In case you forgot your Ubuntu password, here is a quick, easy way to reset it:
- Start your computer; pay close attention to boot promts
- When your computer boots to the GRUB screen, looks like below

=> use your up/down arrow keys on your keyboard to select any line that has (single-user mode)
- Once you got a line with (single-user mode) selected, hit Enter
- When the “Recovery Menu” pops up, use the Down arrow key and select “root Drop to root shell prompt”

- Once selected, press the Tab key; this would highlight <Ok> => Once Ok is selected, press Enter

- A shell prompt would appear. We can now use the “passwd” command to reset password. Make sure to replace “your_username” with the username you used to login to your Ubuntu.
passwd your_username (i.e. password stephen and hit Enter) Enter new UNIX password: (enter your password and hit Enter) Retype new UNIX password: (enter your password and hit Enter) passwd: password updated successfully => you are done.
Now type this to restart your computer:
reboot