I’m currently running Ubuntu 16.04 LTS [beta] and just using apt-get install virtualbox, have installed the virtualbox tool so that I could install Kali Linux.
So I can get full screen virtual machines, you have to install the guest additions, now this needs to compile a few things and do other behind the scenes funky stuff, so this is how I added the additions using Ubuntu/Virtualbox and Kali Linux.
1, Install virtualbox
2, install Kali Linux into virtual box and apt-get dist-upgrade so you’re at the latest upto date version
3, apt-get install linux-headers-$(uname -r)
4, In virtualbox (not the guest os), click Devices -> Insert Guest Additions CD Image…(please note when I installed virtualbox i didn’t get the additions ISO, so had to download it when it asked me too)
5, Copy the file VBoxLinuxAdditions.run from /media/cdrom to the desktop – cp /media/cdrom/VBoxLinuxAdditions.run /root/desktop then cd to the desktop – cd /root/desktop
6, Make the .run file executable – chmod +x VBoxLinuxAdditions.run
7, Install it – ./VBoxLinuxAdditions.run
8, Once finished and back at the prompt reboot the virtual machine and you should then be able to maximise the window or use HOST – F to make it full screen.