Docker - Interview questions

 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 Storing the Docker Images : Amazon Elastic Container Registry (ECR)

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

  1. What is Docker? How does it differ from traditional virtualization?
  2. Explain the Docker container lifecycle.

    The Docker container lifecycle refers to the various stages that a Docker container goes through from its creation to its eventual termination. Docker is a platform that allows you to package, distribute, and run applications and their dependencies in isolated environments called containers. These containers are lightweight, portable, and provide consistent environments for running applications. The container lifecycle consists of the following key stages:

  3. Image Creation: The container lifecycle begins with the creation of a Docker image. An image is a read-only template that contains the application code, runtime, libraries, environment variables, and other necessary files to run the application. Images are created using Dockerfiles, which are text files containing instructions for building the image layer by layer.

  4. Image Pulling: If the desired Docker image is not available locally, Docker will pull it from a container registry (e.g., Docker Hub) before creating a container. This step ensures that you have the latest version of the image.

  5. Container Creation: Once the image is available, you can create a new container based on that image. Containers are isolated environments that run a single application. When you create a container, you can specify various options such as network settings, environment variables, and resource limits.

  6. Container Running: Once the container is created, it enters the "running" state. The application inside the container executes as if it were on its own isolated system. Docker provides process isolation, resource control, and networking capabilities to ensure that the application runs in a consistent and controlled environment.

  7. Container Interaction: You can interact with a running container using various Docker commands, such as docker exec to execute commands inside the container, and docker attach to attach to its standard input, output, and error streams.

  8. Container Pausing and Unpausing: You can pause a running container using the docker pause command, which suspends all processes in the container. To resume the container, you can use the docker unpause command.

  9. Container Stopping and Restarting: Containers can be stopped using the docker stop command. This sends a termination signal (SIGTERM) to the application inside the container, allowing it to perform cleanup operations before shutting down. If the application doesn't stop within a certain time, Docker will forcefully terminate it. Containers can be restarted using the docker restart command.

  10. Container Removal: Containers can be removed using the docker rm command. When you remove a container, its filesystem, resources, and state are discarded. If you want to keep the container's data or configuration, you should consider using Docker volumes or other data persistence mechanisms.

  11. Image Updating and Versioning: As your application evolves, you may need to update the Docker image to include new features or bug fixes. You can do this by modifying the Dockerfile and rebuilding the image. Docker images can be versioned using tags to distinguish between different versions of the same image.

  12. Container Termination: The container lifecycle ends when the container is terminated. This can happen due to manual intervention, application exit, or system rebo

  13. What is a Docker image? How is it different from a container?
  14. How do you create a Docker image?
    Creating a Docker image involves creating a blueprint for a container that specifies how the image should be built and what it should contain. This blueprint is typically defined in a file called a Dockerfile. Here's a step-by-step guide on how to create a Docker image:

        Choose a Base Image: Start by selecting a base image that serves as the foundation for your Docker image. The base image provides the runtime environment and often includes an operating system and basic tools. You can choose from various official and community-maintained base images available on Docker Hub.

        Create a Directory for Your Application: Create a directory on your local machine to organize your application code and files that will be included in the Docker image.

        Write a Dockerfile: Inside the application directory, create a file named Dockerfile (no file extension) using a text editor. The Dockerfile contains a series of instructions that define how the image should be built. These instructions include copying files, installing software, setting environment variables, and more.

        Define the Dockerfile Instructions: Write the necessary instructions in the Dockerfile. Some commonly used instructions include:
            FROM: Specifies the base image.
            WORKDIR: Sets the working directory inside the container.
            COPY or ADD: Copies files from your local machine to the image.
            RUN: Executes commands inside the image during the build process (e.g., installing dependencies, running setup scripts).
            ENV: Sets environment variables.
            EXPOSE: Specifies the network ports that the container will listen on.
            CMD or ENTRYPOINT: Defines the command that will be executed when a container is started from the image.

