Assumption: You will access munin using the server IP adress http://123.123.123.123/munin
(there are several ways to setup and access munin, but in a VirtualHost environment it may not be desirable to setup/access via a VirtualHost.)
sudo apt-get install munin munin-node
sudo vi /etc/munin/apache.conf
Allow from localhost 127.0.0.0/8 ::1
# Replace with this
Allow from all
# add this line just above the following lines
AllowOverride None
# uncomment these lines
AuthUserFile /etc/munin/munin-htpasswd
AuthName “Munin”
AuthType Basic
require valid-user
Set the login user Munin password
sudo htpasswd -c /etc/munin/munin-htpasswd Munin
Change the permissions (very important or you will get a 500 error – and no other How To for Ubuntu points this out)
sudo chmod 644 /etc/munin/munin-htpasswd
Change the Node IP to the server IP address
sudo vi /etc/munin/munin-node.conf
allow ^127\.0\.0\.1$
# Replace this with the server IP address
allow ^123\.123\.123\.123$
sudo service apache2 restart
sudo service munin-node restart
You should be good to go!
In your browser got to http://123.123.123.123/munin
User is Munin