Two files need to be updated to change host name in Linux. Perform the changes as root user.
1. Update file:
# vi /etc/sysconfig/network
Change the value of HOSTNAME according to your need.
2. Update the file:
If you have static IP then add as below:
127.0.0.1 localhost localhost.localdomain
192.168.0.20 mars hostname
3. Restart networking in server to apply changes: