unix_update [...]

       unix_update is a helper program for the pam_unix module that updates
       the password of a given user. It is not intended to be run directly
       from the command line and logs a security violation if done so.

       The purpose of the helper is to enable tighter confinement of login and
       password changing services. The helper is thus called only when SELinux
       is enabled on the system.

       The interface of the helper - command line options, and input/output
       data format are internal to the pam_unix module and it should not be
       called directly from applications.


       Written by Tomas Mraz and other various people.

Linux-PAM Manual                  09/19/2013                    UNIX_UPDATE(8)
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