problem during remastering of Knoppix

i was trying to create an user in chroot environment for installation of a few packages. all went perfect at first; but after i restarted my computer, it's not running... here is the procedure i followed:

i have created a folder "knoppix" under /home in chroot environment and copied all the contents of /etc/skel to the newly created directory.

cp -Rp /etc/skel /home/knoppix

chown -R knoppix:knoppix /home/knoppix

chmod 777 /tmp

to install some packages as "knoppix" user, i wrote the following to make knoppix as the super user

su - knoppix

the above " su - knoppix" command ran well last time. but now after i have restarted my computer it's showing some continues errors as " -su: /dev/null: Permission denied"

i have also tried the whole process again, but still it's giving the same error message.