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| author | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-09-21 09:51:11 -0300 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-10-24 08:12:35 -0200 |
| commit | 9d85025b0418163fae079c9ba8f8445212de8568 (patch) | |
| tree | 4629e2dedf4a9ed45a6855c129101f9b52138372 /Documentation/kernel-parameters.txt | |
| parent | 186128f75392f8478ad1b32a675627d738881ca4 (diff) | |
| download | linux-9d85025b0418163fae079c9ba8f8445212de8568.tar.gz linux-9d85025b0418163fae079c9ba8f8445212de8568.tar.bz2 linux-9d85025b0418163fae079c9ba8f8445212de8568.zip | |
docs-rst: create an user's manual book
Place README, REPORTING-BUGS, SecurityBugs and kernel-parameters
on an user's manual book.
As we'll be numbering the user's manual, remove the manual
numbering from SecurityBugs.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Diffstat (limited to 'Documentation/kernel-parameters.txt')
| -rw-r--r-- | Documentation/kernel-parameters.txt | 4577 |
1 files changed, 0 insertions, 4577 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt deleted file mode 100644 index b0804273b6e3..000000000000 --- a/Documentation/kernel-parameters.txt +++ /dev/null @@ -1,4577 +0,0 @@ -Kernel Parameters -~~~~~~~~~~~~~~~~~ - -The following is a consolidated list of the kernel parameters as -implemented by the __setup(), core_param() and module_param() macros -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. - -The kernel parses parameters from the kernel command line up to "--"; -if it doesn't recognize a parameter and it doesn't contain a '.', the -parameter gets passed to init: parameters with '=' go into init's -environment, others are passed as command line arguments to init. -Everything after "--" is passed as an argument to init. - -Module parameters can be specified in two ways: via the kernel command -line with a module name prefix, or via modprobe, e.g.:: - - (kernel command line) usbcore.blinkenlights=1 - (modprobe command line) modprobe usbcore blinkenlights=1 - -Parameters for modules which are built into the kernel need to be -specified on the kernel command line. modprobe looks through the -kernel command line (/proc/cmdline) and collects module parameters -when it loads a module, so the kernel command line can be used for -loadable modules too. - -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 - -Double-quotes can be used to protect spaces in values, e.g.:: - - param="spaces in here" - -cpu lists: ----------- - -Some kernel parameters take a list of CPUs as a value, e.g. isolcpus, -nohz_full, irqaffinity, rcu_nocbs. The format of this list is: - - <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> - -Note that for the special case of a range one can split the range into equal -sized groups and for each group use some amount from the beginning of that -group: - - <cpu number>-cpu number>:<used size>/<group size> - -For example one can add to the command line following parameter: - - isolcpus=1,2,10-20,100-2000:2/25 - -where the final item represents CPUs 100,101,125,126,150,151,... - - - -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. - CLK Common clock infrastructure is enabled. - CMA Contiguous Memory Area support 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) - X86_UV SGI UV support is enabled. - 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,ARM64] - Advanced Configuration and Power Interface - Format: { force | on | off | strict | noirq | rsdt | - copy_dsdt } - force -- enable ACPI if default was off - on -- enable ACPI but allow fallback to DT [arm64] - 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 - For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force" - are available - - See also Documentation/power/runtime_pm.txt, pci=noacpi - - 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_force_32bit_fadt_addr - force FADT to use 32 bit addresses rather than the - 64 bit X_* addresses. Some firmware have broken 64 - bit addresses for force ACPI ignore these and use - the older legacy 32 bit addresses. - - acpica_no_return_repair [HW, ACPI] - Disable AML predefined validation mechanism - This mechanism can repair the evaluation result to make - the return objects more ACPI specification compliant. - This option is useful for developers to identify the - root cause of an AML interpreter issue when the issue - has something to do with the repair mechanism. - - 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_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. - - acpi_force_table_verification [HW,ACPI] - Enable table checksum verification during early stage. - By default, this is disabled due to x86 early mapping - size limitation. - - 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_serialize [HW,ACPI] - Disable auto-serialization of AML methods - AML control methods that contain the opcodes to create - named objects will be marked as "Serialized" by the - auto-serialization feature. - This feature is enabled by default. - This option allows to turn off the feature. - - acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump - kernels. - - acpi_no_static_ssdt [HW,ACPI] - Disable installation of static SSDTs at early boot time - By default, SSDTs contained in the RSDT/XSDT will be - installed automatically and they will appear under - /sys/firmware/acpi/tables. - This option turns off this feature. - Note that specifying this option does not affect - dynamic table installation which will install SSDT - tables to /sys/firmware/acpi/tables/dynamic. - - 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_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS - Format: To spoof as Windows 98: ="Microsoft Windows" - - acpi_rev_override [ACPI] Override the _REV object to return 5 (instead - of 2 which is mandated by ACPI 6) as the supported ACPI - specification revision (when using this switch, it may - be necessary to carry out a cold reboot _twice_ in a - row to make it take effect on the platform firmware). - - acpi_osi= [HW,ACPI] Modify list of supported OS interface strings - acpi_osi="string1" # add string1 - acpi_osi="!string2" # remove string2 - acpi_osi=!* # remove all strings - acpi_osi=! # disable all built-in OS vendor - strings - acpi_osi=!! # enable all built-in OS vendor - strings - acpi_osi= # disable all strings - - 'acpi_osi=!' can be used in combination with single or - multiple 'acpi_osi="string1"' to support specific OS - vendor string(s). Note that such command can only - affect the default state of the OS vendor strings, thus - it cannot affect the default state of the feature group - strings and the current state of the OS vendor strings, - specifying it multiple times through kernel command line - is meaningless. This command is useful when one do not - care about the state of the feature group strings which - should be controlled by the OSPM. - Examples: - 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent - to 'acpi_osi="Windows 2000" acpi_osi=!', they all - can make '_OSI("Windows 2000")' TRUE. - - 'acpi_osi=' cannot be used in combination with other - 'acpi_osi=' command lines, the _OSI method will not - exist in the ACPI namespace. NOTE that such command can - only affect the _OSI support state, thus specifying it - multiple times through kernel command line is also - meaningless. - Examples: - 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)' - FALSE. - - 'acpi_osi=!*' can be used in combination with single or - multiple 'acpi_osi="string1"' to support specific - string(s). Note that such command can affect the - current state of both the OS vendor strings and the - feature group strings, thus specifying it multiple times - through kernel command line is meaningful. But it may - still not able to affect the final state of a string if - there are quirks related to this string. This command - is useful when one want to control the state of the - feature group strings to debug BIOS issues related to - the OSPM features. - Examples: - 1. 'acpi_osi="Module Device" acpi_osi=!*' can make - '_OSI("Module Device")' FALSE. - 2. 'acpi_osi=!