| 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" |
| |
| 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) |
| 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 | off | strict | noirq | rsdt | |
| copy_dsdt } |
| force -- enable ACPI if default was off |
| off -- disable ACPI if default was on |
| noirq -- do not use ACPI for IRQ routing |
| strict -- Be less tolerant of platforms that are not |
| strictly ACPI specification compliant. |
| rsdt -- prefer RSDT over (default) XSDT |
| copy_dsdt -- copy DSDT to memory |
| For ARM64, ONLY "acpi=off" 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. |
| |
| 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= # 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. |
| |
| amijoy.map= [HW,JOY] Amiga joystick support |
| Map of devices attached to JOY0DAT and JOY1DAT |
| Format: <a>,<b> |
| See also Documentation/input/joystick.txt |
| |
| analog.map= [HW,JOY] Analog joystick and gamepad support |
| Specifies type or capabilities of an analog joystick |
| connected to one of 16 gameports |
| Format: <type1>,<type2>,..<type16> |
| |
| apc= [HW,SPARC] |
| Power management functions (SPARCstation-4/5 + deriv.) |
| Format: noidle |
| Disable APC CPU standby support. SPARCstation-Fox does |
| not play well with APC CPU idle - disable it if you have |
| APC and your system crashes randomly. |
| |
| apic= [APIC,X86-32] Advanced Programmable Interrupt Controller |
| Change the output verbosity whilst booting |
| Format: { quiet (default) | verbose | debug } |
| Change the amount of debugging information output |
| when initialising the APIC and IO-APIC components. |
| |
| autoconf= [IPV6] |
| See Documentation/networking/ipv6.txt. |
| |
| show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller |
| Limit apic dumping. The parameter defines the maximal |
| number of local apics being dumped. Also it is possible |
| to set it to "all" by meaning -- no limit here. |
| Format: { 1 (default) | 2 | ... | all }. |
| The parameter valid if only apic=debug or |
| apic=verbose is specified. |
| Example: apic=debug show_lapic=all |
| |
| apm= [APM] Advanced Power Management |
| See header of arch/x86/kernel/apm_32.c. |
| |
| arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards |
| Format: <io>,<irq>,<nodeID> |
| |
| ataflop= [HW,M68k] |
| |
| atarimouse= [HW,MOUSE] Atari Mouse |
| |
| atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess, |
| EzKey and similar keyboards |
| |
| atkbd.reset= [HW] Reset keyboard during initialization |
| |
| atkbd.set= [HW] Select keyboard code set |
| Format: <int> (2 = AT (default), 3 = PS/2) |
| |
| atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar |
| keyboards |
| |
| atkbd.softraw= [HW] Choose between synthetic and real raw mode |
| Format: <bool> (0 = real, 1 = synthetic (default)) |
| |
| atkbd.softrepeat= [HW] |
| Use software keyboard repeat |
| |
| 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 |
| |
| 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. |
| |
| 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} |
| |
| 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 |
| |
| 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],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) or 32-bit (mmio32). |
| If none of [io|mmio|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. |
| |
| 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= [IPV6] |
| See Documentation/networking/ipv6.txt. |
| |
| 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. |
| |
| 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> |
| Start an early, polled-mode console on a cadence serial |
| port at the specified address. The cadence serial port |
| must already be setup and configured. Options are not |
| yet supported. |
| |
| 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> |
| 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. |
| |
| 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. |
| |
| 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. |
| |
| 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. |
| |
| goldfish [X86] Enable the goldfish android emulator platform. |
| Don't use this when you are not running on the |
| android emulator |
| |
| 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 |
| |
| 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 |
| |
| ignore_loglevel [KNL] |
| Ignore loglevel setting - this will print /all/ |
