Monitoring a UPS with Nut and lighttpd on Linux - Part 1

Matt Pogue

5.00/5 (2 votes)

Jun 13, 2022

CPOL

3 min read

5701

How to monitor a UPS with Nut and lighttpd on Linux

UPDATE: An astute reader posted the following comment for anyone who may be attempting to implement this solution on a Raspberry Pi running with the pi-hole setup (see https://pi-hole.net/). The full comment:

I needed to use the info here: https://www.reddit.com/r/pihole/comments/hauphd/adding_apcupsd_ups_status_util_to_rpi_with/ in order to get it fully working. For some reason, it wasn't able to launch the .cgi file until I aliased the nut directory. My lighttpd.conf has these differences:

server.modules = ( "modaccess", "modaccesslog", "modauth", "modalias", "modexpire", 
                   "modredirect", "modrewrite", "modfastcgi", "modsetenv", "modstatus" )

alias.url = ( "/nut" => "/usr/share/nut/www/")

and now nut works with lighttpd + pihole

Thanks Rob!

We all know the importance of having a battery backup solution for your servers and network equipment; in a small company environment where cost is a factor, the purpose of the battery backup is somewhat different. Typically, the goal isn't all day (or even multi-hour) run time, but rather 20 - 30 minutes - long enough to cover short outages and notify and gracefully shut down the equipment in a longer outage. Again, YMMV of course depending on the needs of your organization. The purpose of these articles is to walk through configuring the nut-server service on a Proxmox host server and the nut-client service on a Linux guest, including email notification and graceful server shutdown for all VM's.

Recently, I had to replace an aging UPS with a new unit and based on cost, user reviews, and technical capability, I selected the Tripp Lite SMART1500RM2U. For our purposes, we'll assume that our UPS unit is connected via USB to our Proxmox host server named VMSERVER.

Before plugging it in, let's start a persistent tail of /var/log/messages to ensure that the UPS gets picked up by the operating system. Open a new SSH session to the host and we'll tail the log file, watching for the USB entries. We should see output similar to the following:

root@vmserver [~]# tail -f /var/log/messages
Oct 26 09:32:03 vmserver kernel: [149701.226307] 
       usb 1-11: SerialNumber: 3122CVYSM88EC01815
Oct 26 09:32:03 vmserver kernel: [149701.275704] 
       hid-generic 0003:09AE:3015.270B: hiddev0,hidraw0: USB HID v1.10 
       Device [Tripp Lite  TRIPP LITE SMART1500RM2U ] on usb-0000:00:14.0-11/input0
Oct 26 09:32:17 vmserver kernel: [149715.705236] 
       usb 1-11: USB disconnect, device number 36
Oct 26 09:32:18 vmserver kernel: [149716.051727] 
       usb 1-11: new low-speed USB device number 37 using xhci_hcd
Oct 26 09:32:18 vmserver kernel: [149716.209951] 
       usb 1-11: New USB device found, idVendor=09ae, idProduct=3015, bcdDevice= 2.0a
Oct 26 09:32:18 vmserver kernel: [149716.209960] 
       usb 1-11: New USB device strings: Mfr=2, Product=3, SerialNumber=4
Oct 26 09:32:18 vmserver kernel: [149716.209965] 
       usb 1-11: Product: TRIPP LITE SMART1500RM2U
Oct 26 09:32:18 vmserver kernel: [149716.209969] 
       usb 1-11: Manufacturer: Tripp Lite
Oct 26 09:32:18 vmserver kernel: [149716.209972] 
       usb 1-11: SerialNumber: 3122CVYSM88EC01815
Oct 26 09:32:18 vmserver kernel: [149716.259635] 
       hid-generic 0003:09AE:3015.270C: hiddev0,hidraw0: USB HID v1.10 
       Device [Tripp Lite  TRIPP LITE SMART1500RM2U ] on usb-0000:00:14.0-11/input0

From our log entries above, we can see that the UPS has been recognized by the operating system so we can now install and configure nut-server and nut-client.

