root@72be92618e35:/var/www/html# php -f /var/www/html/cron.php
Console has to be executed with the user that owns the file config/config.php
Current user id: 0
Owner id of config.php: 1002
root@72be92618e35:/var/www/html# 



root@72be92618e35:/var/www/html# cat /var/spool/cron/crontabs/www-data
*/5 * * * * php -f /var/www/html/cron.php
root@72be92618e35:/var/www/html# 



the whole reason to run the container as a different user is to gain access to the file share
nextcloud has the ability to use file shares as external storage
but nextcloud has more data than what would go on the external storage, and that data also needs to be backed up

looks impossible to modify the cron job to run as a different user without customizing the container :(