How to Fix xkbcomp Errors in X Server: Causes, Warnings, and Solutions

When working with the X Window System, you might encounter the message:

Errors from xkbcomp are not fatal to the X server

This message indicates that the X Keyboard Compiler (xkbcomp) has encountered an issue while processing keyboard configurations. Fortunately, these errors are not critical and do not prevent the X server from running. However, they may result in unexpected keyboard behavior, such as missing key mappings or non-functional shortcuts.

xkbcomp and Its Role

xkbcomp is responsible for compiling keyboard descriptions and applying them to the X server. It processes keymaps, keycodes, symbols, and layout configurations to define how a keyboard should function. When xkbcomp encounters errors, it can affect:

• Custom key mappings
• Special function keys (e.g., multimedia keys, volume control)
• Alternative keyboard layouts
• Key remapping through XKB configurations

Common Causes of xkbcomp Errors

1. Undefined Keysyms:
   • If xkbcomp encounters an unknown keysym (e.g., XF86AudioMicMute), it generates an error.
   • This often happens when a keysym is referenced in a configuration file but is missing from /usr/share/X11/xkb/symbols/.
2. Unsupported Keycodes:
   • If a keycode exceeds the X11 protocol’s maximum value (255), xkbcomp issues a warning like: Warning: Unsupported maximum keycode 708, clipping.
   • This may occur when using certain gaming keyboards or virtual machines with non-standard key mappings.
3. Redefinition Warnings:
   • Errors like Compat map for group 2 redefined indicate conflicting compatibility maps in XKB configurations.
4. Corrupt or Missing Keyboard Configuration Files:
   • If an XKB configuration file is missing or incorrectly formatted, xkbcomp may fail to apply the keyboard layout properly.
5. Missing xkbcomp Binary or Incorrect Permissions:
   • If xkbcomp is not installed or cannot be executed, you might see: Could not invoke xkbcomp
   • This could be due to incorrect permissions or a missing package.

Keyboard Not Working After startx

If you find that your keyboard stops working after running startx to log into a user account, the issue might be caused by missing keysyms and improper user profile settings. Your X server log may contain warnings such as:

The XKEYBOARD keymap compiler (xkbcomp) reports:
> Warning: Could not resolve keysym XF86CameraAccessEnable
> Warning: Could not resolve keysym XF86CameraAccessDisable
> ...
Errors from xkbcomp are not fatal to the X server
xinit: connection to X server lost

To fix this issue, follow these steps:

• Ensure xkbcomp and related packages are installed:

sudo apt-get install --reinstall xkb-data x11-xkb-utils

• Manually define missing keysyms:

xmodmap -e "keycode 121 = XF86CameraAccessEnable"

• Edit the user account settings to prevent conflicts:
  • Open the user settings file:

sudo nano /var/lib/AccountsService/users/yourusername

• Ensure the line SystemAccount=true is correctly set.
• Restart the X server properly:

sudo systemctl restart display-manager

How to Fix xkbcomp Errors

1. Verify Keyboard Configuration Files

Check if all required keyboard configuration files exist and are correctly formatted:

ls /usr/share/X11/xkb/

If any essential file is missing, reinstall the xkeyboard-config package:

sudo apt-get install --reinstall xkb-data

2. Update or Define Missing Keysyms

If xkbcomp is complaining about undefined keysyms, add them manually to your keymap:

xmodmap -e "keycode 121 = XF86AudioMicMute"

Alternatively, update your keyboard symbol file in /usr/share/X11/xkb/symbols/.

3. Adjust Keycode Ranges

If your keyboard generates keycodes above 255, try remapping them within a supported range using setkeycodes:

sudo setkeycodes e073 190

For a more permanent fix, update your XKB configuration files to limit keycodes.

4. Prevent Compatibility Map Redefinitions

Check for duplicate compatibility maps in your XKB configuration files. If necessary, comment out conflicting entries in /usr/share/X11/xkb/compat/basic.

5. Ensure xkbcomp is Installed and Accessible

If xkbcomp is missing, install it:

sudo apt-get install x11-xkb-utils

Ensure it’s executable:

which xkbcomp
ls -l $(which xkbcomp)

If permissions are incorrect, restore them:

sudo chmod +x $(which xkbcomp)

6. Check X Server Logs

Review X server logs for additional details:

cat /var/log/Xorg.0.log | grep xkb

This can provide insights into specific issues.

Conclusion

Although errors from xkbcomp are not fatal to the X server, they can cause issues with keyboard functionality. By checking configuration files, defining missing keysyms, and ensuring xkbcomp is correctly installed, you can resolve these warnings and maintain a fully functional keyboard setup in your X environment.

If your keyboard stops working after startx, following these troubleshooting steps should help resolve the issue efficiently, ensuring smooth login and full keyboard functionality.