When you pull a Docker image, you will notice that it is pulled as different layers. Also, when you create your own Docker image, several layers are created. In this post we will try to get a better understanding of Docker layers.
1. What Is a Docker Layer?
A Docker image consists of several layers. Each layer corresponds to certain instructions in your Dockerfile. The following instructions create a layer: RUN, COPY, ADD. The other instructions will create intermediate layers and do not influence the size of your image. Let’s take a look at an example. We will use a Spring Boot MVC application which we have created beforehand and where the Maven build creates our Docker image. The sources are available at GitHub.