The Best Docker Interview Questions & Answers ... - Mindmajix

Essential Docker Interview Questions 2018-Learn Now!

Q1) What is Docker?

Docker can be defined as Containerization platform that packs all your applications, all the necessary dependencies combined to form containers. This will not only ensure the applications work seamlessly given any environment but also provides better efficiency to your Production ready applications. Docker wraps up bits and pieces of software with all the needed filesystems containing everything that needs to run the code, provide the runtime, system tools / libraries. This will ensure that the software is always run and executed the same, regardless of the environment.

Containers run on the same machine sharing the same Operating system Kernel, this makes it faster – as starting the applications is the only time that is required to start your Docker container (remember that the OS Kernel is already UP and running and uses the least of the RAM possible).

Q2) What is the advantage of Docker over hypervisors?

Docker is light weight and more efficient in terms of resource uses because it uses the host underlying kernel rather than creating its own hypervisor.

Q3) How is Docker different from other container technologies?

To start with, Docker is one of the upcoming and is a fresh project. Since its inception has been done in the Cloud era, it is way better many of the other competing Container technologies which have ruled their way until Docker came into existence. There is an active community that is running towards the better upbringing of Docker and it has also started extending its support to Windows and Mac OSX environments in the recent days. Other than these, below are the best possible reasons to highlight Docker as one of the better options to choose from than the existing Container technologies.

• There is no limitation on running Docker as the underlying infrastructure can be your laptop or else your Organization’s Public / Private cloud space
• Docker with its Container HUB forms the repository of all the containers that you are ever going to work, use and download. Sharing of applications is as well possible with the Containers that you create.
• Docker is one of the best documented technologies available in the Containerization space.

Q4) What is Docker image?

Docker image can be understood as a template from which Docker containers can be created as many as we want out of that single Docker image. Having said that, to put it in layman terms, Docker containers are created out of Docker images. Docker images are created with the build command, and this produces a container that starts when it is run. Docker images are stored in the Docker registry such as the public Docker registry (registry.hub.docker.com) as these are designed to be constituted with layers of other images, enabling just the minimal amount of data over the network.

Q5) What is Docker container?

This is a very important question so just make sure you don’t deviate from the topic and I will advise you to follow the below mentioned format:

1. Docker containers include the application and all of its dependencies, but share the kernel with other containers, running as isolated processes in user space on the host operating system. Docker containers are not tied to any specific infrastructure: they run on any computer, on any infrastructure, and in any cloud.
2. Now explain how to create a Docker container, Docker containers can be created by either creating a Docker image and then running it or you can use Docker images that are present on the Dockerhub.
3. Docker containers are basically runtime instances of Docker images.

Q6) What is Docker hub?

Docker hub is a cloud-based registry service which allows you to link to code repositories, build your images and test them, stores manually pushed images, and links to Docker cloud so you can deploy images to your hosts. It provides a centralized resource for container image discovery, distribution and change management, user and team collaboration, and workflow automation throughout the development pipeline.

Q7) What is Docker Swarm?

Docker Swarm can be best understood as the native way of Clustering implementation for Docker itself. Docker Swarm turns a pool of Docker hosts into a single and virtual Docker host. It serves the standard Docker API or any other tool that can already communicate with a Docker daemon can make use of Docker Swarm to scale in a transparent way to multiple hosts. Following are the list of some of the supported tools that will be helpful in achieving what we have discussed just now.

• Dokku
• Docker Compose
• Docker Machine
• Jenkins

Q8) What is Dockerfile used for?

Dockerfile is nothing but a set of instructions that have to be passed on to Docker itself, so that it can build images automatically reading these instructions from that specified Dockerfile. A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image. Using docker build users can create an automated build that executes several command-line instructions in succession.

Q9) Can I use JSON instead of YAML for my compose file in Docker?

YES, you can very comfortably use JSON instead of the default YAML for your Docker compose file. In order to use JSON file with compose, you need to specify the filename to use as the following:
docker-compose -f docker-compose.json up

Q10) Tell us how you have used Docker in your past position?

This is a question that you could bring upon your whole experience with Docker and if you have used any other Container technologies before Docker. You could also explain the ease that this technology has brought in the automation of the development to production lifecycle management. You can also discuss about any other integrations that you might have worked along with Docker such as Puppet, Chef or even the most popular of all technologies – Jenkins. If you do not have any experience with Docker itself but similar tools from this space, you could convey the same and also show in your interest towards learning this leading containerization technology.

If you're looking for Docker Interview Questions for Experienced or Freshers, you are at right place. Mindmajix offers Docker Interview Questions 2018 that helps you in cracking your interview & acquire dream career as Docker Developer.