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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  exe‐
       cution  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/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 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 con‐
       flicts 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 Mašláňová                                     2012-08-29                                          CRONTABS(4)