How to upgrade SugarCRM using the silent upgrader
The silent upgrade is performed via SSH. It's achieved by executing only one command.
Before you begin back up the SugarCRM files and the MySQL database used by the application.
First, you need to download the upgrade archive corresponding to your SugarCRM version from the official site. Then upload it to your SugarCRM hosting account; keep it zipped. Then connect to your account via SSH and execute the following command:
php -f (path to silentUpgrade.php) (path to upgrade archive) (path to log file) (path to your SugarCRM instance) (your admin name)
Replace (path to silentUpgrade.php) with the actual path to the file. Every installation has this file; in relation to the root SugarCRM directory the path is modules/UpgradeWizard/silentUpgrade.php. In the place of (path to upgrade archive) put the actual path to the upgrade archive that you uploaded to your hosting account. Replace (path to log file) with a path to a log file in the root SugarCRM directory. If there's no such log file as the one you specify, it will be created. Put the file path to the SugarCRM installation that you're about to upgrade in the place of (path to your SugarCRM instance), and in the place of (your admin name) type the admin name that you use to log in to your SugarCRM application.
After you execute the command the upgrade will be performed and you will be notified whether it's successful. Then log in to the application, go to the admin panel click on the button Repair and then on Rebuild Relationships.
For some more details you can also check out the SugarCRM silent upgrade tutorial.