diff --git a/doc/running-on-ubuntu.md b/doc/running-on-ubuntu.md
index 41b34e0e970480d5cc0692fb538c089efad2b330..ba2d1dd1b283bbc1bcf7a75205a09c5cc3d31139 100644
--- a/doc/running-on-ubuntu.md
+++ b/doc/running-on-ubuntu.md
@@ -29,5 +29,6 @@ etcdctl ls
 etcdctl help
 ````
 
+Be aware that this will expose etcd on port 4001, also on the public IP address, so if you are using this in production the it is very important to block this port on the firewall.
 Now follow the [CoreOS-based instructions](deploying-a-server.md)