crontab

CRONTAB(1)                       User Commands                      CRONTAB(1)



NAME
       crontab - maintains crontab files for individual users

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
              VISUAL or EDITOR environment variables.  After you exit from the
              editor, the modified crontab will be installed automatically.

       -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
              crontab(5).

       -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.

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)