Changing the password in UBUNTU was like a challenge for me. because I had been doing it the manually. I used to go to
SYSTEM > ADMINISTRATION>USERS AND GROUPS
and then change the password for the user.
But when I reboot, the changes would not work!
Today, I was able to do it by going to terminal. This makes me feel little more comfy because, now I do have same password for WINDOWS and UBUNTU as well.
1. to change the root password
2. to change the user password