Nagios XI - Scheduled Downtime Not Working

Problem Description

When you attempt to scheduled downtime for a host or service the downtime never appears despite being informed it was successfully added.

In addition to this when you navigate to Home > Incident Management > Scheduled Downtime there are no entries.

This problem can be caused by the Nagios XI server being unable to resolve "localhost".

Diagnosing The Problem

Open an SSH session to your Nagios XI server and execute the following commands:

tail -f /var/log/httpd/error_log

Now go into the XI interface and attempt to schedule downtime for a host or service.

You receive output similar to the following:

[Tue Oct 11 13:49:55 2016] [error] [client 10.25.254.50] Couldn't resolve host 'localhost', referer: http://10.25.5.12/nagiosxi/includes/components/xicore/downtime.php?cmd=schedule&type=host
[Tue Oct 11 13:49:55 2016] [error] [client 10.25.254.50] Couldn't resolve host 'localhost', referer: http://10.25.5.12/nagiosxi/includes/components/xicore/downtime.php

You can see that the log file is complaining that it cannot resolve localhost.

If you execute the following command you can see the contents of the /etc/hosts file:

cat /etc/hosts

Here is the output:

127.0.0.1    localhost.localdomain    localhost.localdomain    localhost4    localhost4.localdomain4        xi-c6x-x64
::1    localhost.localdomain    localhost.localdomain    localhost6    localhost6.localdomain6        xi-c6x-x64

If you look at the output you can see that there are no "localhost" entries, there are similar entries but not one for "localhost".

Resolving The Problem

Edit your /etc/hosts file and make sure there are localhost entries. For example:

127.0.0.1    localhost.localdomain    localhost.localdomain    localhost4    localhost4.localdomain4    localhost    xi-c6x-x64
::1    localhost.localdomain    localhost.localdomain    localhost6    localhost6.localdomain6    localhost    xi-c6x-x64

The last step is to restart the Apache service using one of the commands below:

RHEL 7 | CentOS 7 | Oracle Linux 7

systemctl restart httpd.service

Debian | Ubuntu 16/18

systemctl restart apache2.service

Now go and schedule downtime, your problem should be resolved.

Final Thoughts

For any support related questions please visit the Nagios Support Forums at:

http://support.nagios.com/forum/