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

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).
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23       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.
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30       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.
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38       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.
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43       The temporary directory can be set in an environment variable.   If  it
44       is not set by the user, the /tmp directory is used.
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OPTIONS

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.
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53       -l     Displays the current crontab on standard output.
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55       -r     Removes the current crontab.
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57       -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.
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61       -i     This  option  modifies  the  -r  option to prompt the user for a
62              'y/Y' response before actually removing the crontab.
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64       -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).
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68       -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).
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83       -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.
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89       -V     Print version and exit.
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CAVEATS

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.
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98       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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SEE ALSO

103       crontab(5), cron(8)
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FILES

106       /etc/cron.allow
107       /etc/cron.deny
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STANDARDS

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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DIAGNOSTICS

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

121       Paul Vixie ⟨vixie@isc.org⟩
122       Colin Dean ⟨colin@colin-dean.org⟩
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126cronie                            2019-10-29                        CRONTAB(1)
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