cron

Dump another user's crontab Inspect a service account's jobs as root; note: -u needs root or sudo crontab -l -u <name> 2>/dev/null || echo 'no crontab' #cron#troubleshooting#security Run job at boot Append @reboot job idempotently; note: no networking guarantee at boot, use systemd for deps ( crontab -l 2>/dev/null; echo '@reboot /usr/local/bin/warmup.sh' ) | crontab - #cron#gitops Pipe cron output to syslog Tag stdout+stderr into journald/syslog instead of mailing root */5 * * * * /opt/job.sh 2>&1 | /usr/bin/logger -t job #cron#observability#monitoring MAILTO and PATH header Cron PATH is minimal; set PATH/MAILTO at top or jobs fail silently crontab - <<'EOF' MAILTO=ops@example.com PATH=/usr/local/bin:/usr/bin:/bin 0 3 * * * backup.sh EOF #cron#troubleshooting#secrets Test run-parts dry run List which scripts would execute without running them; debugging cron.daily run-parts --test /etc/cron.daily #cron#debug#troubleshooting systemd timer alternative modern: transient OnCalendar timer with logs/retries; replaces a crontab line systemd-run --on-calendar='*-*-* 03:00:00' --unit=backup /opt/backup.sh #cron#gitops#observability One-shot job with at Schedule a single deferred command; inspect queue with atq, cancel with atrm at now + 1 hour <<< 'systemctl restart nginx' #cron#troubleshooting Defer until load is low Run only when load avg drops below 1.5; note: atd must be running batch <<< '/opt/heavy-reindex.sh' #cron#performance