| kernel messages to the console. Useful for debugging. |
| We also add it as printk module parameter, so users |
| could change it dynamically, usually by |
| /sys/module/printk/parameters/ignore_loglevel. |
| |
| ihash_entries= [KNL] |
| Set number of hash buckets for inode cache. |
| |
| ima_appraise= [IMA] appraise integrity measurements |
| Format: { "off" | "enforce" | "fix" | "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 |
| |
| 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 6 specify maximum depth of C-state. |
| |
| intel_pstate= [X86] |
| disable |
| Do not enable intel_pstate as the default |
| scaling driver for the supported processors |
| 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. |
| |
| 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. |
| |
| irqfixup [HW] |
| When an interrupt is not handled search all handlers |
| for it. Intended to get systems with badly broken |
| firmware running. |
| |
| irqpoll [HW] |
| When an interrupt is not handled search all handlers |
| for it. Also check all handlers each timer |
| interrupt. Intended to get systems with badly broken |
| firmware running. |
| |
| isapnp= [ISAPNP] |
| Format: <RDP>,<reset>,<pci_scan>,<verbosity> |
| |
| isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler. |
| Format: |
| <cpu number>,...,<cpu number> |
| or |
| <cpu number>-<cpu number> |
| (must be a positive range in ascending order) |
| or a mixture |
| <cpu number>,...,<cpu number>-<cpu number> |
| |
| This option can be used to specify one or more CPUs |
| to isolate from the general SMP balancing and scheduling |
| algorithms. You can move a process onto or off an |
| "isolated" CPU via the CPU affinity syscalls or cpuset. |
| <cpu number> begins at 0 and the maximum value is |
| "number of CPUs in system - 1". |
| |
| This option is the preferred way to isolate CPUs. The |
| alternative -- manually setting the CPU mask of all |
| tasks in the system -- can cause problems and |
| suboptimal load balancer performance. |
| |
| iucv= [HW,NET] |
| |
| 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 |
| |
| js= [HW,JOY] Analog joystick |
| See Documentation/input/joystick.txt. |
| |
| kaslr/nokaslr [X86] |
| Enable/disable kernel and module base offset ASLR |
| (Address Space Layout Randomization) if built into |
| the kernel. When CONFIG_HIBERNATION is selected, |
| kASLR is disabled by default. When kASLR is enabled, |
| hibernation will be disabled. |
| |
| keepinitrd [HW,ARM] |
| |
| kernelcore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter |
| specifies the amount of memory usable by the kernel |
| for non-movable allocations. The requested amount is |
| spread evenly throughout all nodes in the system. The |
| remaining memory in each node is used for Movable |
| pages. In the event, a node is too small to have both |
| kernelcore and Movable pages, kernelcore pages will |
| take priority and other nodes will have a larger number |
| of 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. |
| |
| 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 |
| should make use of. maxcpus=n : n >= 0 limits the |
| kernel to using 'n' processors. n=0 is a special case, |
| it is equivalent to "nosmp", which also disables |
| the IO APIC. |
| |
| max_loop= [LOOP] The number of loop block devices that get |
| (loop.max_loop) unconditionally pre-created at init time. The default |
| number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead |
| of statically allocating a predefined number, loop |
| devices can be requested on-demand with the |
| /dev/loop-control interface. |
| |
| mce [X86-32] Machine Check Exception |
| |
| mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt |
| |
| md= [HW] RAID subsystems devices and level |
| See Documentation/md.txt. |
| |
| mdacon= [MDA] |
| Format: <first>,<last> |
| Specifies range of consoles to be captured by the MDA. |
| |
| mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory |
| Amount of memory to be used when the kernel is not able |
| to see the whole system memory or for test. |
| [X86] Work as limiting max address. Use together |
| with memmap= to avoid physical address space collisions. |
| Without memmap= PCI devices could be placed at addresses |
| belonging to unused RAM. |
| |
| mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel |
| memory. |
| |
| memchunk=nn[KMG] |
| [KNL,SH] Allow user to override the default size for |
