What is Docker?

Docker is a tool that makes it easier to create, deploy, and run applications using containers.

Why use Docker?

Imagine you built an app that works perfectly on your machine. You send it to your teammate, and suddenly… it doesn’t work! Different OS, different dependencies, different versions — it’s a mess. Docker solves this by putting your app and everything it needs into a container.

A container is like a box with your app, its settings, and all dependencies — isolated and portable.

How does Docker work?

Docker uses the host OS’s kernel and isolates apps using features like cgroups and namespaces.

docker-architecture

  1. Dockerfile – A file that defines how to build your app.
  2. Docker Image – A snapshot of your app with everything it needs.
  3. Docker Container – A running instance of the image.
# Build an image
docker build -t my-app .

# Run a container
docker run -p 8080:80 my-app

Key Docker Commands

docker ps          # List running containers
docker images      # List available images
docker stop [id]   # Stop a container
docker rm [id]     # Remove a container

Real-World Example

You can use Docker to:

  • Host your web app with Nginx
  • Run a database like PostgreSQL or Redis
  • Create reproducible environments in CI/CD pipelines

Conclusion

Docker simplifies software deployment. It ensures your app runs the same — no matter where it’s deployed.

→ Learn more: