my own solution

------------------------knoppix.sh--------------------------------------
#!/bin/sh
# get the kernel commandline
CMDLINE="$(grep -o -e 'password=[[:alnum:]]\+' /proc/cmdline | sed -e 's/password=//')"
echo "setting rootpassword"
echo "root:$CMDLINE" | chpasswd

# bringing up sshd
/etc/init.d/ssh start
------------------------knoppix.sh---------------------------------------