update docs

docs/40_Usage/10_Backup.md

-## Typical Usage
+## Description
 
 This is the main script to start a backup. The script *backup.sh* is the one to add as a cronjob. It will start
 

docs/40_Usage/20_Database.md

-## Make database dumps
+## Description
 
 To create backup database dumps without transfer of local directory to a backup target use `sudo ./localdump.sh`.
 Backup dumps will be stored as gzip files into `/var/iml-backup/[service]`.

docs/40_Usage/30_Filetransfer.md

-## Transfer files ##
+## Description
 
 To transfer local directories to a backup repository use `sudo ./transfer.sh`.
 

docs/40_Usage/40_Cronjob.md

@@ -47,7 +47,9 @@ $ cat /etc/cron.d/client-backup
 
 ## Desktop notification
 
-If you don't run the backup on a server but on a client you can activate the desktop notification for a user that is logged in.
+If you don't run the backup on a server but on a client you can activate the desktop notification for a user that is logged in. It uses *notify-send* to show notification messages.
+
+In a cronjob that start the backup script as root must know the user that should get the notifications.
 Set a variable `SUPER_USER=<USERNAME>` in your cron file.
 
 Example:
@@ -57,5 +59,5 @@ $ cat /etc/cron.d/client-backup
 
 SUPER_USER=axel
 
-*/17 * * * root /usr/local/bin/cronwrapper.sh 1440 /opt/imlbackup/client/backup.sh 'iml-backup'
+17 * * * * root /usr/local/bin/cronwrapper.sh 1440 /opt/imlbackup/client/backup.sh 'iml-backup'
 ```