if ! $docker_path info 2> /dev/null | egrep -q '^Storage Driver: (aufs|btrfs|zfs|overlay|overlay2)$'; then
and not
if ! $docker_path info 2> /dev/null | egrep -q '^Storage Driver: (aufs|btrfs|zfs|overlay)$'; then
There is no reason for this message if using overlay2.
Your Docker installation is not using a supported storage driver. If we were to proceed you may have a broken install.
aufs is the recommended storage driver, although zfs/btrfs and overlay may work as well.
Other storage drivers are known to be problematic.
You can tell what filesystem you are using by running "docker info" and looking at the 'Storage Driver' line.
This is more about we aren’t using overlay2 internally so we can’t say it runs great with Discourse, but if there are enough people in the community saying it works, and have it running long enough, we can add it.
Sure, overlay2 being removed from the list of “sort of supported storage engines” list was an unintentional change @mpalmer made when he fixed our previous test (that was completely bust).