Demystifying container runtimes [LWN.net]
▻https://lwn.net/Articles/741897
A container is created from a container image. Images are tarballs with a JSON configuration file attached. Images are often nested: for example this Libresonic image is built on top of a Tomcat image that depends (eventually) on a base Debian image. This allows for content deduplication because that Debian image (or any intermediate step) may be the basis for other containers. A container image is typically created with a command like docker build.