Docker is an open-source containerization platform that provides services to facilitate the deployment of applications/software in a container. In this blog post, we will go over the Top Docker Interview Questions that are asked in interviews.

Question: What is a container in terms of Software?

Answer: Containers are executable logical components that are standardized so that application code can run in any environment. It contains the application source code along with operating system libraries and any dependency that is needed to run that application.

Question: What is a Docker?

Answer: Docker is an open-source containerization platform that provides services to facilitate the deployment of applications/software in a container. It allows developers to package/manage their applications through the use of containers. Once the applications are packaged in a container, docker can be used to deploy these containers as one block. These containerized applications can work seamlessly in any environment, be it development, testing, or production. This concept of managing dependency by the developer has helped to reduce errors in the deployment and execution process. With the use of docker, delivery and scalability of distributed applications have been easier in the on-premise and hybrid cloud environments.

Docker is written in Go programming language and has both free and paid licenses.

Question: What is the advantage of using Docker?

Answer: There are many advantages that docker provides. Below are the important ones.

• Development, Deployment, and Execution of applications are quick
• Deployment of Docker containers can be done on any physical machine, virtual machine, or the cloud as a hybrid architecture.
• A common operating system kernel can be used for all containers.
• A Docker container is light-weight in terms of resources and space compared to the virtual machine

Question: What is Dockerfile?

Answer: A Docker File is a text document that has a set of instructions with the correct parameters to create a Docker image. It contains a list of Docker commands that run sequentially to build an image, along with any dependencies needed. These commands can be any of the following.

• Installing Java/Python/Scala Programming Language
• Install and set up Hadoop/Spark software
• Copying the Jar File
• Any steps that are needed for running that application

Question: What are the main types of Docker components?

Answer: Docker has three main components.

• Host: All the docker containers are created in the host component.
• Client: This component runs and builds commands on the host.
• Registry: This component holds all the information related to the registry

Question: What is the advantage of Docker over Hypervisors?

Answer: There are mainly two reasons that make it advantageous over Hypervisor.

• Docker is efficient when using resources.

• Docker is lightweight as it uses the underlying host kernel instead of creating its hypervisor

Question: What are the different platforms on which docker can run?

Answer: Docker runs on many platforms, as shown below.

• Linux: Ubuntu, Fedora, Red Hat, CentOs, Arch Linux, OpenSUSE

• Windows: Microsoft platforms like Windows, window server

• Cloud: Amazon AWS, Google Cloud, Microsoft Azure, Rackspace

Question: What is a Docker Hub?

Answer: The Docker hub is a cloud-based registry where Docker images are stored. It allows developers to build, test, and store images in the docker cloud. They can deploy images to the host with the help of the docker hub. There are both free and paid versions of the docker hub available.

Question: What is a Container in Docker?

Answer: A container is a separate sandbox-like process on one machine that is separate or isolated from all the processes on the host machine. This isolation uses the features of a Linux-like kernel, namespaces, and groups.

Containers have the following properties.

• They are runnable from an image, that can be started, stopped, moved, or deleted using a command-line interface.

• Containers can be run on machines, virtual machines, or in the cloud.
• They are operating system agnostic as it is portable on any operating system

• They are isolated from each other as they run their software, binaries, and configurations.

Question: What are the Different Phases of Docker Containers?

Answer: The Docker container life cycle consists of five phases.

• Create Phase

• Running Phase

• Paused Phase/ UnPause Phase

• Stopped Phase

• Killed Phase

Question: What is Virtualization Technology?

Answer: Virtualization is the process of creating a virtual or software-based component of hardware elements like computers, storage servers, etc. These virtualized versions of environments are created from a physical hardware system. Virtualization allows us to split an existing system into multiple individual units that can be either similar or disparate systems. We use software called a hypervisor to achieve this. A virtual environment that is created by Hypervisor is called a Virtual Machine.

Question: What are the types of registries available in Docker?

Answer: Docker provides two types of registries known as Docker Hub.

• Public Registry: This is free for everyone to us. It allows developers to collaborate on projects using public images.
• Private Registry: This allows developers to store the images privately