On podman this is built in as native command podman-image-scp[0], which perhaps could be more efficient with SSH compression.
[0] https://docs.podman.io/en/stable/markdown/podman-image-scp.1...
[0] https://docs.podman.io/en/stable/markdown/podman-image-scp.1...
Docker and containerd also store their images using a specific file system layout and a boltdb for metadata but I was afraid to access them directly. The owners and coordinators are still Docker/containerd so proper locks should be handled through them. As a result we become limited by the API that docker/containerd daemons provide.
For example, Docker daemon API doesn't provide a way to get or upload a particular image layer. That's why unregistry uses the containerd image store, not the classic Docker image store.
I am a bystander to these technologies. I’ve built and debug’ed the rare image, and I use docker desktop on my Mac to isolate db images.
When I see things like these, I’m always curious why docker, which seems so much more beaurecratic/convoluted, prevails over podman. I totally admit this is a naive impression.
First mover advantage and ongoing VC-funded marketing/DevRel