📖 ~1 min read
Table of contents
Symptom & Impact
Firewall controls disappear after restart, exposing services unexpectedly.
Environment & Reproduction
Occurs when nftables service is disabled or overridden by legacy iptables tooling.
Root Cause Analysis
Rules are loaded manually but not bound to persistent startup unit ordering.
Quick Triage
Check nftables unit status and whether /etc/nftables.conf exists and is valid.
Step-by-Step Diagnosis
Inspect boot journal and conflicting firewall services for race conditions.
Solution – Primary Fix
Enable nftables service, persist canonical ruleset, and disable conflicting units.
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Solution – Alternative Approaches
Use a dedicated firewall management role to enforce deterministic startup state.
Verification & Acceptance Criteria
Rules remain loaded across reboot and expected ports are correctly filtered.
Rollback Plan
Restore prior firewall backend and known-good rules backup if connectivity breaks.
Prevention & Hardening
Automate firewall compliance tests after boot and before production admission.
Related Errors & Cross-Refs
Related to legacy iptables persistence conflicts and dropped management access.
Related tutorial: View the step-by-step tutorial for Debian 13.
View all Debian 13 tutorials on the Tutorials Hub →
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
nftables documentation and Debian firewall persistence practices.
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