Re: Problems raising fd limits in 1.3.78-1.3.80

Stephen C. Tweedie (
Sun, 7 Apr 1996 22:54:01 +0100


On Wed, 3 Apr 1996 12:31:36 -0500 (EST), Roman Gollent
<> said:

> ... How much of a rewrite is required to be able to dynamically
> reconfigure certain kernel variables without recompilation?

None. Look in /proc/sys, and you'll find an interface to many kernel
tuning parameters, which includes write access where appropriate.
There is a corresponding sysctl() system call to give applications
more efficient, binary access to the same data without having to rely
on /proc (which might not be available, eg. during the boot process
before all filesystems are mounted).

The sysctl handling is all table driven, so adding new parameters
requires no extra coding. See linux/kernel/sysctl.c.

> I'm thinking of an /etc/sysconfigtab (Digital Unix) equivalent where
> one can edit the parameters, reboot the system and have them take
> effect.

This might be useful --- it would not be too hard to write a program
to parse /etc/sysconfigtab and perform the appropriate kernel configs
at run time. A reboot would not be required for the new settings to
take effect.


Stephen Tweedie <>
Department of Computer Science, Edinburgh University, Scotland.