diff --git a/readme.md b/readme.md
index 7e23fd7..e811b83 100644
--- a/readme.md
+++ b/readme.md
@@ -42,5 +42,7 @@ services:
 
 ## Prerequisites
 
+In order to use the container, you need two images called `boot.img` and `sys.img` from Synology containing the Virtual DSM OS.
+
 * a
 * b