RHEL 8 Time Drift Despite chronyd Running

📖 ~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 skew causes Kerberos failures, TLS issues, and inconsistent logs across distributed systems. Even small offsets can break authentication-sensitive workflows.

Environment & Reproduction

Often seen on virtualized RHEL 8 nodes with unstable host clocks or blocked NTP traffic. chronyd appears active but offsets keep increasing.

Root Cause Analysis

Poor NTP source quality, network latency asymmetry, or incorrect chrony configuration prevents stable discipline. Hypervisor time sync conflicts can override chrony adjustments.

Quick Triage

Run chronyc tracking and chronyc sources -v, then inspect journalctl -u chronyd for selection and reachability errors. Validate UDP 123 path through firewalld and upstream ACLs.

Step-by-Step Diagnosis

Confirm source reachability, stratum, and jitter values, compare with peer hosts, and check virtualization time settings. Identify whether drift is local oscillator or upstream source related.

Solution – Primary Fix

Correct chrony.conf with reliable pools, disable conflicting host time sync features, restart chronyd via systemctl, and perform controlled makestep where allowed.

Solution – Alternative Approaches

Use internal authenticated NTP hierarchy, deploy dedicated stratum servers, or temporarily pin to trusted local sources during network incidents.

Verification & Acceptance Criteria

Offset stabilizes within defined SLA, chronyc tracking reports normal state, and authentication/log correlation errors disappear. Reboots retain accurate time behavior.

Rollback Plan

Restore prior chrony configuration and restart service if new source set causes instability. Keep backup configs and change windows for time-sensitive platforms.

Prevention & Hardening

Monitor drift metrics continuously, enforce standardized chrony profiles, and test NTP reachability after firewall or routing changes.

Related Errors & Cross-Refs

Related issues include DNS delays, UDP filtering by perimeter firewalls, and VM host clock anomalies. Correlate chrony logs with network telemetry.

Related tutorial: View the step-by-step tutorial for rhel-8.

View all rhel-8 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Review Red Hat chrony documentation and operational recommendations for resilient time synchronization on RHEL 8.