On Thu, 24 Dec 2015 07:59:26 +0100, R. W. Rodolico <rodo(a)dailydata.net>  
wrote:

> I have looked around for any reference to a serial console in the grub
> configurations (in /etc and in /boot/grub) but see no references to a
> serial console in either of them.

Have you checked "/etc/default/grub"?
There should be something like "console=ttyS0,115200n8" for  
"GRUB_CMDLINE_LINUX" afair.


hth,
Lars