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Volumes

By · Reviewed & last updated · Part of Kubernetes Tutorial

Volumes give containers storage that outlives the container’s lifecycle. The modern flow: PersistentVolumeClaim + StorageClass; the cluster dynamically provisions a backing PersistentVolume on demand.

PVCs, StatefulSet templates, ephemeral

EXAMPLE
# 1) StorageClass — defines HOW volumes are provisioned
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata: { name: gp3 }
provisioner: ebs.csi.aws.com
parameters:
    type:       gp3
    iops:       3000
    throughput: 125
reclaimPolicy: Retain          # don't delete the underlying EBS volume on PVC delete
allowVolumeExpansion: true

# 2) PVC — your app's request for storage
apiVersion: v1
kind: PersistentVolumeClaim
metadata: { name: db-data, namespace: ops }
spec:
    accessModes: [ReadWriteOnce]
    resources:
        requests: { storage: 50Gi }
    storageClassName: gp3

# 3) Mount it in a Pod
spec:
    containers:
        - name: db
          image: postgres:16
          volumeMounts:
              - name:      data
                mountPath: /var/lib/postgresql/data
    volumes:
        - name: data
          persistentVolumeClaim: { claimName: db-data }

# 4) StatefulSet — one PVC per replica via volumeClaimTemplates
apiVersion: apps/v1
kind: StatefulSet
metadata: { name: db }
spec:
    serviceName: db-headless
    replicas: 3
    selector: { matchLabels: { app: db } }
    template:
        metadata: { labels: { app: db } }
        spec:
            containers:
                - name: db
                  image: postgres:16
                  volumeMounts:
                      - name: data
                        mountPath: /var/lib/postgresql/data
    volumeClaimTemplates:
        - metadata: { name: data }
          spec:
              accessModes: [ReadWriteOnce]
              resources: { requests: { storage: 100Gi } }
              storageClassName: gp3

# 5) Ephemeral volumes — gone with the Pod, no PVC needed
spec:
    volumes:
        - name: scratch
          emptyDir: { sizeLimit: 1Gi }              # cleared on Pod restart
        - name: in-mem
          emptyDir: { medium: Memory, sizeLimit: 64Mi }
        - name: cfg
          configMap: { name: app-config }
        - name: dl
          downwardAPI:
              items:
                  - path: pod-name
                    fieldRef: { fieldPath: metadata.name }

# 6) Inspect
kubectl get sc
kubectl get pvc -n ops
kubectl get pv
kubectl describe pvc db-data -n ops

Why it matters

PVCs survive Pod restarts; PVs survive PVC deletes (with Retain). Delete reclaim is friendly for dev clusters; Retain is mandatory for anything you don’t want to accidentally lose.

Tip: Tweak the snippet with Try it Yourself », then sit the quiz at the bottom of the page.

Example

Example
# emptyDir, hostPath, configMap, secret, persistentVolumeClaim.
Try it Yourself »

Discussion

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