Ubuntu 20.04 LTS Cloud-Init Rewrites Network on Reboot

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

Static network changes disappear after reboot, leading to intermittent connectivity and failed service bindings on cloud hosts.

Environment & Reproduction

Occurs on images with active cloud-init network modules when administrators also maintain local netplan files manually.

Root Cause Analysis

Cloud-init datasource metadata re-applies network definitions at boot, overriding local configuration without explicit disable controls.

Quick Triage

Determine whether cloud-init owns network configuration and inspect boot logs for module stages rewriting netplan artifacts.

Step-by-Step Diagnosis

Review cloud-init logs, datasource metadata, and generated netplan files to confirm overwrite source and timing.

Solution – Primary Fix

Disable cloud-init network config management where appropriate, persist local netplan definitions, and regenerate network state.

Solution – Alternative Approaches

Manage network purely through cloud-init templates, or use immutable image pipelines with metadata-driven interface assignment.

Verification & Acceptance Criteria

Network configuration should remain unchanged across reboot and instance lifecycle events while expected routes and DNS persist.

Rollback Plan

Re-enable cloud-init network modules if platform automation requires them, then reconcile local settings with metadata policies.

Prevention & Hardening

Define ownership model between image config and cloud metadata, and document lifecycle-safe network customization procedures.

Related Errors & Cross-Refs

Related scenarios include DHCP lease churn, interface rename issues, and netplan renderer conflicts on cloud instances.

Related tutorial: View the step-by-step tutorial for Ubuntu 20.04 LTS.

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Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Use cloud-init network configuration documentation and Ubuntu cloud operations guides for predictable boot-time network behavior.