21 Most asked Docker Interview Questions
We will start this topic by explaining what a docker is all about.
A docker is a tool that does a lot in helping developers create and control their applications in a not-difficult and well-structured way.
That’s not all, for your application to reach its destination, you will need to add it into the container and transport.
In this article, we have listed some important docker interview questions for you.
1. Question: What do you know about the components of docker architecture
Answer: The three important components of docker architecture are explained in details below:
- Host: Containers, Daemon, and images are located in this component. The Docker Daemon creates a link that is connected with the Registry. Docker container holds the Docker Daemon.
- Registry: Docker images are stored by this Registry.
- Clients: This component sets up a communication with Docker Host by running operations.
2. Question: Tell us what you know about Docker Container Lifestyle
Answer: The lifestyle is a process that starts with creating, running, Pausing, unpausing, Starting, Stopping, Restarting, Killing and finally destroying the container.
3. Question: What do you understand by Namespaces in Docker
Answer: A namespace is a technology for providing containers.
A collection of namespaces is created immediately after a container is started. A container is limited to function only in just a Namespace.
4. Question: Docker Objects mean what?
Answer: Docker Objects are called Docker Images, Services and Containers.
- Images: A read-only template containing instructions that can be used to create containers
- Containers: Image’s runnable instance
- Services: Containers are scaled across a variety of Docker Daemons through this.
5. Question: What are the uses of Dockerfile
Answer: A set of instructions passed from a Dockerfile on Docker helps in the building process of an image.
Users can call on any commands on the command line of a Dockerfile for assembly of images.
6. Question: Will you lose all of your work if you mistakenly exit a container?
Answer: No, this won’t make you to lose any information, data or any other parameters.
You will only lose your work if you issue a certain command to delete the container.
7. Question: Instead of using default YAML, is it possible to make use of any other files for composing?
Answer: Yes, you can make use of any file of your choice during composing without a problem.
8. Question: Is there any difference between a registry and a repository?
Answer: A Docker registry hosts and distributes images whereas a Docker repository is the collection of similar Docker images.
They both have different tags but similar names.
9. Question: Explain the difference between the commands “Docker run” and “Docker create”
Answer: The major difference between the two is that “Docker run” container is created in the “stop” state.
10. Question: Explain CMD and ENTRYPOINT in a Dockerfile?
Answer: CMD and ENTRYPOINT instructions in a Dockerfile deal with which command is going to be executed during the process of running a container.
There are some rules that must be obeyed for these two to work out together:
- A minimum of one command from CMD or ENTRYPOINT must be specified by Dockerfile
- The ENTRYPOINT must be defined as you use the container as an executable
- CMD is overridden anytime you run the container with another argument
11. Question: What can you say about Visualization?
Answer: Because of visualization you are able to run two different operating systems on your hardware, a primary OS and a guest OS. The primary OS is refered to as the administrator.
Paravirtualization, Emulation and Container-based virtualization are important types of Visualization.
12. Question: Briefly talk on the workflow of Docker Usage
Answer:
- Everything starts with Dockerfile, the source code
- The next thing is the building the image of the container by the Dockerfile
- Redistribution of the image occurs afterward through the use of the registry
- Containers can be run by this image
13. Question: Name some important Docker commands
Answer: The commands below gives the following Docker commands –
- Build: to develop an image file for Docker
- Create: building a new container
- Kill: for killing a container
- Dockerd: for launching Docker daemon
- commit: for building a new image from the changes of the container
14: Question: What do you know about Docker Swarm?
Answer: Docker containers can be clustered and scheduled by a native tool called Docker Swarm.
Users can easily establish and manage a bunch of nodes in Docker or a solitary Virtual System (VS) through the use of Docker Swarm.
15. Question: Mention the functionalities and applications of Docker
Answer: The implementation of Docker comes with some functionalities and applications given below –
- Application isolation permission
- It limits the use of many servers in the form of containerization
- It makes configuration easy
- Important functionalities created by debugging capabilities is amplified by it
- At the OS level, it brings about quick deployment
16. Question: Which is the best for Docker Container, Stateless or Stateful application?
Answer: It is advisable you make use of Stateless applications ahead of Stateful ones because an image can be reused for distinct scenarios for Stateless applications.
When dealing with Docker Containers, it is not difficult in scaling a Stateless application than that of a Stateful application.
17. Question: Is it possible to remove a paused container from Docker?
Answer: No you can’t. To remove a paused container, the container has to be in the stop state before it can be possible.
18. Question: Is it possible for a container to restart by itself?
Answer: No you can’t have a container restarting by itself.
19. Question: What is the limit of containers that can be run per host?
Answer: There is no limit as you can use as many as you want per host. storage space, CPU and memory of containers are what you need to consider when deciding the numbers you want per host.
Application size is also a good factor, we all know containers as lightweight and very reliable on the host operating system.
20. Question: Let’s say you have an application that has many dependant services. Will docker-compose wait for the current container to be ready to move to the running of the next service?
Answer: Yes, the reason is that the dependency order is the common way Docker composes runs. Depends_on, links, volumes_from, etc. are specialized dependencies.
21. Question: How can one delete an image from the local storage system?
Answer: Use $ docker rmi <container.id> to delete an image from a local storage system.
Conclusion
The market these days has been continually changing, businesses will have to adapt to these changes for them to still be in the game.
Better software delivery, faster scaling of systems and new technologies adaptation, etc. are what keep them in balance.
Docker comes in here with its importance and gives these companies boosting support to remain active in the race.
These Docker interview questions are some of the useful ones you can carefully study and prepare for anything relating to Docker.