Create hadoop-env.sh

Administrators should use the conf/hadoop-env.sh script to do site-specific customization of the Hadoop daemons' process environment.

At the very least you should specify the JAVA_HOME so that it is correctly defined on each remote node.

In most cases you should also specify HADOOP_PID_DIR to point a directory that can only be written to by the users that are going to run the hadoop daemons. Otherwise there is the potential for a symlink attack.