RHEL 8 Chrony Unsynchronized After Virtual Machine Resume

📖 ~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

After VM resume, RHEL 8 clock drift remains high and chrony reports unsynchronized state, affecting auth, logs, and distributed coordination.

Environment & Reproduction

Observed in virtualized environments with suspended guests and tight drift tolerance. Reproduce by pausing VM long enough to exceed normal slew correction window.

Root Cause Analysis

Default chrony settings may avoid large immediate steps, so resumed guests take too long to converge. Upstream reachability issues can further delay correction.

Quick Triage

Run chronyc tracking, chronyc sources, systemctl status chronyd, and journalctl -u chronyd. Confirm firewalld allows NTP and DNS resolution to source servers.

Step-by-Step Diagnosis

Measure offset magnitude post-resume, inspect makestep policy, and verify source reachability and stratum stability before forcing corrective action.

Solution – Primary Fix

Tune chrony makestep for resume scenarios, restart chronyd if required, and validate rapid re-synchronization. Keep settings aligned with compliance requirements for time adjustment.

Solution – Alternative Approaches

Leverage hypervisor time sync integration with care, shorten poll intervals on resume-sensitive hosts, or route through local stratum servers.

Verification & Acceptance Criteria

Offset returns within policy threshold quickly after resume, synchronized state persists, and dependent auth/logging workflows recover fully.

Rollback Plan

Revert chrony.conf to previous values, restart service, and return to earlier time correction behavior if workload sensitivity requires it.

Prevention & Hardening

Include resume-time sync checks in VM operations, monitor drift alerts, and test chrony policy after hypervisor platform updates.

Related Errors & Cross-Refs

Cross-reference Kerberos clock skew failures, TLS validity issues, and scheduler timestamp anomalies tied to drift events.

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

chrony documentation, Red Hat virtualization and timing guidance, and journalctl references for time-sync troubleshooting.