106.2 Graphical Desktops

Weight: 1

Goal: Be aware of major graphical desktop environments. Be aware of protocols used to access remote desktop sessions.

This is a low-weight objective — the exam expects awareness, not deep configuration knowledge.

1. Quick Recap: Layers of a Linux Desktop

To put desktops in context, recall the layers from objective 106.1:

┌─────────────────────────────────────┐
│  Desktop environment (GNOME, KDE…)  │  ← what this objective is about
├─────────────────────────────────────┤
│  Window manager                      │
├─────────────────────────────────────┤
│  Display server (Xorg or Wayland)    │
├─────────────────────────────────────┤
│  Linux kernel + graphics drivers     │
└─────────────────────────────────────┘

A desktop environment (DE) bundles a window manager, a panel, a file manager, settings tools, and a set of applications into one consistent user experience.

2. Major Desktop Environments

The exam lists three desktop environments by name. Know them and their distinguishing traits.

KDE (KDE Plasma)

One of the oldest and most feature-rich desktops.
Highly configurable — almost every aspect of the interface can be tweaked.
Built on the Qt toolkit (a C++ GUI library).
Native applications often start with “K”: Konqueror (file manager / browser), Konsole (terminal), Kate (editor), KMail.
Default desktop on distributions like Kubuntu, openSUSE (one of the options), and historically Mageia.

GNOME

Another major desktop, focused on simplicity and a clean, minimal interface.
Built on the GTK toolkit (a C GUI library).
Default desktop on Fedora, Debian (default), Ubuntu (modern versions), RHEL.
Native applications include Files (Nautilus), GNOME Terminal, gedit.

Xfce

Lightweight desktop, designed to be fast and use few resources.
Also built on GTK.
Good choice for older hardware or low-power systems.
Default desktop on Xubuntu and some lightweight distributions.

Quick comparison

Desktop	Toolkit	Style	Resource use
KDE Plasma	Qt	Highly configurable, feature-rich	Moderate
GNOME	GTK	Simple, modern, minimalist	Higher
Xfce	GTK	Traditional, lightweight	Low

You may also encounter LXDE / LXQt, MATE, and Cinnamon in real life — they aren’t required by the objective but are good to recognize.

3. Remote Desktop Protocols

Sometimes you want to use a graphical desktop on another computer over the network. The exam lists three protocols by name.

X11 forwarding

The classic Unix way: covered in detail in objective 106.1.
Uses the X protocol itself to display individual graphical applications from a remote machine on your local X server.
Used via ssh -X user@host.
Note: this forwards applications, not a full desktop. There is no remote login screen — you must already have access via SSH.
Network-transparent design is unique to X11; Wayland does not provide this natively.

VNC (Virtual Network Computing)

Sends the entire desktop screen as bitmap images, plus keyboard and mouse events, over the network.
Uses the RFB (Remote Frame Buffer) protocol underneath.
Cross-platform: VNC clients and servers exist for Linux, Windows, macOS.
Default TCP port: 5900 (and 5900+display number for additional displays).
Common implementations on Linux: TigerVNC, TightVNC, RealVNC, x11vnc.
Basic VNC is not encrypted. For security, tunnel it through SSH or use a VNC variant that supports TLS.

Typical usage:

# On the remote machine, start a VNC server
$ vncserver :1

# On your local machine, connect with a VNC viewer
$ vncviewer remote.example.com:1

RDP (Remote Desktop Protocol)

Microsoft’s protocol, originally for Windows Remote Desktop.
More efficient than VNC because it sends drawing commands rather than full bitmaps.
Default TCP port: 3389.
Encrypted by default.
On Linux, the most common implementation is xrdp — an RDP server that lets Windows users connect to a Linux desktop using the built-in Windows Remote Desktop client.
Linux RDP clients include rdesktop (older) and xfreerdp / FreeRDP (modern).

# Connect from Linux to a Windows or xrdp host
$ xfreerdp /u:user /v:host.example.com

Quick comparison

Protocol	What it sends	Default port	Encrypted?	Typical use
X11 forwarding	X protocol messages	(over SSH)	Yes, via SSH	Run a single Linux app remotely
VNC	Screen pixels + input	5900 (+display)	No (plain), unless tunneled or TLS-enabled	Full remote desktop, cross-platform
RDP	Drawing commands + input	3389	Yes	Mainly Windows; xrdp on Linux

4. Accessibility (Awareness)

The exam expects awareness of accessibility features available on graphical desktops. You don’t need to configure them — just know they exist and roughly what they do.

Feature	Purpose
Sticky keys	Press modifier keys (Shift, Ctrl, Alt) one at a time instead of holding them down. Helps users who can’t press multiple keys simultaneously.
Slow keys	A key only registers if it’s held down for a minimum time. Helps users who accidentally bump keys.
Bounce keys	Ignores repeated key presses within a short time window. Helps users with tremors.
Toggle keys	Plays a sound when locking keys (Caps Lock, Num Lock) change state.
Mouse keys	Move the mouse pointer using the numeric keypad.
High-contrast / large text themes	Visual aid for users with reduced vision.
Screen reader	Reads text on the screen aloud. The standard Linux screen reader is Orca (works with GNOME and others).
Screen magnifier / zoom	Magnifies part or all of the screen.
On-screen keyboard	A keyboard you can click with the mouse. Examples: GOK (GNOME On-screen Keyboard, deprecated), Onboard.
Braille display support	Linux supports refreshable Braille displays via BRLTTY.

These features are usually grouped together as “Accessibility” or “Universal Access” in a desktop’s settings panel.

5. Quick Reference for the Exam

Desktop environments to recognize:

KDE Plasma — Qt-based, highly configurable.
GNOME — GTK-based, simple and modern.
Xfce — GTK-based, lightweight.

Remote desktop protocols to recognize:

X11 forwarding — runs individual X applications over SSH.
VNC — bitmap-based, cross-platform, port 5900.
RDP — command-based, Microsoft origin, port 3389. xrdp is the Linux server.

Accessibility terms to recognize:

Sticky keys, slow keys, bounce keys, toggle keys, mouse keys
Screen reader (Orca), screen magnifier
On-screen keyboard, Braille support (BRLTTY)
High-contrast themes

6. Likely Exam Questions (Self-Check)

Which desktop environment is based on the Qt toolkit? KDE Plasma.
Which desktop environments are based on the GTK toolkit? GNOME and Xfce.
Which of the three major desktops is the most lightweight? Xfce.
What is the default TCP port for VNC? 5900 (plus the display number).
What is the default TCP port for RDP?
Which remote-desktop protocol sends the entire screen as bitmap images? VNC.
Which Linux package provides an RDP server so Windows clients can connect to a Linux desktop? xrdp.
Name two Linux RDP clients. rdesktop (older) and xfreerdp (modern, from the FreeRDP project).
What is the difference between sticky keys and slow keys? Sticky keys let you press modifier keys one at a time instead of holding them down. Slow keys require a key to be held for a minimum time before it registers.
What is Orca? The standard Linux screen reader, used most commonly with GNOME.
Which remote-display method is built into the X11 protocol itself? X11 forwarding (typically over SSH with ssh -X).
Is plain VNC encrypted? No. It is usually tunneled through SSH or configured with TLS for security.