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1 .TH CRONTABS 4 2012-08-29 "Marcela Mašláňová" "Crontabs users' Manual"
2 .SH NAME
3 crontabs \- configuration and scripts for running periodical jobs
4 .SH SYNOPSIS
5 .B run-parts
6 .RB [ --list | --test ] \fP\fI<directory>\fP
7 .br
8 .SH DESCRIPTION
9 Crontabs is a historical name for the run-parts script and the system
10 crontab. The run-parts script runs all executables in the specified
11 directory.
12 .B Run-parts
13 runs all executables in the specified directory.
14 The execution of files can be allowed or denied by creating file
15 .B jobs.allow
16 or
17 .B jobs.deny
18 which worked similar as other allow/deny config files. The file must be
19 created in the specified directory.
20 .TP
21 .B --list
22 print names of all files (not limited to executables), but don't run
23 them. This option can't be used with
24 .B test
25 option.
26 .TP
27 .B --test
28 print names of files, which would be run.
29
30 Randomization of jobs can be configured in the
31 .IR /etc/sysconfig/run-parts
32 file. To enable randomization of jobs, set the RANDOMIZE parameter to 1
33 and set the RANDOM parameter to an integer which determines a random
34 seed. Additionally, you may configure the RANDOMTIME parameter (again,
35 by specifying an integer) to provide an additional level of
36 randomization. Jobs are not randomized when the RANDOM and RANDOMTIME
37 parameters are set to 0. Values in these two parameters must be set to
38 1 or larger to provide a good enough randomization.
39
40 Randomization of cron jobs can be useful for shared networks, where
41 multiple cron jobs executed at once can cause spikes in traffic,
42 especially during daily jobs. With randomized jobs, the workload is
43 evenly distributed throughout the day.
44
45 .SH EXAMPLE OF CONFIGURATION FILE
46 .nf
47 RANDOMIZE=1
48 RANDOM=4
49 RANDOMTIME=8
50 .fi
51 .PP
52 Historically the crontab file contained configuration which called
53 .B run-parts
54 on files in
55 .I cron.{daily,weekly,monthly}
56 directories. These jobs are now run
57 indirectly through
58 .B anacron
59 to prevent conflicts between
60 .B cron
61 and
62 .B anacron.
63 That means the
64 .B anacron
65 package has to be installed if the jobs in these
66 directories should be running. Refer to the
67 .B anacron(8)
68 how to limit the time of day of the job execution.
69
70 .SH EXAMPLE
71 .I /etc/cron.daily/jobs.deny
72 could contain for example
73 .B 0logwatch
74 which forbid execution of this script.
75 .SH "SEE ALSO"
76 .B anacron(8), crontab(5)