A graphical display manager must not be installed on RHEL 9 unless approved.

Unnecessary service packages must not be installed to decrease the attack surface of the system. Graphical display managers have a long history of security vulnerabilities and must not be used, unless approved and documented.

Verify that a graphical user interface is not installed with the following command:

$ dnf list --installed "xorg-x11-server-common" Error: No matching Packages to list

If the "xorg-x11-server-common" package is installed, and the use of a graphical user interface has not been documented with the information system security officer (ISSO) as an operational requirement, this is a finding.

Document the requirement for a graphical user interface with the ISSO or remove all xorg packages with the following command:

Warning: If you are accessing the system through the graphical user interface, change to the multi-user.target with the following command:

$ sudo systemctl isolate multi-user.target

Warning: Removal of the graphical user interface will immediately render it useless. The following commands must not be run from a virtual terminal emulator in the graphical interface.

$ sudo dnf remove "xorg*"
$ sudo systemctl set-default multi-user.target