Install VNC on a Cloud Server

  • Last updated on: 2016-01-13
  • Authored by: Rackspace Support

This page explains how to install VNC on your Cloud Server. This article was based upon the CentOS 5 distribution. This tutorial assumes you have root access to your server and are running on a clean installation.

Note: In order to use this you must have at least 512MB of RAM or X Windows will not run.

Warning: Running VNC on your Cloud Server will consume large amounts of bandwidth. Please use wisely!

If you would like information about tunnelling VNC over SSH please visit

Install the Necessary Packages

  • Install perl with the following command:

     yum install perl
  • Install X Windows

We will need to install the X-Windows platform to run the graphical portion of this project. X11 is a graphical display server, and will server and will sit above the Window Manager.

To install run the following as root:

    yum groupinstall "X Window System"
  • Install a Window Manager

Window Managers and are the human usable layer that you are probably familiar with. This gives you the access to use a mouse and send calls to the X11 server. - KDE - GNOME - TWM

  • Install KDE Desktop

     yum groupinstall "KDE Desktop"

Also, this may be needed:

    yum install kde-session
  • Install GNOME Desktop Environment

     yum groupinstall "GNOME Desktop Environment"

Also, this may be needed:

    yum install gnome-session
  • Install TWM

TWM is the default X-Window Manager and you don’t have to install any additional packages, it is light and will run on almost anything, but is also not very user friendly and almost requires a power-user.

  • Install VNC Server

VNC is the service that display your X output to a tcp connection over the internet.

    yum install vnc-server


Configure VNC

Modify the /etc/sysconfig/vncservers configuration file by performing the following command:

nano /etc/sysconfig/vncservers

Insert the following lines into the file:

VNCSERVERARGS[1]="-geometry 800x600 -depth 16"

This will create a VNC session for one user with the username of someguy. If you would like to setup multiple users you will need to add additional users to that line. For example:

1:someguy 2:someperson 3:somegirl

You will also need to add additional VNCSERVERARGS lines to correspond to each user. Change the [1] to match the session number.

Configure firewall

If you have a firewall running, you will need to open port 5901. For example, on CentOS, run:

iptables -I INPUT 1 -p tcp --dport 5901 -j ACCEPT

If needed, replace 5901 with a range, depending on the number of sessions required (e.g. 5901:5905).

Save the new iptables rule:

service iptables save

Test the Server

  1. Switch to your User

    su username
    cd ~
  2. Create a .vnc directory

    mkdir .vnc
    cd .vnc

    Note: Rake note of the ‘.’ in front of the name.

  3. Create the xstartup file

Insert the configuration below (this is for a KDE-VNC session):

   exec /etc/X11/xinit/xinitrc
   [ -x /etc/vnc/xstartup ] && exec /etc/vnc/xstartup
   [ -r $HOME/.Xresources ] && xrdb $HOME/.Xresources
   xsetroot -solid grey
   vncconfig -iconic &
   xterm -geometry 80x24+10+10 -ls -title "$VNCDESKTOP Desktop" &

   startx &
   exec kde-session &

- If you are using GNOME, change 'kde-session' to 'gnome-session'

- Make the file executable:

       chmod u+x xstartup
  1. Setup your VNC user

Set the user’s private VNC connection password


You will be required to confirm your password.

  1. Start the VNC server

Make sure you exit out of your user session and go back to ‘root’.

Start the server:

    service vncserver start

You may see some error messages here stating ‘unexpected EOF’ or syntax errors – these are normal. If you see [ OK ] then the service has started properly.

  1. Connect to your VNC

Open up your VNC client and type in your external IP address, colon, then your session ID configured in /etc/sysconfig/vncservers. The session number must correspond to the user name or it will not connect.


Type in the password you chose with vncpasswd and you will be connected.

To close the connection simple close the window.

  1. Stopping the VNC Server

To stop the VNC server type the following:

    service vncserver stop

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