crontabs(4) [centos man page]

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/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  RAN-
	      DOMTIME  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)

queuedefs(4)							   File Formats 						      queuedefs(4)

NAME

       queuedefs - queue description file for at, batch, and cron

SYNOPSIS

       /etc/cron.d/queuedefs

DESCRIPTION

       The queuedefs file describes the characteristics of the queues managed by cron(1M). Each non-comment line in this file describes one queue.
       The format of the lines are as follows:

	      q.[njobj][nicen][nwaitw]

       The fields in this line are:

       q	The name of the queue. a is the default queue for jobs started by at(1); b is the default queue for jobs  started  by  batch  (see
		at(1)); c is the default queue for jobs run from a crontab(1) file.

       njob	The  maximum  number of jobs that can be run simultaneously in that queue; if more than njob jobs are ready to run, only the first
		njob jobs will be run, and the others will be run as jobs that are currently running terminate.  The default value is  100.

       nice	The nice(1) value to give to all jobs in that queue that are not run with a user ID of super-user.  The default value is 2.

       nwait	The number of seconds to wait before rescheduling a job that was deferred because more than njob jobs were running in  that  job's
		queue, or because the system-wide limit of jobs executing has been reached.  The default value is 60.

       Lines beginning with # are comments, and are ignored.

EXAMPLES

       Example 1: A sample file.

       #
       #
       a.4j1n
       b.2j2n90w

       This  file  specifies that the a queue, for at jobs, can have up to 4 jobs running simultaneously; those jobs will be run with a nice value
       of 1.  As no nwait value was given, if a job cannot be run because too many other jobs are running cron will wait 60 seconds before  trying
       again to run it.

       The  b  queue, for batch(1) jobs, can have up to 2 jobs running simultaneously; those jobs will be run with a nice(1) value of 2.  If a job
       cannot be run because too many other jobs are running, cron(1M) will wait 90 seconds before trying again to run it. All	other  queues  can
       have up to 100 jobs running simultaneously; they will be run with a nice value of 2, and if a job cannot be run because too many other jobs
       are running cron will wait 60 seconds before trying again to run it.

FILES

       /etc/cron.d/queuedefs	       queue description file for  at, batch, and  cron.

SEE ALSO

       at(1), crontab(1), nice(1), cron(1M)

SunOS 5.10							    1 Mar 1994							      queuedefs(4)