* acpi_osi="Module Device"' can make - '_OSI("Module Device")' TRUE. - 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is - equivalent to - 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"' - and - 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!', - they all will make '_OSI("Windows 2000")' TRUE. - - 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_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 - - 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 - - alloc_snapshot [FTRACE] - Allocate the ftrace snapshot buffer on boot up when the - main buffer is allocated. This is handy if debugging - and you need to use tracing_snapshot() on boot up, and - do not want to use tracing_snapshot_alloc() as it needs - to be done where GFP_KERNEL allocations are allowed. - - 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. - - amd_iommu_intr= [HW,X86-64] - Specifies one of the following AMD IOMMU interrupt - remapping modes: - legacy - Use legacy interrupt remapping mode. - vapic - Use virtual APIC mode, which allows IOMMU - to inject interrupts directly into guest. - This mode requires kvm-amd.avic=1. - (Default when IOMMU HW support is present.) - - 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. - - apic_extnmi= [APIC,X86] External NMI delivery setting - Format: { bsp (default) | all | none } - bsp: External NMI is delivered only to CPU 0 - all: External NMIs are broadcast to all CPUs as a - backup of CPU 0 - none: External NMI is masked for all CPUs. This is - useful so that a dump capture kernel won't be - shot down by NMI - - 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 - - audit= [KNL] Enable the audit sub-system - Format: { "0" | "1" } (0 = disabled, 1 = enabled) - 0 - kernel audit is disabled and can not be enabled - until the next reboot - unset - kernel audit is initialized but disabled and - will be fully enabled by the userspace auditd. - 1 - kernel audit is initialized and partially enabled, - storing at most audit_backlog_limit messages in - RAM until it is fully enabled by the userspace - auditd. - Default: unset - - audit_backlog_limit= [KNL] Set the audit queue size limit. - Format: <int> (must be >=0) - Default: 64 - - bau= [X86_UV] Enable the BAU on SGI UV. The default - behavior is to disable the BAU (i.e. bau=0). - Format: { "0" | "1" } - 0 - Disable the BAU. - 1 - Enable the BAU. - unset - Disable the BAU. - - 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. - - blkdevparts= Manual partition parsing of block device(s) for - embedded devices based on command line input. - See Documentation/block/cmdline-partition.txt - - 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. - - bert_disable [ACPI] - Disable BERT OS support on buggy BIOSes. - - 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. - - ca_keys= [KEYS] This parameter identifies a specific key(s) on - the system trusted keyring to be used for certificate - trust validation. - format: { id:<keyid> | builtin } - - cca= [MIPS] Override the kernel pages' cache coherency - algorithm. Accepted values range from 0 to 7 - inclusive. See arch/mips/include/asm/pgtable-bits.h - for platform specific values (SB1, Loongson3 and - others). - - 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} - The effects of cgroup_disable=foo are: - - foo isn't auto-mounted if you mount all cgroups in - a single hierarchy - - foo isn't visible as an individually mountable - subsystem - {Currently only "memory" controller deal with this and - cut the overhead, others just disable the usage. So - only cgroup_disable=memory is actually worthy} - - cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1 - Format: { controller[,controller...] | "all" } - Like cgroup_disable, but only applies to cgroup v1; - the blacklisted controllers remain available in cgroup2. - - cgroup.memory= [KNL] Pass options to the cgroup memory controller. - Format: <string> - nosocket -- Disable socket memory accounting. - nokmem -- Disable kernel memory accounting. - - 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. - clk_ignore_unused - [CLK] - Prevents the clock framework from automatically gating - clocks that have not been explicitly enabled by a Linux - device driver but are enabled in hardware at reset or - by the bootloader/firmware. Note that this does not - force such clocks to be always-on nor does it reserve - those clocks in any way. This parameter is useful for - debug and development, but should not be needed on a - platform with proper driver support. For more - information, see Documentation/clk.txt. - - 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 - - clocksource.arm_arch_timer.evtstrm= - [ARM,ARM64] - Format: <bool> - Enable/disable the eventstream feature of the ARM - architected timer so that code using WFE-based polling - loops can be debugged more effectively on production - systems. - - clocksource.arm_arch_timer.fsl-a008585= - [ARM64] - Format: <bool> - Enable/disable the workaround of Freescale/NXP - erratum A-008585. This can be useful for KVM - guests, if the guest device tree doesn't show the - erratum. If unspecified, the workaround is - enabled based on the device tree. - - clearcpuid=BITNUM [X86] - Disable CPUID feature X for the kernel. See - arch/x86/include/asm/cpufeatures.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]@[start[MG][-end[MG]]] - [ARM,X86,KNL] - Sets the size of kernel global memory area for - contiguous memory allocations and optionally the - placement constraint by the physical address range of - memory allocations. A value of 0 disables CMA - altogether. 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] - uart[8250],mmio16,<addr>[,options] - uart[8250],mmio32,<addr>[,options] - uart[8250],0x<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. - MMIO inter-register address stride is either 8-bit - (mmio), 16-bit (mmio16), or 32-bit (mmio32). - If none of [io|mmio|mmio16|mmio32], <addr> is assumed - to be equivalent to 'mmio'. 'options' are specified in - the same format described for ttyS above; if unspecified, - the h/w is not re-initialized. - - 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 - - cpu_init_udelay=N - [X86] Delay for N microsec between assert and de-assert - of APIC INIT to start processors. This delay occurs - on every CPU online, such as boot, and resume from suspend. - Default: 10000 - - 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=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. - - crashkernel=size[KMG],high - [KNL, x86_64] range could be above 4G. Allow kernel - to allocate physical memory region from top, so could - be above 4G if system have more than 4G ram installed. - Otherwise memory region will be allocated below 4G, if - available. - It will be ignored if crashkernel=X is specified. - crashkernel=size[KMG],low - [KNL, x86_64] range under 4G. When crashkernel=X,high - is passed, kernel could allocate physical memory region - above 4G, that cause second kernel crash on system - that require some amount of low memory, e.g. swiotlb - requires at least 64M+32K low memory, also enough extra - low memory is needed to make sure DMA buffers for 32-bit - devices won't run out. Kernel would try to allocate at - at least 256M below 4G automatically. - This one let user to specify own low range under 4G - for second kernel instead. - 0: to disable low allocation. - It will be ignored when crashkernel=X,high is not used - or memory reserved is below 4G. - - cryptomgr.notests - [KNL] Disable crypto self-tests - - 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. - - debug_pagealloc= - [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this - parameter enables the feature at boot time. In - default, it is disabled. We can avoid allocating huge - chunk of memory for debug pagealloc if we don't enable - it at boot time and the system will work mostly same - with the kernel built without CONFIG_DEBUG_PAGEALLOC. - on: enable the feature - - 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. - - disable_1tb_segments [PPC] - Disables the use of 1TB hash page table segments. This - causes the kernel to fall back to 256MB segments which - can be useful when debugging issues that require an SLB - miss to occur. - - disable= [IPV6] - See Documentation/networking/ipv6.txt. - - disable_radix [PPC] - Disable RADIX MMU mode on POWER9 - - disable_cpu_apicid= [X86,APIC,SMP] - Format: <int> - The number of initial APIC ID for the - corresponding CPU to be disabled at boot, - mostly used for the kdump 2nd kernel to - disable BSP to wake up multiple CPUs without - causing system reset or hang due to sending - INIT from AP to BSP. - - 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. - - dis_ucode_ldr [X86] Disable the microcode loader. - - 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>[,[<connector>:]<file>] - Broken monitors, graphic adapters, KVMs and EDIDless - panels may send no or incorrect EDID data sets. - This parameter allows to specify an EDID data sets - in the /lib/firmware directory that are 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. Each connector may use a unique EDID data - set by separating the