In my personal lab I do not have a network managed UPS. My rack mount UPS can only be monitored via USB from a directly connected host.
This guide details the installation and configuration of Network UPS Tools (NUT) to monitor a Tripp Lite USB PDU and prepare it for Zabbix integration.
Prerequisites & Installation
Install the necessary NUT packages. RHEL 10 uses the 2.8.x branch, which introduces an “instantiated” service model.
sudo dnf install nut nut-client nut-server
Directory Structure Setup
RHEL 10 defaults to /etc/ups, we will use /etc/nut to ensure our configuration files are in the correct location and we will create a symbolic link for legacy compatibility.
# Move config if it exists in the old /etc/ups location
sudo mkdir -p /etc/nut
sudo mv /etc/ups/* /etc/nut/ 2>/dev/null
sudo ln -s /etc/nut /etc/ups
Configuration Files
The following files in /etc/nut/ must be configured:
nut.conf
Set the operation mode:
MODE=netserver
NUT (Network UPS Tools) Netserver Mode is a configuration where one machine (the server) connects to a UPS, monitors it, and then broadcasts the power status and alerts (like “on battery”) across the local network
ups.conf
Define the hardware driver. Note the exact spelling of the section name [tripplite].
[tripplite]
driver = usbhid-ups
port = auto
desc = "Tripp Lite USB PDU"
upsd.conf
Control network listening. To allow remote connections (like from a Zabbix server), you must listen on the host’s IP or all interfaces (0.0.0.0).
LISTEN 127.0.0.1 3493
LISTEN 10.1.10.21 3493
upsd.users
Define a user for Zabbix or remote monitoring:
[zabbix]
password = your_secure_password
upsmon master
USB Permissions (udev)
Create a rule to allow the nut user to access the USB bus for Tripp Lite devices (Vendor ID 09ae).
Create file: /etc/udev/rules.d/99-nut-ups.rules and add content shown below.
ACTION=="add", SUBSYSTEM=="usb", ATTR{idVendor}=="09ae", GROUP="nut", MODE="0660"Then apply
sudo udevadm control --reload-rules && sudo udevadm triggerFirewall
You need to allow inbound port 3493 since we want to be able to poll the ups remotely from a Zabbix host.
# Open port 3493 permanently
sudo firewall-cmd --permanent --add-port=3493/tcp
sudo firewall-cmd --reloadService Management
RHEL 10 uses a specific sequence. You must trigger the “enumerator” to generate the systemd units for your specific PDU name.
# Force the system to recognize the [tripplite] section
sudo /usr/libexec/nut-driver-enumerator.sh
# Enable and start the driver instance
sudo systemctl enable --now nut-driver@tripplite.service
# Start the data server and monitoring daemon
sudo systemctl enable --now nut-server.service
sudo systemctl enable --now nut-monitor.service
Manual Check Commands
Use these commands to verify health:
| Command | Purpose |
upsc -l | Lists all configured UPS/PDU devices. |
upsc tripplite@localhost | Dumps all current PDU metrics (voltage, load, etc.). |
systemctl status nut-driver@tripplite | Checks if the USB driver is active and running. |
journalctl -u nut-driver@tripplite -f | Follow live logs if the USB connection drops. |
Test Remotely
From another host, install the nut-client. If this step does not work, but the same commands worked locally, you should double check your Firewall settings.
$ sudo apt install nut-clientAnd test
$ upsc tripplite@10.1.10.21Prepare the Zabbix Agent Permissions
To allow Zabbix to collect this data automatically. Run the two commands below on the host connected to UPS via USB
# sudo usermod -a -G nut zabbix
# sudo systemctl restart zabbix-agentCreate the Zabbix Agent UserParameters
sudo vi /etc/zabbix/zabbix_agentd.d/nut_tripplite.confPaste the following lines into the file above
# Discovery rule to find the UPS name
UserParameter=nut.ups.discovery,upsc -l | awk '{print "{\"{#UPSNAME}\":\"" $1 "\"}"}' | paste -sd "," | sed 's/^/{"data":[/' | sed 's/$/]}/'
# Fetch specific values (e.g., ups.load, output.voltage)
UserParameter=nut.ups.value[*],upsc $1@localhost $2 | grep -v "Value:"Now restart the zabbix agent
# sudo systemctl restart zabbix-agentNow verify that the Zabbix agent returns UPS data
# zabbix_agentd -t "nut.ups.value[tripplite,ups.load]"
nut.ups.value[tripplite,ups.load] [t|24]
Setting up the Zabbix Web UI
Lets create a simple template for zabbix. Follow the steps shown below.
Manual Item Creation
If you just want the most important metrics, go to your Host in Zabbix and create these Items:
| Name | Type | Key | Type of Information |
| PDU Load | Zabbix Agent | nut.ups.value[tripplite,ups.load] | Numeric (float) |
| Input Voltage | Zabbix Agent | nut.ups.value[tripplite,input.voltage] | Numeric (float) |
| Battery Charge | Zabbix Agent | nut.ups.value[tripplite,battery.charge] | Numeric (float) |
| PDU Status | Zabbix Agent | nut.ups.value[tripplite,ups.status] | Character |
Configuring SELinux
If you check the zabbix webui, you are going to see some failures, as we need to configure selinux.
Note that we configured Zabbix “items” first so that we would be able to capture the failures in the audit log and generate a policy.
So now that we have failures, we can tell RHEL to look at all recent security denials involving the zabbix_agent and write a “policy” that allows those specific actions.
# Search the audit log for zabbix-related denials and create a policy module
grep "zabbix" /var/log/audit/audit.log | audit2allow -M zabbix_nut_finalInstall the Policy
The previous command created a file called zabbix_nut_final.pp. Now, load it into the kernel:
semodule -i zabbix_nut_final.ppYou should now see data returning in the Zabbix WebUI. You may need to wait a few second or re-run the check.
