To uninstall Tectonic from a bare-metal cluster, set cluster nodes to boot from your previous, standard PXE image.
Tectonic bare-metal clusters should be reprovisioned using the latest Tectonic bare-metal documentation. If you've setup your infrastructure as described, skip to step 4, Tectonic Installer. Use the Tectonic Installer application, then set your servers to PXE on the next boot and reboot:
ipmitool -H node.example.com -U USER -P PASS chassis bootdev pxe