origin: Mounting file from ConfigMap using volume subPath causes file permission denied error

I’m trying to mount a single file from a ConfigMap into a container directory that already contains other files. Followed https://stackoverflow.com/a/43404857 it seems like it should be possible to do this using volume subPath, however, a permission denied error is shown when I try to open the file. Maybe I’m doing it wrong?

Version

oc v3.6.0+c4dd4cf kubernetes v1.6.1+5115d708d7 features: Basic-Auth

Server XXX openshift v3.6.0+c4dd4cf kubernetes v1.6.1+5115d708d7

Steps To Reproduce

1. Create a configMap:

apiVersion: v1
data:
  hello.txt: This is a test file
kind: ConfigMap
metadata:
  name: myconfig

1. Deploy a test pod, e.g. redis, and edit the deploymentConfig yaml to have:

volumes:
  - configMap:
      name: myconfig
    name: myconfig
....
containers:
  - volumeMounts:
    - mountPath: /var/lib/hello.txt
      name: myconfig
      subPath: hello.txt

1. oc rsh into the pod and cd /var/lib/ and notice how hello.txt can’t be read:

ls -lah                                                                                                                                                           
ls: cannot access hello.txt: Permission denied       

Current Result

ls: cannot access hello.txt: Permission denied

Expected Result

file contents should be available from inside the container.