How to install VirtualBox Guest Additions on Linux
Q. How can I install VirtualBox Guest Additions on Linux
A. If you have VirtualBox installed, and you have a Linux Guest OS, Ubuntu for this example, you can install VirtualBox Guest additions really easy, that will help you in may ways, but maybe the most important one is that you will be able to run your Guest OS, Ubuntu in this case in full screen having it using your complete screen space.
The first thing you need to do, is to insert the CD with the Guest Additions, it is a virtual CD, and all you have to do is to the VirtualBox menu Devices -> Insert Guest Additions CD Image
Then you need to mount the CD into Ubuntu, to do that run this command:
sudo mount /dev/cdrom /mnt
You will be asked to enter your password, do it, and hit ENTER, after that, install the requiered software to compile the needed software.
sudo apt-get update && sudo apt-get install build-essential dkms linux-headers-$(uname -r)
Finally, install the Guest Additions.
cd /mnt sudo ./VBoxLinuxAdditions.run
It will take some time, and when it finishes, just restart your guest OS, and you will have all installed, now you can go full screen and enjoy your Ubuntu guest OS in all the screen.