PAM_PWHISTORY(8)          (06/08/2020)           PAM_PWHISTORY(8)

     NAME
          pam_pwhistory - PAM module to remember last passwords

     SYNOPSIS
          pam_pwhistory.so [debug] [use_authtok] [enforce_for_root]
                           [remember=N] [retry=N]
                           [authtok_type=STRING]

     DESCRIPTION
          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.

     OPTIONS
          debug
              Turns on debugging via syslog(3).

          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_authtok(3) for more details.

     MODULE TYPES PROVIDED
          Only the password module type is provided.

     RETURN VALUES

     Page 1                  Linux-PAM Manual        (printed 5/25/22)

     PAM_PWHISTORY(8)          (06/08/2020)           PAM_PWHISTORY(8)

          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.

     EXAMPLES
          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

     FILES
          /etc/security/opasswd
              File with password history

     SEE ALSO
          pam.conf(5), pam.d(5), pam(7) pam_get_authtok(3)

     AUTHOR
          pam_pwhistory was written by Thorsten Kukuk
          <kukuk@thkukuk.de>

     Page 2                  Linux-PAM Manual        (printed 5/25/22)