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Diffstat (limited to 'Documentation/kernel-parameters.txt')
| -rw-r--r-- | Documentation/kernel-parameters.txt | 280 |
1 files changed, 224 insertions, 56 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 50680a59a2f..b7fa2f59945 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1,27 +1,37 @@ Kernel Parameters ~~~~~~~~~~~~~~~~~ -The following is a consolidated list of the kernel parameters as implemented -(mostly) by the __setup() macro and sorted into English Dictionary order -(defined as ignoring all punctuation and sorting digits before letters in a -case insensitive manner), and with descriptions where known. - -Module parameters for loadable modules are specified only as the -parameter name with optional '=' and value as appropriate, such as: - - modprobe usbcore blinkenlights=1 - -Module parameters for modules that are built into the kernel image -are specified on the kernel command line with the module name plus -'.' plus parameter name, with '=' and value if appropriate, such as: - - usbcore.blinkenlights=1 +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 @@ -214,6 +224,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. unusable. The "log_buf_len" parameter may be useful if you need to capture more output. + 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 @@ -229,7 +244,31 @@ bytes respectively. Such letter suffixes can also be entirely omitted. use by PCI Format: <irq>,<irq>... - acpi_no_auto_ssdt [HW,ACPI] Disable automatic loading of SSDT + 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_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. + + 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_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS Format: To spoof as Windows 98: ="Microsoft Windows" @@ -298,8 +337,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted. acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode Format: { level | edge | high | low } - acpi_serialize [HW,ACPI] force serialization of AML methods - acpi_skip_timer_override [HW,ACPI] Recognize and ignore IRQ0/pin2 Interrupt Override. For broken nForce2 BIOS resulting in XT-PIC timer. @@ -343,6 +380,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted. no: ACPI OperationRegions are not marked as reserved, no further checks are performed. + acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump + kernels. + add_efi_memmap [EFI; X86] Include EFI memory map in kernel's map of available physical RAM. @@ -463,6 +503,22 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 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> @@ -515,7 +571,14 @@ bytes respectively. Such letter suffixes can also be entirely omitted. cgroup_disable= [KNL] Disable a particular controller Format: {name of the controller(s) to disable} - {Currently supported controllers - "memory"} + 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" } @@ -577,8 +640,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. Also note the kernel might malfunction if you disable some critical bits. - cma=nn[MG] [ARM,KNL] - Sets the size of kernel global memory area for contiguous + 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. For more information, see include/linux/dma-contiguous.h @@ -764,16 +830,18 @@ bytes respectively. Such letter suffixes can also be entirely omitted. dhash_entries= [KNL] Set number of hash buckets for dentry cache. - digi= [HW,SERIAL] - IO parameters + enable/disable command. - - digiepca= [HW,SERIAL] - See drivers/char/README.epca and - Documentation/serial/digiepca.txt. - disable= [IPV6] See Documentation/networking/ipv6.txt. + disable_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. @@ -835,7 +903,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted. Enable debug messages at boot time. See Documentation/dynamic-debug-howto.txt for details. + 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. + uart[8250],io,<addr>[,options] uart[8250],mmio,<addr>[,options] uart[8250],mmio32,<addr>[,options] @@ -845,7 +919,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted. (mmio) or 32-bit (mmio32). The options are the same as for ttyS, above. - earlyprintk= [X86,SH,BLACKFIN,ARM] + 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. + + smh Use ARM semihosting calls for early console. + + earlyprintk= [X86,SH,BLACKFIN,ARM,M68k] earlyprintk=vga earlyprintk=efi earlyprintk=xen @@ -881,6 +963,14 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 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 @@ -890,6 +980,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted. edd= [EDD] Format: {"off" | "on" | "skip[mbr]"} + efi= [EFI] + Format: { "old_map" } + old_map [X86-64]: switch to the old ioremap-based EFI + runtime services mapping. 