INCEPTION

This project has been created as part of the 42 curriculum by pbret.

PROJECT DESCRIPTION

Inception is about building a small web infrastructure made of three services, each running in its own Docker container, orchestrated by Docker Compose. Each container is built on the Debian operating system (without its kernel).

1. NGINX     -> the web server
2. WORDPRESS -> the CMS (Content Management System), run via PHP-FPM (FastCGI Process Manager)
3. MARIADB   -> the database

CONCEPTS

Virtual machine VS Docker container

Virtual machine
A virtual machine emulates a complete computer. Through a hypervisor (VBox, UTM), it runs its own full operating system with its own kernel. Each VM therefore embeds an entire OS.

Docker container
A Docker container is a way to isolate an application (service) and everything it needs to run (dependencies), without having to embed a complete operating system.
When building a container, the system files are indeed installed: the programs, the commands (apt, bash...), the libraries. But the kernel is not installed. The container directly uses the kernel of the host machine, which it shares with all the other containers and with the host itself.

Criterion	Virtual machine	Docker container
Kernel	its own (full OS)	shared with the host
Weight	heavy (several GB)	light (a few MB)
Startup	slow	almost instant
Allocated resources	high	low
Isolation	very strong	weaker
OS choice	any	same kernel as the host
Portability	heavy to move	light image, easy to share

Managing the .env file

The .env file gathers the project's environment variables, in particular sensitive data. It is located at the root of the project and added to .gitignore for security. Docker Compose, through the env_file directive, injects them into the containers.

Docker networks

Docker offers two network modes:

• Host network: the container shares its ports directly with the host's. No isolation.
• Docker network (bridge): Docker creates a private virtual network in which the containers are isolated. They communicate with each other by their service name, while remaining invisible from the outside.

Docker volumes

A container is ephemeral. Everything it contains disappears when it is removed. For a database like MariaDB, this would be a major problem: every rebuild of the container would erase all the data.
Volumes solve this by storing the data outside the container, directly on the host machine. This way, the data survives the stop, the removal and the rebuild of the container.
This is called persistence.

Data persistence
There are two ways to handle data persistence:

• Docker volume: Docker manages the storage itself, in its own directory on the host.

• Bind mount: you link a specific directory of the host to a specific directory in the container. A bit like a symbolic link, although it is not exactly the same thing.

	Docker volume	Bind mount
Location	managed by Docker	chosen by the user
Advantage	simple, automatic, portable	direct access to the data, control over the location
Drawback	data less accessible	depends on the host path, the directory must exist

Volumes are defined in the docker-compose.yml file.

PHP-FPM

NGINX cannot execute PHP itself: it delegates this task to PHP-FPM (PHP FastCGI Process Manager).
PHP-FPM is a service that permanently maintains a pool of PHP processes ready to work. When NGINX receives a PHP request, it forwards it to PHP-FPM through the FastCGI protocol (on port 9000). PHP-FPM then executes the code, queries MariaDB if needed, and returns the generated HTML to NGINX, which passes it on to the browser.

INSTRUCTIONS

Prerequisites

• Docker and Docker Compose
• Add the domain to the /etc/hosts file of the host machine: 127.0.0.1 pbret.42.fr
• The following folders must exist on the host (they hold the volumes and the .env file):
  /home/pbret/data/mariadb
  /home/pbret/data/wordpress
  /home/pbret/data/.env

The .env file (database credentials, WordPress accounts, domain) is stored in /home/pbret/data/ and excluded from the repository via .gitignore.
The Makefile automatically copies it into srcs/ at startup.

Installation and launch

• git clone <repository_url>
• cd inception
• make

The make command copies the .env into srcs/, builds the images and starts the three containers.

Available Makefile commands

Command	Action
make	Copies the .env, builds the images and starts containers
make down	Stops and removes the containers and the network
make stop	Stops the containers without removing them
make start	Restarts stopped containers
make re	Rebuilds everything (down then up)
make clean	Stops everything, prunes Docker and removes volumes/data

Access

Once the containers are running, open a browser and go to: https://pbret.42.fr

The WordPress administration dashboard is available at: https://pbret.42.fr/wp-admin

A security warning appears because the SSL certificate is self-signed.
This is normal -> you have to accept it to access the site.

RESOURCES

• Inception tutorial — https://tuto.grademe.fr/inception/
• YouTube playlist on Inception — https://www.youtube.com/watch?v=EfIed-cFms4&list=PLpLG--nxBMd-wO_MAWh3gzqCcFh4qNMvP
• Explanatory YouTube video — https://www.youtube.com/watch?v=mspEJzb8LC4
• Official Docker documentation — https://docs.docker.com/
• AI was used as a learning and support tool throughout the project, in particular to:
  Understand the concepts
  Review and explain the configuration files
  Debug errors
  Review the Dockerfiles, the docker-compose and the Makefile
• The help of my friend Paul phautena: he guided me throughout my project. A true gem of a guy. https://profile.intra.42.fr/users/phautena