sudo apt-get install openssh-server openssh-client

ssh-keygen -t rsa
cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys

chmod 700 /home/hadoop/.ssh
chmod 600 /home/hadoop/.ssh/authorized_keys

scp /home/hadoop/.ssh/id_rsa.pub hadoop@slave:/home/hadoop

cat ~/id_rsa.pub >> ~/.ssh/authorized_keys

ssh slave

Welcome to Ubuntu 12.04.1 LTS (GNU/Linux 3.2.0-29-generic-pae i686)
* Documentation: https://help.ubuntu.com/
411 packages can be updated.
137 updates are security updates.
Last login: Sun May 5 11:14:09 2013 from master

export JAVA_HOME=/usr/lib/jvm/jdk1.6.0_35
export JRE_HOME=${JAVA_HOME}/jre
export PATH=${JAVA_HOME}/bin:${JRE_HOME}/bin:${PATH}
export CLASSPATH=${CLASSPATH}:${JAVA_HOME}/lib:${JRE_HOME}/lib

export JAVA_HOME=/usr/lib/jvm/jdk1.6.0_35

scp -r home/hadoop/hadoop-1.2.1/ hadoop@slave:/home/hadoop