        Here's a simple example of a Dockerfile for a Python application:

    # Use the official Python image as the base image
    FROM python:3.8

    # Set the working directory
    WORKDIR /app

    # Copy the application files to the image
    COPY . /app

    # Install dependencies
    RUN pip install -r requirements.txt

    # Specify the command to run the application
    CMD ["python", "app.py"]


  15. What is a Dockerfile? Provide an example of a simple Dockerfile.
  16. What is a Docker container? How is it isolated from the host system?
  17. How do you manage data persistence in Docker containers?
  18. What is Docker Compose? How does it help in managing multi-container applications?
  19. How do you link containers in Docker? Is linking containers the preferred method for communication between containers?
  20. Explain Docker networking and the different types of networks available.
  21. How do you scale Docker containers horizontally?
  22. What is Docker Swarm? How does it differ from Kubernetes?
  23. What are Docker volumes? How do they enhance data management in containers?
  24. What is the purpose of Docker Hub and Docker Registry?
  25. Explain the concept of layering in Docker images.
  26. How do you troubleshoot a container that is not starting properly?
  27. What are some security best practices for using Docker containers?
  28. How do you secure sensitive information (like passwords) in Docker images?
  29. What is Kubernetes? How does it relate to Docker?
  30. Explain the concepts of pods, deployments, and services in Kubernetes.
  31. What is a Kubernetes namespace? How is it useful?
  32. How does Kubernetes handle load balancing and scaling?
  33. What is a Kubernetes ConfigMap? How can you use it to manage application configuration?
  34. What is the purpose of the Kubernetes Ingress resource?
  35. Explain the differences between Docker Compose and Kubernetes for orchestration and deployment.
  36. How do you monitor and troubleshoot Docker containers and Kubernetes clusters?

Comments

Post a Comment

Popular posts from this blog

Docker Commands

Image
 Docker Commands 1. General Docker Commands docker --version Check the installed Docker version. docker info Display system-wide information about Docker. 2. Docker Image Commands docker build -t <image_name> . Build a Docker image from a Dockerfile in the current directory. docker pull <image_name> Download an image from Docker Hub or another registry. docker push <image_name> Push a local image to a Docker registry. docker images or docker image ls List all available images on your local machine. docker rmi <image_name> Remove an image from your local machine. docker tag <source_image> <target_image> Tag an image with a new name. docker inspect <image_name> Get detailed information about an image. 3. Docker Container Commands docker run <image_name> Create and start a container from an image. docker ps or docker container ls List all running containers. docker ps -a or docker contai...
Read more

Docker: Create a Docker file - IMAGE

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++   ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Building a Docker image involves creating a Dockerfile, which is a text file containing instructions for Docker to build an image with the required software and configurations. Here's a step-by-step guide on how to create and build a Docker image using a Dockerfile: Create a Dockerfile: Create a new file named Dockerfile in your project directory. Open the file with a text editor or an integrated development environment (IDE). Choose a Base Image: Start your Dockerfile with the choice of a base image. A base image provides the starting point for your image. For example, to use an official Ubuntu base image: FROM ubuntu:20.04 Install Dependencies and Set Up Your Application: Use the RUN instruction to install packages, set up environment variables, and configure your application: RUN apt-get update && \   ...
Read more

Docker Volumes

Image
When do we need Docker volumes ? What is Docker Volume ? 3 Volume types Docker Volumes in Docker compose file ============ Volumes : On the host there will be a Physical File system path and we plug into the docker container. So what happens is when the container writes it to its file system it get replicated to the physical file system. If i change somerthing on the physical file system gets replicated the containers as well - it works Vice-Versa First type: Host Volume:  This type will give you the right to decide which volume on the host file must be used. docker run -v /home/mount/data:/va/lib/mysql/data /home/mount/data  -- Host directory /va/lib/mysql/data -- Container file system --- Second type  - Anonymous volumes  just by specifying the container filesystem which host file should be mounted is taken care by docker itself so that directory is automatically created by docker  docker run -v  :/va/lib/mysql/data here you are only referencing the conta...
Read more