If you are running DHCP client then you can put static nameserver in either /etc/dhcp3/dhclient.conf or /etc/resolvconf/resolv.conf.d/base (follow the static address instructions below). If you use /etc/dhcp3/dhclient.conf then the changes will not persist if you switch to a static IP or another interface. In other words, the static nameservers in dhclient.conf will only appear when using DHCP. See DHCP for information on going that route.

If you are using Static IP

If you have a static address and your resolv.conf is lost on reboot then you need to create a file:

/etc/resolvconf/resolv.conf.d/base

Add the nameserver lines that you want to always be included in your resolv.conf file. Then after no matter what service causes resolv.conf to be regenerated you can be sure it will contain these nameserver lines. For example, you might put the following in “base” to use OpenDNS:

nameserver 208.67.222.222
nameserver 208.67.220.220

Do a man on “resolvconf”. This is not the same man page as “resolv.conf”.

source :

http://www.noah.org/wiki/Resolv.conf