Images and Layers

As already mentioned, Docker images are a collection of loosely connected read-only layers where each layer comprises one or more files. The figure below shows an image with four layers. Docker takes care of stacking them and representing them as a single unified image.

Inspecting layers

Let’s look at all of the following ways to inspect layer information:

• Pull operations
• The docker inspect command
• The docker history command

Run the following command to pull the node:latest image and observe it pulling the individual layers. Some newer versions may have more or less layers, but the principle is the same.

Each line ending with Pull complete represents a layer that Docker pulled. This ...