Dynamic Provisioning of PVs
MicroShift deploys the hostpath provisioner as solution to provide persistent storage to pods. The hostpath provisioner pod mounts the /var/hpvolumes directory in order to provision volumes. It also has the ability to dynamically provision PVs when a PVC is created, and wait until a pod uses that specific PVC.
Let's see how to create a PVC so the hostpath provisioner creates the persistent volume for us.
Create a Persistent Volume Claim
MicroShift's hostpath provisioner creates a StorageClass named kubevirt-hostpath-provisioner by default.
The PVC manifest must reference this StorageClass using the storageClassName spec parameter and there should be an annotation pointing at the node where the PV is going to be created. This annotation is crucial if we want dynamic provisioning of PVs:
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: task-pv-claim
annotations:
kubevirt.io/provisionOnNode: ricky-fedora.oglok.net
spec:
storageClassName: kubevirt-hostpath-provisioner
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 3Gi
This manifest will create the following Persistent Volume Claim and a Persistent Volume located at /var/hpvolumes/.
$ oc get pvc
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
task-pv-claim Bound pvc-58a28c40-7726-4830-ba70-32d18188a8b4 39Gi RWO kubevirt-hostpath-provisioner 8m43s
$ oc get pv
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
pvc-58a28c40-7726-4830-ba70-32d18188a8b4 39Gi RWO Delete Bound default/task-pv-claim kubevirt-hostpath-provisioner 8m43s
$ ll /var/hpvolumes/
total 0
drwxrwxrwx. 1 root root 8 Apr 5 10:26 pvc-58a28c40-7726-4830-ba70-32d18188a8b4
For sake of clarity, we will instantiate a sample NGINX pod that mounts that volume:
apiVersion: v1
kind: Pod
metadata:
name: task-pv-pod
spec:
volumes:
- name: task-pv-storage
persistentVolumeClaim:
claimName: task-pv-claim
containers:
- name: task-pv-container
image: nginx
ports:
- containerPort: 80
name: "http-server"
volumeMounts:
- mountPath: "/usr/share/nginx/html"
name: task-pv-storage
Any HTML file located at /var/hpvolumes/pvc-58a28c40-7726-4830-ba70-32d18188a8b4 can be exposed by the NGINX running in the pod using a regular service.