Two monitors

taylorkh · 12-12-2015, 08:39 PM

I have two monitors connected to my PC configured to run as separate X sessions according to the Nvidia settings program. It has been working fine in CentOS 6 for 5 years. In fact, I moved from Ubuntu to CentOS as the display configuration quit working when I attempted to move from Ubuntu 9.10 to 10.4. I am now considering moving up to something newer, in this case CentOS 7.

I connected a test SDD in place of the production drive and did an install of CentOS 7 - Gnome desktop. I updated everything, enabled the CR repo, updated to 7.2 and installed kmod-nvidia from elrepo - as called for by nvidia-detect. (several reboots along the way) So far, so good.

I ran nvidia-settings as root and set my small monitor to the left of my large monitor, set it as the primary monitor (I think that was the wording) and then saved the settings in /etc/X11/xorg.conf. I rebooted and found that my small monitor was in fact on the left, had the Panel, menu etc. and that the right monitor acted as an extension of the left monitor (e.g. I could open a program and drag it from the left monitor to the right monitor). Getting closer.

I again ran nvidia-settings and changed the right (larger) monitor to "new X screen", saved the xorg.conf again and rebooted. This time the right monitor came up with a white screen with a picture of a computer screen with a frowning face

(really!) and a message to the effect "A problem has occurred and the system cannot recover." It then stated to logout and try again and presented a logout button. However, the screen did not respond to mouse nor keyboard. I forced a reboot with the power button and came up to the same screen.

That is where I am stuck at. I am glad that CentOS 6 is supported for another 5 years. For what it is worth, here is the xorg.conf as created by nvidia-settings

Code:

# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings:  version 352.63  (buildmeister@swio-display-x64-rhel04-11)  Sat Nov  7 21:59:07 PST 2015

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0" 0 0
    Screen      1  "Screen1" RightOf "Screen0"
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
    Option         "Xinerama" "0"
EndSection

Section "Files"
    FontPath        "/usr/share/fonts/default/Type1"
EndSection

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

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

Section "Monitor"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Acer V193"
    HorizSync       31.0 - 80.0
    VertRefresh     56.0 - 76.0
    Option         "DPMS"
EndSection

Section "Monitor"
    # HorizSync source: edid, VertRefresh source: edid
    Identifier     "Monitor1"
    VendorName     "Unknown"
    ModelName      "Acer X223W"
    HorizSync       30.0 - 83.0
    VertRefresh     56.0 - 76.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "Quadro K420"
    BusID          "PCI:1:0:0"
    Screen          0
EndSection

Section "Device"
    Identifier     "Device1"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "Quadro K420"
    BusID          "PCI:1:0:0"
    Screen          1
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "nvidiaXineramaInfoOrder" "DFP-2"
    Option         "metamodes" "DP-1: nvidia-auto-select +0+0"
    Option         "SLI" "Off"
    Option         "MultiGPU" "Off"
    Option         "BaseMosaic" "off"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Section "Screen"
    Identifier     "Screen1"
    Device         "Device1"
    Monitor        "Monitor1"
    DefaultDepth    24
    Option         "Stereo" "0"
    Option         "metamodes" "DVI-I-1: nvidia-auto-select +0+0"
    Option         "SLI" "Off"
    Option         "MultiGPU" "Off"
    Option         "BaseMosaic" "off"
    SubSection     "Display"
        Depth       24
    EndSubSection
EndSection

Can anyone suggest a path forward?

TIA,

Ken

p.s. This is my new Quadro K420 card which I installed to replace the original GeForce GT220 which came with the machine, is obsolete and has been a source of trouble over the years.

descendant_command · 12-12-2015, 08:48 PM

I think it's working as you want, but gnome is a bit retarded and barfs on running a second instance on the separate screen - maybe there are some options or workarounds for that (I wouldn't be too hopeful - gnome devs seem to have a pretty narrow view of how you should use your computer...).

I'm currently running a separate screen under xfce and it works well (have also used Openbox in the past and it handles that setup great), but when I use Kwin as the WM the second screen instance crashes (not really an issue for me as I just use it for mplayer output which doesn't need borders/title bars etc.).

taylorkh · 12-13-2015, 05:04 AM

Thanks descendant_command,

I agree with your comment re. gnome. I am hoping to run MATE on the thing when all is said and done. I may try building a minimal install of CentOS 7 and then add MATE. I have MATE running on top of gnome on CentOS 7 as a VMWare virtual machine and it looks nice.

Ken

taylorkh · 12-14-2015, 11:12 AM

It gets better and better. Never being one to leave well enough alone I decided to do some further testing. On my CentOS 7.2 Gnome 3 install I started with the original stub xorg.conf file - just a header comment - and started tweaking things one by one, saving the xorg.conf and making a sequentially numbered copy along with notes as to what I had done and what happened when I rebooted. I continued until I broke the thing and then pulled off the collection of config files and did some comparison using a great little tool called Beyond Compare. Unfortunately I could not make sense of things.

For my next trick I decided to see how much effort I wanted to do trying to tweak CentOS 7. My biggest issue with CentOS 6 was the installation of the vlc media player. I had a CentOS 7.2 virtual machine running under VMWare so I tried to install vlc. It worked first time!!! So I am now strongly motivated to get my screens working in 7.2.

This time I did a minimal install of CentOS 7, added the CR repository and upgraded to 7.2. In installed the MATE desktop and the kmod-nvidia package. I started tweaking the nvidia-settings with the minor difference that I overwrote the xorg.conf file rather than merging changes with each attempt.

I have managed to get two separate X sessions working - at least almost - to my liking. Each panel has its own panels. The icons for hone, computer and trash are on the right monitor, not the left and the launchers are duplicated on the right monitor panel. I am playing with fixing these. My notes from the CentOS 6 build remind me that the duplicate launcher issue was present but went away after a couple of reboots. I also had to edit xorg.conf to change which monitor was session 0 and which was 1.

Bottom line I am making good progress.

Ken

fu9ar · 12-14-2015, 11:42 PM

Oddly, something like this (except it worked and had basically separate screens that I could mouse between but not move windows, etc.) spontaneously happened to me once while running fluxbox after installing the proprietary ATI driver from their binary. It is called a multi headed X server.

https://wiki.archlinux.org/index.php/Multihead