Many times we have a server set up manually with a Gnome or KDE GUI that isn’t necessary on most reboots. After all, GUIs can take up system resources that we may want for something else, such as gaming, mining, or computing projects. Fortunately, turning it off in Ubuntu is as simple as editing the grub configuration file so that the machine boots into command line interface mode only, or CLI.
and then make the following edits:
1. find and disable GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" by commenting it out. (do this by typing # at the beginning of the line)
2. find and change GRUB_CMDLINE_LINUX="" to GRUB_CMDLINE_LINUX="text"
3. find and uncomment the line GRUB_TERMINAL=console
Once you are finished, save and exit (in nano use ctrl-x) and then update Grub and reboot with: