Firewall & SSL Management

Distro support

Two-family skill. UFW is the Debian/Ubuntu firewall; the RHEL family (Fedora, RHEL, CentOS Stream, Rocky, Alma, Oracle) uses firewalld — a zone-based model, not a flat allow-list. certbot works on both; only install and the renew timer differ. The body below uses UFW/Debian; full RHEL detail is in references/firewalld-reference.md.