x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
CRONTAB(1) User Commands CRONTAB(1)
NAME
crontab - maintains crontab files for individual users
SYNOPSIS
crontab [-u user] <file | ->
crontab [-T] <file | ->
crontab [-u user] <-l | -r | -e> [-i] [-s]
crontab -n [ hostname ]
crontab -c
crontab -V
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 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 dif-
ferent 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 ex-
ist, 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.
When listing a crontab on a terminal the output will be colorized un-
less an environment variable NO_COLOR is set.
OPTIONS
-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 is-
sue 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 VIS-
UAL 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 / replace-
ment 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 se-
lected cron jobs subsequently. If there is no host in the clus-
ter 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 direc-
tory, 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
The files cron.allow and cron.deny cannot be used to restrict the exe-
cution of cron jobs; they only restrict the use of crontab. In partic-
ular, 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 invok-
ing crontab. If this is not the case, then they are treated as non-ex-
istent.
SEE ALSO
crontab(5), cron(8)
FILES
/etc/cron.allow
/etc/cron.deny
STANDARDS
The crontab command conforms to IEEE Std1003.2-1992 (``POSIX'') with
one exception: For replacing the current crontab with data from stan-
dard input the - has to be specified on the command line if the stan-
dard input is a TTY. 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 2019-10-29 CRONTAB(1)
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