Getting Started with Docker: A Complete Guide

Docker has revolutionized how we deploy and manage applications. Whether you're setting up a homelab or building production infrastructure, understanding Docker is essential.

What is Docker?

Docker is a platform for developing, shipping, and running applications in containers. Containers are lightweight, standalone packages that include everything needed to run an application: code, runtime, system tools, libraries, and settings.

Prerequisites

Before we begin, make sure you have:

• A Linux server (Ubuntu, Debian, or similar)
• Root or sudo access
• Basic command-line knowledge

Installing Docker

Here's how to install Docker on Ubuntu:

sudo apt update
sudo apt install apt-transport-https ca-certificates curl software-properties-common
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg

Add the Docker repository and install:

echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt update
sudo apt install docker-ce docker-ce-cli containerd.io

Your First Container

Let's run a simple container:

docker run hello-world

This command downloads a test image and runs it in a container. If everything is working correctly, you'll see a welcome message.

Project Structure

A typical Docker project might look like this:

my-docker-project/
├── docker/
│   ├── Dockerfile
│   ├── docker-compose.yml
│   └── .env
├── app/
│   ├── index.js
│   └── package.json
├── config/
│   ├── nginx.conf
│   └── traefik.yml
└── README.md

Docker Compose

Docker Compose is a tool for defining and running multi-container applications. Here's a simple example:

version: '3.8'
services:
  web:
    image: nginx:alpine
    ports:
      - "80:80"
    volumes:
      - ./html:/usr/share/nginx/html

Save this as docker-compose.yml and run:

docker compose up -d

Essential Commands

Here are the Docker commands you'll use most often:

| Command | Description | |---------|-------------| | docker ps | List running containers | | docker images | List downloaded images | | docker logs <container> | View container logs | | docker exec -it <container> /bin/sh | Enter a container | | docker stop <container> | Stop a container | | docker rm <container> | Remove a container |

Best Practices

1. Use official images - Always prefer official images from Docker Hub
2. Pin versions - Don't use latest tag in production
3. Use volumes for data - Never store important data in containers
4. Set resource limits - Prevent containers from consuming all resources
5. Use networks - Isolate containers with custom networks

Common Pitfalls

Warning: Never run commands like docker run --rm -v /:/host alpine rm -rf /host - it could delete your entire filesystem! Always be careful with volume mounts and root access.

Next Steps

Now that you have Docker running, consider exploring:

• Portainer - A web UI for managing Docker
• Traefik - A reverse proxy for Docker containers
• Watchtower - Automatic container updates

Stay tuned for more Docker tutorials and homelab guides!