# Install nodejs
apt-get install nodejs
# install node package manager
apt-get install npm
# Install forever module 
npm -g install forever
ln -s /usr/bin/nodejs /usr/bin/node
# Run nodejs application forever
forever start index.js
forever stop index.js

# one more way
npm install -g pm2
pm2 start index.js

# Generate start up script for pm2
pm2 startup ubuntu

run the last commd generated from above command.

On Mac
brew install node