I was able to execute this and other commands;
hadoop fs -ls hdfs://101-master:50000
I rebooted my cloud instances from OpenStack horizon web interface and started getting this exception for no reason. I did not make any changes to the configuration:
Call From 101-master/192.168.0.18 to 101-master:50000 failed on connection exception: java.net.ConnectException: Connection refused; For more details see: http://wiki.apache.org/hadoop/ConnectionRefused
what is the reason for this exception.