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+ 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 a
+case insensitive manner), and with descriptions where known.
+
+Module parameters for loadable modules are specified only as the
+parameter name with optional '=' and value as appropriate, such as:
+
+ modprobe usbcore blinkenlights=1
+
+Module parameters for modules that are built into the kernel image
+are specified on the kernel command line with the module name plus
+'.' plus parameter name, with '=' and value if appropriate, such as:
+
+ usbcore.blinkenlights=1
+
+Hyphens (dashes) and underscores are equivalent in parameter names, so
+ log_buf_len=1M print-fatal-signals=1
+can also be entered as
+ log-buf-len=1M print_fatal_signals=1
+
+
+This document may not be entirely up to date and comprehensive. The command
+"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
+module. Loadable modules, after being loaded into the running kernel, also
+reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
+parameters 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 were
+enabled and if respective hardware is present. The text in square brackets at
+the beginning of each description states the restrictions within which a
+parameter 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.
+ ARM ARM architecture 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.
+ EVM Extended Verification Module
+ FB The frame buffer device is enabled.
+ FTRACE Function tracing 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.
+ MDA MDA console support is enabled.
+ MIPS MIPS architecture 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.
+ 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.
+ VMMIO Driver for memory mapped virtio devices 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 32-bit or 64-bit x86 (same as X86-32+X86-64)
+ XEN Xen support is enabled
+
+In 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 boot
+loader, and have no meaning to the kernel directly.
+Do not modify the syntax of boot loader parameters without extreme
+need 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 that
+a trailing = on the name of any parameter states that that parameter will
+be entered as an environment variable, whereas its absence indicates that
+it will appear as a kernel argument readable via /proc/cmdline by programs
+running once the system is up.
+
+The number of kernel parameters is not limited, but the length of the
+complete command line (parameters including spaces etc.) is limited to
+a fixed number of characters. This limit depends on the architecture
+and 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 kernel
+parameter values. These 'K', 'M', and 'G' letters represent the _binary_
+multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
+bytes 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/runtime_pm.txt, pci=noacpi
+
+ acpi_rsdp= [ACPI,EFI,KEXEC]
+ Pass the RSDP address to the kernel, mostly used
+ on machines running EFI runtime service to boot the
+ second kernel for kdump.
+
+ acpi_apic_instance= [ACPI, IOAPIC]
+ Format: <int>
+ 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: <int>
+ 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: <irq>,<irq>...
+
+ acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
+ use by PCI
+ Format: <irq>,<irq>...
+
+ 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.
+
+ align_va_addr= [X86-64]
+ Align virtual addresses by clearing slice [14:12] when
+ allocating a VMA at process creation time. This option
+ gives you up to 3% performance improvement on AMD F15h
+ machines (where it is enabled by default) for a
+ CPU-intensive style benchmark, and it can vary highly in
+ a microbenchmark depending on workload and compiler.
+
+ 32: only for 32-bit processes
+ 64: only for 64-bit processes
+ on: enable for both 32- and 64-bit processes
+ off: disable for both 32- and 64-bit processes
+
+ amd_iommu= [HW,X86-64]
+ 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
+ force_isolation - Force device isolation for all
+ devices. The IOMMU driver is not
+ allowed anymore to lift isolation
+ requirements as needed. This option
+ does not override iommu=pt
+
+ amd_iommu_dump= [HW,X86-64]
+ Enable AMD IOMMU driver option to dump the ACPI table
+ for AMD IOMMU. With this option enabled, AMD IOMMU
+ driver will print ACPI tables for AMD IOMMU during
+ IOMMU initialization.
+
+ amijoy.map= [HW,JOY] Amiga joystick support
+ Map of devices attached to JOY0DAT and JOY1DAT
+ Format: <a>,<b>
+ See also Documentation/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: <type1>,<type2>,..<type16>
+
+ 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: <io>,<irq>,<nodeID>
+
+ 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: <int> (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: <bool> (0 = real, 1 = synthetic (default))
+
+ atkbd.softrepeat= [HW]
+ Use software keyboard repeat
+
+ baycom_epp= [HW,AX25]
+ Format: <io>,<mode>
+
+ baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
+ Format: <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 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=
+
+ 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.