files with a comma. An EDID - data set with no connector name will be used for - any connectors not explicitly specified. - - 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. - - nompx [X86] Disables Intel Memory Protection Extensions. - See Documentation/x86/intel_mpx.txt for more - information about the feature. - - nopku [X86] Disable Memory Protection Keys CPU feature found - in some Intel CPUs. - - eagerfpu= [X86] - on enable eager fpu restore - off disable eager fpu restore - auto selects the default scheme, which automatically - enables eagerfpu restore for xsaveopt. - - module.async_probe [KNL] - Enable asynchronous probe on this module. - - early_ioremap_debug [KNL] - Enable debug messages in early_ioremap support. This - is useful for tracking down temporary early mappings - which are not unmapped. - - earlycon= [KNL] Output early console device and options. - - When used with no options, the early console is - determined by the stdout-path property in device - tree's chosen node. - - cdns,<addr>[,options] - Start an early, polled-mode console on a Cadence - (xuartps) serial port at the specified address. Only - supported option is baud rate. If baud rate is not - specified, the serial port must already be setup and - configured. - - uart[8250],io,<addr>[,options] - uart[8250],mmio,<addr>[,options] - uart[8250],mmio32,<addr>[,options] - uart[8250],mmio32be,<addr>[,options] - uart[8250],0x<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 or mmio32be). - If none of [io|mmio|mmio32|mmio32be], <addr> is assumed - to be equivalent to 'mmio'. 'options' are specified - in the same format described for "console=ttyS<n>"; if - unspecified, the h/w is not initialized. - - pl011,<addr> - pl011,mmio32,<addr> - Start an early, polled-mode console on a pl011 serial - port at the specified address. The pl011 serial port - must already be setup and configured. Options are not - yet supported. If 'mmio32' is specified, then only - the driver will use only 32-bit accessors to read/write - the device registers. - - meson,<addr> - Start an early, polled-mode console on a meson serial - port at the specified address. The serial port must - already be setup and configured. Options are not yet - supported. - - msm_serial,<addr> - Start an early, polled-mode console on an msm serial - port at the specified address. The serial port - must already be setup and configured. Options are not - yet supported. - - msm_serial_dm,<addr> - Start an early, polled-mode console on an msm serial - dm port at the specified address. The serial port - must already be setup and configured. Options are not - yet supported. - - smh Use ARM semihosting calls for early console. - - s3c2410,<addr> - s3c2412,<addr> - s3c2440,<addr> - s3c6400,<addr> - s5pv210,<addr> - exynos4210,<addr> - Use early console provided by serial driver available - on Samsung SoCs, requires selecting proper type and - a correct base address of the selected UART port. The - serial port must already be setup and configured. - Options are not yet supported. - - lpuart,<addr> - lpuart32,<addr> - Use early console provided by Freescale LP UART driver - found on Freescale Vybrid and QorIQ LS1021A processors. - A valid base address must be provided, and the serial - port must already be setup and configured. - - armada3700_uart,<addr> - Start an early, polled-mode console on the - Armada 3700 serial port at the specified - address. The serial port must already be setup - and configured. Options are not yet supported. - - earlyprintk= [X86,SH,BLACKFIN,ARM,M68k] - earlyprintk=vga - earlyprintk=efi - earlyprintk=xen - earlyprintk=serial[,ttySn[,baudrate]] - earlyprintk=serial[,0x...[,baudrate]] - earlyprintk=ttySn[,baudrate] - earlyprintk=dbgp[debugController#] - earlyprintk=pciserial,bus:device.function[,baudrate] - - earlyprintk is useful when the kernel crashes before - the normal console is initialized. It is not enabled by - default because it has some cosmetic problems. - - Append ",keep" to not disable it when the real console - takes over. - - Only one of vga, efi, serial, or usb debug port can - be used at a time. - - Currently only ttyS0 and ttyS1 may be specified by - name. Other I/O ports may be explicitly specified - on some architectures (x86 and arm at least) by - replacing ttySn with an I/O port address, like this: - earlyprintk=serial,0x1008,115200 - You can find the port for a given device in - /proc/tty/driver/serial: - 2: uart:ST16650V2 port:00001008 irq:18 ... - - Interaction with the standard serial driver is not - very good. - - The VGA and EFI output is eventually overwritten by - the real console. - - The xen output can only be used by Xen PV guests. - - edac_report= [HW,EDAC] Control how to report EDAC event - Format: {"on" | "off" | "force"} - on: enable EDAC to report H/W event. May be overridden - by other higher priority error reporting module. - off: disable H/W event reporting through EDAC. - force: enforce the use of EDAC to report H/W event. - default: on. - - 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]"} - - efi= [EFI] - Format: { "old_map", "nochunk", "noruntime", "debug" } - old_map [X86-64]: switch to the old ioremap-based EFI - runtime services mapping. 32-bit still uses this one by - default. - nochunk: disable reading files in "chunks" in the EFI - boot stub, as chunking can cause problems with some - firmware implementations. - noruntime : disable EFI runtime services support - debug: enable misc debug output - - efi_no_storage_paranoia [EFI; X86] - Using this parameter you can use more than 50% of - your efi variable storage. Use this parameter only if - you are really sure that your UEFI does sane gc and - fulfills the spec otherwise your board may brick. - - efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86] - Add arbitrary attribute to specific memory range by - updating original EFI memory map. - Region of memory which aa attribute is added to is - from ss to ss+nn. - If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000 - is specified, EFI_MEMORY_MORE_RELIABLE(0x10000) - attribute is added to range 0x100000000-0x180000000 and - 0x10a0000000-0x1120000000. - - Using this parameter you can do debugging of EFI memmap - related feature. For example, you can do debugging of - Address Range Mirroring feature even if your box - doesn't support it. - - efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT - that is to be dynamically loaded by Linux. If there are - multiple variables with the same name but with different - vendor GUIDs, all of them will be loaded. See - Documentation/acpi/ssdt-overlays.txt for details. - - - 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. - - forcepae [X86-32] - Forcefully enable Physical Address Extension (PAE). - Many Pentium M systems disable PAE but may have a - functionally usable PAE implementation. - Warning: use of this parameter will taint the kernel - and may cause unknown problems. - - 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. - - ftrace_graph_notrace=[function-list] - [FTRACE] Do not trace from the functions specified in - function-list. This list is a comma separated list of - functions that can be changed at run time by the - set_graph_notrace 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. If the - primary GPT is corrupted, it enables the backup/alternate - GPT to be used instead. - - 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 - - gpio-mockup.gpio_mockup_ranges - [HW] Sets the ranges of gpiochip of for this device. - Format: <start1>,<end1>,<start2>,<end2>... - - hardlockup_all_cpu_backtrace= - [KNL] Should the hard-lockup detector generate - backtraces on all cpus. - Format: <integer> - - 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 - - hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET - registers. Default set by CONFIG_HPET_MMAP_DEFAULT. - - 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). - - 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.unmask_kbd_data - [HW] Enable printing of interrupt data from the KBD port - (disabled by default, and as a pre-condition - requires that i8042.debug=1 be enabled) - 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, cleanup and - suspend-to-ram transitions, only during s2r - transitions, or never reset - Format: { 1 | Y | y | 0 | N | n } - 1, Y, y: always reset controller - 0, N, n: don't ever reset controller - Default: only on s2r transitions on x86; most other - architectures force reset to be always executed - i8042.unlock [HW] Unlock (ignore) the keylock - i8042.kbdreset [HW] Reset device connected to KBD port - - 