MapR 5.0 Documentation : DNS Resolution

For MapR to work properly, all nodes on the cluster must be able to communicate with each other. Each node must have a unique hostname, and must be able to resolve all other hosts with both normal and reverse DNS name lookup.

You can use the hostname command on each node to check the hostname. Example:

$ hostname -f
swarm

If the command returns a hostname, you can use the getent command to check whether the hostname exists in the hosts database. The getent command should return a valid IP address on the local network, associated with a fully-qualified domain name for the host. Example:

$ getent hosts `hostname`
10.250.1.53     swarm.corp.example.com

If you do not get the expected output from the hostname command or the getent command, correct the host and DNS settings on the node. A common problem is an incorrect loopback entry (127.0.x.x), which prevents the correct IP address from being assigned to the hostname.