Bug#783881: Debugging information
I think I may have gathered a useful clue, though of the kind I was
expecting...
In order to gather the boot messages immediately before shutdown, that I
don't normally get to see due to the graphics card output turning off
early, I attached to the Linux console via serial, by adding this on the
linux kernel command line:
console=ttyS0,38400
After doing that, for about seven boots, I couldn't reproduce the
original problem.
I removed that option again for a couple of boot-shutdown cycles, and on
the second one on shutdown it failed to power the machine off again.
I also tried reinstating the 'quiet' option to the kernel which is there
by default after installing Debian, and shutdown still failed the next time.
Put the console=ttyS0,38400 back, and the problem *seems* to go away.
However the failed poweroff is intermittent, so the use of
console=ttyS0,38400 and it consistently powering off OK could just be
happy coincidence.
I intend to keep the linux console as serial for a few days, and see if
I or the machine's other user experiences this poweroff problem again
under normal operation rather than my forced idea of normal operation.
If it's consistently OK for that time, I think it would be safe to say
that this bug only appears for me if the console is the graphics card.
It also appears that the display stayed on with a blinking cursor in the
top left right until poweroff, whereas without that option it turned off
earlier.
For the record at this point, I think it's worth mentioning that my
graphics adapter is:
01:00.0 VGA compatible controller [0300]: NVIDIA Corporation G98
[GeForce 8400 GS Rev. 2] [10de:06e4] (rev a1)
and it's being driven with the nouveau graphics driver.
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