UGREEN NAS models (the NASync DXP series, such as the DXP2800, DXP4800 Plus, DXP6800 Pro and DXP8800 Plus) come with a watchdog turned on in the BIOS. The watchdog waits for UGREEN's own operating system, UGOS, to check in. HexOS does not check in, so the watchdog restarts the server about 3 minutes after it turns on.
You might see one of these:
The fix is one BIOS setting and takes about five minutes.
Tip: Turn the watchdog off before you install HexOS. Otherwise it can restart the server in the middle of the installation.
Ctrl and press F2 a few times.Ctrl + F12. On some models this opens a boot menu first, where you can choose to enter setup.Info: Menu names vary between models and BIOS versions. On some models with an Intel Core i5 processor the watchdog setting is on the FAST tab instead. If you still cannot find it, look under Hardware Monitor.
Press F10 and confirm to save your changes and exit. You can also use the Save & Exit tab. The NAS restarts.
Leave the watchdog turned off. HexOS does not use it, and turning it on again brings the restarts back.
Wait at least five minutes after the HexOS console screen appears. If the server has not restarted, the watchdog is off.
If you were installing HexOS, start the installation again from the USB drive. If HexOS is already installed, go to deck.hexos.com and claim your server.
Help: Still restarting? Ask in the HexOS Discord Community and tell us your UGREEN model.
Related: Installation issues and Illustrated installation guide