CentOS Stream 9 – Common Problem 056 – Diagnosis and Fix

📖 ~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 lookups time out while ping by IP works.

Environment & Reproduction

After altering /etc/resolv.conf or switching DNS providers.

Root Cause Analysis

systemd-resolved or NetworkManager overwrote the resolver list.

Quick Triage

Check `resolvectl status` and `cat /etc/resolv.conf`.

Step-by-Step Diagnosis

Test with `dig @1.1.1.1 example.com` and `getent hosts`.

Solution – Primary Fix

Set DNS in NetworkManager: `nmcli con mod ipv4.dns ‘1.1.1.1 9.9.9.9’`.

Solution – Alternative Approaches

Disable conflicting `systemd-resolved` if not desired.

Verification & Acceptance Criteria

`dig example.com` resolves with expected servers.

Rollback Plan

Restore prior /etc/resolv.conf from backup if needed.

Prevention & Hardening

Pin DNS at the NM connection level; avoid manual resolv.conf edits.

Related Errors & Cross-Refs

Related to VPN connections and split-DNS issues.

Related tutorial: View the step-by-step tutorial for centos-stream-9.

View all centos-stream-9 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

NetworkManager DNS documentation and systemd-resolved guide.