Ubuntu 20.04 LTS – DNS resolution fails with Temporary failure in name resolution

📖 ~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

Applications cannot resolve hostnames, causing outbound service failures.

Environment & Reproduction

Common after resolver changes, broken netplan, or upstream DNS outages.

Root Cause Analysis

systemd-resolved configuration or upstream DNS reachability is invalid.

Quick Triage

Test local resolver status, nameserver list, and upstream connectivity.

Step-by-Step Diagnosis

Inspect resolver logs and run targeted DNS queries.

Solution – Primary Fix

Correct nameserver configuration and restart resolver and network stack.

Solution – Alternative Approaches

Configure temporary fallback DNS servers during upstream outage.

Verification & Acceptance Criteria

DNS lookups succeed consistently for internal and external domains.

Rollback Plan

Reapply previous netplan and resolver settings if regressions occur.

Prevention & Hardening

Implement redundant DNS servers and active health checks.

Related Errors & Cross-Refs

Temporary failure in name resolution, server can’t find host, and NXDOMAIN.

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

systemd-resolved, netplan DNS configuration, and resolver troubleshooting docs.