1CRONTAB(1) User Commands CRONTAB(1)
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6 crontab - maintains crontab files for individual users
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9 crontab [-u user] file
10 crontab [-u user] [-l | -r | -e] [-i] [-s]
11 crontab -n [ hostname ]
12 crontab -c
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15 Crontab is the program used to install a crontab table file, remove or
16 list the existing tables used to serve the cron(8) daemon. Each user
17 can have their own crontab, and though these are files in /var/spool/,
18 they are not intended to be edited directly. For SELinux in MLS mode,
19 you can define more crontabs for each range. For more information, see
20 selinux(8).
21 In this version of Cron it is possible to use a network-mounted shared
23 /var/spool/cron across a cluster of hosts and specify that only one of
24 the hosts should run the crontab jobs in the particular directory at
25 any one time. You may also use crontab(1) from any of these hosts to
26 edit the same shared set of crontab files, and to set and query which
27 host should run the crontab jobs.
28 Running cron jobs can be allowed or disallowed for different users.
30 For this purpose, use the cron.allow and cron.deny files. If the
31 cron.allow file exists, a user must be listed in it to be allowed to
32 use cron If the cron.allow file does not exist but the cron.deny file
33 does exist, then a user must not be listed in the cron.deny file in
34 order to use cron. If neither of these files exists, only the super
35 user is allowed to use cron. Another way to restrict access to cron is
36 to use PAM authentication in /etc/security/access.conf to set up users,
37 which are allowed or disallowed to use crontab or modify system cron
38 jobs in the /etc/cron.d/ directory.
39 The temporary directory can be set in an environment variable. If it
41 is not set by the user, the /tmp directory is used.
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44 -u Appends the name of the user whose crontab is to be modified.
45 If this option is not used, crontab examines "your" crontab,
46 i.e., the crontab of the person executing the command. Note
47 that su(8) may confuse crontab, thus, when executing commands
48 under su(8) you should always use the -u option. If no crontab
49 exists for a particular user, it is created for him the first
50 time the crontab -u command is used under his username.
51 -l Displays the current crontab on standard output.
53 -r Removes the current crontab.
55 -e Edits the current crontab using the editor specified by the VIS‐
57 UAL or EDITOR environment variables. After you exit from the
58 editor, the modified crontab will be installed automatically.
59 -i This option modifies the -r option to prompt the user for a
61 'y/Y' response before actually removing the crontab.
62 -s Appends the current SELinux security context string as an
64 MLS_LEVEL setting to the crontab file before editing / replace‐
65 ment occurs - see the documentation of MLS_LEVEL in crontab(5).
66 -n This option is relevant only if cron(8) was started with the -c
68 option, to enable clustering support. It is used to set the
69 host in the cluster which should run the jobs specified in the
70 crontab files in the /var/spool/cron directory. If a hostname
71 is supplied, the host whose hostname returned by gethostname(2)
72 matches the supplied hostname, will be selected to run the
73 selected cron jobs subsequently. If there is no host in the
74 cluster matching the supplied hostname, or you explicitly spec‐
75 ify an empty hostname, then the selected jobs will not be run at
76 all. If the hostname is omitted, the name of the local host
77 returned by gethostname(2) is used. Using this option has no
78 effect on the /etc/crontab file and the files in the /etc/cron.d
79 directory, which are always run, and considered host-specific.
80 For more information on clustering support, see cron(8).
81 -c This option is only relevant if cron(8) was started with the -c
83 option, to enable clustering support. It is used to query which
84 host in the cluster is currently set to run the jobs specified
85 in the crontab files in the directory /var/spool/cron , as set
86 using the -n option.
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89 crontab(5), cron(8)
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92 /etc/cron.allow
93 /etc/cron.deny
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96 The crontab command conforms to IEEE Std1003.2-1992 (``POSIX''). This
97 new command syntax differs from previous versions of Vixie Cron, as
98 well as from the classic SVR3 syntax.
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101 An informative usage message appears if you run a crontab with a faulty
102 command defined in it.
103
105 Paul Vixie ⟨vixie@isc.org⟩
106 Colin Dean ⟨colin@colin-dean.org⟩
107cronie 2012-11-22 CRONTAB(1)