What Is Docker and Why Use It

Docker is an open-source platform that packages applications and their dependencies into portable, isolated units called containers. Unlike virtual machines, containers share the host OS kernel and start in milliseconds rather than seconds. This lightweight isolation eliminates the classic "works on my machine" problem: if the container runs on a developer's laptop, it runs identically in CI, staging, and production. Docker's core components are the Docker Engine (the daemon that manages containers), the Docker CLI (the command-line client), Docker images (read-only templates for containers), and the registry (a repository for storing and distributing images). Docker Hub is the default public registry; private registries are available from AWS, GCP, Azure, and as self-hosted solutions. The workflow is: write a Dockerfile that describes how to build the image, run docker build to produce the image, push it to a registry, and pull and run it anywhere Docker is installed. This declarative, reproducible build process integrates naturally with CI/CD pipelines and enables infrastructure-as-code for application packaging.

Example

# Install Docker (Ubuntu)
# curl -fsSL https://get.docker.com | sh
# sudo usermod -aG docker $USER

# Verify installation
docker version
docker info

# Run your first container
docker run hello-world

# Run an interactive Ubuntu shell
docker run -it --rm ubuntu:24.04 bash

# Basic image and container commands
docker images
docker ps
docker ps -a
docker pull nginx:1.27-alpine
docker run -d -p 8080:80 nginx:1.27-alpine
docker stop $(docker ps -q)
docker rm   $(docker ps -aq)
docker rmi  nginx:1.27-alpine
docker system prune -f

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