"FATAL: Module vboxdrv not found in directory /lib/modules/4.10.0-20-generic"
Solution 1:
Try do reinstall "virtualbox-dkms"
sudo apt install --reinstall virtualbox-dkms
Solution 2:
For me, reinstalling virtualbox-dkms always gave an error. It was my first time upgrading the kernel, and hadn't upgraded the headers. I needed to also do
sudo aptitude install linux-headers-`uname -r`
and not accept it's first solution (which was to actually do nothing), but accept the second solution which was to upgrade some further library. After that, then
sudo apt install --reinstall virtualbox-dkms
worked for me.