I tried to show my friend how a null modem cable can allow logging into a computer without a monitor, and it didn't work. I wasted 45 minutes trying to do this simple thing connecting a laptop to a server box, but no matter what, I could not get any data to transmit. When my friend was gone, I tried between 2 other boxes, and the serial ports worked then.

I was so sure that this laptop must simply have had a broken serial port. I mean, how could it be 2012 and Ubuntu not have this working? This is the run-of-the-mill 3F8 COM1 port. It works in a proprietary hardware test, it works in the memtest86+ (serial console output) and it works with an older version of Ubuntu (9.04).

What is the deal? I assume that this affects most newer versions of Ubuntu, not just 12.04. Doesn't make sense, because my Fedora 18 and openSUSE 12.2 systems both support the serial port, so the newer Linux kernel must still support it.

Any ideas?