Linux: Set Fully Qualified Hostname

On a linux system you may find your hostname is just set tot the computer name e.g.
SVR001

The problem is that this is not a valid fully qualified domain name.

To set a FQDM:

1. Edit the hostname file:
   vi /etc/hostname
   vi /etc/hosts
2. Add a suffix to your computer name e.g.
   SVR001.example.com
3. Restart the hostname service:
   Ubuntu: service hostname restart
   /etc/init.d/hostname.sh start
   CentOS: systemctl restart systemd-hostnamed