+
+ 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: <string>
+ 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.
+
+ cma=nn[MG] [ARM,KNL]
+ Sets the size of kernel global memory area for contiguous
+ memory allocations. For more information, see
+ include/linux/dma-contiguous.h
+
+ 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
+
+ coherent_pool=nn[KMG] [ARM,KNL]
+ Sets the size of memory pool for coherent, atomic dma
+ allocations, by default set to 256K.
+
+ 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:
+ <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 device
+ conmode=
+
+ 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 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,<addr>[,options]
+ uart[8250],mmio,<addr>[,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.
+ hvc<n> Use the hypervisor console device <n>. This is for
+ both Xen and PowerPC hypervisors.
+
+ 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/<pid>/coredump_filter.
+ See also Documentation/filesystems/proc.txt.
+
+ cpuidle.off=1 [CPU_IDLE]
+ disable the cpuidle sub-system
+
+ cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
+ Format:
+ <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 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_low=size[KMG]
+ [KNL, x86] parts under 4G.
+
+ 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: <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.txt
+
+ ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
+ time. See Documentation/dynamic-debug-howto.txt for
+ details. Deprecated, see dyndbg.
+
+ 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
+
+ debug_guardpage_minorder=
+ [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
+ parameter allows control of the order of pages that will
+ be intentionally kept free (and hence protected) by the
+ buddy allocator. Bigger value increase the probability
+ of catching random memory corruption, but reduce the
+ amount of memory for normal system use. The maximum
+ possible value is MAX_ORDER/2. Setting this parameter
+ to 1 or 2 should be enough to identify most random
+ memory corruption problems caused by bugs in kernel or
+ driver code when a CPU writes to (or reads from) a
+ random memory location. Note that there exists a class
+ of memory corruptions problems caused by buggy H/W or
+ F/W or by drivers badly programing DMA (basically when
+ memory is written at bus level and the CPU MMU is
+ bypassed) which are not detectable by
+ CONFIG_DEBUG_PAGEALLOC, hence this option will not help
+ tracking down these problems.
+
+ debugpat [X86] Enable PAT debugging
+
+ decnet.addr= [HW,NET]
+ Format: <area>[,<node>]
+ 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=<number>
+ 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=<driver_name>
+ 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.
+
+ drm_kms_helper.edid_firmware=[<connector>:]<file>
+ Broken monitors, graphic adapters and KVMs may
+ send no or incorrect EDID data sets. This parameter
+ allows to specify an EDID data set in the
+ /lib/firmware directory that is used instead.
+ Generic built-in EDID data sets are used, if one of
+ edid/1024x768.bin, edid/1280x1024.bin,
+ edid/1680x1050.bin, or edid/1920x1080.bin is given
+ and no file with the same name exists. Details and
+ instructions how to build your own EDID data are
+ available in Documentation/EDID/HOWTO.txt. An EDID
+ data set will only be used for a particular connector,
+ if its name and a colon are prepended to the EDID
+ name.
+
+ dscc4.setup= [NET]
+
+ dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
+ module.dyndbg[="val"]
+ Enable debug messages at boot time. See
+ Documentation/dynamic-debug-howto.txt for details.
+
+ 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 8250/16550
+ UART at the specified I/O port or MMIO address.
+ MMIO inter-register address stride is either 8-bit
+ (mmio) or 32-bit (mmio32).
+ The options are the same as for ttyS, above.
+
+ earlyprintk= [X86,SH,BLACKFIN]
+ earlyprintk=vga
+ earlyprintk=xen
+ 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.
+
+ The xen output can only be used by Xen PV guests.
