Tom Furie wrote: > On Fri, Apr 07, 2023 at 08:05:18AM +0800, k...@openmbox.net wrote: > > Are the time format in /etc/crontab just random? why they are 6:25, 6:47 > > etc? > > They aren't *random*, though they are somewhat arbitrary. The daily tasks > run at 6:25, a time chosen by someone somewhere back in the mists of time as > a time that the system is likely to be quiet. The daily tasks still run on > the days the weekly tasks are scheduled, so some time displacement is > factored in to give the daily job time to finish. Likewise with the monthly > allowing for both the daily and weekly.
It's also the case that if you have a dozen, hundred or ten thousand machines, you might not want them all doing the same thing at precisely the same time -- especially if it's disk, power or network intensive. So spreading out jobs is often a good idea. Automated deployment systems usually come with a way of randomizing the initial install of a cronjob. -dsr-