:LinuxLookup.com: Crontab Scheduling Service Guide
LinuxLookup.com: Crontab Scheduling Service Guide Oct 1, 2000, 17 :52 UTC (0 Talkback[s]) (4666 reads) (Other stories by Vicky)
"Certain processes must be run at specific times, over and over again. An
example of this might be a backup process that is launched each night
as the rest of the world sleeps, or a log analyzer that must ran every
minute. These processes are ran at certain times or on certain days; the
rest of the time, they are not running because they require user
interaction (command) or "direction" for lack of a better term. This is
where cron comes in handy. It allows you to schedule a specific task to
be ran when ever you please, on the minute, hourly, daily, monthly and
thus giving you a sense of relief knowing tasks are being executed
without you having to baby-sit your system."
"Cron is started from either rc or rc.local and returns immediately, so there
is no need to background this command. Cron searches /etc/crontab for
system entries and also /var/spool/cron for entries that match users in
the /etc/passwd file; found entries are loaded into memory. This occurs
every minute as cron "wakes-up" and does several things:
1. It checks the entries that it knows about and runs any
commands that are scheduled to run.
2. It determines whether the modtime on the cron directory
has changed.
3. If the modtime on the cron directory has changed, cron
checks each of the files and reloads any that have
changed."
"Since cron checks for changes every minute, it is unnecessary to restart
cron when the cron files are changed (edited)."
