Ephemeral Volumes, Projected Volumes, and Volume Projections

Run kubectl get pods -o jsonpath='{.spec.volumes[*].name}' across a production namespace and count: most of those volumes are not PersistentVolumes at all. They are emptyDir scratch space, configMap mounts, projected service account tokens, downward API metadata. The ephemeral half of Kubernetes storage is what Pods actually mount most often, and the CKA exam (Storage domain, 10%) expects you to write all of it from memory.

The previous lesson covered PV-backed storage, access modes, and reclaim policies. This lesson covers the rest: emptyDir, configMap and secret mounts, the downward API, projected volumes that merge multiple sources, and generic ephemeral volumes that give you PVC-backed storage with Pod-scoped lifecycle.