diff --git a/engine/admin/prometheus.md b/engine/admin/prometheus.md
index c6ca5b1e9e..6ec3c76c3e 100644
--- a/engine/admin/prometheus.md
+++ b/engine/admin/prometheus.md
@@ -47,7 +47,15 @@ Docker now exposes Prometheus-compatible metrics on port 9323.
 
 ## Configure and run Prometheus
 
-In this example, Prometheus runs as a Docker container on the same host.
+In this example, Prometheus runs as a Docker service on a Docker swarm.
+
+> **Prerequisites**
+>
+> 1.  One or more Docker engines are joined into a Docker swarm, using `docker swarm init`
+>     on one manager and `docker swarm join` on other managers and worker nodes.
+>
+> 2.  You need an internet connection to pull the Prometheus image.
+
 
 Copy one of the following configuration files and save it to
 `/tmp/prometheus.yml` (Linux or Mac) or `C:\tmp\prometheus.yml` (Windows). This