Only account is a locked "Guest" after upgrading to OS Lion

My friend updated his 13" MacBook Pro to OS X Lion today. After upgrading he has been met with a login screen showing a single account, "Guest". This "Guest" account is password-protected and none of the existing passwords he used on the computer seem to work.

My friend had previously installed rEFIt on his computer, which apparently hasn't been updated for Lion yet.

I found this thread on MacRumors where a few other people are reporting the same problem.

Does anyone know of a solution?

An easier way is to:

1. Get a terminal/console somehow (e.g. start up in recovery mode by holding down option).
2. Delete the file /Volumes/<your root volume>/Library/Preferences/com.apple.loginwindow.plist.
3. Reboot.

That's it.

He found a solution on the Apple discussion boards (slightly edited):

I solved this exact problem by doing the following:

• Restart in recovery mode by holding the option key while booting.
• Open the Terminal, then run resetpassword to set root password.
• Log out, then log in to the now-available root account.

• Go to "Users & Groups" in System Preferences, and create a new user with the exact same username as your old account. When it asks, confirm that you do want to use the existing directory.

  • You can find out the username by looking for the folder in /Users.

• Log out, and your account is back!

This worked for me. I think I lost some of my Desktop's files but they were not too important to me...

My friend reports that the files on his Desktop were intact, but use at your own risk.