🟠 High   ⏱ 5–30 min  Last verified: 19 May 2026
Affected versions: RHEL 10.0 RHEL 10.1

📖 ~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

Clock drift breaks Kerberos, TLS validation, and distributed job scheduling reliability.

Environment & Reproduction

Detected on isolated VLANs or after firewall changes to NTP flows.

chronyc tracking && chronyc sources -v

Root Cause Analysis

NTP servers unreachable, chronyd disabled, or large initial drift requiring makestep policy.

Quick Triage

Confirm service status and recent sync attempts in logs.

sudo systemctl status chronyd && sudo journalctl -u chronyd --since -2h

Step-by-Step Diagnosis

Validate peer reachability and inspect /etc/chrony.conf for bad source or ACL settings.

sudo ss -ulpn | grep 123
Illustrative mockup for rhel-10 — chronyc_sources
chronyc sources output — Illustrative mockup — Progressive Robot

Solution – Primary Fix

Correct chrony sources, allow initial makestep, and restart service.

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sudo sed -i 's/^pool/#pool/' /etc/chrony.conf && echo 'server time.cloudflare.com iburst' | sudo tee -a /etc/chrony.conf && sudo systemctl restart chronyd
Illustrative mockup for rhel-10 — chronyd_service_restart
Restarting and validating chronyd — Illustrative mockup — Progressive Robot

Solution – Alternative Approaches

Use internal NTP stratum servers or PTP where sub-millisecond precision is required.

Verification & Acceptance Criteria

Offset stabilizes near zero and chronyc tracking reports normal state.

Rollback Plan

Restore previous chrony.conf and restart chronyd with earlier peer set.

Prevention & Hardening

Monitor time offset metrics and enforce firewall allowances for approved NTP endpoints.

Look for ntpdate conflicts, leap status alarms, and hardware clock drift anomalies.

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.

References & Further Reading

RHEL time synchronization and chrony operations guide.

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