Building My First Monitoring Setup with Prometheus on Ubuntu

Today I want to share what I learned about Prometheus and how it helps monitor systems and applications in real environments.

Prometheus is a popular open-source system for monitoring and alerting. It collects metrics, stores them as time-series data, and provides powerful tools to analyze and visualize performance. In this article, I explain how to install Prometheus on Ubuntu step by step.

What is Prometheus

Prometheus is a monitoring tool that collects metrics from systems and applications. It saves data as time series and helps you check performance, create alerts, and find issues.

Main features:

• Stores data in its own time-series database
• Pulls metrics from defined targets
• Has a query language (PromQL)
• Includes alerting and a built-in web interface

You can use it to monitor:

• Linux servers (CPU, memory, disk)
• Containers and Kubernetes clusters
• Databases, web apps, and APIs

System Requirements

Before you start:

• Ubuntu or Debian server
• Internet connection
• Port 9090 open for the web UI

Prometheus runs well with:

• 1–2 CPU cores
• 1–2 GB of RAM
• 10 GB or more disk space

Installation Steps

1. Create a Prometheus user and directories

It’s better not to run Prometheus as root. So I created a system user and folders:

sudo groupadd --system prometheus
sudo useradd --system -g prometheus prometheus
sudo mkdir -p /etc/prometheus /var/lib/prometheus

2. Download and extract Prometheus

Get the Linux AMD64 version from the official site:

wget https://github.com/prometheus/prometheus/releases/download/v3.5.0/prometheus-3.5.0.linux-amd64.tar.gz
tar xvf prometheus-3.5.0.linux-amd64.tar.gz
cd prometheus-3.5.0.linux-amd64

Move binaries:

sudo mv prometheus promtool /usr/local/bin/

3. Move configuration files

Prometheus comes with a default config file. Move it to the configuration folder:

sudo mv prometheus.yaml /etc/prometheus/

You can also create /etc/prometheus/web.yml if you plan to add authentication or HTTPS later.

4. Set correct permissions

Prometheus should own its directories:

sudo chown -R prometheus:prometheus /etc/prometheus /var/lib/prometheus

5. Create a systemd service file

This file lets Prometheus run in the background and start automatically on boot.

sudo vim /etc/systemd/system/prometheus.service

Paste this:

[Unit]
Description=Prometheus Service
Documentation=https://prometheus.io/docs/introduction/overview/
Wants=network-online.target
After=network-online.target

[Service]
Type=simple
User=prometheus
Group=prometheus
ExecReload=/bin/kill -HUP $MAINPID
ExecStart=/usr/local/bin/prometheus \
  --config.file=/etc/prometheus/prometheus.yaml \
  --storage.tsdb.path=/var/lib/prometheus \
  --web.config.file=/etc/prometheus/web.yml \
  --web.listen-address=0.0.0.0:9090
SyslogIdentifier=prometheus
Restart=on-failure
RestartSec=5s
LimitNOFILE=65536

[Install]
WantedBy=multi-user.target

Save and exit.

6. Start Prometheus

sudo systemctl daemon-reload
sudo systemctl enable --now prometheus

Check if it’s running:

sudo systemctl status prometheus

You should see active (running).

Verify the Installation

Open your browser and go to:

http://<your-server-ip>:9090

You’ll see the Prometheus web UI. In the query box, type up and click Execute. If you see a result with value 1, Prometheus is running and monitoring itself.

Basic Troubleshooting

• If the page doesn’t open, check your firewall: sudo ufw allow 9090/tcp
• To read logs: journalctl -u prometheus -n 50
• To restart: sudo systemctl restart prometheus

What I Learned

Setting up Prometheus manually helped me understand:

• How Linux services run with systemd
• Why non-root users improve security
• How configuration and data folders are organized
• The first steps of monitoring with PromQL

Now that Prometheus is running, I plan to add Node Exporter next to collect CPU, RAM, and disk metrics.

Adding Node Exporter for System Metrics

Now that Prometheus is installed, I added Node Exporter to collect server metrics like CPU, memory, and disk usage.

Step 1 – Download and Install Node Exporter

cd /tmp
wget https://github.com/prometheus/node_exporter/releases/download/v1.10.2/node_exporter-1.10.2.linux-amd64.tar.gz
tar xvf node_exporter-1.10.2.linux-amd64.tar.gz
cd node_exporter-1.10.2.linux-amd64
sudo mv node_exporter /usr/local/bin/

Create a system user for it:

sudo useradd --system node_exporter

Create a systemd service:

sudo vim /etc/systemd/system/node_exporter.service

Paste this:

[Unit]
Description=Node Exporter
After=network.target

[Service]
User=node_exporter
Group=node_exporter
Type=simple
ExecStart=/usr/local/bin/node_exporter
Restart=on-failure

[Install]
WantedBy=multi-user.target

Save and start it:

sudo systemctl daemon-reload
sudo systemctl enable --now node_exporter

Check the status:

sudo systemctl status node_exporter

If it’s running, open your browser:

http://<server-ip>:9100/metrics

You should see text data with many system metrics.

Step 2 – Add Node Exporter to prometheus.yaml

Now tell Prometheus to scrape data from Node Exporter.

Edit the file:

sudo vim /etc/prometheus/prometheus.yaml

Add this under scrape_configs:

global:
  scrape_interval: 15s

scrape_configs:
  - job_name: 'prometheus'
    static_configs:
      - targets: ['localhost:9090']

  - job_name: 'node_exporter'
    static_configs:
      - targets: ['localhost:9100']

Save and reload Prometheus:

sudo systemctl restart prometheus

Step 3 – Verify Node Exporter in Web UI

Go to:

http://<server-ip>:9090/targets

You should see two targets:

• prometheus
• node_exporter

Both should be in UP state. Now Prometheus collects metrics from your system through Node Exporter.

What I Learned

Through this setup I learned:

• How to install Prometheus and Node Exporter manually
• How systemd services work
• How to edit prometheus.yaml to add scrape targets
• How to verify metrics through the web interface