William Dawson

Full Stack Developer

Docker– A well-known technology widely used and appreciated by DevOps engineers originated in 2013 and it turned out to be a big hit by the end of 2017. So what makes Docker so darn popular? The following statement about Docker will definitely give you an overview of it.

“Docker is hotter than hot because it makes it possible to get far more apps running on the same old servers and it also makes it very easy to package and ship programs.”

All the noise about Docker is happening because companies are adopting it at a remarkable rate. Numerous businesses that had already moved their server application from virtual machines to containers. As Docker is a new trend in tech town no doubt its engineers are also in demand.

Docker Interview  Questions

Here are the Top 20 Docker interviews question that will help you to achieve your goal:-

1. What is Docker?

Docker is a set-of-platform as service products. It’s an open-source lightweight containerization technology. It has made a popular name in the world of the cloud and application packaging. Docker allows you to automate the deployment of applications in lightweight and portable containers.

2. Difference between virtualization and containerization?

Containers provide an isolated environment for running the application. The entire user space is explicitly dedicated to the application. Any changes made inside the container is never reflected on the host or even other containers running on the same host. Containers are an abstraction of the application layer. Each container is a different application.

In virtualization, hypervisors provide an entire virtual machine to the guest including Kernal. Virtual machines are an abstraction of the hardware layer. Each VM is a physical machine.

3. What is a Docker Container and its advantages?

Docker containers include the application and all of its dependencies. It shares the kernel with other containers, running as isolated processes in user space on the host operating system. Docker containers don’t need any specific infrastructure, they run on any infrastructure, and in any cloud. Docker containers are basically runtime instances of Docker images.
Here are some major advantage of using Docker Container:-

  • It offers an efficient and easy initial set up.
  • It allows you to describe your application lifecycle in detail.
  • Simple configuration and interacts with Docker Compose.
  • Documentation provides every bit of information.

4. What are Docker images?

Docker image is the source of the Docker container Or can say Docker images are used to create containers. When a user runs a Docker image, an instance of a container is created. These docker images can be deployed to any Docker environment.

5. Explain Docker Architecture?

Docker Architecture consists of a Docker Engine which is a client-server application:-

  • A server which is a type of long-running program called a daemon process ( the docker command ).
  • A REST API that specifies interfaces that programs can use to talk the daemon and instruct it what to do.
  • A command-line interface (CLI) client (the docker command).
  • The CLI uses the Docker REST API to control or interact with Docker daemon applications use the underlying API and CLI.

6. What is Docker Hub?

Docker hub is a cloud-based registry that helps you to link code repositories. It allows you to build, test, store your image in the Docker cloud. You can also deploy the image to your host with the help of the Docker hub.

7. What are the important features of Docker?

Here are the essential features of Docker:-

  • Easy Modeling
  • version Control
  • Placement/Affinity
  • Application Agility
  • Developer Productivity
  • Operational Efficiencies

8. What are the main drawbacks of Docker?

Some of the disadvantages of Docker that you should keep in mind are:-

  • It doesn’t provide a storage option.
  • Offer a poor monitoring option.
  • No automatic rescheduling of inactive Nodes.
  • Complicated automatic horizontal scaling set up.

9. Tell us something about Docker Compose.

Docker Compose is a YAML file that contains details about the service, network, and volumes for setting up the Docker application. So, you can use Docker compose to create separate containers, host them and get them to communicate with other containers.

10. What is Docker Swarm?

Docker Swarm is native clustering for Docker. It turns a pool of Docker hosts into a single, virtual Docker host. Docker Swarm serves the standard Docker API, any tool that already communicates with a Docker daemon can use Swarm to transparently scale to multiple hosts.

11. What is Docker Engine?

Docker daemon or Docker engine represents the server. The docker daemon and the clients should be run on the same or remote host, which can communicate through command-line client binary and full RESTful API.

12. Explain Registries

Two types of registry are –

  • Public Registry
  • Private Registry

Docker’s public registry is called Docker hub, which allows you to store images privately. In Docker hub, you can store millions of images.

13. What command should you run to see all running container in Docker?

$ docker ps

14. Write the command to stop the Docker Container.

$ sudo docker stop container name

15. What is the command to run the image as a container?

$ sudo docker run -i -t alpine /bin/bash

16. Explain Docker object labels.

Docker object labels is a method for applying metadata to docker objects including images, containers, volumes, network, swarm nodes, and services.

17. Write a Docker file to create and copy a directory and built it using python modules?

FROM pyhton:2.7-slim


COPY . /app

docker build –tag

18. Where the docker volumes are stored?

you need to navigate


19. List out some important advanced docker commands.

20. How do you run multiple copies of Compose file on the same host?

Compose uses the project name which allows you to create unique identifiers for all of a project’s containers and other resources. To run multiple copies of a project, set a custom project name using the -a command-line option or using COMPOSE_PROJECT_NAME environment variable.

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About The Author

William is a CTO and a full-stack engineer with 10 years of experience. He has spent the past seven years doing web and mobile apps. He’s good at designing architecture and implementing agile development process. The technologies he’s worked with include: Node.js, Elixir, Rails, AngularJS, React, React Native, Objective-C, iOS, Java, Android. He’s also familiar with C++, Haskell, C#/.NET. He is an enthusiastic programmer and a great guy to know

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