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
13 crontab -V
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16 Crontab is the program used to install a crontab table file, remove or
17 list the existing tables used to serve the cron(8) daemon. Each user
18 can have their own crontab, and though these are files in /var/spool/,
19 they are not intended to be edited directly. For SELinux in MLS mode,
20 you can define more crontabs for each range. For more information, see
21 selinux(8).
22 In this version of Cron it is possible to use a network-mounted shared
24 /var/spool/cron across a cluster of hosts and specify that only one of
25 the hosts should run the crontab jobs in the particular directory at
26 any one time. You may also use crontab from any of these hosts to edit
27 the same shared set of crontab files, and to set and query which host
28 should run the crontab jobs.
29 Scheduling cron jobs with crontab can be allowed or disallowed for dif‐
31 ferent users. For this purpose, use the cron.allow and cron.deny
32 files. If the cron.allow file exists, a user must be listed in it to
33 be allowed to use crontab. If the cron.allow file does not exist but
34 the cron.deny file does exist, then a user must not be listed in the
35 cron.deny file in order to use crontab. If neither of these files
36 exist, then only the super user is allowed to use crontab.
37 Another way to restrict the scheduling of cron jobs beyond crontab is
39 to use PAM authentication in /etc/security/access.conf to set up users,
40 which are allowed or disallowed to use crontab or modify system cron
41 jobs in the /etc/cron.d/ directory.
42 The temporary directory can be set in an environment variable. If it
44 is not set by the user, the /tmp directory is used.
45
47 -u Specifies the name of the user whose crontab is to be modified.
48 If this option is not used, crontab examines "your" crontab,
49 i.e., the crontab of the person executing the command. If no
50 crontab exists for a particular user, it is created for them the
51 first time the crontab -u command is used under their username.
52 -l Displays the current crontab on standard output.
54 -r Removes the current crontab.
56 -e Edits the current crontab using the editor specified by the VIS‐
58 UAL or EDITOR environment variables. After you exit from the
59 editor, the modified crontab will be installed automatically.
60 -i This option modifies the -r option to prompt the user for a
62 'y/Y' response before actually removing the crontab.
63 -s Appends the current SELinux security context string as an
65 MLS_LEVEL setting to the crontab file before editing / replace‐
66 ment occurs - see the documentation of MLS_LEVEL in crontab(5).
67 -n This option is relevant only if cron(8) was started with the -c
69 option, to enable clustering support. It is used to set the
70 host in the cluster which should run the jobs specified in the
71 crontab files in the /var/spool/cron directory. If a hostname
72 is supplied, the host whose hostname returned by gethostname(2)
73 matches the supplied hostname, will be selected to run the
74 selected cron jobs subsequently. If there is no host in the
75 cluster matching the supplied hostname, or you explicitly spec‐
76 ify an empty hostname, then the selected jobs will not be run at
77 all. If the hostname is omitted, the name of the local host
78 returned by gethostname(2) is used. Using this option has no
79 effect on the /etc/crontab file and the files in the /etc/cron.d
80 directory, which are always run, and considered host-specific.
81 For more information on clustering support, see cron(8).
82 -c This option is only relevant if cron(8) was started with the -c
84 option, to enable clustering support. It is used to query which
85 host in the cluster is currently set to run the jobs specified
86 in the crontab files in the directory /var/spool/cron , as set
87 using the -n option.
88 -V Print version and exit.
90
92 The files cron.allow and cron.deny cannot be used to restrict the exe‐
93 cution of cron jobs; they only restrict the use of crontab. In partic‐
94 ular, restricting access to crontab has no effect on an existing
95 crontab of a user. Its jobs will continue to be executed until the
96 crontab is removed.
97 The files cron.allow and cron.deny must be readable by the user invok‐
99 ing crontab. If this is not the case, then they are treated as non-
100 existent.
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103 crontab(5), cron(8)
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106 /etc/cron.allow
107 /etc/cron.deny
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110 The crontab command conforms to IEEE Std1003.2-1992 (``POSIX'') with
111 one exception: For replacing the current crontab with data from stan‐
112 dard input the - has to be specified on the command line. This new
113 command syntax differs from previous versions of Vixie Cron, as well as
114 from the classic SVR3 syntax.
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117 An informative usage message appears if you run a crontab with a faulty
118 command defined in it.
119
121 Paul Vixie ⟨vixie@isc.org⟩
122 Colin Dean ⟨colin@colin-dean.org⟩
123cronie 2019-10-29 CRONTAB(1)