Working With Hadoop: localhost: Error: JAVA_HOME is not set

Question

I\'m working with Ubuntu 12.04 LTS.

I\'m going through the hadoop quickstart manual to make a pseudo-distributed operation. It seems simple and straightforward (eas

Answer 1

Ran into the same issue on ubuntu LTS 16.04. Running bash -vx ./bin/hadoop showed it tested whether java was a directory. So I changed JAVA_HOME to a folder and it worked.

++ [[ ! -d /usr/bin/java ]]
++ hadoop_error 'ERROR: JAVA_HOME /usr/bin/java does not exist.'
++ echo 'ERROR: JAVA_HOME /usr/bin/java does not exist.'
ERROR: JAVA_HOME /usr/bin/java does not exist.

So I changed JAVA_HOME in ./etc/hadoop/hadoop-env.sh to

export JAVA_HOME=/usr/lib/jvm/java-8-oracle/jre/

and hadoop starts fine. This is also mentioned in this article.

Answer 2

Check if your alternatives is pointing to the right one, you might actually be pointing to a different version and trying to alter the hadoop-env.sh on another installed version.

-alternatives --install /etc/hadoop/conf [generic_name] [your correct path] priority {for further check man page of alternatives}

to set alternatives manually,

alternatives --set [generic name] [your current path].

Answer 3

The way to debug this is to put an "echo $JAVA_HOME" in start-all.sh. Are you running your hadoop environment under a different username, or as yourself? If the former, it's very likely that the JAVA_HOME environment variable is not set for that user.

The other potential problem is that you have specified JAVA_HOME incorrectly, and the value that you have provided doesn't point to a JDK/JRE. Note that "which java" and "java -version" will both work, even if JAVA_HOME is set incorrectly.

Answer 4

The way to solve this problem is to export the JAVA_HOME variable inside the conf/hadoop-env.sh file.

It doesn't matter if you already exported that variable in ~/.bashrc, it'll still show the error.

So edit conf/hadoop-env.sh and uncomment the line "export JAVA_HOME" and add a proper filesystem path to it, i.e. the path to your Java JDK.

# The Java implementation to use. Required.
export JAVA_HOME="/path/to/java/JDK/"

Answer 5

regardless of debian or any linux flavor, just know that ~/.bash_profile belongs to specific user and is not system wide. in pseudo-distributed environment hadoop works on localhost so the $JAVA_HOME in .bash_profile is no use anymore.

just export the JAVA_HOME in ~/.bashrc and use it system wide.