How to Use the Command `x11vnc` (with Examples)

x11vnc is a powerful utility that enables Virtual Network Computing (VNC) on an existing display server, allowing users to remotely access and control a graphical desktop environment. This tool can be a lifesaver for system administrators and remote workers who need to interact with GUI applications from afar. By default, x11vnc terminates when the last client disconnects, but it offers a plethora of options to customize its behavior to suit various use cases.

Use case 1: Launch a VNC server that allows multiple clients to connect

Code:

x11vnc -shared

Motivation: In environments where multiple users need to view the same desktop session simultaneously, such as in collaborative work settings or educational scenarios, it’s essential to allow multiple clients to connect to the VNC server. Using the -shared option facilitates this requirement by enabling concurrent connections without terminating the session when new users connect.

Explanation:

• -shared: This flag instructs x11vnc to allow more than one client to connect to the server concurrently. Without this option, the server would terminate existing connections when a new client attempts to connect.

Example Output: Upon executing this command, multiple users can connect to the VNC server using their preferred VNC client without interrupting each other’s sessions. Each user will see the same desktop environment in real-time.

Use case 2: Launch a VNC server in view-only mode, and which won’t terminate once the last client disconnects

Code:

x11vnc -forever -viewonly

Motivation: In some circumstances, you might want clients to be able to view the desktop but not interact with it—ideal for demonstrations or when sharing progress with stakeholders without risking unintended interference. Moreover, ensuring the server doesn’t terminate after disconnections can be crucial if the server needs to remain available perpetually.

Explanation:

• -forever: Ensures that the VNC server continues to run even after the last client disconnects. This is useful for maintaining persistent access without needing to restart the server manually.
• -viewonly: Sets the VNC server to a mode where connected clients can only view the desktop but cannot control it. This restricts user interactions to observing changes in the environment.

Example Output: Users connecting with a VNC client can see what happens on the desktop but will not be able to perform any actions. The server remains operational and ready for new connections even after all clients have disconnected.

Use case 3: Launch a VNC server on a specific display and screen (both starting at index zero)

Code:

x11vnc -display :display.screen

Motivation: System administrators who manage machines with multiple display setups might need to specify exactly which display and screen a VNC server should interface with. This flexibility is crucial when dealing with intricate graphical setups often found in advanced computational environments or workstations.

Explanation:

• -display :display.screen: This argument specifies the display and screen the VNC server should connect to. Displays and screens in X11 start counting from zero, so :0.0 would refer to the first display’s first screen.

Example Output: Once the specified display and screen are chosen, the VNC server will interact with that particular graphical output, allowing clients to view or control applications running on that screen only.

Use case 4: Launch a VNC server on the third display’s default screen

Code:

x11vnc -display :2

Motivation: In multi-display environments, administrators or users might need to connect to specific displays for debugging or monitoring purposes. This command is tailored to select the third display (indices start at zero) without concerning the specific screen, assuming the default screen is intended.

Explanation:

• -display :2: The :2 syntax tells x11vnc to connect to the third display’s default screen within an X11 environment.

Example Output: The server offers VNC access to the default screen of the third display, useful for observing specialized applications or setups active on that particular display.

Use case 5: Launch a VNC server on the first display’s second screen

Code:

x11vnc -display :0.1

Motivation: For users dealing with complex display setups where multiple screens are employed under a single display head, being able to target a specific screen is crucial. This use case particularly suits scenarios where different screens serve different tasks and must be accessed individually.

Explanation:

• -display :0.1: Here, :0.1 directs the VNC server to the first display’s second screen, enabling focused access to that screen for monitoring or interaction.

Example Output: The VNC server will show the content of the first display’s second screen to any connected VNC client, allowing targeted actions or observations.

Conclusion:

The x11vnc command provides versatile options for managing remote graphical sessions, enabled by flexible command-line arguments. Whether you need to facilitate collaborative sessions, persistently maintain availability, or navigate complex multi-display environments, x11vnc caters to a wide array of requirements for seamless remote desktop management. By understanding and utilizing its various flags, users can tailor its operation to their specific needs, thereby enhancing productivity and operational efficiency.