+
+ 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/cfq-iosched.txt and
+ Documentation/block/deadline-iosched.txt for details.
+
+ elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
+ Specifies physical address of start of kernel core
+ image elf header and optionally the size. 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.
+
+ evm= [EVM]
+ Format: { "fix" }
+ Permit 'security.evm' to be updated regardless of
+ current integrity status.
+
+ 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 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: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
+ 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.
+
+ grcan.enable0= [HW] Configuration of physical interface 0. Determines
+ the "Enable 0" bit of the configuration register.
+ Format: 0 | 1
+ Default: 0
+ grcan.enable1= [HW] Configuration of physical interface 1. Determines
+ the "Enable 0" bit of the configuration register.
+ Format: 0 | 1
+ Default: 0
+ grcan.select= [HW] Select which physical interface to use.
+ Format: 0 | 1
+ Default: 0
+ grcan.txsize= [HW] Sets the size of the tx buffer.
+ Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
+ Default: 1024
+ grcan.rxsize= [HW] Sets the size of the rx buffer.
+ Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
+ Default: 1024
+
+ hashdist= [KNL,NUMA] Large hashes allocated during boot
+ are distributed across NUMA nodes. Defaults on
+ for 64-bit 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: <cyl>,<head>,<sect>
+
+ 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 <nn>. 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.
+
+ hwthread_map= [METAG] Comma-separated list of Linux cpu id to
+ hardware thread id mappings.
+ Format: <cpu>:<hwthread>
+
+ 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:
+ <bus_id>,<clkrate>
+
+ 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 controller
+ 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.
+
+ i915.invert_brightness=
+ [DRM] Invert the sense of the variable that is used to
+ set the brightness of the panel backlight. Normally a
+ brightness value of 0 indicates backlight switched off,
+ and the maximum of the brightness value sets the backlight
+ to maximum brightness. If this parameter is set to 0
+ (default) and the machine requires it, or this parameter
+ is set to 1, a brightness value of 0 sets the backlight
+ to maximum brightness, and the maximum of the brightness
+ value switches the backlight off.
+ -1 -- never invert brightness
+ 0 -- machine default
+ 1 -- force brightness inversion
+
+ icn= [HW,ISDN]
+ Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
+
+ 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=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=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.
+ We also add it as printk module parameter, so users
+ could change it dynamically, usually by
+ /sys/module/printk/parameters/ignore_loglevel.
+
+ ihash_entries= [KNL]
+ Set number of hash buckets for inode cache.
+
+ ima_appraise= [IMA] appraise integrity measurements
+ Format: { "off" | "enforce" | "fix" }
+ default: "enforce"
+
+ ima_appraise_tcb [IMA]
+ The builtin appraise policy appraises all files
+ owned by uid=0.
+
+ 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: <full_path>
+ 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: <irq>
+
+ 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.
+
+ intel_idle.max_cstate= [KNL,HW,ACPI,X86]
+ 0 disables intel_idle and fall back on acpi_idle.
+ 1 to 6 specify maximum depth of C-state.
+
+ intel_pstate= [X86]
+ disable
+ Do not enable intel_pstate as the default
+ scaling driver for the supported processors
+
+ intremap= [X86-64, Intel-IOMMU]
+ on enable Interrupt Remapping (default)
+ off disable Interrupt Remapping
+ nosid disable Source ID checking
+ no_x2apic_optout
+ BIOS x2APIC opt-out request will be ignored
+
+ 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, IA-64]
+
+
+ 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.
+
+ irqaffinity= [SMP] Set the default irq affinity mask
+ 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>
+
+ 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: <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 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.
+ <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. 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: <Controller#>[,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: <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 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.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 64-bit or 32-bit PAE mode.
+
+ 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.nested=
+ [KVM,Intel] Enable VMX nesting (nVMX).
+ Default is 0 (disabled)
+
+ 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= [x86,APIC] "notscdeadline" Do not use TSC deadline
+ value for LAPIC timer one-shot implementation. Default
+ back to the programmable timer unit in the LAPIC.
