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 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 has become the go-to for containerized applications and development. As such, it’s no surprise that the demand for Docker engineers is high.

Then, Why do we need docker interview questions?

Docker is an open platform for developers and system administrators to build, ship, and run distributed applications. With Docker, you can manage your infrastructure in containers. Containers allow you to package your application with all of its dependencies into a standardized unit for software development.

Docker interview questions are important because they help measure a candidate’s experience and expertise with the Docker platform. By asking the right questions, you can determine if a candidate is a good fit for your organization and has the skills necessary to contribute to your Docker infrastructure. In terms of building a good rapport, it is better for engineers to have pinpoint answers to these questions as well.

If you’re looking to land a job in this area, it’s important to be prepared for the interview process. To help you out, we’ve gathered some of the most common docker interview questions for Docker engineers. We’ve also provided answers to help you better understand what the interviewer is looking for.

Top 20 Docker Interview Questions

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

1. What is Docker?

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

2. Difference between virtualization and containerization?

Ans. 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 are never reflected on the host or even on 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?

Ans. 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 advantages of using Docker Container:-

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

4. What are Docker images?

Ans. 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?

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

• A server is a type of long-running program called a daemon process ( the docker command ).
• A REST API specifies interfaces that programs can use to talk to the daemon and instruct it on 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 using the underlying API and CLI.

6. What is Docker Hub?

Ans. Docker hub is a cloud-based registry that helps you to link code repositories. It allows you to build, test, and 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?

Ans. 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?

Ans. 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 setup.

9. Tell us something about Docker Compose.

Ans. 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?

Ans. 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?

Ans. 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

Ans. Two types of the registry are –

• Public Registry
• Private Registry

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

13. What command should you run to see all running containers 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.

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

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

FROM python:2.7-slim

WORKDIR /app

COPY . /app

docker build –tag

18. Where the docker volumes are stored?

Ans. you need to navigate

/var/lib/docker/volumes

19. List out some important advanced docker commands.

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

Ans. 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 the COMPOSE_PROJECT_NAME environment variable.

In A Nutshell…

Successfully passing a docker interview is not easy. There are a lot of docker interview questions that are constantly asked in interviews. It’s important that you are prepared for them.

In this blog post, we’ve shared some of the most common docker interview questions that you may be asked in your interview.

Make sure you are well-prepared for all interview questions by studying our comprehensive list. Do you have any thoughts or insights on these questions? Let us know in the comments below and we may add them to our guide.

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