Edit this file:

/etc/hostname

Then run this command:

/etc/init.d/hostname.sh start

Verify that the name is changed with some of these commands:

uname -n
hostname -a
hostname -s
hostname -d
hostname -f
hostname

For more infomation, see:

“How to change the hostname of a Linux system”
http://www.ducea.com/2006/08/07/
    how-to-change-the-hostname-of-a-linux-system/

“Change hostname or Server name of a Linux Machine”
http://www.debianadmin.com/
    change-hostname-or-server-name-of-a-linux-machine.html