Two hadoop nodes on same machine while a second machine not joining the cluster

Question

I have a test cluster of two machines, on both of them hadoop is installed. I've configured the hadoop cluster but on admin UI (as in the below picture) I see that two nodes are running on the same master machine, and that the other machine has no Hadoop node.

On master machine following services are running:

~$ jps
26310 ResourceManager
27593 Jps
26216 DataNode
26135 NameNode
26557 NodeManager
26701 JobHistoryServer

On the slave machine:

~$ jps
2614 DataNode
2920 Jps
2707 NodeManager

I don't why the slave is not joining the cluster (It was before). I tried to shutdown all servers on both machines and format HDFS then restarting everything but that didn't help. Any help to figure what's causing that behavior is appreciated.

Answer 1

Fixed, the two machines had same hostname! So I just renamed the slave.