautodetection and see what value is printed. Note thaton SMP systems the preset will be applied to all CPUs,which is likely to cause problems if your CPUs needsignificantly divergent settings. An incorrect valuewill cause delays in the kernel to be wrong, leading tounpredictable I/O errors and other breakage. Althoughunlikely, in the extreme case this might damage yourhardware.ltpc=[NET]Format: <io>,<irq>,<dma>machvec=[IA64] Force the use of a particular machine-vector(machvec) in a generic kernel.Example: machvec=hpzx1_swiotlbmachtype=[Loongson] Share the same kernel image file between different yeeloong laptop.Example: machtype=lemote-yeeloong-2f-7inchmax_addr=nn[KMG][KNL,BOOT,ia64] All physical memory greaterthan or equal to this physical address is ignored.maxcpus=[SMP] Maximum number of processors thatan SMP kernelshould make use of. maxcpus=n : n >= 0 limits thekernel to using 'n' processors. n=0 is a special case,it is equivalent to "nosmp", which also disablesthe IO APIC.max_loop=[LOOP] Maximum number of loopback devices that canbe mountedFormat: <1-256>mcatest=[IA-64]mce[X86-32] Machine Check Exceptionmce=option[X86-64] See Documentation/x86/x86_64/boot-options.txtmd=[HW] RAID subsystems devices and levelSee Documentation/md.txt.mdacon=[MDA]Format: <first>,<last>Specifies range of consoles to be captured by the MDA.mem=nn[KMG][KNL,BOOT] Force usage of a specific amount of memoryAmount of memory to be used when the kernel is not ableto see the whole system memory or for test.[X86-32] Use together with memmap= to avoid physicaladdress space collisions. Without memmap= PCI devicescould be placed at addresses belonging to unused RAM.mem=nopentium[BUGS=X86-32] Disable usage of 4MB pages for kernelmemory.memchunk=nn[KMG][KNL,SH] Allow user to override the default size forper-device physically contiguous DMA buffers.memmap=exactmap[KNL,X86] Enable setting of an exactE820 memory map, as specified by the user.Such memmap=exactmap lines can be constructed based onBIOS output or other requirements. See the memmap=nn@ssoption description.memmap=nn[KMG]@ss[KMG][KNL] Force usage of a specific region of memoryRegion of memory to be used, from ss to ss+nn.memmap=nn[KMG]#ss[KMG][KNL,ACPI] Mark specific memory as ACPI data.Region of memory to be used, from ss to ss+nn.memmap=nn[KMG]$ss[KMG][KNL,ACPI] Mark specific memory as reserved.Region of memory to be used, from ss to ss+nn.Example: Exclude memory from 0x18690000-0x1869ffff memmap=64K$0x18690000 or memmap=0x10000$0x18690000memory_corruption_check=0/1 [X86]Some BIOSes seem to corrupt the first 64k ofmemory when doing things like suspend/resume.Setting this option will scan the memorylooking for corruption. Enabling this willboth detect corruption and prevent the kernelfrom using the memory being corrupted.However, its intended as a diagnostic tool; ifrepeatable BIOS-originated corruption alwaysaffects the same memory, you can use memmap=to prevent the kernel from using that memory.memory_corruption_check_size=size [X86]By default it checks for corruption in the low64k, making this memory unavailable for normaluse. Use this parameter to scan forcorruption in more or less memory.memory_corruption_check_period=seconds [X86]By default it checks for corruption every 60seconds. Use this parameter to check at someother rate. 0 disables periodic checking.memtest=[KNL,X86] Enable memtestFormat: <integer>default : 0 <disable>Specifies the number of memtest passes to beperformed. Each pass selects another testpattern from a given set of patterns. Memtestfills the memory with this pattern, validatesmemory contents and reserves bad memoryregions that are detected.meye.*=[HW] Set MotionEye Camera parametersSee Documentation/video4linux/meye.txt.mfgpt_irq=[IA-32] Specify the IRQ to use for theMulti-Function General Purpose Timers on AMD Geodeplatforms.mfgptfix[X86-32] Fix MFGPT timers on AMD Geode platforms whenthe BIOS has incorrectly applied a workaround. TinyBIOSversion 0.98 is known to be affected, 0.99 fixes theproblem by letting the user disable the workaround.mga=[HW,DRM]min_addr=nn[KMG][KNL,BOOT,ia64] All physical memory below thisphysical address is ignored.mini2440=[ARM,HW,KNL]Format:[0..2][b][c][t]Default: "0tb"MINI2440 configuration specification:0 - The attached screen is the 3.5" TFT1 - The attached screen is the 7" TFT2 - The VGA Shield is attached (1024x768)Leaving out the screen size parameter will not loadthe TFT driver, and the framebuffer will be leftunconfigured.b - Enable backlight. The TFT backlight pin will belinked to the kernel VESA blanking code and a GPIOLED. This parameter is not necessary when using theVGA shield.c - Enable the s3c camera interface.t - Reserved for enabling touchscreen support. Thetouchscreen support is not enabled in the mainstreamkernel as of 2.6.30, a preliminary port can be foundin the "bleeding edge" mini2440 support kernel athttp://repo.or.cz/w/linux-2.6/mini2440.gitmminit_loglevel=[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, thisparameter allows control of the logging verbosity forthe additional memory initialisation checks. A valueof 0 disables mminit logging and a level of 4 willlog everything. Information is printed at KERN_DEBUGso loglevel=8 may also need to be specified.mousedev.tap_time=[MOUSE] Maximum time between finger touching andleaving touchpad surface for touch to be considereda tap and be reported as a left button click (fortouchpads