[Nut-upsuser] Two APC UPS deivces, Fedora, slightly lost

[Charles Lepple]

I haven't used NUT on Fedora, but your ups.conf seems to be on the right track (symlinks will not help for devices supported by usbhid-ups).

There are not many USB product IDs for APC UPSes, but do you get different IDs from "lsusb -d 051d:? Matching product IDs uses simpler logic than matching strings.

A while back, we had issues with Linux guests not getting all of the USB information when on an ESXi hypervisor. That may not be the case if your host machine is physical, but there is still a possibility that the driver is having trouble during the stage when it iterates through all of the USB devices to retrieve strings like serial numbers. Check the logs for any messages saying that the driver couldn't read the serial number - probably from something like "journalctl -t usbhid-ups". Specifics of increasing the driver debug level may depend on your version of NUT (and whether/how the packager changed the systemd service definitions).

If that doesn't work, you can try plugging the UPSes into different USB ports (i.e. not into a hub) and using the "bus" parameter in ups.conf, which may need to be adjusted after a major kernel upgrade if the USB stack enumerates the buses in a different order.

-- 
Charles Lepple
clepple at gmail

> On Apr 29, 2026, at 6:55 PM, Gavin Davenport <gavdav at gavdav.net> wrote:
> 
> I have 2 APC UpS devices – I have a group of 4 machines connected to various outputs on them and they are connected by USB to the same fedora host.
>  
> I’m having issues with nut reliabl discovering both devices
>  
> Here’s my ups.conf
>  
>   [850g2]
>       driver = usbhid-ups
>       port = auto
>       desc = "APC Back-UPS ES 850G2"
>       serial = 5B1932T42066
>  
>   [1050g2]
>       driver = usbhid-ups
>       port = auto
>       desc = "APC Back-UPS BE1050G2"
>       serial = 9B2545A15277
>  
> I’m hoping nut will match on the serial number of the device.
>  
> I’ve been rather led astray by chatgpt making stuff up and then forgetting where it is – so I’m a bit confused about whether I try to have udev prepare the appropriate symlinks for nut
>  
> I’ve had this working (2 Ups devices being monitored, but all a bit hand-cranked). I can’t get it to survive a reboot.
> 
> Are there any known issues with using 2 APC Ups devices which announce themselves very similarly ?
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