Re: Write and external script to delete manual backups possible?

Well, you'd have to look in the database for your system to check, but the SQL query is going to look something like:

$sql = "SELECT * FROM {files} WHERE component = 'user' AND filearea = 'backup' AND timemodified < :time";

$params = ['time' => time() - (6 * 30 * DAYSECS)];

$files = $DB->get_records_sql($sql, $params);

But, again, you'd have to look in your database to double-check exactly which 'filearea' and 'component' values you are looking for (the local DB only has a 'no user' backup, which, from memory, I think are stored slightly differently).