Setting up reminders is very simple. You simply have to run the reminders.php script in your /horde/kronolith/scripts/ directory on the shell. To do it manually, simply try this (replace /var/www/horde with the path to your Horde installation):
php /var/www/horde/kronolith/scripts/reminders.php
Note: Your php executable must be the CLI version, it will NOT work with the CGI version. Do php -v to verify that you have the CLI version.
If this works (you will get an email), you have to create a cronjob to call the reminders script regularly. In this example, it is called every five minutes. So edit your crontab:
crontab -e
and enter the following (replace /var/www/horde with the path to your Horde installation and /usr/bin/php with the path to your PHP CLI binary):
# Kronolith reminders */5 * * * * /usr/bin/php /var/www/horde/kronolith/scripts/reminders.php
Note that the user that runs the cron job needs to have write access to the Horde VFS as reminder state information is stored there. If you are using a filesystem based VFS driver, running as the web server user is a good alternative to running as root.
If you are editing a global system crontab instead of using the crontab -e command to edit a specific user's crontab, you may need to specify the user the job will run as or other information specific to your system and that global file.