+
+ 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: <int>
+
+ 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.
+
+ * rstonce: only attempt one reset during
+ hot-unplug link recovery
+
+ * 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: <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 Driver
+ Format: <irq>
+
+ 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: <io>,<irq>,<dma>
+
+ mac= [NET]
+ Used ASIX drivers.
+ Example: mac=12:34:56:78:ab:cd
+
+ machvec= [IA-64] 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] The number of loop block devices that get
+ (loop.max_loop) unconditionally pre-created at init time. The default
+ number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
+ of statically allocating a predefined number, loop
+ devices can be requested on-demand with the
+ /dev/loop-control interface.
+
+ 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: <first>,<last>
+ 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] Work as limiting max address. 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: <integer>
+ default : 0 <disable>
+ 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.
+
+ module.sig_enforce
+ [KNL] When CONFIG_MODULE_SIG is set, this means that
+ modules without (valid) signatures will fail to load.
+ Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
+ is always true, so this option does nothing.
+
+ 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: <msecs>
+ 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: <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 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: <integer>
+ 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: <irq>,<io>,<mem_start>,<mem_end>,<name>
+ 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.max_session_slots=
+ [NFSv4.1] Sets the maximum number of session slots
+ the client will attempt to negotiate with the server.
+ This limits the number of simultaneous RPC requests
+ that the client can send to the NFSv4.1 server.
+ Note that there is little point in setting this
+ value higher than the max_tcp_slot_table_limit.
+
+ nfs.nfs4_disable_idmapping=
+ [NFSv4] When set to the default of '1', this option
+ ensures that both the RPC level authentication
+ scheme and the NFS level operations agree to use
+ numeric uids/gids if the mount is using the
+ 'sec=sys' security flavour. In effect it is
+ disabling idmapping, which can make migration from
+ legacy NFSv2/v3 systems to NFSv4 easier.
+ Servers that do not support this mode of operation
+ will be autodetected by the client, and it will fall
+ back to using the idmapper.
+ To turn off this behaviour, set the value to '0'.
+ nfs.nfs4_unique_id=
+ [NFS4] Specify an additional fixed unique ident-
+ ification string that NFSv4 clients can insert into
+ their nfs_client_id4 string. This is typically a
+ UUID that is generated at system install time.
+
+ nfs.send_implementation_id =
+ [NFSv4.1] Send client implementation identification
+ information in exchange_id requests.
+ If zero, no implementation identification information
+ will be sent.
+ The default is to send the implementation identification
+ information.
+
+ nfsd.nfs4_disable_idmapping=
+ [NFSv4] When set to the default of '1', the NFSv4
+ server will return only numeric uids and gids to
+ clients using auth_sys, and will accept numeric uids
+ and gids from such clients. This is intended to ease
+ migration from NFSv2/v3.
+
+ objlayoutdriver.osd_login_prog=
+ [NFS] [OBJLAYOUT] sets the pathname to the program which
+ is used to automatically discover and login into new
+ osd-targets. Please see:
+ Documentation/filesystems/pnfs.txt for more explanations
+
+ 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.
+ To facilitate more flexible debugging, we also add
+ console_suspend, a printk module parameter to control
+ it. Users could use console_suspend (usually
+ /sys/module/printk/parameters/console_suspend) to
+ turn on/off it dynamically.
+
+ 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
+
+ nosmap [X86]
+ Disable SMAP (Supervisor Mode Access Prevention)
+ even if it is supported by processor.
+
+ nosmep [X86]
+ Disable SMEP (Supervisor Mode Execution Prevention)
+ 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.
+
+ eagerfpu= [X86]
+ on enable eager fpu restore
+ off disable eager fpu restore
+ auto selects the default scheme, which automatically
+ enables eagerfpu restore for xsaveopt.
+
+ 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_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 [IA-64] 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.
