docker save stores a Docker image to a tar archive. It is useful to make an offline backup of an image or transfer an image to a computer in a corporate environment which does not have a direct access to the Internet.
For example, to save the nginx image already in local computer to a file named
nginx-backup.tar, the following command can be run:
docker save -o nginx-backup.tar nginx
Or with a specific version:
docker save -o nginx-backup.tar nginx:1.15.5