Why did Munin stop updating ?

Munin is a cPanel Plugin that displays information about CPU, Exim, Apache, MySQL usage, and other information, using rrdtool. If it fails to update, there is likely a permissions issue that is causing it.

First, check to make sure that cron is running, and that there is a crontab entry for Munin. Next, check /var/lib/munin and /var/log/munin. The files in both directories must be owned by munin:munin. If the files in /var/log/munin are not owned by munin:munin, the log files will be updated, but the graphs displayed by Munin will not be updated.

This permissions issue can be corrected by running the following commands as root:
chown -R munin:munin /var/log/munin
chown -R munin:munin /var/lib/munin

Now run Munin manually from the command line: sudo -u munin munin-cron

You should see entries added to /var/log/munin/munin-update, and no errors in the log file. Now refresh the Munin display in WHM. The graphs should be updated.

The weekly graphs may not be updated immediately. These will be updated at the appointed time configured in the crontab.