working in absolute mode only).Format: <msecs>mousedev.xres=[MOUSE] Horizontal screen resolution, used for devicesreporting absolute coordinates, such as tabletsmousedev.yres=[MOUSE] Vertical screen resolution, used for devicesreporting absolute coordinates, such as tabletsmovablecore=nn[KMG][KNL,X86,IA-64,PPC] This parameteris similar to kernelcore except it specifies theamount of memory used for migratable allocations.If both kernelcore and movablecore is specified,then kernelcore will be at *least* the specifiedvalue but may be more. If movablecore on its ownis specified, the administrator must be carefulthat the amount of memory usable for all allocationsis not too small.MTD_Partition=[MTD]Format: <name>,<region-number>,<size>,<offset>MTD_Region=[MTD] Format:<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]mtdparts=[MTD]See drivers/mtd/cmdlinepart.c.multitce=off[PPC] This parameter disables the use of the pSeriesfirmware feature for updating multiple TCE entriesat a time.onenand.bdry=[HW,MTD] Flex-OneNAND Boundary ConfigurationFormat: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]boundary - index of last SLC block on Flex-OneNAND. The remaining blocks are configured as MLC blocks.lock - Configure if Flex-OneNAND boundary should be locked. Once locked, the boundary cannot be changed. 1 indicates lock status, 0 indicates unlock status.mtdset=[ARM]ARM/S3C2412 JIVE boot controlSee arch/arm/mach-s3c2412/mach-jive.cmtouchusb.raw_coordinates=[HW] Make the MicroTouch USB driver use raw coordinates('y', default) or cooked coordinates ('n')mtrr_chunk_size=nn[KMG] [X86]used for mtrr cleanup. It is largest continuous chunkthat could hold holes aka. UC entries.mtrr_gran_size=nn[KMG] [X86]Used for mtrr cleanup. It is granularity of mtrr block.Default is 1.Large value could prevent small alignment fromusing up MTRRs.mtrr_spare_reg_nr=n [X86]Format: <integer>Range: 0,7 : spare reg numberDefault : 1Used for mtrr cleanup. It is spare mtrr entries number.Set to 2 or more if your graphical card needs more.n2=[NET] SDL Inc. RISCom/N2 synchronous serial cardnetdev=[NET] Network devices parametersFormat: <irq>,<io>,<mem_start>,<mem_end>,<name>Note that mem_start is often overloaded to meansomething different and driver-specific.This usage is only documented in each driver sourcefile if at all.nf_conntrack.acct=[NETFILTER] Enable connection tracking flow accounting0 to disable accounting1 to enable accountingDefault value is 0.nfsaddrs=[NFS] Deprecated. Use ip= instead.See Documentation/filesystems/nfs/nfsroot.txt.nfsroot=[NFS] nfs root filesystem for disk-less boxes.See Documentation/filesystems/nfs/nfsroot.txt.nfsrootdebug[NFS] enable nfsroot debugging messages.See Documentation/filesystems/nfs/nfsroot.txt.nfs.callback_tcpport=[NFS] set the TCP port on which the NFSv4 callbackchannel should listen.nfs.cache_getent=[NFS] sets the pathname to the program which is usedto update the NFS client cache entries.nfs.cache_getent_timeout=[NFS] sets the timeout after which an attempt toupdate a cache entry is deemed to have failed.nfs.idmap_cache_timeout=[NFS] set the maximum lifetime for idmapper cacheentries.nfs.enable_ino64=[NFS] enable 64-bit inode numbers.If zero, the NFS client will fake up a 32-bit inodenumber for the readdir() and stat() syscalls insteadof returning the full 64-bit number.The default is to return 64-bit inode numbers.nfs.nfs4_disable_idmapping=[NFSv4] When set, this option disables the NFSv4idmapper on the client, but only if the mountis using the 'sec=sys' security flavour. This maymake migration from legacy NFSv2/v3 systems easierprovided that the server has the appropriate support.The default is to always enable NFSv4 idmapping.nmi_debug=[KNL,AVR32,SH] Specify one or more actions to takewhen a NMI is triggered.Format: [state][,regs][,debounce][,die]nmi_watchdog=[KNL,BUGS=X86] Debugging features for SMP kernelsFormat: [panic,][nopanic,][num]Valid num: 00 - turn nmi_watchdog offWhen panic is specified, panic when an NMI watchdogtimeout occurs (or 'nopanic' to override the oppositedefault).This is useful when you use a panic=... timeout andneed the box quickly up again.netpoll.carrier_timeout=[NET] Specifies amount of time (in seconds) thatnetpoll should wait for a carrier. By default netpollwaits 4 seconds.no387[BUGS=X86-32] Tells the kernel to use the 387 mathsemulation library even if a 387 maths coprocessoris present.no_console_suspend[HW] Never suspend the consoleDisable suspending of consoles during suspend andhibernate operations. Once disabled, debuggingmessages can reach various consoles while the restof the system is being put to sleep (ie, whiledebugging driver suspend/resume hooks). This maynot work reliably with all consoles, but is knownto work with serial and VGA consoles.noaliencache[MM, NUMA, SLAB] Disables the allocation of aliencaches in the slab allocator. Saves per-node memory,but will impact performance.noalign[KNL,ARM]noapic[SMP,APIC] Tells the kernel to not make use of anyIOAPICs that may be present in the system.noautogroupDisable scheduler automatic task group creation.nobats[PPC] Do not use BATs for mapping kernel lowmemon "Classic" PPC cores.nocache[ARM]noclflush[BUGS=X86] Don't use the CLFLUSH instructionnodelayacct[KNL] Disable per-task delay accountingnodisconnect[HW,SCSI,M68K] Disables SCSI disconnects.nodsp[SH] Disable hardware DSP at boot time.noefi[X86] Disable EFI runtime services