cp /etc/dhcp/dhclient.conf /etc/dhcp/dhclient.conf.orig
echo -e "\n# Using OpenDNS as your default DNS - http://www.opendns.org" >> /etc/dhcp/dhclient.conf
echo "prepend domain-name-servers 208.67.222.222,208.67.220.220;" >> /etc/dhcp/dhclient.conf
ifdown eth0 && ifup eth0
Pay attention to "Privacy issues, conflicts and Google redirection" on the wikipediapage .