Docker — Practical Docker Learning & DevOps Guide

A hands-on Docker reference covering Docker commands, images, containers, Dockerfiles, networking, volumes, cleanup, Docker Compose, installation, multi-stage builds, and containerized application patterns.

This repository is a practical companion for DevOps and cloud engineers who want reusable Docker examples rather than only theory.

What you'll learn

• Docker CLI fundamentals
• Images and containers
• Dockerfile patterns and multi-stage builds
• Container networking
• Volumes and persistent data
• Docker Compose
• Nginx and Java/Spring Boot examples
• Docker cleanup and disk-space management
• Container troubleshooting
• Image optimization and security practices

Repository map

Area	Path
Docker commands	docker-commands.md
Docker installation	docker_installation.md
Ubuntu installation	docker_installation_ubuntu.md
Networking	Docker Networks
Volumes	docker volumes.md
Cleanup	docker cleanup commands
Docker Compose	docker-compose/
Dockerfile examples	Dockerfile's/
Security guide	docs/security.md
Troubleshooting	docs/troubleshooting.md
Image optimization	docs/image-optimization.md

Quick start

Check your installation:

docker --version
docker info

Run a container:

docker run --name nginx-demo -d -p 8080:80 nginx:alpine
docker ps

Open http://localhost:8080.

Inspect logs and clean up:

docker logs nginx-demo
docker stop nginx-demo
docker rm nginx-demo

Build an image

Example:

FROM nginx:alpine
COPY ./website /usr/share/nginx/html
EXPOSE 80

Build and run:

docker build -t my-web-app:1.0 .
docker run --name my-web-app -d -p 8080:80 my-web-app:1.0

Docker Compose

Modern Docker installations use the docker compose command.

docker compose up -d
docker compose ps
docker compose logs -f
docker compose down

See docker-compose/ for the application/database example.

Docker networking

docker network ls
docker network create app-net
docker network connect app-net <container>
docker network inspect app-net
docker network disconnect app-net <container>

Use user-defined networks when containers need reliable service-to-service communication.

Persistent storage

Named volumes persist data beyond a container lifecycle:

docker volume create app-data
docker run --rm -v app-data:/data alpine sh -c 'echo hello > /data/message.txt'
docker run --rm -v app-data:/data alpine cat /data/message.txt

See docker volumes.md.

Multi-stage builds

The repository contains Java and frontend multi-stage examples that separate build dependencies from the runtime image.

Typical pattern:

FROM maven:3.9-eclipse-temurin-17 AS build
WORKDIR /app
COPY pom.xml .
RUN mvn -q -DskipTests dependency:go-offline
COPY src ./src
RUN mvn -q -DskipTests package

FROM eclipse-temurin:17-jre
WORKDIR /app
COPY --from=build /app/target/app.jar app.jar
ENTRYPOINT ["java", "-jar", "app.jar"]

Cleanup

Inspect disk usage first:

docker system df

Then use targeted cleanup:

docker container prune
docker image prune
docker volume prune
docker network prune

Use broad pruning carefully because unused resources may still be needed later.

Production-oriented guides

• Docker Security
• Docker Troubleshooting
• Image Optimization

Learning roadmap

Docker basics
  -> Images & containers
  -> Dockerfiles
  -> Networking
  -> Volumes
  -> Compose
  -> Multi-stage builds
  -> Security & optimization
  -> CI/CD
  -> Kubernetes

Who is this for?

• DevOps engineers
• Cloud engineers
• SREs
• Developers learning containerization
• Docker beginners
• Engineers preparing for Docker/Kubernetes interviews

Contributing

Practical improvements, corrections, new examples, and documentation updates are welcome.

See CONTRIBUTING.md.

Security

Never commit passwords, API keys, access tokens, private keys, registry credentials, or real environment files.

See SECURITY.md.

Support the project

If this repository helps you learn Docker or solve a containerization problem, consider giving it a star. It helps other engineers discover the material and motivates continued improvements.

Author

Sandeep Komal

Cloud / DevOps Engineer focused on AWS, Kubernetes, Terraform, CI/CD, automation, and DevSecOps.

• GitHub: @SandeepKomal