32-bit still uses this one by + default. + 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 @@ -962,6 +1058,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 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 @@ -1013,7 +1116,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted. debugfs files are removed at module unload time. gpt [EFI] Forces disk with valid GPT signature but - invalid Protective MBR to be treated as GPT. + 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. @@ -1217,6 +1322,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 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 @@ -1365,6 +1474,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 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 @@ -1415,6 +1531,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted. Valid arguments: on, off Default: on + 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. @@ -1529,6 +1652,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted. * 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. @@ -1666,16 +1791,16 @@ bytes respectively. Such letter suffixes can also be entirely omitted. option description. memmap=nn[KMG]@ss[KMG] - [KNL] Force usage of a specific region of memory - Region of memory to be used, from ss to ss+nn. + [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 used, from ss to ss+nn. + 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 used, from ss to ss+nn. + Region of memory to be reserved is from ss to ss+nn. Example: Exclude memory from 0x18690000-0x1869ffff memmap=64K$0x18690000 or @@ -2062,6 +2187,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 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 @@ -2135,10 +2262,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted. noreplace-smp [X86-32,SMP] Don't replace SMP instructions with UP alternatives - nordrand [X86] Disable the direct use of the RDRAND - instruction even if it is supported by the - processor. RDRAND is still available to user - space applications. + 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. @@ -2249,6 +2376,14 @@ bytes respectively. Such letter suffixes can also be entirely omitted. timeout < 0: reboot immediately Format: <timeout> + 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#> @@ -2473,6 +2608,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 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. @@ -2625,7 +2767,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 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. @@ -2641,14 +2782,20 @@ bytes respectively. Such letter suffixes can also be entirely omitted. periodically wake up to do the polling. rcutree.blimit= [KNL] - Set maximum number of finished RCU callbacks to process - in one batch. + Set maximum number of finished RCU callbacks to + process in one batch. rcutree.rcu_fanout_leaf= [KNL] Increase the number of CPUs assigned to each leaf rcu_node structure. Useful for very large systems. + 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. @@ -2661,8 +2808,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted. value is one, and maximum value is HZ. rcutree.qhimark= [KNL] - Set threshold of queued - RCU callbacks over which batch limiting is disabled. + Set threshold of queued RCU callbacks beyond which + batch limiting is disabled. rcutree.qlowmark= [KNL] Set threshold of queued RCU callbacks below which @@ -2800,6 +2947,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted. [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] @@ -2837,15 +2991,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted. 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 rhash_entries= [KNL,NET] Set number of hash buckets for route cache - riscom8= [HW,SERIAL] - Format: <io_board1>[,<io_board2>[,...<io_boardN>]] - ro [KNL] Mount root device read-only on boot root= [KNL] Root filesystem @@ -2984,12 +3136,14 @@ bytes respectively. Such letter suffixes can also be entirely omitted. [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 - specialix= [HW,SERIAL] Specialix multi-serial port adapter - See Documentation/serial/specialix.txt. - spia_io_base= [HW,MTD] spia_fio_base= spia_pedr= @@ -3061,7 +3215,11 @@ bytes respectively. Such letter suffixes can also be entirely omitted. controller if no parameter or 1 is given or disable it if 0 is given (See Documentation/cgroups/memory.txt) - swiotlb= [IA-64] Number of I/O TLB slabs + 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] @@ -3342,14 +3500,24 @@ bytes respectively. Such letter suffixes can also be entirely omitted. of CONFIG_HIGHPTE. vdso= [X86,SH] - vdso=2: enable compat VDSO (default with COMPAT_VDSO) - vdso=1: enable VDSO (default) + On X86_32, this is an alias for vdso32=. Otherwise: + + vdso=1: enable VDSO (the default) vdso=0: disable VDSO mapping - vdso32= [X86] - vdso32=2: enable compat VDSO (default with COMPAT_VDSO) - vdso32=1: enable 32-bit VDSO (default) - vdso32=0: disable 32-bit VDSO mapping + 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 |