InformationDefines the number of previous passwords that a user may not reuse.
In setting the histsize attribute, it enforces a minimum number of previous passwords a user cannot reuse.
SolutionIn /etc/security/user, set the default user stanza histsize attribute to be (greater than or) equal to 20:
chsec -f /etc/security/user -s default -a histsize=20
This means that a user may not reuse any of the previous 20 passwords.