missing package dependency on linux-image-extra-* / linux-image-generic

[Jonas Finnemann Jensen]

Installing v4l2loopback-dkms in blank vagrant VM (or VM on cloud provider) creates a machine where v4l2loopback is installed by the required kernel module videodev.ko is not installed.

dmseg shows missing symbols and the v4l2loopback module fails to load.

The workaround is to "apt-get install linux-image-generic", as this will install the "linux-image-extra-*" package, which includes the videodev.ko module.

This wasn't a problem with 16.04, quite likely because most VM images weren't as stripped down as they are today, and thus, always included linux-image-generic.

It's probably reasonable to just make v4l2loopback-dkms depends on linux-image-generic.

Note: This might seem like a corner case, but arguably v4l2loopback is often used for automated testing which often runs on VMs in the cloud.