popular Docker interview questions

Part 1 – Docker Interview Questions (Basic)

This first part covers basic Docker Interview Questions and Answers.

Q1. What is a Docker?

Answer:
A Docker is defined as the platform for containerizing the applications to isolate it from each other in order to ensure high availability and more efficiency irrespective of the environments such as Development, Testing or Production. All the application related dependencies such as libraries, jar files, server related configurations, infrastructure-related elements will be packaged and formed as container called containerized application which does not need any dependency and works independently. It ensures the application to be run irrespective of the external factors. Containers in Docker have support from Docker Engine and Host Operating System to support all the operational or infrastructural related dependencies.

Q2. What are the components of Docker Architecture and explain?

Answer:
This is the common Docker Interview Questions asked in an interview. The Docker works on client-server architecture. The Docker client establishes communication with the Docker Daemon. The Docker client and Daemon can run on the same system. A Docket client can also be connected to a remote Docker Daemon. The different types of Docker components in a Docker architecture are–

1. Docker Client: This performs Docker build pull and run operations to establish communication with the Docker Host. The Docker command uses Docker API to call the queries to be run.
2. Docker Host: This component contains Docker Daemon, Containers and its images. The images will be the kind of metadata for the applications which are containerized in the containers. The Docker Daemon establishes a connection with Registry.
3. Registry: This component will be storing the Docker images. The public registries are Docker Hub and Docker Cloud which can be s used by anyone.

Q3. What is Docker Container?

Answer:
A Docker Container is a form of encapsulation to the application which holds all the dependencies which share the kernel with other containers in the duration of running the isolated processes on the host operating system. A Docker container can be created by creating a Docker image. These Docker images can be run after that using Docker commands. Docker containers are the instances of the Docker images at the runtime. Docker images can be stored in any public hosts or private hosts like Docker hub. Docker Image is a set of files which can be run in an isolated process.

Let us move to the next Docker Interview Questions.

Q4. What are Docker Image and Docker Hub?

Answer:
The Docker Image is a set of files and a combination of parameters which will allow creating the instances to run in separate containers as an isolated process. The Docker hub is a kind of repository to the images where these images can be stored and this access is public. The Docker run command can be used to create the instance called container which can be run using the Docker image. Docker hub is the largest public repository of the image containers which is being maintained by the community of developers and individual contributors.

Q5. What are the different functionalities and applications of using Docker?

Answer:
The different functionalities and applications of using and implementing Docker are as below:

1. It simplifies the configuration and provides ease at infrastructure level configuration.
2. It manages the code pipeline easily which provides consistent environment and stability in the application.
3. It enables the isolation of the application.
4. It improves the productivity of the developer by allowing the developer to solely concentrate on business logic.
5. It enables a lot of debugging capabilities that provides extreme useful functionalities to implement.
6. It enables rapid deployment in the form of virtualization at the operating system level.
7. It reduces the utilization of multiple servers in the form of containerization.

Part 2 – Docker Interview Questions (Advanced)

Let us now have a look at the advanced Docker Interview Questions.

Q6. What is a Docker Registry?

Answer:
A Docker Registry is a place where all the Docker Images will be stored and Docker Cloud and Docker Hub are the public registries where these images can be hosted upon. The Docker hub is the default storage for the Docker Images. An own registry can also be set up as per the requirement. Docker Data Center (DDC) can also be used which includes DTR (Docker Trusted Registry). Docker store will provide the feature of buying and selling the Docker images.

Q7. What is the lifecycle of Docker Container?

Answer:
This is the most popular Docker Interview Questions asked in an interview. The life cycle of the Docker container is as below:

1. Create a container.
2. Run the Docker container.
3. Pause the Container.
4. Unpause the Container.
5. Start the Container.
6. Stop the Container.
7. Restart the Container.
8. Kill the Container.
9. Destroy the Container.

Q8. What are Docker Objects?

Answer:
The Docker Objects are Docker Images, Services, and Docker Containers. A Docker Image is a read-only template with the configuration or runtime instructions for the Docker container. The Services allow scaling the containers across the different Docker Daemons. These all together work as Swarm.

Let us move to the next Docker Interview Questions.

Q9. What are Docker Namespaces?

Answer:
The Namespaces in Docker is a technology which provides isolated workspaces called the Container. Namespaces provide a layer of isolation for the Docker containers.

Q10. What are the important Docker commands?

Answer:

Command	Description
dockerd	To launch Docker daemon.
build	To build an image file for docker.
create	To create a new container.
kill	To kill a container.
commit	To create a new image from container changes.