title: Magento: Setup cronjob every 2 hours
body: <p>For some reason this code in module's config.xml:</p>
  
  <pre><code>&lt;jobs&gt;
      &lt;stockupdate&gt;
         &lt;schedule&gt;&lt;cron_expr&gt;0 */2 * * *&lt;/cron_expr&gt;&lt;/schedule&gt;
          &lt;run&gt;&lt;model&gt;stockupdate/cron::start&lt;/model&gt;&lt;/run&gt;
      &lt;/stockupdate&gt;
  &lt;/jobs&gt;
  </code></pre>
  
  <p>doesn't work. Although after changing <code>*/2</code> to <code>*</code> all seems to be alright.</p>
  
  <p>To test it I first do a <code>TRUNCATE cron_schedule</code>, then clean the cache <code>rm -rf var/cache</code> then run <code>php cron.php</code> and then <code>SELECT * FROM cron_schedule</code> to see if job was scheduled.</p>
  
  <p>I know there is also the nasty way <code>0 0,2,4,6,8,10,12,14,16,18,20,22 0 0 0</code> but this is a very inelegant solution.</p>
  
  <p>So how I can tell Magento to run this task every 2 hours?</p>