pam_pwhistory 8 Linux-PAM Manual pam_pwhistory PAM module to remember last passwords pam_pwhistory.so debug use_authtok enforce_for_root remember=N retry=N authtok_type=STRING This module saves the last passwords for each user in order to force password change history and keep the user from alternating between the same password too frequently. This module does not work together with kerberos. In general, it does not make much sense to use this module in conjunction with NIS or LDAP, since the old passwords are stored on the local machine and are not available on another machine for password history checking. debug Turns on debugging via syslog3 . use_authtok When password changing enforce the module to use the new password provided by a previously stacked password module (this is used in the example of the stacking of the pam_cracklib module documented below). enforce_for_root If this option is set, the check is enforced for root, too. remember=N The last N passwords for each user are saved in /etc/security/opasswd. The default is 10. Value of 0 makes the module to keep the existing contents of the opasswd file unchanged. retry=N Prompt user at most N times before returning with error. The default is 1. authtok_type=STRING See pam_get_authtok3 for more details. Only the password module type is provided. PAM_AUTHTOK_ERR No new password was entered, the user aborted password change or new password couldn't be set. PAM_IGNORE Password history was disabled. PAM_MAXTRIES Password was rejected too often. PAM_USER_UNKNOWN User is not known to system. An example password section would be: #%PAM-1.0 password required pam_pwhistory.so password required pam_unix.so use_authtok In combination with pam_cracklib: #%PAM-1.0 password required pam_cracklib.so retry=3 password required pam_pwhistory.so use_authtok password required pam_unix.so use_authtok /etc/security/opasswd File with password history pam.conf5 , pam.d5 , pam8 pam_get_authtok3 pam_pwhistory was written by Thorsten Kukuk <kukuk@thkukuk.de>