Ubuntu 22.04 LTS – systemd service fails at boot because of missing dependency unit – 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

Critical daemon fails to start automatically, causing application outage after reboot.

Environment & Reproduction

Ubuntu 22.04 custom unit file with incorrect Requires/After relations.

Root Cause Analysis

Dependency graph references unavailable unit or wrong startup ordering target.

Quick Triage

Run systemctl status and systemctl list-dependencies on failing unit.

Step-by-Step Diagnosis

Inspect journalctl -u service and verify referenced unit names and targets exist.

Solution – Primary Fix

Correct unit dependencies, run systemctl daemon-reload, then restart and enable service.

Solution – Alternative Approaches

Use ExecStartPre health checks instead of strict Requires where soft dependency is acceptable.

Verification & Acceptance Criteria

Service reaches active state consistently across reboot cycles.

Rollback Plan

Restore previous unit file and disable new override if startup regression occurs.

Prevention & Hardening

Validate unit files with systemd-analyze verify before deployment.

Related Errors & Cross-Refs

Race conditions with network-online.target are frequent related startup issues.

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 22.04 systemd unit dependency and ordering documentation.