Painless Docker - 2nd Edition

The Base Image

Every image starts from a base image; then, using the layering system of Docker, it builds up to create the final image. The base image is usually an official image with the runtime environment you need (like python, node, or postgres), a minimal Linux distribution (like alpine, debian, or ubuntu), or a custom image you or your organization has created and published to a private registry.

A base image can also be based on other base images, and those images can be based on yet other images, creating a chain of images that ultimately leads back to a base image like scratch - an empty image that is technically the base of all bases.

The base image is specified using the FROM instruction in the Dockerfile. The FROM instruction is typically the first instruction in a Dockerfile, and it sets the stage for all subsequent instructions.

Let's create a simple Dockerfile that uses eon01/hello as the base image.

# Create a folder
mkdir $HOME/hello
cd $HOME/hello

# Create a Dockerfile
cat < Dockerfile
FROM