Example: Monitoring external server with Prometheus Operator

prometheus-operator-kubernetes.yaml

# First install prometheus-operator: 
# 
# helm install coreos/prometheus-operator --name prometheus-operator
#

apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  name: node-exporter
  # Namespace of prometheus operator
  namespace: monitoring
  labels:
    prometheus: mon
spec:
  namespaceSelector:
    matchNames:
    - server-monitoring
  selector:
    matchLabels:
      k8s-app: node-exporter
  endpoints:
  - port: metrics
    interval: 10s

---

apiVersion: v1
kind: Service
metadata:
  name: name-your-server-com
  namespace: server
  labels:
    k8s-app: node-exporter
spec:
  type: ExternalName
  externalName: name.your-server.com
  clusterIP: ""
  # Maybe not relevant
  ports:
  - name: metrics
    port: 9100
    protocol: TCP
    targetPort: 9100

---

apiVersion: v1
kind: Endpoints
metadata:
  # Name must match service name
  name: name-your-server-com
  namespace: server
  labels:
    k8s-app: node-exporter
subsets:
  - addresses:
    - ip: 192.168.99.12
    ports:
      - name: metrics
        port: 9100
        protocol: TCP

Hi,
Do we still need a service monitoring to monitor external service after adding this additional scraperConfigs?

No, you can either use the serviceMonitor with the Service and the Endpoint or add the configuration in the additionalScrapeConfigs