Today, I will present Munin, a tool to monitor various health measurement of a system (essentially resources).

This article is part of a series about remote administration of Linux-based server (actually some of the tool work on *BSD systems too). You can find all article pertaining to this series using the Tag remote-server-admin.

Munin – Server resources monitoring

Munin offers nice timeline graphs of many resources consumption.

Munin is known to work on Linux, FreeBSD, NetBSD, Solaris and even OpenWRT (a port exists).

Installation

Apache web server is not required, but it is an easy set-up to view the Munin graphs.

$ sudo apt-get install munin apache2-mpm-worker

Configuration

As simple as allowing Apache for remote connection for Munin configuration.

Note: if you add installed Apache before, you probably need to create the following symbolic link if it does not exist:
$ [ -h /etc/apache2/conf.d/munin ] || sudo ln -s /etc/munin/apache.conf /etc/apache2/conf.d/munin

Now we can edit the right Apache file:

$ sudo vi /etc/munin/apache.conf

And check that the allowable IP are as follows:

munin/www>
Order allow,deny
Allow from all
#Allow from localhost 127.0.0.0/8 ::1
Options None

Activating the new configuration

Apache needs to reload its configuration:

$ sudo service apache2 reload

Visualising Munin

Open your favorite web browser and go to the page http://IP/munin/ Example: http://192.168.1.2/munin/

This picture depict an example output of Munin graphical trends — Example of Munin resource trends

Advanced configuration

I did not go deep into the configuration of Munin or Apache. But I did the following changes which enhance the security, though I cannot tell if this is sufficient.

Munin configuration enhancement

Edit the file munin-node.conf.

$ sudo vi /etc/munin/munin-node.conf

And change the lines about the binding address to match localhost only (no remote connection allowed to the node):

# Which address to bind to;
# host *
host 127.0.0.1

Now restart Munin:

$ sudo service munin-node restart

Apache/Munin configuration enhancement

Edit the file Apache configuration file again. We are going to set user/passer access.

$ sudo vi /etc/munin/apache.conf

And uncomment a few more lines:

AuthUserFile /etc/munin/munin-htpasswd
AuthName "Munin"
AuthType Basic
require valid-user

It is necessary to create at least one user to gain access to Munin:

$ sudo htpasswd -c /etc/munin/munin-htpasswd munin

This command creates the file /etc/munin/munin-htpasswd and add a user ‘munin’, it will prompt you for a password for this new user.
To add extra users:

$ sudo htpasswd /etc/munin/munin-htpasswd huygens

Apache needs to reload its configuration:

$ sudo service apache2 reload