Install Docker on Ubuntu VPS — Complete Beginner's Guide

What is Docker and Why Use It on a VPS?

Docker is a containerization platform that packages your application and all its dependencies into a lightweight, portable container. Each container runs in an isolated environment, eliminating the classic "it works on my machine" problem.

Docker vs Virtual Machine comparison:

System Requirements

• OS: Ubuntu 20.04, 22.04, or 24.04 LTS (64-bit)
• RAM: Minimum 1GB (2GB+ recommended)
• CPU: 1 vCPU or more
• Disk: 10GB+ free space (SSD)
• Access: root or sudo privileges
• Network: Internet connectivity

Install Docker on Ubuntu 22.04/24.04

Step 1: Update packages

sudo apt update && sudo apt upgrade -y

Step 2: Install dependencies

sudo apt install -y ca-certificates curl gnupg lsb-release

Step 3: Add Docker GPG key

sudo install -m 0755 -d /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
sudo chmod a+r /etc/apt/keyrings/docker.gpg

Step 4: Add Docker repository

echo   "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu   $(. /etc/os-release && echo "$VERSION_CODENAME") stable" |   sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt update

Step 5: Install Docker Engine

sudo apt install -y docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

Step 6: Verify installation

sudo docker run hello-world

Step 7: Run Docker without sudo

sudo usermod -aG docker $USER
newgrp docker

Essential Docker Commands

Managing Images

docker pull nginx          # Download image
docker images              # List all images
docker rmi nginx           # Remove image

Managing Containers

docker run -d -p 80:80 --name my-nginx nginx
docker ps                  # Running containers
docker ps -a               # All containers
docker stop my-nginx
docker start my-nginx
docker rm my-nginx

Logs and Shell Access

docker logs my-nginx
docker logs -f my-nginx    # Follow logs
docker exec -it my-nginx bash

Docker Compose

Docker Compose manages multi-container applications with a single YAML file. It is included with modern Docker CE:

docker compose version

Example docker-compose.yml for WordPress:

version: '3.8'
services:
  db:
    image: mysql:8.0
    environment:
      MYSQL_ROOT_PASSWORD: rootpass
      MYSQL_DATABASE: wordpress
    volumes:
      - db_data:/var/lib/mysql
  wordpress:
    image: wordpress:latest
    ports:
      - "8080:80"
    depends_on:
      - db
    volumes:
      - wp_data:/var/www/html
volumes:
  db_data:
  wp_data:

docker compose up -d

Running Your First Container

docker run -d   --name my-web   -p 8080:80   --restart unless-stopped   -v /var/www/html:/usr/share/nginx/html:ro   nginx

curl http://localhost:8080

Ports, Volumes and Networks

Port Mapping

docker run -d -p 3000:3000 my-app
docker run -d -p 127.0.0.1:5432:5432 postgres

Volumes

docker volume create my-data
docker run -d -v my-data:/data my-app
docker volume ls
docker volume prune

Networks

docker network create my-network
docker run -d --network my-network --name app1 my-app
docker run -d --network my-network --name app2 my-app

Docker Security Best Practices

• Avoid running as root: Use the USER directive in Dockerfile
• Limit resources: docker run --memory=512m --cpus=0.5
• Keep images updated: Regularly pull latest base images
• Bind to localhost: Use -p 127.0.0.1:PORT:PORT with Nginx reverse proxy
• Scan for vulnerabilities: Use Docker Scout or Trivy

Troubleshooting Common Issues

Docker daemon not starting

sudo systemctl status docker
sudo systemctl start docker
sudo systemctl enable docker

Permission denied

sudo usermod -aG docker $USER
# Log out and back in

Port already in use

sudo lsof -i :80
docker stop CONTAINER_NAME

Disk space issues

docker system prune -a
docker volume prune

Frequently Asked Questions