| per-device physically contiguous DMA buffers. |
| |
| memmap=exactmap [KNL,X86] Enable setting of an exact |
| E820 memory map, as specified by the user. |
| Such memmap=exactmap lines can be constructed based on |
| BIOS output or other requirements. See the memmap=nn@ss |
| option description. |
| |
| memmap=nn[KMG]@ss[KMG] |
| [KNL] Force usage of a specific region of memory. |
| Region of memory to be used 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. |
| |
| 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_tcpport= |
| [NFS] set the TCP port on which the NFSv4 callback |
| channel should listen. |
| |
| nfs.cache_getent= |
| [NFS] sets the pathname to the program which is used |
| to update the NFS client cache entries. |
| |
| nfs.cache_getent_timeout= |
| [NFS] sets the timeout after which an attempt to |
| update a cache entry is deemed to have failed. |
| |
| nfs.idmap_cache_timeout= |
| [NFS] set the maximum lifetime for idmapper cache |
| entries. |
| |
| nfs.enable_ino64= |
| [NFS] enable 64-bit inode numbers. |
| If zero, the NFS client will fake up a 32-bit inode |
| number for the readdir() and stat() syscalls instead |
| of returning the full 64-bit number. |
| The default is to return 64-bit inode numbers. |
| |
| nfs.max_session_slots= |
| [NFSv4.1] Sets the maximum number of session slots |
| the client will attempt to negotiate with the server. |
| This limits the number of simultaneous RPC requests |
| that the client can send to the NFSv4.1 server. |
| Note that there is little point in setting this |
| value higher than the max_tcp_slot_table_limit. |
| |
| nfs.nfs4_disable_idmapping= |
| [NFSv4] When set to the default of '1', this option |
| ensures that both the RPC level authentication |
| scheme and the NFS level operations agree to use |
| numeric uids/gids if the mount is using the |
| 'sec=sys' security flavour. In effect it is |
| disabling idmapping, which can make migration from |
| legacy NFSv2/v3 systems to NFSv4 easier. |
| Servers that do not support this mode of operation |
| will be autodetected by the client, and it will fall |
| back to using the idmapper. |
| To turn off this behaviour, set the value to '0'. |
| nfs.nfs4_unique_id= |
| [NFS4] Specify an additional fixed unique ident- |
| ification string that NFSv4 clients can insert into |
| their nfs_client_id4 string. This is typically a |
| UUID that is generated at system install time. |
| |
| nfs.send_implementation_id = |
| [NFSv4.1] Send client implementation identification |
| information in exchange_id requests. |
| If zero, no implementation identification information |
| will be sent. |
| The default is to send the implementation identification |
| information. |
| |
| 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] |
| |
| noaltinstr [S390] Disables alternative instructions patching |
| (CPU alternatives feature). |
| |
| noapic [SMP,APIC] Tells the kernel to not make use of any |
| IOAPICs that may be present in the system. |
| |
| noautogroup Disable scheduler automatic task group creation. |
| |
| nobats [PPC] Do not use BATs for mapping kernel lowmem |
| on "Classic" PPC cores. |
| |
| nocache [ARM] |
| |
| noclflush [BUGS=X86] Don't use the CLFLUSH instruction |
| |
| nodelayacct [KNL] Disable per-task delay accounting |
| |
| nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects. |
| |
| nodsp [SH] Disable hardware DSP at boot time. |
| |
| noefi 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. |
| |
| nospectre_v2 [X86] Disable all mitigations for the Spectre variant 2 |
| (indirect branch prediction) vulnerability. System may |
| allow data leaks with this option, which is equivalent |
| to spectre_v2=off. |
| |
| 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] |
| 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. |
| |
| 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. |
| |
| nopcid [X86-64] Disable the PCID cpu feature. |
| |
| norandmaps Don't use address space randomization. Equivalent to |
| echo 0 > /proc/sys/kernel/randomize_va_space |
| |
| 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 |
| |
| nousb [USB] Disable the USB subsystem |
| |
| 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 |
| supporting 'n' processors. Later in runtime you can not |
| use hotplug cpu feature to put more cpu back to online. |
| just like you compile the kernel NR_CPUS=n |
| |
| nr_uarts= [SERIAL] maximum number of UARTs to be registered. |
