Create a course. Create a failed backup. I edited the backup_stepslib.php file and put a die(); in one of the functions. Check moodledata/temp/backup and ensure that there are directories listed there. Update the scheduled task "Clean up failed backup files from the temp directory" [Site administration ► Server ► Scheduled tasks] and change all of the times to '*'. I don't recommend waiting a week to see if the files get deleted, so I would change the following (lib/classes/task/file_temp_cleanup_task.php): $time = strtotime('-1 week'); to $time = strtotime('-1 minute'); Run the cron. Have a look in the temp/backup directory and check that all of the directories have been removed.