[CentOS] install via http

>
> The CentOS DVD images (not sure about CD images) have an images 
> directory that contains a boot.iso file that can be used to net boot 
> machines.  That's the one I used.
>
> Together with a combination of autofs, lighttpd, rsync'ing and cron I 
> am able to fully support a lab of about 500 machines and a small 
> cluster using just 10 boot CDs and some kickstart files, boot and 
> update the machines in about an hour.  Including system customization, 
> also done through shell scripts.
>

have you had a look at cobbler and koan? They will do all this for you 
automagically