Values for the grafana helm chart to talk to an existing prometheus datasource

grafana-prometheus-values.yaml

persistence:
  enabled: true
  accessModes:
    - ReadWriteOnce
  size: 5Gi

datasources: 
 datasources.yaml:
   apiVersion: 1
   datasources:
   - name: Prometheus
     type: prometheus
     url: http://my-prometheus-server
     access: proxy
     isDefault: true

dashboards:
    kube-dash:
      gnetId: 6663
      revision: 1
      datasource: Prometheus
    kube-official-dash:
      gnetId: 2
      revision: 1
      datasource: Prometheus

dashboardProviders:
  dashboardproviders.yaml:
    apiVersion: 1
    providers:
    - name: 'default'
      orgId: 1
      folder: ''
      type: file
      disableDeletion: false
      editable: true
      options:
        path: /var/lib/grafana/dashboards