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Linux Kernel Parameters

2012-03-30 17:43:00.0 Linux parameters linux x86 debugging timer parallel  
导读: Kernel Parameters ~~~~~~~~~~~~~~~~~The following is a consolidated list of the kernel parameters as implemented(mostly) by the __setup() macro and so...。。。
                          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, so log_buf_len=1M print-fatal-signals=1can also be entered as log-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: ACPI ACPI support is enabled. AGP AGP (Accelerated Graphics Port) is enabled. ALSA ALSA sound support is enabled. APIC APIC support is enabled. APM Advanced Power Management support is enabled. AVR32 AVR32 architecture is enabled. AX25 Appropriate AX.25 support is enabled. BLACKFIN Blackfin architecture is enabled. DRM Direct Rendering Management support is enabled. DYNAMIC_DEBUG Build in debug messages and enable them at runtime EDD BIOS Enhanced Disk Drive Services (EDD) is enabled EFI EFI Partitioning (GPT) is enabled EIDE EIDE/ATAPI support is enabled. FB The frame buffer device is enabled. GCOV GCOV profiling is enabled. HW Appropriate hardware is enabled. IA-64 IA-64 architecture is enabled. IMA     Integrity measurement architecture is enabled. IOSCHED More than one I/O scheduler is enabled. IP_PNP IP DHCP, BOOTP, or RARP is enabled. IPV6 IPv6 support is enabled. ISAPNP ISA PnP code is enabled. ISDN Appropriate ISDN support is enabled. JOY Appropriate joystick support is enabled. KGDB Kernel debugger support is enabled. KVM Kernel Virtual Machine support is enabled. LIBATA  Libata driver is enabled LP Printer support is enabled. LOOP Loopback device support is enabled. M68k M68k architecture is enabled.   These options have more detailed description inside of   Documentation/m68k/kernel-options.txt. MCA MCA bus support is enabled. MDA MDA console support is enabled. MOUSE Appropriate mouse support is enabled. MSI Message Signaled Interrupts (PCI). MTD MTD (Memory Technology Device) support is enabled. NET Appropriate network support is enabled. NUMA NUMA support is enabled. NFS Appropriate NFS support is enabled. OSS OSS sound support is enabled. PV_OPS A paravirtualized kernel is enabled. PARIDE The ParIDE (parallel port IDE) subsystem is enabled. PARISC The PA-RISC architecture is enabled. PCI PCI bus support is enabled. PCIE PCI Express support is enabled. PCMCIA The PCMCIA subsystem is enabled. PNP Plug & Play support is enabled. PPC PowerPC architecture is enabled. PPT Parallel port support is enabled. PS2 Appropriate PS/2 support is enabled. RAM RAM disk support is enabled. S390 S390 architecture is enabled. SCSI Appropriate SCSI support is enabled.   A lot of drivers have their options described inside   the Documentation/scsi/ sub-directory. SECURITY Different security models are enabled. SELINUX SELinux support is enabled. APPARMOR AppArmor support is enabled. SERIAL Serial support is enabled. SH SuperH architecture is enabled. SMP The kernel is an SMP kernel. SPARC Sparc architecture is enabled. SWSUSP Software suspend (hibernation) is enabled. SUSPEND System suspend states are enabled. FTRACE Function tracing enabled. TPM TPM drivers are enabled. TS Appropriate touchscreen support is enabled. UMS USB Mass Storage support is enabled. USB USB support is enabled. USBHID USB Human Interface Device support is enabled. V4L Video For Linux support is enabled. VGA The VGA console has been enabled. VT Virtual terminal support is enabled. WDT Watchdog support is enabled. XT IBM PC/XT MFM hard disk support is enabled. X86-32 X86-32, aka i386 architecture is enabled. X86-64 X86-64 architecture is enabled.   More X86-64 boot options can be found in   Documentation/x86/x86_64/boot-options.txt . X86 Either 32bit or 64bit x86 (same as X86-32+X86-64) XEN Xen support is enabledIn addition, the following text indicates that the option: BUGS= Relates to possible processor bugs on the said processor. KNL Is a kernel start-up parameter. BOOT Is 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 .There are also arch-specific kernel-parameters not documented here.See for example .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 Interface   Format: { force | off | strict | noirq | rsdt }   force -- enable ACPI if default was off   off -- disable ACPI if default was on   noirq -- do not use ACPI for IRQ routing   strict -- Be less tolerant of platforms that are not    strictly ACPI specification compliant.   rsdt -- prefer RSDT over (default) XSDT   copy_dsdt -- copy DSDT to memory   See also Documentation/power/pm.txt, pci=noacpi acpi_apic_instance= [ACPI, IOAPIC]   Format:    2: use 2nd APIC table, if available   1,0: use 1st APIC table   default: 0 acpi_backlight= [HW,ACPI]   acpi_backlight=vendor   acpi_backlight=video   If set to vendor, prefer vendor specific driver   (e.g. thinkpad_acpi, sony_acpi, etc.) instead   of the ACPI video.ko driver. acpi.debug_layer= [HW,ACPI,ACPI_DEBUG] acpi.debug_level= [HW,ACPI,ACPI_DEBUG]   Format:    CONFIG_ACPI_DEBUG must be enabled to produce any ACPI   debug output.  Bits in debug_layer correspond to a   _COMPONENT in an ACPI source file, e.g.,       #define _COMPONENT ACPI_PCI_COMPONENT   Bits in debug_level correspond to a level in   ACPI_DEBUG_PRINT statements, e.g.,       ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...   The debug_level mask defaults to "info".  See   Documentation/acpi/debug.txt for more information about   debug layers and levels.   Enable processor driver info messages:       acpi.debug_layer=0x20000000   Enable PCI/PCI interrupt routing info messages:       acpi.debug_layer=0x400000   Enable AML "Debug" output, i.e., stores to the Debug   object while interpreting AML:       acpi.debug_layer=0xffffffff acpi.debug_level=0x2   Enable all messages related to ACPI hardware:       acpi.debug_layer=0x2 acpi.debug_level=0xffffffff   Some values produce so much output that the system is   unusable.  The "log_buf_len" parameter may be useful   if you need to capture more output. acpi_irq_balance [HW,ACPI]   ACPI will balance active IRQs   default in APIC mode acpi_irq_nobalance [HW,ACPI]   ACPI will not move active IRQs (default)   default in PIC mode acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA   Format: ,... acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for   use by PCI   Format: ,... acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS   Format: To spoof as Windows 98: ="Microsoft Windows" acpi_osi= [HW,ACPI] Modify list of supported OS interface strings   acpi_osi="string1" # add string1 -- only one string   acpi_osi="!string2" # remove built-in string2   acpi_osi=  # disable all strings acpi_pm_good [X86]   Override the pmtimer bug detection: force the kernel   to assume that this machine's pmtimer latches its value   and always returns good values. acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode   Format: { level | edge | high | low } acpi_serialize [HW,ACPI] force serialization of AML methods acpi_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 options   Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,      old_ordering, nonvs, sci_force_enable }   See Documentation/power/video.txt for information on   s3_bios and s3_mode.   s3_beep is for debugging; it makes the PC's speaker beep   as soon as the kernel's real-mode entry point is called.   s4_nohwsig prevents ACPI hardware signature from being   used during resume from hibernation.   old_ordering causes the ACPI 1.0 ordering of the _PTS   control method, with respect to putting devices into   low power states, to be enforced (the ACPI 2.0 ordering   of _PTS is used by default).   nonvs prevents the kernel from saving/restoring the   ACPI NVS memory during suspend/hibernation and resume.   sci_force_enable causes the kernel to set SCI_EN directly   on 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 boards   that require a timer override, but don't have HPET acpi_enforce_resources= [ACPI]   { strict | lax | no }   Check for resource conflicts between native drivers   and ACPI OperationRegions (SystemIO and SystemMemory   only). IO ports and memory declared in ACPI might be   used by the ACPI subsystem in arbitrary AML code and   can interfere with legacy drivers.   strict (default): access to resources claimed by ACPI   is denied; legacy drivers trying to access reserved   resources will fail to bind to device using them.   lax: access to resources claimed by ACPI is allowed;   legacy drivers trying to access reserved resources   will 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 in   kernel's map of available physical RAM. agp=  [AGP]   { off | try_unsupported }   off: disable AGP support   try_unsupported: try to drive unsupported chipsets    (may crash computer or cause data corruption) ALSA  [HW,ALSA]   See Documentation/sound/alsa/alsa-parameters.txt alignment= [KNL,ARM]   Allow the default userspace alignment fault handler   behaviour 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 faster   off   - do not initialize any AMD IOMMU found in        the system amijoy.map= [HW,JOY] Amiga joystick support   Map of devices attached to JOY0DAT and JOY1DAT   Format: ,   See also Documentation/kernel/input/joystick.txt analog.map= [HW,JOY] Analog joystick and gamepad support   Specifies type or capabilities of an analog joystick   connected to one of 16 gameports   Format: ,,.. apc=  [HW,SPARC]   Power management functions (SPARCstation-4/5 + deriv.)   