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). The aggregator module periodically updates feeds using cron. Ping periodically notifies services of new content on your site. Search periodically indexes the content on your site. 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. Cron can, if necessary, also be run manually.