ipc.Client: Retrying connect to server: localhost/127.0.0.1:9000. Already tried 0 time(s); retry policy is

15/05/08 01:26:12 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:9000. Already tried 0 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS)
...
Bad connection to FS. command aborted. exception: Call to localhost/127.0.0.1:9000 failed on connection exception: java.net.ConnectException: Connection refused


solution : run "bin/hadoop namenode -format" command