https://www.drupal.org/docs/7/setting-up-cron/configuring-cron-jobs-using-the-cron-command
curl -s http://domain.com/cron.php?cron_key=xxx
or (if curl is not installed)
/usr/bin/wget -O - -q -t 1 http://www.example.com/cron.php
https://askubuntu.com/questions/56683/where-is-the-cron-crontab-log