support.noexec[IA-64]noexec[X86]On X86-32 available only on PAE configured kernels.noexec=on: enable non-executable mappings (default)noexec=off: disable non-executable mappingsnosmep[X86]Disable SMEP (Supervisor Mode Execution Protection)even if it is supported by processor.noexec32[X86-64]This affects only 32-bit executables.noexec32=on: enable non-executable mappings (default)read doesn't imply executable mappingsnoexec32=off: disable non-executable mappingsread implies executable mappingsnofpu[SH] Disable hardware FPU at boot time.nofxsr[BUGS=X86-32] Disables x86 floating point extendedregister save and restore. The kernel will only savelegacy floating-point registers on task switch.noxsave[BUGS=X86] Disables x86 extended register state saveand restore using xsave. The kernel will fallback toenabling legacy floating-point and sse state.nohlt[BUGS=ARM,SH] Tells the kernel that the sleep(SH) orwfi(ARM) instruction doesn't work correctly and not touse it. This is also useful when using JTAG debugger.no-hlt[BUGS=X86-32] Tells the kernel that the hltinstruction doesn't work correctly and not touse it.no_file_capsTells the kernel not to honor file capabilities. Theonly way then for a file to be executed with privilegeis to be setuid root or executed by root.nohalt[IA-64] Tells the kernel not to use the power savingfunction PAL_HALT_LIGHT when idle. This increasespower-consumption. On the positive side, it reducesinterrupt wake-up latency, which may improve performancein certain environments such as networked servers orreal-time systems.nohz=[KNL] Boottime enable/disable dynamic ticksValid arguments: on, offDefault: onnoiotrap[SH] Disables trapped I/O port accesses.noirqdebug[X86-32] Disables the code which attempts to detect anddisable unhandled interrupt sources.no_timer_check[X86,APIC] Disables the code which tests forbroken timer IRQ sources.noisapnp[ISAPNP] Disables ISA PnP code.noinitrd[RAM] Tells the kernel not to load any configuredinitial RAM disk.nointremap[X86-64, Intel-IOMMU] Do not enable interruptremapping.[Deprecated - use intremap=off]nointroute[IA-64]nojitter[IA64] Disables jitter checking for ITC timers.no-kvmclock[X86,KVM] Disable paravirtualized KVM clock driverno-kvmapf[X86,KVM] Disable paravirtualized asynchronous pagefault handling.nolapic[X86-32,APIC] Do not enable or use the local APIC.nolapic_timer[X86-32,APIC] Do not use the local APIC timer.noltlbs[PPC] Do not use large page/tlb entries for kernellowmem mapping on PPC40x.nomca[IA-64] Disable machine check abort handlingnomce[X86-32] Machine Check Exceptionnomfgpt[X86-32] Disable Multi-Function General PurposeTimer usage (for AMD Geode machines).nopat[X86] Disable PAT (page attribute table extension ofpagetables) support.norandmapsDon't use address space randomization. Equivalent toecho 0 > /proc/sys/kernel/randomize_va_spacenoreplace-paravirt[X86,IA-64,PV_OPS] Don't patch paravirt_opsnoreplace-smp[X86-32,SMP] Don't replace SMP instructionswith UP alternativesnoresidual[PPC] Don't use residual data on PReP machines.noresume[SWSUSP] Disables resume and restores original swapspace.no-scroll[VGA] Disables scrollback.This is required for the Braillex ib80-piezo Braillereader made by F.H. Papenmeier (Germany).nosbagart[IA-64]nosep[BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.nosmp[SMP] Tells an SMP kernel to act as a UP kernel,and disable the IO APIC. legacy for "maxcpus=0".nosoftlockup[KNL] Disable the soft-lockup detector.nosync[HW,M68K] Disables sync negotiation for all devices.notsc[BUGS=X86-32] Disable Time Stamp Counternousb[USB] Disable the USB subsystemnowatchdog[KNL] Disable the lockup detector (NMI watchdog).nowb[ARM]nox2apic[X86-64,APIC] Do not enable x2APIC mode.nptcg=[IA64] Override max number of concurrent global TLBpurges which is reported from either PAL_VM_SUMMARY orSAL PALO.nr_cpus=[SMP] Maximum number of processors thatan SMP kernelcould support. nr_cpus=n : n >= 1 limits the kernel tosupporting 'n' processors. Later in runtime you can notuse hotplug cpu feature to put more cpu back to online.just like you compile the kernel NR_CPUS=nnr_uarts=[SERIAL] maximum number of UARTs to be registered.numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.one of ['zone', 'node', 'default'] can be specifiedThis can be set from sysctl after boot.See Documentation/sysctl/vm.txt for details.ohci1394_dma=early[HW] enable debugging via the ohci1394 driver.See Documentation/debugging-via-ohci1394.txt for moreinfo.olpc_ec_timeout= [OLPC] ms delay when issuing EC commandsRather than timing out after 20 ms if an ECcommand is not properly ACKed, override the lengthof the timeout. We have interrupts disabled whilewaiting for the ACK, so if this is set too highinterrupts *may* be lost!omap_mux=[OMAP] Override bootloader pin multiplexing.Format: <mux_mode0.mode_name=value>...For example, to override I2C bus2:omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100oprofile.timer=[HW]Use timer interrupt instead of performance countersoprofile.cpu_type=Force an oprofile cpu typeThis might be useful if you have an older oprofileuserland or if you want common events.Format: { arch_perfmon }arch_perfmon: [X86] Force use of architecturalperfmon on Intel CPUs instead of theCPU specific event set.oops=panicAlways panic on oopses. Default is to just kill theprocess, but there is a small probability ofdeadlocking the machine.This will also cause panics on machine check exceptions.Useful together with panic=30 to trigger a reboot.OSS[HW,OSS]See Documentation/sound/oss/oss-parameters.txtpanic=[KNL] Kernel behaviour on panic: delay <timeout>seconds before rebootingFormat: <timeout>parkbd.port=[HW] Parallel port number the keyboard adapter isconnected to, default is 0.Format: <parport#>parkbd.mode=[HW] Parallel port keyboard adapter mode of operation,0 for XT, 1 for AT (default is AT).Format: <mode>parport=[HW,PPT] Specify parallel ports. 