Write an init script and link it to your default run level's runcontrol folder. Just make a new text file with this in it:

#!/bin/sh
su -c "vncserver -geometry 1024x768 -name knoppix:1" knoppix


name the script something... vnc1024 in this example. Note: that vnc command may not be quite correct.... I'll check on it and edit if if necessary. A good place to save this is /usr/local/bin (so all users with that in their PATH can use it as a regular system command).

chmod +x vnc1024

^ makes it executable for all users.

as root:

ln -s /usr/local/bin/vnc1024 /etc/rc5.d/S98vnc1024

^ links it to the run control for graphical mode.