How can I do a docker -v in Kubernetes persistent volumes?

Question

I've successfully managed to create an NFS Persistent Volume and a Persistent Volume claim which when I run my deployment does what it's supposed to and mounts my apps data folder on the NFS volume. All good.

In docker there is the ability to run

-v <host dir>:<container dir>

How do I tell Kubernetes in my deployment not to use /kubernetes but to use /kubernetes/ for example?

The current working code is: nfs-pv.yaml

apiVersion: v1
kind: PersistentVolume
metadata:
  name: nfs-pv
spec:
  capacity:
    storage: 10Gi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Recycle
  storageClassName: nfs
  mountOptions:
    - hard
  nfs:
    path: /Dev1Partition1/kubernetes
    server: 192.168.40.202

nfs-pvc.yaml

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: nfs-pvc
spec:
  storageClassName: nfs
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 1Gi

The above works when I run the following deployment the data I expect appears in the Kubernetes folder I specified.

The Deployment looks like this deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    run: n8n-server
  name: n8n-deployment
spec:
  replicas: 1
  selector:
    matchLabels:
      run: n8n-deployment
  template:
    metadata:
      labels:
        run: n8n-deployment
    spec:
      volumes:
        - name: n8n-pv-storage
          persistentVolumeClaim:
            claimName: nfs-pvc
      containers:
      - image: 192.168.40.43:8081/dockercontainers/library/n8n:latest
        name: n8n-server
        volumeMounts:
          - mountPath: "/root/.n8n"
            name: n8n-pv-storage
      imagePullSecrets:
        - name: progercred

I tried adding under volumes:

hostPath: path: n8n (and /n8n) 
type: Directory

This throws up

spec.template.spec.volumes[0].persistentVolumeClaim: Forbidden: may not specify more than 1 volume type

spec.template.spec.containers[0].volumeMounts[0].name: Not found: "n8n-pv-storage"

I'm guessing because hostPath is for emptyDir?

Help?

Am i thinking about this right?

Where did you exactly add type: Directory ? In the PersistentVolume definition? If I understand well, you created a PersistentVolume mapped to a directory. And in your Deployment you want tell your pod to use another folder than the one mapped by the PersistentVolume ? — Flo
I'd like the deployment to create an application directory under the directory created by PersistentVolume.. from what i've been reading it seems that I've misunderstood PersistentVolume/NFS and I need to create a persistentvolume per App? would that be right? Seems a bit counterintuitive to not be able to create a volume of storage and then have access for the application to create an application specific folder on that blob of storage. — David Field

David Field David Field · Accepted Answer · 2021-06-18T10:57:01

The thing just about NONE of the "helpful" PV/PVC/NFS sites mention is subPath

So in the containers section of the deployment.yaml change so it has

volumeMounts:
  - mountPath: "/root/.n8n"
    name: n8n-pv-storage
    subPath: n8n

the subPath directive will create a subdirectory on the PV/PVC mountpoint of n8n which is persistent across nodes.

References:

How to mount the sub path of PVC to the specific path in container https://kubernetes.io/docs/concepts/storage/volumes/#using-subpath

How can I do a docker -v in Kubernetes persistent volumes?

1 Answers