Install nut, nut-client, nut-server, nut-cgi, and lighttpd using apt-get:

root@vmserver [~]# apt-get install nut nut-client nut-server nut-cgi lighttpd
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
  libltdl7 libnutscan1 libupsclient4 libusb-0.1-4 lighttpd-mod-deflate 
  lighttpd-mod-openssl spawn-fcgi
Suggested packages:
  rrdtool php-cgi php-fpm apache2-utils lighttpd-doc lighttpd-mod-authn-gssapi 
  lighttpd-mod-authn-pam lighttpd-mod-authn-sasl lighttpd-mod-geoip 
  lighttpd-mod-maxminddb lighttpd-mod-trigger-b4-dl lighttpd-mod-vhostdb-pgsql
  lighttpd-mod-webdav lighttpd-modules-dbi lighttpd-modules-ldap 
  lighttpd-modules-lua lighttpd-modules-mysql nut-monitor nut-ipmi nut-snmp nut-xml
The following NEW packages will be installed:
  libltdl7 libnutscan1 libupsclient4 libusb-0.1-4 lighttpd 
  lighttpd-mod-deflate lighttpd-mod-openssl nut nut-cgi nut-client 
  nut-server spawn-fcgi
0 upgraded, 12 newly installed, 0 to remove and 65 not upgraded.
Need to get 2,360 kB/2,786 kB of archives.
After this operation, 9,075 kB of additional disk space will be used.
Do you want to continue? [Y/n]

I configured nut using the steps in this article.
NOTE: If you're not rebooting the server, you'll need to restart udev like so: systemctl restart udev (it's not mentioned in the article).

Load the CGI module in the lighttpd configuration and restart lighttpd:

root@vmserver [/etc/nut]# lighttpd-enable-mod cgi
Enabling cgi: ok
Run "service lighttpd force-reload" to enable changes

root@vmserver [/etc/nut]# service lighttpd force-reload

Check the UPS status by visiting http://<server name/IP>/cgi-bin/upsstats.cgi in your browser. You should see a page similar to the following:

UPS Status - HTML Page

Now that the nut server is functional, you can install the nut client on the Proxmox guest systems. On Linux, you can install the client with apt-get:

root@linuxappserver [~]# apt-get install nut-client
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
  bash-completion libupsclient4
Suggested packages:
  nut-monitor
The following NEW packages will be installed:
  bash-completion libupsclient4 nut-client
0 upgraded, 3 newly installed, 0 to remove and 28 not upgraded.
Need to get 673 kB of archives.
After this operation, 2,348 kB of additional disk space will be used.
Do you want to continue? [Y/n]

Check the nut server with the upsc command:

upsc tripplite@vmserver ups.status

You should get output similar to the following:

root@linuxappserver [/var/log]# upsc tripplite@vmserver ups.status
Init SSL without certificate database
OL

Modify the nut configuration files:

nut.conf:

MODE=netclient

upsmon.conf:

RUN_AS_USER root

MONITOR tripplite@vmserver.wwf-mgt.com 1 admin secret slave

MINSUPPLIES 1
SHUTDOWNCMD "/sbin/shutdown -h now"
NOTIFYCMD /usr/sbin/upssched
POLLFREQ 2
POLLFREQALERT 1
HOSTSYNC 15
DEADTIME 15
POWERDOWNFLAG /etc/killpower

NOTIFYMSG ONLINE    "UPS %s on line power"
NOTIFYMSG ONBATT    "UPS %s on battery"
NOTIFYMSG LOWBATT   "UPS %s battery is low"
NOTIFYMSG FSD       "UPS %s: forced shutdown in progress"
NOTIFYMSG COMMOK    "Communications with UPS %s established"
NOTIFYMSG COMMBAD   "Communications with UPS %s lost"
NOTIFYMSG SHUTDOWN  "Auto logout and shutdown proceeding"
NOTIFYMSG REPLBATT  "UPS %s battery needs to be replaced"
NOTIFYMSG NOCOMM    "UPS %s is unavailable"
NOTIFYMSG NOPARENT  "upsmon parent process died - shutdown impossible"

NOTIFYFLAG ONLINE   SYSLOG+WALL+EXEC
NOTIFYFLAG ONBATT   SYSLOG+WALL+EXEC
NOTIFYFLAG LOWBATT  SYSLOG+WALL
NOTIFYFLAG FSD      SYSLOG+WALL+EXEC
NOTIFYFLAG COMMOK   SYSLOG+WALL+EXEC
NOTIFYFLAG COMMBAD  SYSLOG+WALL+EXEC
NOTIFYFLAG SHUTDOWN SYSLOG+WALL+EXEC
NOTIFYFLAG REPLBATT SYSLOG+WALL
NOTIFYFLAG NOCOMM   SYSLOG+WALL+EXEC
NOTIFYFLAG NOPARENT SYSLOG+WALL

RBWARNTIME 43200

NOCOMMWARNTIME 600

FINALDELAY 5

That covers the basic setup of server and client for Linux. I will finish addressing the Promox-specific pieces - including email notification and guest shutdown - in Part 2 of this article.

If you have questions about the article or if you're trying to follow along and having problems, I'd be happy to help as best I can. Please leave a comment below.