1. Format and Start HDFS

Execute these commands on the NameNode host machine:

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

Execute these commands on the SecondaryNameNode:

su $HDFS_USER
/usr/lib/hadoop/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR start secondarynamenode

Execute these commands on all DataNodes:

su $HDFS_USER
/usr/lib/hadoop/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR start datanode

where:

$HDFS_USER is the user owning the HDFS services. For example, hdfs.
$HADOOP_CONF_DIR is the directory for storing the Hadoop configuration files. For example, /etc/hadoop/conf.