-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.
APM Advanced Power Management support is enabled.
AX25 Appropriate AX.25 support is enabled.
CD Appropriate CD support is enabled.
- DEVFS devfs support is enabled.
DRM Direct Rendering Management support is enabled.
EDD BIOS Enhanced Disk Drive Services (EDD) is enabled
EFI EFI Partitioning (GPT) 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.
+ GENERIC_TIME The generic timeofday code is enabled.
NFS Appropriate NFS support is enabled.
OSS OSS sound support is enabled.
PARIDE The ParIDE subsystem is enabled.
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.
+
+
53c7xx= [HW,SCSI] Amiga SCSI controllers
See header of drivers/scsi/53c7xx.c.
See also Documentation/scsi/ncr53c7xx.txt.
acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
Format: <irq>,<irq>...
+ acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
+ Format: To spoof as Windows 98: ="Microsoft Windows"
+
acpi_osi= [HW,ACPI] empty param disables _OSI
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.
+ 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
acpi_dbg_layer= [HW,ACPI]
Format: <int>
override platform specific driver.
See also Documentation/acpi-hotkey.txt.
+ acpi_pm_good [IA-32,X86-64]
+ Override the pmtimer bug detection: force the kernel
+ to assume that this machine's pmtimer latches its value
+ and always returns good values.
+
enable_timer_pin_1 [i386,x86-64]
Enable PIN 1 of APIC timer
Can be useful to work around chipset bugs
autotest [IA64]
- awe= [HW,OSS] AWE32/SB32/AWE64 wave table synth
- Format: <io>,<memsize>,<isapnp>
-
aztcd= [HW,CD] Aztech CD268 CDROM driver
Format: <io>,0x79 (?)
Value can be changed at runtime via
/selinux/checkreqprot.
- clock= [BUGS=IA-32,HW] gettimeofday timesource override.
- Forces specified timesource (if avaliable) to be used
- when calculating gettimeofday(). If specicified
- timesource is not avalible, it defaults to PIT.
+ clock= [BUGS=IA-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 }
disable_8254_timer
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]
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.
+
decnet= [HW,NET]
Format: <area>[,<node>]
See also Documentation/networking/decnet.txt.
- devfs= [DEVFS]
- See Documentation/filesystems/devfs/boot-options.
-
dhash_entries= [KNL]
Set number of hash buckets for dentry cache.
Default value is 0.
Value can be changed at runtime via /selinux/enforce.
- es1370= [HW,OSS]
- Format: <lineout>[,<micbias>]
- See also header of sound/oss/es1370.c.
-
es1371= [HW,OSS]
Format: <spdif>,[<nomix>,[<amplifier>]]
See also header of sound/oss/es1371.c.
eurwdt= [HW,WDT] Eurotech CPU-1220/1410 onboard watchdog.
Format: <io>[,<irq>]
+ failslab=
+ fail_page_alloc=
+ fail_make_request=[KNL]
+ General fault injection mechanism.
+ Format: <interval>,<probability>,<space>,<times>
+ See also /Documentation/fault-injection/.
+
fd_mcs= [HW,SCSI]
See header of drivers/scsi/fd_mcs.c.
floppy= [HW]
See Documentation/floppy.txt.
- ftape= [HW] Floppy Tape subsystem debugging options.
- See Documentation/ftape.txt.
-
gamecon.map[2|3]=
[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
support via parallel port (up to 5 devices per port)
gscd= [HW,CD]
Format: <io>
- gt96100eth= [NET] MIPS GT96100 Advanced Communication Controller
-
- gus= [HW,OSS]
- Format: <io>,<irq>,<dma>,<dma16>
-
gvp11= [HW,SCSI]
hashdist= [KNL,NUMA] Large hashes allocated during boot
hugepages= [HW,IA-32,IA-64] Maximal number of HugeTLB pages.
- noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing
-
i8042.direct [HW] Put keyboard port into non-translated mode
- i8042.dumbkbd [HW] Pretend that controlled can only read data from
- keyboard and can not control its state
+ 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
idle= [HW]
Format: idle=poll or idle=halt
+ ignore_loglevel [KNL]
+ Ignore loglevel setting - this will print /all/
+ kernel messages to the console. Useful for debugging.
+
ihash_entries= [KNL]
Set number of hash buckets for inode cache.
ips= [HW,SCSI] Adaptec / IBM ServeRAID controller
See header of drivers/scsi/ips.c.
+ 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>....
+
irqfixup [HW]
When an interrupt is not handled search all handlers
for it. Intended to get systems with badly broken
Format: <RDP>,<reset>,<pci_scan>,<verbosity>
isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
- Format: <cpu number>,...,<cpu number>
+ 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. The only way to move a process onto or off
(machvec) in a generic kernel.
Example: machvec=hpzx1_swiotlb
- mad16= [HW,OSS] Format:
- <io>,<irq>,<dma>,<dma16>,<mpu_io>,<mpu_irq>,<joystick>
-
- maui= [HW,OSS]
- Format: <io>,<irq>
-
max_loop= [LOOP] Maximum number of loopback devices that can
be mounted
Format: <1-256>
emulation library even if a 387 maths coprocessor
is present.
+ noaliencache [MM, NUMA] Disables the allcoation of alien caches in
+ the slab allocator. Saves per-node memory, but will
+ impact performance on real NUMA hardware.
