JAVA _Home is not set in Hadoop

Question

I am a beginner with hadoop and trying to install and run hadoop in my Ubuntu as a single node cluster. This is my JAVA_HOME in my hadoop_env.sh

# The java          


        

Answer 1

I'm using hadoop 2.8.0. Even though I exported JAVA_HOME (I put it in .bashrc), I still caught this error while trying to run start-dfs.sh.

user@host:/opt/hadoop-2.8.0 $ echo $JAVA_HOME
<path_to_java>
user@host:/opt/hadoop-2.8.0 $ $JAVA_HOME/bin/java -version
java version "1.8.0_65"
...
user@host:/opt/hadoop-2.8.0 $ sbin/start-dfs.sh
...
Starting namenodes on []
localhost: Error: JAVA_HOME is not set and could not be found.
localhost: Error: JAVA_HOME is not set and could not be found.

The only way I could get it to run was to add JAVA_HOME=path_to_java to etc/hadoop/hadoop-env.sh and then source it:

:/opt/hadoop-2.8.0 $ grep JAVA_HOME etc/hadoop/hadoop-env.sh
#export JAVA_HOME=${JAVA_HOME}
export JAVA_HOME=path_to_java
user@host:/opt/hadoop-2.8.0 $ source etc/hadoop/hadoop-env.sh

Maybe that (sourcing hadoop-env.sh) was implied in the posts above. Just thought someone should say it out loud. Now it runs. I've encountered other issues (due, I suspect, to the limited resources on the server I'm using), but at least I got past this one.

Answer 2

Under your HADOOP_HOME/conf directory please update the hadoop-env.sh file. It has entry to export JAVA_HOME.

Setting to appropriate JAVA_HOME in this file should solve your issue.