An important need for me on my system is the remote connection via VNC.
I commonly use Kubuntu but krfb is basically useless because of 100% CPU usage (at least to 5 PC`s I have tried it)
So a very simple solution is to setup x11vnc as krfb alternative with exactly the same behavior (Enable VNC per user when he logs in).
That is generic for KDE
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With the following tip you can make something startup per user when this user logs into KDE!!
There is a folder under everyone`s home directory called ".kde/Autostart"
Generally if you type
Code:
cd ~/.kde/Autostart
You should be there 
In this folder you can make bash scripts or symbolic links that are executed everytime this user logs in his KDE Desktop environment
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The following is specifically for x11vnc
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First of all you need to disable krfb if you are using it.
Then apt-get the x11vnc package so do:
Code:
sudo apt-get install x11vnc vncserver
Then you need to create the password that you will be using when you are trying to login to your x11vnc server. type the following in a terminal:
Then you have to create the startup script and place it under ~/.kde/Autostart/x11vnc
Code:
kate ~/.kde/Autostart/x11vnc
Paste the following lines into the file:
Code:
#! /bin/sh
x11vnc -rfbauth ~/.vnc/passwd -bg -forever -noxdamage -shared &
Save the file and exit. Then make the above file executable by using the following command:
Code:
chmod 700 ~/.kde/Autostart/x11vnc
And it is ready
Now restart KDE and x11vnc will start automatically instead of krfb!!!
EXTRA TIPS THAT YOU MAY NEED
If you also need a tray icon to be able to check when someone is logging into your VNC server just change the "~/.kde/Autostart/x11vnc" contents as emanaton describing on the quote below.

Originally Posted by
emanaton
Greetings All,
Most excellent article! For myself, I require the functionality described herein as well as some notification of VNC activity. I've achieved this by expanding my apt-get install to include "tk8.4" (for the needed "wish" scripting support) as follows:
Code:
sudo apt-get install x11vnc vncserver tk8.4
and expanded ~/.kde/Autostart/x11vnc as follows:
Code:
#! /bin/sh
x11vnc -rfbauth ~/.vnc/passwd -bg -accept "popup" -gone "popup" -rfbport 5900 -gui tray=minimal,iconfont=14x17 -forever -noxdamage -shared &
Not only does this provide on-screen verification to allow or disallow connections, it also provides an ugly tray icon that changes color whenever someone connects! Of course, if you don't care about receiving such notifications then remove the "accept" and "gone" arguments.
Enjoy!
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# Updated 2007-11-28