The networking configuration and eth0 is configured in the file /etc/network/interfaces file.If the system is set up to use dhcp, then the /etc/network/interfaces would contain:
iface eth0 inet dhcp
To change the system to use a static IP address, change the /etc/network/interfaces file to:
iface eth0 inet static
address 192.168.1.1
netmask 255.255.255.0
gateway 192.168.1.254
