Book for Beginner Web Developers in Docker

This book offers a comprehensive guide to getting started in the world of Docker, covering everything from the most elementary concepts to the orchestration of complex applications with Docker Compose, with a practical focus for web developers; that is, you will be able to learn how to use Docker to develop your web apps with Laravel, CodeIgniter, Flask, FastAPI, Django and, ultimately, any web app that you can run with Docker or in production.
1. Introduction to Docker and its Fundamental Concepts
Before diving into commands, it is crucial to understand the philosophy behind Docker and its main components.
What is Docker and why use it?
Docker is a platform that allows you to package applications along with all their dependencies (libraries, configurations, etc.) into standardized units called containers. The primary goal is to ensure that an application runs consistently in any environment, whether it is a developer's machine, a testing server, or the cloud.
The need for Docker is best understood through analogies. Just as virtual environments in Python (venv, pipenv) isolate a project's dependencies to avoid version conflicts (for example, having one project with Django 4 and another with Django 7 on the same machine), Docker encapsulates the entire application and its environment, preventing compatibility issues with the host operating system and other projects.
Images: Your Application Templates
A Docker image is an immutable, read-only template that contains everything needed to run an application: the file system, code, libraries, and environment variables. You can think of an image as an .exe file or a class in object-oriented programming: it is a static package that does nothing on its own until it is executed. Examples of popular images include python, ubuntu, nginx, and postgres.
Containers: The Running Instances
A container is a running instance of an image. If the image is the blueprint, the container is the house built from that blueprint. When launching a container, it runs as an isolated process with its own file system, network, and environment, but sharing the host operating system's kernel, which makes it much lighter than a full virtual machine. Containers are portable, self-contained, and can be created, started, stopped, and deleted independently.
2. Architecture and Essential Docker Commands
To interact with Docker, two main components work together.
The Client (docker) and the Daemon (dockerd)
Docker Client (docker): It is the command-line tool (CLI) that the user interacts with. When you type a command like docker run, you are using the client.
Docker Daemon (dockerd): It is the Docker engine, a process that runs in the background and is responsible for managing images, containers, networks, and volumes. The client sends instructions to the daemon, and the daemon executes them.
Essential Commands for Management
docker images: Lists all the images downloaded to your system.
docker ps: Shows the containers that are currently running.
docker ps -a: Shows all containers, both active and stopped.
docker run image: Creates and starts a new container from an image.
docker stop id/name: Stops a running container.
docker rm id/name: Deletes a stopped container.
docker rmi id/name: Deletes an image.
docker logs id/name: Shows the logs of a container, useful for debugging.
docker exec -it id/name bash: Allows access to an interactive terminal inside a container that is already running.
3. Creating Custom Images with Dockerfile
The true power of Docker for developers lies in the ability to create their own images for their projects.
The Dockerfile
A Dockerfile is a text file without an extension that contains a set of sequential instructions to build a custom image. Its typical structure includes:
FROM: Defines the base image on which the new image will be built (e.g., FROM python:3.12-slim).
WORKDIR: Sets the working directory inside the container (e.g., WORKDIR /app).
COPY: Copies files from the host system to t