If you are a TeamCity system administrator and lost or forgot your local admin password to the server, there are still ways to access it. If your user account has an email address assigned to it, you can reset your password via email – the reset link is located below the login form.
If you don’t have an email address tied to your account, or cannot remember it, but do have access to the OS where TeamCity is installed, you can sign in to TeamCity as Super User by providing a special authentication token. TeamCity sends such tokens to the server log file located in <TeamCity installation directory>\logs\teamcity-server.log. Search for the Super user authentication token phrase and make sure to find the most recent token value. Copy the token and return to the TeamCity login form. Leave the username empty and paste the Super User token as the password.
As a Super User, you can change any setting on the server – when signed in, remember to go to your own user account settings and set a new password.