OK! That was an adventure. You should now be able to build any type of Docker image that your heart desires. You know when to use COPY versus ADD, when to use ENV versus ARG, and perhaps most importantly, when to use CMD versus ENTERYPOINT. You even learned how to travel through time! This information is really a great foundation for getting started with Docker and will serve as a great reference as you develop more complex Docker images. 

I hope you have learned a lot from this chapter, but we still have more to learn, so let's turn our attention to the next topic. In Chapter 4, Docker Volumes, we are going to learn more about Docker volumes. Turn the page and let's continue our quick-start journey.