hostPath as volume in kubernetes

Question

I am trying to configure hostPath as the volume in kubernetes. I have logged into VM server, from where I usually use kubernetes commands such as kubectl.

Below is the pod yaml:

apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: helloworldanilhostpath
spec:
  replicas: 1
  template:
    metadata:
      labels:
        run: helloworldanilhostpath
    spec:
      volumes:
        - name: task-pv-storage
          hostPath:
            path: /home/openapianil/samplePV
            type: Directory
      containers:
      - name: helloworldv1
        image: ***/helloworldv1:v1
        ports:
        - containerPort: 9123
        volumeMounts:
         - name: task-pv-storage
           mountPath: /mnt/sample

In VM server, I have created "/home/openapianil/samplePV" folder and I have a file present in it. It has a sample.txt file.

once I try to create this deployment. it does not happen with error -
Warning FailedMount 28s (x7 over 59s) kubelet, aks-nodepool1-39499429-1 MountVolume.SetUp failed for volume "task-pv-storage" : hostPath type check failed: /home/openapianil/samplePV is not a directory.

Can anyone please help me in understanding the problem here.

Answer 1

hostPath type volumes refer to directories on the Node (VM/machine) where your Pod is scheduled for running (aks-nodepool1-39499429-1 in this case). So you'd need to create this directory at least on that Node.

To make sure your Pod is consistently scheduled on that specific Node you need to set spec.nodeSelector in the PodTemplate:

apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: helloworldanilhostpath
spec:
  replicas: 1
  template:
    metadata:
      labels:
        run: helloworldanilhostpath
    spec:
      nodeSelector:
        kubernetes.io/hostname: aks-nodepool1-39499429-1
      volumes:
        - name: task-pv-storage
          hostPath:
            path: /home/openapianil/samplePV
            type: Directory
      containers:
      - name: helloworldv1
        image: ***/helloworldv1:v1
        ports:
        - containerPort: 9123
        volumeMounts:
         - name: task-pv-storage
           mountPath: /mnt/sample

In most cases it's a bad idea to use this type of volume; there are some special use cases, but chance are yours is not one them!

If you need local storage for some reason then a slightly better solution is to use local PersistentVolumes.