Ubuntu 20.04.3 desktop (Cinnamon) - SSH disconnects when user logs off the desktop!

[Colin Law]

On Mon, 24 Jan 2022 at 11:17, Bo Berglund <bo.berglund at gmail.com> wrote:
>
> Another snag here!
> If I disconnect the physical monitor after I have installed and successfully
> tested TigerVNC on display :1, then it will *not* boot and since I have no
> display attached I cannot say how far it gets. In any case it never comes
> on-line on the LAN.

You can look in syslog after the successful reboot to see what was happening.
Did it also not respond to ssh?

>
> Strangely if I leave the monitor cable in place but power down the monitor in
> the other end of the cable, then it boots and I can use VNC! What is the
> difference? Monitor disconnected or a powered down monitor in the other end of
> the cable?

The PC still sees the monitor even if it is not powered up.  I believe
the logic connected to the port is powered via the cable rather than
from the display.  You can see that if you watch syslog and plug the
cable in.

>
> The monitor connection is by way of DiaplayPort, the HP PC has 2 of these and
> nothing else...
>
> So as it is now I cannot use it after all, since there will be no monitor
> attached in the end location. The plan was to have the PC stored in a cupboard
> somewhere and accessed via SSH and VNC. But of course that does not work if it
> behaves in this way.

As I said, check syslog.

However, I still think you have a hardware problem, though it is very
odd I agree.  Have you tried running memtest from a USB stickovernight
to see if it keeps going?

>
> I have a dozen or so Raspberry Pi units which run a Debian variant of Linux.
> These will not behave like this,

Neither does any machine I have ever heard of behave like this running
Ubuntu.  That is why I think you have a hardware problem.

A thought though, so obvious that you have likely already done it.
Have you checked that you are using the latest version of the
BIOS/UEFI firmware?

Colin