Docker Interview Questions with Answers

Docker is an open source containerization platform.

- Docker is used to work with containers.

- knowledge about containers and how Docker is used to work with them.

Docker is a containerization platform used to manage the life cycle of containers.

- The first question in the interview is about your experience with Docker and containers.

- The second question is about the difference between containers and virtual machines.

Explain the life cycle of Docker

- Start with writing a Docker file that contains instructions to run the application

- Build the Docker image using Docker CLI, then create and execute the container using Docker CLI

Different Docker components explained

- Docker components include client, Docker CLI, Docker daemon, Docker desktop

- Docker daemon is the heart of Docker, responsible for executing actions

Docker add command is used to download a specific package from the internet, while Docker copy command is used to copy files from the file system.

- CMD is used to pass arguments to the container that can be overwritten, while entry point is the name of the function.

- The difference between CMD and entry point in Docker is that CMD allows the user to provide configurable parameters, while entry point is fixed.

Understanding the difference between CMD and entry point in Docker

- The entry point should not be overwritten and should be passed as an entry point

- The parameters that can be overridden should be passed using CMD

MacVlan Network allows a container to appear as a physical host rather than a container.

- MacVlan Network should only be used in special cases and not by default.

- Isolating networking between containers can be achieved by using different networks like bridge Network or MacVlan Network.

Create networking isolation in Docker using Bridge networks

- You can create your own Bridge networking in Docker by using the 'docker network create' command

- When running a container, specify the bridge network using the '--network' flag and the name of the secure network

Multi-stage build in Docker allows you to build your container in multiple stages, resulting in smaller image sizes.

- The basic idea is to copy artifacts from one stage to another to only include the necessary dependencies for the final image.

- It is useful in scenarios where you have a multi-tier application with different dependencies for each tier.

Using multi-stage builds in Docker can significantly reduce image size.

- The concept of multi-stage builds allows you to optimize the size of Docker images by separating the build and runtime dependencies.

- By copying only the necessary binaries or executables into the final stage and installing only the required runtime in that stage, the image size can be reduced from 1GB to around 200-300MB.

Docker digitalized images are lightweight and minimalistic, reducing resource consumption and improving security.

- Digitalized images remove unnecessary files and commands, reducing space and resource usage.

- Using digitalized images improves application security by reducing exposure to security implications.

The Docker daemon is a single point of failure and can cause major challenges in production.

- Tools like Builder podman address this challenge by not having a single point of failure.

- Podman can also run the same Docker instructions and does not have the security implications of running as a root user.

Virtual machines are less likely to impact each other, while containers can be compromised if security is not considered properly.

- Using minimalist container images can reduce the chance of exposing containers to external vulnerabilities.

- Properly configuring networking is important to ensure the security and isolation of different applications within containers.

Configuring networking in Docker allows subcontainers to be secure.

- Creating a different Bridge Network for the login application.

- Using utilities like sync to scan container images for vulnerabilities before pushing them to production.