How to Reset Forgotten Password in Ubuntu
When the computer starts booting, press the [Esc] key.
This will show you the boot menu.
Use the Up/Down arrow keys to select Recovery Mode,
then wait for the computer to completely boot up.
You will get a command prompt,
and you will be an administrator.
If you aren’t sure of your username,
just do a directory of the /home folder,
and you will see all of the registered users on the computer.
Once you know the username, now its just a simple matter
of executing the following command:
Put the password
Retype the password
Now you are ready to reboot with your reset password.
After it finishes booting, just enter the password that
you reset it to, and you are in!