The error is due to a bug in a Perl library Munin uses which causes $PATH variable to be lost, and then causes the plugin cannot find the mysqladmin program which it needs to retrieve the numbers to populate in the graphs. Uninstall and reinstall Munin Service Monitor may make it works again, however, a more permanent solution is to hardcode the path of the program, which will fix the problem. Here the guide on how to specify the path to mysqladmin to Munin.

Fix for Munin installed by cPanel/WHM

   1. Determine where is mysqladmin program located with the one of the following command:

      which mysqladmin
      type mysqladmin
      locate mysqladmin

      If should return a path to mysqladmin which looks similar or the same to /usr/bin/mysqladmin.

   2. Edit the /etc/munin/plugin-conf.d/cpanel.conf Munin configuration file, and modify the [mysql*] to look like below:
      [mysql*]
      user root
      group wheel
      env.mysqladmin /usr/bin/mysqladmin
      env.mysqlopts –defaults-extra-file=/root/.my.cnf

      Ensure the env.mysqladmin value is path returned by step above. Also ensure that /root/.my.cnf contains correct root password to the MySQL databases.

   3. Then restart Munin service:

      /etc/init.d/munin-node restart

   4. Wait a while for MySQL statistics to be gathered, and check the graphs again.