DevOps with Kubernetes - Second Edition

Layers, images, containers, and volumes

We know that an image is immutable and a container is ephemeral, and we know how to run an image as a container. Nevertheless, we are still missing some information with regard to packing an image.

An image is a read-only stack that consists of one or more layers, and a layer is a collection of files and directories in the filesystem. To improve disk space utilization, layers aren't locked to just one image but are shared among images, which means that Docker simply stores one copy of a base image locally, regardless of how many images are derived from it. You can utilize the docker history [image] command to understand how an image is built. For example, you will see that Alpine has only one layer ...