My home server is protected by an MGE Ellipse 750 UPS for years. I bought it for several reasons: it’s affordable, has good capacity and is Ubuntu certified.
I also read back then rumors implying that Nut’s maintainer was employed by MGE. Having a hardware manufacturer employing a fellow open-source hacker has certainly influenced my purchase decision.
MGE is no more and has been merged with EATON. But my UPS is still supported, and the release of Debian Squeeze is a good opportunity to consolidate my knowledge in the form of this tutorial.
So here is how I setup Nut on Debian Squeeze to monitor my UPS.
First things first, we have to install the main package and its USB driver:
1 $ aptitude install nut nut-usb
Now let’s configure Nut and run it:
1$ sed -i 's/MODE=none/MODE=standalone/g' /etc/nut/nut.conf2$ echo '3[MGE-Ellipse750]4driver = usbhid-ups5port = auto6desc = "MGE UPS Systems"7' >> /etc/nut/ups.conf8$ sed -i 's/# LISTEN 127\.0\.0\.1 3493/LISTEN 127\.0\.0\.1/g' /etc/nut/upsd.conf9$ echo '10[kevin]11password = badpassword12upsmon master13' >> /etc/nut/upsd.users14$ sed -i 's/# NOTIFYCMD \/usr\/local\/ups\/bin\/notifyme/NOTIFYCMD \/sbin\/upssched/g' /etc/nut/upsmon.conf15$ echo '16MONITOR MGE-Ellipse750@localhost 1 kevin badpassword master17NOTIFYFLAG ONBATT SYSLOG+WALL+EXEC18NOTIFYFLAG ONLINE SYSLOG+WALL+EXEC19' >> /etc/nut/upsmon.conf20$ sed -i 's/CMDSCRIPT \/upssched-cmd/CMDSCRIPT \/etc\/nut\/upssched-cmd/g' /etc/nut/upssched.conf21$ sed -i 's/# PIPEFN \/var\/run\/nut\/upssched\/upssched.pipe/PIPEFN \/var\/run\/nut\/upssched.pipe/g' /etc/nut/upssched.conf22$ sed -i 's/# LOCKFN \/var\/run\/nut\/upssched\/upssched.lock/LOCKFN \/var\/run\/nut\/upssched.lock/g' /etc/nut/upssched.conf23$ echo '24AT ONBATT * START-TIMER onbatt 3025AT ONLINE * CANCEL-TIMER onbatt26' >> /etc/nut/upssched.conf27$ echo '28#!/bin/sh29exit 030' > /etc/nut/upssched-cmd31$ /etc/init.d/nut restart
As you can see you have lots of stuff to configure before Nut can do what it was designed for. But after all of these commands, you should have a working UPS.
You can now test that your system works by using the command below, which list statistics of a given UPS:
1 $ upsc MGE-Ellipse750@localhost
But in some rare cases, your UPS will not be recognized and you’ll have like me the following messages in your /var/log/syslog:
May 5 16:12:36 paris-server upsmon[10773]: Poll UPS [[email protected]] failed - Driver not connected
In this case, you should run Nut’s driver in debug mode:
1$ /lib/nut/usbhid-ups -DDD -a MGE-Ellipse7502Network UPS Tools - Generic HID driver 0.34 (2.4.3)3USB communication driver 0.3140.000000 debug level is '3'50.013911 upsdrv_initups...60.189541 Checking device (0463/FFFF) (005/003)70.189705 - VendorID: 046380.189741 - ProductID: ffff90.189767 - Manufacturer: unknown100.189794 - Product: unknown110.189819 - Serial Number: unknown120.189842 - Bus: 005130.189862 Trying to match device140.189906 Device matches150.189954 failed to claim USB device: could not claim interface 0: Operation not permitted160.189995 failed to detach kernel driver from USB device: could not detach kernel driver from interface 0: Operation not permitted170.190033 failed to claim USB device: could not claim interface 0: Operation not permitted180.190070 failed to detach kernel driver from USB device: could not detach kernel driver from interface 0: Operation not permitted190.190108 failed to claim USB device: could not claim interface 0: Operation not permitted200.190145 failed to detach kernel driver from USB device: could not detach kernel driver from interface 0: Operation not permitted210.190181 failed to claim USB device: could not claim interface 0: Operation not permitted220.190217 failed to detach kernel driver from USB device: could not detach kernel driver from interface 0: Operation not permitted230.190252 Can't claim USB device [0463:ffff]: could not detach kernel driver from interface 0: Operation not permitted
As you can see in messages above, Nut can’t see my UPS. By chance, forcing nut to use the root user let it see my UPS:
1$ /lib/nut/usbhid-ups -DDD -u root -a MGE-Ellipse7502Network UPS Tools - Generic HID driver 0.34 (2.4.3)3USB communication driver 0.3140.000000 debug level is '3'50.001678 upsdrv_initups...60.172877 Checking device (0463/FFFF) (005/003)71.112408 - VendorID: 046381.112464 - ProductID: ffff91.112489 - Manufacturer: MGE OPS SYSTEMS101.112516 - Product: ELLIPSE111.112542 - Serial Number: BDCJ3800Q121.112569 - Bus: 005131.112595 Trying to match device141.112647 Device matches151.112726 failed to claim USB device: could not claim interface 0: Device or resource busy161.113239 detached kernel driver from USB device...171.251394 HID descriptor, method 1: (9 bytes) => 09 21 00 01 21 01 22 01 03181.251460 HID descriptor, method 2: (9 bytes) => 09 21 00 01 21 01 22 01 03191.251491 HID descriptor length 769201.351379 Report Descriptor size = 769211.351456 Report Descriptor: (769 bytes) => 05 84 09 04 a1 01 09 24 a1 00 09 02 a1 00221.351509 55 00 65 00 85 01 75 01 95 05 15 00 25 01 05 85 09 d0 09 44 09 45 09 42 0b23(...)24
So the issue is now clear and is related to permissions. I was able to fix this issue by changing the permissions on the USB device corresponding to my UPS:
1 $ chmod 0666 /dev/bus/usb/005/003
Another working way to fix this is to change the group of the device to nut:
1 $ chown :nut /dev/bus/usb/005/003
BTW, to get the bus number (005 here) and device number (003 in my case) of your UPS, run lsudb:
1$ lsusb2Bus 005 Device 003: ID 0463:ffff MGE UPS Systems UPS3Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub4Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub5Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub6Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub7Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Of course this fix is absolutely temporary, as you’ll need to perform the change above after every reboot. This is far from practical. In fact, as describe in this Fedora 10 bug report, but also in some other Debian bug report, this issue is directly tied to conflicting Udev rules.
Based on clues from these bug reports you can fix Udev using different strategies. As I can’t decide which one is the cleanest, I just did something that is quite brutal, but works. It consist of replacing in /lib/udev/rules.d/91-permissions.rules the line setting rights for USBfs-like devices:
--- /lib/udev/rules.d/91-permissions.rules-orig 2011-05-05 18:49:08.015538434 +0200
+++ /lib/udev/rules.d/91-permissions.rules 2011-05-05 18:49:16.663537978 +0200
@@ -33,7 +33,7 @@
# usbfs-like devices
SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", \
- MODE="0664"
+ MODE="0666"
# serial devices
SUBSYSTEM=="tty",Now all you have to do is to unplug the power cord and wait until your machine gracefully shut down as soon as batteries are low! :)