Where the details of Password and Username/Computer Name being Stored in Ubuntu 14.04?
How to Change the Password and the Username?
Ways to recover the forgotten Password and the Username without doing any Harm?
Usernames are stored in
/etc/passwd - so you can look in here to remind yourself what the usernames are - anyone can read this file.
Passwords are stored (hashed) in
To reset a user's password:
sudo passwd <username>
-- it will ask you for a new password.
Last question - erm - don't tell anyone? Not quite sure what sort of suggestion you're looking for here.
If you can't get into the machine at all (so can't look in
/etc/passwd) then you have to reset the root password, with which Google can help.