Top 50+ Docker Interview Questions & Answers [2022]

Are you looking for Docker Interview Questions and Answers for your upcoming DevOps interview?

In this post, you will know some of the most often asked Docker job interview questions for both freshers as well as seasoned DevOps engineers.

Here they are:

Docker Interview Questions & Answers

1. What exactly is Docker?

Ans: Docker is a lightweight containerization technology that is open source. It has acquired considerable acceptance in the cloud and application packaging communities. It enables you to automate application deployment in lightweight and portable containers.

2. Why do we need to use Docker?

Ans: Docker is lighter in weight and more resource efficient since it leverages the host’s underlying kernel rather than creating its own hypervisor.

3. How can I use Docker to create environment-agnostic systems?

Ans: There are three key characteristics:

VolumesEnvironment Variable Injection.
Read-only file systems.

4. What are the most popular Dockerfile instructions?

Ans: FROM, LABEL, RUN, and CMD

5. What is the Docker workflow?

Ans: It begins with a docker file, which must be built in order to produce an image of the container, which is then redistributed through a registry and used to run the containers.

6. What exactly is Docker Swarm?

Docker Swarm is a native gathering tool for Docker. It is used to combine many Docker hosts into a single virtual Docker host. It provides the standard Docker application programming interface.

7. How should a docker be monitored in a production environment?

Ans: Docker stats and Docker Events.

8. Why does Docker Compose not wait for a container to be ready before proceeding to the next service in dependency order?

Ans: Docker compose begins in the order specified by the link volume form and network mode.

9. How does communication between the Docker client and the Docker Daemon take place?

Ans: A combination of Rest API, Socket.IO, and TCP.

10. Where are the Docker images stored by the Docker Daemon?

Ans: In Docker Registry.

11. What are the different Docker container states?

Ans: There are four states: Running, Paused, Restarting, and Exited.

12. Where are the Docker volumes stored?

Ans: In /var/lib/docker/volumes.

13. What exactly are Docker object labels?

Ans: This is the method for adding metadata to Docker objects like as images, containers, local daemons, volumes, networks, Swarm nodes, and swarm services.

14. How to start containers automatically?

Ans: We must employ a restart policy…for example…docker run always.

15. How should the image be published?

Ans: docker push username/repository:tag

16. How to scale 1the app?

Ans: Change the replicas value in docker compose.yml and rerun the “docker stack deploy” command.

17. How can I make a virtual machine with Docker?

Ans: Use the command docker-machine create –driver virtual box myvm1 to create a container.

18. What exactly does the Docker inspect do?

Ans: It will provide more information about the container in json format.

19. How do you use Docker to implement CI/CD?

Ans: You need to run Jenkins on Docker and use docker-compose to execute integration tests jenkins.

20. What is the difference between CLIs in Docker?

Ans: Engine CLI, Compose CLI, Machine CLI, DTR (Docker Trusted Registry)CLI, UCP (Universal Control Pane) CLI

21. How do I start the Docker Daemon?

Ans: By running dockerd [options]

22. How to get Docker performance?

Ans: Docker stats or Docker top are two options.

23. How can I inspect container logs?

Ans: By Docker logs

24. How to install logging driver plugin?

Ans: docker plugin install org/imgname> is the solution.

25. How do you log tags for the logging driver?

Ans: We must utilize the tag option.

docker run –log-driver=fluentd –log-opt fluentd-address=myhost.local:24224 –log-opt tag=”mailer”

26. What is Docker security ?

Ans: There are four factors to consider: kernel namespaces, control groups, the docker daemon attack surface, and Linux kernel capabilities.

27. How can I check the status of a container?

Ans: docker ps is the answer.

28. How you manage Docker images?

Ans: Docker Hub and Docker Registry are used to manage Docker images.

29. How do you run several Docker commands?

Ans: docker run image /bin/bash -c “cd /path/; python a.py” is the solution.

30. When will you utilize Docker Swarm?

Ans: We will use Docker Swarm to manage container scheduling across several hosts.

