Everything missing but one host.

[questrad]

Installed Version: 2014R2.0
Red Hat Enterprise Linux Server release 6.5 (Santiago)

So today when I went to review my environment in NagiosXI (Note: With various accounts admin/nonadmin), and all I could see was one host and thousands missing . After reviewing the alerts in my inbox and viewing /usr/local/nagios/var/objects.cache I felt like it was safe to apply config. After that was done everything came back .

Could you help us understand the following

1- What went wrong and how to prevent this from happening again.
2- Tell me where I can find the backup logs

[lmiltchev]

1- What went wrong and how to prevent this from happening again.

Is the MySQL database offloaded to a remote server? Could nagios connect to MySQL when this happened? It is hard to say what really happened. Have you searched logs for clues?

2- Tell me where I can find the backup logs

You can look in "/usr/local/nagiosxi/var/dbmaint.log".
This file logs the result of the database maintenance cron. This should include table truncates and db backups.