Via a serial connection, and either a pair of modems or a "null modem" cable, one system can act as a terminal for another system. This is variously known as "call out" or "dial up". This package contains tools for emulating a real terminal on another system via a serial port.
Call-out is done with ttycallout services, configured to use those devices.
Such a call-out service is a very simple service, which can be managed just like other ordinary services, started and stopped and enabled and disabled in the usual way.
run scripts look like
The run script for such services is basically this (using ttycallout@cuau1 as an example):
#!/bin/nosh setenv TTY /dev/cuau1 setsid open-controlling-terminal --revoke setuidgid --primary-group user-vt-realizer -- user-vt-emulator console-terminal-emulator /dev/vc4"