Docker Interview Questions - 2

1.      What is Docker?

Ans: Docker is an open-source platform that allows you to create, deploy, and run applications in containers. Containers are lightweight, self-contained environments that include all the necessary dependencies and libraries for an application to run. Docker allows you to package an application and its dependencies into a single container, making it easy to move between development, testing, and production environments.

2.      What are the benefits of using Docker?

Ans: Some of the benefits of using Docker include:

·        Portability: Docker containers can run on any platform that supports Docker, making it easy to move an application between different environments.

·        Isolation: Docker containers isolate an application from the host system and other containers, which can reduce the risk of conflicts and improve security.

·        Scalability: Docker allows you to easily scale an application by running multiple instances of a container.

·        Efficiency: Docker allows you to use fewer resources than traditional virtualization, making it more efficient.

·        Versioning: Docker provides a way to version and rollback containers, making it easy to test and deploy new versions of an application.

3.      What are the differences between a Docker container and a virtual machine?

Ans: A Docker container is a lightweight, self-contained environment that includes all the necessary dependencies and libraries for an application to run, while a virtual machine is a full replica of a physical machine, including the operating system and all its dependencies. Containers share the host system's kernel and libraries, while virtual machines have their own kernel and libraries, which can make them more isolated but also heavier and more resource-intensive.

4.      How does Docker handle networking?

Ans: Docker uses a feature called container networking to handle networking. Container networking allows containers to communicate with each other and with the host system using virtual networks. Docker provides several built-in network drivers, such as bridge, host, and overlay, that can be used to configure the network settings of a container.

5.      How does Docker handle storage?

Ans: Docker uses a feature called container storage to handle storage. Container storage allows containers to mount file systems from the host system or other containers. Docker provides several built-in storage drivers, such as aufs, overlay2, and devicemapper, that can be used to configure the storage settings of a container.

6.      How does Docker handle security?

Ans: Docker provides several features that can be used to improve security, such as user namespaces, which allow you to run a container as a non-root user, and seccomp, which allows you to configure the system calls that a container can make. Docker also provides a feature called AppArmor, which allows you to configure the permissions of a container.

7.      How does Docker handle scaling?

Ans: Docker allows you to scale an application by running multiple instances of a container. You can use Docker Compose to define a multi-container application and then use the docker-compose up command to start multiple instances of each container. You can also use a container orchestration tool like Kubernetes or Docker Swarm to manage the scaling of your application.

8.      How does Docker handle image management?

Ans: Docker uses a feature called image management to handle image management. Image management allows you to create, distribute, and manage images. Docker provides a command-line tool called docker that can be used to create, push, and pull images. Docker also provides a service called Docker Hub, which allows you to store and share images.

9.      How does Docker handle container orchestration?

Ans: Docker provides a built-in orchestration feature called Docker Swarm that can be used to manage the scaling, availability, and fault-tolerance of a multi-container application. Docker Swarm provides features like load balancing, service discovery, and rolling updates that can be used to manage the deployment and scaling of an application.

10.   How does Docker handle container logging?

Ans: Docker allows you to configure the logging of a container using the --log-driver and --log-opt options. The --log-driver option can be used to specify the logging driver that should be used for a container, and the --log-opt option can be used to specify the options for the logging driver. Docker provides several built-in logging drivers, such as json-file and syslog, that can be used to configure the logging of a container.

11.   How does Docker handle container data?

Ans: Docker allows you to manage the data of a container using volumes. Volumes are a way to store data outside of a container's filesystem. Volumes can be created, mounted, and managed using the docker volume command. They can also be defined in the docker-compose.yml file and managed using docker-compose. This allows for data to persist even if the container is deleted and makes it easier to share data between containers.

12.   How does Docker handle environment variables?

Ans: Docker allows you to pass environment variables to a container using the -e option of the docker run command. Environment variables can also be defined in a .env file and passed to the container using docker-compose. This allows for easy configuration of the container and makes it easier to manage different environments.

13.   How does Docker handle container updates?

Ans: Docker allows you to update a container by pulling the latest image and restarting the container. This can be done using the docker pull and docker restart commands. Docker also provides the docker-compose up --build command which allows to rebuild the images and restart the containers. This allows for easy and efficient management of updates.

14.   What is a Dockerfile and how is it used?

Ans: A Dockerfile is a script that contains instructions for building a Docker image. It consists of a set of commands and arguments that are executed in order to create an image. The commands in the Dockerfile include instructions for setting environment variables, installing software, and configuring the container. Once the Dockerfile is created, the docker build command can be used to create an image from it. This allows for automated, repeatable image creation process.

15.   How does Docker handle container logging?

Ans: By default, Docker sends container logs to the container's stdout and stderr. These logs can be accessed using the docker logs command. Docker also supports sending container logs to external log management tools, such as syslog, journald, and gelf, by configuring the container's log driver. This allows for centralized logging and better log management.

16.   How does Docker handle resource allocation?

Ans: Docker allows you to configure resource allocation for containers using options like --memory, --cpus, and --cpu-shares. These options can be used to specify the amount of memory, CPU, and CPU shares that a container can use. By using these options, you can ensure that containers have the resources they need to run correctly and that resources are not over-allocated.

17.   How does Docker handle container health checks?

Ans: Docker allows you to configure health checks for containers using the HEALTHCHECK instruction in a Dockerfile or the healthcheck key in the docker-compose.yml file. Health checks specify a command that Docker runs inside the container to check its health, and a set of parameters to determine if the container is healthy or not. This allows you to quickly detect and respond to issues with a container.

18.   What is a Docker image?

Ans: A Docker image is a pre-built, ready-to-run container that includes all the necessary dependencies and libraries for an application to run. An image is built using a Dockerfile, which contains instructions for building the image. Once an image is built, it can be run as a container using the docker run command.

19.   What is a Docker registry?

Ans: A Docker registry is a service that allows you to store and distribute Docker images. The Docker Hub is the default registry and is provided by Docker, but there are also other registries available like the Azure Container Registry, Google Container Registry and others. These registries allows you to store and distribute your own images, as well as to download images from other users.