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-generic.probe-mask= [HW] (E)IDE subsystem - Format: <int> - Probe mask for legacy ISA IDE ports. Depending on - platform up to 6 ports are supported, enabled by - setting corresponding bits in the mask to 1. The - default value is 0x0, which has a special meaning. - On systems that have PCI, it triggers scanning the - PCI bus for the first and the second port, which - are then probed. On systems without PCI the value - of 0x0 enables probing the two first ports as if it - was 0x3. - - 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 - - ieee754= [MIPS] Select IEEE Std 754 conformance mode - Format: { strict | legacy | 2008 | relaxed } - Default: strict - - Choose which programs will be accepted for execution - based on the IEEE 754 NaN encoding(s) supported by - the FPU and the NaN encoding requested with the value - of an ELF file header flag individually set by each - binary. Hardware implementations are permitted to - support either or both of the legacy and the 2008 NaN - encoding mode. - - Available settings are as follows: - strict accept binaries that request a NaN encoding - supported by the FPU - legacy only accept legacy-NaN binaries, if supported - by the FPU - 2008 only accept 2008-NaN binaries, if supported - by the FPU - relaxed accept any binaries regardless of whether - supported by the FPU - - The FPU emulator is always able to support both NaN - encodings, so if no FPU hardware is present or it has - been disabled with 'nofpu', then the settings of - 'legacy' and '2008' strap the emulator accordingly, - 'relaxed' straps the emulator for both legacy-NaN and - 2008-NaN, whereas 'strict' enables legacy-NaN only on - legacy processors and both NaN encodings on MIPS32 or - MIPS64 CPUs. - - The setting for ABS.fmt/NEG.fmt instruction execution - mode generally follows that for the NaN encoding, - except where unsupported by hardware. - - 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. - - ignore_rlimit_data - Ignore RLIMIT_DATA setting for data mappings, - print warning at first misuse. Can be changed via - /sys/module/kernel/parameters/ignore_rlimit_data. - - ihash_entries= [KNL] - Set number of hash buckets for inode cache. - - ima_appraise= [IMA] appraise integrity measurements - Format: { "off" | "enforce" | "fix" | "log" } - default: "enforce" - - ima_appraise_tcb [IMA] - The builtin appraise policy appraises all files - owned by uid=0. - - ima_hash= [IMA] - Format: { md5 | sha1 | rmd160 | sha256 | sha384 - | sha512 | ... } - default: "sha1" - - The list of supported hash algorithms is defined - in crypto/hash_info.h. - - ima_policy= [IMA] - The builtin measurement policy to load during IMA - setup. Specyfing "tcb" as the value, measures all - programs exec'd, files mmap'd for exec, and all files - opened with the read mode bit set by either the - effective uid (euid=0) or uid=0. - Format: "tcb" - - ima_tcb [IMA] Deprecated. Use ima_policy= instead. - 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. - - ima_template= [IMA] - Select one of defined IMA measurements template formats. - Formats: { "ima" | "ima-ng" | "ima-sig" } - Default: "ima-ng" - - ima_template_fmt= - [IMA] Define a custom template format. - Format: { "field1|...|fieldN" } - - ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage - Format: <min_file_size> - Set the minimal file size for using asynchronous hash. - If left unspecified, ahash usage is disabled. - - ahash performance varies for different data sizes on - different crypto accelerators. This option can be used - to achieve the best performance for a particular HW. - - ima.ahash_bufsize= [IMA] Asynchronous hash buffer size - Format: <bufsize> - Set hashing buffer size. Default: 4k. - - ahash performance varies for different chunk sizes on - different crypto accelerators. This option can be used - to achieve best performance for particular HW. - - 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. - - initcall_blacklist= [KNL] Do not execute a comma-separated list of - initcall functions. Useful for debugging built-in - modules and initcalls. - - initrd= [BOOT] Specify the location of the initial ramdisk - - init_pkru= [x86] Specify the default memory protection keys rights - register contents for all processes. 0x55555554 by - default (disallow access to all but pkey 0). Can - override in debugfs after boot. - - inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver - Format: <irq> - - int_pln_enable [x86] Enable power limit notification interrupt - - integrity_audit=[IMA] - Format: { "0" | "1" } - 0 -- basic integrity auditing messages. (Default) - 1 -- additional integrity auditing messages. - - 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. - ecs_off [Default Off] - By default, extended context tables will be supported if - the hardware advertises that it has support both for the - extended tables themselves, and also PASID support. With - this option set, extended tables will not be used even - on hardware which claims to support them. - - intel_idle.max_cstate= [KNL,HW,ACPI,X86] - 0 disables intel_idle and fall back on acpi_idle. - 1 to 9 specify maximum depth of C-state. - - intel_pstate= [X86] - disable - Do not enable intel_pstate as the default - scaling driver for the supported processors - force - Enable intel_pstate on systems that prohibit it by default - in favor of acpi-cpufreq. Forcing the intel_pstate driver - instead of acpi-cpufreq may disable platform features, such - as thermal controls and power capping, that rely on ACPI - P-States information being indicated to OSPM and therefore - should be used with caution. This option does not work with - processors that aren't supported by the intel_pstate driver - or on platforms that use pcc-cpufreq instead of acpi-cpufreq. - no_hwp - Do not enable hardware P state control (HWP) - if available. - hwp_only - Only load intel_pstate on systems which support - hardware P state control (HWP) if available. - support_acpi_ppc - Enforce ACPI _PPC performance limits. If the Fixed ACPI - Description Table, specifies preferred power management - profile as "Enterprise Server" or "Performance Server", - then this feature is turned on by default. - - 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 - nopost disable Interrupt Posting - - 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] - nobypass [PPC/POWERNV] - Disable IOMMU bypass, using IOMMU for PCI devices. - - - 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. - - irqaffinity= [SMP] Set the default irq affinity mask - The argument is a cpu list, as described above. - - 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. - The argument is a cpu list, as described above. - - 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] - - ivrs_ioapic [HW,X86_64] - Provide an override to the IOAPIC-ID<->DEVICE-ID - mapping provided in the IVRS ACPI table. For - example, to map IOAPIC-ID decimal 10 to - PCI device 00:14.0 write the parameter as: - ivrs_ioapic[10]=00:14.0 - - ivrs_hpet [HW,X86_64] - Provide an override to the HPET-ID<->DEVICE-ID - mapping provided in the IVRS ACPI table. For - example, to map HPET-ID decimal 0 to - PCI device 00:14.0 write the parameter as: - ivrs_hpet[0]=00:14.0 - - ivrs_acpihid [HW,X86_64] - Provide an override to the ACPI-HID:UID<->DEVICE-ID - mapping provided in the IVRS ACPI table. For - example, to map UART-HID:UID AMD0020:0 to - PCI device 00:14.5 write the parameter as: - ivrs_acpihid[00:14.5]=AMD0020:0 - - js= [HW,JOY] Analog joystick - See Documentation/input/joystick.txt. - - nokaslr [KNL] - When CONFIG_RANDOMIZE_BASE is set, this disables - kernel and module base offset ASLR (Address Space - Layout Randomization). - - keepinitrd [HW,ARM] - - kernelcore= [KNL,X86,IA-64,PPC] - Format: nn[KMGTPE] | "mirror" - 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 Movable 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. - - Instead of specifying the amount of memory (nn[KMGTPE]), - you can specify "mirror" option. In case "mirror" - option is specified, mirrored (reliable) memory is used - for non-movable allocations and remaining memory is used - for Movable pages. nn[KMGTPE] and "mirror" are exclusive, - so you can NOT specify nn[KMGTPE] and "mirror" at the same - time. - - 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 - Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y, - the default is off. - - kmemcheck= [X86] Boot-time kmemcheck enable/disable/one-shot mode - Valid arguments: 0, 1, 2 - kmemcheck=0 (disabled) - kmemcheck=1 (enabled) - kmemcheck=2 (one-shot mode) - Default: 2 (one-shot mode) - - 