Time drift causes Kerberos or TLS failures

📖 ~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

Authentication and certificate validation fail when host clock drifts beyond acceptable skew.

Environment & Reproduction

RHEL 7 system with chronyd misconfigured; timedatectl and chronyc tracking show large offset.

Root Cause Analysis

NTP servers unreachable, firewall blocks UDP 123, or chronyd not enabled at boot.

Quick Triage

Check systemctl status chronyd and run chronyc sources -v to inspect reachability and offsets.

Step-by-Step Diagnosis

Review /etc/chrony.conf, test UDP 123 path, and inspect journalctl -u chronyd for sync errors.

Solution – Primary Fix

Set valid NTP servers, allow service with firewall-cmd, then systemctl enable –now chronyd.

Solution – Alternative Approaches

Use local NTP relay in restricted networks and configure iburst for faster initial sync.

Verification & Acceptance Criteria

chronyc tracking reports small offset and secure services no longer fail on time skew.

Rollback Plan

Revert chrony.conf from backup and temporarily set clock manually with timedatectl if needed.

Prevention & Hardening

Alert on offset thresholds and standardize chrony configuration via automation.

Related Errors & Cross-Refs

Clock skew too great, certificate not yet valid, KRB_AP_ERR_SKEW.

Related tutorial: View the step-by-step tutorial for rhel-7.

View all rhel-7 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

chrony documentation, RHEL 7 time services guide, Kerberos time sync requirements.