“In any system, an important funciton is scheduling tasks to
be run. Users and administrators alike often pay hundreds of
dollars for Windows tools to run programs at specified times. In
Linux, there is a tool called ‘cron’ which will handle all of your
scheduling needs. Best of all, it’s free, and it comes with
Linux.“
“Cron is available with every Linux distribution. It has two
main programs, crond and crontab. crond is the daemon that runs in
the background and makes sure that programs get run when they’re
scheduled to be run. crontab is the program that allows you to
modify the programs that you have scheduled to run. /etc/crontab is
the file that stores sytem scheduling information; each user has
their own crontab file in /var/spool/cron….”
“You can create a crontab file without using crontab, but use
crontab to set the file to be your crontab file. Use the command
`crontab file`, where ‘file’ is the file you want to use. This will
replace your old crontab file, however, not append to it.”