In most UNIX-variant operating systems, all DNS server entries will be in a configuration file /etc/resolv.conf. The resolv.conf configuration file will have entries for each DNS server which stores alpha-numeric name to numeric IP address mapping. For example, an entry "nameserver 1.2.3.4" in resolv.conf indicates that the DNS server to be accessed for all name-to-IP address mapping is 1.2.3.4 To add a new DNS server entry, append resolv.conf with new DNS server entry in the format "nameserver ". Example to add DNS server 5.6.7.8: nameserver 5.6.7.8 For the just added entry to be effective, it requires restarting network services. Run #/etc/netstart