Ubuntu 18.04 LTS cron jobs stop running due to invalid environment

📖 ~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

Automated maintenance tasks silently fail and backlog accumulates.

Environment & Reproduction

Scripts migrated from interactive shell without absolute paths.

Root Cause Analysis

Cron non-interactive environment lacks expected variables and profile.

Quick Triage

Review syslog cron entries and test command with minimal env.

Step-by-Step Diagnosis

Trace script dependencies and verify executable permissions.

Solution – Primary Fix

Use absolute paths, explicit shell, and required environment exports.

Solution – Alternative Approaches

Move jobs to systemd timers for richer logging and control.

Verification & Acceptance Criteria

Scheduled runs complete on time and produce expected artifacts.

Rollback Plan

Restore prior crontab and script versions from backup.

Prevention & Hardening

Template cron scripts with strict shell options and health checks.

Related Errors & Cross-Refs

Compare timezone drift and lock-file deadlock scenarios.

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

Cron documentation and Ubuntu automation operational standards.