Update ruby version on Ubuntu nginx.

> rvm install ruby-2.1.8

> rvm use 2.1.8@xan --create

and

> gem install bundler

Edit nginx.cof

> sudo vi /opt/nginx/conf/nginx.conf

server{

......

   passenger_ruby /home/ubuntu/.rvm/gems/ruby-2.1.8/wrappers/ruby;

   passenger_enabled on;

   rails_env staging;

......

}

restart nginx.