[tor-relays] tor-instance-create vs. /etc/tor/torrc

Hi, I use tor-instance-create to spawn a number of relay instances. However, there seems to be one extra instance running - the default one that reads /etc/tor/torrc (and not /etc/tor/instances/INSTANCE/torrc). How do I disable that default tor relay? It opens port 9050 and does who else knows what by default. I can delete /etc/tor/torrc and it seems to do the trick, however, I am not sure how permanent this change will be with automatic package updates. Thanks!