-February 2003 Kernel Parameters v2.5.59
+ Kernel Parameters
~~~~~~~~~~~~~~~~~
The following is a consolidated list of the kernel parameters as implemented
usbcore.blinkenlights=1
-The text in square brackets at the beginning of the description states the
-restrictions on the kernel for the said kernel parameter to be valid. The
-restrictions referred to are that the relevant option is valid if:
+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.
ALSA ALSA sound support is enabled.
MCA MCA bus support is enabled.
MDA MDA console support is enabled.
MOUSE Appropriate mouse support is enabled.
+ MSI Message Signaled Interrupts (PCI).
MTD MTD support is enabled.
NET Appropriate network support is enabled.
NUMA NUMA support is enabled.
timesource is not avalible, it defaults to PIT.
Format: { pit | tsc | cyclone | pmtmr }
+ disable_8254_timer
+ enable_8254_timer
+ [IA32/X86_64] Disable/Enable interrupt 0 timer routing
+ over the 8254 in addition to over the IO-APIC. The
+ kernel tries to set a sensible default.
+
hpet= [IA-32,HPET] option to disable HPET and use PIT.
Format: disable
tty<n> Use the virtual console device <n>.
ttyS<n>[,options]
+ ttyUSB0[,options]
Use the specified serial port. The options are of
- the form "bbbbpn", where "bbbb" is the baud rate,
- "p" is parity ("n", "o", or "e"), and "n" is bits.
- Default is "9600n8".
+ 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 also Documentation/serial-console.txt.
+ See Documentation/serial-console.txt for more
+ information. See
+ Documentation/networking/netconsole.txt for an
+ alternative.
uart,io,<addr>[,options]
uart,mmio,<addr>[,options]
eata= [HW,SCSI]
+ ec_intr= [HW,ACPI] ACPI Embedded Controller interrupt mode
+ Format: <int>
+ 0: polling mode
+ non-0: interrupt mode (default)
+
eda= [HW,PS2]
edb= [HW,PS2]
arch/i386/kernel/cpu/cpufreq/elanfreq.c.
elevator= [IOSCHED]
- Format: {"as" | "cfq" | "deadline" | "noop"}
+ Format: {"anticipatory" | "cfq" | "deadline" | "noop"}
See Documentation/block/as-iosched.txt and
Documentation/block/deadline-iosched.txt for details.
- elfcorehdr= [IA-32]
+ elfcorehdr= [IA-32, X86_64]
Specifies physical address of start of kernel core
- image elf header.
- See Documentation/kdump.txt for details.
+ image elf header. Generally kexec loader will
+ pass this option to capture kernel.
+ See Documentation/kdump/kdump.txt for details.
enforcing [SELINUX] Set initial enforcing status.
Format: {"0" | "1"}
load_ramdisk= [RAM] List of ramdisks to load from floppy
See Documentation/ramdisk.txt.
- lockd.udpport= [NFS]
+ 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.tcpport= [NFS]
+ lockd.nlm_udpport=M [NFS] Assign UDP port.
+ Format: <integer>
logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
Format: <irq>
mga= [HW,DRM]
+ migration_cost=
+ [KNL,SMP] debug: override scheduler migration costs
+ Format: <level-1-usecs>,<level-2-usecs>,...
+ This debugging option can be used to override the
+ default scheduler migration cost matrix. The numbers
+ are indexed by 'CPU domain distance'.
+ E.g. migration_cost=1000,2000,3000 on an SMT NUMA
+ box will set up an intra-core migration cost of
+ 1 msec, an inter-core migration cost of 2 msecs,
+ and an inter-node migration cost of 3 msecs.
+
+ WARNING: using the wrong values here can break
+ scheduler performance, so it's only for scheduler
+ development purposes, not production environments.
+
+ migration_debug=
+ [KNL,SMP] migration cost auto-detect verbosity
+ Format=<0|1|2>
+ If a system's migration matrix reported at bootup
+ seems erroneous then this option can be used to
+ increase verbosity of the detection process.
+ We default to 0 (no extra messages), 1 will print
+ some more information, and 2 will be really
+ verbose (probably only useful if you also have a
+ serial console attached to the system).
