Oops!! Frustrated with Nagios check_disk permission denied error?

Errors with monitoring systems like Nagios are critical and need an immediate fix.

This error occurs due to many reasons like permission restrictions for root, incorrect Nagios configuration and so on.

At Bobcares, we often get requests to fix Nagios errors, as a part of our Server Management Services.

Today, let’s see how our Support Engineers fix Nagios check_disk permission denied error for customers.

A quick look on Nagios

Nagios is a “plugin”-based approach for monitoring systems, networks, and infrastructure.

Also, it monitors the server and troubleshoots server performance errors. Overall, it comes as a handy tool in keeping an eye on the server 24×7.

However, while dealing with Nagios we may encounter many errors too. One such error is check_disk permission denied.

Reasons for Nagios check_disk permission denied error

The check_disk program is a part of the Nagios monitoring plugin. It is used for checking the disk status. Errors can happen here due to several reasons.

Today, we’ll discuss in detail on this and let’s see how our Engineers fix it.

1. Permission restrictions

A major reason for the Nagios check_disk permission denied error is permission restrictions for the root user on the selected directory on the disk.

The user that runs the Nagios service should have enough privileges on the directories. In many production servers, problems can creep in when the users lack sudo privileges.

Similarly, SELinux settings can also affect the working of Nagios.

In the nrpe command, our Dedicated Engineers add the sudo command. Thus, when the agent runs it, it will run it as root.

How do we verify permissions?

In one of the helpdesk requests, we handled a situation where the customer approached us with the below-shown check_disk error:

When checking in detail, we found that the problem was due to special permission set by FUSE on the .gvfs directory. It was restricting the root user from accessing the directory.

So we modified /etc/nagios2/conf.d/localhost_nagios2.cfg as:

/usr/lib/nagios/plugins/check_disk -w $ARG1$ -c $ARG2$ -u GB -A -i .gvfs

Finally, this fixed the error.

2. NRPE configuration settings

Nagios uses the NRPE aka Nagios Remote Plugin Executor to monitor remote server metrics like disk usage, CPU load, etc. And, the whole system works on the fact that Nagios allows you to remotely execute Nagios plugins.

Thus the NRPE configuration has a prominent role. Even if any of the options used in the Nagios command fails, it results in errors. For example, the Tracefs option can capture uniform traces for any file system, without modifying the file systems as such. If for any reason it fails, it can show up as errors.

How do we fix this error?

Recently, one of our customers approached us saying that he is getting an error like the one shown below.

Our Engineers checked in detail and did the following.

Firstly, we logged in to the client’s server.

Then, opened /etc/nagios/nrpe.cfg and searched for check_disk.

Next, we added –exclude-type=tracefs to check_disk as shown below:

[check_data]=/usr/lib/nagios/plugins/check_disk -e --exclude-type=tracefs

Finally, we restarted the service using:

/etc/init.d/nagios-nrpe-server restart

This fixed check_disk permission denied error.

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Conclusion

In short, the check_disk permission denied error in Nagios happens due to permission restrictions or incorrect Nagios configuration. Today, we saw how our Support Engineers fix this error.