Configure each host in the cluster as follows to ensure that all members can communicate with each other:

1. Set the hostname to a unique name (not localhost).

   sudo hostnamectl set-hostname foo-1.example.com

2. Edit /etc/hosts with the IP address and fully qualified domain name (FQDN) of each host in the cluster. You can add the unqualified name as well.

   1.1.1.1  foo-1.example.com  foo-1
   2.2.2.2  foo-2.example.com  foo-2
   3.3.3.3  foo-3.example.com  foo-3
   4.4.4.4  foo-4.example.com  foo-4

   Important:
   • The canonical name of each host in /etc/hostsmust be the FQDN (for example myhost-1.mynet.myco.com), not the unqualified hostname (for example myhost-1). The canonical name is the first entry after the IP address.
   • Do not use aliases, either in /etc/hosts or in configuring DNS.
3. Edit /etc/sysconfig/network with the FQDN of this host only:

   HOSTNAME=foo-1.example.com

4. Verify that each host consistently identifies to the network:
   1. Run uname -a and check that the hostname matches the output of the hostname command.