can i use codeigniter with nginx?

Yes, you can use CI over nginx (Engine X). CI is basically a PHP based framework. So, you need a web server to handle your request and responses and run your codes. A web server may be apache, nginx, IIS or PHP inbuilt web server.

If you want to install and setup nginx on Ubuntu. You can refer to http://getweblessons.com/install-configu...ntu-14-04/.

Let me know if you need any more help.

Nitin