Instalar VB guesbox additions in ubuntu distros

sudo apt-get update

sudo apt-get upgrade

sudo apt-get install dkms

Reboot your guest system in order to activate the updates and then proceed as described above:

Insert the VBoxGuestAdditions.iso CD file into your Linux guest's virtual CD-ROM drive [Don't do this, if the Storage tab shows it to be already attached to the virtual machine]

[open a terminal, ] Change to the directory where your CD-ROM drive is mounted, and execute:

sudo sh ./VBoxLinuxAdditions.run