NAME

     systemd.crom — systemd units for cron periodic jobs

SYNOPSIS

     cron.target
     cron-update.path, cron-update.service
     cron-mail@.service

DESCRIPTION

     These units provide the functionality usually afforded by the cron daemon — running scripts
     in /etc/cron.schedule directories and sending mail on failure.

     Crontabs are monitored by cron-update.path and are automatically translated by
     systemd-crontab-generator(8).

FILES

     /etc/crontab              Administrator's system crontab, see crontab(5).
     /etc/cron.d               System crontabs managed by packages live here.
     /etc/anacrontab           anacrontab(5)
     /var/spool/cron/crontabs  Users' crontabs live here.

     /etc/cron.hourly          Directory for scripts to be executed every hour.
     /etc/cron.daily           Directory for scripts to be executed every day.
     /etc/cron.weekly          Directory for scripts to be executed every week.
     /etc/cron.monthly         Directory for scripts to be executed every month.
     /etc/cron.yearly          Directory for scripts to be executed every year.

     /usr/lib/systemd/system/schedule.timer
     /etc/systemd/system/schedule.timer
                               Native systemd timers will override cron jobs with the same name.

                               You can also use this mechanism to mask an unneeded crontab
                               provided by a package via systemctl mask package.timer.

UNITS

     cron.target              Target unit which starts the others, needs to be enabled to use
                              systemd-cron.
     cron-update.path         Monitors FILES and calls
     cron-update.service      which runs systemctl daemon-reload to re-run the generator.

     cron-mail@.service       Sends mail (via sendmail(1), which can be overridden with
                              $SENDMAIL) in case a cron service unit fails, succeeds, or
                              succeeds-but-only-if-it-wrote-something.  The instance name (the
                              bit after the @) is the unit name, followed by optional arguments
                              delimited by colons (‘:’):
                              nonempty    exit silently if the unit produced no output
                                          (equivalent to CRON_MAIL_SUCCESS=nonempty) for
                                          OnSuccess=),
                              nometadata  don't include systemctl status output, don't add usual
                                          journalctl metadata to the output (equivalent to
                                          CRON_MAIL_FORMAT=nometadata), and
                              verbose     log reason before exiting silently.
                              (upper-case arguments are ignored).

                              Overriding this via systemctl edit can be useful, especially for
                              units under /etc/cron.*.

BUGS

     Do not use with a cron daemon or anacron, otherwise scripts may be executed multiple times.

     All services are run with Type=oneshot, which means you can't use systemd-cron to launch
     long lived forking daemons.

EXTENSIONS

     The generator can optionally turn any crontabs in persistent timers with the PERSISTENT=true
     flag, while a regular cron and anacron setup won't catch up on the missed executions of
     crontabs on reboot.

EXAMPLES

   Start cron units
     # systemctl start cron.target

   Start cron units on boot
     # systemctl enable cron.target

   View script output
     # journalctl -u cron-daily

   Override some generated timer start time
         # systemctl edit cron-geoip-database-contrib-root-1.timer
     and add
         [Timer]
         OnCalendar=
         OnCalendar=*-*-* 18:36:00

   Override cron-daily.service priority, useful for old computers
         # systemctl edit cron-daily.service
     and add
         [Service]
         CPUSchedulingPolicy=idle
         IOSchedulingClass=idle

   Example service file executed every hour
     [Unit]
     Description=Update the man db

     [Service]
     Nice=19
     IOSchedulingClass=2
     IOSchedulingPriority=7
     ExecStart=/usr/bin/mandb --quiet

     [Install]
     WantedBy=cron-hourly.target

NOTES

     The exact times scripts are executed is determined by the values of the special calendar
     events hourly, daily, weekly, monthly, and yearly defined in systemd.time(7).

DIAGNOSTICS

     systemctl list-timers shows an overview of current timers and when they'll elapse.

SEE ALSO

     crontab(1), systemd(1), crontab(5), systemd.service(5), systemd.timer(5), systemd.unit(5),
     systemd.time(7), run-parts(8), systemd-crontab-generator(8)