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I have a question, magento uses a cron own or uses the cron of the same operating system?

And how could I configure it to make a cron of a specific module? In my case I want to export every "x" time the products of my store to make feeds with the module "Product Feed Export Module"

Operating system's crontab executes magento system cron and then magento system cron executes all the crons exist in magento modules which includes custom modules too.

It works like this:

1.) In operating system crontab you need to setup magento crons like this:

#~ MAGENTO START
* * * * * /usr/bin/php /var/www/html/magento2/bin/magento cron:run | 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
#~ MAGENTO END

2.) First cron command cron:run, it collects the crons from crontab.xml file of all modules and creates the entries into the database table 'cron_schedule' with the time when each cron needs to be executed.

3.) Now as the cron:run is executing repeatedly next time when it will run it will check the cron_schedule table and execute the crons which have same scheduled_time as the current time. Also this cron will schedule the crons to be executed into the cron_schedule table.

To setup/create cron for custom module.

1.) Create crontab.xml inside module's etc folder

<?xml version="1.0" ?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Cron:etc/crontab.xsd">
 <group id="default">
 <job instance="NamespaceModulenameCronExport" method="execute" name="namespace_modulename_export">
 <schedule>*/5 * * * *</schedule>
 </job>
 </group>
</config>

2.) Create your cron file inside module's Cron folder

<?php

namespace NamespaceModulenameCron;

class Export

 /**
 * Execute the cron
 *
 * @return void
 */

 public function execute()
 
 // write your cron code 
 

Magento2 is using the cron of the same operating system that mean you have to configure it.
Magento2 support a command that auto create system crontab:

php bin/Magento cron:install [--force]

After run above command, you can see system cron by this command:

crontab -l

A sample follows:

#~ MAGENTO START
* * * * * /usr/bin/php /var/www/html/magento2/bin/magento cron:run | 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
#~ MAGENTO END

Check more detail here

Create crontab.xml under:

app/code/Vendor/Module/etc/crontab.xml

with below contents:

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Cron:etc/crontab.xsd">
 <group id="default">
 <job name="export_products" instance="VendorModuleCronRun" method="execute">
 <schedule>*/5 * * * *</schedule>-->
 </job>
 </group>
</config>

Create Run.php under:

app/code/Vendor/Module/Cron/Run.php

with below contents:

<?php
namespace VendorModuleCron;

class Run 

 protected $_logger;
 public function __construct(
 PsrLogLoggerInterface $logger
 ) 
 
 $this->_logger = $logger;
 

 public function execute()
 
 // Write your export logic here
 $this->_logger->debug('Cron run successfully');
 return $this;
 

Above method only add this to magento 2 cron schedule. Above configuration show that the cron will execute at every 5 mins. You can change the time according to your requirement.

@Lee already mentioned how you need to set cron for magento 2.

Note: Above cron will run only when your magento 2 cron is enabled and running correctly.