Tag: RHEL10

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

# 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 trigger

Firewall

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 --reload

Service 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:

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-client

And test

$ upsc tripplite@10.1.10.21

Prepare 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-agent

Create the Zabbix Agent UserParameters

sudo vi /etc/zabbix/zabbix_agentd.d/nut_tripplite.conf

Paste 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-agent

Now 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:

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_final

Install the Policy

The previous command created a file called zabbix_nut_final.pp. Now, load it into the kernel:

 semodule -i zabbix_nut_final.pp

You should now see data returning in the Zabbix WebUI. You may need to wait a few second or re-run the check.