Introduction:
Docker, a cornerstone in the realm of DevOps, holds immense significance for those venturing into the field. In this blog post, we'll delve into key Docker interview questions, breaking down complex concepts into digestible answers.
1. What is the Difference between an Image, Container and Engine?
- An image is a snapshot, a container is a running instance of that snapshot, and the engine manages them. Think of an image as a recipe, a container as the dish, and the engine as the chef orchestrating the cooking.
2. What is the Difference between the Docker command COPY vs ADD?
- COPY copies local files, while ADD does more, like extracting archives. For simplicity, it's advisable to prefer COPY.
3. What is the Difference between the Docker command CMD vs RUN?
- RUN executes commands during image build, while CMD sets a default command for the container to run.
4. How Will you reduce the size of the Docker image?
- To shrink the image, use multi-stage builds, minimize layers, and remove unnecessary files. This ensures a lean and efficient image.
5. Why and when to use Docker?
- Docker simplifies deployment by packaging applications with dependencies, ensuring consistency across different environments. It shines in scenarios demanding scalability and consistency.
6. Explain the Docker components and how they interact with each other.
- Docker Compose orchestrates services, Docker File defines the image, Docker Image is a packaged app, and Docker Container is a running instance. They collaborate seamlessly for smooth operations.
7. Explain the terminology: Docker Compose, Docker File, Docker Image, Docker Container?
- Docker Compose manages services, Docker File sets up the image, Docker Image is the packaged app, and Docker Container is the live instance.
8. In what real scenarios have you used Docker?
- Docker proves invaluable in scenarios like microservices architecture, ensuring app isolation, easy deployment, and scalable solutions.
9. Docker vs Hypervisor?
- Answer: Docker is lightweight, sharing OS resources, while a Hypervisor is heavier, creating virtual machines. Docker is preferred for efficiency.
10. What are the advantages and disadvantages of using docker?
Advantages include easy scaling and consistency.
Disadvantages involve security concerns and a steeper learning curve.
11. What is a Docker namespace?
- Docker namespace isolates processes and resources, preventing conflicts between containers.
12. What is a Docker registry?
- Docker Registry is a storage and distribution system for Docker images, acting as a library for sharing and accessing images.
13. What is an entry point?
- Entry Point is a command specifying what runs when the container starts, setting the stage for container activities.
14. How to implement CI/CD in Docker?
- CI/CD in Docker involves using CI tools for automated building and testing of Docker images, followed by deploying with CD tools.
15. Will data on the container be lost when the docker container exits?
- Data inside a container is lost if not persisted externally, like using volumes for data retention.
- What is a Docker swarm?
- Docker Swarm is Docker's native clustering solution, orchestrating and managing multiple containers seamlessly.
17. What are the docker commands for the following:
- View running containers:
docker ps
- Run container with a specific name:
docker run --name <name>
Export:
docker exportImport:
docker importDelete container:
docker rmRemove all unused:
docker system prune
18. What are the common docker practices to reduce the size of Docker Image?
- Utilize Alpine images, minimize layers, and eliminate unnecessary dependencies and files to create compact Docker images.
Conclusion:
Docker, with its versatile capabilities, stands as a fundamental skill for any DevOps engineer. Mastering these interview questions not only prepares you for interviews but also equips you to harness the power of Docker effectively in real-world scenarios.