Re: Dial-in serial getty
On Tue 29 Nov 2022 at 14:12:37 (+0100), Steve Keller wrote:
> For some retro feeling I grabbed my old modem and attached it to the
> phone line. Minicom and dial-out work but now I'd like to allow
> dial-in with a getty waiting on the line.
>
> Systemd has a serial-getty@ service which uses agetty but that doesn't
> work. It seems agetty is just not suited for that job although the
> manual page claims it to be. But I couldn't get agetty to wait for an
> incoming call, answer it, and then send the login prompt. Instead, it
> always immediately sends the prompt, execve()s to /bin/login which then
> terminates after a 60s timeout.
>
> I've now installed mgetty but there is no systemd service file for it.
>
> Should I change the serial-getty@ service to use mgetty or should I
> create a new service for it? In case of the latter, does it suffice
> to only add the .service file or do I need anything else?
I'd certainly try using the service that's already there, just
changing the ExecStart line. I used mgetty for years a couple of
decades ago, and it worked really well. I could dial out from work
to home, and I could use callback to call me at home when I dialled
in to work, logging in with a secret word. (The word selects the
number that it dials back.) In fact, I used callback from anywhere
I happened to be staying if it could receive an external call directly.
To prevent interfering with normal phone use, I set -n to something
like 19 rings, by which time most humans will have given up. (IIRC
this exceeded the number of rings that an internal caller could wait
for pickup, but not external callers.)
Restart=always was important if, like me, you find you have to restart
the modem every so often, otherwise after a few days, it would just
not pick up. I ran the modem off a mechanical timer switch with just
one ¼hr segment set to Off, at ~04:30.
Another wrinkle with callback: don't put ABORT "NO CARRIER" into
the chat script, because you get that string when the modem hangs up
to call back.
It saved a lot of money, as the office could dial National Calls for
a flatrate 10p (IIRC), whereas I would be paying by the minute.
(The Friends and Family tariff would lower the cost of my calls,
but that meant redialling before an hour had passed, else the rate
would go up.)
It also broke the security rules which mandated using a dongle
to log in from off site. Of course, the dongle only worked if you
logged in to a Windows server, and all my machines ran linux.
At that time, interoperability was crude to say the least.
Does this sound suitably retro?
Cheers,
David.
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