Recently, I was working on a new Mac OS X 10.5 Server setup. At one point after I’ve been through hours and hours of work, something terrible happened: After having brought up some client computers into the network, setting up some accounts and groups and preferences for them etc. I started up the server. The system did not accept my administrator password. I tried another admin account – nothing. I tried resetting the password from the OS X Installation DVD – still nothing.
Luckily, I found the problem really quickly. How?
I logged on from another local computer using the Server Admin Tools. I could access the server! What the problem came down to is this (the image does not depict what was the case!):

In the Server Admin Settings, there’s a tab to control service access. Per default it is set to “For all services” and “Allow all users and groups”. But before the reboot, someone (and I am not going to tell who) ticked “allow only users and groups below”, while the field below was left empty. That meant that no user had access to the login window, at least that is what I assume to have been the problem. I changed the parameter back to “Allow all users and groups” and bob’s your uncle again!
Tags: admin, administrator, does not work, fails, locked out, login, OS X, password, problems, Server