Hadoop--WARN hdfs.DFSClient: DataStreamer Exception org.apache.hadoop.ipc.RemoteException

 WARN hdfs.DFSClient: DataStreamer Exception
org.apache.hadoop.ipc.RemoteException(java.io.IOException): File /user/mhw/input/wc.input._COPYING_ could only be replicated to 0 nodes instead of minReplication (=1).  There are 0 datanode(s) running and no node(s) are excluded in this operation.

报错是由于datanode未启动造成的.

先用jps查看namenode与datanode是否都启动 , 若是有未启动的则先启动.