Three writers, one ruleset: reading what the kernel holds
Read the kernel's whole ruleset with nft, find ufw's chains, Docker's and fail2ban's inside it, and let the counters say which rule actually decided.
22 minutesTechnical content last reviewed on 14 Sept 2026
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What this lesson builds
- Knowing what the machine exposes, and closing the rest
- Saying what an output proves, and what it leaves open
- Working out why a service cannot be reached