Information
The /etc/security/opasswd file stores the users' old passwords and can be checked to ensure that users are not recycling recent passwords.
- remember=<N> - <N> is the number of old passwords to remember
Requiring users not to reuse their passwords make it less likely that an attacker will be able to guess the password or use a compromised password.
Note: These change only apply to accounts configured on the local system.
Solution
Edit the files /etc/pam.d/system-auth and /etc/pam.d/password-auth:
Add the following line to the password section:
password required pam_pwhistory.so remember=24 enforce_for_root try_first_pass use_authtok
Example password section:
password requisite pam_pwquality.so try_first_pass local_users_only retry=3
password required pam_pwhistory.so remember=24 enforce_for_root try_first_pass use_authtok
password sufficient pam_unix.so sha512 shadow try_first_pass use_authtok
password required pam_deny.so
Note: the use_authtok option should exist on all password lines except the first entry and the pam_deny.so line