Does not login or shutdown when external display is connected

Asked by Juha Simola

After a recent update, about on 28th Jan, 2019, there's a problem that desktop is not showing up after login if the external display is connected.
The computer does not shut down either when the external display is connected. Only default dark brown ubuntu color is shown on the laptop display and the computer stays on forever.

When I disconnect the display from dock, login and shutdown work normally.
If I connect the display after login, the desktop is moved there normally and the built-in display is switched off.
If I disconnect the display before the shutdown, the computer shuts down normally.

Ubuntu 18.04 LTS
ThinkPad T480s
ThinkPad USB-C dock
Dell 27" 4k display
Display-cable

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Juha Simola
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mtd (miehael) said :
#2

The problem description matches my recent (today) experience. Usually, I leave laptop docked, case closed and just use the external display. Today, there was a crash involving the display corruption after unlocking the screen lock, so I rebooted. Since then, there are problems involving the external display:
(1) after login (docked mode, external display only), the display does not show. ssh into host still works.
(2) it works ok to start with internal display on, then connect external display (dual displays).
(3) but in this dual mode, if I use the keyboard combination to disable the internal monitor, I get a lockup similar to (1), with the internal display frozen. ssh works.

I have similar hardware to the original report: Lenovo T480; Thinkpad USB-C dock; Dell 4K display, HDMI->DisplayPort cable.

I currently have the Nouveau display driver enabled, but I have tried both nvideo-driver-410 and -415 to no success.

Revision history for this message
Juha Simola (jm-simola) said :
#3

Downgrading to previous Kernel 4.15.0-43-generic fixed the problem.
The problem is with 4.15.0-44-generic

This bug report seems to be from this issue:
https://bugs.launchpad.net/ubuntu/+source/gnome-shell/+bug/1813738