What is Docker and Docker Compose? A Beginner's Guide to Containerization
Learn how Docker and Docker Compose make development and self-hosting easier than ever.
Publish date: 11/25/2024
Learn how Docker and Docker Compose make development and self-hosting easier than ever.
Publish date: 11/25/2024
Software deployment used to mean endless hours of configuring servers, resolving dependency conflicts, and debugging environment-specific issues. Docker changed that forever by introducing containerization to the masses, and Docker Compose made managing complex applications straightforward.
In this article, we'll explain a bit more about what both of these tools do, and explore how they work together to make application deployment simpler and more reliable than ever before. Let's dive in.
Imagine you're moving to a new house. Instead of throwing all your belongings loosely into a moving truck, you pack everything into standardized shipping containers. Each container is self-contained, protecting its contents and making it easy to transport. This is essentially what Docker does for software.
Docker creates containers that package your application code, runtime, system tools, libraries, and settings. These containers are lightweight, standalone, and executable packages that include everything needed to run your application. The best part? They work the same way whether you're running them on a Raspberry Pi, your laptop, a VPS, a dedicated server, or beyond.
Traditional application deployment often leads to the infamous "it works on my machine" problem. Docker eliminates this headache by ensuring your application runs identically across all environments. When you create a Docker container, you're creating a consistent, isolated environment that remains unchanged regardless of where it runs.
For example, if you're running a LAMP stack, Docker lets you package Apache, MariaDB, PHP, and all their dependencies into a container that works flawlessly across different systems.
At its core, Docker uses containerization technology built into the Linux kernel—specifically namespaces and cgroups. Namespaces provide isolation for system resources like processes, network interfaces, and mount points, while cgroups manage resource allocation like CPU, memory, and I/O.
When you run a Docker container, you're essentially creating a lightweight runtime environment that:
For example, when you run a command like docker run nginx, Docker:
While Docker excels at running individual containers, modern applications often require multiple services working together. This is where Docker Compose shines. Instead of managing each container separately with long docker run commands, Docker Compose lets you define your entire application stack in a single YAML file.
Docker Compose uses a docker-compose.yml file that describes:
Here's a practical example. Let's say you're setting up Uptime Kuma to monitor your services.
Instead of running multiple Docker commands, you can define everything in a docker-compose.yml file:
services:
uptime-kuma:
image: louislam/uptime-kuma:1
container_name: uptime-kuma
volumes:
- ./data:/app/data
ports:
- "3001:3001"
restart: always
nginx:
image: nginx:latest
ports:
- "80:80"
volumes:
- ./nginx.conf:/etc/nginx/nginx.conf
depends_on:
- uptime-kuma
With this configuration, you can:
docker compose up -d commanddocker compose downdocker compose logsLet's look at the advantages and potential challenges of using Docker and Docker Compose in your development workflow.
Docker and Docker Compose shine in several common scenarios:
The beauty of Docker is that it's easy to get started, and most importantly you can start small and scale as needed. Many popular applications offer official Docker images.
While Docker's installation varies depending on OS/distribution, for an easy way to get started, we recommend checking out our guide on how to install Docker and Docker Compose on Debian 12 (Debian is our recommended distribution here because it's lightweight and just works). For alternative installation instructions, you can check out Docker's documentation here.
Once you have Docker running, you might want to explore tools like Watchtower to keep your containers automatically updated.
Docker and Docker Compose have entirely changed how we deploy and manage applications for the better. The ability to create consistent, portable environments makes Docker an invaluable tool for deploying applications and self-hosting.
Whether you're a developer looking to streamline your development environment or a system administrator managing multiple applications, Docker's containerization approach offers a great solution for common deployment challenges.
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