login(1) and /etc/ttys

[guy at gorodish.UUCP]

>Excuse me if this is obvious, but why is it that when there is no entry in
>"/etc/ttys" for the terminal device you are logging in to, no record is made
>of your login in "/etc/utmp"?

Because without an entry in "/etc/ttys", it has no way of knowing
where the record should be made.  Each tty port is assumed to have an
entry in "/etc/utmp" at a fixed location; that location is defined by
the position of that port's entry in "/etc/ttys".  No entry in
"/etc/ttys", no location, and hence no entry.