I got a CyberPower UPS to protect my Freenas box. I connected the included UPS cable and I noticed these errors in dmesg and the UPS service would not start.
ugen2.4: at usbus2 (disconnected) ugen2.4: at usbus2 ugen2.4: at usbus2 (disconnected) ugen2.4: at usbus2 ugen2.4: at usbus2 (disconnected) ugen2.4: at usbus2 ugen2.4: at usbus2 (disconnected) ugen2.4: at usbus2 ugen2.4: at usbus2 (disconnected) ugen2.4: at usbus2 ugen2.4: at usbus2 (disconnected) ugen2.4: at usbus2 ugen2.4: at usbus2 (disconnected) ugen2.4: at usbus2 ugen2.4: at usbus2 (disconnected) ugen2.4: at usbus2 ugen2.4: at usbus2 (disconnected) ugen2.4: at usbus2 ugen2.4: at usbus2 (disconnected) ugen2.4: at usbus2 ugen2.4: at usbus2 (disconnected) ugen2.4: at usbus2
After sprinkling a little google dust, I came across the following posts:
https://blog.grogscave.net/2013/12/suppressing-messages-in-freenasfreebsd.html
http://www.castro.aus.net/~maurice/OddsAndEnds/blog/files/Cyberpower-BR850ELCD-UPS-FreeBSD.html
I edited /etc/devd.conf and added the following then restarted the Freenas.
nomatch 10 { match "bus" "uhub[0-9]+"; match "vendor" "0x0764"; match "product" "0x0501"; };
UPS service started successfully and I was no longer seeing the disconnect errors in dmesg or /var/log/message
Oct 7 13:18:04 freenas ugen2.4: at usbus2 Oct 7 13:35:11 freenas ugen2.4: at usbus2
Time to set up auto shutdown!