apcupsd_exporter forks and app setup

date:

tags: apcupsd ups prometheus golang open source software

categories: Homelab Software

This is a follow-up to my previous apcupsd post. Check that post out for an overview of this project but essentially the goal is to collect metrics from a UPS system manufactured by APC and present them in Prometheus format to scrape with Prometheus.

I forked the GitHub repositories needed for apcupsd_exporter and kept the MIT license in place. That means anyone can still use, modify, and redistribute the code under the same open source terms.

Using forks here gives me a stable base for my homelab while still keeping the project open for anyone else. So far I have just updated the project dependencies and configured Renovate to manage the dependencies.

Forks and license

I am now using my forked repositories:

  • apcupsd_exporter: GitHub
  • apcupsd library dependency: GitHub

Both remain under the MIT license.

apcupsd library changes (2026-02-28)

I also took over maintenance for my apcupsd library fork with two focused commits:

  • Commit 8dc22a9:
    • moved module/repo from github.com/mdlayher/apcupsd to github.com/acaylor/apcupsd
    • kept original attribution and added fork attribution in LICENSE.md and README.md
    • upgraded the project from Go 1.20 to 1.26
    • updated go-cmp from v0.5.9 to v0.7.0
    • added .gitignore and a clearer development section in README
    • updated CI matrices to test/analyze on Go 1.26
  • Commit d1cbec1:
    • disabled enumcheck in static analysis because its x/tools dependency is not compatible with Go 1.26 yet
    • kept staticcheck and go vet enabled
    • upgraded GitHub Actions from older versions (setup-go@v2, checkout@v2) to current versions (setup-go@v5, checkout@v4)

Short version: the fork is now clearly maintained, modernized for Go 1.26, and CI is stable while waiting for enumcheck compatibility to catch up.

apcupsd_exporter changes (2026-02-28)

I made a matching maintenance pass on my apcupsd_exporter fork so it builds and tests cleanly with modern Go:

  • switched exporter dependency from github.com/mdlayher/apcupsd to github.com/acaylor/apcupsd pinned at v0.1.0
  • updated imports and module files (go.mod/go.sum) to match
  • fixed tests for static analysis by replacing deprecated io/ioutil calls with io
  • upgraded GitHub Actions (setup-go v2 -> v5, checkout v2 -> v4)
  • moved CI from older multi-version Go matrices to Go 1.26 only, because both this repo and the client library now require Go 1.26

Short version: the exporter fork tracks my maintained apcupsd client, requires Go 1.26, and has a stable CI pipeline for testing and static analysis.

Fresh setup on a new Linux system

This example assumes a Debian or Ubuntu system with an APC UPS connected by USB.

1. Install apcupsd and basic tools

sudo apt update
sudo apt install -y apcupsd curl git tar

You can install go via apt repos but usually the version is old on Ubuntu and Debian: sudo apt install golang-go

If you are on Raspberry Pi, you can install Go manually (Go 1.26.0) before building the exporter:

wget https://go.dev/dl/go1.26.0.linux-arm64.tar.gz
sudo rm -rf /usr/local/go
sudo tar -C /usr/local -xzf go1.26.0.linux-arm64.tar.gz
export PATH=$PATH:/usr/local/go/bin
go version

To make that Go path persistent across sessions:

echo 'export PATH=$PATH:/usr/local/go/bin' >> ~/.profile
source ~/.profile

2. Configure apcupsd

Edit /etc/apcupsd/apcupsd.conf and make sure these values are set for USB:

UPSCABLE usb
UPSTYPE usb
DEVICE

If DEVICE has a serial device path, clear it for USB setups.

Restart and enable the service:

sudo systemctl enable --now apcupsd
sudo systemctl restart apcupsd
sudo systemctl status apcupsd --no-pager

Optional quick check:

apcaccess status

3. Build exporter from fork

Clone and build:

git clone https://github.com/acaylor/apcupsd_exporter.git
cd apcupsd_exporter/cmd/apcupsd_exporter
go build
./apcupsd_exporter

Expected startup log looks like:

starting apcupsd exporter on ":9162" for server tcp://:3551

Stop with Ctrl + C after testing.

4. Install exporter as a systemd service

sudo mkdir -p /opt/apcupsd_exporter
sudo cp apcupsd_exporter /opt/apcupsd_exporter/
sudo chmod 755 /opt/apcupsd_exporter/apcupsd_exporter
sudo useradd --system --no-create-home --shell /usr/sbin/nologin apcupsd_exporter

Create /etc/systemd/system/apcupsd_exporter.service:

[Unit]
Description=Prometheus exporter for apcupsd
After=network.target apcupsd.service

[Service]
Type=simple
User=apcupsd_exporter
Group=apcupsd_exporter
ExecStart=/opt/apcupsd_exporter/apcupsd_exporter
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target

Enable and start:

sudo systemctl daemon-reload
sudo systemctl enable --now apcupsd_exporter
sudo systemctl status apcupsd_exporter --no-pager

5. Verify metrics endpoint

curl -s http://localhost:9162/metrics | grep -i apc

6. Add Prometheus scrape config

- job_name: 'apcupsd'
  scrape_interval: 60s
  static_configs:
    - targets:
        - your-server-name-or-ip:9162

After reloading Prometheus, you should see UPS metrics being scraped from the new host.

If you are also using Grafana, you can reuse the dashboard approach from my apcupsd dashboard post.

Closing thoughts

I have mixed feelings about copying/forking the original projects. I settled on the fact that the original code is MIT open source and many others have already forked the project. Since it is so important to my homelab, I would rather keep a close eye on this software.

New disclaimer: I used an LLM to help create this post. Opinions expressed are likely from me and not the LLM.

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