Ubuntu 16.04 LTS intermittent DNS failures with resolvconf

📖 ~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 fails intermittently and applications lose connectivity.

Environment & Reproduction

Ubuntu 16.04 host using DHCP with changing upstream DNS servers.

Root Cause Analysis

Resolvconf updates create inconsistent resolver state under interface changes.

Quick Triage

Check IP reachability first to isolate DNS from network routing issues.

Step-by-Step Diagnosis

Inspect resolv.conf updates, dhclient hooks, and resolver latency.

Solution – Primary Fix

Set persistent DNS servers and restart networking services cleanly.

Solution – Alternative Approaches

Use local caching DNS service with static upstream definitions.

Verification & Acceptance Criteria

Repeated lookup tests complete quickly with no timeout or SERVFAIL.

Rollback Plan

Restore prior resolver and interface configuration backups.

Prevention & Hardening

Monitor DNS response time and avoid mixed resolver ownership.

Related Errors & Cross-Refs

Cross-check against firewall egress blocks and proxy misconfiguration.

Related tutorial: View the step-by-step tutorial for Ubuntu 16.04 LTS.

View all Ubuntu 16.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Ubuntu networking and resolvconf administration references.