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XWN740

X-Windows Configuring and Using Using VNC (Chapter 14: Pages 193-198) ‏. XWN740. Agenda. Using VNC: Purpose Using VNC Running VNC Server Running VNC Viewer Running VNC within SSH Tunnel Bypassing a firewall. VNC. VNC - Purpose

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XWN740

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  1. X-Windows Configuring and Using Using VNC (Chapter 14: Pages 193-198)‏ XWN740

  2. Agenda • Using VNC: • Purpose • Using VNC • Running VNC Server • Running VNC Viewer • Running VNC within SSH Tunnel • Bypassing a firewall

  3. VNC • VNC - Purpose • VNC stands forVirtual Network Computerand is an open source technology that provides a low-bandwidth, platform-independent remote display service. • VNC is an amazingly versatile tool. It can be started by non-root users, or configured to start automatically on demand; it can be accessed on a wide range of OS platforms using a native viewer or a portable Java or .Net applet..

  4. VNC • USING VNC vncserver • RealVNC and TightVNC provide a script named vncserver. This script may be run by a regular user, and it starts Xvnc on the local sytem with a preset group of clients. The first available X server number will be used for both the X and VNC display numbers. Since clients are started automatically, the VNC session is always password-protected. • This program is basically the VNC equivalent of the startx command.

  5. VNC • USING VNC Using Xvnc • Xvnc is a combined X server and VNC server. It may be started on a command line like any other X server. This gives you the opportunity to select the specific clients that will be started; it also enables you to choose different VNC and X display numbers, enable or disable the built-in web server, and control the use of passwords. • Running the command vncserver is a wrapper for Xvnc which will prompt the user for a password.

  6. VNC • USING VNC Starting Xvnc from command line • vncpasswd ~/myvncpasswd # (type & verify new password)‏ • Xvnc -query [server-ip] -once – rfbauth ~/myvncpasswdStarting vncserver from command line • vncserver

  7. VNC • USING VNC Starting Xvnc from /etc/inittab • In the same way that character-based logins are run on VTs 1-6, and an X server is started on VT7, it's possible to configure /etc/inittab to start standing X servers at boot time. This provides an easy way for remote users to log in to the system and to have a persistent connection which will remain available across disconnections and re-connections. • When used in this way, Xvnc is usually configured to issue an XDCMP query (often to localhost) and VNC passwords are used.

  8. VNC • Using VNC Starting Xvnc from Inetd • The inetd superserver is used to start services on demand. When used with Xvnc, this provides the opportunity to start as many servers as system resources permit without pre-configuring a set number of standing servers and without wasting any resources on servers that are not needed.

  9. VNC • USING VNC VNC Viewers • Binary VNC viewers are available for many platforms, including PDAs and cell phones. • The Java VNC viewer is designed to be embedded into a web page as an applet. Due to the standard Java applet security restrictions, the embedded applet can only contact the server from which the web page was served; for convenience, Xvnc contains a mini webserver for this purpose. However, this web server cannot be used when Xvnc is started by Inetd, so a separate web server is required when using Inetd and the Java applet.

  10. VNC • USING VNC Starting viewer from command line • Vncviewer [ip-address]:display Starting viewer from Java-enable Browser • Firefox http://[ip-address]:5804(assuming that server is running display 4... i.e. 5800 + display number )‏

  11. VNC Running VNC (Tunneling with SSH)‏ • The minimal security features provided by VNC can be greatly enhanced by tunneling the RFB protocol through SSH. Most native clients support the use of SSH through the -via command-line argument, which configures an SSH tunnel automatically.For example:vncviewer -via username@[IP-address]

  12. VNC Running VNC (Bypassing a Firewall)‏ • Firewalls can pose a problem when using VNC. The simplest and most secure method to solve this problem is through SSH tunneling.First, run the vncviewer to provide a reverse connection:vncviewer -listen Then, start the vncserver to broadcast on port 5500:vncconnect -display :1 [IP-address]:5500

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