Ubuntu 26.04 LTS – cron jobs skip execution due to wrong timezone and PATH – 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

Scheduled tasks run at unexpected times or fail silently, disrupting operations.

Environment & Reproduction

Often triggered by migration from interactive shell scripts to cron without explicit env.

crontab -l
systemctl status cron

Root Cause Analysis

Cron uses minimal environment and system timezone may differ from expected schedule context.

Quick Triage

Check timezone, cron daemon health, and recent cron logs.

timedatectl
systemctl status cron
journalctl -u cron -n 80 --no-pager

Step-by-Step Diagnosis

Validate job command paths and compare execution environment with shell profile.

crontab -l
which bash python3
cat /etc/crontab
printenv | sort

Solution – Primary Fix

Set explicit TZ and PATH in crontab, use absolute command paths, and log output.

(crontab -l; echo 'TZ=UTC'; echo 'PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin'; echo '*/5 * * * * /usr/bin/bash /opt/jobs/task.sh >> /var/log/task.log 2>&1') | crontab -
sudo systemctl restart cron

Solution – Alternative Approaches

Use systemd timers for richer logging, dependency control, and timezone handling.

systemctl list-timers --all

Verification & Acceptance Criteria

Jobs execute on expected schedule and produce expected output artifacts/logs.

grep CRON /var/log/syslog | tail -n 20
tail -n 20 /var/log/task.log

Rollback Plan

Restore previous crontab backup and restart cron.

crontab /tmp/crontab.backup
sudo systemctl restart cron

Prevention & Hardening

Version-control scheduled tasks and validate runtime env in preflight scripts.

Related Errors & Cross-Refs

Related to locale differences and missing execute permissions on scripts.

Related tutorial: View the step-by-step tutorial for Ubuntu 26.04 LTS.

View all Ubuntu 26.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Ubuntu cron and systemd timer operational documentation.