📖 ~1 min read
Table of contents
Symptom & Impact
After reboot, network is down or interface has no IP, causing service outages and remote access loss.
Environment & Reproduction
Ubuntu 20.04 server using netplan with renderer networkd or NetworkManager and edited YAML under ‘/etc/netplan’.
Root Cause Analysis
Invalid YAML indentation, wrong interface name, or gateway/DNS mismatch prevents netplan from applying routes.
Quick Triage
Use console access, run ‘ip a’, ‘ip route’, and ‘sudo netplan try’ to avoid locking yourself out.
Step-by-Step Diagnosis
Validate files with ‘sudo netplan generate’, verify predictable interface names, and review journalctl for networkd errors.
Solution – Primary Fix
Correct YAML syntax, set proper interface and gateway, then apply with ‘sudo netplan apply’.
Still having issues? Our IT Solutions & Services team can diagnose and resolve this for you. Get in touch for a free consultation.
Solution – Alternative Approaches
Fallback to DHCP for temporary recovery or switch renderer if desktop/server profile changed.
Verification & Acceptance Criteria
Interface has expected IPv4/IPv6, default route exists, DNS resolves, and remote SSH works.
Rollback Plan
Revert to last known-good netplan file from ‘/etc/netplan/*.bak’ and re-apply.
Prevention & Hardening
Use netplan try before apply, keep console/KVM access, and version-control network configuration.
Related Errors & Cross-Refs
systemd-networkd failed, Temporary failure in name resolution, and cloud-init network conflicts.
Related tutorial: View the step-by-step tutorial for Ubuntu 20.04 LTS.
View all Ubuntu 20.04 LTS tutorials on the Tutorials Hub →
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
netplan.io examples, Ubuntu Server networking docs, and systemd-networkd man pages.
Need Expert Help?
If you cannot resolve this yourself, our team offers hands-on Server Management, Managed IT Services, and flexible Support Plans. Contact us today — we respond within one business day.
