Top 20 Docker Interview Questions and Answers

Get answers to the top 20 most common questions about Docker, including topics such as installation, containers, images, networks, and more. Learn how to build, push, and pull images, as well as how to run, stop, and remove containers.

1. What is Docker?
   Docker is a tool designed to make it easier to create, deploy, and run applications by using containers. Containers allow a developer to package up an application with all of the parts it needs, such as libraries and other dependencies, and ship it all out as one package.
   
2. What is a Docker container?
   A Docker container is a lightweight, standalone, and executable package of software that includes everything needed to run the application. It includes the application itself, as well as the libraries and dependencies it requires to run.
   
3. What is a Docker image?
   A Docker image is a lightweight, stand-alone, executable package that includes everything needed to run a piece of software, including the application itself, as well as libraries and dependencies.
   
4. What is Docker Compose?
   Docker Compose is a tool for defining and running multi-container Docker applications. It allows you to use a single configuration file to define and run multiple containers, making it easier to manage complex applications.
   
5. What is Docker Swarm?
   Docker Swarm is a native clustering and scheduling tool for Docker containers. It allows you to create a cluster of Docker engines and schedule containers to run on them.
   
6. How do I install Docker?
   To install Docker, you will need to follow the instructions for your specific operating system. You can find installation instructions for various operating systems at the following link: https://docs.docker.com/engine/install/
   
7. How do I run a Docker container?
   To run a Docker container, use the following command:
   docker run <image_name>
   
8. How do I list all Docker containers?
   To list all Docker containers, use the following command:
   docker container ls -a
   
9. How do I stop a Docker container?
   To stop a Docker container, use the following command:
   docker stop <container_name>
   
10. How do I remove a Docker container?
    To remove a Docker container, use the following command:
    docker rm <container_name>

11. How do I build a Docker image?
    To build a Docker image, you will need to create a Dockerfile that defines the steps required to build the image. Then, use the docker build command to build the image, like this.
    docker build -t <image_name> .

12. How do I push a Docker image to a registry?
    To push a Docker image to a registry, you will need to first log in to the registry using the docker login command. Then, use the docker push command to push the image to the registry, like this:
    docker push <image_name>
    
13. How do I pull a Docker image from a registry?
    To pull a Docker image from a registry, use the docker pull command, like this:
    docker pull <image_name>
    
14. How do I create a Docker network?
    To create a Docker network, use the docker network create command, like this:
    docker network create <network_name>
    
15. How do I connect a Docker container to a network?
    To connect a Docker container to a network, use the –network flag when starting the container, like this:
    docker run –network <network_name> <image_name>
    
16. How do I see the logs for a Docker container?
    To see the logs for a Docker container, use the docker logs command, like this:
    docker logs <container_name>
    
17. How do I see the processes running inside a Docker container?
    To see the processes running inside a Docker container, use the docker top command, like this:
    docker top <container_name>
    
18. How do I access a running Docker container?
    To access a running Docker container, use the docker exec command, like this:
    docker exec -it <container_name> bash
    This will open a new terminal inside the running container, allowing you to run commands and interact with the container.
    
19. How do I commit changes to a Docker container?
    To commit changes to a Docker container, you will need to create a new image from the container. To do this, use the docker commit command, like this:
    docker commit <container_name> <image_name>
    This will create a new image with the changes you made to the container.
    
20. How do I save changes to a Docker image?
    To save changes to a Docker image, you will need to create a new image from the changes. To do this, you can use the docker commit command, as described above. Alternatively, you can build a new image using a Dockerfile, which allows you to automate the process of creating an image.
    
21. How do I create a Docker volume?
    To create a Docker volume, use the docker volume create command, like this:
    docker volume create <volume_name>
    
22. How do I attach a Docker volume to a container?
    To attach a Docker volume to a container, use the -v flag when starting the container, like this:
    docker run -v <volume_name>:<mount_point> <image_name>
    This will attach the volume to the specified mount point inside the container.
    
23. How do I copy files between a Docker container and the host machine?
    To copy files between a Docker container and the host machine, you can use the docker cp command. To copy a file from the container to the host machine, use the following command:
    docker cp <container_name>:<file_path> <host_destination>
    To copy a file from the host machine to the container, use the following command:
    docker cp <file_path> <container_name>:<destination>
    
24. How do I set environment variables in a Docker container?
    To set environment variables in a Docker container, you can use the -e flag when starting the container, like this:
    docker run -e <VAR_NAME>=<value> <image_name>
    
25. How do I expose a port in a Docker container?
    To expose a port in a Docker container, you can use the -p flag when starting the container, like this:
    docker run -p <host_port>:<container_port> <image_name>