0 disables.Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }Use 'auto' to force the driver to use anyIRQ/DMA settings detected (the default is toignore detected IRQ/DMA settings because ofpossible conflicts). You can specify the baseaddress, IRQ, and DMA settings; IRQ and DMAshould be numbers, or 'auto' (for using detectedsettings on that particular port), or 'nofifo'(to avoid using a FIFO even if it is detected).Parallel ports are assigned in the order theyare specified on the command line, startingwith parport0.parport_init_mode=[HW,PPT]Configure VIA parallel port to operate ina specific mode. This is necessary on Pegasoscomputer where firmware has no options for settingup parallel port mode and sets it to spp.Currently this function knows 686a and 8231 chips.Format: [spp|ps2|epp|ecp|ecpepp]pause_on_oops=Halt all CPUs after the first oops has been printed forthe specified number of seconds. This is to be used ifyour oopses keep scrolling off the screen.pcbit=[HW,ISDN]pcd.[PARIDE]See header of drivers/block/paride/pcd.c.See also Documentation/blockdev/paride.txt.pci=option[,option...][PCI] various PCI subsystem options:earlydump[X86] dump PCI config space before the kernel changes anythingoff[X86] don't probe for the PCI busbios[X86-32] force use of PCI BIOS, don't accessthe hardware directly. Use this if your machinehas a non-standard PCI host bridge.nobios[X86-32] disallow use of PCI BIOS, only directhardware access methods are allowed. Use thisif you experience crashes upon bootup and yoususpect they are caused by the BIOS.conf1[X86] Force use of PCI ConfigurationMechanism 1.conf2[X86] Force use of PCI ConfigurationMechanism 2.noaer[PCIE] If the PCIEAER kernel config parameter isenabled, this kernel boot option can be used todisable the use of PCIE advanced error reporting.nodomains[PCI] Disable support for multiple PCIroot domains (aka PCI segments, in ACPI-speak).nommconf[X86] Disable use of MMCONFIG for PCIConfigurationcheck_enable_amd_mmconf [X86] check for and enableproperly configured MMIO access to PCIconfig space on AMD family 10h CPUnomsi[MSI] If the PCI_MSI kernel config parameter isenabled, this kernel boot option can be used todisable the use of MSI interrupts system-wide.noioapicquirk[APIC] Disable all boot interrupt quirks.Safety option to keep boot IRQs enabled. Thisshould never be necessary.ioapicreroute[APIC] Enable rerouting of boot IRQs to theprimary IO-APIC for bridges that cannot disableboot IRQs. This fixes a source of spurious IRQswhen the system masks IRQs.noioapicreroute[APIC] Disable workaround that uses theboot IRQ equivalent of an IRQ that connects toa chipset where boot IRQs cannot be disabled.The opposite of ioapicreroute.biosirq[X86-32] Use PCI BIOS calls to get the interruptrouting table. These calls are known to be buggyon several machines and they hang the machinewhen used, but on other computers it's the onlyway to get the interrupt routing table. Trythis option if the kernel is unable to allocateIRQs or discover secondary PCI buses on yourmotherboard.rom[X86] Assign address space to expansion ROMs.Use with caution as certain devices shareaddress decoders between ROMs and otherresources.norom[X86] Do not assign address space toexpansion ROMs that do not already haveBIOS assigned address ranges.nobar[X86] Do not assign address space to theBARs that weren't assigned by the BIOS.irqmask=0xMMMM[X86] Set a bit mask of IRQs allowed to beassigned automatically to PCI devices. You canmake the kernel exclude IRQs of your ISA cardsthis way.pirqaddr=0xAAAAA[X86] Specify the physical addressof the PIRQ table (normally generatedby the BIOS) if it is outside theF0000h-100000h range.lastbus=N[X86] Scan all buses thru bus #N. Can beuseful if the kernel is unable to find yoursecondary buses and you want to tell itexplicitly which ones they are.assign-busses[X86] Always assign all PCI busnumbers ourselves, overridingwhatever the firmware may have done.usepirqmask[X86] Honor the possible IRQ mask storedin the BIOS $PIR table. This is needed onsome systems with broken BIOSes, notablysome HP Pavilion N5400 and Omnibook XE3notebooks. This will have no effect if ACPIIRQ routing is enabled.noacpi[X86] Do not use ACPI for IRQ routingor for PCI scanning.use_crs[X86] Use PCI host bridge window informationfrom ACPI. On BIOSes from 2008 or later, thisis enabled by default. If you need to use this,please report a bug.nocrs[X86] Ignore PCI host bridge windows from ACPI. If you need to use this, please report a bug.routeirqDo IRQ routing for all PCI devices.This is normally done in pci_enable_device(),so this option is a temporary workaroundfor broken drivers that don't call it.skip_isa_align[X86] do not align io start addr, so canhandle more pci cardsfirmware[ARM] Do not re-enumerate the bus but insteadjust use the configuration from thebootloader. This is currently used onIXP2000 systems where the bus has to beconfigured a certain way for adjunct CPUs.noearly[X86] Don't do any early