The slackware /etc/rc.d/rc.bind script has some useful comments.
(extract of relevant bit below)
bind_stop() {
echo "Stopping BIND: /usr/sbin/rndc $RDNC_OPTIONS stop"
/usr/sbin/rndc $RDNC_OPTIONS stop
# A problem with using "/usr/sbin/rndc stop" is that if you
# managed to get multiple copies of named running it will
# only stop one of them and then can't stop the others even
# if you run it again. So, after doing things the nice way
# we'll do them the old-fashioned way. If you don't like
# it you can comment it out, but unless you have a lot of
# other programs you run called "named" this is unlikely
# to have any ill effects:
sleep 1
if ps axc | grep -q named ; then
echo "Using "killall named" on additional BIND processes..."
/bin/killall named 2> /dev/null
fi
}
I would guess that systemd does not have the functionality of the
belt'n'braces bit at the end
Regards, Tim