🟡 Medium   ⏱ 5–30 min  Last verified: 19 May 2026

📖 ~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 breaks TLS validation, Kerberos, and scheduled automation. Package repositories may reject connections due to invalid certificate times.

Environment & Reproduction

Ubuntu 22.04 with disabled NTP or unreachable time servers. Reproduce by stopping systemd-timesyncd and setting incorrect manual time.

Root Cause Analysis

Without reliable NTP sync, VM pause/resume and drift accumulate. Authentication and cryptographic checks become unreliable.

Quick Triage

Run timedatectl status and check NTP sync state. Validate upstream NTP reachability at network level.

Step-by-Step Diagnosis

Inspect journalctl -u systemd-timesyncd -b, verify configured NTP servers in timesyncd.conf, and compare against trusted external time source.

Illustrative mockup for ubuntu-22-04-lts — ubuntu2204-common-problem-11-ntp-01.webp
System clock drift causes TLS and authentication failures. — Illustrative mockup — Progressive Robot

Solution – Primary Fix

Enable synchronization with sudo timedatectl set-ntp true, configure valid NTP pools, then restart systemd-timesyncd and verify synchronization.

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Illustrative mockup for ubuntu-22-04-lts — ubuntu2204-common-problem-11-ntp-02.webp
Restore time sync using timedatectl and systemd-timesyncd. — Illustrative mockup — Progressive Robot

Solution – Alternative Approaches

Use chrony in environments requiring advanced clock discipline or intermittent connectivity.

Verification & Acceptance Criteria

timedatectl reports synchronized clock, TLS handshakes succeed, and time-sensitive jobs run without skew errors.

Rollback Plan

Revert to previous NTP config and restore earlier daemon choice if compatibility issues occur.

Prevention & Hardening

Maintain redundant NTP sources, monitor drift thresholds, and enforce time-sync policy in baseline images.

certificate is not yet valid, clock skew too great, timedatectl unsynchronized.

Related tutorial: View the step-by-step tutorial for Ubuntu 22.04 LTS.

View all Ubuntu 22.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Ubuntu time synchronization docs, man timedatectl, systemd-timesyncd service references.

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