InformationThe /etc/security/opasswd file stores the users' old passwords and can be checked to ensure that users are not recycling recent passwords. Forcing users not to reuse their past 5 passwords make it less likely that an attacker will be able to guess the password. Note that these change only apply to accounts configured on the local system.
SolutionSet the pam_unix.so remember parameter to 5 in /etc/pam.d/common-password- password [success=1 default=ignore] pam_unix.so obscure sha512 remember=5 Note- The default password setting in this document is the last 5 passwords. Change this number to conform to your site's password policy.