What is the best way to move a Linux GMS to a new hardware?

What I've done til now:
Make a image of the old server and restore it to the new hardware.
After I changed some hardware related Linux settings the server and the GMS started again.
But now no user cannot login into the GMS - neither with the mobile device nor via webpim. The GMS admin can login into the admin interface. Also I cannot add new user to the GMS (Authentication failed)
I have removed the groupwise related settings in GMS and inserted again but without any success. I can see the SOAP login from the GMS to my POA.
Maybe that there are some hardware specific rules/keys how to creates/saves the GMS the passwords, but I cannot find anything about this - and I cannot set the password inside of the admin interface (the password fields are grayed out)