Error: Could not find or load main classorg.apache.hadoop.hdfs.server.namenode.NameNode

Error: Could not find or load main class org.apache.hadoop.hdfs.server.namenode.NameNode

This error "Error: Could not find or load main class org.apache.hadoop.hdfs.server.namenode.NameNode" can be seen When you try to execute the below command.

$ bin/hdfs namenode -format

The most common reason for this is the HADOOP_PREFIX environment variable is not set or to the correct path atleast.To set the path to the current session execute the following or set it in the profile permanently:

$ export HADOOP_PREFIX=/path_to_hadoop_location

For example,

$ export HADOOP_PREFIX= /u01/bigdata/hadoop

Once the value is set and running the command again the following start up messages should be seen.

-bash-4.2$ bin/hdfs namenode -format

15/10/20 14:13:07 INFO namenode.NameNode: STARTUP_MSG:

/************************************************************

STARTUP_MSG: Starting NameNode

STARTUP_MSG:   host = localhost/10.xx.xx.xx

STARTUP_MSG:   args = [-format]

STARTUP_MSG:   version = 2.6.1

STARTUP_MSG:   classpath = /u01/bigdata/hadoop/etc/hadoop:/u01/bigdata/hadoop/share/hadoop/common/

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