Format: noidle   Disable APC CPU standby support. SPARCstation-Fox does   not play well with APC CPU idle - disable it if you have   APC and your system crashes randomly. apic=  [APIC,X86-32] Advanced Programmable Interrupt Controller   Change the output verbosity whilst booting   Format: { quiet (default) | verbose | debug }   Change the amount of debugging information output   when initialising the APIC and IO-APIC components. autoconf= [IPV6]   See Documentation/networking/ipv6.txt. show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller   Limit apic dumping. The parameter defines the maximal   number of local apics being dumped. Also it is possible   to set it to "all" by meaning -- no limit here.   Format: { 1 (default) | 2 | ... | all }.   The parameter valid if only apic=debug or   apic=verbose is specified.   Example: apic=debug show_lapic=all apm=  [APM] Advanced Power Management   See header of arch/x86/kernel/apm_32.c. arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards   Format: ,, ataflop= [HW,M68k] atarimouse= [HW,MOUSE] Atari Mouse atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,   EzKey and similar keyboards atkbd.reset= [HW] Reset keyboard during initialization atkbd.set= [HW] Select keyboard code set   Format:  (2 = AT (default), 3 = PS/2) atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar   keyboards atkbd.softraw= [HW] Choose between synthetic and real raw mode   Format:  (0 = real, 1 = synthetic (default)) atkbd.softrepeat= [HW]   Use software keyboard repeat autotest [IA64] baycom_epp= [HW,AX25]   Format: , baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem   Format: ,   See header of drivers/net/hamradio/baycom_par.c. baycom_ser_fdx= [HW,AX25]   BayCom Serial Port AX.25 Modem (Full Duplex Mode)   Format: ,,[,]   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: ,,   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 to   no delay (0).   Format: integer bootmem_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 as   kernel args too. bttv.pll= See Documentation/video4linux/bttv/Insmod-options bttv.tuner= and Documentation/video4linux/bttv/CARDLIST bulk_remove=off [PPC]  This parameter disables the use of the pSeries   firmware feature for flushing multiple hpte entries   at a time. c101=  [NET] Moxa C101 synchronous serial card cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.   Sometimes CPU hardware bugs make them report the cache   size incorrectly. The kernel will attempt work arounds   to fix known problems, but for some CPUs it is not   possible to determine what the correct size should be.   This option provides an override for these situations. capability.disable=   [SECURITY] Disable capabilities.  This would normally   be used only if an alternative security model is to be   configured.  Potentially dangerous and should only be   used if you are entirely sure of the consequences. ccw_timeout_log [S390]   See Documentation/s390/CommonIO for details. cgroup_disable= [KNL] Disable a particular controller   Format: {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 (includes    any 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 used   when calculating gettimeofday(). If specified   clocksource is not available, it defaults to PIT.   Format: { pit | tsc | cyclone | pmtmr } clocksource= Override the default clocksource   Format:    Override the default clocksource and use the clocksource   with the name specified.   Some clocksource names to choose from, depending on   the 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,tsc clearcpuid=BITNUM [X86]   Disable CPUID feature X for the kernel. See   arch/x86/include/asm/cpufeature.h for the valid bit   numbers. Note the Linux specific bits are not necessarily   stable over kernel options, but the vendor specific   ones should be.   Also note that user programs calling CPUID directly   or using the feature without checking anything   will still see it. This just prevents it from   being used by the kernel or shown in /proc/cpuinfo.   Also note the kernel might malfunction if you disable   some critical bits. cmo_free_hint= [PPC] Format: { yes | no }   Specify whether pages are marked as being inactive   when they are freed.  This is used in CMO environments   to determine OS memory pressure for page stealing by   a hypervisor.   Default: yes code_bytes [X86] How many bytes of object code to print   in an oops report.   Range: 0 - 8192   Default: 64 com20020= [HW,NET] ARCnet - COM20020 chipset   Format:   [,[,[,[,[,]]]]] com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)   Format: [,] com90xx= [HW,NET]   ARCnet - COM90xx chipset (memory-mapped buffers)   Format: [,[,]] condev=  [HW,S390] console device conmode= console= [KNL] Output console device and options.  tty Use the virtual console device .  ttyS[,options]  ttyUSB0[,options]   Use the specified serial port.  The options are of   the form "bbbbpnf", where "bbbb" is the baud rate,   "p" is parity ("n", "o", or "e"), "n" is number of   bits, and "f" is flow control ("r" for RTS or   omit it).  Default is "9600n8".   See Documentation/serial-console.txt for more   information.  See   Documentation/networking/netconsole.txt for an   alternative.  uart[8250],io,[,options]  uart[8250],mmio,[,options]   Start an early, polled-mode console on the 8250/16550   UART at the specified I/O port or MMIO address,   switching to the matching ttyS device later.  The   options 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 instance   console=brl,ttyS0  For now, only VisioBraille is supported. consoleblank= [KNL] The console blank (screen saver) timeout in   seconds. Defaults to 10*60 = 10mins. A value of 0   disables the blank timer. coredump_filter=   [KNL] Change the default value for   /proc//coredump_filter.   See also Documentation/filesystems/proc.txt. cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver   Format:   ,,,[,] crashkernel=size[KMG][@offset[KMG]]   [KNL] Using kexec, Linux can switch to a 'crash kernel'   upon panic. This parameter reserves the physical   memory region [offset, offset + size] for that kernel   image. If '@offset' is omitted, then a suitable offset   is selected automatically. Check   Documentation/kdump/kdump.txt for further details. crashkernel=range1:size1[,range2:size2,...][@offset]   [KNL] Same as above, but depends on the memory   in the running system. The syntax of range is   start-[end] where start and end are both   a memory unit (amount[KMG]). See also   Documentation/kdump/kdump.txt for an example. cs89x0_dma= [HW,NET]   Format:  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: ,   See also Documentation/input/joystick-parport.txt ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot   time. See Documentation/dynamic-debug-howto.txt for   details. debug  [KNL] Enable kernel debugging (events log level). debug_locks_verbose=   [KNL] verbose self-tests   Format=<0|1>   Print debugging info while doing the locking API   self-tests.   We default to 0 (no extra messages), setting it to   1 will print _a lot_ more information - normally   only useful to kernel developers. debug_objects [KNL] Enable object debugging no_debug_objects   [KNL] Disable object debugging debugpat [X86] Enable PAT debugging decnet.addr= [HW,NET]   Format: [,]   See also Documentation/networking/decnet.txt. default_hugepagesz=   [same as hugepagesz=] The size of the default   HugeTLB page size. This is the size represented by   the legacy /proc/ hugepages APIs, used for SHM, and   default size when mounting hugetlbfs filesystems.   Defaults to the default architecture's huge page size   if 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 and   Documentation/serial/digiepca.txt. disable= [IPV6]   See Documentation/networking/ipv6.txt. disable_ddw     [PPC/PSERIES]   Disable Dynamic DMA Window support. Use this if   to workaround buggy firmware. disable_ipv6= [IPV6]   See Documentation/networking/ipv6.txt. disable_mtrr_cleanup [X86]   The kernel tries to adjust MTRR layout from continuous   to discrete, to make X server driver able to add WB   entry later. This parameter disables that. disable_mtrr_trim [X86, Intel and AMD only]   By default the kernel will trim any uncacheable   memory out of your available memory pool based on   MTRR settings.  This parameter disables that behavior,   possibly causing your machine to run very slowly. disable_timer_pin_1 [X86]   Disable PIN 1 of APIC timer   Can be useful to work around chipset bugs. dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,   this option disables the debugging code at boot. dma_debug_entries=   This option allows to tune the number of preallocated   entries for DMA-API debugging code. One entry is   required per DMA-API allocation. Use this if the   DMA-API debugging code disables itself because the   architectural default is too low. dma_debug_driver=   With this option the DMA-API debugging driver   filter feature can be enabled at boot time. Just   pass the driver to filter for as the parameter.   