Undo sudo nvram boot-args="-s" without terminal I couldn't boot into single-user mode on my iMac 2007 with Mac OS X 10.5, so I forced it to do so with sudo nvram boot-args="-s". However, now my Mac won't boot and sits there with the spinning icon under the Apple logo.

Obviously, being an older OS there is no Internet recovery or normal recovery partition to boot to.

Icing on the cake is, it's a 2nd hand iMac with no recovery disks.

I have tried resetting PRAM and NVRAM, alas to no avail, does anyone know how to remedy this?
Turns out this was as simple as a stuck key was stopping any boot up commands.

Plugged in a different keyboard and everything was just fine.