Fresh install of Trusty 14.04.0 with *old* udev: # apt-cache policy udev udev: Installed: 204-5ubuntu20 Candidate: 204-5ubuntu20.24 Version table: 204-5ubuntu20.24 0 500 http://us.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages *** 204-5ubuntu20 0 500 http://us.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages 100 /var/lib/dpkg/status Plugging CyberPower USB cable: # udevadm monitor --subsystem-match=usb monitor will print the received events for: UDEV - the event which udev sends out after rule processing KERNEL - the kernel uevent KERNEL[212.661306] add /devices/pci0000:00/0000:00:1a.1/usb4/4-2 (usb) KERNEL[212.663416] add /devices/pci0000:00/0000:00:1a.1/usb4/4-2/4-2:1.0 (usb) UDEV [212.861460] add /devices/pci0000:00/0000:00:1a.1/usb4/4-2 (usb) UDEV [212.863063] add /devices/pci0000:00/0000:00:1a.1/usb4/4-2/4-2:1.0 (usb) Wrong perms: # find /dev/bus/usb/ -ls 7329 0 drwxr-xr-x 10 root root 200 Aug 29 16:14 /dev/bus/usb/ ... 7336 0 drwxr-xr-x 2 root root 80 Aug 29 16:17 /dev/bus/usb/004 11406 0 crw-rw-r-- 1 root root Aug 29 16:17 /dev/bus/usb/004/002 7337 0 crw-rw-r-- 1 root root Aug 29 16:14 /dev/bus/usb/004/001 ... Install nut-server # apt-get install -y nut-server # pulling 2.7.1-1ubuntu1 # lsusb | grep Cyber Bus 004 Device 002: ID 0764:0501 Cyber Power System, Inc. CP1500 AVR UPS Unplugging/re-plugging the CyberPower: # udevadm monitor --subsystem-match=usb monitor will print the received events for: UDEV - the event which udev sends out after rule processing KERNEL - the kernel uevent KERNEL[544.264436] remove /devices/pci0000:00/0000:00:1a.1/usb4/4-2/4-2:1.0 (usb) KERNEL[544.264626] remove /devices/pci0000:00/0000:00:1a.1/usb4/4-2 (usb) UDEV [544.271603] remove /devices/pci0000:00/0000:00:1a.1/usb4/4-2/4-2:1.0 (usb) UDEV [544.271648] remove /devices/pci0000:00/0000:00:1a.1/usb4/4-2 (usb) KERNEL[548.024486] add /devices/pci0000:00/0000:00:1a.1/usb4/4-2 (usb) KERNEL[548.027386] add /devices/pci0000:00/0000:00:1a.1/usb4/4-2/4-2:1.0 (usb) UDEV [548.186083] add /devices/pci0000:00/0000:00:1a.1/usb4/4-2 (usb) UDEV [548.187851] add /devices/pci0000:00/0000:00:1a.1/usb4/4-2/4-2:1.0 (usb) Notice that nut-server's 52-nut-usbups.rules worked: # find /dev/bus/usb/ -ls 7329 0 drwxr-xr-x 10 root root 200 Aug 29 16:14 /dev/bus/usb/ ... 7336 0 drwxr-xr-x 2 root root 80 Aug 29 16:23 /dev/bus/usb/004 12329 0 crw-rw-r-- 1 root nut Aug 29 16:23 /dev/bus/usb/004/003 7337 0 crw-rw-r-- 1 root root Aug 29 16:14 /dev/bus/usb/004/001 ... What's weird in the above is that udev reports it's adding 4-2 but the device is apparently at 4-3: # lsusb | grep Cyber Bus 004 Device 003: ID 0764:0501 Cyber Power System, Inc. CP1500 AVR UPS I did unplug/plug back in the exact same physical slot. Here's dmesg just in case: # dmesg -T | grep 0501 [Tue Aug 29 16:17:32 2017] usb 4-2: New USB device found, idVendor=0764, idProduct=0501 [Tue Aug 29 16:17:32 2017] hid-generic 0003:0764:0501.0002: hiddev0,hidraw1: USB HID v1.10 Device [CPS CP685AVR-G] on usb-0000:00:1a.1-2/input0 [Tue Aug 29 16:23:08 2017] usb 4-2: New USB device found, idVendor=0764, idProduct=0501 [Tue Aug 29 16:23:08 2017] hid-generic 0003:0764:0501.0003: hiddev0,hidraw1: USB HID v1.10 Device [CPS CP685AVR-G] on usb-0000:00:1a.1-2/input0