Ubuntu 18.04 LTS – Docker daemon fails after kernel update with cgroup issues – 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

Containers do not start because dockerd cannot initialize cgroups.

Environment & Reproduction

Ubuntu 20.04 host upgraded kernel/runtime with existing Docker config.

Root Cause Analysis

Cgroup mode mismatch between kernel, Docker, and container runtime settings.

Quick Triage

Read journalctl for docker.service and inspect daemon config values.

Step-by-Step Diagnosis

Compare cgroup driver and hierarchy settings across system components.

Solution – Primary Fix

Align daemon cgroup driver with host mode, reload config, restart Docker.

Solution – Alternative Approaches

Pin kernel/runtime versions until full migration plan is validated.

Verification & Acceptance Criteria

Docker starts cleanly and test containers run without cgroup errors.

Rollback Plan

Restore prior daemon.json and package versions if startup regresses.

Prevention & Hardening

Test kernel and container runtime compatibility in staging before rollout.

Related Errors & Cross-Refs

Kubelet startup failures often share the same cgroup mismatch root cause.

Related tutorial: View the step-by-step tutorial for Ubuntu 18.04 LTS.

View all Ubuntu 18.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Docker and Ubuntu cgroup compatibility documentation.