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How to resolve 'error validating data: ValidationError(Deployment.spec): unknown field volumeClaimTemplates in io.k8s.api.apps.v1.DeploymentSpec' error?

Cowrie
Cowrie
Dev @ Bswen

Problem

When installing an application in Kubernetes (k8s), you might encounter the following error:

Terminal window
root@launch-advisor:~# kubectl apply -f deployment-redis.yaml


error: error validating "deployment-redis.yaml": error validating data: ValidationError(Deployment.spec): unknown field "volumeClaimTemplates" in io.k8s.api.apps.v1.DeploymentSpec; if you choose to ignore these errors, turn validation off with --validate=false

The content of deployment-redis.yaml is:

deployment-redis.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: redis
  namespace: ns-bswen
  labels:
    app: redis
spec:
  selector:
    matchLabels:
      app: redis
  replicas: 1
  template:
    metadata:
      labels:
        app: redis
    spec:
      containers:
        - name: redis
          image: redis:6.0.9
          ports:
            - containerPort: 6379
          command: ["redis-server", "/etc/redis/redis.conf"]
          volumeMounts:
            - name: "redis-conf"
              mountPath: /etc/redis/redis.conf
              subPath: redis_conf
            - name: "redis-data"
              mountPath: "/var/lib/redis"
      volumes:
        - name: "redis-conf"
          configMap:
            name: "redis"
        - name: "redis-data"
          persistentVolumeClaim:
            claimName: redis-pvc
  volumeClaimTemplates:
    - metadata:
        name: redis-pvc
        annotations:
          volume.beta.kubernetes.io/storage-class: "my-nfs-storage"
      spec:
        accessModes: ["ReadWriteOnce"]
        resources:
          requests:
            storage: 100Mi

Environment

  • Docker: Server Version: 19.03.13
  • Kubectl version:
Terminal window
Client Version: version.Info{Major:"1", Minor:"17", GitVersion:"v1.17.3", GitCommit:"06ad960bfd03b39c8310aaf92d1e7c12ce618213", GitTreeState:"clean", BuildDate:"2020-02-13T18:06:54Z", GoVersion:"go1.13.8", Compiler:"gc", Platform:"darwin/amd64"}


Server Version: version.Info{Major:"1", Minor:"18", GitVersion:"v1.18.6", GitCommit:"dff82dc0de47299ab66c83c626e08b245ab19037", GitTreeState:"clean", BuildDate:"2020-07-15T16:51:04Z", GoVersion:"go1.13.9", Compiler:"gc", Platform:"linux/amd64"}

Reason

The error occurs because volumeClaimTemplates can ONLY be used in StatefulSets, not Deployments.

Solution

To resolve this issue, switch from Deployment to StatefulSet as follows:

statefulset-redis.yaml
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: redis
  namespace: ns-bswen
  labels:
    app: redis
spec:
  serviceName: redis
  selector:
    matchLabels:
      app: redis
  replicas: 1
  template:
    metadata:
      labels:
        app: redis
    spec:
      containers:
        - name: redis
          image: redis:6.0.9
          ports:
            - containerPort: 6379
          command: ["redis-server", "/etc/redis/redis.conf"]
          volumeMounts:
            - name: "redis-conf"
              mountPath: /etc/redis/redis.conf
              subPath: redis_conf
            - name: "redis-data"
              mountPath: "/var/lib/redis"
      volumes:
        - name: "redis-conf"
          configMap:
            name: "redis"
        - name: "redis-data"
          persistentVolumeClaim:
            claimName: redis-pvc
  volumeClaimTemplates:
    - metadata:
        name: redis-pvc
        annotations:
          volume.beta.kubernetes.io/storage-class: "my-nfs-storage"
      spec:
        accessModes: ["ReadWriteOnce"]
        resources:
          requests:
            storage: 100Mi

Summary

This post explained how to resolve the “unknown field volumeClaimTemplates” error in Kubernetes. The key takeaway is that volumeClaimTemplates is only supported in StatefulSets, not Deployments. By switching to a StatefulSet, you can ensure each pod replica gets its own unique storage, which is essential for applications like databases or distributed systems. Always choose the appropriate Kubernetes resource based on your application’s storage requirements.

Final Words + More Resources

My intention with this article was to help others who might be considering solving such a problem. So I hope that’s been the case here. If you still have any questions, don’t hesitate to ask me by email: Email me

Here are also the most important links from this article along with some further resources that will help you in this scope:

Oh, and if you found these resources useful, don’t forget to support me by starring the repo on GitHub!

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