LPIC-1 102-500: Interfaces and Desktops

What the exam tests

Interfaces and Desktops covers X11 and Wayland fundamentals, display managers, desktop environments, remote display access, and accessibility settings. The exam favors configuration locations and diagnostic commands over GUI clicking.

Core rules

X11 uses a display server and clients; DISPLAY=:0 means local display 0. xhost controls host-based access, while xauth manages MIT-MAGIC-COOKIE credentials. Prefer xauth over xhost +.
Modern Xorg reads /etc/X11/xorg.conf and drop-in files under /etc/X11/xorg.conf.d/. Most hardware is autoconfigured; xdpyinfo and xwininfo inspect a running display.
Wayland is a protocol with compositors such as GNOME Mutter, KDE KWin, and Sway. XWayland allows legacy X11 clients. XDG_SESSION_TYPE reports x11 or wayland.
Display managers include GDM, LightDM, SDDM, and XDM; they start the graphical session after boot. Desktop environments include GNOME, KDE Plasma, Xfce, and LXDE.
Accessibility features include Orca screen reader, high-contrast themes, large text, sticky keys, slow keys, bounce keys, mouse keys, and toggle keys. Many map to AccessX/XKB settings and can be enabled per user.

Worked example

A remote user needs to run xeyes on server lab from workstation ws1. On lab, run xauth list to find the cookie for :0, merge it on ws1 with xauth add, set DISPLAY=lab:0, then start xeyes. Reason: X11 authorization is cookie-based; xhost +lab would grant broad host access without per-user authentication and is a security trap.

Traps

DISPLAY=:0 is not the same as DISPLAY=localhost:10 used by SSH X11 forwarding. Do not edit xorg.conf first when autodetection works. Wayland sessions can block tools that assume X11; check XDG_SESSION_TYPE. Accessibility options are per-user and may not apply at the login greeter. xhost + disables access control; avoid it.