How to set on config.php the full path to the directory where you want to save the backup files

Hi,
Can anyone please confirm what $CFG property should I set on config.php to indicate the full path to the directory where you want to save the backup files, when having "$CFG->preventexecpath = true".

Is it "$CFG->backup_auto_destination"? Can't find any information about it on config-dist.php.

Thank you in advance,
susana