Docker Interview Questions & Notes

Docker Interview Questions & Notes 

Now, let's go through some useful Docker commands:

1. docker build: Build an image from a Dockerfile
2. docker run: Run a container from an image
3. docker ps: List running containers
4. docker images: List available images
5. docker stop: Stop a running container
6. docker rm: Remove a container
7. docker rmi: Remove an image
8. docker exec: Execute a command in a running container
9. docker logs: View logs of a container
10. docker-compose up: Start services defined in a docker-compose.yml file

Auto-scaling with Docker Swarm:

Docker Swarm is Docker's native clustering and orchestration solution. Here's a basic example of how to use it:

1. Initialize a Swarm:

   docker swarm init

2. Create a service with multiple replicas:

   docker service create --name my-web-app --replicas 3 -p 80:3000 my-nodejs-app

3. Scale the service:

   docker service scale my-web-app=5

This will increase the number of replicas to 5.

Understanding Docker Compose:

Docker Compose is a tool for defining and running multi-container Docker applications. Here's a simple docker-compose.yml file for our Node.js app:

yaml
version: '3'
services:
  web:
    build: .
    ports:
      - "3000:3000"
  redis:
    image: "redis:alpine"

To run this composition:

docker-compose up

This will start both the Node.js app and a Redis container.

To stop and remove the containers:

docker-compose down