qnap

rsync

Do NOT edit crontab the usual way! crontab -e

However, due to the way the QNAP firmware updates crontab, it will be overwritten on the next reboot. Obviously, you want your automation to survive reboots, so edit the crontab file directly with your text editor:

vim /etc/config/crontab

When you're done, reload the crontab file and restart the cron daemon:

crontab /etc/config/crontab && /etc/init.d/crond.sh restart

https://wiki.qnap.com/wiki/Add_items_to_crontab