NAME

       systemd.cron - systemd cron units

SYNOPSIS

       cron.target, cron-hourly.timer, cron-hourly.target, cron-hourly.service, cron-daily.timer,
       cron-daily.target,  cron-daily.service,   cron-weekly.timer,   cron-weekly.target,   cron-
       weekly.service,   cron-monthly.timer,   cron-monthly.target,  cron-monthly.service,  cron-
       yearly.timer,    cron-yearly.target,    cron-yearly.service,    cron-update.path,    cron-
       update.service.

DESCRIPTION

       These units provide cron daemon functionality by running scripts in cron directories.
       The  crontabs  are  monitored  by  cron-update.path  and  are  automatically translated by
       systemd-crontab-generator(8) .

FILES

       /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.

       /etc/cron.d
              Directory for crontabs to be executed on a custom  schedule.   The  files  in  this
              folder must follow the crontab(5) layout.
              If  there  exists  a  timer  of  the same name + '.timer' in /lib/systemd/system or
              /etc/systemd/system, this crontab will be ignored to enable a smooth  migration  to
              native timers.
              You can also use this to mask an unneeded crontab provide by a package:
              ln -s /dev/null /etc/systemd/system/[package].timer

SYSTEM UNITS

       cron.target
              The  target unit which starts the others. This should be enabled and started to use
              cron functionality.

       cron-schedule.timer
              The timer units which pull the cron-schedule.target units at the appropriate  time.
              Started  and  stopped  by  the  cron.target  unit. These units cannot be controlled
              manually.

       cron-schedule.target
              The  targets  invoke  all  service  units   wanted   by   them,   including   cron-
              schedule.service.

       cron-schedule.service
              The service units which run scripts in the cron directories. Started and stopped by
              the cron-schedule.target units. These units cannot be controlled manually. You  can
              use journalctl(1) to view the output of scripts run from these units.

LIMITATIONS

       This  cron  replacement  only  send  mails on failure. The log of jobs is saved in systemd
       journal.  Do not use with a cron daemon or anacron,  otherwise  scripts  may  be  executed
       multiple times.
       All  services  are run with Type=oneshot , that means you can't use systemd-cron to launch
       long lived forking daemons.

EXTENSIONS

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

EXAMPLES

       Start cron units
              # systemctl start cron.target

       Start cron units on boot
              # systemctl enable cron.target

       View script output
              # journalctl -u cron-hourly
              # journalctl -u cron-daily
              # journalctl -u cron-weekly
              # journalctl -u cron-monthly
              # journalctl -u cron-yearly

       Override some generated timer start time
              # systemctl edit cron-geoip-database-contrib-root-<...>.timer --full
              keep existing statements, but change this one:
              [Timer]
              OnCalendar=*-*-* 18:36:00

       Override cron-daily.service priority, useful for old computers
              # systemctl edit cron-daily.service
              this will open a blank editor when you can type a drop-in configuration  file  that
              will extend the current .service
              [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

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

       2. run-parts(8) is used to run scripts. Scripts must be executable by root to run.

DIAGNOSTICS

       With systemd >= 209, you can execute "systemctl list-timers" to have a overview of  timers
       and know when they will elapse.

SEE ALSO

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

AUTHOR

       Dwayne Bent