+
+ no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
+ steal time is computed, but won't influence scheduler
+ behaviour
+
+ 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).
+
+ nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
+ shutdown the other cpus. Instead use the REBOOT_VECTOR
+ irq.
+
+ nomodule Disable module load
+
+ 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.
+
+ nordrand [X86] Disable the direct use of the RDRAND
+ instruction even if it is supported by the
+ processor. RDRAND is still available to user
+ space applications.
+
+ 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.
+
+ cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
+ CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
+ Some features depend on CPU0. Known dependencies are:
+ 1. Resume from suspend/hibernate depends on CPU0.
+ Suspend/hibernate will fail if CPU0 is offline and you
+ need to online CPU0 before suspend/hibernate.
+ 2. PIC interrupts also depend on CPU0. CPU0 can't be
+ removed if a PIC interrupt is detected.
+ It's said poweroff/reboot may depend on CPU0 on some
+ machines although I haven't seen such issues so far
+ after CPU0 is offline on a few tested machines.
+ If the dependencies are under your control, you can
+ turn on cpu0_hotplug.
+
+ nptcg= [IA-64] 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_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
+ Allowed values are enable and disable
+
+ 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: <mux_mode0.mode_name=value>...
+ 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.
+ timer: [X86] Force use of architectural NMI
+ timer mode (see also oprofile.timer
+ for generic hr timer mode)
+ [s390] Force legacy basic mode sampling
+ (report cpu_type "timer")
+
+ 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 <timeout>
+ timeout > 0: seconds before rebooting
+ timeout = 0: wait forever
+ timeout < 0: reboot immediately
+ Format: <timeout>
+
+ parkbd.port= [HW] Parallel port number the keyboard adapter is
+ connected 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 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.
+ pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
+ tuning and use the BIOS-configured MPS defaults.
+ pcie_bus_safe Set every device's MPS to the largest value
+ supported by all devices below the root complex.
+ pcie_bus_perf Set device MPS to the largest allowable MPS
+ based on its parent bus. Also set MRRS (Max
+ Read Request Size) to the largest supported
+ value (no larger than the MPS that the device
+ or bus can support) for best performance.
+ pcie_bus_peer2peer Set every device's MPS to 128B, which
+ every device is guaranteed to support. This
+ configuration allows peer-to-peer DMA between
+ any pair of devices, possibly at the cost of
+ reduced performance. This also guarantees
+ that hot-added devices will work.
+ 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:
+ [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
+ Specifies alignment and device to reassign
+ aligned memory resources.
+ If <order of align> 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.
+ hpiosize=nn[KMG] The fixed amount of bus space which is
+ reserved for hotplug bridge's IO window.
+ Default size is 256 bytes.
+ hpmemsize=nn[KMG] The fixed amount of bus space which is
+ reserved for hotplug bridge's memory window.
+ Default size is 2 megabytes.
+ realloc= Enable/disable reallocating PCI bridge resources
+ if allocations done by BIOS are too small to
+ accommodate resources required by all child
+ devices.
+ off: Turn realloc off
+ on: Turn realloc on
+ realloc same as realloc=on
+ noari do not use PCIe ARI.
+ pcie_scan_all Scan all possible PCIe devices. Otherwise we
+ only look for one device below a PCIe downstream
+ port.
+
+ 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_hp= [PCIE] PCI Express Hotplug driver options:
+ nomsi Do not use MSI for PCI Express Native Hotplug (this
+ makes all PCIe ports use INTx for hotplug services).
+
+ 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<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=0x508
+
+ pnp.debug=1 [PNP]
+ Enable PNP debug messages (depends on the
+ CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
+ via /sys/module/pnp/parameters/debug. We always show
+ current resource usage; turning this on also shows
+ possible settings and some assignment information.
+
+ 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: <port>,<port>....