| |
| numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing. |
| Allowed values are enable and disable |
| |
| numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA. |
| one of ['zone', 'node', 'default'] can be specified |
| This can be set from sysctl after boot. |
| See Documentation/sysctl/vm.txt for details. |
| |
| ohci1394_dma=early [HW] enable debugging via the ohci1394 driver. |
| See Documentation/debugging-via-ohci1394.txt for more |
| info. |
| |
| olpc_ec_timeout= [OLPC] ms delay when issuing EC commands |
| Rather than timing out after 20 ms if an EC |
| command is not properly ACKed, override the length |
| of the timeout. We have interrupts disabled while |
| waiting for the ACK, so if this is set too high |
| interrupts *may* be lost! |
| |
| omap_mux= [OMAP] Override bootloader pin multiplexing. |
| Format: <mux_mode0.mode_name=value>... |
| For example, to override I2C bus2: |
| omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100 |
| |
| oprofile.timer= [HW] |
| Use timer interrupt instead of performance counters |
| |
| oprofile.cpu_type= Force an oprofile cpu type |
| This might be useful if you have an older oprofile |
| userland or if you want common events. |
| Format: { arch_perfmon } |
| arch_perfmon: [X86] Force use of architectural |
| perfmon on Intel CPUs instead of the |
| CPU specific event set. |
| timer: [X86] Force use of architectural NMI |
| timer mode (see also oprofile.timer |
| for generic hr timer mode) |
| [s390] Force legacy basic mode sampling |
| (report cpu_type "timer") |
| |
| oops=panic Always panic on oopses. Default is to just kill the |
| process, but there is a small probability of |
| deadlocking the machine. |
| This will also cause panics on machine check exceptions. |
| Useful together with panic=30 to trigger a reboot. |
| |
| OSS [HW,OSS] |
| See Documentation/sound/oss/oss-parameters.txt |
| |
| 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 |
| |
| 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 |
| Mechanism 1. |
| conf2 [X86] Force use of PCI Configuration |
| Mechanism 2. |
| noaer [PCIE] If the PCIEAER kernel config parameter is |
| enabled, this kernel boot option can be used to |
| disable the use of PCIE advanced error reporting. |
| nodomains [PCI] Disable support for multiple PCI |
| root domains (aka PCI segments, in ACPI-speak). |
| nommconf [X86] Disable use of MMCONFIG for PCI |
| Configuration |
| check_enable_amd_mmconf [X86] check for and enable |
| properly configured MMIO access to PCI |
| config space on AMD family 10h CPU |
| nomsi [MSI] If the PCI_MSI kernel config parameter is |
| enabled, this kernel boot option can be used to |
| disable the use of MSI interrupts system-wide. |
| noioapicquirk [APIC] Disable all boot interrupt quirks. |
| Safety option to keep boot IRQs enabled. This |
| should never be necessary. |
| ioapicreroute [APIC] Enable rerouting of boot IRQs to the |
| primary IO-APIC for bridges that cannot disable |
| boot IRQs. This fixes a source of spurious IRQs |
| when the system masks IRQs. |
| noioapicreroute [APIC] Disable workaround that uses the |
| boot IRQ equivalent of an IRQ that connects to |
| a chipset where boot IRQs cannot be disabled. |
| The opposite of ioapicreroute. |
| biosirq [X86-32] Use PCI BIOS calls to get the interrupt |
| routing table. These calls are known to be buggy |
| on several machines and they hang the machine |
| when used, but on other computers it's the only |
| way to get the interrupt routing table. Try |
| this option if the kernel is unable to allocate |
| IRQs or discover secondary PCI buses on your |
| motherboard. |
| rom [X86] Assign address space to expansion ROMs. |
| Use with caution as certain devices share |
| address decoders between ROMs and other |
| resources. |
| norom [X86] Do not assign address space to |
| expansion ROMs that do not already have |
| BIOS assigned address ranges. |
| nobar [X86] Do not assign address space to the |
| BARs that weren't assigned by the BIOS. |
| irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be |
| assigned automatically to PCI devices. You can |
| make the kernel exclude IRQs of your ISA cards |
| this way. |
| pirqaddr=0xAAAAA [X86] Specify the physical address |
| of the PIRQ table (normally generated |
| by the BIOS) if it is outside the |
| F0000h-100000h range. |
| lastbus=N [X86] Scan all buses thru bus #N. Can be |
| useful if the kernel is unable to find your |
