Reset MySQL root password in LAMPP server on Ubuntu

Question

I forgot the password I changed for the root user of MySQL. I'm logged in as root user and when I do
# /opt/lampp/lampp security
it gives result as

XAMPP: Quick security check...
XAMPP: Your XAMPP pages are secured by a password.
XAMPP: Do you want to change the password anyway? [no] n
XAMPP: MySQL has a root passwort set. Fine! :)
XAMPP: The FTP password for user 'nobody' is still set to 'lampp'.
XAMPP: Do you want to change the password? [yes] n
XAMPP: Done.

How do I reset the password. I checked to see, but couldn't find the password in any file (including my.cnf).