By default, your server is started with the server’s given name as the hostname. This article describes how to change a server hostname in CentOS.
Using a text editor, open the server’s /etc/sysconfig/network file.
# cd /etc/sysconfig
# vi network
HOSTNAME= value to match your FQDN hostname.
For internal networking, change the host that is associated with the main IP address for your server (found at /etc/hosts).
127.0.0.1 localhost localhost.localdomain
184.108.40.206 hostname.domain.com hostname
-- INSERT -- 2,43-57 ALL
hostname command. This command lets you change the hostname on the server that the command line remembers, but it does not actively update all programs that are running under the old hostname.
[root@defiant ~]# hostname hostname.domain.com
[root@defiant ~]# hostname
Restart networking on your server to ensure that changes will persist on restart.
# /etc/init.d/network restart