virtualbox no kernel (4.1.0-0.bpo.1-amd64)

WARNING: The vboxdrv kernel module is not loaded. Either there is no module
         available for the current kernel (4.1.0-0.bpo.1-amd64) or it failed to
         load. Please recompile the kernel module and install it by

           sudo /etc/init.d/vboxdrv setup

         You will not be able to start VMs until this problem is fixed.