Today I had a strange problem with virtualbox in Debian Jessie which was no longer running. When I start a virtual machine I got the following error message
The VirtualBox Linux kernel driver (vboxdrv) is either not loaded or there is a permission problem with /dev/vboxdrv. Please reinstall the kernel module by executing '/etc/init.d/vboxdrv setup'
But the problem was that the vboxdrv was not installed so I was unable to run that command. Alos reinstalling Virtualbox or the linux-headers did not solve the problem.
After all I found this discussion on stackoverflow. I was able to solve the problem by installing a new version of Virtualbox from the backports by using the following command:
apt-get -t jessie-backports install virtualbox