Update 28 July 2019: An updated version of this guide for Ubuntu Server 18.04 LTS is now available. Feel free to check it out.
Update 23 May 2020: This guide is ALREADY OUTDATED and might no longer work with new versions of Ubuntu and VirtualBox. Please consider switching to the updated guide instead. I will no longer respond to the replies to this gist. Thank you.
Mounting VirtualBox shared folders on Ubuntu Server 16.04 LTS
This guide will walk you through steps on how to setup a VirtualBox shared folder inside your Ubuntu Server guest. Tested on Ubuntu Server 16.04.3 LTS (Xenial Xerus)