Cron submission of tasks | cron important configure files and directory

/var/spool/corn/username file it contain each user regulates his distinguished file and this is used in the UNIX system five
/etc/crontab file. These file it is accessible only by the root. crontab file from BSD Unix and it is derivatives.
/etc/cron.d directory. It is similar to crontab file. Only root user has permission to access the files.
/etc/cron.hourly
/etc/cron.daily
/etc/cron.weekly
/etc/cron.monthly these are the directory all these files are shell script which run time indicated in /etc/crontab file. Only root use has permission to access the files.

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