you can try to manually add the lines in the configuration files. For DHCP to work on interface you need to open /etc/network/interfaces file and if your interface is eth0 then it should look like this:
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface
iface lo inet loopback
# The primary network interface
iface eth0 inet dhcp
DNS records are in /etc/resolv.conf file. If you know IP of your DNS server you can manualy add it to this file. For example:
I have two DNS servers at my home, that's why there are two IP addresses listed. Just change ip address to your DNS server.
After all changes are done you need to restart the network with:
sudo /etc/init.d/networking restart
Hope it helps