The filter can be disabled or changed to another   driver later using sysfs. dscc4.setup= [NET] earlycon= [KNL] Output early console device and options.  uart[8250],io,[,options]  uart[8250],mmio,[,options]  uart[8250],mmio32,[,options]   Start an early, polled-mode console on the 8250/16550   UART 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=vga   earlyprintk=serial[,ttySn[,baudrate]]   earlyprintk=ttySn[,baudrate]   earlyprintk=dbgp[debugController#]   Append ",keep" to not disable it when the real console   takes 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 not   very good.   The VGA output is eventually overwritten by the real   console. ekgdboc= [X86,KGDB] Allow early kernel console debugging   ekgdboc=kbd   This is designed to be used in conjunction with   the boot argument: earlyprintk=vga edd=  [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() in   arch/x86/kernel/cpu/cpufreq/elanfreq.c. elevator= [IOSCHED]   Format: {"cfq" | "deadline" | "noop"}   See Documentation/block/as-iosched.txt and   Documentation/block/deadline-iosched.txt for details. elfcorehdr= [IA64,PPC,SH,X86]   Specifies physical address of start of kernel core   image elf header. Generally kexec loader will   pass this option to capture kernel.   See Documentation/kdump/kdump.txt for details. enable_mtrr_cleanup [X86]   The kernel tries to adjust MTRR layout from continuous   to discrete, to make X server driver able to add WB   entry later. This parameter enables that. enable_timer_pin_1 [X86]   Enable PIN 1 of APIC timer   Can 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 parameters   This option is obsoleted by the "netdev=" option, which   has equivalent usage. See its documentation for details. failslab= fail_page_alloc= fail_make_request=[KNL]   General fault injection mechanism.   Format: ,,,   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 on   buggy SAL_CACHE_FLUSH implementations. Using this   parameter will force ia64_sal_cache_flush to call   ia64_pal_cache_flush instead of SAL_CACHE_FLUSH. ftrace=[tracer]   [FTRACE] will set and start the specified tracer   as early as possible in order to facilitate early   boot debugging. ftrace_dump_on_oops[=orig_cpu]   [FTRACE] will dump the trace buffers on oops.   If no parameter is passed, ftrace will dump   buffers of all CPUs, but if you pass orig_cpu, it will   dump only the buffer of the CPU that triggered the   oops. ftrace_filter=[function-list]   [FTRACE] Limit the functions traced by the function   tracer at boot up. function-list is a comma separated   list of functions. This list can be changed at run   time by the set_ftrace_filter file in the debugfs   tracing directory.  ftrace_notrace=[function-list]   [FTRACE] Do not trace the functions specified in   function-list. This list can be changed at run time   by the set_ftrace_notrace file in the debugfs   tracing directory. ftrace_graph_filter=[function-list]   [FTRACE] Limit the top level callers functions traced   by the function graph tracer at boot up.   function-list is a comma separated list of functions   that can be changed at run time by the   set_graph_function file in the debugfs tracing directory. gamecon.map[2|3]=   [HW,JOY] Multisystem joystick and NES/SNES/PSX pad   support via parallel port (up to 5 devices per port)   Format: ,,,,,   See also Documentation/input/joystick-parport.txt gamma=  [HW,DRM] gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART   Format: off | on   default: on gcov_persist= [GCOV] When non-zero (default), profiling data for   kernel modules is saved and remains accessible via   debugfs, even when the module is unloaded/reloaded.   When zero, profiling data is discarded and associated   debugfs files are removed at module unload time. gpt  [EFI] Forces disk with valid GPT signature but   invalid Protective MBR to be treated as GPT. hashdist= [KNL,NUMA] Large hashes allocated during boot   are distributed across NUMA nodes.  Defaults on   for 64bit NUMA, off otherwise.   Format: 0 | 1 (for off | on) hcl=  [IA-64] SGI's Hardware Graph compatibility layer hd=  [EIDE] (E)IDE hard drive subsystem geometry   Format: ,, hest_disable [ACPI]   Disable Hardware Error Source Table (HEST) support;   corresponding firmware-first mode error processing   logic will be disabled. highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact   size of . This works even on boxes that have no   highmem otherwise. This also works to reduce highmem   size 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 usage   Format: { enable (default) | disable | force |    verbose }   disable: disable HPET and use PIT instead   force: allow force enabled of undocumented chips (ICH4,    VIA, nVidia)   verbose: show contents of HPET registers during setup hugepages= [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 specified   multiple times interleaved with hugepages= to reserve   huge pages of different sizes. Valid pages sizes on   x86-64 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 time   using hugepages= and not freed afterwards. hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)          terminal devices. Valid values: 0..8 hvc_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 only   useful for debugging when something happens in the window   between unregistering the boot console and initializing   the 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:        , i8042.debug [HW] Toggle i8042 debug mode i8042.direct [HW] Put keyboard port into non-translated mode i8042.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) port i8042.nokbd [HW] Don't check/create keyboard port i8042.noloop [HW] Disable the AUX Loopback command while probing        for the AUX port i8042.nomux [HW] Don't check presence of an active multiplexing        controller i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX        controllers i8042.notimeout [HW] Ignore timeout condition signalled by conroller i8042.reset [HW] Reset the controller during init and cleanup i8042.unlock [HW] Unlock (ignore) the keylock i810=  [HW,DRM] i8k.ignore_dmi [HW] Continue probing hardware even if DMI data   indicates that the driver is running on unsupported   hardware. i8k.force [HW] Activate i8k driver even if SMM BIOS signature   does 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_ADMIN   capability is set. icn=  [HW,ISDN]   Format: [,[,[,]]] ide-core.nodma= [HW] (E)IDE subsystem   Format: =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 options   See Documentation/ide/ide.txt. ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem   Claim all unknown PCI IDE storage controllers. idle=  [X86]   Format: idle=poll, idle=mwait, idle=halt, idle=nomwait   Poll forces a polling idle loop that can slightly   improve the performance of waking up a idle CPU, but   will use a lot of power and make the system run hot.   Not recommended.   idle=mwait: On systems which support MONITOR/MWAIT but   the kernel chose to not use it because it doesn't save   as much power as a normal idle loop, use the   MONITOR/MWAIT idle loop anyways. Performance should be   the 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-states ignore_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 Trusted   Computing Base.  This means IMA will measure all   programs exec'd, files mmap'd for exec, and all files   opened for read by uid=0. init=  [KNL]   Format:    Run specified binary instead of /sbin/init as init   process. initcall_debug [KNL] Trace initcalls as they are executed.  Useful   for working out where the kernel is dying during   startup. initrd=  [BOOT] Specify the location of the initial ramdisk inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver   Format:  intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option  on   Enable intel iommu driver.  off   Disable intel iommu driver.  igfx_off [Default Off]   By default, gfx is mapped as normal device. If a gfx   device has a dedicated DMAR unit, the DMAR unit is   bypassed by not enabling DMAR with this option. In   this case, gfx device will use physical address for   DMA.  forcedac [x86_64]   With this option iommu will not optimize to look   for io virtual address below 32 bit forcing dual   address cycle on pci bus for cards supporting greater   than 32 bit addressing. The default is to look   for translation below 32 bit and if not available   then look in the higher range.  strict [Default Off]   With this option on every unmap_single operation will   result in a hardware IOTLB flush operation as opposed   to batching them for performance.  sp_off [Default Off]   By default, super page will be supported if Intel IOMMU   has the capability. With this option, super page will   not be supported. intremap= [X86-64, Intel-IOMMU]   Format: { on (default) | off | nosid }   on enable Interrupt Remapping (default)   off disable Interrupt Remapping   nosid disable Source ID checking inttest= [IA64] iomem=  Disable strict checking of access to MMIO memory  strict regions from userspace.  