🟡 Medium   ⏱ 5–30 min  Last verified: 20 May 2026
Affected versions: RHEL 10.0

📖 ~1 min read

Table of contents
  1. Problem Summary
  2. Symptoms
  3. Diagnostics
  4. Root Cause
  5. Primary Fix
  6. Verification
  7. Prevention
  8. Rollback
  9. Automation
  10. Command Reference
  11. Escalation
  12. Related Notes

Problem Summary

Local DNS service fails to bind because port 53 is already in use.

Symptoms

dnsmasq startup errors show address already in use.

Diagnostics

Use ss -lntup | grep :53 and check conflicting services.

Root Cause

Another resolver service occupies wildcard bind on port 53.

Primary Fix

Disable conflicting resolver or bind dnsmasq to specific interface/IP.

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Illustrative mockup for rhel-10 — rhel10-b02-p49-1
Illustrative mockup — Progressive Robot — Illustrative mockup — Progressive Robot

Verification

Restart dnsmasq and confirm queries succeed with dig.

Illustrative mockup for rhel-10 — rhel10-b02-p49-2
Illustrative mockup — Progressive Robot — Illustrative mockup — Progressive Robot

Prevention

Document resolver ownership on hosts with multiple DNS components.

Rollback

Restore original resolver service if application dependency breaks.

Automation

Enforce single authoritative local resolver through baseline role.

Command Reference

systemctl status dnsmasq; ss -lntup; journalctl -u dnsmasq -b

Escalation

Provide port binding table and resolver configs.

firewalld DNS service settings can mask local binding issues.

Related tutorial: View the step-by-step tutorial for rhel-10.

View all rhel-10 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

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