Docker interview questions, ranked by how often they're asked.

We read 11 of the most widely used Docker interview guides and counted which questions each one includes. 14 questions appear in at least 8 of them. Every question has a model answer written for this course, likely follow-ups, and a link to the lesson that teaches it.

How this list was made

In November 2026 we collected every question from the guides below and grouped questions that ask the same thing in different words. A question's frequency is the number of guides that include it: ●●●● means 8 or more of 11, ●●● 5 to 7, ●● 3 to 4, ● fewer. Guides aren't interviews, so treat it as a strong signal of what interviewers draw on, not a record of real interviews.

Questions marked our pick appear in few guides but come up in real work and in senior interviews, so we added them. The answers are our own; none are copied from the guides.

InterviewBit 35 questions
GeeksforGeeks 71 questions
Simplilearn 35 questions
Edureka 50 questions
DataCamp 26 questions
Dataquest 35 questions
KodeKloud 30 questions
Linux Handbook 28 questions
Guru99 43 questions
Turing 110 questions
devops-exercises (GitHub) 143 questions

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54 OF 54 QUESTIONS

01
Junior11/11 guidesMust-knowConcept
What's the difference between an image and a container?
Basics
02
Junior11/11 guidesMust-knowConcept
What is a Dockerfile, and which instructions do you use most?
Images & Dockerfile
03
Junior11/11 guidesMust-knowConcept
Will you lose data when a container exits? How do you persist data?
Data
04
Junior11/11 guidesMust-knowConcept
What is Docker Compose, and how is it different from a Dockerfile?
Compose
05
Junior10/11 guidesMust-knowConcept
What's the difference between a container and a virtual machine?
Basics
06
Mid10/11 guidesMust-knowConcept
What network types does Docker provide, and how do containers talk to each other?
Networking
07
Junior9/11 guidesMust-knowConcept
Explain Docker's architecture. How do the client and the daemon communicate?
Basics
08
Junior9/11 guidesMust-knowConcept
What is a Docker registry, and how do you push and pull images?
Basics
09
Junior8/11 guidesMust-knowConcept
What's the difference between COPY and ADD?
Images & Dockerfile
10
Junior8/11 guidesMust-knowConcept
Can a container restart itself? Explain the restart policies.
Running containers
11
Junior8/11 guidesMust-knowConcept
How do you clean up unused images, containers and other Docker data? What's a dangling image?
Production & CI
12
Mid8/11 guidesMust-knowConcept
How does Docker isolate containers? Explain namespaces and cgroups.
Basics
13
Mid8/11 guidesMust-knowDesign
How do you secure Docker containers? Name the practices you'd apply.
Security
14
Mid8/11 guidesMust-knowConcept
What's the difference between Docker and Kubernetes? Where does Docker Swarm fit?
Production & CI
15
Junior7/11 guidesMust-knowConcept
What is Docker, and why do teams use it?
Basics
16
Junior7/11 guidesMust-knowConcept
Describe the lifecycle of a Docker container.
Running containers
17
Mid7/11 guidesMust-knowConcept
What's the difference between RUN, CMD and ENTRYPOINT?
Images & Dockerfile
18
Senior7/11 guidesMust-knowDesign
How do you manage secrets like passwords and API keys with Docker?
Security
19
Mid6/11 guidesMust-knowConcept
How do image layers and the build cache work, and how does instruction order matter?
Images & Dockerfile
20
Mid6/11 guidesMust-knowConcept
What are multi-stage builds, and why use them?
Images & Dockerfile
21
Mid6/11 guidesMust-knowDesign
How do you run the same image in development, staging and production?
Running containers
22
Mid6/11 guidesMust-knowConcept
What's the difference between volumes, bind mounts and tmpfs mounts?
Data
23
Mid6/11 guidesGood to knowConcept
How do you scale containers, and what limits how many can run on one host?
Production & CI
24
Mid6/11 guidesMust-knowDebugging
A container exits immediately after starting, or keeps restarting. How do you debug it?
Troubleshooting
25
Mid5/11 guidesMust-knowScenario
How do you reduce the size of a Docker image?
Images & Dockerfile
26
Mid5/11 guidesMust-knowConcept
How do you limit a container's CPU and memory, and what happens when it exceeds them?
Running containers
27
Mid5/11 guidesGood to knowConcept
What's the difference between docker exec and docker attach?
Running containers
28
Mid5/11 guidesGood to knowDesign
How does logging work in Docker, and how would you handle logs in production?
Running containers
29
Mid5/11 guidesMust-knowDesign
How would you use Docker in a CI/CD pipeline?
Production & CI
30
Junior4/11 guidesMust-knowConcept
What's the difference between docker stop and docker kill?
Running containers
31
Junior4/11 guidesGood to knowConcept
Can you write a Compose file in JSON instead of YAML?
Compose
32
Mid4/11 guidesMust-knowConcept
Why do containers need health checks, and what does Docker do with them?
Running containers
33
Mid4/11 guidesGood to knowConcept
How do you share data between containers?
Data
34
Mid4/11 guidesGood to knowScenario
How does a container reach a service running on the host machine?
Networking
35
Senior4/11 guidesGood to knowDesign
How would you monitor Docker containers in production?
Production & CI
36
Junior3/11 guidesMust-knowConcept
What's the difference between EXPOSE and publishing a port with -p?
Networking
37
Mid3/11 guidesGood to knowConcept
Walk me through what happens when you run docker run nginx.
Basics
38
Mid3/11 guidesGood to knowConcept
What's the difference between the exec form and the shell form of CMD?
Images & Dockerfile
39
Mid3/11 guidesGood to knowConcept
What is the build context, and what is .dockerignore for?
Images & Dockerfile
40
Mid3/11 guidesMust-knowConcept
Why is the latest tag considered risky? What should you use instead?
Images & Dockerfile
41
Mid3/11 guidesGood to knowConcept
How do you move an image to another machine without a registry? What's the difference between save/load and export/import?
Images & Dockerfile
42
Mid3/11 guidesMust-knowDebugging
Two containers can't reach each other by name. How do you debug it?
Networking
43
Mid3/11 guidesMust-knowScenario
With Compose, how do you make sure one container starts only after another is ready?
Compose
44
Mid3/11 guidesGood to knowScenario
How do you update a container to a new image version, or move it to a new server, without losing data?
Production & CI
45
Junior2/11 guidesGood to knowConcept
What's the difference between docker run, docker start and docker exec?
Running containers
46
Mid2/11 guidesGood to knowConcept
What's the difference between ARG and ENV?
Images & Dockerfile
47
Senior2/11 guidesGood to knowConcept
What is rootless Docker, and why would you use it?
Security
48
Senior2/11 guidesGood to knowDesign
Should you run databases and other stateful apps in Docker?
Production & CI
49
Mid1/11 guides · our pickMust-knowDebugging
A container keeps exiting with code 137. What does that mean, and how do you find the cause?
Troubleshooting
50
Mid1/11 guides · our pickGood to knowDebugging
Why does docker stop take ten seconds for some containers, and how do you fix it?
Troubleshooting
51
Mid1/11 guidesGood to knowDebugging
You rebuilt the image, but your code changes still aren't showing up. Why?
Troubleshooting
52
Senior1/11 guides · our pickGood to knowDebugging
Your Mac-built image fails on a server with exec format error. Why, and how do you build images for several CPU architectures?
Images & Dockerfile
53
Senior1/11 guides · our pickGood to knowDesign
Is Docker Compose suitable for production? What would you change in the file?
Compose
54
Senior1/11 guides · our pickMust-knowScenario
It works locally but fails in production. Where do you look?
Troubleshooting