@utu

If you want to see the output that is made by startx on /dev/tty5 then you have to modify /etc/init.d/knoppix-startx. I use the tee program to copy that output into a file /var/log/knoppix-startx-dev-tty5.log:
Code:
su -l -c "export STARTUP=$STARTUP ; exec /usr/bin/startx -- vt5 -dpi "$DPI" -br -noreset -nolisten tcp" "$USER" </dev/tty5 2>&1 | /usr/bin/tee -a /var/log/knoppix-startx-dev-tty5.log >/dev/tty6 ; RC="$?"
I also redirect the output to /dev/tty6 so that I am able to read it on the virtual terminal 6.