55 Must-Know Docker Interview Questions and Answers 2024

Docker Fundamentals

1.
What is Docker, and how is it different from virtual machines?
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2.
Can you explain what a Docker image is?
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3.
How does a Docker container differ from a Docker image?
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4.
What is the Docker Hub, and what is it used for?
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5.
Explain the Dockerfile and its significance in Docker.
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6.
How does Docker use layers to build images?
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7.
What’s the difference between the COPY and ADD commands in a Dockerfile?
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8.
What’s the purpose of the .dockerignore file?
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9.
How would you go about creating a Docker image from an existing container?
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10.
In practice, how do you reduce the size of Docker images?
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11.
What command is used to run a Docker container from an image?
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12.
Can you explain what a Docker namespace is and its benefits?
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13.
What is a Docker volume, and when would you use it?
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14.
Explain the use and significance of the docker-compose tool.
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15.
Can Docker containers running on the same host communicate with each other by default? If so, how?
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Docker Networking

16.
Describe the different types of networks in Docker.
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17.
How do you create a Docker network?
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18.
How could you connect a container to a specific network?
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19.
Can you explain how Docker’s default bridge network differs from a user-defined bridge network?
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20.
How would you enable communication between Docker containers on different hosts?
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Docker Performance & Security

21.
How can resource constraints be applied to containers in Docker?
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22.
What are Docker security profiles, and how do they work?
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23.
Explain how you would scan a Docker image for vulnerabilities.
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24.
What is the purpose of a Docker Healthcheck?
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25.
Describe how you would handle sensitive data with Docker.
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Docker Orchestration

26.
What is Docker Swarm, and when would you use it?
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27.
Can you explain the difference between Docker Swarm and Kubernetes?
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28.
What is a Docker Stack?
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29.
How do you deploy an application stack in Docker Swarm?
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30.
How does Docker manage service replication and load balancing?
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Docker CLI & API

31.
What command would you use to list all running containers?
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32.
How can you stop all containers running on a host using a single command?
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33.
Can you describe how you would execute a command inside a running container?
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34.
What command would you use to display the logs of a container?
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35.
Explain how to copy files from a container to the local file system.
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36.
How can you inspect the details of a specific container via the CLI?
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37.
Describe how to use Docker’s REST API to start a container.
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Docker Best Practices

38.
Explain the importance of minimizing the number of layers in a Dockerfile.
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39.
Discuss the best practices for tagging Docker images.
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40.
When should you use a .dockerignore file?
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41.
Why is it advised to run only one process per container?
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42.
How should you handle logging in Docker containers?
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Docker Troubleshooting & Optimization

43.
How would you diagnose high CPU or memory usage in a container?
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44.
What steps would you take if a container consistently fails shortly after starting?
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45.
In what scenarios would you prune Docker objects, and how?
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46.
How can you monitor the performance of Docker containers?
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47.
What common issues might arise when working with Docker in a CI/CD pipeline?
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Docker Deployment & Integration

48.
How do you define a multi-container application with docker-compose?
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49.
What considerations must be made when deploying Docker containers in a production environment?
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50.
Explain the process of integrating Docker with a continuous integration system.
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51.
How would you migrate a traditional on-premise application to a Dockerized environment?
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52.
Describe how to automate the deployment of Docker containers using a CI/CD pipeline.
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Docker Storage & Persistence

53.
When would you use a bind mount over a volume?
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54.
How do you create a Docker volume, and what is its lifecycle?
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55.
What strategies would you use for data persistence in Docker clusters?
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55 Docker interview questions

What is Docker, and how is it different from virtual machines?

Can you explain what a Docker image is?

How does a Docker container differ from a Docker image?

What is the Docker Hub, and what is it used for?

Explain the Dockerfile and its significance in Docker.

How does Docker use layers to build images?

What’s the difference between the COPY and ADD commands in a Dockerfile?

What’s the purpose of the .dockerignore file?

How would you go about creating a Docker image from an existing container?

In practice, how do you reduce the size of Docker images?

What command is used to run a Docker container from an image?

Can you explain what a Docker namespace is and its benefits?

What is a Docker volume, and when would you use it?

Explain the use and significance of the docker-compose tool.

Can Docker containers running on the same host communicate with each other by default? If so, how?

Describe the different types of networks in Docker.

How do you create a Docker network?

How could you connect a container to a specific network?

Can you explain how Docker’s default bridge network differs from a user-defined bridge network?

How would you enable communication between Docker containers on different hosts?

How can resource constraints be applied to containers in Docker?

What are Docker security profiles, and how do they work?

Explain how you would scan a Docker image for vulnerabilities.

What is the purpose of a Docker Healthcheck?

Describe how you would handle sensitive data with Docker.

What is Docker Swarm, and when would you use it?

Can you explain the difference between Docker Swarm and Kubernetes?

What is a Docker Stack?

How do you deploy an application stack in Docker Swarm?

How does Docker manage service replication and load balancing?

What command would you use to list all running containers?

How can you stop all containers running on a host using a single command?

Can you describe how you would execute a command inside a running container?

What command would you use to display the logs of a container?

Explain how to copy files from a container to the local file system.

How can you inspect the details of a specific container via the CLI?

Describe how to use Docker’s REST API to start a container.

Explain the importance of minimizing the number of layers in a Dockerfile.

Discuss the best practices for tagging Docker images.

When should you use a .dockerignore file?

Why is it advised to run only one process per container?

How should you handle logging in Docker containers?

How would you diagnose high CPU or memory usage in a container?

What steps would you take if a container consistently fails shortly after starting?

In what scenarios would you prune Docker objects, and how?

How can you monitor the performance of Docker containers?

What common issues might arise when working with Docker in a CI/CD pipeline?

How do you define a multi-container application with docker-compose?

What considerations must be made when deploying Docker containers in a production environment?

Explain the process of integrating Docker with a continuous integration system.

How would you migrate a traditional on-premise application to a Dockerized environment?

Describe how to automate the deployment of Docker containers using a CI/CD pipeline.

When would you use a bind mount over a volume?

How do you create a Docker volume, and what is its lifecycle?

What strategies would you use for data persistence in Docker clusters?

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What’s the difference between the `COPY` and `ADD` commands in a Dockerfile?

What’s the purpose of the `.dockerignore` file?

Explain the use and significance of the `docker-compose` tool.

When should you use a `.dockerignore` file?

How do you define a multi-container application with `docker-compose`?