[ale] linux kernel tuneables ?

[Chris Ricker]

On Wed, 19 Dec 2001, Gene Matthews wrote:

> I am trying to figure out where I can tune certain things under linux. 
> Solaris has the /etc/system file where you set values for some kernel 
> parms that are pickep up at boot time.  I haven't found (yet) anything 
> similar, although I'm still looking.
> 
> Can anyone point me in the right direction?

Linux has two interfaces to the exact same kernel parameters, a BSD-sytle
sysctl(8) and /proc/sys.

sysctl is a command to modify parameters.  It can be run directly with the
parameter to modify (similar to using adb / mdb on the running kernel in
Solaris), but more typically the parameters are listed in /etc/sysctl.conf
(similar to /etc/system).  sysctl -p will apply that file.

/proc/sys contains files representing the tunable parameters.  Values are 
read by catting the files, and are changed by echoing new values into the 
files.

The same parameters are available through either interface.  It's just a 
matter of which syntax you prefer.  For example,

sysctl -w kernel.sysrq=1

and 

echo "1" > /proc/sys/kernel/sysrq

both do the same thing -- enable the Magic SysRequest key.

The files in
/usr/src/linux/Documentation/{networking/ip-sysctl.txt,sysctl/*} document
all the available parameters.

later,
chris


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