Even if /var/lib/docker is on it's own mount, what do we do when it nears 100%? Explore and document the results of each of the following:

• Extend the volume
• Create a new volume and move the data – if so, how (rsync -H -S?)
• Create a snapshot and create a new volume (is this efficient – how long does it take)
• Shut down Docker and delete the data (of course, you have to unmount overlay mounts, etc). https://github.com/moby/moby/issues/3127#issuecomment-30095339

Make sure we know what's actually happening, document it, recommend what to do under different conditions (i.e., I'm in a workshop now and need this solved in 10 minutes versus a long-running instance).  Best effort.