For backup mode, the user creation screen is just a placeholder since you already have your users setup.
Right but when I get to the point where a user creation screen normally comes up what I get rather than the screen is an Invalid username message. I do nothing to prompt that message. It simply appears a bit after I select my keyboard layout. If I attempt to close that message box it just reappears. After a while a second box appears behind the Invalid user message. That is a notification that Ubi-partman crashed. The install is dead from that point.
If I reset my box, on a reboot I am then able to install my backup okay. In this instance there is no Invalid user message. The user creation screen comes up and requires me to give it user info.
I've done 3 different backups and in all 3 cases I was faced with the same scenario as I've stated above. I can say that in the end I did end up with a complete, operable system that duplicated the original.
Maybe I am doing something wrong when I create the backup but I don't know what it is. I haven't used remastersys since Ubuntu 9.04 was on the scene and then I was working with distribution disks rather than backups. I didn't have this situation with that.