Quadro K4000 second monitor problem on Xubuntu 18.04

System:
Machine: Intel Dual Xeon E5-2630
OS: Xubuntu 18.10
GPU: Nvidia K4000 GPU
Monitors: Dual Planar PX212M 1600x1200 Monitors

Problem:

This system has been running fine for years under all past versions of
Xubuntu up through 18.04.  The dual monitors are configures without
Xinerama so that separate desktop sessions with separate panels launch
on each screen.

After the recent upgrade to Xubuntu 18.10, the second monitor is not
being recognized.  There is a display [b]:0.0[/b], but no active display [b]:0.1[/b].

However, the second monitor is actually active:

  * Upon boot it goes from black to a uniform grey

  * The mouse can travel onto the second screen (pointer visible)
    and keyboard input (e.g., volume keys) are active

  * Xscreensaver displays on both monitors when it goes active


I have tried to manually start an xfwm4 window manager on the second
screen, but this is not possible without a defined [b]:0.1[/b] display.

At the following link I have provided a number of screen shots, config
file listings, output from relevant commands and log files to explain
in detail what is (or isn't!) happening.  In particular, see notes
under the [b]Log Information[/b] section.

    [url]http://smallthoughts.com/xfce/xfce.html[/url]

The above link also contains a link to the nvidia-bug-report.sh log output.

Questions:

What changed between Xubuntu 18.04 and 18.10 that is keeping the OS
from detecting the second screen and configuring it properly and what
can I do to rectify the problem?  I will provide additional information
as needed.

Supporting dual monitors with separate window managers seems like a
common set-up, yet I can't find straightforward documentation on
enabling this. Am I missing something?

Suggestions are truly appreciated.  Thanks for any help you can offer.

Another user reported some time ago that after upgrade, it wasn’t possible anymore for him to start a second xfce session when using the nvidia drivers, something changed in xfce. Did you try to start an openbox session on the second screen?

I do not have openbox installed on this system. xfwm4 is default window manager for Xfce/Xubuntu and I have tried to manually start it. However, it requires a --display=:0.1 option and there is no defined :0.1 display, although this worked fine for all other Xubuntu releases. I would suspect that that would be the same problem for any other window manager. And would openbox be compatible with this environment (xfce4-session)?

I’m not familiar enough with the guts of X11 to know what the sequence is for identifying the attached monitors and manipulating them manually, but I’m willing to look anywhere and try some experiments if you can give me some pointers.

First monitor:
xrandr -display :0.0
Second monitor:
xrandr -display :0.1
Start xterm on secondary:
DISPLAY=:0.1 xterm
Install and run openbox on secondary:
sudo apt install openbox
DISPLAY=:0.1 openbox

Just try and post output.

35-> xrandr -display :0.0
Screen 0: minimum 8 x 8, current 1600 x 1200, maximum 16384 x 16384
DVI-I-0 connected 1600x1200+0+0 (normal left inverted right x axis y axis) 432mm x 324mm
1600x1200 60.00*+
1280x1024 85.02 75.02 60.02
1024x768 85.00 75.03 70.07 60.00
800x600 85.06 75.00 72.19 60.32 56.25
640x480 85.01 75.00 72.81 59.94
DVI-I-1 disconnected (normal left inverted right x axis y axis)
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)

36-> xrandr -display :0.1
Screen 1: minimum 8 x 8, current 1600 x 1200, maximum 16384 x 16384
DP-3 connected primary 1600x1200+0+0 (normal left inverted right x axis y axis) 432mm x 324mm
1600x1200 60.00*+
1280x1024 85.02 75.02 60.02
1024x768 85.00 75.03 70.07 60.00
800x600 85.06 75.00 72.19 60.32 56.25
640x480 85.01 75.00 72.81 59.94

37-> xrandr
Screen 0: minimum 8 x 8, current 1600 x 1200, maximum 16384 x 16384
DVI-I-0 connected 1600x1200+0+0 (normal left inverted right x axis y axis) 432mm x 324mm
1600x1200 60.00*+
1280x1024 85.02 75.02 60.02
1024x768 85.00 75.03 70.07 60.00
800x600 85.06 75.00 72.19 60.32 56.25
640x480 85.01 75.00 72.81 59.94
DVI-I-1 disconnected (normal left inverted right x axis y axis)
DP-0 disconnected (normal left inverted right x axis y axis)
DP-1 disconnected (normal left inverted right x axis y axis)
DP-2 disconnected (normal left inverted right x axis y axis)

[i]arandr[/b] show it? However it does display it if invoked as: arandr --randr-display=:0.1. I find this non-intuitive and confusing!]

38-> DISPLAY=:0.1 xterm

Yes, the xterm does display on the second screen!

39-> DISPLAY=:0.1 openbox
Obt-Message: Xinerama extension is not present on the server
Openbox-Message: A window manager is already running on screen 1

[Processes running include xfce4-session, xfwm4, xfce4-panel and xfdesktop]

40-> xfwm4 --display=:0.1
Gtk-Message: 11:19:28.442: Failed to load module “atk-bridge”
xfwm4-Message: 11:19:28.489: Another Window Manager (Xfwm4) is already running on screen :0.0
xfwm4-Message: 11:19:28.489: To replace the current window manager, try “–replace”
xfwm4-Message: 11:19:28.490: Another Window Manager (Xfwm4) is already running on screen :0.1
xfwm4-Message: 11:19:28.490: To replace the current window manager, try “–replace”

(xfwm4:22751): xfwm4-WARNING **: 11:19:28.490: Could not find a screen to manage, exiting
44-> DISPLAY=:0.1 openbox-session
Obt-Message: Xinerama extension is not present on the server
Openbox-Message: A window manager is already running on screen 1

[So it does appears that xfwm4 is already managing :0.1 as there is only one xfwm4 process. Lets try starting a second desktop …]

41-> xfdesktop --display=:0.1

[It silently returns, but no desktop appears on screen :0.1 and there is still only one xfdesktop process running. Next, lets try running a panel]

42-> xfce4-panel --display=:0.1

(xfce4-panel:24110): xfce4-panel-CRITICAL **: 11:39:04.805: Name org.xfce.Panel lost on the message dbus, exiting.

[There is apparently no desktop displayed so there isn’t really any place to put the panel!]

All of this is very encouraging. The missing piece is figuring out what steps are required to get that second desktop and panel on the second display. I’ll continue to play around with this, but please offer any other suggestions you may have. Thanks for all the great pointers, but I’m still confused why arandr and xfce4-display-settings do not show the second screen. There still seems to be a lower-level X11 display identification problem here.

Maybe you can find some help in here:
https://forums.gentoo.org/viewtopic-t-152750-start-0.html
Just ignore the Gentoo specific stuff and modify the mentioned xfce session setup script.

Thanks for the link. This discussion was from 2004 so things have changes since then. I’m experimenting with different ways of starting things up but no success so far. There may have been changes to the way the xfce4 session manager operates, so I’m looking into that now. I’ll report back with what I find.

I had the exact same issue, reported here:

https://devtalk.nvidia.com/default/topic/1050250/linux/rtx-2060-xubuntu-2-separate-screens/post/5330751/#5330751

Did not work on xubuntu 18.10, or, 19.04. Works fine on 18.04. Something did change. I was forced to go back to 18.04 as a result, I could not use the system as it did not meet my needs.

Note, I used the exact same configuration (xorg.conf) on 18.04 as 18.10 and 19.04.

I would add one piece of info to this: On 18.04, which does display the desktop on both monitors, the second display is nevertheless hidden from xrandr. I was surprised and had never noticed this before.