type 1 scanning.This might help on some broken boards whichmachine check when some devices' config spaceis read. But various workarounds are disabledand some IOMMU drivers will not work.bfsortSort PCI devices into breadth-first order.This sorting is done to get a deviceorder compatible with older (<= 2.4) kernels.nobfsortDon't sort PCI devices into breadth-first order.cbiosize=nn[KMG]The fixed amount of bus space which isreserved for the CardBus bridge's IO window.The default value is 256 bytes.cbmemsize=nn[KMG]The fixed amount of bus space which isreserved for the CardBus bridge's memorywindow. The default value is 64 megabytes.resource_alignment=Format:[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]Specifies alignment and device to reassignaligned memory resources.If <order of align> is not specified,PAGE_SIZE is used as alignment.PCI-PCI bridge can be specified, if resourcewindows need to be expanded.ecrc=Enable/disable PCIe ECRC (transaction layerend-to-end CRC checking).bios: Use BIOS/firmware settings. This is thethe default.off: Turn ECRC offon: Turn ECRC on.reallocreallocate PCI resources if allocations done by BIOSare erroneous.pcie_aspm=[PCIE] Forcibly enable or disable PCIe Active State PowerManagement.offDisable ASPM.forceEnable ASPM even on devices that claim not to support it.WARNING: Forcing ASPM on may cause system lockups.pcie_ports=[PCIE] PCIe ports handling:autoAsk the BIOS whether or not to use native PCIe servicesassociated with PCIe ports (PME, hot-plug, AER). Usethem only if that is allowed by the BIOS.nativeUse native PCIe services associated with PCIe portsunconditionally.compatTreat PCIe ports as PCI-to-PCI bridges, disable the PCIeports driver.pcie_pme=[PCIE,PM] Native PCIe PME signaling options:nomsiDo not use MSI for native PCIe PME signaling (this makesall PCIe root ports use INTx for all services).pcmv=[HW,PCMCIA] BadgePAD 4pd.[PARIDE]See Documentation/blockdev/paride.txt.pdcchassis=[PARISC,HW] Disable/Enable PDC Chassis Status codes atboot time.Format: { 0 | 1 }See arch/parisc/kernel/pdc_chassis.cpercpu_alloc=Select which percpu first chunk allocator to use.Currently supported values are "embed" and "page".Archs may support subset or none of theselections.See comments in mm/percpu.c for details on eachallocator. This parameter is primarilyfor debuggingand performance comparison.pf.[PARIDE]See Documentation/blockdev/paride.txt.pg.[PARIDE]See Documentation/blockdev/paride.txt.pirq=[SMP,APIC] Manual mp-table setupSee Documentation/x86/i386/IO-APIC.txt.plip=[PPT,NET] Parallel port network linkFormat: { parport<nr> | timid | 0 }See also Documentation/parport.txt.pmtmr=[X86] Manual setup of pmtmr I/O Port. Override pmtimer IOPort with a hex value.e.g. pmtmr=0x508pnp.debug[PNP]Enable PNP debug messages. This depends on theCONFIG_PNP_DEBUG_MESSAGES option.pnpacpi=[ACPI]{ off }pnpbios=[ISAPNP]{ on | off | curr | res | no-curr | no-res }pnp_reserve_irq=[ISAPNP] Exclude IRQs for the autoconfigurationpnp_reserve_dma=[ISAPNP] Exclude DMAs for the autoconfigurationpnp_reserve_io=[ISAPNP] Exclude I/O ports for the autoconfigurationRanges are in pairs (I/O port base and size).pnp_reserve_mem=[ISAPNP] Exclude memory regions for theautoconfiguration.Ranges are in pairs (memory base and size).ports=[IP_VS_FTP] IPVS ftp helper moduleDefault is 21.Up to 8 (IP_VS_APP_MAX_PORTS) portsmay be specified.Format: <port>,<port>....print-fatal-signals=[KNL] debug: print fatal signalsIf enabled, warn about various signal handlingrelated application anomalies: too many signals,too many POSIX.1 timers, fatal signals causing acoredump - etc.If you hit the warning due to signal overflow,you might want to try "ulimit -i unlimited".default: off.printk.time=Show timing data prefixed to each printk message lineFormat: <bool> (1/Y/y=enable, 0/N/n=disable)processor.max_cstate=[HW,ACPI]Limit processor to maximum C-statemax_cstate=9 overrides any DMI blacklist limit.processor.nocst[HW,ACPI]Ignore the _CST method to determine C-states,instead using the legacy FADT methodprofile=[KNL] Enable kernel profiling via /proc/profileFormat: [schedule,]<number>Param: "schedule" - profile schedule points.Param: <number> - step/bucket size as a power of 2 forstatistical time based profiling.Param: "sleep" - profile D-state sleeping (millisecs).Requires CONFIG_SCHEDSTATSParam: "kvm" - profile VM exits.prompt_ramdisk=[RAM] List of RAM disks to prompt for floppy diskbefore loading.See Documentation/blockdev/ramdisk.txt.psmouse.proto=[HW,MOUSE] Highest PS2 mouse protocol extension toprobe for; one of (bare|imps|exps|lifebook|any).psmouse.rate=[HW,MOUSE] Set desired mouse report rate, in reportsper second.psmouse.resetafter=[HW,MOUSE]Try to reset the device after so many bad packets(0 = never).psmouse.resolution=[HW,MOUSE] Set desired mouse resolution, in dpi.psmouse.smartscroll=[HW,MOUSE] Controls Logitech smartscroll autorepeat.0 = disabled, 1 = enabled (default).pt.