Drupal comes with system-wide defaults but the setting-module provides control over many Drupal preferences, behaviours including visual and operational settings.
Some modules require regularly scheduled actions, such as cleaning up logfiles. Cron, which stands for chronograph, is a periodic command scheduler executing commands at intervals specified in seconds. It can be used to control the execution of daily, weekly and monthly jobs (or anything with a period measured in seconds). Automating tasks is one of the best ways to keep a system running smoothly, and if most of your administration does not require your direct involvement, cron is an ideal solution.
-Whenever %cron-link is accessed, cron will run: it calls the _cron hook in each module allowing the module to run tasks if they have not been executed in the last n seconds, where n is the period of that task. When all the tasks are finished, cron is done.
The recommended way to set up your cron system is to set up a Unix/Linux crontab entry (see \"man crontab\") that frequently visits %cron-link. Note that cron does not guarantee the commands will be executed at the specified interval. However, Drupal will try its best to run the tasks as close to the specified intervals as possible. The more you visit cron.php, the more accurate cron will be.
If your hosting company does not allow you to set up crontab entries, you can always ask someone else to set up an entry for you. After all, virtually any Unix/Linux machine with access to the internet can set up a crontab entry to frequently visit %cron-link.
For the Unix/Linux crontab itself, use a browser like lynx or wget but make sure the process terminates: either use /usr/bin/lynx -source %base_url/cron.php or /usr/bin/wget -o /dev/null -O /dev/null %cron-link. Take a look at the example scripts in the scripts-directory. Make sure to adjust them to fit your needs. A good crontab line to run the cron script once every hour would be: