set Domain in CentOS/RHEL/OEL 6

/etc/sysconfig/network
NETWORKING=yes
HOSTNAME=MDS-NOD-01
DOMAIN=milliondollarserver.com

# /etc/hosts

127.0.0.1   MDS-NOD-01.milliondollarserver.com MDS-NOD-01 localhost localhost.localdomain localhost4 localhost4.localdomain4

testing:

# hostname
# hostname -f