+
+ migration_factor=
+ [KNL,SMP] multiply/divide migration costs by a factor
+ Format=<percent>
+ This debug option can be used to proportionally
+ increase or decrease the auto-detected migration
+ costs for all entries of the migration matrix.
+ E.g. migration_factor=150 will increase migration
+ costs by 50%. (and thus the scheduler will be less
+ eager migrating cache-hot tasks)
+ migration_factor=80 will decrease migration costs
+ by 20%. (thus the scheduler will be more eager to
+ migrate tasks)
+
+ WARNING: using the wrong values here can break
+ scheduler performance, so it's only for scheduler
+ development purposes, not production environments.
+
mousedev.tap_time=
[MOUSE] Maximum time between finger touching and
leaving touchpad surface for touch to be considered
noexec=on: enable non-executable mappings (default)
noexec=off: disable nn-executable mappings
- nofxsr [BUGS=IA-32]
+ nofxsr [BUGS=IA-32] Disables x86 floating point extended
+ register save and restore. The kernel will only save
+ legacy floating-point registers on task switch.
nohlt [BUGS=ARM]
noltlbs [PPC] Do not use large page/tlb entries for kernel
lowmem mapping on PPC40x.
+ nomca [IA-64] Disable machine check abort handling
+
nomce [IA-32] Machine Check Exception
noresidual [PPC] Don't use residual data on PReP machines.
nosbagart [IA-64]
+ nosep [BUGS=IA-32] Disables x86 SYSENTER/SYSEXIT support.
+
nosmp [SMP] Tells an SMP kernel to act as a UP kernel.
nosync [HW,M68K] Disables sync negotiation for all devices.
pas16= [HW,SCSI]
See header of drivers/scsi/pas16.c.
+ 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]
Mechanism 1.
conf2 [IA-32] Force use of PCI Configuration
Mechanism 2.
+ nommconf [IA-32,X86_64] Disable use of MMCONFIG for PCI
+ Configuration
+ 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.
nosort [IA-32] Don't sort PCI devices according to
order given by the PCI BIOS. This sorting is
done to get a device order compatible with
New name for the ramdisk parameter.
See Documentation/ramdisk.txt.
+ rcu.blimit= [KNL,BOOT] Set maximum number of finished
+ RCU callbacks to process in one batch.
+
+ rcu.qhimark= [KNL,BOOT] Set threshold of queued
+ RCU callbacks over which batch limiting is disabled.
+
+ rcu.qlowmark= [KNL,BOOT] Set threshold of queued
+ RCU callbacks below which batch limiting is re-enabled.
+
+ rcu.rsinterval= [KNL,BOOT,SMP] Set the number of additional
+ RCU callbacks to queued before forcing reschedule
+ on all cpus.
+
rdinit= [KNL]
Format: <full_path>
Run specified binary instead of /init from the ramdisk,
If enabled at boot time, /selinux/disable can be used
later to disable prior to initial policy load.
+ selinux_compat_net =
+ [SELINUX] Set initial selinux_compat_net flag value.
+ Format: { "0" | "1" }
+ 0 -- use new secmark-based packet controls
+ 1 -- use legacy packet controls
+ Default value is 0 (preferred).
+ Value can be changed at runtime via
+ /selinux/compat_net.
+
serialnumber [BUGS=IA-32]
sg_def_reserved_size= [SCSI]
Format:
<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
+ norandmaps Don't use address space randomization
+ Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
-______________________________________________________________________
-Changelog:
-
-2000-06-?? Mr. Unknown
- The last known update (for 2.4.0) - the changelog was not kept before.
-2002-11-24 Petr Baudis <pasky@ucw.cz>
- Randy Dunlap <randy.dunlap@verizon.net>
- Update for 2.5.49, description for most of the options introduced,
- references to other documentation (C files, READMEs, ..), added S390,
- PPC, SPARC, MTD, ALSA and OSS category. Minor corrections and
- reformatting.
-
-2005-10-19 Randy Dunlap <rdunlap@xenotime.net>
- Lots of typos, whitespace, some reformatting.
+______________________________________________________________________
TODO:
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff