The command line to execute Magento 2 cron jobs is:
php <path to magento root>/bin/magento cron:run
To get it executed automatically you need add it to /etc/crontab, for example:
*/1 * * * * www-data php <path to magento root>/bin/magento cron:run
*/1 * * * * www-data php <path to magento root>/update/cron.php
*/1 * * * * www-data php <path to magento root>/bin/magento setup:cron:run