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crontab


SYNOPSIS

       crontab [-u user] file
       crontab [-u user] [-l | -r | -e] [-i] [-s]
       crontab -n [ hostname ]
       crontab -c


DESCRIPTION

       Crontab  is the program used to install a crontab table file, remove or
       list the existing tables used to serve the cron(8) daemon.   Each  user
       can  have their own crontab, and though these are files in /var/spool/,
       they are not intended to be edited directly.  For SELinux in MLS  mode,
       you can define more crontabs for each range.  For more information, see
       selinux(8).

       In this version of Cron it is possible to use a network-mounted  shared
       /var/spool/cron  across a cluster of hosts and specify that only one of
       the hosts should run the crontab jobs in the  particular  directory  at
       any  one  time.  You may also use crontab(1) from any of these hosts to
       edit the same shared set of crontab files, and to set and  query  which
       host should run the crontab jobs.

       Running  cron  jobs  can  be allowed or disallowed for different users.
       For this purpose, use the  cron.allow  and  cron.deny  files.   If  the
       cron.allow  file  exists,  a user must be listed in it to be allowed to
       use cron If the cron.allow file does not exist but the  cron.deny  file
       does  exist,  then  a  user must not be listed in the cron.deny file in
       order to use cron.  If neither of these files exists,  only  the  super
       user is allowed to use cron.  Another way to restrict access to cron is
       to use PAM authentication in /etc/security/access.conf to set up users,
       which  are  allowed  or disallowed to use crontab or modify system cron
       jobs in the /etc/cron.d/ directory.

       The temporary directory can be set in an environment variable.   If  it
       is not set by the user, the /tmp directory is used.


OPTIONS

       -u     Appends  the  name  of the user whose crontab is to be modified.
              If this option is not used,  crontab  examines  "your"  crontab,
              i.e.,  the  crontab  of  the person executing the command.  Note
              that su(8) may confuse crontab, thus,  when  executing  commands
              under  su(8) you should always use the -u option.  If no crontab
              exists for a particular user, it is created for  him  the  first
              time the crontab -u command is used under his username.

       -l     Displays the current crontab on standard output.

       -r     Removes the current crontab.

       -e     Edits the current crontab using the editor specified by the VIS-
              UAL or EDITOR environment variables.  After you  exit  from  the
              editor, the modified crontab will be installed automatically.

              cluster  matching the supplied hostname, or you explicitly spec-
              ify an empty hostname, then the selected jobs will not be run at
              all.   If  the  hostname  is omitted, the name of the local host
              returned by gethostname(2) is used.  Using this  option  has  no
              effect on the /etc/crontab file and the files in the /etc/cron.d
              directory, which are always run, and  considered  host-specific.
              For more information on clustering support, see cron(8).

       -c     This  option is only relevant if cron(8) was started with the -c
              option, to enable clustering support.  It is used to query which
              host  in  the cluster is currently set to run the jobs specified
              in the crontab files in the directory /var/spool/cron ,  as  set
              using the -n option.


SEE ALSO

       crontab(5), cron(8)


FILES

       /etc/cron.allow
       /etc/cron.deny


STANDARDS

       The  crontab command conforms to IEEE Std1003.2-1992 (``POSIX'').  This
       new command syntax differs from previous versions  of  Vixie  Cron,  as
       well as from the classic SVR3 syntax.


DIAGNOSTICS

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


AUTHOR

       Paul Vixie <vixie@isc.org>
       Colin Dean <colin@colin-dean.org>


cronie 2012-11-22 CRONTAB(1)



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