1 Introduction

1.1 Goals

• Install and configure Munin on the master host

1.2 Notes

• Commands preceded with "$" imply that you should execute the command as a general user - not as root.
• Commands preceded with "#" imply that you should be working as root.
• Commands with more specific command lines (e.g. "rtrX>" or "mysql>") imply that you are executing commands on remote equipment, or within another program.

2 Exercises

2.1 Installing Munin on the master node

Make sure you only do this on your master node.

Note that to be able to visualize the graphs/data collected by Munin on the master, you'll need to install apache2 (the web server) on your master host as well.

Let's do this now:

$ sudo apt-get install apache2 apache2-utils

This shouldn't take more than a few seconds. Test that the service is running by pointing your browser at http://hostN.ws.nsrc.org, where N is the number of your master host.

Note: apache2-utils is required for the htpasswd program to be installed.

$ sudo apt-get install munin

The list of packages to be installed is long! But don't worry, installation won't take long.

By default, installing the munin package, installs both the munin master process (which collects data) and the munin-node.

Run the following command to verify that munin-node is active on your master host:

$ ps ax | grep munin

You should see something similar:

 3997 ?        Ss     0:00 /usr/bin/perl -wT /usr/sbin/munin-node

2.2 Enable the provided Apache2 configuration directive for Munin

Included in Munin is a configuration file for Apache2. First, let's copy the file into Apache's configuration directory:

$ sudo cp /etc/munin/apache.conf /etc/apache2/conf-available/munin.conf

Let's modify the file, so we can access Munin from our web browser.

$ sudo editor /etc/apache2/conf-enabled/munin.conf

You will have to do the following changes multiple times.

Skip the first section which looks like this:

# Enable this for cgi-based templates
# Alias /munin-cgi/static /var/cache/munin/www/static
# ScriptAlias /munin-cgi /usr/lib/munin/cgi/munin-cgi-html
# <Location /munin-cgi>
#       Order allow,deny
#       Allow from all
#       AuthUserFile /etc/munin/munin-htpasswd
#       AuthName "Munin"
#       AuthType Basic
#       require valid-user
# </Location>

After this, every time you see this line:

        Allow from localhost 127.0.0.0/8 ::1

replace it with:

        Allow from all

Same thing for the user authentication. Every time you see:

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

replace it with:

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

(Remove the # in front)

Save the file and exit.

Now, to emable the configuration, run the following commands:

$ sudo a2enconf munin.conf

You should see:

Enabling conf munin.
To activate the new configuration, you need to run:
  service apache2 reload

As indicated, reload the apache2 configuration:

2.3 Create a user to allow access to the Munin web interface

We still need to create a user + password to allow access to the Munin web statistics. To do so:

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

This will create the sysadm user. When prompted, enter a password for the user. Please use the same password as for the sysadm user.

Now, point your browser to http://hostN.ws.nsrc.org/munin - N is the number of your master host.

You should be prompted for a user and password. The user is sysadm, and the password is the one you set just now.

You will be presented with the following screen:

Munin Main Screen

If you click on 'localhost.localdomain', you'll be able to navigate the following categories of statistics, for the host localhost (that is, the machine that munin is running on.

disk munin network processes system

Take a moment to browse these categories. It should be pretty clear what each of them stands for.

Q: Explore the munin category. Why do you think it is useful to have these statistics ?

2.4 Change the name of the local client

Let's make the names more meaningful - localhost.localdomain isn't very informative.

Edit the file /etc/munin/munin.conf:

$ sudo editor /etc/munin/munin.conf`

Most of the default values don't need to be touched, the Ubuntu package has reasonable settings.

Move down and fine the section:

[localhost.localdomain]
    address 127.0.0.1
    use_node_name yes

... replace localhost.localdomain with hostN.ws.nsrc.org, where N is the number of your master host.

Once this is done, save the file and exit.

Now, we just need to wait 5 minutes for munin to run again - Munin on the collector side doesn't run as a daemon (service) - it it called by cron from /etc/cron.d/munin, which in turns calls /usr/bin/munin-cron.

This is done every 5 minutes by default.

After this time has elapsed, navigate once more to http://hostN.ws.nsrc.org/munin, and you should notice that the name of the only host being monitored now reflects what we set it to.

Notice on the left menu, how Groups lists the domain for our workshop, ws.nsrc.org.