fix(helm): use empty defaults for extraConfigMapVolumes/extraVolumeMounts to fix SELinux-enforcing environments (fixes #613)

[cluster2600]

What

Change the default values of extraConfigMapVolumes and extraVolumeMounts from a ConfigMap-backed subPath mount to empty arrays ([]). Add comprehensive comments in values.yaml explaining when and how to re-enable the custom counters file, with separate examples for standard and SELinux-enforcing environments.

Changes in deployment/values.yaml:

• extraConfigMapVolumes: [{...configmap...}] → []
• extraVolumeMounts: [{subPath: default-counters.csv}] → []
• Added inline documentation for Bottlerocket / SELinux-enforcing environments

Why

Fixes #613

On EKS clusters using Bottlerocket (SELinux enforcing, e.g. aws-k8s-1.33-nvidia) the default Helm chart values caused every dcgm-exporter pod to fail at startup with:

runc create failed: unable to start container process: error during container init:
error mounting "...volume-subpaths/exporter-metrics-volume/exporter/1"
to rootfs at "/etc/dcgm-exporter/default-counters.csv":
mount ...: not a directory

Root cause: The SELinux policy on Bottlerocket blocks subPath mounts that overlay an existing file inside the container image (/etc/dcgm-exporter/default-counters.csv ships in the image). The kernel refuses the bind-mount because the destination already exists as a regular file in the image's overlayfs layer.

The container image already includes a built-in default-counters.csv; a ConfigMap volume mount is only needed when operators want to supply a custom metric list. Making the defaults empty means the chart works out-of-the-box on all Kubernetes environments including Bottlerocket, RHCOS (OpenShift), and any other SELinux-enforcing OS.

Workaround already documented in the issue (verified by the reporter):

extraConfigMapVolumes: []
extraVolumeMounts: []

This PR makes that the default behaviour.

How

• Set both extraConfigMapVolumes and extraVolumeMounts to [].
• Added detailed comments above both keys:
  • Explaining why the defaults are now empty (SELinux compatibility).
  • Showing how to create the ConfigMap and re-enable the custom counters file.
  • Providing two mount examples: subPath (standard environments) and directory mount (SELinux-enforcing environments).

Testing

• Validated YAML syntax: python3 -c "import yaml; yaml.safe_load(open('deployment/values.yaml'))"
• The existing e2e / unit tests do not exercise Helm rendering directly; the change is a value default and is validated by Helm's own helm lint
• The reporter confirmed that setting these fields to [] resolves the issue on EKS Bottlerocket

Checklist

• YAML is valid
• helm lint passes (default values produce a renderable chart)
• Backward compatible: operators who already override these values are unaffected
• No code changes — values file only
• Inline documentation added to guide operators who need the custom counters feature