relaxed iommu=  [x86]  off  force  noforce  biomerge  panic  nopanic  merge  nomerge  forcesac  soft  pt [x86, IA64] io7=  [HW] IO7 for Marvel based alpha systems   See comment before marvel_specify_io7 in   arch/alpha/kernel/core_marvel.c. io_delay= [X86] I/O delay method  0x80   Standard port 0x80 based delay  0xed   Alternate port 0xed based delay (needed on some systems)  udelay   Simple two microseconds delay  none   No delay ip=  [IP_PNP]   See Documentation/filesystems/nfs/nfsroot.txt. ip2=  [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards   See comment before ip2_setup() in   drivers/char/ip2/ip2base.c. irqfixup [HW]   When an interrupt is not handled search all handlers   for it. Intended to get systems with badly broken   firmware running. irqpoll  [HW]   When an interrupt is not handled search all handlers   for it. Also check all handlers each timer   interrupt. Intended to get systems with badly broken   firmware running. isapnp=  [ISAPNP]   Format: ,,, isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.   Format:   ,...,   or   -   (must be a positive range in ascending order)   or a mixture   ,...,-   This option can be used to specify one or more CPUs   to isolate from the general SMP balancing and scheduling   algorithms. You can move a process onto or off an   "isolated" CPU via the CPU affinity syscalls or cpuset.    begins at 0 and the maximum value is   "number of CPUs in system - 1".   This option is the preferred way to isolate CPUs. The   alternative -- manually setting the CPU mask of all   tasks in the system -- can cause problems and   suboptimal load balancer performance. iucv=  [HW,NET] js=  [HW,JOY] Analog joystick   See Documentation/input/joystick.txt. keepinitrd [HW,ARM] kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter   specifies the amount of memory usable by the kernel   for non-movable allocations.  The requested amount is   spread evenly throughout all nodes in the system. The   remaining memory in each node is used for Movable   pages. In the event, a node is too small to have both   kernelcore and Movable pages, kernelcore pages will   take priority and other nodes will have a larger number   of kernelcore pages.  The Movable zone is used for the   allocation of pages that may be reclaimed or moved   by the page migration subsystem.  This means that   HugeTLB pages may not be allocated from this zone.   Note that allocations like PTEs-from-HighMem still   use the HighMem zone if it exists, and the Normal   zone if it does not. kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.   Format: [,poll interval]   The controller # is the number of the ehci usb debug   port as it is probed via PCI.  The poll interval is   optional and is the number seconds in between   each poll cycle to the debug port in case you need   the functionality for interrupting the kernel with   gdb or control-c on the dbgp connection.  When   not using this parameter you use sysrq-g to break into   the 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: [,baud]    keyboard only format: kbd    keyboard and serial format: kbd,[,baud]   Optional Kernel mode setting:    kms, kbd format: kms,kbd    kms, kbd and serial format: kms,kbd,[,baud] kgdbwait [KGDB] Stop kernel execution and enter the   kernel debugger at the earliest opportunity. kmac=  [MIPS] korina ethernet MAC address.   Configure the RouterBoard 532 series on-chip   Ethernet adapter MAC address. kmemleak= [KNL] Boot-time kmemleak enable/disable   Valid arguments: on, off   Default: on kstack=N [X86] Print N words from the kernel stack   in 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 audit   KVM 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 mode kvm-intel.bypass_guest_pf=   [KVM,Intel] Disables bypassing of guest page faults   on 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 states   Default 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 capable   Intel chips. Default is 1 (enabled) kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification   feature (tagged TLBs) on capable Intel chips.   Default is 1 (enabled) l2cr=  [PPC] l3cr=  [PPC] lapic  [X86-32,APIC] Enable the local APIC even if BIOS   disabled it. lapic_timer_c2_ok [X86,APIC] trust the local apic timer   in C2 power state. libata.dma= [LIBATA] DMA control   libata.dma=0   Disable all PATA and SATA DMA   libata.dma=1   PATA and SATA Disk DMA only   libata.dma=2   ATAPI (CDROM) DMA only   libata.dma=4   Compact Flash DMA only    Combinations also work, so libata.dma=3 enables DMA   for disks and CDROMs, but not CFs.  libata.ignore_hpa= [LIBATA] Ignore HPA limit   libata.ignore_hpa=0   keep BIOS limits (default)   libata.ignore_hpa=1   ignore limits, using full disk libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume   when set.   Format:  libata.force= [LIBATA] Force configurations.  The format is comma   separated list of "[ID:]VAL" where ID is   PORT[.DEVICE].  PORT and DEVICE are decimal numbers   matching port, link or device.  Basically, it matches   the ATA ID string printed on console by libata.  If   the whole ID part is omitted, the last PORT and DEVICE   values are used.  If ID hasn't been specified yet, the   configuration applies to all ports, links and devices.   If only DEVICE is omitted, the parameter applies to   the port and all links and devices behind it.  DEVICE   number of 0 either selects the first device or the   first fan-out link behind PMP device.  It does not   select the host link.  DEVICE number of 15 selects the   host link and device attached to it.   The VAL specifies the configuration to force.  As long   as 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 changing   the same attribute, the last one is used. memblock=debug [KNL] Enable memblock debug messages. load_ramdisk= [RAM] List of ramdisks to load from floppy   See Documentation/blockdev/ramdisk.txt. lockd.nlm_grace_period=P  [NFS] Assign grace period.   Format:  lockd.nlm_tcpport=N [NFS] Assign TCP port.   Format:  lockd.nlm_timeout=T [NFS] Assign timeout value.   Format:  lockd.nlm_udpport=M [NFS] Assign UDP port.   Format:  logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver   Format:  loglevel= All Kernel Messages with a loglevel smaller than the   console loglevel will be printed to the console. It can   also be changed with klogd or other programs. The   loglevels are defined as follows:   0 (KERN_EMERG)  system is unusable   1 (KERN_ALERT)  action must be taken immediately   2 (KERN_CRIT)  critical conditions   3 (KERN_ERR)  error conditions   4 (KERN_WARNING) warning conditions   5 (KERN_NOTICE)  normal but significant condition   6 (KERN_INFO)  informational   7 (KERN_DEBUG)  debug-level messages log_buf_len=n[KMG] Sets the size of the printk ring buffer,   in bytes.  n must be a power of two.  The default   size 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 for   kernel log messages and is useful when debugging   kernel boot problems. lp=0  [LP] Specify parallel ports to use, e.g, lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses lp=reset  first parallel port). 'lp=0' disables the lp=auto   printer driver. 'lp=reset' (which can be    specified in addition to the ports) causes    attached printers to be reset. Using    lp=port1,port2,... specifies the parallel ports    to associate lp devices with, starting with    lp0. A port specification may be 'none' to skip    that lp device, or a parport name such as    'parport0'. Specifying 'lp=auto' instead of a    port specification list means that device IDs    from each port should be examined, to see if    an IEEE 1284-compliant printer is attached; if    so, 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 avoiding   time-consuming boot-time autodetection (up to 250 ms per   CPU). 0 enables autodetection (default). To determine   the correct value for your kernel, boot with normal   autodetection and see what value is printed. Note that   on SMP systems the preset will be applied to all CPUs,   which is likely to cause problems if your CPUs need   significantly divergent settings. An incorrect value   will cause delays in the kernel to be wrong, leading to   unpredictable I/O errors and other breakage. Although   unlikely, in the extreme case this might damage your   hardware. ltpc=  [NET]   Format: ,, machvec= [IA64] Force the use of a particular machine-vector   (machvec) in a generic kernel.   Example: machvec=hpzx1_swiotlb machtype= [Loongson] Share the same kernel image file between different    yeeloong laptop.   Example: machtype=lemote-yeeloong-2f-7inch max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater   than or equal to this physical address is ignored. maxcpus= [SMP] Maximum number of processors that an SMP kernel   should make use of.  maxcpus=n : n >= 0 limits the   kernel to using 'n' processors.  n=0 is a special case,   it is equivalent to "nosmp", which also disables   the IO APIC. max_loop= [LOOP] Maximum number of loopback devices that can   be mounted   Format: <1-256> mcatest= [IA-64] mce  [X86-32] Machine Check Exception mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt md=  [HW] RAID subsystems devices and level   See Documentation/md.txt. mdacon=  [MDA]   Format: ,   Specifies range of consoles to be captured by the MDA. mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory   Amount of memory to be used when the kernel is not able   to see the whole system memory or for test.   [X86-32] Use together with memmap= to avoid physical   address space collisions. Without memmap= PCI devices   could be placed at addresses belonging to unused RAM. mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel   memory. memchunk=nn[KMG]   [KNL,SH] Allow user to override the default size for   per-device physically contiguous DMA buffers. memmap=exactmap [KNL,X86] Enable setting of an exact   E820 memory map, as specified by the user.   Such memmap=exactmap lines can be constructed based on   BIOS output or other requirements. See the memmap=nn@ss   option description. memmap=nn[KMG]@ss[KMG]   [KNL] Force usage of a specific region of memory   Region 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$0x18690000 memory_corruption_check=0/1 [X86]   Some BIOSes seem to corrupt the first 64k of   memory when doing things like suspend/resume.   Setting this option will scan the memory   looking for corruption.  Enabling this will   both detect corruption and prevent the kernel   from using the memory being corrupted.   However, its intended as a diagnostic tool; if   repeatable BIOS-originated corruption always   affects 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 low   64k, making this memory unavailable for normal   use.  Use this parameter to scan for   corruption in more or less memory. memory_corruption_check_period=seconds [X86]   By default it checks for corruption every 60   seconds.  Use this parameter to check at some   other rate.  0 disables periodic checking. memtest= [KNL,X86] Enable memtest   Format:    default : 0    Specifies the number of memtest passes to be   performed. Each pass selects another test   pattern from a given set of patterns. Memtest   fills the memory with this pattern, validates   memory contents and reserves bad memory   regions that are detected. meye.*=  [HW] Set MotionEye Camera parameters   See Documentation/video4linux/meye.txt. mfgpt_irq= [IA-32] Specify the IRQ to use for the   Multi-Function General Purpose Timers on AMD Geode   platforms. mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when   the BIOS has incorrectly applied a workaround. TinyBIOS   version 0.98 is known to be affected, 0.99 fixes the   problem by letting the user disable the workaround. mga=  [HW,DRM] min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this   physical 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" TFT   1 - The attached screen is the 7" TFT   2 - The VGA Shield is attached (1024x768)   Leaving out the screen size parameter will not load   the TFT driver, and the framebuffer will be left   unconfigured.   b - Enable backlight. The TFT backlight pin will be   linked to the kernel VESA blanking code and a GPIO   LED. This parameter is not necessary when using the   VGA shield.   c - Enable the s3c camera interface.   t - Reserved for enabling touchscreen support. The   touchscreen support is not enabled in the mainstream   kernel as of 2.6.30, a preliminary port can be found   in the "bleeding edge" mini2440 support kernel at   http://repo.or.cz/w/linux-2.6/mini2440.git mminit_loglevel=   [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this   parameter allows control of the logging verbosity for   the additional memory initialisation checks. A value   of 0 disables mminit logging and a level of 4 will   log everything. Information is printed at KERN_DEBUG   so loglevel=8 may also need to be specified. mousedev.tap_time=   [MOUSE] Maximum time between finger touching and   leaving touchpad surface for touch to be considered   a tap and be reported as a left button click (for   touchpads working in absolute mode only).   Format:  mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices   reporting absolute coordinates, such as tablets mousedev.yres= [MOUSE] Vertical screen resolution, used for devices   reporting absolute coordinates, such as tablets movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter   is similar to kernelcore except it specifies the   amount of memory used for migratable allocations.   If both kernelcore and movablecore is specified,   then kernelcore will be at *least* the specified   value but may be more. If movablecore on its own   is specified, the administrator must be careful   that the amount of memory usable for all allocations   is not too small. MTD_Partition= [MTD]   Format: ,,, MTD_Region= [MTD] Format:   ,[,,,,] mtdparts= [MTD]   See drivers/mtd/cmdlinepart.c. multitce=off [PPC]  This parameter disables the use of the pSeries   firmware feature for updating multiple TCE entries   at a time. onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration   Format: [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 control   See arch/arm/mach-s3c2412/mach-jive.c mtouchusb.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 chunk   that 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 from   using up MTRRs. mtrr_spare_reg_nr=n [X86]   Format:    Range: 0,7 : spare reg number   Default : 1   Used 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 card netdev=  [NET] Network devices parameters   Format: ,,,,   Note that mem_start is often overloaded to mean   something different and driver-specific.   This usage is only documented in each driver source   file if at all. nf_conntrack.acct=   [NETFILTER] Enable connection tracking flow accounting   0 to disable accounting   1 to enable accounting   Default 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 callback   channel should listen. nfs.cache_getent=   [NFS] sets the pathname to the program which is used   to update the NFS client cache entries. nfs.cache_getent_timeout=   [NFS] sets the timeout after which an attempt to   update a cache entry is deemed to have failed. nfs.idmap_cache_timeout=   [NFS] set the maximum lifetime for idmapper cache   entries. nfs.enable_ino64=   [NFS] enable 64-bit inode numbers.   If zero, the NFS client will fake up a 32-bit inode   number for the readdir() and stat() syscalls instead   of 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 NFSv4   idmapper on the client, but only if the mount   is using the 'sec=sys' security flavour. This may   make migration from legacy NFSv2/v3 systems easier   provided 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 take   when a NMI is triggered.   Format: [state][,regs][,debounce][,die] nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels   Format: [panic,][nopanic,][num]   Valid num: 0   0 - turn nmi_watchdog off   When panic is specified, panic when an NMI watchdog   timeout occurs (or 'nopanic' to override the opposite   default).   This is useful when you use a panic=... timeout and   need the box quickly up again. netpoll.carrier_timeout=   [NET] Specifies amount of time (in seconds) that   netpoll should wait for a carrier. By default netpoll   waits 4 seconds. no387  [BUGS=X86-32] Tells the kernel to use the 387 maths   emulation library even if a 387 maths coprocessor   is present. no_console_suspend   [HW] Never suspend the console   Disable suspending of consoles during suspend and   hibernate operations.  Once disabled, debugging   messages can reach various consoles while the rest   of the system is being put to sleep (ie, while   debugging driver suspend/resume hooks).  This may   not work reliably with all consoles, but is known   to work with serial and VGA consoles. noaliencache [MM, NUMA, SLAB] Disables the allocation of alien   caches 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 any   IOAPICs that may be present in the system. noautogroup Disable scheduler automatic task group creation. nobats  [PPC] Do not use BATs for mapping kernel lowmem   on "Classic" PPC cores. nocache  [ARM] noclflush [BUGS=X86] Don't use the CLFLUSH instruction nodelayacct [KNL] Disable per-task delay accounting nodisconnect [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 mappings nosmep  [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 mappings   noexec32=off: disable non-executable mappings    read implies executable mappings nofpu  [SH] Disable hardware FPU at boot time. nofxsr  [BUGS=X86-32] Disables x86 floating point extended   register save and restore. The kernel will only save   legacy floating-point registers on task switch. noxsave  [BUGS=X86] Disables x86 extended register state save   and restore using xsave. The kernel will fallback to   enabling legacy floating-point and sse state. nohlt  [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or   wfi(ARM) instruction doesn't work correctly and not to   use it. This is also useful when using JTAG debugger. no-hlt  [BUGS=X86-32] Tells the kernel that the hlt   instruction doesn't work correctly and not to   use it. no_file_caps Tells the kernel not to honor file capabilities.  The   only way then for a file to be executed with privilege   is to be setuid root or executed by root. nohalt  [IA-64] Tells the kernel not to use the power saving   function PAL_HALT_LIGHT when idle. This increases   power-consumption. On the positive side, it reduces   interrupt wake-up latency, which may improve performance   in certain environments such as networked servers or   real-time systems. nohz=  [KNL] Boottime enable/disable dynamic ticks   Valid arguments: on, off   Default: on noiotrap [SH] Disables trapped I/O port accesses. noirqdebug [X86-32] Disables the code which attempts to detect and   disable unhandled interrupt sources. no_timer_check [X86,APIC] Disables the code which tests for   broken timer IRQ sources. noisapnp [ISAPNP] Disables ISA PnP code. noinitrd [RAM] Tells the kernel not to load any configured   initial RAM disk. nointremap [X86-64, Intel-IOMMU] Do not enable interrupt   remapping.   [Deprecated - use intremap=off] nointroute [IA-64] nojitter [IA64] Disables jitter checking for ITC timers. no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page   fault 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 kernel   lowmem mapping on PPC40x. nomca  [IA-64] Disable machine check abort handling nomce  [X86-32] Machine Check Exception nomfgpt  [X86-32] Disable Multi-Function General Purpose   Timer usage (for AMD Geode machines). nopat  [X86] Disable PAT (page attribute table extension of   pagetables) support. norandmaps Don't use address space randomization.  Equivalent to   echo 0 > /proc/sys/kernel/randomize_va_space noreplace-paravirt [X86,IA-64,PV_OPS] Don't patch paravirt_ops noreplace-smp [X86-32,SMP] Don't replace SMP instructions   with UP alternatives noresidual [PPC] Don't use residual data on PReP machines. noresume [SWSUSP] Disables resume and restores original swap   space. no-scroll [VGA] Disables scrollback.   This is required for the Braillex ib80-piezo Braille   reader 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 Counter nousb  [USB] Disable the USB subsystem nowatchdog [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 TLB   purges which is reported from either PAL_VM_SUMMARY or   SAL PALO. nr_cpus= [SMP] Maximum number of processors that an SMP kernel   could support.  nr_cpus=n : n >= 1 limits the kernel to   supporting 'n' processors. Later in runtime you can not   use hotplug cpu feature to put more cpu back to online.   just like you compile the kernel NR_CPUS=n nr_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 specified   This 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 more   info. olpc_ec_timeout= [OLPC] ms delay when issuing EC commands   Rather than timing out after 20 ms if an EC   command is not properly ACKed, override the length   of the timeout.  We have interrupts disabled while   waiting for the ACK, so if this is set too high   interrupts *may* be lost! omap_mux= [OMAP] Override bootloader pin multiplexing.   Format: ...   For example, to override I2C bus2:   omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 oprofile.timer= [HW]   Use timer interrupt instead of performance counters oprofile.cpu_type= Force an oprofile cpu type   This might be useful if you have an older oprofile   userland or if you want common events.   Format: { arch_perfmon }   arch_perfmon: [X86] Force use of architectural    perfmon on Intel CPUs instead of the    CPU specific event set. oops=panic Always panic on oopses. Default is to just kill the   process, but there is a small probability of   deadlocking 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.txt panic=  [KNL] Kernel behaviour on panic: delay    seconds before rebooting   Format:  parkbd.port= [HW] Parallel port number the keyboard adapter is   connected to, default is 0.   Format:  parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,   0 for XT, 1 for AT (default is AT).   Format:  parport= [HW,PPT] Specify parallel ports. 0 disables.   Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }   Use 'auto' to force the driver to use any   IRQ/DMA settings detected (the default is to   ignore detected IRQ/DMA settings because of   possible conflicts). You can specify the base   address, IRQ, and DMA settings; IRQ and DMA   should be numbers, or 'auto' (for using detected   settings on that particular port), or 'nofifo'   (to avoid using a FIFO even if it is detected).   Parallel ports are assigned in the order they   are specified on the command line, starting   with parport0. parport_init_mode= [HW,PPT]   Configure VIA parallel port to operate in   a specific mode. This is necessary on Pegasos   computer where firmware has no options for setting   up 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 for   the specified number of seconds.  This is to be used if   your 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 anything  off  [X86] don't probe for the PCI bus  bios  [X86-32] force use of PCI BIOS, don't access    the hardware directly. Use this if your machine    has a non-standard PCI host bridge.  nobios  [X86-32] disallow use of PCI BIOS, only direct    hardware access methods are allowed. Use this    if you experience crashes upon bootup and you    suspect they are caused by the BIOS.  conf1  [X86] Force use of PCI Configuration    Mechanism 1.  conf2  [X86] Force use of PCI Configuration    Mechanism 2.  noaer  [PCIE] If the PCIEAER kernel config parameter is    enabled, this kernel boot option can be used to    disable the use of PCIE advanced error reporting.  nodomains [PCI] Disable support for multiple PCI    root domains (aka PCI segments, in ACPI-speak).  nommconf [X86] Disable use of MMCONFIG for PCI    Configuration  check_enable_amd_mmconf [X86] check for and enable    properly configured MMIO access to PCI    config space on AMD family 10h CPU  nomsi  [MSI] If the PCI_MSI kernel config parameter is    enabled, this kernel boot option can be used to    disable the use of MSI interrupts system-wide.  noioapicquirk [APIC] Disable all boot interrupt quirks.    Safety option to keep boot IRQs enabled. This    should never be necessary.  ioapicreroute [APIC] Enable rerouting of boot IRQs to the    primary IO-APIC for bridges that cannot disable    boot IRQs. This fixes a source of spurious IRQs    when the system masks IRQs.  noioapicreroute [APIC] Disable workaround that uses the    boot IRQ equivalent of an IRQ that connects to    a chipset where boot IRQs cannot be disabled.    The opposite of ioapicreroute.  biosirq  [X86-32] Use PCI BIOS calls to get the interrupt    routing table. These calls are known to be buggy    on several machines and they hang the machine    when used, but on other computers it's the only    way to get the interrupt routing table. Try    this option if the kernel is unable to allocate    IRQs or discover secondary PCI buses on your    motherboard.  rom  [X86] Assign address space to expansion ROMs.    Use with caution as certain devices share    address decoders between ROMs and other    resources.  norom  [X86] Do not assign address space to    expansion ROMs that do not already have    BIOS assigned address ranges.  nobar  [X86] Do not assign address space to the    BARs that weren't assigned by the BIOS.  irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be    assigned automatically to PCI devices. You can    make the kernel exclude IRQs of your ISA cards    this way.  pirqaddr=0xAAAAA [X86] Specify the physical address    of the PIRQ table (normally generated    by the BIOS) if it is outside the    F0000h-100000h range.  lastbus=N [X86] Scan all buses thru bus #N. Can be    useful if the kernel is unable to find your    secondary buses and you want to tell it    explicitly which ones they are.  assign-busses [X86] Always assign all PCI bus    numbers ourselves, overriding    whatever the firmware may have done.  usepirqmask [X86] Honor the possible IRQ mask stored    in the BIOS $PIR table. This is needed on    some systems with broken BIOSes, notably    some HP Pavilion N5400 and Omnibook XE3    notebooks. This will have no effect if ACPI    IRQ routing is enabled.  noacpi  [X86] Do not use ACPI for IRQ routing    or for PCI scanning.  use_crs  [X86] Use PCI host bridge window information    from ACPI.  On BIOSes from 2008 or later, this    is 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.  routeirq Do IRQ routing for all PCI devices.    This is normally done in pci_enable_device(),    so this option is a temporary workaround    for broken drivers that don't call it.  skip_isa_align [X86] do not align io start addr, so can    handle more pci cards  firmware [ARM] Do not re-enumerate the bus but instead    just use the configuration from the    bootloader. This is currently used on    IXP2000 systems where the bus has to be    configured a certain way for adjunct CPUs.  noearly  [X86] Don't do any early type 1 scanning.    This might help on some broken boards which    machine check when some devices' config space    is read. But various workarounds are disabled    and some IOMMU drivers will not work.  bfsort  Sort PCI devices into breadth-first order.    This sorting is done to get a device    order compatible with older (<= 2.4) kernels.  nobfsort Don't sort PCI devices into breadth-first order.  cbiosize=nn[KMG] The fixed amount of bus space which is    reserved for the CardBus bridge's IO window.    The default value is 256 bytes.  cbmemsize=nn[KMG] The fixed amount of bus space which is    reserved for the CardBus bridge's memory    window. The default value is 64 megabytes.  resource_alignment=    Format:    [@][:]:.[; ...]    Specifies alignment and device to reassign    aligned memory resources.    If  is not specified,    PAGE_SIZE is used as alignment.    PCI-PCI bridge can be specified, if resource    windows need to be expanded.  ecrc=  Enable/disable PCIe ECRC (transaction layer    end-to-end CRC checking).    bios: Use BIOS/firmware settings. This is the    the default.    