Virtual Box is extensively used as our development environment.   This allows easy re-creation of development boxes when needed.   We have a few versions which we re-create and drop every so often as part of the development and testing work.  Recently, we created a virtual box environment with a fresh iDempiere 6.2 installation.

As part of the virtual box installation, I would normally share my external drive with my Ubuntu guest O/S.

This would normally work.  However, there are a few times that the Ubuntu guest O/S fails to link to the external folder.  This can happen when your user is not part of the vboxsf group.  To fix this issue, we would issue the following command to allow my user to access the external folder:   sudo adduser <user> vboxsf .   At times, we will also reboot the system to make this work.  Hope this helps!