Hadoop UI shows only one Datanode

Question

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 -rep

Answer 1

Sorry, feels like it's been a time. But still I'd like to share my answer: the root cause is from hadoop/etc/hadoop/hdfs-site.xml: the xml file has a property named dfs.datanode.data.dir. If you set all the datanodes with the same name, then hadoop is assuming the cluster has only one datanode. So the proper way of doing it is naming every datanode with a unique name:

Regards, YUN HANXUAN