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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 command 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)