The software described in this documentation is either in Extended Support or Sustaining Support. See https://www.oracle.com/us/support/library/enterprise-linux-support-policies-069172.pdf for more information.
Oracle recommends that you upgrade the software described by this documentation as soon as possible.
You can use automated tasks to perform periodic backups, monitor the system, run custom scripts, and other administrative tasks.
The cron
and anacron
utilities allow you to schedule the execution of recurring tasks
(jobs) according to a combination of the
time, day of the month, month, day of the week, and week.
cron
allows you to schedule jobs to run as
often as every minute. If the system is down when a job is
scheduled, cron
does not run the job when the
system restarts. anacron
allows you to schedule
a system job to run only once per day. However, if a scheduled job
has not been run, that job runs when the system restarts.
anacron
is mainly intended for use on laptop
computers.
You do not usually need to run cron
and
anacron
directly. The crond
daemon executes scheduled tasks on behalf of
cron
and it starts anacron
once every hour. crond
looks in
/etc/crontab
or in files in
/etc/cron.d
for system cron
job definitions, and /var/spool/cron
for
cron
job definitions belonging to users.
crond
checks each job definition to see whether
it should run in the current minute. If a job is scheduled for
execution, crond
runs it as the owner of the
job definition file or, for system cron
jobs,
the user specified in the job definition (if any).
crond
runs the 0anacron
script in the /etc/cron.hourly
directory as
root
once per hour according to the schedule in
/etc/cron.d/0hourly
. If
anacron
is not already running and the system
is connected to mains and not battery power,
crond
starts anacron
.
anacron
runs the scripts in the
/etc/cron.daily
,
/etc/cron.weekly
, and
/etc/cron.monthly
directories as
root
once per day, week or month, according to
the job definitions that are scheduled in
/etc/anacrontab
.