Change hostname in Linux

First you need to find out your hostname, you can do this with

$ hostname
localhost.localdomain
$

Edit /etc/hosts

You need to edit /etc/hosts and add a line for your host name

$ cat /etc/hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1               localhost.localdomain localhost
$

My new server IP is 72.232.196.90, i need to assign it hostname server12.hosthat.com, to do this, i have edited /etc/hosts as follows.

# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1               localhost.localdomain localhost
72.232.196.90           server12.hosthat.com server12

Edit /etc/sysconfig/network

First lets see what is in the file

$ cat /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=localhost.localdomain
$

To change servers hostname to server12.hosthat.com, change the file as follows.

$ cat /etc/sysconfig/network
NETWORKING=yes
HOSTNAME=server12.hosthat.com
$

Now you need to reboot the server to change the hostname.