Add rule for reboot-required (#262)

_data/rules.yml

@@ -280,6 +280,11 @@ groups:
                 query: 'min_over_time(node_timex_sync_status[1m]) == 0 and node_timex_maxerror_seconds >= 16'
                 severity: warning
                 for: 2m
+              - name: Host requires reboot
+                description: '{{ $labels.instance }} requires a reboot.'
+                query: 'node_reboot_required > 0'
+                severity: info
+                for: 4h
 
 
       - name: Docker containers