Kubernetes: mounted file is a... directory?

Question

I've created a secret and when I deploy an application intended to read the secret, the application complains that the secret is a directory.

What am I doing wrong? The file is intended to be read as, well, a file.

kc logs <pod>
(error) /var/config/my-file.yaml: is a directory.

The secret is created like this.

kubectl create secret generic my-file.yaml --from-file=my-file.yaml

And here is the deployment.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: a-name
spec:
  replicas: 1
  selector:
    matchLabels:
      name: a-name
  template:
    metadata:
      labels:
        name: a-name
    spec:
      volumes:
        - name: my-secret-volume
          secret:
            secretName: my-file.yaml
      containers:
        - name: a-name
          image: test/image:v1.0.0
          volumeMounts:
            - name: my-secret-volume
              mountPath: /var/config/my-file.yaml
              subPath: my-file.yaml
              readOnly: true
          ports:
            - containerPort: 1234
            - containerPort: 5678
          imagePullPolicy: Always
          args:
            - run
            - --config
            - /var/config/my-file.yaml 
  revisionHistoryLimit: 1

Answer 1

You are using subPath in the volume mount section. According to Kubernetes volume doc, when you need same volume for different purpose in the same pod then you should use subPath.

But here you are using the volume for only single use. But I'll give you both yaml file with subPath and without subPath.

With SubPath

          volumeMounts:
            - name: my-secret-volume
              mountPath: /var/config
              subPath: config
              readOnly: true

WithOut SubPath

          volumeMounts:
            - name: my-secret-volume
              mountPath: /var/config
              readOnly: true

Rest of the manifest file will be same in both cases.