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.
SolutionEdit the /etc/pam.d/common-password file to include the remember option and conform to site policy as shown:
password sufficient pam_unix.so remember=5