Ephemeral Volumes

Ephemeral Volumes

Ephemeral and Host-Path Volumes

A volume is declared in spec.volumes and mounted by any of the Pod's containers. An emptyDir is created empty when the Pod lands on a node and deleted when the Pod leaves it; containers restart around it:

An emptyDir outlives container restarts, not the PodShell

kubectl apply -f - >/dev/null <<'EOF'
apiVersion: v1
kind: Pod
metadata: { name: scratch }
spec:
  containers:
  - name: logger
    image: localhost:33500/booknest-web:1.3
    command: [sh, -c, 'date +%T >> /cache/starts; echo $(cat /cache/starts); sleep 5']
    volumeMounts: [{ name: cache, mountPath: /cache }]
  volumes: [{ name: cache, emptyDir: { sizeLimit: 64Mi } }]
EOF
sleep 30; kubectl get pod scratch; kubectl logs scratch
kubectl delete pod scratch --now

Output

NAME      READY   STATUS    RESTARTS      AGE
scratch   1/1     Running   2 (19s ago)   31s
16:15:00 16:15:06 16:15:25
pod "scratch" deleted from booknest namespace

The logger exits after five seconds and restarts with back-off, and its latest start found the earlier timestamps. emptyDir suits caches and files shared between containers (medium: Memory uses tmpfs). A hostPath volume mounts a node directory: it ties the Pod to one node and can expose the node, so the Baseline Pod Security Standard (Pod Security and Policies) forbids it. Node agents (Common DaemonSet Workloads) use it; applications should not.

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