+
+ 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.always_kmsg_dump=
+ Trigger kmsg_dump for cases other than kernel oops or
+ panics
+ Format: <bool> (1/Y/y=enable, 0/N/n=disable)
+ default: disabled
+
+ printk.time= Show timing data prefixed to each printk message line
+ Format: <bool> (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,]<number>
+ Param: "schedule" - profile schedule points.
+ Param: <number> - 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).
+
+ pstore.backend= Specify the name of the pstore backend to use
+
+ 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.
+
+ rcu_nocbs= [KNL,BOOT]
+ In kernels built with CONFIG_RCU_NOCB_CPU=y, set
+ the specified list of CPUs to be no-callback CPUs.
+ Invocation of these CPUs' RCU callbacks will
+ be offloaded to "rcuoN" kthreads created for
+ that purpose. This reduces OS jitter on the
+ offloaded CPUs, which can be useful for HPC and
+ real-time workloads. It can also improve energy
+ efficiency for asymmetric multiprocessors.
+
+ rcu_nocb_poll [KNL,BOOT]
+ Rather than requiring that offloaded CPUs
+ (specified by rcu_nocbs= above) explicitly
+ awaken the corresponding "rcuoN" kthreads,
+ make these kthreads poll for callbacks.
+ This improves the real-time response for the
+ offloaded CPUs by relieving them of the need to
+ wake up the corresponding kthread, but degrades
+ energy efficiency by requiring that the kthreads
+ periodically wake up to do the polling.
+
+ rcutree.blimit= [KNL,BOOT]
+ Set maximum number of finished RCU callbacks to process
+ in one batch.
+
+ rcutree.fanout_leaf= [KNL,BOOT]
+ Increase the number of CPUs assigned to each
+ leaf rcu_node structure. Useful for very large
+ systems.
+
+ rcutree.qhimark= [KNL,BOOT]
+ Set threshold of queued
+ RCU callbacks over which batch limiting is disabled.
+
+ rcutree.qlowmark= [KNL,BOOT]
+ Set threshold of queued RCU callbacks below which
+ batch limiting is re-enabled.
+
+ rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
+ Suppress RCU CPU stall warning messages.
+
+ rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
+ Set timeout for RCU CPU stall warning messages.
+
+ rcutree.jiffies_till_first_fqs= [KNL,BOOT]
+ Set delay from grace-period initialization to
+ first attempt to force quiescent states.
+ Units are jiffies, minimum value is zero,
+ and maximum value is HZ.
+
+ rcutree.jiffies_till_next_fqs= [KNL,BOOT]
+ Set delay between subsequent attempts to force
+ quiescent states. Units are jiffies, minimum
+ value is one, and maximum value is HZ.
+
+ rcutorture.fqs_duration= [KNL,BOOT]
+ Set duration of force_quiescent_state bursts.
+
+ rcutorture.fqs_holdoff= [KNL,BOOT]
+ Set holdoff time within force_quiescent_state bursts.
+
+ rcutorture.fqs_stutter= [KNL,BOOT]
+ Set wait time between force_quiescent_state bursts.
+
+ rcutorture.irqreader= [KNL,BOOT]
+ Test RCU readers from irq handlers.
+
+ rcutorture.n_barrier_cbs= [KNL,BOOT]
+ Set callbacks/threads for rcu_barrier() testing.
+
+ rcutorture.nfakewriters= [KNL,BOOT]
+ Set number of concurrent RCU writers. These just
+ stress RCU, they don't participate in the actual
+ test, hence the "fake".
+
+ rcutorture.nreaders= [KNL,BOOT]
+ Set number of RCU readers.
+
+ rcutorture.onoff_holdoff= [KNL,BOOT]
+ Set time (s) after boot for CPU-hotplug testing.
+
+ rcutorture.onoff_interval= [KNL,BOOT]
+ Set time (s) between CPU-hotplug operations, or
+ zero to disable CPU-hotplug testing.
