Immutable infrastructure with containers

Containerization consists of deploying applications in containers instead of deploying them in VMs.

Today, it is very clear that the container technology to be used is Docker and that the configuration of a Docker image is also done in code in a Dockerfile. This file contains the declaration of the base image, which represents the bone to be used, the installation of additional middleware to be installed on the image, only the files and binaries necessary for the application, and the network configuration of the ports. Unlike VMs, containers are said to be immutable; the configuration of a container cannot be modified during its execution.

Here is a simple example of a Dockerfile:

FROM ubuntu
RUN apt-get update
RUN apt-get install -y nginx
ENTRYPOINT ["/usr/sbin/nginx","-g","daemon off;"]
EXPOSE 80

In this Docker image, we use a basic Ubuntu image, install nginx, and expose port 80.