| secondary buses and you want to tell it |
| explicitly which ones they are. |
| assign-busses [X86] Always assign all PCI bus |
| numbers ourselves, overriding |
| whatever the firmware may have done. |
| usepirqmask [X86] Honor the possible IRQ mask stored |
| in the BIOS $PIR table. This is needed on |
| some systems with broken BIOSes, notably |
| some HP Pavilion N5400 and Omnibook XE3 |
| notebooks. This will have no effect if ACPI |
| IRQ routing is enabled. |
| noacpi [X86] Do not use ACPI for IRQ routing |
| or for PCI scanning. |
| use_crs [X86] Use PCI host bridge window information |
| from ACPI. On BIOSes from 2008 or later, this |
| is enabled by default. If you need to use this, |
| please report a bug. |
| nocrs [X86] Ignore PCI host bridge windows from ACPI. |
| If you need to use this, please report a bug. |
| routeirq Do IRQ routing for all PCI devices. |
| This is normally done in pci_enable_device(), |
| so this option is a temporary workaround |
| for broken drivers that don't call it. |
| skip_isa_align [X86] do not align io start addr, so can |
| handle more pci cards |
| firmware [ARM] Do not re-enumerate the bus but instead |
| just use the configuration from the |
| bootloader. This is currently used on |
| IXP2000 systems where the bus has to be |
| configured a certain way for adjunct CPUs. |
| noearly [X86] Don't do any early type 1 scanning. |
| This might help on some broken boards which |
| machine check when some devices' config space |
| is read. But various workarounds are disabled |
| and some IOMMU drivers will not work. |
| bfsort Sort PCI devices into breadth-first order. |
| This sorting is done to get a device |
| order compatible with older (<= 2.4) kernels. |
| nobfsort Don't sort PCI devices into breadth-first order. |
| pcie_bus_tune_off Disable PCIe MPS (Max Payload Size) |
| tuning and use the BIOS-configured MPS defaults. |
| pcie_bus_safe Set every device's MPS to the largest value |
| supported by all devices below the root complex. |
| pcie_bus_perf Set device MPS to the largest allowable MPS |
| based on its parent bus. Also set MRRS (Max |
| Read Request Size) to the largest supported |
| value (no larger than the MPS that the device |
| or bus can support) for best performance. |
| pcie_bus_peer2peer Set every device's MPS to 128B, which |
| every device is guaranteed to support. This |
| configuration allows peer-to-peer DMA between |
| any pair of devices, possibly at the cost of |
| reduced performance. This also guarantees |
| that hot-added devices will work. |
| cbiosize=nn[KMG] The fixed amount of bus space which is |
| reserved for the CardBus bridge's IO window. |
| The default value is 256 bytes. |
| cbmemsize=nn[KMG] The fixed amount of bus space which is |
| reserved for the CardBus bridge's memory |
| window. The default value is 64 megabytes. |
| resource_alignment= |
| Format: |
| [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...] |
| Specifies alignment and device to reassign |
| aligned memory resources. |
| If <order of align> is not specified, |
| PAGE_SIZE is used as alignment. |
| PCI-PCI bridge can be specified, if resource |
| windows need to be expanded. |
| ecrc= Enable/disable PCIe ECRC (transaction layer |
| end-to-end CRC checking). |
| bios: Use BIOS/firmware settings. This is the |
| the default. |
| off: Turn ECRC off |
| on: Turn ECRC on. |
| hpiosize=nn[KMG] The fixed amount of bus space which is |
| reserved for hotplug bridge's IO window. |
| Default size is 256 bytes. |
| hpmemsize=nn[KMG] The fixed amount of bus space which is |
| reserved for hotplug bridge's memory window. |
| Default size is 2 megabytes. |
| realloc= Enable/disable reallocating PCI bridge resources |
| if allocations done by BIOS are too small to |
| accommodate resources required by all child |
| devices. |
| off: Turn realloc off |
| on: Turn realloc on |
| realloc same as realloc=on |
| noari do not use PCIe ARI. |
| pcie_scan_all Scan all possible PCIe devices. Otherwise we |
| only look for one device below a PCIe downstream |
| port. |
| |
| pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power |
| Management. |
| off Disable ASPM. |
| force Enable ASPM even on devices that claim not to support it. |
| WARNING: Forcing ASPM on may cause system lockups. |
| |
| pcie_hp= [PCIE] PCI Express Hotplug driver options: |
| nomsi Do not use MSI for PCI Express Native Hotplug (this |
