1CRONTAB(1)                       User Commands                      CRONTAB(1)
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NAME

6       crontab - maintains crontab files for individual users
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SYNOPSIS

9       crontab [-u user] <file | ->
10       crontab [-T] <file | ->
11       crontab [-u user] <-l | -r | -e> [-i] [-s]
12       crontab -n [ hostname ]
13       crontab -c
14       crontab -V
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DESCRIPTION

17       Crontab  is the program used to install a crontab table file, remove or
18       list the existing tables used to serve the cron(8) daemon.   Each  user
19       can  have their own crontab, and though these are files in /var/spool/,
20       they are not intended to be edited directly.  For SELinux in MLS  mode,
21       you can define more crontabs for each range.  For more information, see
22       selinux(8).
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24       In this version of Cron it is possible to use a network-mounted  shared
25       /var/spool/cron  across a cluster of hosts and specify that only one of
26       the hosts should run the crontab jobs in the  particular  directory  at
27       any one time.  You may also use crontab from any of these hosts to edit
28       the same shared set of crontab files, and to set and query  which  host
29       should run the crontab jobs.
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31       Scheduling cron jobs with crontab can be allowed or disallowed for dif‐
32       ferent users.  For this  purpose,  use  the  cron.allow  and  cron.deny
33       files.   If  the cron.allow file exists, a user must be listed in it to
34       be allowed to use crontab.  If the cron.allow file does not  exist  but
35       the  cron.deny  file  does exist, then a user must not be listed in the
36       cron.deny file in order to use crontab.   If  neither  of  these  files
37       exist, then only the super user is allowed to use crontab.
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39       Another  way  to restrict the scheduling of cron jobs beyond crontab is
40       to use PAM authentication in /etc/security/access.conf to set up users,
41       which  are  allowed  or disallowed to use crontab or modify system cron
42       jobs in the /etc/cron.d/ directory.
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44       The temporary directory can be set in an environment variable.   If  it
45       is not set by the user, the /tmp directory is used.
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47       When  listing  a  crontab  on  a  terminal the output will be colorized
48       unless an environment variable NO_COLOR is set.
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OPTIONS

51       -u     Specifies the name of the user whose crontab is to be  modified.
52              If  this  option  is  not used, crontab examines "your" crontab,
53              i.e., the crontab of the person executing  the  command.  If  no
54              crontab exists for a particular user, it is created for them the
55              first time the crontab -u command is used under their username.
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57       -T     Test the crontab file syntax without  installing  it.   Once  an
58              issue  is found, the validation is interrupted, so this will not
59              return all the existing issues at the same execution.
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61       -l     Displays the current crontab on standard output.
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63       -r     Removes the current crontab.
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65       -e     Edits the current crontab using the editor specified by the VIS‐
66              UAL  or  EDITOR  environment variables.  After you exit from the
67              editor, the modified crontab will be installed automatically.
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69       -i     This option modifies the -r option to  prompt  the  user  for  a
70              'y/Y' response before actually removing the crontab.
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72       -s     Appends  the  current  SELinux  security  context  string  as an
73              MLS_LEVEL setting to the crontab file before editing /  replace‐
74              ment occurs - see the documentation of MLS_LEVEL in crontab(5).
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76       -n     This  option is relevant only if cron(8) was started with the -c
77              option, to enable clustering support.  It is  used  to  set  the
78              host  in  the cluster which should run the jobs specified in the
79              crontab files in the /var/spool/cron directory.  If  a  hostname
80              is  supplied, the host whose hostname returned by gethostname(2)
81              matches the supplied hostname,  will  be  selected  to  run  the
82              selected  cron  jobs  subsequently.   If there is no host in the
83              cluster matching the supplied hostname, or you explicitly  spec‐
84              ify an empty hostname, then the selected jobs will not be run at
85              all.  If the hostname is omitted, the name  of  the  local  host
86              returned  by  gethostname(2)  is used.  Using this option has no
87              effect on the /etc/crontab file and the files in the /etc/cron.d
88              directory,  which  are always run, and considered host-specific.
89              For more information on clustering support, see cron(8).
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91       -c     This option is only relevant if cron(8) was started with the  -c
92              option, to enable clustering support.  It is used to query which
93              host in the cluster is currently set to run the  jobs  specified
94              in  the  crontab files in the directory /var/spool/cron , as set
95              using the -n option.
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97       -V     Print version and exit.
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CAVEATS

100       The files cron.allow and cron.deny cannot be used to restrict the  exe‐
101       cution of cron jobs; they only restrict the use of crontab.  In partic‐
102       ular, restricting access to  crontab  has  no  effect  on  an  existing
103       crontab  of  a  user.  Its  jobs will continue to be executed until the
104       crontab is removed.
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106       The files cron.allow and cron.deny must be readable by the user  invok‐
107       ing  crontab.   If  this is not the case, then they are treated as non-
108       existent.
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SEE ALSO

111       crontab(5), cron(8)
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FILES

114       /etc/cron.allow
115       /etc/cron.deny
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STANDARDS

118       The crontab command conforms to IEEE  Std1003.2-1992  (``POSIX'')  with
119       one  exception:  For replacing the current crontab with data from stan‐
120       dard input the - has to be specified on the command line if  the  stan‐
121       dard  input  is  a  TTY.  This new command syntax differs from previous
122       versions of Vixie Cron, as well as from the classic SVR3 syntax.
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DIAGNOSTICS

125       An informative usage message appears if you run a crontab with a faulty
126       command defined in it.
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AUTHOR

129       Paul Vixie ⟨vixie@isc.org⟩
130       Colin Dean ⟨colin@colin-dean.org⟩
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134cronie                            2019-10-29                        CRONTAB(1)
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