+
+ rcutorture.shuffle_interval= [KNL,BOOT]
+ Set task-shuffle interval (s). Shuffling tasks
+ allows some CPUs to go into dyntick-idle mode
+ during the rcutorture test.
+
+ rcutorture.shutdown_secs= [KNL,BOOT]
+ Set time (s) after boot system shutdown. This
+ is useful for hands-off automated testing.
+
+ rcutorture.stall_cpu= [KNL,BOOT]
+ Duration of CPU stall (s) to test RCU CPU stall
+ warnings, zero to disable.
+
+ rcutorture.stall_cpu_holdoff= [KNL,BOOT]
+ Time to wait (s) after boot before inducing stall.
+
+ rcutorture.stat_interval= [KNL,BOOT]
+ Time (s) between statistics printk()s.
+
+ rcutorture.stutter= [KNL,BOOT]
+ Time (s) to stutter testing, for example, specifying
+ five seconds causes the test to run for five seconds,
+ wait for five seconds, and so on. This tests RCU's
+ ability to transition abruptly to and from idle.
+
+ rcutorture.test_boost= [KNL,BOOT]
+ Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
+ "Maybe" means test if the RCU implementation
+ under test support RCU priority boosting.
+
+ rcutorture.test_boost_duration= [KNL,BOOT]
+ Duration (s) of each individual boost test.
+
+ rcutorture.test_boost_interval= [KNL,BOOT]
+ Interval (s) between each boost test.
+
+ rcutorture.test_no_idle_hz= [KNL,BOOT]
+ Test RCU's dyntick-idle handling. See also the
+ rcutorture.shuffle_interval parameter.
+
+ rcutorture.torture_type= [KNL,BOOT]
+ Specify the RCU implementation to test.
+
+ rcutorture.verbose= [KNL,BOOT]
+ Enable additional printk() statements.
+
+ 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 mode
+ Format: <reboot_mode>[,<reboot_mode2>[,...]]
+ 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
+ Format:
+ {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
+
+ resume_offset= [SWSUSP]
+ Specify the offset from the beginning of the partition
+ given 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.txt
+
+ resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
+ read the resume files
+
+ resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
+ Useful for devices that are detected asynchronously
+ (e.g. USB and MMC devices).
+
+ 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: <io_board1>[,<io_board2>[,...<io_boardN>]]
+
+ ro [KNL] Mount root device read-only on boot
+
+ root= [KNL] Root filesystem
+ See name_to_dev_t comment in init/do_mounts.c.
+
+ 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.
+
+ skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
+ xtime_lock contention on larger systems, and/or RCU lock
+ contention on all systems with CONFIG_MAXSMP set.
+ Format: { "0" | "1" }
+ 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
+ 1 -- enable.
+ Note: increases power consumption, thus should only be
+ enabled if running jitter sensitive (HPC/RT) workloads.
+
+ 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: { <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]
+
+ slab_max_order= [MM, SLAB]
+ Determines the maximum allowed order for slabs.
+ A high setting may cause OOMs due to memory
+ fragmentation. Defaults to 1 for systems with
+ more than 32MB of RAM, 0 otherwise.
+
+ 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 minimum 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: <io1>[,<io2>[,...,<io8>]]
+
+ 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: <integer>
+
+ sonypi.*= [HW] Sony Programmable I/O Control Device driver
+ See Documentation/laptops/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.
+
+ stacktrace_filter=[function-list]
+ [FTRACE] Limit the functions that the stack tracer
+ will trace at boot up. function-list is a comma separated
+ list of functions. This list can be changed at run
+ time by the stack_trace_filter file in the debugfs
+ tracing directory. Note, this enables stack tracing
+ and the stacktrace above is not needed.
+
+ sti= [PARISC,HW]
+ Format: <num>
+ 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:<bpp1>[:<bpp2>[:<bpp3>...]]
