shared folders

Transferring files from the host to the guest OS and vice-versa doesn't work out-of-the-box when you install VirtualBox from the Ubuntu repositories and download an Ubuntu VirtualBox image (e.g. from http://www.osboxes.org/virtualbox-images). After installing the guest additions, drag-and-drop didn't seem to work for me and I needed to set up a "Shared Folder". After setting it up via the GUI, it doesn't automatically appear on the guest desktop. You need to mount it: