I recently install Ubuntu 14.04 into a Oracle’s VirtualBox. This went fine, but I was unable to get the desktop to resize to my host machines.
I selected “Devices >> install guesst additions”. It installed and I restarted, but still nothing. I tried manual ways and bunch of stuff, but nothing worked till I ran this command in terminal.
sudo apt-get install virtualbox-guest-dkms
Restarted the virtual machine and everything worked.
This link helped me.
I hope this helps someone else.