Stop cloud-init from Overwriting Network Settings on Ubuntu 26.04 LTS

📖 ~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

Manual netplan changes revert after reboot. IP, DNS, or routes return to cloud-provided defaults.

Environment & Reproduction

Common on cloud images where cloud-init generates network files on first and subsequent boots.

Root Cause Analysis

cloud-init datasource applies network configuration and overwrites local admin netplan files.

Quick Triage

Run cloud-init status –long and inspect /etc/netplan/50-cloud-init.yaml for generated settings.

Step-by-Step Diagnosis

Review cloud-init logs in /var/log/cloud-init.log and check datasource metadata with cloud-init query ds.

Solution – Primary Fix

Create /etc/cloud/cloud.cfg.d/99-disable-network-config.cfg with ‘network: {config: disabled}’, then define your own netplan YAML and run sudo netplan apply.

Solution – Alternative Approaches

Keep cloud-init enabled but set desired static network in instance metadata where platform allows it.

Verification & Acceptance Criteria

After reboot, custom netplan remains unchanged and interface configuration matches expected static settings.

Rollback Plan

Remove disable file and regenerate cloud-init defaults with sudo cloud-init clean –logs, then reboot.

Prevention & Hardening

Document whether image instances are cloud-init managed before local network edits.

Related Errors & Cross-Refs

Related symptoms include recurring DHCP assignment and overwritten /etc/netplan files.

Related tutorial: View the step-by-step tutorial for Ubuntu 26.04 LTS.

View all Ubuntu 26.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

cloud-init docs for network configuration and Ubuntu cloud image documentation.