Fixing VirtualBox virtual machine startup in Ubuntu.

After Ubuntu kernel upgrades (which may happen unnoticed by the user, depending on your upgrade settings), VirtualBox 5.0 machines may fail to start.

The error message tries to be helpful and suggest to run the following command:

$ sudo /sbin/rcvboxdrv setup

However, this command fails:

Bad argument setup

As reported in several other places (but I find myself googling for it over and over again), the command that is actually helpful is:

sudo /usr/lib/virtualbox/ setup

The most permanent solution however is to upgrade to VirtualBox 5.0.16 (or newer), where the bug has been fixed. This version was released on March 4.