How to expand a VDI disk image on a Macintosh computer: http://mithunme.wordpress.com/2013/07/08/how-to-increase-the-disk-size-of-a-ubuntu-vdi-on-mac/. This would also be applicable to a Linux machine. A very useful tip.
How to add a standard user to the /etc/sudoers file on a Macintosh computer: http://mithunme.wordpress.com/2013/02/10/adding-a-standard-user-to-etcsudoers-in-mac-os-x/. This is also applicable to a Linux machine.