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Inline ephemeral support

The CSI Hostpath driver (starting with version 1.2.0) now includes support for inline ephemeral volumes. This means that a volume can be specified directly inside a pod spec without the need to use a persistent volume object. Inline ephemeral support was introduced as an alpha feature in Kubernetes 1.15 and was promoted to beta in 1.16. Find out how to enable or create a CSI driver with support for such volumes here

To test this feature on Kubernetes 1.15 (and only with that release), redeploy the CSI Hostpath plugin YAML by updating the hostpath container to use the inline ephemeral mode by setting the ephemeral flag, of the driver binary, to true as shown in the following setup:

kind: StatefulSet
apiVersion: apps/v1
metadata:
  name: csi-hostpathplugin
spec:
...
  template:
    spec:
      containers:
        - name: hostpath
          image: image: quay.io/k8scsi/hostpathplugin:v1.2.0
          args:
            - "--v=5"
            - "--endpoint=$(CSI_ENDPOINT)"
            - "--nodeid=$(KUBE_NODE_NAME)"
            - "--ephemeral=true"      
...

Notice the addition of the ephemeral=true flag used in the args: block in the previous snippet. This is an intermediate solution for Kubernetes 1.15. With Kubernetes 1.16 and later, the normal deployment supports both inline ephemeral volumes and persistent volumes.

Once the driver plugin has been deployed, it can be tested by deploying a simple pod which has an inline volume specified in the spec:

kind: Pod
apiVersion: v1
metadata:
  name: my-csi-app
spec:
  containers:
    - name: my-frontend
      image: busybox
      volumeMounts:
      - mountPath: "/data"
        name: my-csi-volume
      command: [ "sleep", "1000000" ]
  volumes:
    - name: my-csi-volume
      csi:
        driver: hostpath.csi.k8s.io

See sample YAML file here.

Notice the CSI driver is now specified directly in the container spec inside the volumes: block. You can use the [same steps as above][Confirm Hostpath driver works] to verify that the volume has been created and deleted (when the pod is removed).