Magento has important system processes that are very important to maintain the system's working at its full potential. These processes need automated executions to handle the updates made by the user and administrator. That is the why this feature is critical to Magento.
Cron job works with UNIX systems and can schedule specific tasks to be executed in a predetermined time on the server. The following activities can be scheduled to execute on the Magento 2.0 system:
To configure the cron job, follow this recipe.
Find the php.ini file path.
If you use XAMPP, as was suggested for a web server solution at the beginning of the book, you simply can use the XAMPP/xamppfiles/etc/php.ini path. If you use a Unix-based terminal, you can use the command to find the PHP configuration file. Perform the following steps:
sudo crontab -u magento_user –e command; here, magento_user refers to your system's owner.*/1 * * * * php -c <php-ini-file-path> <your Magento install dir>/bin/magento cron:run */1 * * * * php -c <php-ini-file-path> <your Magento install dir>/update/cron.php */1 * * * * php -c <php-file-path> <your Magento install dir>/bin/magento setup:cron:run
Here's an example:
*/1 * * * * php -c /Applications/XAMPP/xamppfiles/etc/php.ini /Applications/XAMPP/xamppfiles/etc/php.ini /Applications/XAMPP/htdocs/packt/bin/magento cron:run */1 * * * * php -c /Applications/XAMPP/xamppfiles/etc/php.ini /Applications/XAMPP/xamppfiles/etc/php.ini /Applications/XAMPP/htdocs/packt/update/cron.php */1 * * * * php -c /Applications/XAMPP/xamppfiles/etc/php.ini /Applications/XAMPP/htdocs/packt/bin/magento setup:cron:run
sudo crontab -u fjmiguel –l command to take a look at your new cron job configuration.In some cases, it is necessary to give write permissions again to the directories.
The */1 * * * * configuration specifies that the cron job will be executed every minute. The cron job will now run in the background every minute. To manually execute the cron job, you can run the php magento cron:run command on the Magento command-line tool, as shown in the following figure:

For further information about the cron job, follow the link at https://help.ubuntu.com/community/CronHowto.
For Magento cron, take a look at the official Magento documentation http://devdocs.magento.com/guides/v2.0/config-guide/cli/config-cli-subcommands-cron.html.