To disable X Windows (also known as the X Window System or X11) and the KDE desktop environment during system boot on a Linux system, follow these steps:
Open the /etc/default/grub file in a text editor. This file contains configuration options for the GRUB bootloader.
Look for the GRUB_CMDLINE_LINUX_DEFAULT line and append text to the end of it. For example:
GRUB_CMDLINE_LINUX_DEFAULT="quiet text"
This will boot the system into text mode, rather than starting the X Window System and the KDE desktop environment.
Save the changes and close the file.
Run the following command to update the GRUB configuration:
sudo update-grub
This will apply the changes you made to the /etc/default/grub file.
That's it! X Windows and the KDE desktop environment are now disabled during system boot on your Linux system. Note that this change may not be persistent across reboots, as the /etc/default/grub file may be overwritten by updates or other changes. To make the change permanent, you may need to modify your system's bootloader configuration.