virtualbox in full screen code example
Example 1: virtualbox fullscreen resolution
sudo apt-get install virtualbox-guest-dkms
sudo dpkg-reconfigure virtualbox-guest-dkmsExample 2: virtualbox fullscreen resolution
Go to the VirtualBox options while in your VM (the same place you went to to install Guest Additions) and select View -> Auto-resize Guest Display. This should automatically set your VM's resolution to the proper screen size.