Load a Kernel Module Persistently

A firewall/bridge feature needs the br_netfilter kernel module loaded — and it has to survive reboots, not just this session. The persistent way is a drop-in under /etc/modules-load.d/: any module named (one per line) in a *.conf there is loaded at boot.

echo br_netfilter | sudo tee /etc/modules-load.d/br_netfilter.conf

(modprobe br_netfilter loads it right now, but only until reboot — the drop-in is what makes it persistent.) Grading reads /etc/modules-load.d/ the way systemd-modules-load does.