Enable udevadm in the container for node_exporter

[TProhofsky]

Node_exporter 1.4.0 now supports reporting udevadm information on devices like serial number and world wide name. When node_exporter is running inside the container it doesn't have the udevadm executable and libraries and any other mappings required for operation. Is there a plan to add what is needed through the pod spec or is the node_exporter Dockerfile going to capture the magic? What is the best way to enable the new metrics available in 1.4.0 with a kube-prometheus deployment?

[TProhofsky]

After looking deeper at the node_exporter code I see it does not call udevadm but uses the /run/udev/data directly. This makes the solution obvious by adding a read only volume mount in the pod spec. This works for me:

# git diff
diff --git a/manifests/nodeExporter-daemonset.yaml b/manifests/nodeExporter-daemonset.yaml
index 1720502f..25d3e61c 100644
--- a/manifests/nodeExporter-daemonset.yaml
+++ b/manifests/nodeExporter-daemonset.yaml
@@ -5,7 +5,7 @@ metadata:
     app.kubernetes.io/component: exporter
     app.kubernetes.io/name: node-exporter
     app.kubernetes.io/part-of: kube-prometheus
-    app.kubernetes.io/version: 1.3.1
+    app.kubernetes.io/version: 1.4.0
   name: node-exporter
   namespace: monitoring
 spec:
@@ -22,7 +22,7 @@ spec:
         app.kubernetes.io/component: exporter
         app.kubernetes.io/name: node-exporter
         app.kubernetes.io/part-of: kube-prometheus
-        app.kubernetes.io/version: 1.3.1
+        app.kubernetes.io/version: 1.4.0
     spec:
       automountServiceAccountToken: true
       containers:
@@ -35,7 +35,7 @@ spec:
         - --collector.filesystem.mount-points-exclude=^/(dev|proc|sys|run/k3s/containerd/.+|var/lib/docker/.+|var/lib/kubelet/pods/.+)($|/)
         - --collector.netclass.ignored-devices=^(veth.*|[a-f0-9]{15})$
         - --collector.netdev.device-exclude=^(veth.*|[a-f0-9]{15})$
-        image: quay.io/prometheus/node-exporter:v1.3.1
+        image: quay.io/prometheus/node-exporter:v1.4.0
         name: node-exporter
         resources:
           limits:
@@ -61,6 +61,10 @@ spec:
           mountPropagation: HostToContainer
           name: root
           readOnly: true
+        - mountPath: /run/udev/data      # Used by node_exporter for drive attributes
+          mountPropagation: HostToContainer
+          name: udev
+          readOnly: true
       - args:
         - --logtostderr
         - --secure-listen-address=[$(IP)]:9100
@@ -111,6 +115,9 @@ spec:
       - hostPath:
           path: /
         name: root
+      - hostPath:
+          path: /run/udev/data
+        name: udev
   updateStrategy:
     rollingUpdate:
       maxUnavailable: 10%