Fix errors about a missing kernel driver wanting to install dkms and run
/sbin/vboxconfig, with thi procedure.
This error usually happens when going between major or point releases–say Virtualbox 5.0 → 5.1 or 4.3 → 5.1).
It can also happen when upgrading the operating system.
Uninstall old Virtualbox by
apt remove virtualbox
dpkg -r virtualbox
Then reinstall new Virtualbox: