To find your system files, look for the config.inc.php configuration file; this will be in the directory where you originally installed OJS. Back up all files in this directory and all subdirectories. Assuming OJS is installed in /var/www/html/ojs and the backup should be placed in /root, the following example will compress the OJS system files to a file in /root/ called ojs-install.tar.gz:

$ cd /var/www/html/ojs
$ tar czf /root/ojs-install.tar.gz *