X11 Display Config

Why X11 (not Wayland)?

• Isaac Sim uses Xlib/OpenGL directly, no Wayland support
• XWayland has issues — users switch to X11
• Virtual display setup easier on X11
• Sunshine/Moonlight works better with X11 for unattended access

Current Config

Location: /etc/X11/xorg.conf Backup: /etc/X11/xorg.conf.backup

# Headless virtual display - 2016x1260 (1.5x zoom)

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

Section "Files"
EndSection

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

Section "InputDevice"
    Identifier     "Keyboard0"
    Driver         "kbd"
EndSection

Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Virtual"
    ModelName      "Headless"
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    BoardName      "NVIDIA GeForce RTX 3090"
    BusID          "PCI:1:0:0"
    Option         "AllowEmptyInitialConfiguration" "True"
    Option         "ConnectedMonitor" "DP-0"
    Option         "ModeValidation" "AllowNonEdidModes,NoVirtualSizeCheck,NoMaxPClkCheck"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "AllowEmptyInitialConfiguration" "True"
    SubSection     "Display"
        Depth       24
        Modes      "1920x1080"
    EndSubSection
EndSection

Custom Resolution with EDID Generator

Set a custom resolution (e.g., matching MacBook Pro 14” display):

# Clone EDID generator (if not already done)
cd /tmp && git clone https://github.com/akatrevorjay/edid-generator.git

# Install dependencies
sudo apt-get install -y zsh edid-decode automake dos2unix

# Generate modeline for desired resolution
cvt 2016 1260 60
# Output: Modeline "2016x1260_60.00" 213.00 2016 2152 2368 2720 1260 1263 1269 1307 -hsync +vsync

# Create EDID source file
cd /tmp/edid-generator
echo 'Modeline "2016x1260_60" 213.00 2016 2152 2368 2720 1260 1263 1269 1307 -hsync +vsync ratio=16:10' | ./modeline2edid

# Compile to binary
make 2016x1260_60.bin

# Install EDID
sudo cp 2016x1260_60.bin /etc/X11/edid.bin

# Update xorg.conf with matching modeline, then restart
sudo systemctl restart gdm

Common Resolutions for MacBook Pro 14”

Resolution	Zoom	Use Case
3024x1890	1x	Native (below notch)
2016x1260	1.5x	Comfortable viewing
1512x945	2x	Large UI elements

Troubleshooting

X server not starting

# Check logs
journalctl -u gdm -f

# Check Xorg log
tail -50 /var/log/Xorg.0.log

# Restore backup if virtual display broke things
sudo cp /etc/X11/xorg.conf.backup /etc/X11/xorg.conf
sudo systemctl restart gdm

NVIDIA kernel module failed to initialize

If X fails with “Failed to initialize the NVIDIA kernel module”:

# Check if driver is working
nvidia-smi

# If nvidia-smi works but X fails, restart GDM
sudo systemctl restart gdm

# If nvidia-smi fails, check DKMS
dkms status

# Reinstall DKMS module if needed (use installed driver version)
sudo dkms install nvidia-srv/<driver-version>

Rollback xorg.conf

sudo cp /etc/X11/xorg.conf.backup /etc/X11/xorg.conf
sudo systemctl restart gdm

File Locations

/etc/X11/xorg.conf              # X11 display config
/etc/X11/xorg.conf.backup       # Backup of original config
/etc/X11/edid.bin               # Custom EDID for virtual display
/etc/gdm3/custom.conf           # GDM config (autologin)
/var/log/Xorg.0.log             # X server log
/tmp/edid-generator/            # EDID generator tool (cloned)