NAME

       systemd.cron — 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.
       /dev/shm/systemd-cron.*   Queues     and     tokens     used     for     CRON_BATCH_LOADAVG_BELOW     and
                                 CRON_BATCH_THROTTLE_GROUP.

       /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)

systemd-cron 2.6.0-1                               2025-09-06                                    SYSTEMD.CRON(7)