CODEWITHSUNDEEP
kubernetesconfigmap
OLA
OLA

Reputation: 59

Kubernetes: use environment variable/ConfigMap in PersistentVolume host path

Does anyone know if is it possible to use environment variable or ConfigMap in hostPath of PersistentVolume? Found that it's possible with Helm, envsubst etc. But I want to use only Kubernetes functions

I need to create a volume that will have a not static path.

Here is my PV:

apiVersion: v1
kind: PersistentVolume
metadata:
  name: some-pv
  labels:
    type: local
spec:
  storageClassName: manual
  capacity:
    storage: 2Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "${PATH_FROM_ENV}/some-path"

Upvotes: 1

Views: 1872

Answers (1)

Shai Katz
Shai Katz

Reputation: 1833

You can't do it natively, but a combination of a kubernetes Job that reads from a configmap can do that for you. We will create a Job with the proper RBAC permissions, this job uses kubectl image, reads the configmap, and passes it to the PV creation manifest.

Here are the manifests:

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  namespace: default
  name: pv-generator-role
rules:
- apiGroups: [""] # "" indicates the core API group
  resources: ["persistentvolumes"]
  verbs: ["create"]
- apiGroups: [""] # "" indicates the core API group
  resources: ["configmaps"]
  verbs: ["get"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: pv-geneartor-role-binding
  namespace: default
subjects:
- kind: ServiceAccount
  name: pv-generator-sa
  namespace: default
roleRef:
  kind: ClusterRole
  name: pv-generator-role
  apiGroup: rbac.authorization.k8s.io
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: pv-generator-sa
---
apiVersion: batch/v1
kind: Job
metadata:
  name: pv-generator
spec:
  template:
    spec:
      serviceAccountName: pv-generator-sa
      containers:
      - name: kubectl
        image: bitnami/kubectl
        command: 
        - sh
        - "-c"
        - |
          /bin/bash <<'EOF'
          cat <<EOF | kubectl apply -f -
          apiVersion: v1
          kind: PersistentVolume
          metadata:
            name: some-pv
            labels:
              type: local
          spec:
            storageClassName: manual
            capacity:
              storage: 2Gi
            accessModes:
              - ReadWriteOnce
            hostPath:
              path: $(kubectl get cm path-configmap -ojsonpath="{.data.path}")/some-path
          EOF
      restartPolicy: Never
  backoffLimit: 4
---
apiVersion: v1
kind: ConfigMap
metadata:
  name: path-configmap
  namespace: default
data:
  path: /mypath

Upvotes: 2

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