Replacing crontab with systemd timers

As of systemd version 212, you can use timers to schedule regular jobs. Systemd timers offer more functionality compared to crontab. See systemd.time for more details.

This post will show how to create timer job for ownclouds' cron.php job.

Basically, you need to create 2 files:

• systemd .service file
• systemd .timer file

Place these files in /etc/systemd/system.

cron-owncloud@http.service:
-this file will execute specified command. Notice the @http which ensures that the command will be executed with user http.

cat /etc/systemd/system/cron-owncloud\@http.service 

[Unit]
Description=owncloud cron job
Wants=cron-owncloud.timer

[Service]
User=%I      # comment this line if you want to run as root
Type=oneshot
Nice=19
IOSchedulingClass=2
IOSchedulingPriority=7
ExecStart=/usr/bin/php -f /srv/http/owncloud/cron.php 1>/dev/null

[Install]
WantedBy=basic.target

cron-owncloud.timer:
-this file will trigger .service file at specified time (OnCalendar). In this case, the service will be trigged each 5 minutes, in 20th second.

cat /etc/systemd/system/cron-owncloud.timer

[Unit]
Description=owncloud cron.php job

[Timer]
# To add a time of your choosing here, please refer to systemd.time manual page for the correct format
OnCalendar=*-*-* *:0/5:20
Persistent=true
Unit=cron-owncloud@http.service

[Install]
WantedBy=basic.target

Now you can enable and start this timer:

systemctl daemon-reload
systemctl enable cron-owncloud.timer
systemctl start cron-owncloud.timer