How do I remove /etc/nologin I was perusing man pages for fun, as I often do when bored, and happened to be playing around with login today. The login man page mentioned that creating a /etc/nologin file would prevent a user from logging in. I decided to try it. 

The good new is it works as advertised. The bad news is I can no longer use the Terminal. I can't remove the file with rm for obvious reasons, and I can't even delete it from Finder because I can't see hidden files.

How do I regain control of my system?
Power down the system (using the standard Shut Down in the Apple menu) and then start it up again. Shutdown should remove the nologin file for you.