31. How do you create a Jenkins image with Docker?

Ans: Docker pull jenkins

32. What are the benefits of Docker?

Ans: The following are Docker’s benefits:

Return on investment (ROI) and cost-cutting measures
Productivity and standardization
Efficiency and CI/CD.
Simple and safe.
Detailed documentation.

33. What is the Docker container life cycle?

Ans: It is Build, Pull, and Run.

34. How do you know what version of Docker you’re running?

Ans: We may use the docker version command 19.03 to find out.

35. How can I use systemd to control Docker?

Ans: By systemctl start/stop docker and service docker start/stop

36. What exactly are Docker object labels?

Ans: It is used to add metadata to Docker objects such as images, containers, local daemons, volumes, networks, swarm nodes, and swarm services.

37. What is the best way to clean up Docker objects?

Ans: By Docker image pruning and Docker container pruning.

38. How can we share Docker containers across nodes?

Ans: Through the use of Docker Swarm. Docker swarm is made up of two types of nodes. One is the manager node, while the other is the worker node.

39. What is the command for creating a Docker swarm?

Ans: docker swarm init –advertise-addr is the command.

40. How can I run multiple containers with a single service?

Ans: Through the use of Docker Compose. Each container runs alone, although they can communicate with one another. The yaml programming language is used in all Docker Compose files.

41. Do you know how to utilize json instead of a yaml compose file?

Ans: By docker-compose -f docker-compose.json up.

42. How do I incorporate code in a copy/add or volumes?

Ans: In the Docker file, we must use the COPY or ADD directive. This is helpful for relocating code. If we wish to make modifications, we should utilize a volume.

43. How you can push the new image to the Docker registry?

Ans: By docker push myorg/myimg

44. What are the key characteristics of Docker?

The following are Docker’s most important features:

Modeling is simple.
Control over the versions.
Affinity/Placement
Agility in application.
Developer Productivity.
Efficiencies in operations.

45. What is Docker Engine, and how does it work?

The server is represented by the Docker daemon or Docker engine. The Docker Daemon and clients should be run on the same or a remote host, and they should be able to interact via a command-line client binary and a full RESTful API.

46. What exactly is a Docker image?

The Docker image helps in the creation of Docker containers. The build command may be used to create a Docker image. As a result, it generates a container that starts when it starts running. The Docker registry contains all of the docker images.

47. What are Docker’s primary drawbacks?

The following are some of Docker’s noteworthy drawbacks:

There isn’t a storage option.
Provides a subpar monitoring option.
Inactive Nodes are not automatically rescheduled.
Setup for automated horizontal scaling is complicated.

48. What exactly is a Docker hub?

Docker Hub is a cloud-based registry that facilitates the linking of code repositories. It enables you to build, test, and store your images on the Docker cloud. Docker hub may also be used to deploy the image to your host.

49. What is the definition of virtualization?

Virtualization is a technique for logically dividing mainframes in order to execute many programs at the same time.

It lets many operating systems to operate in parallel on a single x86-based machine.

50. Is IPV6 support available in Docker?

Docker does, in fact, support IPv6, however o nly Docker daemons running on Linux servers support IPv6 networking. However, if you want the Docker Daemon to support IPv6, you must modify /etc/docker/daemon.json and change the ipv6 key to true.

51. What are Docker Namespaces, and how do I use them?

In Docker, the Namespace is a way for creating isolated workplaces known as Containers. Docker containers benefit from a layer of isolation provided by namespaces.

52. What are the three elements that make up the Docker Architecture?

Client, Docker-Host, and Registry are the three components.

53. What is a Hypervisor?

You may use the hypervisor to create a virtual environment in which guest virtual machines can run. It monitors the guest systems and ensures that the required resources are provided to the visitors.

54. What is Docker_Host’s purpose?

It contains containers, images, and the Docker Daemon. It provides a complete environment in which your application may be executed and run.

Learn more about Docker.