How to change hostname or FQDN in CentOS and Redhat

In this tutorial we will learn about,how to change Hostname or FQDN in CentOS and Red Hat.
The method is applicable to all Red Hat based operating system. I have described about difference between hostname and FQDN which you can read from this post (The post is written on how to change hostname in Ubuntu,read the theory).

Step 1: Edit the /etc/hosts file and give IP Address,FQDN name and Server name

 #vi /etc/hosts
        ipaddress_of_system server1.sharadchhetri.com server1 

Step 2: Edit /etc/sysconfig/network file ,give HOSTNAME as machine name i.e server1

         # vi /etc/sysconfig/network
         NETWORKING=yes
         HOSTNAME=server1
       

Step 3: Restart the network service.

         /etc/init.d/network restart

         

Now check the hostname and FQDN with command called hostname and hostname -f respectively.

#hostname
 server1
#hostname -f
 server1.sharadchhetri.com

Note: There is another method through which you can change the hostname but generally it is not so much preferable.

The command is

sysctl kernel.hostname                      (It will show the current hostname)
sysctle kernem.hostname Give_hostname        (It will set the hostname)