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 (easy!).

However, when I try to run start-all.sh I get:

localhost: Error: JAVA_HOME is not set. 

I've read all the other advice on stackoverflow for this issue and have done the following to ensure JAVA_HOME is set:

In /etc/hadoop/conf/hadoop-env.sh I have set

JAVA_HOME=/usr/lib/jvm/java-6-oracle export JAVA_HOME 

In /etc/bash.bashrc I have set

JAVA_HOME=/usr/lib/jvm/java-6-oracle export JAVA_HOME PATH=$PATH:$JAVA_HOME/bin export PATH 

which java returns:

/usr/bin/java 

java –version works

echo $JAVA_HOME returns:

/usr/lib/jvm/java-6-oracle 

I've even tried becoming root and explicitly writing the in the terminal:

$ JAVA_HOME=/usr/lib/jvm/java-6-oracle $ export JAVA_HOME $ start-all.sh 

If you could show me how to resolve this error it would be greatly appreciated. I'm thinking that my JAVA_HOME is being overridden somehow. If that is the case, could you explain to me how to make my exports global?

Answer 1

I am using hadoop 1.1, and faced the same problem.

I got it solved through changing JAVA_HOME variable in /etc/hadoop/hadoop-env.sh as:

export JAVA_HOME=/usr/lib/jvm/<jdk folder> 

Answer 2

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/"