Understanding Dockerfiles, components, and directives

A Dockerfile is a simple file that constitutes a series of steps needed to build a Docker image. Each step is known as a directive, and there are different kinds of directives. Let's look at a simple example to understand how it works.

We will create a simple NGINX container, but this time by building the image from scratch and not using the one available on Docker Hub.

So, start by creating a Dockerfile, as follows:

$ vim Dockerfile
FROM ubuntu:xenial
RUN apt update && apt install -y curl
RUN apt update && apt install -y nginx
CMD ["nginx", "-g", "daemon off;"]

Let's look at each line and directive one by one to understand how this Dockerfile works:

• The FROM directive specifies what the base image for this container should be. This means we are using another image as the base and will be building layers on top of it. We start by using the ubuntu:xenial...