Cron job failures often go undetected because monitoring misses silent non-events

A common system outage occurs when scheduled cron jobs fail to run at all, rather than fail during execution. Standard monitoring that only checks for process exit codes cannot detect this, as no error is generated if the job never starts. The article lists numerous silent causes, such as cron being disabled after a reboot or a full disk preventing script execution. It recommends implementing a 'dead man's switch,' where jobs proactively signal their start and completion to an external monitor to detect their absence.