Format and Start HDFS

Modify the JAVA_HOME value in the hadoop-env.sh file:
```
export JAVA_HOME=/usr/java/default
```

Execute the following commands on the NameNode host machine:

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

Execute the following commands on the SecondaryNameNode:

su - $HDFS_USER
/usr/hdp/current/hadoop-hdfs-secondarynamenode/../hadoop/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR start secondarynamenode

Execute the following commands on all DataNodes:
```
su - $HDFS_USER
/usr/hdp/current/hadoop-hdfs-datanode/../hadoop/sbin/hadoop-daemon.sh --config $HADOOP_CONF_DIR start datanode
```
Where $HADOOP_CONF_DIR is the directory for storing the Hadoop configuration files. For example, /etc/hadoop/conf.
Where $HDFS_USER is the HDFS user, for example, hdfs.

​Format and Start HDFS