How to port data-only volumes from one host to another?

Question

As described in the Docker documentation on Working with Volumes there is the concept of so-called data-only containers, which provide a volume that can be mounted

Answer 1

You can export the volume to tar and transfer to another machine. And import the data with tar on the second machine. This does not rely on implementation details of the volumes.

# you can list shared directories of the data container
docker inspect  | grep "/vfs/dir/"

# you can export data container directory to tgz
docker run --cidfile=id.tmp --volumes-from  ubuntu tar -cO  | gzip -c > volume.tgz

# clean up: remove exited container used for export and temporary file
docker rm `cat id.tmp` && rm -f id.tmp