Munin
Munin is a networked resource monitoring tool that can help analyze resource trends and bottlenecks. Munin has a master/node architecture in which the master regularly fetches the data from the nodes and presents the information in graphs through a web interface. A default installation provides a lot of graphs with almost no work and new graphs can be easily created added as plugins.
You can check out OpenStreetMap's Munin install for an example.
Installation
Install the munin package on the master machine and munin-node on the devices that you whish to monitor.
You can also install them both on the same machine so that the master machine monitors itself.
Further documentation may be found on the Munin documentation wiki.
Configuration
Directories
Create a directory where the munin-master will write the generated HTML and graph images. The munin user must have write permission to this directory.
The following example uses /srv/http/munin, so the generated output can be viewed at http://localhost/munin/, provided that a web server is installed and running:
# mkdir /srv/http/munin # chown munin:munin /srv/http/munin
Uncomment the htmldir entry in /etc/munin/munin.conf and change it to the directory created in the previous step:
htmldir /srv/http/munin
crontab
Run the following to have Munin collect data and update the generated HTML and graph images every 5 minutes:
# crontab /etc/munin/munin-cron-entry -u munin
Configure the email server to send mails to the munin user. If using postfix, add the following:
/etc/postfix/aliases
munin: root
And run:
# newaliases
systemd timer
Instead of a cron job a systemd timer can be used.
This needs a service unit configuration:
/etc/systemd/system/munin-cron.service
[Unit] Description=Survey monitored computers After=network.target [Service] User=munin ExecStart=/usr/bin/munin-cron
And a timer unit configuration:
/etc/systemd/system/munin-cron.timer
[Unit] Description=Survey monitored computers every five minutes [Timer] OnCalendar=*-*-* *:00/5:00 [Install] WantedBy=multi-user.target
Now, reload systemd configuration, enable/start munin-cron.timer and verify that everything is working:
# journalctl --unit munin-cron.service # less /var/log/munin/munin-update.log
Permissions
When graph_strategy cgi is enabled in /etc/munin/munin.conf ensure the directory /var/lib/munin/cgi-tmp is owned by user and group so that the script is able to write the png files to this directory.
# chown munin: /var/lib/munin/cgi-tmp
Testing
Once is configured to run Munin will be ready to start generating graphs. Ensure the is running on each of the nodes. It may be useful to jump ahead to the #Munin node section and return here once the node are up and running.
Change to the user with the following su command, the / option is for specifiying the shell (in this case bash).
This needs to be done from root shell, since the user does not have a password:
# su -s /bin/bash munin
By runnning the command manually it will trigger the generation of HTML and graph images immediately without having to wait for the next cron run:
munin> munin-cron
If the munin logging is configured, the logs are usually found in . Watching the munin-update.log log in a seperate terminal after running the command can be helpful in diagnosing issues.
# tail -f /var/log/munin/munin-update.log
And finally test the interface by pointing your browser to the output directory or http://localhost/munin/.
Daemon
On the nodes, [[enable/start}} .
IPv6
For IPv6 support on munin-node, using:
Install:
Customization
Before running munin, you might want to setup the hostname of your system. In /etc/munin/munin.conf, the default hostname is . This can be altered to any preferred hostname. The hostname will be used to group and name the files in /var/lib/munin and further, used to group the html files and graphs in your selected munin-master directory.
Plugins
Run with the option to have Munin suggest plugins it thinks will work on your installation:
# munin-node-configure --suggest
If there is a suggestion for a plugin you want to use, follow that suggestion and run the command again. When you are satisfied with the plugins suggested by , run it with the option to have the plugins configured:
# munin-node-configure --shell | sh
Adding
Basically all plugins are added in the following manner (although there are exceptions, review each plugin!):
Download a plugin, then copy or move it to :
# cp plugin /usr/lib/munin/plugins/
Then link the plugin to :
# ln -s /usr/lib/munin/plugins/plugin /etc/munin/plugins/
<plugin>_<device> to be used on <device>. See the if_ plugin for an example.Now test your plugin. You do not need to use the full path to the plugin, should be able to figure it out:
# munin-run plugin
And restart . Finally, refresh the web page.
Additional plugins
There are many Munin plugins out there just waiting to be installed. The MuninExchange is an excellent place to start looking, and if you cannot find a plugin that does what you want it is easy to write your own. Have a look at Developing Plugins at the Munin documentation wiki to learn how.
Removing
If you want to remove a plugin, simply delete the linked file in - there is no need to remove the plugin from .
# rm /etc/munin/plugins/plugin
Debugging
If you come across a plugin that is not working as expected (for example giving you no output at all) it might be interesting to run it directly. Fortunately there is a way to do this. Following the instructions until here, you will for example notice, that the plugin gives no output at all, when enabled. In order to run the plugin directly:
# munin-run apache_accesses
The following error:
LWP::UserAgent not found at /etc/munin/plugins/apache_accesses line 86.
indicates that a perl function could not be found. To resolve the problem, install the missing library, in this case, .
Permissions
Because many plugins read log files, it is useful to add user into group:
# usermod -a -G log munin
Web server (optional)
This 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 will need to install and configure one of the following web servers:
Or one of the other servers found in the web server category.
