📖 ~1 min read
Table of contents
Symptom & Impact
Expected firewall restrictions disappear on reboot, exposing ports and increasing attack surface.
Environment & Reproduction
Observed when ufw service state conflicts with iptables-persistent or custom startup scripts.
Root Cause Analysis
Rule load order and backend conflicts prevent intended policy from being restored at boot time.
Quick Triage
Check ufw status, active backend, and competing startup tasks that overwrite iptables state.
Step-by-Step Diagnosis
Review systemd unit ordering, inspect netfilter tables, and compare saved versus runtime firewall rules.
Solution – Primary Fix
Normalize firewall stack ownership, enable ufw service persistence, and remove conflicting custom rule loaders.
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Solution – Alternative Approaches
Migrate to nftables with managed policy, or centralize firewall enforcement via configuration management.
Verification & Acceptance Criteria
Firewall rules survive multiple reboots and external scan confirms only approved ports are exposed.
Rollback Plan
Restore prior rule snapshots and unit files if service dependencies fail under revised policy order.
Prevention & Hardening
Track firewall changes with version control and test boot-time policy loading in staging first.
Related Errors & Cross-Refs
Compare with docker chain overrides and cloud security-group drift in related network tutorials.
Related tutorial: View the step-by-step tutorial for Ubuntu 18.04 LTS.
View all Ubuntu 18.04 LTS tutorials on the Tutorials Hub →
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
Read UFW docs, netfilter architecture notes, and Ubuntu firewall persistence examples.
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