crontab - maintains crontab files for individual users
crontab -n [ hostname
is the program used to install a crontab table file
remove or list the existing tables used to serve the cron(8)
Each user can have their own crontab, and though these are files in
, 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
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
files. If the
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 temporary directory can be set in an environment variable. If it is not set
by the user, the /tmp
directory is used.
- 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
- Displays the current crontab on standard output.
- Removes the current crontab.
- 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.
- This option modifies the -r option to prompt the
user for a 'y/Y' response before actually removing the crontab.
- 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).
- 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
- 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.
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.
An informative usage message appears if you run a crontab with a faulty command
defined in it.