"Munin the monitoring tool surveys all your computers and remembers what it saw. It presents all the information in graphs through a web interface. Its emphasis is on plug and play capabilities. After completing a installation a high number of monitoring plugins will be playing with no more effort.
Using Munin you can easily monitor the performance of your computers, networks, SANs, applications, weather measurements and whatever comes to mind. It makes it easy to determine "what's different today" when a performance problem crops up. It makes it easy to see how you're doing capacity-wise on any resources.
Munin uses the excellent RRDTool (written by Tobi Oetiker) and the framework is written in Perl, while plugins may be written in any language. Munin has a master/node architecture in which the master connects to all the nodes at regular intervals and asks them for data. It then stores the data in RRD files, and (if needed) updates the graphs. One of the main goals has been ease of creating new plugins (graphs). " Munin
Simply put, munin allows you to make graphs about system statistics. See a running munin example
Munin relies on a client-server model. The client is munin-node, and the server is munin (refered to "munin-master" in the documentation).
You will only need to install munin-master on a single machine. But munin-node will need to be installed on all machines you wish to monitor. This article will focus on a single machine installation. Further documentation may be found on the munin documentation wiki.
Currently there's a munin (munin-master) and a munin-node package in extra.
# pacman -S munin munin-node
Installing optional web server
The following guide sets up munin to generate static html and graph images and write them in a directory of your choosing. You can view these generated files locally with any web browser. If you want to view the generated files from a remote machine then you want to install one of the following web servers.
Or one of the others from the web server category.
Add the daemon to /etc/rc.conf:
DAEMONS=(syslog-ng network netfs crond httpd munin-node)
Create a directory where the munin-master will write the generated html and graphs. The munin user must have write permission to this directory.
/srv/http/munin is used below so the generated output can be viewed at the following url  provided a web server is installed and running.
# mkdir /srv/http/munin # chown munin:munin /srv/http/munin
Uncomment the htmldir entry in /etc/munin.conf and change it to the directory created in the previous step:
Run the following to have munin collect data and update the generated html and graphs every 5 minutes:
# crontab /etc/munin/munin-cron-entry -u munin
You can run also run monin-cron manually for testing purposes.
# su - munin --shell=/bin/bash $ munin-cron
Testing the Installation
Start the services:
#/etc/rc.d/httpd start #/etc/rc.d/munin-node start
Then test the interface by pointing your browser to http://localhost/munin
There are many munin plugins (and they're easy to write). You can start looking for plugins on the munin exchange.
Basically all plugins are installed in the following manner (although there are exceptions, review each plugin!):
Download a plugin, then copy or move it to /usr/lib/munin/plugins
cp <plugin> /usr/lib/munin/plugins/
Now link the plugin to /etc/munin/plugins
ln -s /usr/lib/munin/plugins/<plugin> /etc/munin/plugins/<plugin>
Test your plugin, you do not need to use the full path to the plugin, munin-run should be able to figure it out.
Now restart munin-node
Then refresh the web page, there should be no need to restart munin-master.
If you want to remove a plugin, simply delete the linked file in /etc/munin/plugins/ no need to actually remove the plugin from /usr. Many scripts also follow the following naming convention <plugin>_<device>. This allows multiple links to a single plugin.