If you are running linux, then you may be able to reset the password for the master admin account named 'root'. With that you then can login using the account name of 'root' and that will enable you to reset your actual linux user account name via the user account management configuration program / panel.
See: -
http://linuxconfig.org/recover-reset-forgotten-linux-root-password
If you are running a version of Linux called 'Ubuntu' you may be able to reset your actual user account password as follows:
- Reboot your computer.
- Hold the 'Shift' key during bootup to startup the 'GRUB' menu.
- Highlight your boot image from the displayed and press E to edit.
- Find the line starting with "linux" and append the text rw init=/bin/bash at the end of that line.
- Press Ctrl + X to boot.
- When reboot completes, type in the text 'passwd username' (where username is the actual account name you are attempting to reset).
- Set your password.
or some other methods to try if using Ubuntu are:-
https://help.ubuntu.com/community/LostPassword
Hope that works for you.