Cannot force correct resolution of monitor connected through KVM switch.

[rcdawson]

I need help in setting up my KVM switch. At this point I am not able to boot the system and have the monitor operate at its preferred resolution. I have attempted to create an xorg.conf file to achieve this, but have so far not succeeded. I thought I had done that, but it seems to have no effect, so I have either not created a valid file, or this isn't even the right approach. I would appreciate any help available.

The SAGA:

The monitor is a Dell U2410 with native resolution of 1920x1200.

The computer is running Kubuntu 19.04 with Nvidia proprietary driver.

The computer is connected to the monitor through a KVM switch. In the past, with previous versions of Linux, Linux Mint KDE up to 17.3, System Settings > Displays also offered a maximum resolution less than 1920x1200 with the monitor connected through the KVM switch. I learned to live with it, but when I attempted to install Kubuntu 19.04 the computer would not connect to the monitor at all, and I got an error message saying that I needed to have a device with 1920X1200 resolution. I couldn't proceed with the installation. I tried rebooting the CD to no avail. I saw no way around the problem, so I connected the monitor directly to the computer. Booted into a 1920x1200 screen with no problem, and all worked well.

I still wanted to use the KVM switch. so I attempted to use Nvidia's application to generate an xorg.conf. There must have been some sort of permissions problem, because it couldn't write the file. Tried running "sudo nvidia-settings." Same result. It would not write to /etc/X11 or to my home directory. I used xvidtune to generate mode lines for my monitor for the resultions that I wanted.

I found a file named "xorg.conf.nvidia-xconfig" in the /etc/X11 directory. It included a Monitor section as follows:
Section "Monitor"
Identifier "Monitor0"
VendorName "Dell"
ModelName "U2410"
HorizSync 28.0 - 33.0
VertRefresh 43.0 - 72.0
Option "DPMS"
EndSection

I copied the file to /etc/X11/xorg.conf, added mode lines, and commented out the HorizSync and VertRefresh lines as follows:
Section "Monitor"
Identifier "Monitor0"
VendorName "Dell"
ModelName "U2410"
ModeLine "1920x1200" 154.00 1920 1968 2000 2080 1200 1203 1209 1235 +hsync -vsync
ModeLine "1280x1024" 193.25 1920 2056 2256 2592 1200 1203 1209 1245 -hsync +vsync
# HorizSync 28.0 - 33.0
# VertRefresh 43.0 - 72.0
Option "DPMS"
EndSection

With the computer running, I reconnected the monitor and computer to the KVM switch. The monitor remained in 1920x1200 resolution mode, and would remain in 1920x1200 mode when switching back and forth with another computer set up at a lower resolution. When I rebooted, however, the highest resolution available was 1600x900. The presence of the xorg.conf file that I created seemed to have no effect on what resolutions were available.

I notice that in the graphical utility Settings>Displays, the monitor is labeled VGA-0. The monitor identification in the xorg.conf file is Monitor0. I tried changing that to VGA-0, but that made no difference.

Some things I found on line seeme to suggest that KDE is using some other method of setting the resolution, but I couldn't find enough information to confirm that, if it even is the case.

I would appreciate any help available to get full resolution through the KVM.

Here is the xorg.conf file that I presently have in my X11 directory:

# nvidia-xconfig: X configuration file generated by nvidia-xconfig ** This is actually the file I created by modifying the file named "xorg.conf.nvidia-xconfig" that I found in /etc/X11.
# nvidia-xconfig: version 418.56

Section "ServerLayout"
Identifier "Layout0"
Screen 0 "Screen0"
InputDevice "Keyboard0" "CoreKeyboard"
InputDevice "Mouse0" "CorePointer"
EndSection

Section "Files"
EndSection

Section "InputDevice"
# generated from default
Identifier "Mouse0"
Driver "mouse"
Option "Protocol" "auto"
Option "Device" "/dev/psaux"
Option "Emulate3Buttons" "no"
Option "ZAxisMapping" "4 5"
EndSection

Section "InputDevice"
# generated from default
Identifier "Keyboard0"
Driver "kbd"
EndSection

Section "Monitor"
Identifier "Monitor0"
VendorName "Dell"
ModelName "U2410"
ModeLine "1920x1200" 154.00 1920 1968 2000 2080 1200 1203 1209 1235 +hsync -vsync
ModeLine "1280x1024" 193.25 1920 2056 2256 2592 1200 1203 1209 1245 -hsync +vsync
# HorizSync 28.0 - 33.0
# VertRefresh 43.0 - 72.0
Option "DPMS"
EndSection

Section "Device"
Identifier "Device0"
Driver "nvidia"
VendorName "NVIDIA Corporation"
EndSection

Section "Screen"
Identifier "Screen0"
Device "Device0"
Monitor "Monitor0"
DefaultDepth 24
SubSection "Display"
Depth 24
EndSubSection
EndSection

[oshunluvr]

We don't really use xorg.conf any more, what we do more often now is create "sections" under /etc/X11/Xsession.d/ and /usr/share/X11/xorg.conf.d/, however xorg.conf should still be read if you make one.

I would start by deleting ~/.xsession-errors and rebooting. Then read through the ~/.xsession-errors file and /var/log/Xorg.0.log and see if there are any hints as to what's happening.

Also, many of us, myself included, have to force X to do what we want with a script that runs after we log in. If you're up and running but at the wrong resolution, try using xrandr to set the resolution correctly. This may mean creating the resolution for X using xrandr also. Once you figure out the series of commands that works, you can put them into a script that can be triggered when needed.