If you install virtualbox and get ready to fire up the installation of a new virtual machine, but immediately get an error about having to do '/etc/init.d/vboxdrv setup' -- but find that there's no such executable in /etc/init.d in spite of having installed the virtualbox-dkms package, then
sudo apt-get install linux-headers-`uname -r`
sudo dpkg-reconfigure virtualbox-dkms