Yesterday, I tried to update to the second public beta of macOS Sierra. For some reason, however, the update process stopped shortly before the completion, and since there was no progress even after many hours, I decided to shut down. Everything works fine as far as the startup is concerned, but I can not login with my regular user account. While the password is recognized as correct, the display turns black when my data are supposed to be loaded, and I am again asked to enter my password. Neither restarts nor safe boots were of help. As this Mac is not my main computer, there is no backup. Still, I would like to know: Is there any way to restore my login? Update Meanwhile, I reinstalled macOS Sierra—probably the first public beta—via the recovery mode completely, but the problem is still there, even in safe mode. Apparently, all of the disk data are still there as well, but I can simply not login due to the black screen. Is there no other approach?