CRONTABS(4) - phpMan

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 executa-
bles in the specified directory. The execution of files can be allowed or denied by cre-
ating 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/sysconfig/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 con-
figure the RANDOMTIME parameter (again, by specifying an integer) to provide an
additional level of randomization. Jobs are not randomized when the RANDOM and RAN-
DOMTIME 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.