NFS-Subdirectory Provider on Kubernetes

This storage provider allows you to use an NFS server like a native K8s storage provider, letting you to use mass storage for things like media or other large files. Why would this be useful? Things that you don't want to be replicated, for example, media (replicating 4.5TB can get expensive quick) or large data such as game servers! Of course, this does add a singe point of failure, but a lot less expensive than replicating data out to many nodes.

NFS-Subdirectory Provider requirements

Preparation

HelmRepository

We're going to install a helm chart from the NFS Subdirectory External Provisioner chart repository, so I create the following in my flux repo:

apiVersion: source.toolkit.fluxcd.io/v1beta1
kind: HelmRepository
metadata:
  name: nfs-subdir
  namespace: flux-system
spec:
  interval: 15m
  url: https://kubernetes-sigs.github.io/nfs-subdir-external-provisioner/

Note that I have shortened the name to nfs-subdir, a theme you will find running throughout.¹

Namespace

We need a namespace to deploy our HelmRelease and associated ConfigMaps into. Per the flux design, I create this example yaml in my flux repo at /bootstrap/namespaces/namespace-nfs-subdir.yaml:

apiVersion: v1
kind: Namespace
metadata:
  name: nfs-subdir

Kustomization

Now that the "global" elements of this deployment have been defined, we do some "flux-ception", and go one layer deeper, adding another Kustomization, telling flux to deploy any YAMLs found in the repo at /nfs-subdir. I create this example Kustomization in my flux repo:

apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
metadata:
  name: nfs-subdir
  namespace: flux-system
spec:
  interval: 15m
  path: nfs-subdir
  prune: true # remove any elements later removed from the above path
  timeout: 2m # if not set, this defaults to interval duration, which is 1h
  sourceRef:
    kind: GitRepository
    name: flux-system
    healthChecks:
    - apiVersion: apps/v1
      kind: Deployment
      name: nfs-subdir-external-provisioner
      namespace: nfs-suibdir

ConfigMap

Now we're into the nfs-subdir-specific YAMLs. First, we create a ConfigMap, containing the entire contents of the helm chart's values.yaml. Paste the values into a values.yaml key as illustrated below, indented 4 spaces (since they're "encapsulated" within the ConfigMap YAML). I create this example yaml in my flux repo:

apiVersion: v1
kind: ConfigMap
metadata:
  name: nfs-subdir-helm-chart-value-overrides
  namespace: nfs-subdir
data:
  values.yaml: |-  
    # <upstream values go here>

Values you will want to change from the default are:

    nfs:
      server: 
      path: 
      mountOptions: 

HelmRelease

Finally, having set the scene above, we define the HelmRelease which will actually deploy the provider into the cluster. I save this in my flux repo:

apiVersion: helm.toolkit.fluxcd.io/v2beta1
kind: HelmRelease
metadata:
  name: nfs-subdir
  namespace: nfs-subdir 
spec:
  chart:
    spec:
      chart: nfs-subdir-external-provisioner
      version: 4.X.X
      sourceRef:
        kind: HelmRepository
        name: nfs-subdir
        namespace: flux-system
  interval: 15m
  timeout: 5m
  releaseName: nfs-subdir-external-provisioner
  valuesFrom:
  - kind: ConfigMap
    name: nfs-subdir-helm-chart-value-overrides
    valuesKey: values.yaml # This is the default, but best to be explicit for clarity

Install the provider.

Commit the changes to your flux repository, and either wait for the reconciliation interval, or force a reconcilliation using flux reconcile source git flux-system. You should see the kustomization appear...

~ ❯ flux get kustomizations | grep nfs-subdir
nfs-subdir                      main@sha1:f1b8c5ad      False           True    Applied revision: main@sha1:f1b8c5ad
~ ❯

The helmrelease should be reconciled...

~ ❯  $ flux get helmreleases -n nfs-subdir
NAME        REVISION    SUSPENDED   READY   MESSAGE
nfs-subdir      4.0.18          False           True    Release reconciliation succeeded
~ ❯

And you should have a happy NFS-Subdirectory pod:

~ ❯ kubectl get pods -n nfs-subdir 
NAME                                              READY   STATUS    RESTARTS         AGE
nfs-subdir-external-provisioner-9cf9d78b5-6zd7r   1/1     Running   22 (4d11h ago)   105d
~ ❯

You can now use this new provider to use an external NFS server for storage.

How do I know it's working?

So the provisioner is running, but how do we know we can actually provision volumes?

Create PVC

Create a PVC, by running:

cat <<EOF | kubectl create -f -
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: nfs-subdir-pvc
spec:
  accessModes:
    - ReadWriteOnce
  storageClassName: nfs-client
  resources:
    requests:
      storage: 128Mi
EOF

Examine the PVC by running kubectl describe pvc nfs-subdir-pvc

Create Pod

Now create a pod to consume the PVC, by running:

cat <<EOF | kubectl create -f -
apiVersion: v1
kind: Pod
metadata:
  name: nfs-subdir-test
spec:
  containers:
  - name: volume-test
    image: nginx:stable-alpine
    imagePullPolicy: IfNotPresent
    volumeMounts:
    - name: nfs-subdir-rocks
      mountPath: /data
    ports:
    - containerPort: 80
  volumes:
  - name: nfs-subdir-rocks
    persistentVolumeClaim:
      claimName: nfs-subdir-pvc
EOF

Examine the pod by running kubectl describe pod nfs-subdir-test.

Clean up

Assuming that the pod is in a Running state, then nfs-subdir is working!

Clean up by running:

kubectl delete pod nfs-subdir-test
kubectl delete pvc nfs-subdir-pvc

Summary

What have we achieved? We have a storage provider that can use an NFS server as it's storage backend, useful for large files, such as media for the autopirate recipe!

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