off: Turn ECRC off    on: Turn ECRC on.  realloc  reallocate PCI resources if allocations done by BIOS    are erroneous. pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power   Management.  off Disable ASPM.  force Enable ASPM even on devices that claim not to support it.   WARNING: Forcing ASPM on may cause system lockups. pcie_ports= [PCIE] PCIe ports handling:  auto Ask the BIOS whether or not to use native PCIe services   associated with PCIe ports (PME, hot-plug, AER).  Use   them only if that is allowed by the BIOS.  native Use native PCIe services associated with PCIe ports   unconditionally.  compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe   ports driver. pcie_pme= [PCIE,PM] Native PCIe PME signaling options:  nomsi Do not use MSI for native PCIe PME signaling (this makes   all PCIe root ports use INTx for all services). pcmv=  [HW,PCMCIA] BadgePAD 4 pd.  [PARIDE]   See Documentation/blockdev/paride.txt. pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at   boot time.   Format: { 0 | 1 }   See arch/parisc/kernel/pdc_chassis.c percpu_alloc= Select which percpu first chunk allocator to use.   Currently supported values are "embed" and "page".   Archs may support subset or none of the selections.   See comments in mm/percpu.c for details on each   allocator.  This parameter is primarily for debugging   and performance comparison. pf.  [PARIDE]   See Documentation/blockdev/paride.txt. pg.  [PARIDE]   See Documentation/blockdev/paride.txt. pirq=  [SMP,APIC] Manual mp-table setup   See Documentation/x86/i386/IO-APIC.txt. plip=  [PPT,NET] Parallel port network link   Format: { parport | 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=0x508 pnp.debug [PNP]   Enable PNP debug messages.  This depends on the   CONFIG_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 autoconfiguration pnp_reserve_dma=   [ISAPNP] Exclude DMAs for the autoconfiguration pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration   Ranges are in pairs (I/O port base and size). pnp_reserve_mem=   [ISAPNP] Exclude memory regions for the   autoconfiguration.   Ranges are in pairs (memory base and size). ports=  [IP_VS_FTP] IPVS ftp helper module   Default is 21.   Up to 8 (IP_VS_APP_MAX_PORTS) ports   may be specified.   Format: ,.... print-fatal-signals=   [KNL] debug: print fatal signals   If enabled, warn about various signal handling   related application anomalies: too many signals,   too many POSIX.1 timers, fatal signals causing a   coredump - 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 line   Format:   (1/Y/y=enable, 0/N/n=disable) processor.max_cstate= [HW,ACPI]   Limit processor to maximum C-state   max_cstate=9 overrides any DMI blacklist limit. processor.nocst [HW,ACPI]   Ignore the _CST method to determine C-states,   instead using the legacy FADT method profile= [KNL] Enable kernel profiling via /proc/profile   Format: [schedule,]   Param: "schedule" - profile schedule points.   Param:  - step/bucket size as a power of 2 for    statistical time based profiling.   Param: "sleep" - profile D-state sleeping (millisecs).    Requires CONFIG_SCHEDSTATS   Param: "kvm" - profile VM exits. prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk   before loading.   See Documentation/blockdev/ramdisk.txt. psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to   probe for; one of (bare|imps|exps|lifebook|any). psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports   per 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-in   default number. quiet  [KNL] Disable most log messages r128=  [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 kilobytes   See Documentation/blockdev/ramdisk.txt. rcupdate.blimit= [KNL,BOOT]   Set maximum number of finished RCU callbacks to process   in one batch. rcupdate.qhimark= [KNL,BOOT]   Set threshold of queued   RCU callbacks over which batch limiting is disabled. rcupdate.qlowmark= [KNL,BOOT]   Set threshold of queued RCU callbacks below which   batch limiting is re-enabled. rdinit=  [KNL]   Format:    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 mode   Format: [,[,...]]   See arch/*/kernel/reboot.c or arch/*/kernel/process.c relax_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 area reservetop= [X86-32]   Format: nn[KMG]   Reserves a hole at the top of the kernel virtual   address space. reservelow= [X86]   Format: nn[K]   Set the amount of memory to reserve for BIOS at   the bottom of the address space. reset_devices [KNL] Force drivers to reset the underlying device   during initialization. resume=  [SWSUSP]   Specify the partition device for software suspend resume_offset= [SWSUSP]   Specify the offset from the beginning of the partition   given by "resume=" at which the swap header is located,   in  units (needed only for swap files).   See  Documentation/power/swsusp-and-swap-files.txt hibernate= [HIBERNATION]  noresume Don't check if there's a hibernation image    present during boot.  nocompress Don't compress/decompress hibernation images. retain_initrd [RAM] Keep initrd memory after extraction rhash_entries= [KNL,NET]   Set number of hash buckets for route cache riscom8= [HW,SERIAL]   Format: [,[,...]] ro  [KNL] Mount root device read-only on boot root=  [KNL] Root filesystem rootdelay= [KNL] Delay (in seconds) to pause before attempting to   mount the root filesystem rootflags= [KNL] Set root filesystem mount option string rootfstype= [KNL] Set root filesystem type rootwait [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 boot S  [KNL] Run init in single mode sa1100ir [NET]   See drivers/net/irda/sa1100_ir.c. sbni=  [NET] Granch SBNI12 leased line adapter sched_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 first   security module asking for security registration will be   loaded. An invalid security module name will be treated   as 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 used   later to disable prior to initial policy load. apparmor= [APPARMOR] Disable or enable AppArmor at boot time   Format: { "0" | "1" }   See security/apparmor/Kconfig help text   0 -- 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 settings   Format: {  }   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 the   culprit if slab objects become corrupted. Enabling   slub_debug can create guard zones around objects and   may poison objects when not in use. Also tracks the   last alloc / free. For more information see   Documentation/vm/slub.txt. slub_max_order= [MM, SLUB]   Determines the maximum allowed order for slabs.   A high setting may cause OOMs due to memory   fragmentation. For more information see   Documentation/vm/slub.txt. slub_min_objects= [MM, SLUB]   The minimum number of objects per slab. SLUB will   increase the slab order up to slub_max_order to   generate a sufficiently large slab able to contain   the number of objects indicated. The higher the number   of objects the smaller the overhead of tracking slabs   and 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 be   lower than slub_max_order.   For more information see Documentation/vm/slub.txt. slub_nomerge [MM, SLUB]   Disable merging of slabs with similar size. May be   necessary if there is some reason to distinguish   allocs to different slabs. Debug options disable   merging on their own.   For more information see Documentation/vm/slub.txt. smart2=  [HW]   Format: [,[,...,]] smp-alt-once [X86-32,SMP] On a hotplug CPU system, only   attempt to substitute SMP alternatives once at boot. smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port smsc-ircc2.ircc_sir= [HW] SIR base I/O port smsc-ircc2.ircc_fir= [HW] FIR base I/O port smsc-ircc2.ircc_irq= [HW] IRQ line smsc-ircc2.ircc_dma= [HW] DMA channel smsc-ircc2.ircc_transceiver= [HW] Transceiver type:    0: Toshiba Satellite 1800 (GP data pin select)    1: Fast pin select (default)    2: ATC IRMode softlockup_panic=   [KNL] Should the soft-lockup detector generate panics.   Format:  sonypi.*= [HW] Sony Programmable I/O Control Device driver   See Documentation/sonypi.txt specialix= [HW,SERIAL] Specialix multi-serial port adapter   See 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:    Set the STI (builtin display/keyboard on the HP-PARISC   machines) console (graphic card) which should be used   as 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:[:[:...]] sunrpc.min_resvport= sunrpc.max_resvport=   [NFS,SUNRPC]   SunRPC servers often require that client requests   originate from a privileged port (i.e. a port in the   range 0 < portnr < 1024).   An administrator who wishes to reserve some of these   ports for other uses may adjust the range that the   kernel's sunrpc client considers to be privileged   using these two parameters to set the minimum and   maximum port values. sunrpc.pool_mode=   [NFS]   Control how the NFS server code allocates CPUs to   service thread pools.  Depending on how many NICs   you have and where their interrupts are bound, this   option will affect which CPUs will do NFS serving.   Note: this parameter cannot be changed while the   NFS server is running.   