I've started hadoop cluster composed of on master and 4 slave nodes.

Configuration seems ok:

[hduser@ubuntu-amd64:/usr/local/hadoop$ ./bin/hdfs dfsadmin -report](http://pastebin.com/6QfgKMmk)

When I enter NameNode UI (`http://10.20.0.140:50070/`) `Overview` card seems ok - for example total Capacity of all Nodes sumes up.

[![enter image description here](https://i.stack.imgur.com/wnJOg.png)](https://i.stack.imgur.com/wnJOg.png)

The problem is that in the card `Datanodes` I see only one datanode.

[![Datanode card](https://i.stack.imgur.com/JjyDZ.png)](https://i.stack.imgur.com/JjyDZ.png)