I would think that you would use shared folders as a means of mapping to container volumes.
I don't know if it would be such a good idea to use shared folders for actually storing containers.
I sort of agree. I've set my OMV root partition large enough that I can do a lot in there, but a lot of people may not have done that. That would mean you need to move the docker images somplace.... so to data drive someplace. Moving it is pretty easy: http://peterjolson.com/moving-…uff-to-a-different-drive/
As for the path mapping, Something like:
. This means that anything added to /opt/webapp in the container will be actually stored at /media/43j2klj234lkj432i243ij4o234/sharedFolder/Folderinside on the host.
Is a container just the configuration file?
Nope... container is like a VM image that takes up way less space and is cached so it can be rebuilt very quickly. Did you mess with this at all: https://www.docker.com/tryit/ ?