TerraMaster Forum

I am facing a critical issue with TOS 6 where the NAS automatically shuts down after about 45–50 minutes when a USB UPS is connected. Here is a summary of the diagnostic details:

The UPS Status: The APC BX950 UPS hardware is perfectly fine. The internal self-tests are successful, and the UPS logs confirm that it is broadcasting valid telemetry data through the USB cable.

The Root Cause: The built-in NUT (Network UPS Tools) service cannot maintain a stable connection to the USB port because it lacks proper execution privileges. While the service starts up, the OS permissions eventually block the process from reading the /dev/bus/usb/ interface.

The Consequence: Because NUT loses connection to the UPS, TOS misinterprets this as a critical power event and forcefully triggers a system shutdown after 45 minutes to protect the data.

The Blocker: I tried to fix this via SSH (sudo), but TOS 6 prevents modifying system configurations or adding custom udev rules, returning Permission denied even for elevated superusers.

Relevant Technical Details: NUT Version: Network UPS Tools upsd 2.8.0

The Key Log Error: usb_set_report: Protocol error (or insufficient permissions)
Data lookup failed: Got disconnected by another driver?
Since this seems to me ar system-level permission bug in TOS 6, is there any official fix or a workaround to grant the NUT service permanent root access to the USB bus without rebuilding the rootfs?

Additional Note: As further proof of the system lock, I managed to temporarily fix the UPS timer settings using CLI commands, but all these modifications were completely wiped out and restored to default after a system reboot.
sed -i 's/offdelay = 2700/offdelay = 30/g' /usr/etc/nut/ups.conf
sed -i 's/ondelay = 600/ondelay = 60/g' /usr/etc/nut/ups.conf

Thanks for any help!

Sorry for the inconvenience, we checked carefully and found the UPS model you use is not on our compatibility list
https://www.terra-master.com/pages/comp ... tab_A8cfP6
It's recommended to choose UPS model from our compatibility list and verify if the issue persists.

MikeZhang wrote: ↑15 Jun 2026, 17:57

Really? APC models are pretty common and tend to be standardised to work with usual drivers.
Maybe check the Nut Compatibility lists.

MikeZhang wrote: ↑15 Jun 2026, 17:57

Dear MikeZhang,

Thank you for your response. However, I am quite surprised by this answer because the root cause of the issue does not seem to be related to the specific UPS model.

According to the system logs, the APC BX950 is communicating and broadcasting telemetry data over the USB cable flawlessly. The actual problem is that the built-in NUT (Network UPS Tools) service does not have the necessary system-level permissions to access the USB bus (/dev/bus/usb/) on TOS 6.

Because the driver is blocked by OS permissions, it eventually drops the connection, which TOS then misinterprets as a power failure and triggers a shutdown. This permission issue would happen with any UPS model connected via USB, regardless of whether it is on the compatibility list or not.

Could you please let me know how I can manually grant elevated root privileges or modify the udev rules for the NUT service on TOS 6 so it can maintain a stable connection?

Balage911 wrote: ↑15 Jun 2026, 20:03

To ensure your data security and long-term system stability, we strongly recommend that you choose a UPS model from the compatibility list. Devices on the compatibility list have undergone rigorous testing for physical electrical performance, communication robustness, and various extreme power outage scenarios, ensuring the absolute reliability of core power management services.

Risk Warning: Any drastically modify system bus permissions via SSH command line, low-level udev rules, mount overrides, or scheduled tasks are unofficially supported. Such modifications may lower the system's security level and may even cause unknown system conflicts, external device access errors, or service deadlocks during future TOS system upgrades.

If the issue still persists with compatible UPS, please contact us via official online chat

MikeZhang wrote: ↑16 Jun 2026, 19:19

Thats kind of a "I don't want take care your issue" answer to me.

Maybe the easiest way if I wait for TOS7 and if that OS is also that shitty than TOS6 than swich to an another OS.

But thanks for your answer, I guess.

Balage911 wrote: ↑18 Jun 2026, 04:57

Is your current system version the latest TOS 6.0.794? When logging in using the built-in terminal, the super administrator user has the highest privileges, so you don't need to add sudo before the command.