If systemd is installed on the system, a systemd timer could be an alternative to a cronjob.
This approach requires two files: myappcron.service and myappcron.timer. Create these two files in /etc/systemd/system/.
myappcron.service should look like this:
[Unit] Description=myapp cron.php job [Service] User=www-data ExecStart=/usr/bin/php -f /var/www/myapp/cron.php [Install] WantedBy=basic.target
Replace the user www-data with the user of your http server and /var/www/myapp/cron.php with the location of cron.php in your nextcloud directory.
myappcron.timer should look like this:
[Unit] Description=Run myapp cron.php every 5 minutes [Timer] OnBootSec=5min OnUnitActiveSec=5min Unit=myappcron.service [Install] WantedBy=timers.target
The important parts in the timer-unit are OnBootSec and OnUnitActiveSec. OnBootSec will start the timer 5 minutes after boot, otherwise you would have to start it manually after every boot. OnUnitActiveSec will set a 5 minute timer after the service-unit was last activated.
Now all that is left is to start and enable the timer by running this command:
# systemctl enable --now myappcron.timer
When the option –now is used with enable, the resp. unit will also be started.