Solved this but going to leave it up in case it's useful to anyone - just used the pod template in the values.yml for the clearml-agent helm chart to mount the hostpath as a volume mount i.e.:
podTemplate:
# -- volumes definition for pods spawned to consume ClearML Task (example in values.yaml comments)
volumes:
- name: x11-host-dir
hostPath:
path: /tmp/.X11-unix
volumeMounts:
- name: x11-host-dir
mountPath: '/tmp/.X11-unix'
Nice! Well found and thanks for posting the solution!
May I ask out of curiosity, why mount X11? Are you planning to use a GUI app on the k8s cluster?