To check the host name use the below command
#hostname
This will display the host name if already set
To Change the host name temporarly use the below command
#hostname NEW-NAME
To make the changes permanent we need to edit two files
1)Network File
2)/etc/hosts file
1)Redhat / CentOS / Fedora: Change Hostname
vi /etc/sysconfig/network
HOSTNAME=NEW-NAME
Set only the host name not the domain name extension
2)vi /etc/hostname
Enter the ipaddress followed by host name without domain extension after a space
192.168.0.1 NEW-NAME