You should make sure that all users have a valid password.
Become superuser.
Display users who have no passwords by using the logins command.
# logins -p |
-p |
Displays a list of users with no passwords. |
The logins command uses the local /etc/passwd file and the NIS or NIS+ password databases to obtain a user's login status.
The following example displays that the user pmorph does not have a password.
# logins -p pmorph 501 other 1 Polly Morph # |