On Thu, Nov 5, 2009 at 4:04 AM,  <Richard dot MANAS at unice dot fr> wrote:
> Thanks for you answer.
> My hardware is a pentium IV with 512 mB of RAM
> More than 200 students are connected.
>
> I set only "Captive portal" and syslog is enable on a remote server
>
> Before I reboot, I saw that memory  was only 15% busy
> and logs said "file system full"
>

The file system that's full is RAM, it's running from RAM disk. If you
have a very large DHCP leases file it will fill up the memory disk.
Your only option may be to switch to using some other system as a DHCP
server.