VOLUME command not needed?

[gannebamm]

Why do we use VOLUME? https://github.com/GeoNode/geoserver-docker/blob/2.18.2/Dockerfile#L20

This image is intended to get used in conjunction with geoserver-data-dir which will mount this directory already, isn´t it?

[frafra]

It can make a difference if you forget to start geoserver without mounting the goserver-data-dir. It can help the developer understanding that such folder should be persistent.
On the other side, someone could like to just fire geoserver without any kind of persistence and found VOLUME redundant.

I do not like VOLUME, actually. Everything should be ephemeral by default, and I do not want to end up having volumes around which I didn't expect and have to go thought the various Dockerfiles. I think there is not a general recommendation here.