Here’s a simple fix to a common problem.
You’re trying to launch X the same way you always have, but today of all days, you’re getting the following error: X: user not authorized to run the X server, aborting.
The first thing to check is your /etc/X11/Xwrapper.config.
sudo nano /etc/X11/Xwrapper.config
Make sure the line allowed_users is set to allowed_users=console. This means that anybody who is actively logged in to the terminal can start an X session. Don’t set it to anybody unless you have a good reason to– you’d be allowing anybody to start X with root privileges, and for security’s sake we don’t want to do that (at least without a good reason).
The second thing to check is to make sure you are not currently in an attached screen session!
You may or may not see active screens in the list, but none of them should say “attached!” If it does, you’re currently in a screen session, and cannot start an X session from it. Either detach your current session (screen -d) or exit out of it completely (Ctrl+A, D).
The second one is what trips me up every now and then, hence this article…