In order to set up Google public DNS to your Linux settings place the following root@ptubuntu-laptop:/home/ptubuntu# vi /etc/resolv.conf:

nameserver 8.8.8.8
nameserver 8.8.4.4

root@ptubuntu-laptop:/home/ptubuntu# dig @8.8.8.8 ptubuntu.com

; <<>> DiG 9.6.1-P1 <<>> @8.8.8.8 ptubuntu.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 23748
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;ptubuntu.com.            IN    A

;; ANSWER SECTION:
ptubuntu.com.        1713    IN    A    174.120.9.66

;; Query time: 75 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Fri Dec  4 10:23:32 2009
;; MSG SIZE  rcvd: 46