startx with "root" and not with "knoppix"

[ix86i]

Hi,
i'm creating my knoppix customization with the good "HOWTO: Remaster Knoppix using Fabian Franz's remaster script"

for error, i have login (inside chroot) as root and not as knoppix and launch startx.

after, i'm go out from kde and i try to launch startx as knoppix user but i have this error:

X: cannot stat /tmp/X11-unix (no such file or directory), aborting.
giving up



where is the problem? how can i start kde as knoppix user?

thank you!