[PARIDE]See Documentation/blockdev/paride.txt.pty.legacy_count=[KNL] Number of legacy pty's. Overwrites compiled-indefault number.quiet[KNL] Disable most log messagesr128=[HW,DRM]raid=[HW,RAID]See Documentation/md.txt.ramdisk_blocksize=[RAM]See Documentation/blockdev/ramdisk.txt.ramdisk_size=[RAM] Sizes of RAM disks in kilobytesSee Documentation/blockdev/ramdisk.txt.rcupdate.blimit=[KNL,BOOT]Set maximum number of finished RCU callbacks to processin one batch.rcupdate.qhimark=[KNL,BOOT]Set threshold of queuedRCU callbacks over which batch limiting is disabled.rcupdate.qlowmark=[KNL,BOOT]Set threshold of queued RCU callbacks below whichbatch limiting is re-enabled.rdinit=[KNL]Format: <full_path>Run specified binary instead of /init from the ramdisk,used for early userspace startup. See initrd.reboot=[BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting modeFormat: <reboot_mode>[,<reboot_mode2>[,...]]See arch/*/kernel/reboot.c or arch/*/kernel/process.crelax_domain_level=[KNL, SMP] Set scheduler's default relax_domain_level.See Documentation/cgroups/cpusets.txt.reserve=[KNL,BUGS] Force the kernel to ignore some iomem areareservetop=[X86-32]Format: nn[KMG]Reserves a hole at the top of the kernel virtualaddress space.reservelow=[X86]Format: nn[K]Set the amount of memory to reserve for BIOS atthe bottom of the address space.reset_devices[KNL] Force drivers to reset the underlying deviceduring initialization.resume=[SWSUSP]Specify the partition device for software suspendresume_offset=[SWSUSP]Specify the offset from the beginning of the partitiongiven by "resume=" at which the swap header is located,in <PAGE_SIZE> units (needed only for swap files).See Documentation/power/swsusp-and-swap-files.txthibernate=[HIBERNATION]noresumeDon't check if there's a hibernation imagepresent during boot.nocompressDon't compress/decompress hibernation images.retain_initrd[RAM] Keep initrd memory after extractionrhash_entries=[KNL,NET]Set number of hash buckets for route cacheriscom8=[HW,SERIAL]Format: <io_board1>[,<io_board2>[,...<io_boardN>]]ro[KNL] Mount root device read-only on bootroot=[KNL] Root filesystemrootdelay=[KNL] Delay (in seconds) to pause before attempting tomount the root filesystemrootflags=[KNL] Set root filesystem mount option stringrootfstype=[KNL] Set root filesystem typerootwait[KNL] Wait (indefinitely) for root device to show up.Useful for devices that are detected asynchronously(e.g. USB and MMC devices).rw[KNL] Mount root device read-write on bootS[KNL] Run init in single modesa1100ir[NET]See drivers/net/irda/sa1100_ir.c.sbni=[NET] Granch SBNI12 leased line adaptersched_debug[KNL] Enables verbose scheduler debug messages.security=[SECURITY] Choose a security module to enable at boot.If this boot parameter is not specified, only the firstsecurity module asking for security registration will beloaded. An invalid security module name will be treatedas if no module has been chosen.selinux=[SELINUX] Disable or enable SELinux at boot time.Format: { "0" | "1" }See security/selinux/Kconfig help text.0 -- disable.1 -- enable.Default value is set via kernel config option.If enabled at boot time, /selinux/disable can be usedlater to disable prior to initial policy load.apparmor=[APPARMOR] Disable or enable AppArmor at boot timeFormat: { "0" | "1" }See security/apparmor/Kconfig help text0 -- disable.1 -- enable.Default value is set via kernel config option.serialnumber[BUGS=X86-32]shapers=[NET]Maximal number of shapers.show_msr=[x86] show boot-time MSR settingsFormat: { <integer> }Show boot-time (BIOS-initialized) MSR settings.The parameter means the number of CPUs to show,for example 1 means boot CPU only.simeth=[IA-64]simscsi=slram=[HW,MTD]slub_debug[=options[,slabs]][MM, SLUB]Enabling slub_debug allows one to determine theculprit if slab objects become corrupted. Enablingslub_debug can create guard zones around objects andmay poison objects when not in use. Also tracks thelast alloc / free. For more information seeDocumentation/vm/slub.txt.slub_max_order= [MM, SLUB]Determines the maximum allowed order for slabs.A high setting may cause OOMs due to memoryfragmentation. For more information seeDocumentation/vm/slub.txt.slub_min_objects=[MM, SLUB]The minimum number of objects per slab. SLUB willincrease the slab order up to slub_max_order togenerate a sufficiently large slab able to containthe number of objects indicated. The higher the numberof objects the smaller the overhead of tracking slabsand the less frequently locks need to be acquired.For more information see Documentation/vm/slub.txt.slub_min_order=[MM, SLUB]Determines the mininum page order for slabs. Must belower than slub_max_order.For more information see Documentation/vm/slub.txt.slub_nomerge[MM, SLUB]Disable merging of slabs with similar size. May benecessary if there is some reason to distinguishallocs to different slabs. Debug options disablemerging on their own.For more information see Documentation/vm/slub.txt.smart2=[HW]Format: <io1>[,<io2>[,...,<io8>]]smp-alt-once[X86-32,SMP] On a hotplug CPU system, onlyattempt to substitute SMP alternatives once at boot.smsc-ircc2.nopnp[HW] Don't use PNP to discover SMC devicessmsc-ircc2.ircc_cfg=[HW] Device configuration I/O portsmsc-ircc2.ircc_sir=[HW] SIR base I/O portsmsc-ircc2.ircc_fir=[HW] FIR base I/O portsmsc-ircc2.ircc_irq=[HW] IRQ linesmsc-ircc2.ircc_dma=[HW] DMA channelsmsc-ircc2.ircc_transceiver= [HW] Transceiver type:0: Toshiba Satellite 1800 (GP data pin select)1: Fast pin select (default)2: ATC IRModesoftlockup_panic=[KNL] Should the soft-lockup detector generate panics.Format: <integer>sonypi.