NAME

       systemd.cron - systemd cron units

SYNOPSIS

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

       /usr/lib/systemd/system/<schedule>.timer

       /etc/systemd/system/<schedule>.timer
              These native systemd timers will overide the legacy cron jobs.
              You can also use this mechanism to mask an unneeded crontab provide by a package:
              ln -s /dev/null /etc/systemd/system/[package].timer

       /var/spool/cron/crontabs
              User's crontabs, to be modifier using the crontab(1) utility.

SYSTEM UNITS

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

       cron-update.path
              This monitor  alteration  of  the  FILES  listed  hereupper  and  will  call  cron-
              update.service

       cron-update.service
              This  trigger a 'systemctl daemon-reload', the only way to ask systemd to rerun the
              generator.

       cron-failure@.service
              This service will send an email in case of failure.

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, which 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-<schedule>

       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.

DIAGNOSTICS

       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.timer(5),   systemd.time(7),
       systemd-crontab-generator(8), crontab(1), crontab(5)

AUTHOR

       Dwayne Bent