I was working on this project where the task was to add some code for the test automation of the product. The whole system was on linux, so I had to prepare all the system on ubuntu. I set up an ubuntu instance on the virtualbox-4.3.12. The problem was that the size of the screen was static where it had scroll bars and so it was uncool. I also use virtualbox in my work with redhat as guest os, but there, the screen size of guest machine dynamically changes as I resize the virtual-box window.
So I thought, there must be some way to do this in ubuntu as well. I researched and found an amazingly simple solution. In the window where the guest OS is running, there is an option Devices->Install guest additions CD image. Click on the link and install the image in the guest os. Now restart it. That should do the work.
However in my case, the virtual box started to crash and could not open. I tried different things but it didnot work. Finally, I copied the .vdi file of the image to another location, and deleted all the references to the instances in the virtual box. Then I created another instances pointing to the same vdi file, and it worked properly.
Do enjoy virtualizing.
