Docker learning update! Section 3: Docker Essentials for Beginners This section was hands-on: → Container lifecycle → Port mapping & volumes → Environment variables → Dockerfiles → Node.js app containerization → Multi-stage builds @Hiteshdotcom @techie_piyush @nirudhuuu t.co/3Xh4OFCp7P
Running containers docker run <image> : run a container docker run -d <image> : run in background docker run --name my-container <image> : custom name docker run -it <image> sh : open an interactive shell
Port mapping & volumes docker run -p 8080:80 nginx Maps host port 8080 to container port 80. docker run -v $(pwd):/app <image> Mounts the current directory into the container. Useful for local development.
Container lifecycle docker ps : running containers docker ps -a : all containers docker stop <name> : gracefully stop docker kill <name> : force stop docker start <name> : start again docker rm <name> : remove a container
Debugging & managing containers docker logs <name> : view logs docker exec -it <name> sh : run commands inside docker attach <name> : attach to the main process docker cp <name>:/path/file ./ : copy files from a container.
Writing a Dockerfile A Dockerfile defines how to build an image for an application. For a Node.js app, I practiced: FROM node:22-alpine WORKDIR /app COPY package*.json ./ RUN npm install COPY . . CMD ["node","server.js"]
Building & running images docker build -t express-app . Builds an image from a Dockerfile. docker run -p 4000:3000 -e PORT=3000 --rm express-app Maps ports, passes environment variables and removes the container after it exits.
Environment variables Instead of passing variables individually: docker run -p 4000:3000 --env-file .env --rm express-app Docker can load environment variables from a file. A useful way to manage application configuration across environments.
Multi-stage builds Learned how to use multiple stages in a Dockerfile. Stage 1: Build the application and prepare dependencies. Stage 2: Create a separate runtime image using required files from the builder. COPY --from=builder /app /app
Biggest takeaway 🐳 I'm moving beyond running containers to understanding how to package and run backend applications. Next up: continuing Docker and Kubernetes, with more hands-on practice. One section at a time. 🚀 #Docker #NodeJS #DevOps
