CentOS Stream 10 – Common Problem 229 – 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

Custom DNS entries placed in /etc/resolv.conf are reverted every time NetworkManager activates a connection.

Environment & Reproduction

Occurs on hosts where administrators manage DNS manually but leave NM in default rc-manager mode.

Root Cause Analysis

NetworkManager regenerates resolv.conf from connection profiles unless its dns plugin is changed.

Quick Triage

Inspect /etc/NetworkManager/conf.d for dns settings and review nmcli connection show ipv4.dns values.

Step-by-Step Diagnosis

Run: nmcli connection show | grep -i dns; cat /etc/NetworkManager/NetworkManager.conf.

Solution – Primary Fix

Set dns=none in NetworkManager.conf or configure ipv4.dns on the active connection and reload.

Solution – Alternative Approaches

Use systemd-resolved with NetworkManager dns=systemd-resolved for split DNS and stub resolver behaviour.

Verification & Acceptance Criteria

resolv.conf survives nmcli connection up and reboot, and dig returns expected resolvers.

Rollback Plan

Reset dns plugin to default and re-add DNS via connection profile if manual control is removed.

Prevention & Hardening

Define DNS in connection profiles or via DHCP options to eliminate manual file edits.

Related Errors & Cross-Refs

Linked to systemd-resolved conflicts and DHCP-supplied DNS overrides.

Related tutorial: View the step-by-step tutorial for centos-stream-10.

View all centos-stream-10 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

NetworkManager.conf(5) and Red Hat networking guide DNS sections.