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)

systemd-cron 2.3.2-1build1                         2023-08-13                                    SYSTEMD.CRON(7)