Interview › Kubernetes, Docker, Helm & Podman
What is a Docker volume versus a bind mount?
Kubernetes, Docker, Helm & Podman · Advanced level
Answer
A Docker volume is managed by the container engine and survives container replacement. A bind mount maps a specific host path into the container, which is useful for development but can leak host coupling into production.
Technical explanation
Volumes are portable across container replacements on the same engine; bind mounts are tied to a host path and host permissions.
In Kubernetes, avoid hostPath unless absolutely necessary because it couples Pods to node filesystem layout.
Container image quality affects supply chain, startup time, vulnerability surface, rollout reliability, and debugging workflows.
Prefer reproducible builds: pinned dependencies, small build context, deterministic Dockerfile order, non-root runtime, and immutable image references.
Understand the runtime boundary: an image is not a VM, and container isolation depends on kernel, namespaces, cgroups, capabilities, seccomp, and mounts.
Hands-on example
1. Create a tiny sample app and Dockerfile for this exercise: persist data with a Docker volume and compare it with a bind mount.
2. Build and inspect it with docker build or podman build, docker history, image inspect, and a vulnerability or size scan if available.
3. Run it locally with explicit env vars, ports, user, volumes, and signal tests depending on the question.
4. Convert the final runtime assumptions into Kubernetes fields such as image, command, args, ports, securityContext, probes, and volumeMounts.
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More Kubernetes, Docker, Helm & Podman interview questions
- What is Kubernetes, and what problem does it solve over running containers manually?
- Explain the Kubernetes control plane components (API server, etcd, scheduler, controller manager).
- What runs on a worker node (kubelet, kube-proxy, container runtime)?
- What is a Pod, and why does Kubernetes schedule Pods rather than containers?
- What is the difference between a Pod, a ReplicaSet, and a Deployment?
- How does a Deployment perform a rolling update, and how do maxSurge and maxUnavailable work?
- How do you roll back a Deployment, and how does Kubernetes track revisions?
- What is a Service, and what are the types (ClusterIP, NodePort, LoadBalancer, ExternalName)?