Silent cron failures: why your scheduled job may never have run at all

A common but overlooked failure mode occurs when scheduled cron jobs never execute rather than failing with an error, leaving no logs, no alerts, and no trace. Causes range from a masked crond after a reboot to full disks, unmounted filesystems, or a mistyped crontab line — all of which produce complete silence. Standard monitoring that alerts on non-zero exit codes cannot catch these cases, since no process ever starts to produce an exit code. The recommended fix is a dead man's switch pattern, where each job actively reports its start and completion to an external monitor, and the absence of that report within an expected window triggers the alert. Developers are advised to wrap jobs with start and completion pings, use shell traps to catch early exits, and ensure monitoring failures can never themselves prevent the underlying job from running.