*=[HW] Sony Programmable I/O Control Device driverSee Documentation/sonypi.txtspecialix=[HW,SERIAL] Specialix multi-serial port adapterSee Documentation/serial/specialix.txt.spia_io_base=[HW,MTD]spia_fio_base=spia_pedr=spia_peddr=stacktrace[FTRACE]Enabled the stack tracer on boot up.sti=[PARISC,HW]Format: <num>Set the STI (builtin display/keyboard on the HP-PARISCmachines) console (graphic card) which should be usedas the initial boot-console.See also comment in drivers/video/console/sticore.c.sti_font=[HW]See comment in drivers/video/console/sticore.c.stifb=[HW]Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]sunrpc.min_resvport=sunrpc.max_resvport=[NFS,SUNRPC]SunRPC servers often require that client requestsoriginate from a privileged port (i.e. a port in therange 0 < portnr < 1024).An administrator who wishes to reserve some of theseports for other uses may adjust the range that thekernel's sunrpc client considers to be privilegedusing these two parameters to set the minimum andmaximum port values.sunrpc.pool_mode=[NFS]Control how the NFS server code allocates CPUs toservice thread pools. Depending on how many NICsyou have and where their interrupts are bound, thisoption will affect which CPUs will do NFS serving.Note: this parameter cannot be changed while theNFS server is running.auto the server chooses an appropriate mode automatically using heuristicsglobal a single global pool contains all CPUspercpu one pool for each CPUpernode one pool for each NUMA node (equivalent to global on non-NUMA machines)sunrpc.tcp_slot_table_entries=sunrpc.udp_slot_table_entries=[NFS,SUNRPC]Sets the upper limit on the number of simultaneousRPC calls that can be sent from the client to aserver. Increasing these values may allow you toimprove throughput, but will also increase theamount of memory reserved for use by the client.swapaccount[=0|1][KNL] Enable accounting of swap in memory resourcecontroller if no parameter or 1 is given or disableit if 0 is given (See Documentation/cgroups/memory.txt)swiotlb=[IA-64] Number of I/O TLB slabsswitches=[HW,M68k]sysfs.deprecated=0|1 [KNL]Enable/disable old style sysfs layout for old udevon older distributions. When this option is enabledvery new udev will not work anymore. When this optionis disabled (or CONFIG_SYSFS_DEPRECATED not compiled)in older udev will not work anymore.Default depends on CONFIG_SYSFS_DEPRECATED_V2 set inthe kernel configuration.sysrq_always_enabled[KNL]Ignore sysrq setting - this boot parameter willneutralize any effect of /proc/sys/kernel/sysrq.Useful for debugging.tdfx=[HW,DRM]test_suspend=[SUSPEND]Specify "mem" (for Suspend-to-RAM) or "standby" (forstandby suspend) as the system sleep state to brieflyenter during system startup. The system is woken fromthis state using a wakeup-capable RTC alarm.thash_entries=[KNL,NET]Set number of hash buckets for TCP connectionthermal.act=[HW,ACPI]-1: disable all active trip points in all thermal zones<degrees C>: override all lowest active trip pointsthermal.crt=[HW,ACPI]-1: disable all critical trip points in all thermal zones<degrees C>: override all critical trip pointsthermal.nocrt=[HW,ACPI]Set to disable actions on ACPI thermal zonecritical and hot trip points.thermal.off=[HW,ACPI]1: disable ACPI thermal controlthermal.psv=[HW,ACPI]-1: disable all passive trip points<degrees C>: override all passive trip points to thisvaluethermal.tzp=[HW,ACPI]Specify global default ACPI thermal zone polling rate<deci-seconds>: poll all this frequency0: no polling (default)threadirqs[KNL]Force threading of all interrupt handlers except thosemarked explicitely IRQF_NO_THREAD.topology=[S390]Format: {off | on}Specify if the kernel should make use of the cputopology information if the hardware supports this.The scheduler will make use of this information ande.g. base its process migration decisions on it.Default is on.tp720=[HW,PS2]tpm_suspend_pcr=[HW,TPM]Format: integer pcr idSpecify that at suspend time, the tpm drivershould extend the specified pcr with zeros,as a workaround for some chips which fail toflush the last written pcr on TPM_SaveState.This will guarantee that all the other pcrsare saved.trace_buf_size=nn[KMG][FTRACE] will set tracing buffer size.trace_event=[event-list][FTRACE] Set and start specified trace events in orderto facilitate early boot debugging.See also Documentation/trace/events.txttsc=Disable clocksource stability checks for TSC.Format: <string>[x86] reliable: mark tsc clocksource as reliable, thisdisables clocksource verification at runtime, as wellas the stability checks done at bootup.Used to enablehigh-resolution timer mode on older hardware, and invirtualized environment.[x86] noirqtime: Do not use TSC to do irq accounting.Used to run time disable IRQ_TIME_ACCOUNTING on anyplatforms where RDTSC is slow and this accountingcan add overhead.turbografx.map[2|3]=[HW,JOY]TurboGraFX parallel port interfaceFormat:<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>See also Documentation/input/joystick-parport.txtuhash_entries=[KNL,NET]Set number of hash buckets for UDP/UDP-Lite connectionsuhci-hcd.ignore_oc=[USB] Ignore overcurrent events (default N).Some badly-designed motherboards generate lots ofbogus events, for ports that aren't wired toanything. Set this parameter to avoid log spamming.Note that genuine overcurrent events won't bereported either.unknown_nmi_panic[X86] Cause panic on unknown NMI.usbcore.autosuspend=[USB] The autosuspend time delay (in seconds) usedfor newly-detected USB devices (default 2). Thisis the time required before an idle device will beautosuspended. Devices for which the delay is setto a negative value won't be autosuspended at all.usbcore.usbfs_snoop=[USB] Set to log all usbfs traffic (default 0 = off).usbcore.blinkenlights=[USB] Set