/etc/motd의 내용은 pam_motd(8) login(1) 에서 로그인이 성공한 후 로그인 쉘이 실행되기 직전에 보여준다.
The abbreviation "motd" stands for "message of the day", and this file has been traditionally used for exactly that (it requires much less disk space than mail to all users).
On Debian GNU/Linux, dynamic content configured at /etc/pam.d/login is also displayed by pam_exec.
/etc/motd
/etc/pam.d/login