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crontab(1) — Linux manual page

CRONTAB(1)                    User CommandsCRONTAB(1)

NAME        top

       crontab - maintains crontab files for individual users

SYNOPSIS        top

crontab[-uuser] <file |->crontab[-T] <file |->crontab[-uuser] <-l|-r|-e> [-i] [-s]crontab -n[hostname ]crontab -ccrontab -V

DESCRIPTION        top

Crontab is the program used to install a crontab tablefile,       remove or list the existing tables used to serve thecron(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, seeselinux(8).       In this version ofCron 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 usecrontab       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 withcrontabcan be allowed or disallowed for       different users.  For this purpose, use thecron.allow andcron.deny files.  If thecron.allow file exists, a user must be       listed in it to be allowed to usecrontab.  If thecron.allow file       does not exist but thecron.deny file does exist, then a user mustnot be listed in thecron.deny file in order to usecrontab.If       neither of these files exist, then only the super user is allowed       to usecrontab.       Another way to restrict the scheduling of cron jobs beyondcrontab       is to use PAM authentication in/etc/security/access.conf to set       up users, which are allowed or disallowed to usecrontabor 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       unless an environment variableNO_COLOR is set.       On edition or deletion of the crontab, a backup of the last       crontab will be saved to$XDG_CACHE_HOME/crontab/crontab.bak or$XDG_CACHE_HOME/crontab/crontab.<user>.bak if-uis used.  If theXDG_CACHE_HOME environment variable is not set,$HOME/.cache will       be used instead.

OPTIONS        top

-uSpecifies the name of the user whose crontab is to be              modified.  If this option is not used,crontabexamines              "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 thecrontab -ucommand              is used under their username.-TTest 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.-lDisplays the current crontab on standard output.-rRemoves the current crontab.-eEdits the current crontab using the editor specified by theVISUAL orEDITOR environment variables.  After you exit              from the editor, the modified crontab will be installed              automatically.-iThis option modifies the-roption to prompt the user for a              'y/Y' response before actually removing the crontab.-sAppends 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 incrontab(5).-nThis option is relevant only ifcron(8) was started with              the-coption, 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 bygethostname(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 bygethostname(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,              seecron(8).-cThis option is only relevant ifcron(8) was started with              the-coption, 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-noption.-VPrint version and exit.

CAVEATS        top

       The filescron.allow andcron.deny cannot be used to restrict the       execution of cron jobs; they only restrict the use ofcrontab.  In       particular, restricting access tocrontabhas no effect on an       existingcrontab of a user. Its jobs will continue to be executed       until the crontab is removed.       The filescron.allow andcron.deny must be readable by the user       invokingcrontab.  If this is not the case, then they are treated       as non-existent.

SEE ALSO        top

crontab(5),cron(8)

FILES        top

       /etc/cron.allow       /etc/cron.deny

STANDARDS        top

       Thecrontab 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       if the standard input is a TTY.  This new command syntax differs       from previous versions of Vixie Cron, as well as from the classic       SVR3 syntax.

DIAGNOSTICS        top

       An informative usage message appears if you run a crontab with a       faulty command defined in it.

AUTHOR        top

       Paul Vixie ⟨vixie@isc.org⟩       Colin Dean ⟨colin@colin-dean.org⟩

COLOPHON        top

       This page is part of thecronie (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 2025-08-11.  (At       that time, the date of the most recent commit that was found in       the repository was 2025-07-31.)  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 isnot part of the original manual page), send a mail to       man-pages@man7.orgcronie                          2019-10-29CRONTAB(1)

Pages that refer to this page:cronnext(1), pmsnap(1), anacrontab(5), crontab(5), systemd.exec(5), cron(8)

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