USE THESE COMMANDS AT YOUR OWN RISK. IF YOU DON'T UNDERSTAND WHAT THEY DO, DO NOT USE THEM AND GO TO MAN PAGES!

List/reset unsuccessful logins count:

[root@linux ~]# pam_tally --user blah
User blah	(539)	has 20
[root@linux ~]# pam_tally --user blah --reset
User blah	(539)	had 20
[root@linux ~]# pam_tally --user blah
User blah	(539)	has 0

Enforce password change on first login:

[root@linux ~]# chage -d 0 blah