1. What is Docker?

Docker is a platform for containerization — packaging an application and its dependencies into a portable, lightweight container that runs consistently across environments.

Key Features:

• Isolation: Each container runs independently.
• Portability: Runs the same way on any machine.
• Efficiency: Shares the host OS kernel, lighter than virtual machines.
• Version Control for Environments: Track, share, and roll back container versions.

2. Docker Components

1. Docker Image

   • Read-only template for creating containers.
   • Example: ubuntu:22.04, node:20-alpine.

2. Docker Container

   • Running instance of an image.
   • Can be started, stopped, removed.

3. Dockerfile

   • Script to define how an image is built.

   • Example:

     FROM node:20-alpine
     WORKDIR /app
     COPY package.json .
     RUN npm install
     COPY . .
     CMD ["npm", "start"]
     
     

4. Docker Hub

   • Registry to store and share images.

5. Volumes

   • Persistent storage for containers.

6. Networks

   • Allow containers to communicate.

3. Basic Docker Commands