It is strongly recommended to create a backup before starting the update process. If you have important data, create and try to restore a backup to ensure that everything works properly.
You can upgrade the application only without modifying any other stack components, as described below:
Ensure that you establish a PHP memory limit of at least 2 GB, in installdir/php/etc/php.ini:
$ sudo installdir/ctlscript.sh restart apache
Visit the Magento Marketplace and obtain your public/private access key pair using the “My Account -> Connect -> Developers -> Secure Keys” section. If you don’t have a Magento Marketplace account, create one here.
Log in to Magento’s administration panel and navigate to the “System -> Web Setup Wizard -> System Configuration” section.
Enter the public and private keys and click “Save Config” to save the changes.
Navigate to the “System -> Web Setup Wizard -> System Upgrade” section.
The upgrade process should begin. Follow the prompts to complete the upgrade.
For more information, refer to the Magento documentation.