Ubuntu 20.04 LTS Cron Jobs Miss Scheduled Run

📖 ~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 and business workflows fail silently, causing stale data and missed SLAs.

Environment & Reproduction

Triggered by malformed crontab syntax, PATH assumptions, timezone drift, or permission constraints.

Root Cause Analysis

Cron executes in minimal environment; command dependencies and schedule parsing often break jobs.

Quick Triage

Validate crontab entries, check mail output and logs, and test command under cron-like environment.

Step-by-Step Diagnosis

Trace runtime environment, file permissions, and shell invocation behavior to identify failure point.

Solution – Primary Fix

Correct schedule syntax, use explicit paths, and add robust logging and error handling in scripts.

Solution – Alternative Approaches

Migrate critical jobs to systemd timers with dependency and status integration.

Verification & Acceptance Criteria

Jobs execute on schedule with expected outputs and alerting on non-zero exit conditions.

Rollback Plan

Restore prior crontab from backup and re-enable legacy schedule if needed.

Prevention & Hardening

Adopt standardized job wrappers and monitor schedule drift and task health.

Related Errors & Cross-Refs

Connected to timezone misalignment and shell profile-dependent command failures.

Related tutorial: View the step-by-step tutorial for Ubuntu 20.04 LTS.

View all Ubuntu 20.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Refer to cron and systemd timer documentation for reliable scheduled task design.