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.
-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
-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.
This page is part of the cronie (crond daemon) project. Information
about the project can be found at ⟨https://fedorahosted.org/cronie/⟩.
If you have a bug report for this manual page, see
⟨https://fedorahosted.org/cronie/⟩. This page was obtained from the
project's upstream Git repository
⟨http://git.fedorahosted.org/git/cronie.git⟩ on 2016-10-04. If you
discover any rendering problems in this HTML version of the page, or
you believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail
cronie 2012-11-22 CRONTAB(1)