diff --git a/README.md b/README.md
index b527052cdfcf48615a06bc563d28f1d03900aac9..d074c4dcfdf3ded1636c2e33a3e0499327d9ac67 100644
--- a/README.md
+++ b/README.md
@@ -50,6 +50,11 @@ and in README files for individual Ansible roles:
 * [Log management and analysis](roles/log-collector/README.md)
 * [Authoritative public DNS](roles/dns/README.md)
 
+Built-in services are currently implemented with Ansible roles, and do
+not run in containers. But this is just an implementation detail, and
+in the future they could be moved to containers without requiring any
+changes in the clients.
+
 # Requirements
 
 On the local machine (the one that will run Ansible), you're going to