DevOps(Day-26) : Docker Interview Questions - Part2

 

  • Docker vs Hypervisor?

The software that helps in the creation of Virtual machines where a virtual platform is provided to the operating systems to manage and execute the virtual machines is called Hypervisor which is otherwise called Virtual Machine Monitor or Emulator or Virtualizer. One system can control various virtual machines and this helps to manage the working of virtual machines via the hypervisor.

Docker is a service for virtualization used in OS where software is delivered in containers with software, libraries, and configuration files. Written in the Go language and developed by Solomon Hykes, the applications are created and deployed using containers and are developed as packages inside the same.

  • What are the advantages and disadvantages of using docker?

Advantages

  • Docker containers are extremely portable and can operate on any platform that supports Docker.

  • Docker containers have a smaller footprint than typical virtual machines, allowing for faster deployment times and lower infrastructure costs.

  • Docker adds layers of security by separating apps and their dependencies into distinct containers. This can aid in the prevention of security breaches.

  • Docker delivers consistency by guaranteeing that programs execute on consistent environments across various servers and development workstations.

  • Docker makes it easier for developers to share their work environments and work together on projects, which increases productivity and guarantees that everyone in the team is using the same codebase and dependencies.

Disadvantages

  • Docker can increase complexity by requiring additional tools and skills for maintaining containers and coordinating containerized applications.

  • While Docker provides a solution for dependency management, it may also create extra issues for maintaining dependencies across multiple containers and environments.

  • Docker may cause compatibility difficulties with current programs since they may not be compatible with containerization or may require additional configuration to function in a containerized environment.

  • What is a Docker namespace?

Docker uses namespaces of various kinds to provide the isolation that containers need to remain portable and refrain from affecting the remainder of the host system. Each aspect of a container runs in a separate namespace and its access is limited to that namespace.

Namespace Types:

  1. Process ID

  2. Mount

  3. IPC (Interprocess communication)

  4. User (currently experimental support for)

  5. Network

  • What is a Docker registry?

A Docker registry is a storage and distribution system for named Docker images. The same image might have multiple different versions, identified by their tags. A Docker registry is organized into Docker repositories, where a repository holds all the versions of a specific image.

  • What is an entry point?

In a Dockerfile, we use the entry point instruction to provide executables that will always execute when the container is launched.

  • How to implement CI/CD in Docker?

Dockers help developers to build their code and test their code in any environment to catch bugs early in the application development life cycle. Dockers help streamline the process, save time on builds, and allow developers to run tests in parallel.

Dockers can integrate with source control management tools like GitHub and Integration tools like Jenkins. Developers submit the code to GitHub and test the code that automatically triggers a build using Jenkins to create an image. This image can be added to the Docker registry to deal with inconsistencies between different environment types.

One method to fit the Docker in the CI process is to have the CI server build the Docker Image after it has built the application. The application goes inside the image, and the image is then pushed to the Docker hub. On another host, either QA/Dev/Production environment, pull the nearly completed build from the Docker Hub and run the Container which will run your application. In the CI server, you could even have your Compile and Testing done as part of the Image build.

  • Will data on the container be lost when the docker container exits?

The container data will be lost if the container is not tagged to the volume.

Docker volumes are a widely used and useful tool for ensuring data persistence while working in containers. Docker volumes are file systems mounted on Docker containers to preserve data generated by the running container.

  • The data doesn't persist when that container no longer exists, and it can be difficult to get the data out of the container if another process needs it.

  • A container's writable layer is tightly coupled to the host machine where the container is running. The data cannot be easily moveable somewhere else.

  • Writing into a container's writable layer requires a storage driver to manage the filesystem.

Docker has two options for containers to store files in the host machine so that the files are persisted even after the container stops:

  1. Volumes are stored in a part of the host filesystem, which is managed by

  2. Bind mounts may be stored anywhere on the host system.

  • What is a Docker swarm?

A Docker Swarm is a container orchestration tool running the Docker application. It has been configured to join together in a cluster. The activities of the cluster are controlled by a swarm manager, and machines that have joined the cluster are referred to as nodes.

What are the docker commands for the following:

  • view running containers

    docker ps -a

  • command to run the container under a specific name

    docker run --name 'container-name' 'image-name'

  • command to export a docker

    docker export 'container-name' 'path-to-save-file>.tar'

  • command to import an already existing docker image

    docker import 'path-to-docker-image' 'image-name'

  • commands to delete a container

    docker stop <container-name>

    docker rm <container-name>

  • command to remove all stopped containers, unused networks, build caches, and dangling images?

    docker system prune

Thanks for reading my article. Have a nice day.

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