From what documentation I could find, the UPS should be (is!) supported by Linux and ought to work with apcupsd. I looked for specific problems such as the infamous Microlink protocol, and found none. I have found a feedback from a guy in UK that reports using this very model on a not-too-different OS version (his OpenSuSE 12.1, mine 12.3 x86_64). The USB port is detected, lsusb reports Bus 002 Device 003: ID 051d:0002 American Power Conversion Uninterruptible Power Supply and lsusb -v -s002:003 confirms and expands: Bus 002 Device 003: ID 051d:0002 American Power Conversion Uninterruptible Power Supply Device Descriptor: bLength 18 bDescriptorType 1 bcdUSB 2.00 bDeviceClass 0 (Defined at Interface level) bDeviceSubClass 0 bDeviceProtocol 0 bMaxPacketSize0 64 idVendor 0x051d American Power Conversion idProduct 0x0002 Uninterruptible Power Supply bcdDevice 0.90 iManufacturer 1 American Power Conversion iProduct 2 Back-UPS RS 900G FW:879.L4 .I USB FW:L4 bNumConfigurations 1 Configuration Descriptor: [...] Interface Descriptor: [...] bInterfaceClass 3 Human Interface Device bInterfaceSubClass 0 No Subclass bInterfaceProtocol 0 None iInterface 0 HID Device Descriptor: bLength 9 bDescriptorType 33 bcdHID 1.00 bCountryCode 33 US bNumDescriptors 1 bDescriptorType 34 Report wDescriptorLength 1134 Report Descriptors: ** UNAVAILABLE ** Endpoint Descriptor: bLength 7 bDescriptorType 5 bEndpointAddress 0x81 EP 1 IN bmAttributes 3 Transfer Type Interrupt Synch Type None Usage Type Data wMaxPacketSize 0x0008 1x 8 bytes bInterval 100 Device Status: 0x0000 (Bus Powered) The kernel recognizes this and duly sets up crw------- 1 root root 180, 96 Nov 4 16:11 /dev/usb/hiddev0 As far as I know, everything is as it should be. I have put the standard configuration in /etc/apcupsd/apcupsd.conf (which is Unix-terminated, ASCII-only, no BOM (just in case)) UPSCABLE usb UPSTYPE usb DEVICE (I have also tried commenting out DEVICE, and setting a device of /dev/puppa results in an access attempt to /dev/puppa, not some /var/lib/dev/puppa or /dev/puppa\r\n). Yet, what apcaccess tells me is VERSION : 3.14.10 (13 September 2011) suse CABLE : USB Cable DRIVER : USB UPS Driver UPSMODE : Stand Alone STARTTIME: 2013-11-04 16:24:22 +0100 MODEL : STATUS : NOBATT LINEV : 000.0 Volts LOADPCT : 0.0 Percent Load Capacity BCHARGE : 000.0 Percent TIMELEFT : 0.0 Minutes MBATTCHG : 5 Percent MINTIMEL : 3 Minutes MAXTIME : 0 Seconds SENSE : Low LOTRANS : 000.0 Volts HITRANS : 000.0 Volts It doesn't recognize the model, and reports no battery (and no voltage). This confirms that it's not the Microlink problem, or it would report the battery status, if precious little else. If I disconnect the USB cable, I get an apcupsd message to the effect that communications have been lost; and I get the "communication restored" broadcast too, if I reconnect the cable. apcupsd is monitoring. So everything tells me that it should work -- only it doesn't. Does anyone spot what I'm missing?