+
noalign [KNL,ARM]
noapic [SMP,APIC] Tells the kernel to not make use of any
nocache [ARM]
+ nodelayacct [KNL] Disable per-task delay accounting
+
nodisconnect [HW,SCSI,M68K] Disables SCSI disconnects.
noexec [IA-64]
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]
in certain environments such as networked servers or
real-time systems.
+ noirqbalance [IA-32,SMP,KNL] Disable kernel irq balancing
+
noirqdebug [IA-32] Disables the code which attempts to detect and
disable unhandled interrupt sources.
+ no_timer_check [IA-32,X86_64,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
noltlbs [PPC] Do not use large page/tlb entries for kernel
lowmem mapping on PPC40x.
- nomce [IA-32] Machine Check Exception
-
nomca [IA-64] Disable machine check abort handling
+ nomce [IA-32] Machine Check Exception
+
noresidual [PPC] Don't use residual data on PReP machines.
noresume [SWSUSP] Disables resume and restores original swap
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.
opl3= [HW,OSS]
Format: <io>
- opl3sa= [HW,OSS]
- Format: <io>,<irq>,<dma>,<dma2>,<mpu_io>,<mpu_irq>
-
opl3sa2= [HW,OSS] Format:
<io>,<irq>,<dma>,<dma2>,<mss_io>,<mpu_io>,<ymode>,<loopback>[,<isapnp>,<multiple]
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.
+ mmconf [IA-32,X86_64] Enable use of MMCONFIG for PCI
+ Configuration
nommconf [IA-32,X86_64] Disable use of MMCONFIG for PCI
Configuration
+ msi [MSI] If the PCI_MSI kernel config parameter is
+ enabled, this kernel boot option can be used to
+ enable the use of MSI interrupts system-wide.
+ 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
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.
pcmv= [HW,PCMCIA] BadgePAD 4
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)
processor.max_cstate= [HW,ACPI]
Limit processor to maximum C-state
pt. [PARIDE]
See Documentation/paride.txt.
- quiet= [KNL] Disable log messages
+ quiet [KNL] Disable most log messages
r128= [HW,DRM]
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,
reboot= [BUGS=IA-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
Format: <reboot_mode>[,<reboot_mode2>[,...]]
- See arch/*/kernel/reboot.c.
+ See arch/*/kernel/reboot.c or arch/*/kernel/process.c
reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
+ reservetop= [IA-32]
+ Format: nn[KMG]
+ Reserves a hole at the top of the kernel virtual
+ address space.
+
+ reset_devices [KNL] Force drivers to reset the underlying device
+ during initialization.
+
resume= [SWSUSP]
Specify the partition device for software suspend
+ 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
+
rhash_entries= [KNL,NET]
Set number of hash buckets for route cache
scsi_logging= [SCSI]
+ scsi_mod.scan= [SCSI] sync (default) scans SCSI busses as they are
+ discovered. async scans them in kernel threads,
+ allowing boot to proceed. none ignores them, expecting
+ user space to do the scan.
+
selinux [SELINUX] Disable or enable SELinux at boot time.
Format: { "0" | "1" }
See security/selinux/Kconfig help text.
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]
- sgalaxy= [HW,OSS]
- Format: <io>,<irq>,<dma>,<dma2>,<sgbase>
-
shapers= [NET]
Maximal number of shapers.
snd-ymfpci= [HW,ALSA]
- sonicvibes= [HW,OSS]
- Format: <reverb>
-
sonycd535= [HW,CD]
Format: <io>[,<irq>]
sym53c416= [HW,SCSI]
See header of drivers/scsi/sym53c416.c.
+ sysrq_always_enabled
+ [KNL]
+ Ignore sysrq setting - this boot parameter will
+ neutralize any effect of /proc/sys/kernel/sysrq.
+ Useful for debugging.
+
t128= [HW,SCSI]
See header of drivers/scsi/t128.c.
time Show timing data prefixed to each printk message line
+ clocksource= [GENERIC_TIME] Override the default clocksource
+ Override the default clocksource and use the clocksource
+ with the name specified.
+
tipar.timeout= [HW,PPT]
Set communications timeout in tenths of a second
(default 15).
uart6850= [HW,OSS]
Format: <io>,<irq>
+ 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.
+
usbhid.mousepoll=
[USBHID] The interval which mice are to be polled at.
+ vdso= [IA-32]
+ vdso=1: enable VDSO (default)
+ vdso=0: disable VDSO mapping
+
video= [FB] Frame buffer configuration
See Documentation/fb/modedb.txt.
decrease the size and leave more room for directly
mapped kernel RAM.
- vmhalt= [KNL,S390]
+ 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]
+ vmpoff= [KNL,S390] Perform z/VM CP command after power off.
+ Format: <command>
waveartist= [HW,OSS]
Format: <io>,<irq>,<dma>,<dma2>
norandmaps Don't use address space randomization
Equivalent to echo 0 > /proc/sys/kernel/randomize_va_space
+ unwind_debug=N N > 0 will enable dwarf2 unwinder debugging
+ This is useful to get more information why
+ you got a "dwarf2 unwinder stuck"
______________________________________________________________________
-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://git.onelab.eu / linux-2.6.git / blobdiff