Interview Prep
Docker interview questions and how to answer them
Docker questions show up in DevOps, platform, and backend interviews. They test whether you understand containers conceptually and can explain how they fit into a deployment pipeline.
PrepVault tracks your prep and maps the JD to what you need to study. Free to start.
Docker interview questions and how to answer them
How do you use docker exec to debug a running container?
run command in container. interactive shell. debug runtime environment. not image modification
What is Docker layer caching, and how does instruction ordering affect build speed?
layers reused from cache. earlier changes invalidate later layers. copy manifests first. stable before changing
What are the main Docker container lifecycle states?
created. running. exited. removed
How do minimal base images improve Docker security?
smaller attack surface. fewer packages. compatibility trade-offs. debugging trade-offs
What is the difference between docker compose up and docker compose run?
up starts services. run creates one-off container. exec enters running container. ports may differ
How should executives understand the business value of investing in Docker build optimization?
developer productivity. lower security risk. reliable releases. shared platform leverage
What problem does Docker Compose solve, and what are its key concepts?
single YAML defines all services. automatic shared network by service name. docker compose up/down lifecycle. volumes and env vars per service
How should you apply least privilege to Docker containers?
non-root. minimal mounts. drop capabilities. scoped secrets
How do you design a production container image build pipeline?
Build reproducibly. Scan and tag immutably. Generate SBOM or provenance. Promote same digest
What is a Dockerfile and what are its most common instructions?
FROM sets base image. each instruction = one layer. CMD vs ENTRYPOINT distinction. EXPOSE is documentation not port binding
Common mistakes
- Confusing images and containers
- Vague on networking and volumes
- No sense of how it fits a deploy pipeline
What interviewers weigh
- Containers conceptually, not just commands
- How images and layers work
- Where Docker fits in deployment