how to access portal admin page without logging in.

I plan to start modifying the login page. In case something goes wrong with the portal login page I modify, I need to have a way to access the portal administration console without having to log in. What is the URL for the portal admin page (where I can deploy par files etc) that does not require me to log in? Or at least requires me to log in without showing the standard login screen (that is specified in the authschemes.xml).