If anyone still having this problem, here is what i did and worked well:
First, backup the metabase.db directory (yes, it is a folder inside /):
docker cp metabase:/metabase.db /home/metabase
To restore into a new container:
docker run -d -p 3001:3000 --name metabase2 -v /home/metabase/metabase.db:/metabase.db -e "MB_DB_FILE=/metabase.db" metabase/metabase
Notice that i’ve changed the exposed port to 3001 and container name to metabase2.
If i hit http://localhost:3001 then it is all good.