If you are reading this article it means that you have heard of Docker for work reasons or because you are passionate about software development and want to understand what it is and how it works. We will therefore try to answer the question starting from the beginning and illustrating all the concepts that underlie the functioning of this open source platform which has revolutionized the way in which we develop, distribute and run applications.
Docker is a platform that allows developers to build, deploy, and manage containerized applications. To understand what Docker is, it is therefore essential to understand the concept of containers.
The containers
A container is a lightweight, portable unit that includes everything needed to run an application: code, runtime, system libraries, settings, and dependencies. Unlike virtual machines (VMs) that run an entire guest operating system on top of a hypervisor, containers share the host operating system kernel but operate in isolation. This makes them extremely efficient in terms of resources and speed.
Docker containers work thanks to two main components: Docker images and the Docker Engine:
- A Docker image is a read-only template that contains all the instructions for creating a container. Images are built from a file called Dockerfile, which specifies all their dependencies and the steps needed to set up the container environment. Images can be stored and shared via registries like DockerHub.
- The Docker Engine is the component that manages the execution of containers. It is responsible for creating, running, and managing containers on the host operating system.
How does the Docker Engine work?
The Docker Engine is the core of the Docker platform and consists of the following parts:
- The Docker Client is the main interface through which users send commands. It is a command line program that translates user instructions into API requests that the Docker Daemon can understand and execute. The Docker Client is available on multiple platforms, including macOS, Windows, and Linux, and provides a wide range of commands for managing Docker containers.
- The Docker Daemon receives requests via the REST API and executes them, managing the various processes necessary to create and manage containers. This includes downloading the required images, creating containers, and managing system resources.
With its client-server architecture, the Docker Engine allows developers to build, run, and manage containers efficiently and consistently.
What are the advantages of Docker?
Adopting Docker offers numerous benefits:
- Portability: Thanks to containerization, applications can seamlessly run on any environment that supports Docker, from the developer’s laptop to production servers.
- Isolation: Each container operates in an isolated environment, meaning that applications do not interfere with each other.
- Resource efficiency: Containers are much lighter than VMs, allowing you to run multiple containers on the same hardware.
- Speed of deployment: Creating and launching containers is very fast, facilitating the development and deployment cycle.
Docker has become a key tool in the context of DevOps, which aims to unite software development (Dev) and IT operations (Ops). With Docker, you can automate many parts of the application lifecycle, from writing code to testing to full-scale deployment. Orchestration tools like Kubernetes integrate with Docker to manage container clusters in production, improving application scalability and resilience.
Docker has transformed the way we think about building and deploying applications. Its ability to isolate applications in portable, lightweight containers has reduced compatibility issues and improved resource efficiency. If you haven’t started using this tool yet, it’s time to explore this powerful technology and find out how it can improve your workflow.