In many companies, nagios is the de-facto monitoring tool. Even with new modern alternatives solutions, this opensource project, still, has a large amount of implementations in place. This guide is based on a “clean/fresh” CentOS 6.9 virtual machine.
Epel
An official nagios repository exist in this address: https://repo.nagios.com/
I prefer to install nagios via the EPEL repository:
# yum -y install http://fedora-mirror01.rbc.ru/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
# yum info nagios | grep Version
Version ...Thank you.
What is the time?
Time offset is the amount of time that is off (or drift) from a specific value. In Linux systems, date is been calculating from the beginning of time. That is 00:00:00 1 January 1970 or as it called Unix Time and systems define date (time) as the number of seconds that have elapsed from 01.01.1970.
It is so important that even a few seconds off can cause tremendous disaster in data centers and applications.
Network Time
To avoid problems with time, systems must and should synchronize their time over the Internet every now and then. This is being done by asking a central NTP server via Network Time Protocol. The most common scenario for infrastructures is to have one or two NTP servers and then all the systems inside this infrastructure can synchronize their time from those machines.
Nagios - NRPE
In my case, I have a centralized NTP Daemon that...
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