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. - - * [no]ncqtrim: Turn off queued DSM TRIM. - - * nohrst, nosrst, norst: suppress hard, soft - and both resets. - - * rstonce: only attempt one reset during - hot-unplug link recovery - - * dump_id: dump IDENTIFY data. - - * atapi_dmadir: Enable ATAPI DMADIR bridge support - - * disable: Disable this device. - - 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> - - locktorture.nreaders_stress= [KNL] - Set the number of locking read-acquisition kthreads. - Defaults to being automatically set based on the - number of online CPUs. - - locktorture.nwriters_stress= [KNL] - Set the number of locking write-acquisition kthreads. - - locktorture.onoff_holdoff= [KNL] - Set time (s) after boot for CPU-hotplug testing. - - locktorture.onoff_interval= [KNL] - Set time (s) between CPU-hotplug operations, or - zero to disable CPU-hotplug testing. - - locktorture.shuffle_interval= [KNL] - Set task-shuffle interval (jiffies). Shuffling - tasks allows some CPUs to go into dyntick-idle - mode during the locktorture test. - - locktorture.shutdown_secs= [KNL] - Set time (s) after boot system shutdown. This - is useful for hands-off automated testing. - - locktorture.stat_interval= [KNL] - Time (s) between statistics printk()s. - - locktorture.stutter= [KNL] - 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 the locking primitive's ability to - transition abruptly to and from idle. - - locktorture.torture_runnable= [BOOT] - Start locktorture running at boot time. - - locktorture.torture_type= [KNL] - Specify the locking implementation to test. - - locktorture.verbose= [KNL] - Enable additional printk() statements. - - 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 and greater - than the minimal size. The minimal size is defined - by LOG_BUF_SHIFT kernel config parameter. There is - also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter - that allows to increase the default size depending on - the number of CPUs. See init/Kconfig for more details. - - 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> - - 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 - will bring up during bootup. maxcpus=n : n >= 0 limits - the kernel to bring up 'n' processors. Surely after - bootup you can bring up the other plugged cpu by executing - "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus - only takes effect during system bootup. - While 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. - - memhp_default_state=online/offline - [KNL] Set the initial state for the memory hotplug - onlining policy. If not specified, the default value is - set according to the - CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config - option. - See Documentation/memory-hotplug.txt. - - 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 is from ss to ss+nn. - - memmap=nn[KMG]#ss[KMG] - [KNL,ACPI] Mark specific memory as ACPI data. - Region of memory to be marked is from ss to ss+nn. - - memmap=nn[KMG]$ss[KMG] - [KNL,ACPI] Mark specific memory as reserved. - Region of memory to be reserved is from ss to ss+nn. - Example: Exclude memory from 0x18690000-0x1869ffff - memmap=64K$0x18690000 - or - memmap=0x10000$0x18690000 - - memmap=nn[KMG]!ss[KMG] - [KNL,X86] Mark specific memory as protected. - Region of memory to be used, from ss to ss+nn. - The memory region may be marked as e820 type 12 (0xc) - and is NVDIMM or ADR memory. - - 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,ARM] 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_FORCE is set, that - is always true, so this option does nothing. - - module_blacklist= [KNL] Do not load a comma-separated list of - modules. Useful for debugging problem modules. - - 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. - - movable_node [KNL,X86] Boot-time switch to enable the effects - of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details. - - 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_nr_threads= - [NFSv4] set the total number of threads that the - NFS client will assign to service NFSv4 callback - requests. - - 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_cb_slots= - [NFSv4.1] Sets the maximum number of session - slots the client will assign to the callback - channel. This determines the maximum number of - callbacks the client will process in parallel for - a particular server. - - 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. - - nfs.recover_lost_locks = - [NFSv4] Attempt to recover locks that were lost due - to a lease timeout on the server. Please note that - doing this risks data corruption, since there are - no guarantees that the file will remain unchanged - after the locks are lost. - If you want to enable the kernel legacy behaviour of - attempting to recover these locks, then set this - parameter to '1'. - The default parameter value of '0' causes the kernel - not to attempt recovery of lost locks. - - nfs4.layoutstats_timer = - [NFSv4.2] Change the rate at which the kernel sends - layoutstats to the pNFS metadata server. - - Setting this to value to 0 causes the kernel to use - whatever value is the default set by the layout - driver. A non-zero value sets the minimum interval - in seconds between layoutstats transmissions. - - 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 or 1 - 0 - turn hardlockup detector in nmi_watchdog off - 1 - turn hardlockup detector in nmi_watchdog on - When panic is specified, panic when an NMI watchdog - timeout occurs (or 'nopanic' to override the opposite - default). To disable both hard and soft lockup detectors, - please see 'nowatchdog'. - 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 - - nodsp [SH] Disable hardware DSP at boot time. - - noefi 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 [MIPS,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. - - nohugeiomap [KNL,x86] Disable kernel huge I/O mappings. - - nosmt [KNL,S390] Disable symmetric multithreading (SMT). - Equivalent to smt=1. - - 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. - - noxsaveopt [X86] Disables xsaveopt used in saving x86 extended - register states. The kernel will fall back to use - xsave to save the states. By using this parameter, - performance of saving the states is degraded because - xsave doesn't support modified optimization while - xsaveopt supports it on xsaveopt enabled systems. - - noxsaves [X86] Disables xsaves and xrstors used in saving and - restoring x86 extended register state in compacted - form of xsave area. The kernel will fall back to use - xsaveopt and xrstor to save and restore the states - in standard form of xsave area. By using this - parameter, xsave area per process might occupy more - memory on xsaves enabled systems. - - 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. - - nohibernate [HIBERNATION] Disable hibernation and resume. - - nohz= [KNL] Boottime enable/disable dynamic ticks - Valid arguments: on, off - Default: on - - nohz_full= [KNL,BOOT] - The argument is a cpu list, as described above. - In kernels built with CONFIG_NO_HZ_FULL=y, set - the specified list of CPUs whose tick will be stopped - whenever possible. The boot CPU will be forced outside - the range to maintain the timekeeping. - The CPUs in this range must also be included in the - rcu_nocbs= set. - - 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] - - noinvpcid [X86] Disable the INVPCID cpu feature. - - 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 and PPC8xx - - nomca [IA-64] Disable machine check abort handling - - nomce [X86-32] Disable 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 - - nordrand [X86] Disable kernel use of the RDRAND and - RDSEED instructions even if they are supported - by the processor. RDRAND and RDSEED are 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 - - nowatchdog [KNL] Disable both lockup detectors, i.e. - soft-lockup and NMI watchdog (hard-lockup). - - 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 - support 'n' processors. It could be larger than the - number of already plugged CPU during bootup, later in - runtime you can physically add extra cpu until it reaches - n. So during boot up some boot time memory for per-cpu - variables need be pre-allocated for later physical cpu - hot plugging. - - 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) - - 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 - - page_owner= [KNL] Boot-time page_owner enabling option. - Storage of the information about who allocated - each page is disabled in default. With this switch, - we can turn it on. - on: enable the feature - - page_poison= [KNL] Boot-time