x11vnc Command Linux: Complete Guide to Remote Desktop Access via VNC Server

The x11vnc command is a powerful Linux utility that allows you to share your existing X11 desktop session via VNC (Virtual Network Computing). Unlike traditional VNC servers that create a new desktop session, x11vnc enables remote access to your current running desktop, making it perfect for remote troubleshooting, administration, and desktop sharing.

What is x11vnc?

x11vnc is a VNC server that provides remote access to an existing X Window System desktop session. It captures the display content of your current X11 session and makes it available to VNC clients over the network. This tool is particularly useful for:

• Remote desktop access and control
• Technical support and troubleshooting
• Screen sharing and demonstrations
• Server administration without physical access
• Accessing GUI applications on headless servers

Installing x11vnc

Before using x11vnc, you need to install it on your Linux system. The installation process varies depending on your distribution:

Ubuntu/Debian

sudo apt update
sudo apt install x11vnc

CentOS/RHEL/Fedora

# For CentOS/RHEL
sudo yum install x11vnc

# For Fedora
sudo dnf install x11vnc

Arch Linux

sudo pacman -S x11vnc

Basic x11vnc Syntax

The basic syntax for x11vnc command is:

x11vnc [options] [display]

Where [options] are various configuration parameters and [display] specifies the X11 display to share (defaults to :0).

Starting x11vnc Server

Basic Usage

To start x11vnc with default settings:

x11vnc -display :0

Expected Output:

26/08/2025 04:08:15 passing arg to libvncserver: -rfbport
26/08/2025 04:08:15 passing arg to libvncserver: 5900
26/08/2025 04:08:15 x11vnc version: 0.9.16 lastmod: 2019-01-05  pid: 12345
26/08/2025 04:08:15 Using X display :0
26/08/2025 04:08:15 rootwin: 0x2a3 reswin: 0x2a3 dpy: 0x7f8b4c000e50
26/08/2025 04:08:15 
26/08/2025 04:08:15 ------------------ USEFUL INFORMATION ------------------
26/08/2025 04:08:15 X DAMAGE available on display, using it for polling hints.
26/08/2025 04:08:15 Wireframe: -wireframe mode is in effect for window moves.
26/08/2025 04:08:15 The VNC desktop is:      hostname:0
26/08/2025 04:08:15 PORT=5900

This starts x11vnc on the default VNC port 5900, sharing display :0.

Setting a Password

For security, always set a password when starting x11vnc:

x11vnc -display :0 -passwd mypassword

Alternatively, you can use a password file:

# Create password file
x11vnc -storepasswd mypassword ~/.vnc/passwd

# Use password file
x11vnc -display :0 -rfbauth ~/.vnc/passwd

Common x11vnc Options

Display and Port Configuration

Security Options

# Run with authentication
x11vnc -display :0 -passwd secretpass -localhost

# Use SSL encryption
x11vnc -display :0 -ssl -sslverify

# Allow specific IP addresses
x11vnc -display :0 -allow 192.168.1.100,192.168.1.101

Advanced x11vnc Usage

Running as Daemon

To run x11vnc as a background daemon:

x11vnc -display :0 -passwd mypass -forever -bg

The -forever option keeps the server running even after client disconnections, while -bg runs it in the background.

Logging and Monitoring

# Enable detailed logging
x11vnc -display :0 -passwd mypass -logfile /var/log/x11vnc.log -verbose

# Monitor connections
x11vnc -display :0 -passwd mypass -connect_or_exit hostname:5900

Performance Optimization

# Optimize for slow connections
x11vnc -display :0 -passwd mypass -noxdamage -noxfixes -noxrandr

# Enable compression
x11vnc -display :0 -passwd mypass -compression 9

Practical Examples

Example 1: Basic Remote Desktop Setup

# Start x11vnc with password protection
x11vnc -display :0 -passwd desktop123 -forever -bg -o /tmp/x11vnc.log

Expected Output:

26/08/2025 04:08:20 x11vnc version: 0.9.16 lastmod: 2019-01-05  pid: 12456
26/08/2025 04:08:20 Using X display :0
26/08/2025 04:08:20 Backgrounding: fork returned: 12457
26/08/2025 04:08:20 VNC server started on port 5900

Example 2: Secure Local Access Only

# Restrict to localhost connections only
x11vnc -display :0 -localhost -passwd localpass -forever -bg

This setup only allows connections from the local machine, perfect for SSH tunneling.

Example 3: SSH Tunnel Setup

First, start x11vnc with localhost restriction:

x11vnc -display :0 -localhost -passwd tunnelpass -forever -bg

Then create SSH tunnel from remote machine:

# On remote machine
ssh -L 5900:localhost:5900 user@server-ip

Now connect VNC client to localhost:5900 on the remote machine.

Security Considerations

Password Protection

Always use strong passwords and consider using password files:

# Create secure password file
x11vnc -storepasswd
# Enter password when prompted
# Password file saved to ~/.vnc/passwd

# Use the password file
x11vnc -display :0 -rfbauth ~/.vnc/passwd

SSL Encryption

# Enable SSL encryption
x11vnc -display :0 -ssl SAVE -sslverify -rfbauth ~/.vnc/passwd

IP Filtering

# Allow specific IP ranges
x11vnc -display :0 -allow 192.168.1.0/24 -deny all

Troubleshooting Common Issues

Permission Denied Errors

If you encounter permission issues:

# Check X11 permissions
xhost +si:localuser:$(whoami)

# Or run with proper authentication
x11vnc -display :0 -auth ~/.Xauthority

Display Not Found

To list available displays:

# Check running X sessions
ps aux | grep Xorg
w
who

Firewall Issues

Open VNC port in firewall:

# UFW (Ubuntu)
sudo ufw allow 5900

# Firewalld (CentOS/RHEL)
sudo firewall-cmd --permanent --add-port=5900/tcp
sudo firewall-cmd --reload

Systemd Service Setup

Create a systemd service for automatic x11vnc startup:

# Create service file
sudo nano /etc/systemd/system/x11vnc.service

Service file content:

[Unit]
Description=x11vnc VNC Server
After=graphical-session.target

[Service]
Type=simple
User=your-username
ExecStart=/usr/bin/x11vnc -display :0 -rfbauth /home/your-username/.vnc/passwd -forever -bg -o /var/log/x11vnc.log
Restart=always
RestartSec=10

[Install]
WantedBy=graphical-session.target

Enable and start the service:

sudo systemctl enable x11vnc.service
sudo systemctl start x11vnc.service
sudo systemctl status x11vnc.service

Performance Monitoring

Connection Statistics

# Monitor with verbose output
x11vnc -display :0 -passwd mypass -verbose -stats

Resource Usage

# Check x11vnc process resource usage
ps aux | grep x11vnc
top -p $(pgrep x11vnc)

Best Practices

1. Always use passwords: Never run x11vnc without authentication
2. Limit access: Use -localhost and SSH tunneling when possible
3. Enable logging: Monitor connections and potential security issues
4. Use SSL: Encrypt connections for sensitive environments
5. Regular updates: Keep x11vnc updated for security patches
6. Firewall configuration: Properly configure network access

Conclusion

The x11vnc command is an essential tool for Linux system administrators and users who need remote desktop access. Its ability to share existing X11 sessions makes it more convenient than traditional VNC servers for many use cases. By following the security best practices and configuration examples provided in this guide, you can set up secure and efficient remote desktop access to your Linux systems.

Remember to always prioritize security when setting up remote access, use strong authentication methods, and consider using SSH tunneling for connections over untrusted networks. With proper configuration, x11vnc provides a reliable solution for remote Linux desktop access and administration.