A containerization platform that packages applications and their dependencies into portable units.
Docker is a platform that packages applications and their dependencies into portable containers. A container includes everything needed to run the application - code, libraries, system tools - so it works identically everywhere.
Think of containers like shipping containers: they package goods in a standard format that works on any ship, truck, or train. Docker containers work on any machine - your laptop, a colleague laptop, or production servers.
"It works on my machine" - the classic developer frustration. Code runs fine locally but breaks in production because of different operating systems, library versions, or configurations.
Docker eliminates this by packaging everything together. If it works in a Docker container on your laptop, it works the same way in production.
You write a Dockerfile describing your application:
FROM node:18
COPY . /app
RUN npm install
CMD ["npm", "start"]
Docker builds this into an image, which runs as a container. The container is isolated from other processes but lightweight - starts in seconds.
Microservices: Companies like Uber and Netflix run thousands of containers, each handling a specific service (payments, notifications, recommendations).
: Teams use Docker to ensure everyone has identical development environments. New developers run one command and have everything set up.
Learn the three main neighborhoods where applications live and why choosing the right location matters for system-wide vs personal installations.
CI/CD: Build and test in containers to guarantee consistency between testing and production.
Virtual Machines: Heavy. Each VM includes a full operating system. Takes minutes to start.
Docker Containers: Lightweight. Share the host OS kernel. Start in seconds.
A laptop can run 3-4 VMs comfortably but dozens of Docker containers.
Image: The blueprint - contains your application and dependencies.
Container: A running instance of an image.
Docker Hub: A registry where you can find pre-built images (Node.js, Python, databases).
Consistency: Same environment everywhere eliminates configuration issues.
Isolation: Applications do not interfere with each other.
Portability: Move applications between environments effortlessly.
Efficiency: Lightweight and fast compared to virtual machines.
Install Docker, pull an image (docker pull node), run a container (docker run node). Many tutorials exist, but the core concepts are simple.
Docker has become essential for modern development. Most companies use it for deployment, and understanding containers is a valuable skill for any developer.
