Using a text editor, open the hosts file on every host in your cluster. For example:
vi /etc/hosts
Add a line for each host in your cluster. The line should consist of the IP address and the FQDN. For example:
1.2.3.4 <fully.qualified.domain.name>
Do
not
remove the following two lines from your hosts file. Removing or editing the following lines may cause various programs that require network functionality to fail.127.0.0.1 localhost.localdomain localhost
::1 localhost6.localdomain6 localhost6