auto     the server chooses an appropriate mode        automatically using heuristics   global     a single global pool contains all CPUs   percpu     one pool for each CPU   pernode     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 simultaneous   RPC calls that can be sent from the client to a   server. Increasing these values may allow you to   improve throughput, but will also increase the   amount of memory reserved for use by the client. swapaccount[=0|1]   [KNL] Enable accounting of swap in memory resource   controller if no parameter or 1 is given or disable   it if 0 is given (See Documentation/cgroups/memory.txt) swiotlb= [IA-64] Number of I/O TLB slabs switches= [HW,M68k] sysfs.deprecated=0|1 [KNL]   Enable/disable old style sysfs layout for old udev   on older distributions. When this option is enabled   very new udev will not work anymore. When this option   is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)   in older udev will not work anymore.   Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in   the kernel configuration. sysrq_always_enabled   [KNL]   Ignore sysrq setting - this boot parameter will   neutralize any effect of /proc/sys/kernel/sysrq.   Useful for debugging. tdfx=  [HW,DRM] test_suspend= [SUSPEND]   Specify "mem" (for Suspend-to-RAM) or "standby" (for   standby suspend) as the system sleep state to briefly   enter during system startup.  The system is woken from   this state using a wakeup-capable RTC alarm. thash_entries= [KNL,NET]   Set number of hash buckets for TCP connection thermal.act= [HW,ACPI]   -1: disable all active trip points in all thermal zones   : override all lowest active trip points thermal.crt= [HW,ACPI]   -1: disable all critical trip points in all thermal zones   : override all critical trip points thermal.nocrt= [HW,ACPI]   Set to disable actions on ACPI thermal zone   critical and hot trip points. thermal.off= [HW,ACPI]   1: disable ACPI thermal control thermal.psv= [HW,ACPI]   -1: disable all passive trip points   : override all passive trip points to this   value thermal.tzp= [HW,ACPI]   Specify global default ACPI thermal zone polling rate   : poll all this frequency   0: no polling (default) threadirqs [KNL]   Force threading of all interrupt handlers except those   marked explicitely IRQF_NO_THREAD. topology= [S390]   Format: {off | on}   Specify if the kernel should make use of the cpu   topology information if the hardware supports this.   The scheduler will make use of this information and   e.g. base its process migration decisions on it.   Default is on. tp720=  [HW,PS2] tpm_suspend_pcr=[HW,TPM]   Format: integer pcr id   Specify that at suspend time, the tpm driver   should extend the specified pcr with zeros,   as a workaround for some chips which fail to   flush the last written pcr on TPM_SaveState.   This will guarantee that all the other pcrs   are saved. trace_buf_size=nn[KMG]   [FTRACE] will set tracing buffer size. trace_event=[event-list]   [FTRACE] Set and start specified trace events in order   to facilitate early boot debugging.   See also Documentation/trace/events.txt tsc=  Disable clocksource stability checks for TSC.   Format:    [x86] reliable: mark tsc clocksource as reliable, this   disables clocksource verification at runtime, as well   as the stability checks done at bootup. Used to enable   high-resolution timer mode on older hardware, and in   virtualized environment.   [x86] noirqtime: Do not use TSC to do irq accounting.   Used to run time disable IRQ_TIME_ACCOUNTING on any   platforms where RDTSC is slow and this accounting   can add overhead. turbografx.map[2|3]= [HW,JOY]   TurboGraFX parallel port interface   Format:   ,,,,,,,   See also Documentation/input/joystick-parport.txt uhash_entries= [KNL,NET]   Set number of hash buckets for UDP/UDP-Lite connections uhci-hcd.ignore_oc=   [USB] Ignore overcurrent events (default N).   Some badly-designed motherboards generate lots of   bogus events, for ports that aren't wired to   anything.  Set this parameter to avoid log spamming.   Note that genuine overcurrent events won't be   reported either. unknown_nmi_panic   [X86] Cause panic on unknown NMI. usbcore.autosuspend=   [USB] The autosuspend time delay (in seconds) used   for newly-detected USB devices (default 2).  This   is the time required before an idle device will be   autosuspended.  Devices for which the delay is set   to 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 initialization   scheme (default 0 = off). usbcore.use_both_schemes=   [USB] Try the other device initialization scheme   if 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 is   scanned for Logical Units (default 5). usb-storage.quirks=   [UMS] A list of quirks entries to supplement or   override the built-in unusual_devs list.  List   entries are separated by commas.  Each entry has   the form VID:PID:Flags where VID and PID are Vendor   and Product ID values (4-digit hex numbers) and   Flags is a set of characters, each corresponding   to a common usb-storage quirk flag as follows:    a = SANE_SENSE (collect more than 18 bytes     of sense data);    b = BAD_SENSE (don't collect more than 18     bytes of sense data);    c = FIX_CAPACITY (decrease the reported     device capacity by one sector);    d = NO_READ_DISC_INFO (don't use     READ_DISC_INFO command);    e = NO_READ_CAPACITY_16 (don't use     READ_CAPACITY_16 command);    h = CAPACITY_HEURISTICS (decrease the     reported device capacity by one     sector if the number is odd);    i = IGNORE_DEVICE (don't bind to this     device);    l = NOT_LOCKABLE (don't try to lock and     unlock ejectable media);    m = MAX_SECTORS_64 (don't transfer more     than 64 sectors = 32 KB at a time);    n = INITIAL_READ10 (force a retry of the     initial READ(10) command);    o = CAPACITY_OK (accept the capacity     reported by the device);    r = IGNORE_RESIDUE (the device reports     bogus residue values);    s = SINGLE_LUN (the device has only one     Logical Unit);    w = NO_WP_DETECT (don't test whether the     medium is write-protected).   Example: quirks=0419:aaf5:rl,0421:0433:rc userpte=   [X86] Flags controlling user PTE allocations.    nohigh = do not allocate PTE pages in     HIGHMEM regardless of setting     of CONFIG_HIGHPTE. vdso=  [X86,SH]   vdso=2: enable compat VDSO (default with COMPAT_VDSO)   vdso=1: enable VDSO (default)   vdso=0: disable VDSO mapping vdso32=  [X86]   vdso32=2: enable compat VDSO (default with COMPAT_VDSO)   vdso32=1: enable 32-bit VDSO (default)   vdso32=0: disable 32-bit VDSO mapping vector=  [IA-64,SMP]   vector=percpu: enable percpu vector domain video=  [FB] Frame buffer configuration   See Documentation/fb/modedb.txt. vga=  [BOOT,X86-32] Select a particular video mode   See Documentation/x86/boot.txt and   Documentation/svga.txt.   Use vga=ask for menu.   This is actually a boot loader parameter; the value is   passed to the kernel using a special protocol. vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact   size of . This can be used to increase the   minimum size (128MB on x86). It can also be used to   decrease the size and leave more room for directly   mapped kernel RAM. vmhalt=  [KNL,S390] Perform z/VM CP command after system halt.   Format:  vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.   Format:  vmpoff=  [KNL,S390] Perform z/VM CP command after power off.   Format:  vt.cur_default= [VT] Default cursor shape.   Format: 0xCCBBAA, where AA, BB, and CC are the same as   the parameters of the [?A;B;Cc escape sequence;   see VGA-softcursor.txt. Default: 2 = underline. vt.default_blu= [VT]   Format: ,,,...,   Change the default blue palette of the console.   This is a 16-member array composed of values   ranging from 0-255. vt.default_grn= [VT]   Format: ,,,...,   Change the default green palette of the console.   This is a 16-member array composed of values   ranging from 0-255. vt.default_red= [VT]   Format: ,,,...,   Change the default red palette of the console.   This is a 16-member array composed of values   ranging 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 all   newly opened terminals. vt.global_cursor_default=   [VT]   Format=<-1|0|1>   Set system-wide default for whether a cursor   is shown on new VTs. Default is -1,   i.e. cursors will be created by default unless   overridden by individual drivers. 0 will hide   cursors, 1 will display them. watchdog timers [HW,WDT] For information on watchdog timers,   see Documentation/watchdog/watchdog-parameters.txt   or other driver-specific files in the   Documentation/watchdog/ directory. x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of   default x2apic cluster mode on platforms   supporting x2apic. x86_mrst_timer= [X86-32,APBT]   Choose timer option for x86 Moorestown MID platform.   Two valid options are apbt timer only and lapic timer   plus one apbt timer for broadcast timer.   x86_mrst_timer=apbt_only | lapic_and_apbt xd=  [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 devices   Format: [unplug0,][unplug1]   ide-disks -- unplug primary master IDE devices   aux-ide-disks -- unplug non-primary-master IDE devices   nics -- unplug network devices   all -- unplug all emulated devices (NICs and IDE disks)   unnecessary -- unplugging emulated devices is    unnecessary even if the host did not respond to    the unplug protocol   never -- do not unplug even if version check succeeds xirc2ps_cs= [NET,PCMCIA]   Format:   ,,,,,[,[,[,]]]______________________________________________________________________TODO: Add more DRM drivers.


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