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-
       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.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

       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