diff --git a/Update-recommendations-and-troubleshooting.md b/Update-recommendations-and-troubleshooting.md
index d024eda..b1e2ecd 100644
--- a/Update-recommendations-and-troubleshooting.md
+++ b/Update-recommendations-and-troubleshooting.md
@@ -4,6 +4,14 @@
 
 If you are not familiar with your Apache/Nginx configuration (including https), or need to ensure only a minimal downtime, the recommendation will be always to do the **painless new installation** on a new host and then an **migration of your database and files** to the new host! Same is true if your old hosts version is no longer supported by from it distribution.
 
+# Requirements for the update to succeed
+The update operates under the assumption you have NOT changed any of the following:
+* files or backup directory (/var/lib/egroupware/default/files or /var/lib/egrouware/default/backup)
+* your database runs on the host AND you use "localhost" as "db_host in header.inc.php
+* your EGroupware runs under http(s)://your.domain/egroupware (Setup >> Konfiguration >> Webserver URL: /egroupware).
+> If you changed anything of the above, you either need to change it back to the default locations, or you need to fix your installation after the update. 
+> ***EGroupware will fail after the update without any further changes!***
+
 # How to migrate your data from an existing 17.1 or older installation
 1. do a new installation as described for the distribution of the new host
 2. enable https using Let's Encrypt following the exzellent instructs from eg. [Digital Ocean](https://www.digitalocean.com/community/tutorials/how-to-secure-apache-with-let-s-encrypt-on-ubuntu-18-04)