Safe Mode in Big Data Hadoop

Safe Mode in Hadoop is a maintenance state of the NameNode during which NameNode doesn’t allow any changes to the file system. During Safe Mode, HDFS cluster is read-only and doesn’t replicate or delete blocks.

status of safe mode: hdfs dfsadmin -safemode get

Enter safe mode: hdfs dfsadmin -safemode enter

Exit safe mode: hdfs dfsadmin -safemode leave