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Container image layers

As previously mentioned, a Docker image contains a number of layers that are combined into a single filesystem using a storage driver. The layers (also called intermediate images) are generated when commands are executed during the Docker image build process. Usually, Docker images are created using a Dockerfile, the syntax of which will be described later. Each layer represents an instruction in the image's Dockerfile.

Each layer, except the very last one, is read-only:

Docker image layers

A Docker image usually consists of several layers, stacked one on top of the other. The top layer has read-write permissions, and ...