Cron Job Not Running — Troubleshooting Guide

When a cron job doesn't run, the cause is almost always one of these issues: incorrect PATH, wrong permissions, environment variable differences, syntax errors in the crontab, or the cron daemon not running.

Most common fix: Cron runs with a minimal PATH (usually just /usr/bin:/bin). If your script uses commands in /usr/local/bin or other directories, use full paths in your cron command: /usr/local/bin/python3 /home/user/script.py instead of just python3 script.py. Or set PATH at the top of your crontab: PATH=/usr/local/bin:/usr/bin:/bin.

Other common causes: the script isn't executable (chmod +x script.sh), the cron expression has a syntax error (validate with SimpleCronTab first), the cron daemon isn't running (systemctl status cron), or the job runs but produces errors you don't see (redirect output: * * * * * /path/to/script.sh >> /tmp/cron.log 2>&1). Always check /var/log/syslog or journalctl -u cron for cron execution logs.