Support to securityContext.fsGroup to override the owner of mounted volumes

[Heitor Ricardino Barros]

Hi there!

I recently attached SSDs for caching purposes and enabled them by mounting the volume at /data/trino/cache. However, upon doing so, I encountered the following exception from Alluxio:

IllegalArgumentException: Cannot write to cache directory /data/trino/cache.

After some investigation, I suspect that I need to specify the fsGroup to 1000 in pod.spec.securityContext. Currently, the chart supports runAsGroup and runAsUser in securityContext:

...
     {{- with .Values.securityContext }}
     securityContext:
        runAsUser: {{ .runAsUser }}
        runAsGroup: {{ .runAsGroup }}
     {{- end }}
...

The volume declared into pod spec:

...
    - name: ebs-cache-volume
      ephemeral:
        volumeClaimTemplate:
          spec:
            accessModes:
              - ReadWriteOnce
            resources:
              requests:
                storage: 100Gi
            volumeMode: Filesystem
...

Could you please confirm if adding fsGroup: 1000 to the pod.spec.securityContext would resolve this issue? If not, any guidance on how to properly configure the security context for SSD caching would be greatly appreciated.

Thanks in advance for your help!

[Heitor Ricardino Barros]

PR adding the fsGroup

[Catherine Thompson]

Would it be worth making the entire podSecurityContext a templated value?