| makes all PCIe ports use INTx for hotplug services). |
| |
| pcie_ports= [PCIE] PCIe ports handling: |
| auto Ask the BIOS whether or not to use native PCIe services |
| associated with PCIe ports (PME, hot-plug, AER). Use |
| them only if that is allowed by the BIOS. |
| native Use native PCIe services associated with PCIe ports |
| unconditionally. |
| compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe |
| ports driver. |
| |
| pcie_pme= [PCIE,PM] Native PCIe PME signaling options: |
| nomsi Do not use MSI for native PCIe PME signaling (this makes |
| all PCIe root ports use INTx for all services). |
| |
| pcmv= [HW,PCMCIA] BadgePAD 4 |
| |
| pd_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>.... |
| |
| print-fatal-signals= |
| [KNL] debug: print fatal signals |
| |
| If enabled, warn about various signal handling |
| related application anomalies: too many signals, |
| too many POSIX.1 timers, fatal signals causing a |
| coredump - etc. |
| |
| If you hit the warning due to signal overflow, |
| you might want to try "ulimit -i unlimited". |
| |
| default: off. |
| |
| printk.always_kmsg_dump= |
| Trigger kmsg_dump for cases other than kernel oops or |
| panics |
| Format: <bool> (1/Y/y=enable, 0/N/n=disable) |
| default: disabled |
| |
| printk.time= Show timing data prefixed to each printk message line |
| Format: <bool> (1/Y/y=enable, 0/N/n=disable) |
| |
| processor.max_cstate= [HW,ACPI] |
| Limit processor to maximum C-state |
| max_cstate=9 overrides any DMI blacklist limit. |
| |
| processor.nocst [HW,ACPI] |
| Ignore the _CST method to determine C-states, |
| instead using the legacy FADT method |
| |
| profile= [KNL] Enable kernel profiling via /proc/profile |
| Format: [schedule,]<number> |
| Param: "schedule" - profile schedule points. |
| Param: <number> - step/bucket size as a power of 2 for |
| statistical time based profiling. |
| Param: "sleep" - profile D-state sleeping (millisecs). |
| Requires CONFIG_SCHEDSTATS |
| Param: "kvm" - profile VM exits. |
| |
| prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk |
| before loading. |
| See Documentation/blockdev/ramdisk.txt. |
| |
| psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to |
| probe for; one of (bare|imps|exps|lifebook|any). |
| psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports |
| per second. |
| psmouse.resetafter= [HW,MOUSE] |
| Try to reset the device after so many bad packets |
| (0 = never). |
| psmouse.resolution= |
| [HW,MOUSE] Set desired mouse resolution, in dpi. |
| psmouse.smartscroll= |
| [HW,MOUSE] Controls Logitech smartscroll autorepeat. |
| 0 = disabled, 1 = enabled (default). |
| |
| pstore.backend= Specify the name of the pstore backend to use |
| |
| pt. [PARIDE] |
| See Documentation/blockdev/paride.txt. |
| |
| pti= [X86_64] Control Page Table Isolation of user and |
| kernel address spaces. Disabling this feature |
| removes hardening, but improves performance of |
| system calls and interrupts. |
| |
| on - unconditionally enable |
| off - unconditionally disable |
| auto - kernel detects whether your CPU model is |
| vulnerable to issues that PTI mitigates |
| |
| Not specifying this option is equivalent to pti=auto. |
| |
| nopti [X86_64] |
| Equivalent to pti=off |
| |
| pty.legacy_count= |
| [KNL] Number of legacy pty's. Overwrites compiled-in |
| default number. |
| |
| quiet [KNL] Disable most log messages |
| |
| r128= [HW,DRM] |
| |
| raid= [HW,RAID] |
| See Documentation/md.txt. |
| |
| ramdisk_blocksize= [RAM] |
| See Documentation/blockdev/ramdisk.txt. |
| |
| ramdisk_size= [RAM] Sizes of RAM disks in kilobytes |
| See Documentation/blockdev/ramdisk.txt. |
| |
| rcu_nocbs= [KNL] |
| 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. |
| |
| 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_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. |
| |
| 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_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/cgroups/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. |
| |
| 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 |
| |
| 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. |
| |
| 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 |
| |
| 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 |
| |
| spectre_v2= [X86] Control mitigation of Spectre variant 2 |
| (indirect branch speculation) vulnerability. |
| |
| on - unconditionally enable |
| off - unconditionally disable |
