Linux · Job Scheduling (cron & timers)

In a .timer [Timer] section, what's the difference between OnBootSec, OnActiveSec, OnUnitActiveSec and OnUnitInactiveSec — and what unit applies to a bare number like 30?

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More in Job Scheduling (cron & timers)

Your machine unexpectedly starts hitting the disk and sending mail every 60 seconds. What about the cron daemon's design explains this once-a-minute rhythm?

In what order do the seven fields of a line in /etc/crontab appear, and what do an asterisk and the notation slash-n each do to a time field?

Which weekday number schedules a cron job for Sunday, and what surprising thing do the values 0 and 7 have in common?

You add a job as the last line of /etc/crontab but it never runs, even though the syntax looks perfect. What formatting rule is the usual culprit?

You drop a script into /etc/cron.daily but nothing happens on the next run. What one-line permission fix is almost always missing, and what privileges do these scripts run with?

When you edit your personal cron jobs with crontab -e instead of touching /etc/crontab, how does the field layout of your entries differ?

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