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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | CAVEATS | SEE ALSO | FILES | STANDARDS | DIAGNOSTICS | AUTHOR | COLOPHON |
CRONTAB(1) User Commands CRONTAB(1)
crontab - maintains crontab files for individual users
crontab [-u user] <file | ->
crontab [-T] <file | ->
crontab [-u user] <-l | -r | -e> [-i] [-s]
crontab -n [ hostname ]
crontab -c
crontab -V
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.
-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
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.
-V Print version and exit.
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
non-existent.
crontab(5), cron(8)
/etc/cron.allow
/etc/cron.deny
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.
An informative usage message appears if you run a crontab with a
faulty command defined in it.
Paul Vixie ⟨vixie@isc.org⟩
Colin Dean ⟨colin@colin-dean.org⟩
This page is part of the cronie (crond daemon) project. Information
about the project can be found at
⟨https://github.com/cronie-crond/cronie⟩. If you have a bug report
for this manual page, see
⟨https://github.com/cronie-crond/cronie/issues⟩. This page was
obtained from the project's upstream Git repository
⟨https://github.com/cronie-crond/cronie.git⟩ on 2020-08-13. (At that
time, the date of the most recent commit that was found in the repos‐
itory was 2020-08-03.) 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 to man-pages@man7.org
cronie 2019-10-29 CRONTAB(1)
Pages that refer to this page: cronnext(1) , pmsnap(1) , anacrontab(5) , crontab(5) , cron(8) , crond(8)