📖 ~1 min read
Table of contents
Symptom & Impact
A critical service shows failed in systemctl, causing application downtime and missed SLAs.
Environment & Reproduction
Ubuntu 20.04 with custom or vendor unit file and startup dependencies on network or mounts.
Root Cause Analysis
Misconfigured ExecStart, missing environment variables, permission issues, or incorrect After/Wants dependencies.
Quick Triage
Run ‘systemctl status ‘ and ‘journalctl -u -b –no-pager’ for immediate failure context.
Step-by-Step Diagnosis
Validate unit syntax with ‘systemd-analyze verify’, inspect drop-ins, and test command manually as service user.

Solution – Primary Fix
Fix unit file path/env, run ‘sudo systemctl daemon-reload’, then restart and enable service.
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Solution – Alternative Approaches
Use a wrapper script with explicit environment and add Restart=on-failure with sane StartLimit settings.
Verification & Acceptance Criteria
Service remains active across reboot, health checks pass, and no recurring errors appear in journalctl.
Rollback Plan
Restore prior unit file from backup and revert daemon-reload changes if regression appears.
Prevention & Hardening
Track unit changes in git, add CI lint for systemd units, and monitor failed unit metrics.
Related Errors & Cross-Refs
Start request repeated too quickly, dependency failed, and permission denied at ExecStart.
Related tutorial: View the step-by-step tutorial for Ubuntu 20.04 LTS.
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Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
man systemd.service, systemctl, journalctl, and Ubuntu service management guide.
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