parameter changing the state of - poisoning on the buddy allocator. - off: turn off poisoning - on: turn on poisoning - - panic= [KNL] Kernel behaviour on panic: delay <timeout> - timeout > 0: seconds before rebooting - timeout = 0: wait forever - timeout < 0: reboot immediately - Format: <timeout> - - panic_on_warn panic() instead of WARN(). Useful to cause kdump - on a WARN(). - - crash_kexec_post_notifiers - Run kdump after running panic-notifiers and dumping - kmsg. This only for the users who doubt kdump always - succeeds in any situation. - Note that this also increases risks of kdump failure, - because some panic notifiers can make the crashed - kernel more unstable. - - 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 Access - Mechanism 1 (config address in IO port 0xCF8, - data in IO port 0xCFC, both 32-bit). - conf2 [X86] Force use of PCI Configuration Access - Mechanism 2 (IO port 0xCF8 is an 8-bit port for - the function, IO port 0xCFA, also 8-bit, sets - bus number. The config space is then accessed - through ports 0xC000-0xCFFF). - See http://wiki.osdev.org/PCI for more info - on the configuration access mechanisms. - 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 - 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>[; ...] - [<order of align>@]pci:<vendor>:<device>\ - [:<subvendor>:<subdevice>][; ...] - 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. - To specify the alignment for several - instances of a device, the PCI vendor, - device, subvendor, and subdevice may be - specified, e.g., 4096@pci:8086:9c22:103c:198f - 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. - hpbussize=nn The minimum amount of additional bus numbers - reserved for buses below a hotplug bridge. - Default is 1. - 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_port_pm= [PCIE] PCIe port power management handling: - off Disable power management of all PCIe ports - force Forcibly enable power management of all PCIe ports - - 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_ignore_unused - [PM] - Keep all power-domains already enabled by bootloader on, - even if no driver has claimed them. This is useful - for debug and development, but should not be - needed on a platform with proper driver support. - - 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>.... - - ppc_strict_facility_enable - [PPC] This option catches any kernel floating point, - Altivec, VSX and SPE outside of regions specifically - allowed (eg kernel_enable_fpu()/kernel_disable_fpu()). - There is some performance impact when enabling this. - - 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.devkmsg={on,off,ratelimit} - Control writing to /dev/kmsg. - on - unlimited logging to /dev/kmsg from userspace - off - logging to /dev/kmsg disabled - ratelimit - ratelimit the logging - Default: ratelimit - - 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_size= [RAM] Sizes of RAM disks in kilobytes - See Documentation/blockdev/ramdisk.txt. - - rcu_nocbs= [KNL] - The argument is a cpu list, as described above. - - 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 "rcuox/N" kthreads created for - that purpose, where "x" is "b" for RCU-bh, "p" - for RCU-preempt, and "s" for RCU-sched, and "N" - is the CPU number. 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] - 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] - Set maximum number of finished RCU callbacks to - process in one batch. - - rcutree.dump_tree= [KNL] - Dump the structure of the rcu_node combining tree - out at early boot. This is used for diagnostic - purposes, to verify correct tree setup. - - rcutree.gp_cleanup_delay= [KNL] - Set the number of jiffies to delay each step of - RCU grace-period cleanup. This only has effect - when CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP is set. - - rcutree.gp_init_delay= [KNL] - Set the number of jiffies to delay each step of - RCU grace-period initialization. This only has - effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT - is set. - - rcutree.gp_preinit_delay= [KNL] - Set the number of jiffies to delay each step of - RCU grace-period pre-initialization, that is, - the propagation of recent CPU-hotplug changes up - the rcu_node combining tree. This only has effect - when CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT is set. - - rcutree.rcu_fanout_exact= [KNL] - Disable autobalancing of the rcu_node combining - tree. This is used by rcutorture, and might - possibly be useful for architectures having high - cache-to-cache transfer latencies. - - rcutree.rcu_fanout_leaf= [KNL] - Change the number of CPUs assigned to each - leaf rcu_node structure. Useful for very - large systems, which will choose the value 64, - and for NUMA systems with large remote-access - latencies, which will choose a value aligned - with the appropriate hardware boundaries. - - rcutree.jiffies_till_sched_qs= [KNL] - Set required age in jiffies for a - given grace period before RCU starts - soliciting quiescent-state help from - rcu_note_context_switch(). - - rcutree.jiffies_till_first_fqs= [KNL] - 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] - Set delay between subsequent attempts to force - quiescent states. Units are jiffies, minimum - value is one, and maximum value is HZ. - - rcutree.kthread_prio= [KNL,BOOT] - Set the SCHED_FIFO priority of the RCU per-CPU - kthreads (rcuc/N). This value is also used for - the priority of the RCU boost threads (rcub/N) - and for the RCU grace-period kthreads (rcu_bh, - rcu_preempt, and rcu_sched). If RCU_BOOST is - set, valid values are 1-99 and the default is 1 - (the least-favored priority). Otherwise, when - RCU_BOOST is not set, valid values are 0-99 and - the default is zero (non-realtime operation). - - rcutree.rcu_nocb_leader_stride= [KNL] - Set the number of NOCB kthread groups, which - defaults to the square root of the number of - CPUs. Larger numbers reduces the wakeup overhead - on the per-CPU grace-period kthreads, but increases - that same overhead on each group's leader. - - rcutree.qhimark= [KNL] - Set threshold of queued RCU callbacks beyond which - batch limiting is disabled. - - rcutree.qlowmark= [KNL] - Set threshold of queued RCU callbacks below which - batch limiting is re-enabled. - - rcutree.rcu_idle_gp_delay= [KNL] - Set wakeup interval for idle CPUs that have - RCU callbacks (RCU_FAST_NO_HZ=y). - - rcutree.rcu_idle_lazy_gp_delay= [KNL] - Set wakeup interval for idle CPUs that have - only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y). - Lazy RCU callbacks are those which RCU can - prove do nothing more than free memory. - - rcuperf.gp_exp= [KNL] - Measure performance of expedited synchronous - grace-period primitives. - - rcuperf.holdoff= [KNL] - Set test-start holdoff period. The purpose of - this parameter is to delay the start of the - test until boot completes in order to avoid - interference. - - rcuperf.nreaders= [KNL] - Set number of RCU readers. The value -1 selects - N, where N is the number of CPUs. A value - "n" less than -1 selects N-n+1, where N is again - the number of CPUs. For example, -2 selects N - (the number of CPUs), -3 selects N+1, and so on. - A value of "n" less than or equal to -N selects - a single reader. - - rcuperf.nwriters= [KNL] - Set number of RCU writers. The values operate - the same as for rcuperf.nreaders. - N, where N is the number of CPUs - - rcuperf.perf_runnable= [BOOT] - Start rcuperf running at boot time. - - rcuperf.shutdown= [KNL] - Shut the system down after performance tests - complete. This is useful for hands-off automated - testing. - - rcuperf.perf_type= [KNL] - Specify the RCU implementation to test. - - rcuperf.verbose= [KNL] - Enable additional printk() statements. - - rcutorture.cbflood_inter_holdoff= [KNL] - Set holdoff time (jiffies) between successive - callback-flood tests. - - rcutorture.cbflood_intra_holdoff= [KNL] - Set holdoff time (jiffies) between successive - bursts of callbacks within a given callback-flood - test. - - rcutorture.cbflood_n_burst= [KNL] - Set the number of bursts making up a given - callback-flood test. Set this to zero to - disable callback-flood testing. - - rcutorture.cbflood_n_per_burst= [KNL] - Set the number of callbacks to be registered - in a given burst of a callback-flood test. - - rcutorture.fqs_duration= [KNL] - Set duration of force_quiescent_state bursts - in microseconds. - - rcutorture.fqs_holdoff= [KNL] - Set holdoff time within force_quiescent_state bursts - in microseconds. - - rcutorture.fqs_stutter= [KNL] - Set wait time between force_quiescent_state bursts - in seconds. - - rcutorture.gp_cond= [KNL] - Use