Ubuntu 26.04 LTS – chrony service not syncing after VM resume – Fix & Prevention

📖 ~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, system clock remains offset and time-sensitive applications fail.

Environment & Reproduction

Observed on suspended virtual machines with delayed network reconnection.

chronyc tracking
chronyc sources

Root Cause Analysis

chronyd does not promptly reacquire good sources after resume event.

Quick Triage

Inspect chrony state and network readiness right after resume.

systemctl status chrony
chronyc activity
ip route

Step-by-Step Diagnosis

Check source reachability and offset history to confirm post-resume degradation.

chronyc sourcestats -v
chronyc tracking
journalctl -u chrony -n 80 --no-pager

Solution – Primary Fix

Force immediate source reacquisition and add resume hook for chrony restart.

sudo systemctl restart chrony
sudo chronyc -a makestep
sudo tee /lib/systemd/system-sleep/99-chrony-resume >/dev/null <<'EOF'
#!/bin/sh
[ "$1" = post ] && systemctl restart chrony
EOF
sudo chmod +x /lib/systemd/system-sleep/99-chrony-resume

Solution – Alternative Approaches

Use systemd-timesyncd for simpler environments with lighter precision requirements.

sudo systemctl disable --now chrony
sudo systemctl enable --now systemd-timesyncd

Verification & Acceptance Criteria

Clock converges quickly after resume and stays synchronized.

chronyc tracking
timedatectl status

Rollback Plan

Remove custom sleep hook and revert to previous time sync behavior.

sudo rm -f /lib/systemd/system-sleep/99-chrony-resume
sudo systemctl restart chrony

Prevention & Hardening

Include resume-time sync checks in VM lifecycle operational runbooks.

Related Errors & Cross-Refs

Related to Kerberos ticket rejection and apt metadata validity errors.

Related tutorial: View the step-by-step tutorial for Ubuntu 26.04 LTS.

View all Ubuntu 26.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

chrony behavior and Ubuntu VM timekeeping recommendations.