Setting Up NVIDIA Mosaic on Ubuntu

Configuring NVIDIA Mosaic on Ubuntu can enhance your multi-display setup, allowing seamless use of multiple screens as one large desktop. This guide will provide a detailed walkthrough of the steps necessary to successfully install, configure, and troubleshoot NVIDIA Mosaic on Ubuntu.

Prerequisites

• NVIDIA GPU: Ensure that you have a compatible NVIDIA GPU, such as a Quadro or RTX series, that supports Mosaic technology.
• NVIDIA Drivers: It is crucial to have the appropriate proprietary NVIDIA drivers installed. Use the official NVIDIA repository or the Ubuntu graphics drivers PPA to get the latest drivers.
• X Server: The setup requires the use of the X Server for display management. Ensure any other display managers like Wayland are disabled.
• System Preparation: You may need to perform some preparatory steps to ensure a smooth installation.

Preparation Steps

1. Disable Wayland: Edit the GDM configuration file to disable Wayland. Open the terminal and run:

   sudo nano /etc/gdm3/custom.conf

   Uncomment or add the line:

   WaylandEnable=false

2. Blacklist Nouveau Driver: Prevent the Nouveau driver from loading by adding it to the blacklist. Run:

   sudo bash -c 'echo "blacklist nouveau" >> /etc/modprobe.d/blacklist.conf'

   Additionally, blacklist other NVIDIA modules:

   sudo bash -c 'echo "blacklist nvidia" >> /etc/modprobe.d/blacklist.conf'
   sudo bash -c 'echo "blacklist nvidia-drm" >> /etc/modprobe.d/blacklist.conf'
   sudo bash -c 'echo "blacklist nvidia-modeset" >> /etc/modprobe.d/blacklist.conf'

   Update the initial RAM filesystem:

   sudo update-initramfs -u

   And then reboot your system:

   sudo reboot

Installing NVIDIA Drivers

1. Add the NVIDIA PPA: This enables you to install the latest drivers. Use the following commands:

sudo add-apt-repository ppa:graphics-drivers/ppa
sudo apt update

2. Install the NVIDIA Driver: Replace <version> with the appropriate version, for example:

sudo apt install nvidia-driver-525

Reboot your system again:

sudo reboot

3. Install Additional Packages: Ensure the nvidia-settings utility is installed:

sudo apt install nvidia-settings

Configuring NVIDIA Mosaic

After installation, you can configure the displays in Mosaic mode:

1. Open NVIDIA X Server Settings: Launch the application from the terminal:

nvidia-settings

2. Configure Displays for Mosaic: Navigate to the "X Server Display Configuration" section. You should see all connected displays. To set up Mosaic:
1. Select the desired displays.
2. Click on "Configure".
3. Choose "Mosaic" from the available options.
4. Arrange your displays according to your preferred layout (e.g., grid format).
3. Save Configuration: After configuring, click "Apply" and save the changes to the X configuration file:

sudo nvidia-xconfig

Editing Xorg Configuration Manually (Optional)

If finer control over the settings is desired, you may want to manually edit the Xorg configuration:

1. Create/Edit the Xorg Configuration File: Open or create the /etc/X11/xorg.conf file:

sudo nano /etc/X11/xorg.conf

2. Add Device Configuration: Add the following settings under the "Device" section:

Section "Device"
    Identifier "NVIDIA Card"
    Driver "nvidia"
    Option "MetaModes" "1920x1080 +0+0, 1920x1080 +1920+0, 1920x1080 +0+1080, 1920x1080 +1920+1080"
    Option "nvidiaXineramaInfo" "FALSE"
EndSection

3. Modify Extensions Section: Disable RANDR extension:

Section "Extensions"
    Option "RANDR" "Disable"
EndSection

4. Save and Exit: Press CTRL + X, then Y, and Enter.

Once done, reboot your system again:

sudo reboot

Verifying the Setup

Once your system is back up:

1. Run:

nvidia-settings

Check that the displays are properly configured under the Mosaic setup.

Troubleshooting Common Issues

• Black Screen/No Display: If you face a black screen, boot into recovery mode and revert to the original /etc/X11/xorg.conf.
• Single GPU Detection: If only one GPU is shown, ensure both are recognized by the system and double-check the configuration in your xorg.conf.
• Mosaic Not Available: Verify that your drivers are correct and that the GPU supports Mosaic technology.
• Display Tearing: If you experience tearing, ensure your configurations meet SLI or NVLink requirements, as Base Mosaic setups can cause this without proper support.
• Check Logs: Review /var/log/Xorg.0.log for errors that may indicate problems with the NVIDIA drivers or display settings.

Additional Resources

• NVIDIA Driver Downloads
• NVIDIA Mosaic Documentation
• ArchLinux Wiki on NVIDIA Mosaic

Conclusion

By following these steps, you should be able to set up and configure NVIDIA Mosaic on your Ubuntu system successfully. Keep in mind that configurations may vary depending on the specific hardware in use and occasionally require adjustments. Always consult the latest NVIDIA documentation for up-to-date configuration and troubleshooting guidance.