How to Change the hostname or computer name in ubuntu

This is a really simple one, but can cause a lot of weeping and gnashing of teeth. You were given the default “ubuntu” hostname when you installed, and now you want something cooler that enhances your street cred. Heres how to change it:

Edit /etc/hostname and change to the new value, you can use nano instead of vi, but remember that real men prefer vi.

vi /etc/hostname

Edit /etc/hosts and change the old 127.0.1.1 line to your new hostname (if you dont do this, you wont be able to use sudo anymore. If you hav e already done it, press ESC on the grub menu, choose recovery, and edit your host file to the correct settings)

127.0.0.1   localhost
127.0.1.1   ubuntu.local    ubuntu   # change to your new hostname/fqdn

Now after a reboot, your hostname will be the new one you chose. To change without a reboot, you can just use hostname.sh after you edit /etc/hostname:

sudo /etc/init.d/hostname.sh start

Thanks to  http://techgurulive.com/2008/11/12/how-to-change-the-hostname-or-computer-name-in-ubuntu/