Check_disk shows different value as performance data

Hello there.

Hopefully I chose the right forum for my issue.
We’re running the check_disk command on several hosts. The check gives a return value of free disk space and also performance data of used disk space. Both together don’t add up to 100%.

For an example look here:

You can see that there are 9% free disk space (which is correct - looking at df -h). It also shows that there are 85% of space occupied which adds up to 94%. We are using Grafana with InfluxDB to visualize stuff easier and since the value of used disk space equals the 85% the free value displayed in Grafana is off by a few percent.

Do I miss something obvious here? Is this supposed to look like this or did I run into a bug?

Kind regards


what’s the raw output of the plugin, if you execute it manually on the host itself?


Hi Michael,

the raw output is as follows:
DISK WARNING - free space: / 1933 MB (10% inode=72%);| /=17057MB;18027;19028;0;20030

I want to add that this does not only happen on this particular host but on all host we’re running check_disk on.


so 1933 is free space, 17057 is used. Sums up to 18990.

Maybe there’s something cached, or reserved. The plugin provides some options for that.

 -f, --freespace-ignore-reserved
    Don't account root-reserved blocks into freespace in perfdata


1 Like

That did the trick. Now it sums up to 100%. Thanks for your time.

You’re welcome. Whenever you find a reply helpful or as solution, please mark it as solved. This allows others to immediately see the solution and also, to filter search results. Thanks.