As I had some issues with my Linode server related to mistuned MariaDB settings, I was forced to find a way to monitor a Linux process, such as httpd, mysqld and php. Not only did I need to know if they were running, how many of them were running, but also their cpu and memory usage, so I could tune my Apache settings (located at /etc/httpd/conf/httpd.conf). I hoped to find a plugin which did all of the above, but couldn’t find one. The plugin that came closest to what I needed, was this one written bij Eli Keimig. 

As the last release date was 08/11/2010 and it missed some crucial features, I decided to make it better. At the moment I added the following features:

  • Performance data for Linux process CPU usage.
  • Performance data for Linux process Memory usage.
  • Added Linux process count with performance data.
  • Improved the plugin output.
  • Added minimum and maximum Linux process count.

How to monitor a Linux process?

The plugin uses ‘ps’ to retrieve the Linux process information. Logged in as root, type the following in your terminal to show active processes on the server:

The a option tells ps to list the processes of all users on the system rather than just those of the current user, with the exception of group leaders and processes not associated with a terminal. A group leader is the first member of a group of related processes.

The u option tells ps to provide detailed information about each process.

The x option adds to the list processes that have no controlling terminal, such as daemons, which are programs that are launched during boot and run unobtrusively in the background until they are activated by a particular event or condition.

As the list of processes can be quite long and occupy more than a single screen, the output of ps aux can be piped (transferred) to the less command, which lets it be viewed one screen full at a time. The output can be advanced one screen forward by pressing the SPACE bar and one screen backward by pressing the b key.

With the -C parameter you can specify the Linux process for which to show information.

And you can specify what specific information to show with the -o parameter:

After joining the results with paste and making the sum with bc, we get the result we want.

Check out this screenshot which shows information about the httpd, mysqld, nagios and php processes.

Linux process

This information can really help troubleshoot LAMP configuration issues. I haven’t got a lot of time to produce a decent post, but I’ll extend this post when I find some more time. As it’s a Bash script I’m guessing it doesn’t need to much explanation to get it working in Nagios.

Willem D'Haese
Expert Monitoring at Digipolis
Expert Monitoring with a demonstrated history of working in the information technology and services industry. Strong ICT skills such as monitoring, virtualization, automation.