K
Q

How to let Kubernetes PetSet use existing Persistent Volumes?

10/28/2016

As part of the PetSet definition, the volumeClainTemplates are defined for Kubernetes to dynamically generate Persistent Volume Claims. For example:

  volumeClaimTemplates:
  - metadata:
      name: datadir
      annotations:
        volume.alpha.kubernetes.io/storage-class: anything
    spec:
      accessModes: [ "ReadWriteOnce" ]
      resources:
        requests:
          storage: 24Gi

However, I already has a few of the Persistent Volumes defined:

#kubectl get pv    
NAME      CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS    CLAIM                 REASON    AGE 
pv-1-rw   24Gi       RWO           Retain          Bound     rnd/pvc-1-rw             1h
pv-2-rw   24Gi       RWO           Retain          Bound     rnd/pvc-2-rw             6d
pv-3-rw   24Gi       RWO           Retain          Bound     rnd/pvc-3-rw             6d
...

I would like the Kubernetes to choose the persistent volumes from the existing ones rather than dynamically creating new ones.

I'm using Kubernetes 1.4.3. Does anyone know how to do that?

-- k8s-in-action
kubernetes

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3 Answers

10/14/2019

A simple solution is to manually create the PVCs and the PVs. If your PVC are named html-nginx-0 to html-nginx-N the volume claim template will use them instead of creating new ones and everything will be fine.

You can use kind https://kind.sigs.k8s.io/, where dynamic volume provisionning is enabled in order to get the yaml examples for PVs and PVCs. And adapt PVs to your storage.

-- fjammes
Source: StackOverflow
3/14/2018

Here's how to use a select a volume by label

volumeClaimTemplates:
- metadata:
    name: data
spec:
    accessModes: [ "ReadWriteOnce" ]
    selector: 
    matchLabels:
        data-label: database-1
-- Jonathan
Source: StackOverflow
10/28/2016

volumeClaimTemplates is an array of PersistentVolumeClaim. You can try to define them using selector and label existing volumes somehow, i.e.:

kind: PersistentVolume
apiVersion: v1
metadata:
  name: pv0001
  labels:
    foo: foo
    bar: bar
spec:
  accessModes:
    - ReadWriteOnce
  capacity:
    storage: 5Gi
  hostPath:
    path: /data/pv0001/
---
kind: PersistentVolume
apiVersion: v1
metadata:
  name: pv0002
  labels:
    foo: foo
    bar: bar
spec:
  accessModes:
    - ReadWriteOnce
  capacity:
    storage: 5Gi
  hostPath:
    path: /data/pv0002/
---
kind: Service
apiVersion: v1
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  ports:
    - port: 80
  selector:
    app: nginx
---
kind: PetSet
apiVersion: apps/v1alpha1
metadata:
  name: nginx
spec:
  serviceName: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
        - name: nginx
          image: gcr.io/google_containers/nginx-slim:0.8
          ports:
            - containerPort: 80
          volumeMounts:
            - name: html
              mountPath: /usr/share/nginx/html
  volumeClaimTemplates:
    - metadata:
        name: html
      spec:
        accessModes:
          - ReadWriteOnce
        resources:
          requests:
            storage: 5Gi
        selector:
          matchLabels:
            foo: foo
            bar: bar

Of course, volumes must be available for bounding.

$ kubectl get pvc html-nginx-0
NAME           STATUS    VOLUME    CAPACITY   ACCESSMODES   AGE
html-nginx-0   Bound     pv0002    5Gi        RWO           1m
$ kubectl get pv
NAME      CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS      CLAIM                  REASON    AGE
pv0001    5Gi        RWO           Retain          Available                                    2m
pv0002    5Gi        RWO           Retain          Bound       default/html-nginx-0             2m
-- Maciej Strzelecki
Source: StackOverflow