conditional/asynchronous update-side - primitives, if available. - - rcutorture.gp_exp= [KNL] - Use expedited update-side primitives, if available. - - rcutorture.gp_normal= [KNL] - Use normal (non-expedited) asynchronous - update-side primitives, if available. - - rcutorture.gp_sync= [KNL] - Use normal (non-expedited) synchronous - update-side primitives, if available. If all - of rcutorture.gp_cond=, rcutorture.gp_exp=, - rcutorture.gp_normal=, and rcutorture.gp_sync= - are zero, rcutorture acts as if is interpreted - they are all non-zero. - - rcutorture.n_barrier_cbs= [KNL] - Set callbacks/threads for rcu_barrier() testing. - - rcutorture.nfakewriters= [KNL] - Set number of concurrent RCU writers. These just - stress RCU, they don't participate in the actual - test, hence the "fake". - - rcutorture.nreaders= [KNL] - Set number of RCU readers. The value -1 selects - N-1, where N is the number of CPUs. A value - "n" less than -1 selects N-n-2, where N is again - the number of CPUs. For example, -2 selects N - (the number of CPUs), -3 selects N+1, and so on. - - rcutorture.object_debug= [KNL] - Enable debug-object double-call_rcu() testing. - - rcutorture.onoff_holdoff= [KNL] - Set time (s) after boot for CPU-hotplug testing. - - rcutorture.onoff_interval= [KNL] - Set time (s) between CPU-hotplug operations, or - zero to disable CPU-hotplug testing. - - rcutorture.shuffle_interval= [KNL] - Set task-shuffle interval (s). Shuffling tasks - allows some CPUs to go into dyntick-idle mode - during the rcutorture test. - - rcutorture.shutdown_secs= [KNL] - Set time (s) after boot system shutdown. This - is useful for hands-off automated testing. - - rcutorture.stall_cpu= [KNL] - Duration of CPU stall (s) to test RCU CPU stall - warnings, zero to disable. - - rcutorture.stall_cpu_holdoff= [KNL] - Time to wait (s) after boot before inducing stall. - - rcutorture.stat_interval= [KNL] - Time (s) between statistics printk()s. - - rcutorture.stutter= [KNL] - 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] - 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] - Duration (s) of each individual boost test. - - rcutorture.test_boost_interval= [KNL] - Interval (s) between each boost test. - - rcutorture.test_no_idle_hz= [KNL] - Test RCU's dyntick-idle handling. See also the - rcutorture.shuffle_interval parameter. - - rcutorture.torture_runnable= [BOOT] - Start rcutorture running at boot time. - - rcutorture.torture_type= [KNL] - Specify the RCU implementation to test. - - rcutorture.verbose= [KNL] - Enable additional printk() statements. - - rcupdate.rcu_cpu_stall_suppress= [KNL] - Suppress RCU CPU stall warning messages. - - rcupdate.rcu_cpu_stall_timeout= [KNL] - Set timeout for RCU CPU stall warning messages. - - rcupdate.rcu_expedited= [KNL] - Use expedited grace-period primitives, for - example, synchronize_rcu_expedited() instead - of synchronize_rcu(). This reduces latency, - but can increase CPU utilization, degrade - real-time latency, and degrade energy efficiency. - No effect on CONFIG_TINY_RCU kernels. - - rcupdate.rcu_normal= [KNL] - Use only normal grace-period primitives, - for example, synchronize_rcu() instead of - synchronize_rcu_expedited(). This improves - real-time latency, CPU utilization, and - energy efficiency, but can expose users to - increased grace-period latency. This parameter - overrides rcupdate.rcu_expedited. No effect on - CONFIG_TINY_RCU kernels. - - rcupdate.rcu_normal_after_boot= [KNL] - Once boot has completed (that is, after - rcu_end_inkernel_boot() has been invoked), use - only normal grace-period primitives. No effect - on CONFIG_TINY_RCU kernels. - - rcupdate.rcu_task_stall_timeout= [KNL] - Set timeout in jiffies for RCU task stall warning - messages. Disable with a value less than or equal - to zero. - - rcupdate.rcu_self_test= [KNL] - Run the RCU early boot self tests - - rcupdate.rcu_self_test_bh= [KNL] - Run the RCU bh early boot self tests - - rcupdate.rcu_self_test_sched= [KNL] - Run the RCU sched early boot self tests - - rdinit= [KNL] - Format: <full_path> - Run specified binary instead of /init from the ramdisk, - used for early userspace startup. See initrd. - - reboot= [KNL] - Format (x86 or x86_64): - [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \ - [[,]s[mp]#### \ - [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \ - [[,]f[orce] - Where reboot_mode is one of warm (soft) or cold (hard) or gpio, - reboot_type is one of bios, acpi, kbd, triple, efi, or pci, - reboot_force is either force or not specified, - reboot_cpu is s[mp]#### with #### being the processor - to be used for rebooting. - - relax_domain_level= - [KNL, SMP] Set scheduler's default relax_domain_level. - See Documentation/cgroup-v1/cpusets.txt. - - relative_sleep_states= - [SUSPEND] Use sleep state labeling where the deepest - state available other than hibernation is always "mem". - Format: { "0" | "1" } - 0 -- Traditional sleep state labels. - 1 -- Relative sleep state labels. - - 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. - no Disable hibernation and resume. - protect_image Turn on image protection during restoration - (that will set all pages holding image data - during restoration read-only). - - retain_initrd [RAM] Keep initrd memory after extraction - - rfkill.default_state= - 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm, - etc. communication is blocked by default. - 1 Unblocked. - - rfkill.master_switch_mode= - 0 The "airplane mode" button does nothing. - 1 The "airplane mode" button toggles between everything - blocked and the previous configuration. - 2 The "airplane mode" button toggles between everything - blocked and everything unblocked. - - rhash_entries= [KNL,NET] - Set number of hash buckets for route cache - - ro [KNL] Mount root device read-only on boot - - rodata= [KNL] - on Mark read-only kernel memory as read-only (default). - off Leave read-only kernel memory writable for debugging. - - rockchip.usb_uart - Enable the uart passthrough on the designated usb port - on Rockchip SoCs. When active, the signals of the - debug-uart get routed to the D+ and D- pins of the usb - port and the regular usb controller gets disabled. - - 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). - - rproc_mem=nn[KMG][@address] - [KNL,ARM,CMA] Remoteproc physical memory block. - Memory area to be used by remote processor image, - managed by CMA. - - rw [KNL] Mount root device read-write on boot - - S [KNL] Run init in single mode - - s390_iommu= [HW,S390] - Set s390 IOTLB flushing mode - strict - With strict flushing every unmap operation will result in - an IOTLB flush. Default is lazy flushing before reuse, - which is faster. - - sa1100ir [NET] - See drivers/net/irda/sa1100_ir.c. - - sbni= [NET] Granch SBNI12 leased line adapter - - sched_debug [KNL] Enables verbose scheduler debug messages. - - schedstats= [KNL,X86] Enable or disable scheduled statistics. - Allowed values are enable and disable. This feature - incurs a small amount of overhead in the scheduler - but is useful for debugging and performance tuning. - - 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_nomerge [MM] - 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. - - 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] - Same with slab_nomerge. This is supported for legacy. - See slab_nomerge for more information. - - 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 - - smt [KNL,S390] Set the maximum number of threads (logical - CPUs) to use per physical CPU on systems capable of - symmetric multithreading (SMT). Will be capped to the - actual hardware limit. - Format: <integer> - Default: -1 (no limit) - - softlockup_panic= - [KNL] Should the soft-lockup detector generate panics. - Format: <integer> - - softlockup_all_cpu_backtrace= - [KNL] Should the soft-lockup detector generate - backtraces on all cpus. - Format: <integer> - - sonypi.*= [HW] Sony Programmable I/O Control Device driver - See Documentation/laptops/sonypi.