Hi, three possibilities;
a. Add your command to /etc/rc.local - this is the easiest
b. Write your own init script and install in init.d, then link to /etc/init.d/rc<n>.d (on ubuntu, use "update-rc.d")
c. Add to cron, with "crontab -e" (as root) then add "@reboot /<your script>" at the top, no time information
..