20 Docker interview questions and answers
Docker interview questions and answers
1.What is Docker?
Answer: Docker is an open-source platform that allows
you to automate the deployment and management of applications using
containerization. It enables applications to run in isolated environments
called containers.
2.What is a container in Docker?
Answer: A container in Docker is a lightweight and
standalone executable package that encapsulates an application and its
dependencies. Containers provide isolation and portability, allowing
applications to run consistently across different environments.
3.What is the difference between a Docker container and a
virtual machine?
Answer: Docker containers share the host system's
kernel and resources, making them lightweight and faster to start compared to
virtual machines. In contrast, virtual machines emulate an entire operating
system, including its kernel, and have more overhead.
4.How do you create a Docker container?
Answer: Docker containers are created using Docker
images. To create a container, you run the docker run command followed by the
image name, which downloads the image (if not already available) and starts the
container.
5.What is a Dockerfile?
Answer: A Dockerfile is a text file that contains
instructions to build a Docker image. It defines the base image, application
code, dependencies, and any configuration needed to run the container.
6.How do you share data between a Docker container and
the host machine?
Answer: You can share data between a Docker container
and the host machine by using Docker volumes. Volumes provide a way to persist
and share data between the container and the host.
7.How do you scale Docker containers?
Answer: Docker provides a scaling feature called
Docker Swarm or Kubernetes. By using these orchestration tools, you can define
the desired number of replicas of a container and manage the distribution of
containers across a cluster of hosts.
8.How do you remove a Docker container?
Answer: To remove a Docker container, you can use the
command docker rm container_name or docker rm container_id. This command
removes the specified container from the host system.
9.What is Docker Compose?
Answer: Docker Compose is a tool that allows you to
define and manage multi-container Docker applications. It uses a YAML file to
define the services, networks, and volumes required for the application.
10.What is the purpose of Docker registry?
Answer: A Docker registry is a repository that stores
Docker images. It acts as a centralized location from which Docker can pull
images when creating containers. Docker Hub is a popular public Docker
registry.
11.How do you pass environment variables to a Docker
container?
Answer: You can pass environment variables to a
Docker container using the -e flag with the docker run command. For example,
docker run -e "VAR_NAME=value" image_name.
12.What is Docker swarm mode?
Answer: Docker swarm mode is a clustering and
orchestration feature built into Docker. It allows you to create and manage a
swarm of Docker nodes, forming a cluster for running and scaling containers
across multiple hosts.
13.How do you update a Docker image?
Answer: To update a Docker image, you need to rebuild
the image using an updated Dockerfile or pull the latest version from the
registry using the docker pull command. Then, you can recreate or update the
container using the new image.
14.What is the difference between Docker image and Docker
container?
Answer: A Docker image is a static, read-only file
that contains the application and its dependencies. A Docker container, on the
other hand, is an instance of an image that can be created, started, stopped,
and deleted.
15.How do you link containers in Docker?
Answer: In Docker, container linking is an older
method of connecting containers. However, it has been deprecated in favor of
using Docker networks. Docker networks allow containers to communicate with
each other using their service names as DNS names.
16.What is Docker volume?
Answer: Docker volume is a Docker feature that
provides persistent storage for containers. Volumes allow data to be stored
outside the container's lifecycle, ensuring that it is preserved even if the
container is deleted.
17.What is the purpose of the docker-compose up command?
Answer: The docker-compose up command is used to
start and run the services defined in a Docker Compose file. It creates and
starts the containers defined in the Compose file, along with any associated
networks and volumes.
18.How do you remove a Docker image?
Answer: To remove a Docker image, you can use the
command docker rmi image_name or docker rmi image_id. This command removes the
specified image from the local Docker image cache.
19.What is Docker Hub?
Answer: Docker Hub is a cloud-based registry service
provided by Docker. It allows users to store, distribute, and share Docker
images publicly or privately. Docker Hub is commonly used to host and discover
Docker images.
20.What are the differences between CMD and ENTRYPOINT in
a Dockerfile?
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