Top Docker Interview Questions (2026)

Docker is essential for backend and DevOps roles. Also prepare Kubernetes Interview Questions.

1. What is Docker?

Docker is a containerization platform that allows applications to run in isolated environments.

2. What is a Container?

A lightweight, standalone package that includes everything needed to run an app.

3. Docker Image vs Container?

Image is a blueprint; container is a running instance.

4. What is Dockerfile?

FROM golang:1.22
WORKDIR /app
COPY . .
RUN go build -o main .
CMD ["./main"]

5. What are Docker Volumes?

Volumes persist data outside containers.

6. What is Docker Networking?

Allows communication between containers.

7. What is Docker Compose?

Defines multi-container applications.

version: "3"
services:
  app:
    build: .
  db:
    image: mongo

8. What is Layer Caching?

Improves build speed using cached layers.

9. What is Multi-stage Build?

Reduces image size using multiple build stages.

10. Docker vs VM?

Containers are lightweight; VMs include full OS.