+
+ 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
+ <degrees C>: override all lowest active trip points
+
+ thermal.crt= [HW,ACPI]
+ -1: disable all critical trip points in all thermal zones
+ <degrees C>: 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
+ <degrees C>: override all passive trip points to this
+ value
+
+ thermal.tzp= [HW,ACPI]
+ Specify global default ACPI thermal zone polling rate
+ <deci-seconds>: poll all this frequency
+ 0: no polling (default)
+
+ threadirqs [KNL]
+ Force threading of all interrupt handlers except those
+ marked explicitly 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
+
+ trace_options=[option-list]
+ [FTRACE] Enable or disable tracer options at boot.
+ The option-list is a comma delimited list of options
+ that can be enabled or disabled just as if you were
+ to echo the option name into
+
+ /sys/kernel/debug/tracing/trace_options
+
+ For example, to enable stacktrace option (to dump the
+ stack trace of each event), add to the command line:
+
+ trace_options=stacktrace
+
+ See also Documentation/trace/ftrace.txt "trace options"
+ section.
+
+ transparent_hugepage=
+ [KNL]
+ Format: [always|madvise|never]
+ Can be used to control the default behavior of the system
+ with respect to transparent hugepages.
+ See Documentation/vm/transhuge.txt for more details.
+
+ tsc= Disable clocksource stability checks for TSC.
+ Format: <string>
+ [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:
+ <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
+ See also Documentation/input/joystick-parport.txt
+
+ udbg-immortal [PPC] When debugging early kernel crashes that
+ happen after console_init() and before a proper
+ console driver takes over, this boot options might
+ help "seeing" what's going on.
+
+ 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.authorized_default=
+ [USB] Default USB device authorization:
+ (default -1 = authorized except for wireless USB,
+ 0 = not authorized, 1 = authorized)
+
+ 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.usbfs_memory_mb=
+ [USB] Memory limit (in MB) for buffers allocated by
+ usbfs (default = 16, 0 = max = 2047).
+
+ 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);
+ p = WRITE_CACHE (the device cache is ON
+ by default);
+ 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
+
+ user_debug= [KNL,ARM]
+ Format: <int>
+ See arch/arm/Kconfig.debug help text.
+ 1 - undefined instruction events
+ 2 - system calls
+ 4 - invalid data aborts
+ 8 - SIGSEGV faults
+ 16 - SIGBUS faults
+ Example: user_debug=31
+
+ 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.
+
+ virtio_mmio.device=
+ [VMMIO] Memory mapped virtio (platform) device.
+
+ <size>@<baseaddr>:<irq>[:<id>]
+ where:
+ <size> := size (can use standard suffixes
+ like K, M and G)
+ <baseaddr> := physical base address
+ <irq> := interrupt number (as passed to
+ request_irq())
+ <id> := (optional) platform device id
+ example:
+ virtio_mmio.device=1K@0x100b0000:48:7
+
+ Can be used multiple times for multiple devices.
+
+ 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 <nn>. 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: <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>
+
+ vsyscall= [X86-64]
+ Controls the behavior of vsyscalls (i.e. calls to
+ fixed addresses of 0xffffffffff600x00 from legacy
+ code). Most statically-linked binaries and older
+ versions of glibc use these calls. Because these
+ functions are at fixed addresses, they make nice
+ targets for exploits that can control RIP.
+
+ emulate [default] Vsyscalls turn into traps and are
+ emulated reasonably safely.
+
+ native Vsyscalls are native syscall instructions.
+ This is a little bit faster than trapping
+ and makes a few dynamic recompilers work
+ better than they would in emulation mode.
+ It also makes exploits much easier to write.
+
+ none Vsyscalls don't work at all. This makes
+ them quite hard to use for exploits but
+ might break your system.
+
+ vt.cur_default= [VT] Default cursor shape.
+ Format: 0xCCBBAA, where AA, BB, and CC are the same as
+ the 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 values
+ ranging 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 values
+ ranging 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 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:
+ <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
+
+______________________________________________________________________
+
+TODO:
+
+ Add more DRM drivers.