Fix Frozen CentOS 7 GUI: Quick Fixes

1. Restart the graphical interface by pressing Ctrl + Alt + F2 to switch to a new terminal window, then switch back to the graphical interface with Ctrl + Alt + F1 to see if it can be restored to normal.
2. Forcefully close a frozen program: If a specific program is causing the graphical interface to freeze, you can try using the kill command in the terminal window to close that program, for example: killall program_name.
3. Reboot the X window system: You can try restarting the X window system using the command, such as: sudo systemctl restart display-manager.service.
4. Check system resources: The graphics interface may be lagging due to insufficient system resources. Use the htop or top command to check resource usage and try releasing some resources.
5. Update graphics card driver: If the graphical interface is stuck due to a graphics card driver issue, try updating the graphics card driver.

If none of the above methods can resolve the issue, it may be necessary to reboot the system or reinstall the graphical interface.