On 12.04 LTS, I typed "apt-get install xdm" - then a window asked if I wanted
lightdm or xdm, and I selected xdm. Then I rebooted but the display only showed,
for a very long time, the word "ubuntu" and orange dots moving over a purple
background. There was no login prompt. I was not able to use key sequences such
as Ctrl-Alt-F1 to Ctrl-Alt-F7 (or Alt-F1 to Alt-F7) to obtain a text terminal.
All of these key sequences were ignored. I rebooted multiple times and this behavior
always occurs. What is the easiest way to obtain login access to the system?