Docker Interview Questions and Answer Part – 1

• What happens when you run docker run hello-world?

Docker CLI passes your request to Docker daemon.
Docker daemon downloads the image from Docker Hub
Docker daemon creates a new container by using the image it downloaded
Docker daemon redirects output from container to Docker CLI which redirects it to the standard output
Code language: JavaScript (javascript)

• How do you run a container?
• What do you see when you run docker ps?
• What docker commit does? when will you use it?
• Explain what is Dockerfile used for and the content of the following Dockerfile

FROM registry.access.redhat.com/rhel7/rhel

RUN yum -y install httpd && yum -y update; yum clean all

EXPOSE 80
ENTRYPOINT [ "/usr/sbin/httpd" ]
CMD [ "-D", "FOREGROUND" ]
Code language: JavaScript (javascript)

Answer:

Use the image 'rhel7/rhel' from the registry 'registry.access.redhat.com` to run httpd.
Befor running it, install the httpd package, update all packages and expose port 80.
Code language: PHP (php)

• How would you transfer data from one container into another?
• What is the difference between ADD and COPY in Dockerfile?
• What is the difference between CMD and RUN in Dockerfile?
• Explain what is Docker compose and what is it used for
• What are the differences between Docker compose, Docker swarm and Kuberenets?
• Explain Docker interlock
• What is the difference between Docker Hub and Docker cloud?

Docker Hub is a native Docker registry service which allows you to run pull
and push commands to install and deploy Docker images from the Docker Hub.

Docker Cloud is built on top of the Docker Hub so Docker Cloud provides
you with more options/features compared to Docker Hub. One example is
Swarm management which means you can create new swarms in Docker Cloud.Code language: JavaScript (javascript)

Rajesh Kumar

I’m Rajesh Kumar, a DevOps, SRE, DevSecOps, Cloud, and Platform Engineering expert passionate about sharing practical knowledge, real-world experiences, and industry best practices. I have worked at Cotocus and regularly write about technology, travel, investing, health, product reviews, and digital marketing through my various platforms.

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