Staring at a crashed Gnome session, CTRL-ALT-BKSPC does nothing. ALT-CTRL-F1 won’t bring you to a terminal where you could cd to /etc/init.d and restart gdm.
There’s two more options that you may not have known about
Here are two ways to first try and kill just the process on your current terminal and if that fails, to bring your machine down in a more graceful manner than a hard shutdown.
First, we’ll try and kill all the process on your current terminal. To do this, hold down the following keys --
ALT + SysReq + k
SysReq key means you need to Look for it on your PrtSc or Print Screen key. The k in this instance stands for Kill.
You’ll now enter a series of keystrokes that will tell your computer to do some housekeeping before shutting down.
ALT + SysReq + r
This stands for Raw keyboard mode.
ALT + SysReq + s
This syncs the disk.
ALT + SysReq + e
This terminates all processes
ALT + SysReq + i
Kill’s all processes that weren’t terminated nicely.
ALT + SysReq + u
Remounts all filesystems as read only.
ALT + SysReq + b