1. First change all app old name to new name under app folder.
2. Then change web server config under web server config file, like sudo vi /opt/nginx/conf/nginx.conf
3. change database name
3.1 change database name in your database system, like mysql
3.2 use rake db:reset to drop old and create new.
4. restart your nginx with
/etc/init.d/nginx stop
/etc/init.d/nginx start