Use-case: run Hadoop with localhost as your only master/slave and with a custom JVM:

echo JAVA_HOME=/home/user/jdk > ~/.bashrc
echo JAVA_HOME=/home/user/jdk > ~/.ssh/environment
sudo -i
echo PermitUserEnvironment yes >> /etc/ssh/sshd_config
service ssh restart
exit
ssh localhost ‘echo $JAVA_HOME’