Linux user cannot login with a password but remove the password and he can

Question

I recently helped someone recover from a lost root password (boot cd), but there is something strange going on. i can add a new user and login as that user. then set a password for that user (as the user) and it is accepted. then log out and it will not accept the password to log in again. remove the password and the user can log in. Something i am missing? But i've thrashed around with it for quite a while and i cant put my finger on it. any push would be appreciated. j

Answer 1

This sort of thing can quite easily happen if both of these conditions are met:

1. The configured keyboard layout differs between the login screen / display manager, and the logged-in session.
2. The password contains characters that are found on different physical keys in the respective keyboard layouts.

The easiest way to rule out #2 is probably to set a password consisting only of digits, as I'm pretty sure all keyboard layouts normally found will emit the same scan codes for the digit keys (both alphanumeric digit keys and numpad digit keys, the latter with Num Lock on).

If you are able to log in with such a password set, then you need to look at why the keyboard layout is configured differently and how to change it so that it matches between the two environments. That will be a different question.

Also, especially if it's a laptop with a combined alphanumeric/numpad keyboard, watch out for Num Lock being turned on by default, as that will almost certainly result in characters different than what you intend are passed to the application (likely the login manager in this case).