Docker is a containerization platform that allows developers to package applications and their dependencies into lightweight, portable containers. Containers ensure that applications run consistently across different environments.

1. Portability: Run anywhere (local, cloud, servers).
2. Scalability: Easily scale applications with container orchestration tools.
3. Consistency: Avoid environment-specific issues.
4. Resource Efficiency: Containers use fewer resources than virtual machines.
5. Faster Deployment: Containers start quickly and reduce downtime.

• A Docker image is a lightweight, stand-alone, executable package that includes everything needed to run a piece of software (code, libraries, dependencies, and configuration files).
• Images are built from Dockerfiles and stored in Docker Hub.

Common Commands:

# List all downloaded images
docker images

# Pull an image from Docker Hub
docker pull ubuntu:latest

# Remove an image
docker rmi image_id

• A container is a running instance of a Docker image.
• Containers are isolated environments, ensuring that applications run consistently.

Common Commands:

# Run a container
docker run -d -p 8080:80 nginx

# List running containers
docker ps

# Stop a container
docker stop container_id

# Remove a container
docker rm container_id

• A Dockerfile is a script that contains a set of instructions for building a Docker image.

Example Dockerfile:

# Use an official Node.js runtime as a parent image
FROM node:14

# Set the working directory
WORKDIR /app

# Copy package.json and install dependencies
COPY package.json .
RUN npm install

# Copy the project files
COPY . .

# Expose a port and start the application
EXPOSE 3000
CMD ["node", "index.js"]

Build and Run the Image:

# Build an image
docker build -t myapp .

# Run the container
docker run -p 3000:3000 myapp

• Docker Compose allows you to define multi-container applications.

Example docker-compose.yml:

version: '3'
services:
  web:
    image: nginx
    ports:
      - "8080:80"
  database:
    image: mysql
    environment:
      MYSQL_ROOT_PASSWORD: password

Commands:

# Start services
docker-compose up -d

# Stop services
docker-compose down

• A cloud-based registry to store and share Docker images.
• You can push your own images to Docker Hub for sharing.

# Log in to Docker Hub
docker login

# Push an image to Docker Hub
docker tag myapp username/myapp

docker push username/myapp

1. A developer writes a web application in Node.js.
2. They create a Dockerfile to containerize the app.
3. They build a Docker image using docker build.
4. The image is pushed to Docker Hub.
5. A team member pulls the image and runs it locally.
6. The image is deployed to a cloud server using docker run.
7. Updates are made, a new image is built, and the cycle repeats.

Answer: Docker is an open-source platform that enables developers to automate the deployment of applications inside lightweight, portable containers.

Answer: A Docker container is a lightweight, standalone, and executable package that includes everything needed to run an application, such as code, runtime, libraries, and dependencies.

Answer: A Docker image is a lightweight, stand-alone, and executable software package that contains all the dependencies and instructions needed to run an application in a container.

Answer: You can create a Docker container using the command:

docker run -d --name my_container my_image

Answer: Use the command:

docker ps

Answer: Use the command:

docker ps -a

Answer: Use the command:

docker stop <container_id>

Answer: Use the command:

docker rm <container_id>

Answer: Use the command:

docker rmi <image_id>

Answer: A Dockerfile is a script containing a series of instructions that are used to build a Docker image.

Answer: Use the command:

docker build -t my_image .

Answer: CMD sets default commands and arguments, while ENTRYPOINT is used to define a fixed command that cannot be overridden easily.

Answer: Use the command:

docker run -it my_image bash

Answer: Use the command:

docker logs <container_id>

Answer: Use the command:

docker start <container_id>

Answer: Use the command:

docker inspect <container_id>

Answer: A Docker Volume is a persistent storage mechanism that allows data to persist beyond the lifecycle of a container.

Answer: Use the command:

docker volume create my_volume

Answer: Use the command:

docker run -v my_volume:/data my_image

Answer: Docker Compose is a tool for defining and running multi-container Docker applications using a YAML file.

Answer: Use the command:

docker-compose up -d

Answer: Use the command:

docker-compose down

Answer: The default network driver in Docker is bridge.

Answer: Use the command:

docker container prune

Answer: Use the command:

docker image prune

For More Questions Pls refer -> https://www.geeksforgeeks.org/docker-interview-questions/