Getting Started

This tutorial walks you through installing Munin, seeing your first graph, and understanding what happened. It takes about 5 minutes.

Note

This guide assumes a Debian/Ubuntu system. For other distributions, substitute yum or dnf for apt-get. The concepts are the same.

Prerequisites

You need two machines (or one machine acting as both master and node):

  • Master: collects data and serves the web interface.

  • Node: the machine being monitored (runs a small agent).

Both need network connectivity on TCP port 4949 (node) and 4948 (web interface).

Step 1: Install the Packages

On the node (the machine to monitor):

sudo apt-get install munin-node

On the master (the machine that collects data):

sudo apt-get install munin

This installs everything: the master, the web interface, and a node so Munin can monitor itself.

Step 2: Allow the Master to Query the Node

Edit /etc/munin/munin-node.conf on the node. Add the master’s IP address to the access list:

allow ^127\.0\.0\.1$

Replace 127.0.0.1 with your master’s actual IP if they are on different machines. Then restart the node:

sudo systemctl restart munin-node

Step 3: Tell the Master About the Node

Edit /etc/munin/munin.conf on the master. Add a section for the node you want to monitor:

[myserver.example.com]
  address 127.0.0.1

Use the node’s hostname or IP address. If you are monitoring the master itself, 127.0.0.1 is correct.

Step 4: Wait for the First Data Collection

Munin collects data every 5 minutes via cron. After installation, munin-cron is already set up. Wait 5 minutes, or run it manually to speed things up:

sudo -u munin /usr/share/munin/munin-cron

Step 5: View Your First Graph

Open a web browser and go to:

http://localhost:4948/

You should see the Munin web interface with graphs for your machine. Click on a host name, then a category (like “system”), then a service (like “load”) to see a graph.

What Just Happened?

Here is what each component did:

  1. munin-node (on the node) listened on port 4949 and waited for connections from the master.

  2. munin-update (on the master) connected to the node, asked for a list of plugins, and ran each one to collect data. The data was stored in RRD files under /var/lib/munin/.

  3. munin-limits (on the master) checked the collected data against warning and critical thresholds.

  4. munin-httpd (on the master) served the web interface on port 4948, generating graphs from the RRD files on demand.

Understanding the Plugin System

Munin’s power comes from its plugins. Each plugin is a small script that knows how to collect one type of data (CPU load, disk usage, network traffic, etc.).

You can see which plugins are active on a node by connecting to it:

nc localhost 4949

Then type:

list

You will get a list of plugin names like cpu, load, df, if_, and so on.

To see what a plugin outputs, use munin-run:

sudo munin-run load

This prints the current values:

load.value 0.42

To see the plugin’s configuration (graph title, labels, thresholds):

sudo munin-run load config

Next Steps