to cycle leds on hubs (default 0 = off).usbcore.old_scheme_first=[USB] Start with the old device initializationscheme (default 0 = off).usbcore.use_both_schemes=[USB] Try the other device initialization schemeif the first one fails (default 1 = enabled).usbcore.initial_descriptor_timeout=[USB] Specifies timeout for the initial 64-byte USB_REQ_GET_DESCRIPTOR request in milliseconds(default 5000 = 5.0 seconds).usbhid.mousepoll=[USBHID] The interval which mice are to be polled at.usb-storage.delay_use=[UMS] The delay in seconds before a new device isscanned for Logical Units (default 5).usb-storage.quirks=[UMS] A list of quirks entries to supplement oroverride the built-in unusual_devs list. Listentries are separated by commas. Each entry hasthe form VID:PID:Flags where VID and PID are Vendorand Product ID values (4-digit hex numbers) andFlags is a set of characters, each correspondingto a common usb-storage quirk flag as follows:a = SANE_SENSE (collect more than 18 bytesof sense data);b = BAD_SENSE (don't collect more than 18bytes of sense data);c = FIX_CAPACITY (decrease the reporteddevice capacity by one sector);d = NO_READ_DISC_INFO (don't useREAD_DISC_INFO command);e = NO_READ_CAPACITY_16 (don't useREAD_CAPACITY_16 command);h = CAPACITY_HEURISTICS (decrease thereported device capacity by onesector if the number is odd);i = IGNORE_DEVICE (don't bind to thisdevice);l = NOT_LOCKABLE (don't try to lock andunlock ejectable media);m = MAX_SECTORS_64 (don't transfer morethan 64 sectors = 32 KB at a time);n = INITIAL_READ10 (force a retry of theinitial READ(10) command);o = CAPACITY_OK (accept the capacityreported by the device);r = IGNORE_RESIDUE (the device reportsbogus residue values);s = SINGLE_LUN (the device has only oneLogical Unit);w = NO_WP_DETECT (don't test whether themedium is write-protected).Example: quirks=0419:aaf5:rl,0421:0433:rcuserpte=[X86] Flags controlling user PTE allocations.nohigh = do not allocate PTE pages inHIGHMEM regardless of settingof CONFIG_HIGHPTE.vdso=[X86,SH]vdso=2: enable compat VDSO (default with COMPAT_VDSO)vdso=1: enable VDSO (default)vdso=0: disable VDSO mappingvdso32=[X86]vdso32=2: enable compat VDSO (default with COMPAT_VDSO)vdso32=1: enable 32-bit VDSO (default)vdso32=0: disable 32-bit VDSO mappingvector=[IA-64,SMP]vector=percpu: enable percpu vector domainvideo=[FB] Frame buffer configurationSee Documentation/fb/modedb.txt.vga=[BOOT,X86-32] Select a particular video modeSee Documentation/x86/boot.txt andDocumentation/svga.txt.Use vga=ask for menu.This is actually a boot loader parameter; the value ispassed to the kernel using a special protocol.vmalloc=nn[KMG][KNL,BOOT] Forces the vmalloc area to have an exactsize of <nn>. This can be used to increase theminimum size (128MB on x86). It can also be used todecrease the size and leave more room for directlymapped kernel RAM.vmhalt=[KNL,S390] Perform z/VM CP command after system halt.Format: <command>vmpanic=[KNL,S390] Perform z/VM CP command after kernel panic.Format: <command>vmpoff=[KNL,S390] Perform z/VM CP command after power off.Format: <command>vt.cur_default=[VT] Default cursor shape.Format: 0xCCBBAA, where AA, BB, and CC are the same asthe parameters of the <Esc>[?A;B;Cc escape sequence;see VGA-softcursor.txt. Default: 2 = underline.vt.default_blu=[VT]Format: <blue0>,<blue1>,<blue2>,...,<blue15>Change the default blue palette of the console.This is a 16-member array composed of valuesranging from 0-255.vt.default_grn=[VT]Format: <green0>,<green1>,<green2>,...,<green15>Change the default green palette of the console.This is a 16-member array composed of valuesranging from 0-255.vt.default_red=[VT]Format: <red0>,<red1>,<red2>,...,<red15>Change the default red palette of the console.This is a 16-member array composed of valuesranging from 0-255.vt.default_utf8=[VT]Format=<0|1>Set system-wide default UTF-8 mode for all tty's.Default is 1, i.e. UTF-8 mode is enabled for allnewly opened terminals.vt.global_cursor_default=[VT]Format=<-1|0|1>Set system-wide default for whether a cursoris shown on new VTs. Default is -1,i.e. cursors will be created by default unlessoverridden by individual drivers. 0 will hidecursors, 1 will display them.watchdog timers[HW,WDT] For information on watchdog timers,see Documentation/watchdog/watchdog-parameters.txtor other driver-specific files in theDocumentation/watchdog/ directory.x2apic_phys[X86-64,APIC] Use x2apic physical mode instead ofdefault x2apic cluster mode on platformssupporting x2apic.x86_mrst_timer= [X86-32,APBT]Choose timer option for x86 Moorestown MID platform.Two valid options are apbt timer only and lapic timerplus one apbt timer for broadcast timer.x86_mrst_timer=apbt_only | lapic_and_apbtxd=[HW,XT] Original XT pre-IDE (RLL encoded) disks.xd_geo=See header of drivers/block/xd.c.xen_emul_unplug=[HW,X86,XEN]Unplug Xen emulated devicesFormat: [unplug0,][unplug1]ide-disks -- unplug primary master IDE devicesaux-ide-disks -- unplug non-primary-master IDE devicesnics -- unplug network devicesall -- unplug all emulated devices (NICs and IDE disks)unnecessary -- unplugging emulated devices isunnecessary even if the host did not respond tothe unplug protocolnever -- do not unplug even if version check succeedsxirc2ps_cs=[NET,PCMCIA]Format:<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]______________________________________________________________________TODO:Add more DRM drivers.
人，都有不能称心如意的时候，都有愿望落空的窘迫，
