Automated jobs.
WHAT CRON DOES
Runs commands on a schedule.
WHAT IT IS USED FOR
Application scheduled tasks Backups Maintenance Certificate renewal
WHICH USER RUNS IT
Matters. A job running as the wrong user may fail or create files with wrong ownership.
WHAT GOES WRONG
A job that fails silently A job running more often than intended Output filling the disk Jobs overlapping because one takes longer than the interval
THE SILENT FAILURE PROBLEM
Cron failures produce no visible symptom until something that depended on them is missing.
Log output and check it.
FOR APPLICATION TASKS
Many applications expect a scheduled task. WordPress is one.
Check yours is actually running.
FOR HEAVY JOBS
Schedule them outside busy periods.
WHAT TO DOCUMENT
What runs, when, as whom, and why.
