Hostname is to display the current host, domain or node name of the system. These names are used by many of the networking programs to identify the machine. The domain name is also used by NIS/YP. It should be a FQDN (Fully Qualified Domain Name).
Login to your server via SSH & set a hostname with command “hostname”
# hostname server.domain.com
Open the file /etc/sysconfig/network and set the hostname in this file. Save the file and quit.
Doing this, hostname for your server is set.