I am not sure what I did. I just entered the commands listed above, then the unit rebooted and I was unable to access it anymore, via IP and telnet/SSH and also the console did not work. I powered it down by unplugging the power cables, waited some time and booted it up again.
Now it is listed up in the OnCommand System Manager with Version 8.2.5P5 7-Mode and I can access the config interface via OnCommand System Manager again.
But all licences are gone and I can not re-enter them: Invalid license.
But for some reason I was able to join the domain and I can access the share with my domain admin. But the ESXi servers can not.
On the new FAS we have running version 9.3 I had to edit "Export Policies" for the SVMs and add the IP addresses of the servers. But I can not find that option on the old one... Where is that?
So this issue is left with the IP addresses and export policies and the licences... System ID of the FAS2240-2 is 1787986847 - if that helps.