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.svc_rpc_per_connection_limit= - [NFS,SUNRPC] - Limit the number of requests that the server will - process in parallel from a single connection. - The default value is 0 (no limit). - - 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. - - suspend.pm_test_delay= - [SUSPEND] - Sets the number of seconds to remain in a suspend test - mode before resuming the system (see - /sys/power/pm_test). Only available when CONFIG_PM_DEBUG - is set. Default value is 5. - - 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/cgroup-v1/memory.txt) - - swiotlb= [ARM,IA-64,PPC,MIPS,X86] - Format: { <int> | force } - <int> -- Number of I/O TLB slabs - force -- force using of bounce buffers even if they - wouldn't be automatically used by the kernel - - 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. - - tcpmhash_entries= [KNL,NET] - Set the number of tcp_metrics_hash slots. - Default value is 8192 or 16384 depending on total - ram pages. This is used to specify the TCP metrics - cache size. See Documentation/networking/ip-sysctl.txt - "tcp_no_metrics_save" section for more details. - - tdfx= [HW,DRM] - - test_suspend= [SUSPEND][,N] - Specify "mem" (for Suspend-to-RAM) or "standby" (for - standby suspend) or "freeze" (for suspend type freeze) - as the system sleep state during system startup with - the optional capability to repeat N number of times. - 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. - - tmem [KNL,XEN] - Enable the Transcendent memory driver if built-in. - - tmem.cleancache=0|1 [KNL, XEN] - Default is on (1). Disable the usage of the cleancache - API to send anonymous pages to the hypervisor. - - tmem.frontswap=0|1 [KNL, XEN] - Default is on (1). Disable the usage of the frontswap - API to send swap pages to the hypervisor. If disabled - the selfballooning and selfshrinking are force disabled. - - tmem.selfballooning=0|1 [KNL, XEN] - Default is on (1). Disable the driving of swap pages - to the hypervisor. - - tmem.selfshrinking=0|1 [KNL, XEN] - Default is on (1). Partial swapoff that immediately - transfers pages from Xen hypervisor back to the - kernel based on different criteria. - - 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. - - topology_updates= [KNL, PPC, NUMA] - Format: {off} - Specify if the kernel should ignore (off) - topology updates sent by the hypervisor to this - LPAR. - - 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 on each cpu. - - trace_event=[event-list] - [FTRACE] Set and start specified trace events in order - to facilitate early boot debugging. The event-list is a - comma separated list of trace events to enable. 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. - - tp_printk[FTRACE] - Have the tracepoints sent to printk as well as the - tracing ring buffer. This is useful for early boot up - where the system hangs or reboots and does not give the - option for reading the tracing buffer or performing a - ftrace_dump_on_oops. - - To turn off having tracepoints sent to printk, - echo 0 > /proc/sys/kernel/tracepoint_printk - Note, echoing 1 into this file without the - tracepoint_printk kernel cmdline option has no effect. - - ** CAUTION ** - - Having tracepoints sent to printk() and activating high - frequency tracepoints such as irq or sched, can cause - the system to live lock. - - traceoff_on_warning - [FTRACE] enable this option to disable tracing when a - warning is hit. This turns off "tracing_on". Tracing can - be enabled again by echoing '1' into the "tracing_on" - file located in /sys/kernel/debug/tracing/ - - This option is useful, as it disables the trace before - the WARNING dump is called, which prevents the trace to - be filled with content caused by the warning output. - - This option can also be set at run time via the sysctl - option: kernel/traceoff_on_warning - - 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.usbfs_snoop_max= - [USB] Maximum number of bytes to snoop in each URB - (default = 65536). - - 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). - - usbcore.nousb [USB] Disable the USB subsystem - - 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 1). - - 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); - f = NO_REPORT_OPCODES (don't use report opcodes - command, uas only); - g = MAX_SECTORS_240 (don't transfer more than - 240 sectors at a time, uas only); - 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); - j = NO_REPORT_LUNS (don't use report luns - command, uas only); - 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); - t = NO_ATA_1X (don't allow ATA(12) and ATA(16) - commands, uas only); - u = IGNORE_UAS (don't bind to the uas driver); - w = NO_WP_DETECT (don't test whether the - medium is write-protected). - y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE - even if the device claims no cache) - 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] - On X86_32, this is an alias for vdso32=. Otherwise: - - vdso=1: enable VDSO (the default) - vdso=0: disable VDSO mapping - - vdso32= [X86] Control the 32-bit vDSO - vdso32=1: enable 32-bit VDSO - vdso32=0 or vdso32=2: disable 32-bit VDSO - - See the help text for CONFIG_COMPAT_VDSO for more - details. If CONFIG_COMPAT_VDSO is set, the default is - vdso32=0; otherwise, the default is vdso32=1. - - For compatibility with older kernels, vdso32=2 is an - alias for vdso32=0. - - Try vdso32=0 if you encounter an error that says: - dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed! - - vector= [IA-64,SMP] - vector=percpu: enable percpu vector domain - - video= [FB] Frame buffer configuration - See Documentation/fb/modedb.txt. - - video.brightness_switch_enabled= [0,1] - If set to 1, on receiving an ACPI notify event - generated by hotkey, video driver will adjust brightness - level and then send out the event to user space through - the allocated input device; If set to 0, video driver - will only send out the event without touching backlight - brightness level. - default: 1 - - 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.color= [VT] Default text color. - Format: 0xYX, X = foreground, Y = background. - Default: 0x07 = light gray on black. - - 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. - - vt.italic= [VT] Default color for italic text; 0-15. - Default: 2 = green. - - vt.underline= [VT] Default color for underlined text; 0-15. - Default: 3 = cyan. - - 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. - - workqueue.watchdog_thresh= - If CONFIG_WQ_WATCHDOG is configured, workqueue can - warn stall conditions and dump internal state to - help debugging. 0 disables workqueue stall - detection; otherwise, it's the stall threshold - duration in seconds. The default value is 30 and - it can be updated at runtime by writing to the - corresponding sysfs file. - - workqueue.disable_numa - By default, all work items queued to unbound - workqueues are affine to the NUMA nodes they're - issued on, which results in better behavior in - general. If NUMA affinity needs to be disabled for - whatever reason, this option can be used. Note - that this also can be controlled per-workqueue for - workqueues visible under /sys/bus/workqueue/. - - workqueue.power_efficient - Per-cpu workqueues are generally preferred because - they show better performance thanks to cache - locality; unfortunately, per-cpu workqueues tend to - be more power hungry than unbound workqueues. - - Enabling this makes the per-cpu workqueues which - were observed to contribute significantly to power - consumption unbound, leading to measurably lower - power usage at the cost of small performance - overhead. - - The default value of this parameter is determined by - the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT. - - workqueue.debug_force_rr_cpu - Workqueue used to implicitly guarantee that work - items queued without explicit CPU specified are put - on the local CPU. This guarantee is no longer true - and while local CPU is still preferred work items - may be put on foreign CPUs. This debug option - forces round-robin CPU selection to flush out - usages which depend on the now broken guarantee. - When enabled, memory and cache locality will be - impacted. - - x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of - default x2apic cluster mode on platforms - supporting x2apic. - - x86_intel_mid_timer= [X86-32,APBT] - Choose timer option for x86 Intel MID platform. - Two valid options are apbt timer only and lapic timer - plus one apbt timer for broadcast timer. - x86_intel_mid_timer=apbt_only | lapic_and_apbt - - xen_512gb_limit [KNL,X86-64,XEN] - Restricts the kernel running paravirtualized under Xen - to use only up to 512 GB of RAM. The reason to do so is - crash analysis tools and Xen tools for doing domain - save/restore/migration must be enabled to handle larger - domains. - - 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 - - xen_nopvspin [X86,XEN] - Disables the ticketlock slowpath using Xen PV - optimizations. - - xen_nopv [X86] - Disables the PV optimizations forcing the HVM guest to - run as generic HVM guest with no PV drivers. - - xirc2ps_cs= [NET,PCMCIA] - Format: - <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] - ------------------------- - -Todo ----- - - Add more DRM drivers. |