Munin: Why Isn’t My Graph For My New Plugin Showing!?!
Munin is a really nice light weight record keeper for pretty much anything. It stores the values of anything and generates graphs for those values and leaves interpretation up to us (the viewer). It’s primarily designed for server monitoring and it’s great because the abstractness of the program allows us to monitor hardware, software, and user activity as well as anything else we can think of !
The trick is that we have to write a plugin for Munin to understand what we want it to do. I haven’t actually written any myself, but I have modified others to tweak what they do. I installed an iostat plugin for Munin FreeBSD (it doesn’t come with one in FBSD for the iostat) but was having a hard time getting it to work. It worked on the command line and all but it wouldn’t show the graph. Yes I had restarted the node program but it still wasn’t showing up. I even went to the point of upgrading my munin-node on the server.
The problem? The iostat plugin was not owned by root:wheel and set to 755. I.e. the permissions were wrong and it was not executable. Munin appears to run ./plugin rather than $PERL ./plugin. A little annoying as long as you know about this; a lot annoying if you don’t! Changing the persmissions resulted in it showing up on the graph after 2 polling cycles.