2.2. Linux full-screen
After installation of Ubuntu we have a fixed resolution of the desktop, without the possibility of changing the size when VBox maximized window. To solve this problem have the Guest Additions VirtualBox, which allows the guest machine's desktop to maximize the window size VirtualBox on the host machine.

Ubuntu in VirtualBox

Install Guest Additions
VBox accessing the menu Devices -> Install Guest Additions be installed virtual CD VBOXADDITIONS scripts. From Ubuntu to access places -> VBOXADDITIONS_3.2.12_68302 to mount the virtual CD.

Mount the Guest Additions
Inside VBOXADDITIONS find the scripts for different operating systems, is appropriate for running the Linux operating system, in our case is VBoxLinuxAdditions-x86.run.
Probably an error in the execution of the script, this is because it needs administrator privileges, close the current session and start a new one with the root, now will install without problems. These steps are completed, restart the Ubuntu virtual machine and we can resize the window, the Gnome desktop will adapt to its size.

Run the script of Guest Additions for Linux distribution