Learning Docker - Second Edition

Docker images

A Docker image is a collection of all the files that make up an executable software application. This collection includes the application plus all the libraries, binaries, and other dependencies such as the deployment descriptor, just needed to run the application everywhere without hitch or hurdle. These files in the Docker image are read-only and hence the content of the image cannot be altered. If you choose to alter the content of your image, the only option Docker allows is to add another layer with the new changes. In other words, a Docker image is made up of layers, which you can review using the docker history subcommand, as explained in Chapter 3, Building Images.

The Docker image architecture effectively leverages ...