docker-container-basics

When to Use

• You need to package an application with its dependencies for consistent deployment
• You want to isolate applications from the host system
• You're setting up development environments that match production
• You need to deploy applications across different operating systems

Prerequisites

• Docker Desktop installed on your system
• Basic command line familiarity
• Application code ready to containerize

Procedure

1. Create a Dockerfile in your project root: touch Dockerfile
2. Define the base image and dependencies: FROM node:16-alpine WORKDIR /app COPY package*.json ./ RUN npm install COPY . . EXPOSE 3000 CMD ["npm", "start"]

3. Build the Docker image: docker build -t my-app:latest .
4. Run the container: docker run -d -p 3000:3000 --name my-app-container my-app:latest
5. Verify container is running: docker ps
6. View application logs: docker logs my-app-container

Verification

• Container appears in docker ps output with "Up" status
• Application responds at localhost:3000 (or configured port)
• docker logs container-name shows expected startup messages

Pitfalls

• Forgetting to expose ports in Dockerfile and map them when running
• Not using .dockerignore leading to large image sizes
• Running containers as root user (security risk)
• Not cleaning up stopped containers and unused images

Sources

• https://www.docker.com/
• https://en.wikipedia.org/wiki/Docker_(software)
• https://www.ibm.com/think/topics/docker
• https://github.com/docker