[SOLVED] Host directory indicated as mounted, but empty in the container

Host directory indicated as mounted, but empty in the container - what to check?

My Docker container running in a minikube pod has configured a directory mounted from the host's non-empty /home/my_username/useful/dir. kubectl shows what I expect:

$ kubectl get --namespace=my_namespace pods/my-pod -o json | jq '.spec.volumes[3]'
{
  "hostPath": {
    "path": "/hosthome/my_username/useful/dir",
    "type": "Directory"
  },
  "name": "useful_dir"
}
$ kubectl get --namespace=my_namespace pods/my-pod -o json | jq '.spec.containers[].volumeMounts[3]'
{
  "mountPath": "/dir/in/container",
  "name": "useful_dir",
  "readOnly": true
}

But in the pod, the mountpoint is empty:

$ kubectl exec --stdin --tty --namespace my_namespace my-pod -- ls /dir/in/container
total 0

I looked at the pod's mountpoint with kubectl exec --stdin --tty --namespace my_namespace my-pod -- findmnt /dir/in/container, and see overlay[/hosthome/my_username/useful/dir]. From this, I conclude that Docker has mounted the directory from the host as expected.

I check the mountpoint directly from a pod's container (as root to make sure there is no permission restriction in the way):

$ docker exec -it -u root minikube /bin/bash
root@minikube:/# docker exec -it -u root <container_id> ls /dir/in/container
root@minikube:/#

It does not have any content which is present in the host.

What should I look for to investigate?

Solution

Issue solved in comments, the driver was running dockerd inside a container itself so it didn't have a global filesystem view. Solved via minikube mount.