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Diffstat (limited to 'Documentation/admin-guide/kernel-parameters.rst')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.rst | 174 |
1 files changed, 48 insertions, 126 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst index 6d421694d98e..02a725536cc5 100644 --- a/Documentation/admin-guide/kernel-parameters.rst +++ b/Documentation/admin-guide/kernel-parameters.rst @@ -1,10 +1,12 @@ +.. SPDX-License-Identifier: GPL-2.0 + .. _kernelparameters: The kernel's command-line parameters ==================================== -The following is a consolidated list of the kernel parameters as -implemented by the __setup(), core_param() and module_param() macros +The following is a consolidated list of the kernel parameters as implemented +by the __setup(), early_param(), 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. @@ -27,6 +29,16 @@ 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. +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}``. + +Special handling +---------------- + Hyphens (dashes) and underscores are equivalent in parameter names, so:: log_buf_len=1M print-fatal-signals=1 @@ -39,8 +51,8 @@ Double-quotes can be used to protect spaces in values, e.g.:: param="spaces in here" -cpu lists: ----------- +cpu lists +~~~~~~~~~ Some kernel parameters take a list of CPUs as a value, e.g. isolcpus, nohz_full, irqaffinity, rcu_nocbs. The format of this list is: @@ -60,7 +72,7 @@ Note that for the special case of a range one can split the range into equal sized groups and for each group use some amount from the beginning of that group: - <cpu number>-cpu number>:<used size>/<group size> + <cpu number>-<cpu number>:<used size>/<group size> For example one can add to the command line following parameter: @@ -68,127 +80,47 @@ For example one can add to the command line following parameter: where the final item represents CPUs 100,101,125,126,150,151,... +The value "N" can be used to represent the numerically last CPU on the system, +i.e "foo_cpus=16-N" would be equivalent to "16-31" on a 32 core system. +Keep in mind that "N" is dynamic, so if system changes cause the bitmap width +to change, such as less cores in the CPU list, then N and any ranges using N +will also change. Use the same on a small 4 core system, and "16-N" becomes +"16-3" and now the same boot input will be flagged as invalid (start > end). -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 special case-tolerant group name "all" has a meaning of selecting all CPUs, +so that "nohz_full=all" is the equivalent of "nohz_full=0-N". + +The semantics of "N" and "all" is supported on a level of bitmaps and holds for +all users of bitmap_parselist(). + +Metric suffixes +~~~~~~~~~~~~~~~ -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. - ARM64 ARM64 architecture is enabled. - AX25 Appropriate AX.25 support 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. - ISOL CPU Isolation 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.rst. - 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. - OF Devicetree 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. - RDT Intel Resource Director Technology. - 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.rst. - X86 Either 32-bit or 64-bit x86 (same as X86-32+X86-64) - X86_UV SGI UV support is enabled. - XEN Xen support is enabled - -In addition, the following text indicates that the option:: - - BUGS= Relates to possible processor bugs on the said processor. - KNL Is a kernel start-up parameter. - BOOT Is a boot loader parameter. +The [KMG] suffix is commonly described after a number of kernel +parameter values. 'K', 'M', 'G', 'T', 'P', and 'E' suffixes are allowed. +These letters represent the _binary_ multipliers 'Kilo', 'Mega', 'Giga', +'Tera', 'Peta', and 'Exa', equaling 2^10, 2^20, 2^30, 2^40, 2^50, and +2^60 bytes respectively. Such letter suffixes can also be entirely omitted. + +Kernel Build Options +-------------------- + +The parameters listed below are only valid if certain kernel build options +were enabled and if respective hardware is present. This list should be kept +in alphabetical order. The text in square brackets at the beginning +of each description states the restrictions within which a parameter +is applicable. 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.rst>. +need or coordination with <Documentation/arch/x86/boot.rst>. There are also arch-specific kernel-parameters not documented here. -See for example <Documentation/x86/x86_64/boot-options.rst>. 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 +a trailing = on the name of any parameter states that the 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. @@ -197,17 +129,7 @@ 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', equaling 2^10, 2^20, and 2^30 -bytes respectively. Such letter suffixes can also be entirely omitted: +./include/uapi/asm-generic/setup.h as COMMAND_LINE_SIZE. .. include:: kernel-parameters.txt :literal: - -Todo ----- - - Add more DRM drivers. |