crontab(1) — Linux manual page


CRONTAB(1)                      User Commands                     CRONTAB(1)

NAME         top

       crontab - maintains crontab files for individual users

SYNOPSIS         top

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

DESCRIPTION         top

       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 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.

       Scheduling cron jobs with crontab 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 crontab.  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 crontab.  If neither of these files
       exist, then only the super user is allowed to use crontab.

       Another way to restrict the scheduling of cron jobs beyond crontab 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         top

       -u     Specifies 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. If no crontab exists for a particular user, it is
              created for them the first time the crontab -u command is used
              under their username.

       -T     Test the crontab file syntax without installing it.  Once an
              issue is found, the validation is interrupted, so this will
              not return all the existing issues at the same execution.

       -l     Displays the current crontab on standard output.

       -r     Removes the current crontab.

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

       -i     This option modifies the -r option to prompt the user for a
              'y/Y' response before actually removing the crontab.

       -s     Appends the current SELinux security context string as an
              MLS_LEVEL setting to the crontab file before editing /
              replacement occurs - see the documentation of MLS_LEVEL in

       -n     This option is relevant only if cron(8) was started with the
              -c option, to enable clustering support.  It is used to set
              the host in the cluster which should run the jobs specified in
              the crontab files in the /var/spool/cron directory.  If a
              hostname is supplied, the host whose hostname returned by
              gethostname(2) matches the supplied hostname, will be selected
              to run the selected cron jobs subsequently.  If there is no
              host in the cluster matching the supplied hostname, or you
              explicitly specify 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.

       -V     Print version and exit.

CAVEATS         top

       The files cron.allow and cron.deny cannot be used to restrict the
       execution of cron jobs; they only restrict the use of crontab.  In
       particular, restricting access to crontab has no effect on an
       existing crontab of a user. Its jobs will continue to be executed
       until the crontab is removed.

       The files cron.allow and cron.deny must be readable by the user
       invoking crontab.  If this is not the case, then they are treated as

SEE ALSO         top

       crontab(5), cron(8)

FILES         top


STANDARDS         top

       The crontab command conforms to IEEE Std1003.2-1992 (``POSIX'') with
       one exception: For replacing the current crontab with data from
       standard input the - has to be specified on the command line.  This
       new command syntax differs from previous versions of Vixie Cron, as
       well as from the classic SVR3 syntax.

DIAGNOSTICS         top

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

AUTHOR         top

       Paul Vixie ⟨⟩
       Colin Dean ⟨⟩

COLOPHON         top

       This page is part of the cronie (crond daemon) project.  Information
       about the project can be found at 
       ⟨⟩.  If you have a bug report
       for this manual page, see
       ⟨⟩.  This page was
       obtained from the project's upstream Git repository
       ⟨⟩ on 2020-09-18.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2020-08-21.)  If you discover any rendering problems in
       this HTML version of the page, or you believe there is a better or
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       of the original manual page), send a mail to

cronie                           2019-10-29                       CRONTAB(1)

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