There are several ways to change the hostname on Red Hat or a Red Hat clone:

• Use hostname (no network service restart required).
  Type hostname followed by the machine name. For example, to change it to hostname.example.com:
  #hostname hostname.example.com

• Use system-config-network (network service restart required).

• Edit /etc/sysconfig/network (network service restart required).
  Edit HOSTNAME. For example, to change the hostname to hostname.example.com:

cat /etc/sysconfig/network

NETWORKING=yes
HOSTNAME=hostname.example.com