Ubuntu 14.04 LTS Common Problem 057 – Definitive Diagnosis, Recovery, and Prevention

📖 ~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

Name resolution randomly fails, causing application outages and delayed service discovery.

Environment & Reproduction

Often triggered in mixed DHCP/static setups or after VPN and network restarts.

Root Cause Analysis

Resolver order and transient resolv.conf rewrites point clients to unreachable DNS servers.

Quick Triage

Test direct DNS queries, inspect resolv.conf ownership, and verify upstream resolver health.

Step-by-Step Diagnosis

Trace resolver updates through resolvconf hooks and identify race conditions after interface cycling.

Solution – Primary Fix

Set deterministic resolver order and persistent nameserver configuration, then restart networking.

Solution – Alternative Approaches

Deploy local caching resolver or hardcode resilient public and private DNS fallbacks.

Verification & Acceptance Criteria

Repeated dig and application lookups succeed without timeout or SERVFAIL responses.

Rollback Plan

Restore prior resolver templates and DHCP options from backup snapshots.

Prevention & Hardening

Monitor DNS latency and enforce configuration management for resolvconf files.

Related Errors & Cross-Refs

Tied to apt mirror failures, mail delivery delays, and outbound proxy lookup errors.

Related tutorial: View the step-by-step tutorial for Ubuntu 14.04 LTS.

View all Ubuntu 14.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

resolvconf manual, Ubuntu DNS troubleshooting, and dig/nslookup diagnostic references.