Apache VirtualHost examples
Based on information found here:
- http://guide.munin-monitoring.org/en/stable-2.0/example/webserver/apache-virtualhost.html
- http://munin-monitoring.org/wiki/MuninConfigurationMasterCGIdead+link+2021-05-17 ⓘ
In the next major release of Munin, things will be much simpler. Check it out:
Basic static HTML
<VirtualHost *:80>
ServerName localhost
ServerAdmin root@localhost
DocumentRoot /srv/http/munin
ErrorLog /var/log/httpd/munin-error.log
CustomLog /var/log/httpd/munin-access.log combined
</VirtualHost>
Static HTML with DynaZoom feature
Install .
You must enable one of these:
- (or if using mpm_prefork_module) by uncommenting the line in .
- Or install and add in .
<VirtualHost *:80>
ServerName localhost
ServerAdmin root@localhost
DocumentRoot /srv/http/munin
ErrorLog /var/log/httpd/munin-error.log
CustomLog /var/log/httpd/munin-access.log combined
# Rewrites
RewriteEngine On
# Images
RewriteRule ^/munin-cgi(.*) /usr/share/munin/cgi/$1 [L]
# Ensure we can run (fast)cgi scripts
<Directory "/usr/share/munin/cgi">
Require all granted
Options +ExecCGI
<IfModule mod_fcgid.c>
SetHandler fcgid-script
</IfModule>
<IfModule !mod_fcgid.c>
SetHandler cgi-script
</IfModule>
</Directory>
</VirtualHost>
DynaZoom Permissions
When Munin cannot draw graphs and logs a similar message to check to make sure group permissions are set on /var/lib/munin/cgi-tmp/munin-cgi-graph/ so the directory has writeable group permissions such as drwxrwxr-x 3 munin http 4096 Aug 9 20:11 munin-cgi-graph.
If group permissions are not set, then
Full dynamic
Use this VirtualHost if you want to set and to . Page loads will take longer because all the HTML and PNG files will be dynamically generated, but the munin-cron run will take less time because it will not execute munin-html and munin-graph. This feature may become necessary for you if your master polls many nodes and the munin-cron risks taking more than 5 minutes.
Install .
You must enable one of these:
- (or if using mpm_prefork_module) by uncommenting the line in .
- Or install and add in .
<VirtualHost *:80>
ServerName localhost
ServerAdmin root@localhost
DocumentRoot /srv/http/munin
ErrorLog /var/log/httpd/munin-error.log
CustomLog /var/log/httpd/munin-access.log combined
# Rewrites
RewriteEngine On
# Static content in /static
RewriteRule ^/favicon.ico /etc/munin/static/favicon.ico [L]
RewriteRule ^/static/(.*) /etc/munin/static/$1 [L]
# HTML
RewriteCond %{REQUEST_URI} .html$ [or]
RewriteCond %{REQUEST_URI} =/
RewriteRule ^/(.*) /usr/share/munin/cgi/munin-cgi-html/$1 [L]
# Images
RewriteRule ^/munin-cgi(.*) /usr/share/munin/cgi/$1 [L]
<Directory "/etc/munin/static">
Require all granted
</Directory>
# Ensure we can run (fast)cgi scripts
<Directory "/usr/share/munin/cgi">
Require all granted
Options +ExecCGI
<IfModule mod_fcgid.c>
SetHandler fcgid-script
</IfModule>
<IfModule !mod_fcgid.c>
SetHandler cgi-script
</IfModule>
</Directory>
</VirtualHost>
Munin 2.0.x
This example Nginx setup is based on a Munin 2.0.x master installation. It requires FastCGI and uses the and graph_strategy cgi in the munin.conf configuration.
Install the , and packages on the Munin-Master.
As we will be using the cgi strategy the systemd socket files need to be enabled. So the /run/munin/fcgi-graph.sock and sockets are created for the Nginx FastCGI configuration to hook into.
Enable/start and .
Create the munin vhost configuration file
Then restart the webserver ().
If all goes well, point your browser to your host http://yourhost.example.com/munin/ and you should see the Munin Overview page.
Munin 2.1.x
Although Munin 2.1.x versions are not yet available in the Arch repository. It is worth mentioning that the 2.1.x series will no longer use FastCGI and will be replaced with munin-httpd This page already contains an example configuration.
Tips and Tricks
MySQL
The MySQL plugin has extra dependencies: , perl-dbd-mysql, , and
Additionally it is recommended to access the database through a separate MySQL user. To make another user via the following MySQL commands:
To configure Munin to use this new user, create:
S.M.A.R.T.
To enable monitoring of S.M.A.R.T. data, install the package, and use:
/etc/munin/plugin-conf.d/munin-node
[smart_*]
user root
group disk
Then create the appropriate symlink for each disk to be monitored. As an example for :
lm_sensors
Install and configure according to lm_sensors#Setup. Assuming all goes correctly, create some symlinks:
# ln -s /usr/lib/munin/plugins/sensors_ /etc/munin/plugins/sensors_fan # ln -s /usr/lib/munin/plugins/sensors_ /etc/munin/plugins/sensors_temp # ln -s /usr/lib/munin/plugins/sensors_ /etc/munin/plugins/sensors_volt