10.1.1 Registry Image Distribution

Registry image distribution is the overall process by which a built image, once pushed to a registry, becomes available for any authorized client to pull and run, the mechanism that makes container images practically shareable across different machines, teams, and environments.

The Basic Distribution Flow

An image moves from being built locally, to being pushed to a registry, to being pulled and run elsewhere, completing the distribution cycle.

docker build -t registry.example.com/myteam/myapi:2.3.0 .
docker push registry.example.com/myteam/myapi:2.3.0

docker pull registry.example.com/myteam/myapi:2.3.0
docker run -d registry.example.com/myteam/myapi:2.3.0

The second pair of commands could run on an entirely different machine, having no direct access to the original build environment, yet successfully obtaining and running the exact same image.

Why Layer-Based Distribution Is Efficient

Because images are composed of layers, a registry only needs to transfer layers a client doesn't already have locally — pulling a new version of an image that shares most of its layers with a previously pulled version is typically much faster than a full transfer would be.

docker pull myapi:2.4.0

If 2.3.0 was already pulled and most layers are unchanged in 2.4.0, only the differing layers actually need to be downloaded.

Why Distribution Doesn't Require Direct Access Between Machines

A registry decouples where an image is built from where it's run — the building and running environments never need direct connectivity to each other, only each needing connectivity to the registry itself.

docker push registry.example.com/myteam/myapi:2.3.0

Why Registry Image Distribution Matters

This decoupled, layer-efficient distribution mechanism is what makes container images practically useful across the various machines and environments a real deployment pipeline typically spans, from a developer's build to a production server pulling and running the exact same, verified image.