1. Format and Start HDFS

Execute these commands on the NameNode:

Login as $HDFS_USER
/usr/lib/hadoop/bin/hadoop namenode -format
/usr/lib/hadoop/bin/hadoop-daemon.sh --config $HADOOP_CONF_DIR start namenode

Execute these commands on the Secondary NameNode :

Login as $HDFS_USER
/usr/lib/hadoop/bin/hadoop-daemon.sh --config $HADOOP_CONF_DIR start secondarynamenode

Execute these commands on all DataNodes:

Login as $HDFS_USER
/usr/lib/hadoop/bin/hadoop-daemon.sh --config $HADOOP_CONF_DIR start datanode