📖 ~1 min read
Table of contents
Symptom & Impact
Host can reach IP addresses but hostname lookups fail, breaking package updates, APIs, and service discovery.
Environment & Reproduction
Often appears after manual edits to /etc/resolv.conf or conflicting netplan DNS entries.
Root Cause Analysis
Stub resolver link, upstream DNS list, or symlinked resolv.conf state becomes inconsistent with systemd-resolved expectations.
Quick Triage
Verify resolver service health and active nameserver assignment.
Step-by-Step Diagnosis
Inspect per-link DNS and query behavior to isolate link-level or global resolver faults.
Solution – Primary Fix
Restore expected resolv.conf symlink, correct netplan DNS entries, and restart networking services.
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Solution – Alternative Approaches
Use static nameservers in netplan for isolated networks where DHCP DNS is unreliable.
Verification & Acceptance Criteria
Forward and reverse lookups succeed and application endpoints resolve consistently.
Rollback Plan
Revert netplan YAML from backup and reapply if new DNS set introduces regressions.
Prevention & Hardening
Manage DNS through netplan only and avoid direct manual edits to generated resolver files.
Related Errors & Cross-Refs
Frequently coincides with cloud-init network rewrites and VPN client DNS takeover.
Related tutorial: View the step-by-step tutorial for Ubuntu 22.04 LTS.
View all Ubuntu 22.04 LTS tutorials on the Tutorials Hub →
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
Ubuntu and systemd-resolved documentation on resolver architecture and netplan integration.
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