The pam_acct_mgmt function
      is used to determine if the users account is valid. It checks
      for authentication token and account expiration and verifies
      access restrictions. It is typically called after the user
      has been authenticated.
The pamh argument is an authentication handle obtained by a prior call to pam_start(). The flags argument is the binary or of zero or more of the following values:
Do not emit any messages.
The PAM module service should return PAM_NEW_AUTHTOK_REQD if the user has a null authentication token.
User account has expired.
Authentication failure.
The user account is valid but their authentication
            token is expired. The correct
            response to this return-value is to require that the
            user satisfies the pam_chauthtok() function before
            obtaining service. It may not be possible for some
            applications to do this. In such cases, the user should
            be denied access until such time as they can update
            their password.
Permission denied.
The authentication token was successfully updated.
User unknown to password service.
pam_start(3), pam_authenticate(3), pam_chauthtok(3), pam_strerror(3), pam(8)
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                  See Linux-PAM copyright notice for more information.
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