If you see the error message:
Set the appropriate path in BACKUP_PATH variable in the configuration file [config/Components/Backup.php] to enable it.
and also see it from error.log
Undefined index: query_cache_size in /var/www/yetiforce/app/Db.php on line 169
Undefined variable: typeDb in /var/www/yetiforce/app/Db.php on line 174
Undefined index: in /var/www/yetiforce/app/Utils/ConfReport.php on line 712
Undefined index: www in /var/www/yetiforce/app/Utils/ConfReport.php on line 813
First you need create a folder under /var/www/yetiforce/
jimlee@CRMServer:~$ cd /var/www/yetiforce
jimlee@CRMServer:/var/www/yetiforce$ sudo mkdir backup
Then change the permission
jimlee@CRMServer:/var/www/yetiforce$ sudo chown -R www-data:www-data /var/www/yetiforce/backup/
jimlee@CRMServer:/var/www/yetiforce$ sudo chmod -R 755 /var/www/yetiforce/backup/
No we need add the path to the /var/www/yetiforce/config/backup.php
/** Backup catalog path. */
public static $BACKUP_PATH = '/var/www/yetiforce/backup/';