http://vjetnamnet.com/how-to-change-the-hostname-on-linux-centos-6-3-server/
Check current hostname with this command :
# hostname --fqd
centos62.ehowstuff.local
1. Modify /etc/sysconfig/network
# nano /etc/sysconfig/network
2. Edit to your preferred hostname :
NETWORKING=yes
HOSTNAME=server.vjetnamnet.local
3. Modify /etc/hosts file as below :
# nano /etc/hosts
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.1.44 server.vjetnamnet.local server
4. Save and reboot your server.