title: How to run cron script alternately 30 minutes every minute
body: <p>I have two web servers namely web1 and web2. They are identical servers. Now, I have a php script that needs to run every 30 minutes. How can I run the php script in alternately every 30 minutes. Let say after 30 minutes from web1 server, the next 30 minutes will be run to web2 server.</p>
  
  <p>This is wrong.<br>
  <code>
  web1:
  */30 * * * * /usr/bin/php /path/to/site/cron.php
  <br>
  web2:
  */30 * * * * /usr/bin/php /path/to/site/cron.php
  </code></p>
  
  <p>Thanks. </p>