updated readme

README.md

@@ -2,6 +2,8 @@
 
 A Docker Container for [Apache Guacamole](https://guacamole.incubator.apache.org/), a client-less remote desktop gateway. It supports standard protocols like VNC, RDP, and SSH over HTML5.
 
+This container runs the guacamole web client, the guacd server and a postgres database.
+
 ## Usage
 
 ```shell
@@ -17,3 +19,7 @@ The parameters are split into two halves, separated by a colon, the left hand si
 
 * `-p 8080:8080` - Binds the service to port 8080 on the Docker host, **required**
 * `-v /config` - The config and database location, **required**
+
+## Default User
+
+The default username is `guacadmin` with password `guacadmin`.