How can I investigate the cause of total hang? Is there some information that I should pay attention to in order to get some hint?

[Karl Auer]

On Sat, 2020-07-04 at 08:43 -0600, Drew Einhorn wrote:
> I don't know to tell whether it is sleeping, hibernating, or
> blanking.

Well, finding out would be a good first move.

Next time the screen is blank when you return, try the following things
carefully and slowly, giving the system a good ten or twenty seconds to
react before trying the next:

- move the mouse slightly
- tap LEFT SHIFT
- tap RIGHT SHIFT
- tap SPACE
- tap ENTER
- press (and immediately release) the power button

Whichever of these causes a change to the system is probably your
system's "come back from sleep" trigger. Remember it and use that next
time.

If your system has a clear indicator that it is asleep, is that
indicator showing when you return to the system (before you touch it an
any way)? I'm guessing that you don't have such an indicator, or that
it is not working. Most systems will show a slowly blinking light of
some sort, or change the colour of the power light, but it may be
something else on your system.

Try manually triggering sleep/blank. Generally you can elect to sleep
the system using the widget at top right of the screen. Check the
system carefully for any light or other unambiguous indicator that
starts showing when you manually sleep the system. If you have a manual
of any sort for your system you could consult that for information
about what sleep looks like.

If the system appears to have slept, does it recover? If not, you have
IMHO proven that your system has a problem recovering from sleep. If it
DOES recover, then it could be the BIOS causing the problem (see
below).

As a workaround, you could turn off all sleeping and blanking options,
so that the system should not ever sleep or blank. Wait a respectable
amount of time (like overnight) to make sure it has not slept/blanked. 

If the system sleeps/blanks even though you told it not to, you could
check the BIOS settings just in case the motherboard is doing it. If it
is, disable it there too.

If there is nothing of value to you on the system (or you have it
backed up) then a re-install can't hurt. However, if your system is one
that doesn't know how to sleep properly (or rather, doesn't know how to
come back) I fear a re-install is unlikely to help.

> I see that lightdm proccesses are runnning.
> "systemctl restart lightdm" gets graphics restored.
> 
> That's a big step forward.

Good - one step at a time :-)

Regards, K.

PS: Is this a brand-name system? If so, what make and model? Again, I
apologise if this has already been asked and answered.

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Karl Auer (kauer at biplane.com.au)
http://www.biplane.com.au/kauer
http://twitter.com/kauer389

GPG fingerprint: 2561 E9EC D868 E73C 8AF1 49CF EE50 4B1D CCA1 5170
Old fingerprint: 8D08 9CAA 649A AFEF E862 062A 2E97 42D4 A2A0 616D