UNITE works against XML site definitions. They tell it what to do. Since version 4.0.0 there is only one way to use UNITE: running it against a single XML file. Please note that batch mode, the default in versions 1.0 to 3.0 and which was deprecated in 3.1, has now been removed. You can always use a for-loop in your command line shell's scripting language to achieve the same result.
Your CRON job needs to run the
file with the path to the XML site definition for the site you want to
restore as its argument. A sample CRON command line looks like
/usr/bin/php-cli /path/to/unite.phar /home/myuser/backups/mysite.xml
Keep in mind that scheduling of the CRON script is the responsibility of the user. This is customarily done through the Control Panel of your web server.
If you are not sure how CRON jobs work, we advise you to consult the following third-party resources: