Hands-On Docker for Microservices with Python

Chapter 3

1. What does the FROM keyword do in a Dockerfile?

It starts our image from an existing one, adding more layers to it.

2. How would you start a container with its predefined command?

You would run the following command:

docker run image

3. Why won't creating a step to remove files from a Dockerfile create a smaller image?

Due to the layered structure of the filesystem that's used by Docker, each step in a Docker file creates a new layer. The filesystem is the result of all the operations working in tandem. The final image includes all the existing layers; adding a layer never reduces the size of the image. A new step for deleting will not be present in the final image, but it will always be available as part of the previous layer.