x11vnc

x11vnc is a free and open-source VNC (Virtual Network Computing) server that allows remote access to a running X11 session. Unlike other VNC servers that create a virtual display, x11vnc shares the existing X server, enabling remote control of the graphical user interface that is actively being used on the physical machine.

This functionality differentiates x11vnc from other VNC servers that create a new virtual desktop. It allows a user to connect to and control the actual desktop environment that is currently displayed on the screen, including any running applications and windows.

x11vnc is often used for remote administration, troubleshooting, remote assistance, and collaborative work scenarios. It can be configured with various security options, including password protection and encryption, to secure the remote connection. It supports various VNC viewers on different operating systems. Because it interacts directly with the existing X server, it requires root or administrator privileges in some configurations.