Unix background daemons receive commands via signals that are sent to their pid6. bind 4.9.4pl1 understands a number of signals: SIGINT, SIGQUIT, SIGIOT, SIGUSR1, SIGUSR2, SIGHUP, SIGALARM, SIGTERM.
A way to send signals under OS/2 is provided in the Apache httpd port7 in directory Apache/os2/.