[Yum] How to update a system using a cdrom

[Francois Massonneau]

Hi,

i've just bought a cd-rom containing updated packages for Redhat9.0
It's structure is :
athlon
i386
i486
etc...
noarch
SRPMS
it is mounted on /mnt/cdrom.

I would like to ask yum to check that cdrom to update the packages 
installed on the machine. First, is it possible ?

If so, I've added to the yum.conf file the following lines :
[local]
name=LocalStuff
baseurl=file:///mnt/cdrom/$basearch

But yum doesn't like that, and complains about the header.info file 
missing.

Is it possible to do what I describe above ? Thanks. Francois