ping: unknown host google.com in UBUNTU SERVER [duplicate]

If you're using a static IP you should also add DNS servers.

1. Edit /etc/network/interfaces:

   sudo nano /etc/network/interfaces
   

2. Below iface eth0 inet static add the following line:

   dns-nameservers 8.8.8.8 8.8.4.4
   

   This will use Google's DNS servers.

3. Restart your network:

   sudo /etc/init.d/networking restart
   

Note: as chaos says, you can also edit /etc/resolv.conf but these changes will be overwritten on reobot.

Note2: Sometimes sudo /etc/init.d/networking restart is not enough, but a full reboot helps.

Create a file called /etc/resolv.conf write fill in the contents:

nameserver <ip-of-your-nameserver>

For example if your want to use googles dns-service:

nameserver 8.8.8.8
nameserver 8.8.4.4