Top 67 Docker Interview Questions & Answers (2026)

01 What is Docker? 02 What is a container? 03 What is a Docker image? 04 What is the difference between a container and a virtual machine? 05 What is a Dockerfile? 06 What is Docker Hub? 07 What is the docker run command? 08 What is the difference between CMD and ENTRYPOINT in Dockerfile? 09 What is a Docker volume? 10 What is Docker Compose? 11 What are Docker networking modes? 12 What is the difference between ADD and COPY in Dockerfile? 13 What is a Docker registry? 14 What is the purpose of .dockerignore? 15 What is docker-compose.yml structure? 16 What are Docker image layers? 17 What is the difference between docker stop and docker kill? 18 What is docker exec? 19 What is a Docker network? 20 What is docker-compose up vs docker-compose start? 21 What is the WORKDIR instruction in Dockerfile? 22 What is docker build and how does it work? 23 What is a multi-stage Dockerfile? 24 What are environment variables in Docker? 25 How do you list and manage Docker containers? 26 What are restart policies in Docker? 27 What is Docker Swarm? 28 What is the difference between EXPOSE and port publishing in Docker? 29 How do you reduce Docker image size? 30 What is the USER instruction in Dockerfile? 31 What is the HEALTHCHECK instruction in Dockerfile? 32 What is docker inspect? 33 What is docker pull and docker push? 34 What is the difference between image tags and digests? 35 What is docker system prune?

01 What is Docker BuildKit and why is it better? 02 How do you handle secrets in Docker? 03 What is Docker Compose override and multiple Compose files? 04 How does Docker handle logging? 05 What is Docker context? 06 What is the Docker socket and why is exposing it dangerous? 07 What is container orchestration and what problems does it solve? 08 What is Kubernetes and how does it relate to Docker? 09 What is a Docker registry mirror? 10 What is container security scanning? 11 What is Docker in Docker (DinD)? 12 What is the difference between Docker and Podman? 13 What is the principle of least privilege in Docker? 14 What is Docker Compose profiles? 15 What is the difference between COPY and RUN in terms of Docker layers? 16 What are Docker labels? 17 What is init in Docker containers? 18 What is container resource limiting in Docker? 19 What is a Docker healthcheck and how does it differ from a liveness probe? 20 What are Docker build arguments (ARG)? 21 What is Docker content trust?

01 What is containerd and how does it relate to Docker? 02 What are Linux namespaces and cgroups, and how do they enable containers? 03 What is overlay2 storage driver and how does it work? 04 What is Docker Buildx and multi-platform builds? 05 What is Docker networking at a deep level (iptables, veth pairs)? 06 What is the difference between Docker Swarm services and Docker Compose services? 07 What is the OCI (Open Container Initiative) and why does it matter? 08 What is a distroless container image? 09 What is Dockerfile heredoc syntax and when would you use it? 10 How do you implement zero-downtime deployments with Docker? 11 What is Compose watch and how does it improve developer experience?