So far, we have looked at the integrated build system, the Dockerfile syntax and a sample lifecycle, wherein how a sample Dockerfile is leveraged for generating an image and how a container gets spun off from that image was discussed. In this section, we will introduce the Dockerfile instructions, their syntax, and a few befitting examples.
The FROM instruction is the most important one and it is the first valid instruction of a Dockerfile. It sets the base image for the build process. The subsequent instructions will use this base image and build on top of it. The Docker build system lets you flexibly use the images built by anyone. You can also extend them by adding more precise and practical features to them. By default, the Docker build system looks in the Docker host for the images.
However, if the image is not found in the Docker host, then the Docker build system will pull the image from the publicly available Docker Hub Registry...