Hi everyone.
I have root acces to an Ubuntu machine.
This machine have several users so, being root, I can access to their account without knowing their password, simply using
sudo su user
But I need to know the password of a specific user, so in this situation, is there a technique to know what is the user password?
Short answer: No.
Long answer: Unless they have a very very simple password, no.
UNIX does not save the passwords in plain text for obvious security reasons, but hashes them using a salt. For authentications the supplied password is also hashed, and the hashes are compared. If it's a very simple password one could use John the Ripper to crack it, but that's about it. Short of just asking the user that is.
Ok, thank you for the explanation!
May I do an answer here? If you can be root, then you have access to everything! All files and folders of ALL users. Why to want to know others' passwds?