1CRONTABS(4) Crontabs users' Manual CRONTABS(4)
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6 crontabs - configuration and scripts for running periodical jobs
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9 run-parts [--list|--test]<directory>
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12 Crontabs is a historical name for the run-parts script and the system
13 crontab. The run-parts command runs all executables in the specified
14 directory. The execution of files can be allowed or denied by creating
15 file jobs.allow or jobs.deny which worked similar as other allow/deny
16 config files. The file must be created in the specified directory.
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18 --list print names of all files (not limited to executables), but don't
19 run them. This option can't be used with test option.
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21 --test print names of files, which would be run.
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23 Randomization of jobs can be configured in the /etc/syscon‐
24 fig/run-parts file. To enable randomization of jobs, set the
25 RANDOMIZE parameter to 1 and set the RANDOM parameter to an
26 integer which determines a random seed. Additionally, you may
27 configure the RANDOMTIME parameter (again, by specifying an
28 integer) to provide an additional level of randomization. Jobs
29 are not randomized when the RANDOM and RANDOMTIME parameters are
30 set to 0. Values in these two parameters must be set to 1 or
31 larger to provide a good enough randomization.
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33 Randomization of cron jobs can be useful for shared networks,
34 where multiple cron jobs executed at once can cause spikes in
35 traffic, especially during daily jobs. With randomized jobs, the
36 workload is evenly distributed throughout the day.
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40 RANDOMIZE=1
41 RANDOM=4
42 RANDOMTIME=8
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44 Historically the crontab file contained configuration which called run-
45 parts on files in cron.{daily,weekly,monthly} directories. These jobs
46 are now run indirectly through anacron to prevent conflicts between
47 cron and anacron. That means the anacron package has to be installed
48 if the jobs in these directories should be running. Refer to the
49 anacron(8) how to limit the time of day of the job execution.
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53 /etc/cron.daily/jobs.deny could contain for example 0logwatch which
54 forbid execution of this script.
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57 anacron(8), crontab(5)
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61Marcela Mašláňová 2012-08-29 CRONTABS(4)