1. Open terminal 
2. write a command crontab -e 
3. write below command

* * * * * /usr/bin/php /var/www/html/magento2/bin/magento cron:run 2>&1 | grep -v "Ran jobs by schedule" >> /var/www/html/magento2/var/log/magento.cron.log
* * * * * /usr/bin/php /var/www/html/magento2/update/cron.php >> /var/www/html/magento2/var/log/update.cron.log
* * * * * /usr/bin/php /var/www/html/magento2/bin/magento setup:cron:run >> /var/www/html/magento2/var/log/setup.cron.log

Note :- check your php and magento 2 folder path according your project.

1. Open terminal 
2. write a command crontab -e 
3. write below command

* * * * * /usr/bin/php /var/www/html/magento2/bin/magento cron:run 2>&1 | grep -v "Ran jobs by schedule" >> /var/www/html/magento2/var/log/magento.cron.log
* * * * * /usr/bin/php /var/www/html/magento2/update/cron.php >> /var/www/html/magento2/var/log/update.cron.log
* * * * * /usr/bin/php /var/www/html/magento2/bin/magento setup:cron:run >> /var/www/html/magento2/var/log/setup.cron.log

Note :- check your php and magento 2 folder path according to your project.