Selling one of my TNAS - remove all data

[lecce]

I have multiple TNAS units; I plan to sell an older one on Ebay.

How do I ensure that the device has none of my data left on it?

I will remove the hard drives from the caddies. But I am aware there is some TOS software installed internally in the unit, either on a USB stick or possibly on some other storage.

Is it guaranteed that none of my data (e.g. TOS setup with passwords, IP addresses) is present if I just remove the drives I added?

[crisisacting]

The internal USB is purely for initialization; there's no user data stored on it as it looks for a certain path on mounted HDD(s) to boot from that/those if TOS is installed, otherwise it'll load from the USB to go through the initial boot wizard.

Removing your caddied drives has sufficiently taken your data away.