problematic poweroff on shutdown
Periodically, for no reason I can fathom, or trace to a specific cause,
when I shutdown my machine, it fails to power off. The shutdown
procedure unrolls, or unfurls, as expected, but at the point where it
says at the console "Will now halt," instead of a power off taking
place, the console displays an additional message: "Power off". At that
point, my only alternative is to press the power buttom at the front of
the machine for five seconds, which turns the machine off (this seems
a gentler alternative to yanking out the power cord from the socket, as the
psu on this 'puter has no power switch).
How would I go about trouble-shooting this erratic behavior?
I hijacked another thread in which I posited that the problem was
related to plugging in an external usb hard drive. This supposition has
turned out to be false (post hoc ergo propter hoc), as so many of my
suppositions do these days.
There's nothing in the logs to distinguish the no poweroff shutdowns
from the poweroff ones (I don't think; I have looked).