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Container Image

An immutable, content-addressed stack of filesystem layers plus a config manifest (entrypoint, env, ports) in the OCI format; runtimes union the layers into a root filesystem at start. Shared layers are stored and pulled once, which is why image ordering and small final layers matter.

jeremy Video

How Docker Image Layers Stack to Form a Container Filesystem

A container image is not a monolithic file but metadata plus an ordered sequence of read-only layers, each holding only the filesystem diff produced by one build instruction; at container creation th…