Docker Interview Preparation Course

Docker is one of the fastest growing software in technology world. Till now 4 billion Docker containers have been used. This course is designed to help you achieve your goals in Docker field. Engineers with Docker knowledge may get more salary than others with similar qualifications without Docker knowledge.

In this course, you will learn how to handle interview questions on Docker technology in Software Design and Development. I will explain you the important concepts of Docker and related areas.

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You will also learn the benefits of Docker in this course.

What is the biggest benefit of this course to me?

Finally, the biggest benefit of this course is that you will be able to demand higher salary in your next job interview.

It is good to learn Docker for theoretical benefits. But if you do not know how to handle interview questions on Docker, you can not convert your Docker knowledge into higher salary.

What are the topics covered in this course?

We cover a wide range of topics in this course. We have questions on Docker best practices, Security, DockerHub, DockerCompose etc.

How will this course help me?

By attending this course, you do not have to spend time searching the Internet for Docker interview questions. We have already compiled the list of the most popular and the latest Docker Interview questions.

Are there answers in this course?

Yes, in this course each question is followed by an answer. So you can save time in interview preparation.

What is the best way of viewing this course?

You have to just watch the course from beginning to end. Once you go through all the videos, try to answer the questions in your own words. Also mark the questions that you could not answer by yourself. Then, in second pass go through only the difficult questions. After going through this course 2-3 times, you will be well prepared to face a technical interview in Docker architecture.

What is the level of questions in this course?

This course contains questions that are good for a Fresher to an Architect level. The difficulty level of question varies in the course from a Fresher to an Experienced professional.

What happens if Docker technology changes in future?

From time to time, we keep adding more questions to this course. Our aim is to keep you always updated with the latest interview questions on Docker.

What are the sample questions covered in this course?

Sample questions covered in this course are as follows:

  1. What is Docker?
  2. What is the difference between Docker image and Docker container?
  3. How will you remove an image from Docker?
  4. How is a Docker container different from a hypervisor?
  5. Can we write compose file in json file instead of yaml?
  6. Can we run multiple apps on one server with Docker?
  7. What are the common use cases of Docker?
  8. What are the main features of Docker-compose?
  9. What is the most popular use of Docker?
  10. What is the role of open source development in the popularity of Docker?
  11. What is the difference between Docker commands: up, run and start?
  12. What is Docker Swarm?
  13. What are the features of Docker Swarm?
  14. What is a Docker Image?
  15. What is a Docker Container?
  16. What is Docker Machine?
  17. Why do we use Docker Machine?
  18. How will you create a Container in Docker?
  19. Do you think Docker is Application-centric or Machine-centric?
  20. Can we lose our data when a Docker Container exits?
  21. Can we run more than one process in a Docker container?
  22. What are the objects created by Docker Cloud in Amazon Web Services (AWS) EC2?
  23. How will you take backup of Docker container volumes in AWS S3?
  24. What are the three main steps of Docker Compose?
  25. What is Pluggable Storage Driver architecture in Docker based containers?
  26. What is Docker Hub?
  27. What are the main features of Docker Hub?
  28. What are the main security concerns with Docker based containers?
  29. What are the security benefits of using Container based system?
  30. How can we check the status of a Container in Docker?
  31. What are the main benefits of using Docker?
  32. How does Docker simplify Software Development process?
  33. What is the basic architecture behind Docker?
  34. What are the popular tasks that you can do with Docker Command line tool?
  35. What type of applications- Stateless or Stateful are more suitable for Docker Container?
  36. How can Docker run on different Linux distributions?
  37. Why do we use Docker on top of a virtual machine?
  38. How can Docker container share resources?
  39. What is the difference between Add and Copy command in a Dockerfile?
  40. What is Docker Entrypoint?
  41. What is ONBUILD command in Docker?
  42. What is Build cache in Docker?
  43. What are the most common instructions in Dockerfile?
  44. What is the purpose of EXPOSE command in Dockerfile?
  45. What are the different kinds of namespaces available in a Container?
  46. How will you monitor Docker in production?
  47. What are the Cloud platforms that support Docker?
  48. How can we control the startup order of services in Docker compose?
  49. Why Docker compose does not wait for a container to be ready before moving on to start next service in dependency order?
  50. How will you customize Docker compose file for different environments?

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How will you monitor Docker in production?

Docker provides tools like docker stats and docker events to monitor Docker in production.
We can get reports on important statistics with these commands.
Docker stats: When we call docker stats with a container id, we get the CPU, memory usage etc of a container. It is similar to top command in Linux.
Docker events: Docker events are a command to see the stream of activities that are going on in Docker daemon.
Some of the common Docker events are: attach, commit, die, detach, rename, destroy etc.
We can also use various options to limit or filter the events that we are interested in.

How can we control the startup order of services in Docker compose?

In Docker compose we can use the depends_on option to control the startup order of services.
With compose, the services will start in the dependency order. Dependencies can be defined in the options like- depends_on, links, volumes_from, network_mode etc.
But Docker does not wait for until a container is ready.

Why Docker compose does not wait for a container to be ready before moving on to start next service in dependency order?

The problem with waiting for a container to be ready is that in a Distributed system, some services or hosts may become unavailable sometimes. Similarly during startup also some services may also be down.
Therefore, we have to build resiliency in our application. So that even if some services are down we can continue our work or wait for the service to become available again.
We can use wait-for-it or dockerize tools for building this kind of resiliency.

How will you customize Docker compose file for different environments?

In Docker compose there are two files docker-compose.yml and docker-compose.override.yml. We specify our base configuration in docker-compose.yml file. For any environment specific customization we use docker-compose.override.yml file.
We can specify a service in both the files. Docker compose will merge these files based on following rules:
For single value options, new value replaces the old value.
For multi-value options, compose will concatenate the both set of values.
We can also use extends field to extend a service configuration to multiple environments. With extends, child services can use the common configuration defined by parent service.

What is the purpose of EXPOSE command in Dockerfile?

We use EXPOSE command to inform Docker that Container will listen on a specific network port during runtime.
But these ports on Container may not be accessible to the host. We can use –p to publish a range of ports from Container.

What are the different kinds of namespaces available in a Container?

In a Container we have an isolated environment with namespace for each resource that a kernel provides. There are mainly six types of namespaces in a Container.

  • UTS Namespace: UTS stands for Unix Timesharing System. In UTS namespace every container gets its own hostname and domain name.
  • Mount Namespace: This namespace provides its own file system within a container. With this namespace we get root like / in the file system on which rest of the file structure is based.
  • PID Namespace: This namespace contains all the processes that run within a Container. We can run ps command to see the processes that are running within a Docker container.
  • IPC Namespace: IPC stands for Inter Process Communication. This namespace covers shared memory, semaphores, named pipes etc resources that are shared by processes. The items in this namespace do not cross the container boundary.
  • User Namespace: This namespace contains the users and groups that are defined within a container.
  • Network Namespace: With this namespace, container provides its own network resources like- ports, devices etc. With this namespace, Docker creates an independent network stack within each container.

What is ONBUILD command in Docker?

We use ONBUILD command in Docker to run the instructions that have to execute after the completion of current Dockerfile build.
It is used to build a hierarchy of images that have to be build after the parent image is built.
A Docker build will execute first ONBUILD command and then it will execute any other command in Child Dockerfile.

What is Build cache in Docker?

When we build an Image, Docker will process each line in Dockerfile. It will execute the commands on each line in the order that is mentioned in the file.
But at each line, before running any command, Docker will check if there is already an existing image in its cache that can be reused rather than creating a new image.
This method of using cache in Docker is called Build cache in Docker.
We can also specify the option –no-cache=true to let Docker know that we do not want to use cache for Images. With this option, Docker will create all new images.