| auto - kernel detects whether your CPU model is |
| vulnerable |
| |
| Selecting 'on' will, and 'auto' may, choose a |
| mitigation method at run time according to the |
| CPU, the available microcode, the setting of the |
| CONFIG_RETPOLINE configuration option, and the |
| compiler with which the kernel was built. |
| |
| Specific mitigations can also be selected manually: |
| |
| retpoline - replace indirect branches |
| retpoline,generic - google's original retpoline |
| retpoline,amd - AMD-specific minimal thunk |
| |
| Not specifying this option is equivalent to |
| spectre_v2=auto. |
| |
| spia_io_base= [HW,MTD] |
| spia_fio_base= |
| spia_pedr= |
| spia_peddr= |
| |
| stack_guard_gap= [MM] |
| override the default stack gap protection. The value |
| is in page units and it defines how many pages prior |
| to (for stacks growing down) resp. after (for stacks |
| growing up) the main stack are reserved for no other |
| mapping. Default value is 256 pages. |
| |
| stacktrace [FTRACE] |
| Enabled the stack tracer on boot up. |
| |
| stacktrace_filter=[function-list] |
| [FTRACE] Limit the functions that the stack tracer |
| will trace at boot up. function-list is a comma separated |
| list of functions. This list can be changed at run |
| time by the stack_trace_filter file in the debugfs |
| tracing directory. Note, this enables stack tracing |
| and the stacktrace above is not needed. |
| |
| sti= [PARISC,HW] |
| Format: <num> |
| Set the STI (builtin display/keyboard on the HP-PARISC |
| machines) console (graphic card) which should be used |
| as the initial boot-console. |
| See also comment in drivers/video/console/sticore.c. |
| |
| sti_font= [HW] |
| See comment in drivers/video/console/sticore.c. |
| |
| stifb= [HW] |
| Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]] |
| |
| sunrpc.min_resvport= |
| sunrpc.max_resvport= |
| [NFS,SUNRPC] |
| SunRPC servers often require that client requests |
| originate from a privileged port (i.e. a port in the |
| range 0 < portnr < 1024). |
| An administrator who wishes to reserve some of these |
| ports for other uses may adjust the range that the |
| kernel's sunrpc client considers to be privileged |
| using these two parameters to set the minimum and |
| maximum port values. |
| |
| sunrpc.pool_mode= |
| [NFS] |
| Control how the NFS server code allocates CPUs to |
| service thread pools. Depending on how many NICs |
| you have and where their interrupts are bound, this |
| option will affect which CPUs will do NFS serving. |
| Note: this parameter cannot be changed while the |
| NFS server is running. |
| |
| auto the server chooses an appropriate mode |
| automatically using heuristics |
| global a single global pool contains all CPUs |
| percpu one pool for each CPU |
| pernode one pool for each NUMA node (equivalent |
| to global on non-NUMA machines) |
| |
| sunrpc.tcp_slot_table_entries= |
| sunrpc.udp_slot_table_entries= |
| [NFS,SUNRPC] |
| Sets the upper limit on the number of simultaneous |
| RPC calls that can be sent from the client to a |
| server. Increasing these values may allow you to |
| improve throughput, but will also increase the |
| amount of memory reserved for use by the client. |
| |
| 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/cgroups/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. |
| 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.blinkenlights= |
| [USB] Set to cycle leds on hubs (default 0 = off). |
| |
| usbcore.old_scheme_first= |
| [USB] Start with the old device initialization |
| scheme (default 0 = off). |
| |
| usbcore.usbfs_memory_mb= |
| [USB] Memory limit (in MB) for buffers allocated by |
| usbfs (default = 16, 0 = max = 2047). |
| |
| usbcore.use_both_schemes= |
| [USB] Try the other device initialization scheme |
| if the first one fails (default 1 = enabled). |
| |
| usbcore.initial_descriptor_timeout= |
| [USB] Specifies timeout for the initial 64-byte |
| USB_REQ_GET_DESCRIPTOR request in milliseconds |
| (default 5000 = 5.0 seconds). |
| |
| usbhid.mousepoll= |
| [USBHID] The interval which mice are to be polled at. |
| |
| usb-storage.delay_use= |
| [UMS] The delay in seconds before a new device is |
| scanned for Logical Units (default 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). |
| 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.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. |
| |
| 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. |