CRONTABS(4) Crontabs users' Manual CRONTABS(4)
NAME
crontabs - configuration and scripts for running periodical jobs
SYNOPSIS
run-parts [--list|--test]<directory>
DESCRIPTION
Crontabs is a historical name for the run-parts script and the system
crontab. The run-parts script runs all executables in the specified
directory. Run-parts runs all executables in the specified directory.
The execution of files can be allowed or denied by creating file
jobs.allow or jobs.deny which worked similar as other allow/deny config
files. The file must be created in the specified directory.
--list print names of all files (not limited to executables), but don't
run them. This option can't be used with test option.
--test print names of files, which would be run.
Randomization of jobs can be configured in the /etc/syscon-
fig/run-parts file. To enable randomization of jobs, set the
RANDOMIZE parameter to 1 and set the RANDOM parameter to an
integer which determines a random seed. Additionally, you may
configure the RANDOMTIME parameter (again, by specifying an
integer) to provide an additional level of randomization. Jobs
are not randomized when the RANDOM and RANDOMTIME parameters are
set to 0. Values in these two parameters must be set to 1 or
larger to provide a good enough randomization.
Randomization of cron jobs can be useful for shared networks,
where multiple cron jobs executed at once can cause spikes in
traffic, especially during daily jobs. With randomized jobs, the
workload is evenly distributed throughout the day.
EXAMPLE OF CONFIGURATION FILE
RANDOMIZE=1
RANDOM=4
RANDOMTIME=8
Historically the crontab file contained configuration which called run-
parts on files in cron.{daily,weekly,monthly} directories. These jobs
are now run indirectly through anacron to prevent conflicts between
cron and anacron. That means the anacron package has to be installed
if the jobs in these directories should be running. Refer to the
anacron(8) how to limit the time of day of the job execution.
EXAMPLE
/etc/cron.daily/jobs.deny could contain for example 0logwatch which
forbid execution of this script.
SEE ALSO
anacron(8), crontab(5)
Marcela Malaova 2012-08-29 CRONTABS(4)