Where could I find the ifcfg-eth0 file?

You could find an example in /usr/share/doc*/initscript*, can't remember the exact name, but I'll provide a comprehensive example here:

All fields are fairly easy to understand

DEVICE=eth0 
BOOTPROTO=none 
ONBOOT=yes 
NETWORK=10.0.1.0 
NETMASK=255.255.255.0 
IPADDR=10.0.1.27 

Docs here