===== Upgrade Nagios =====
<code>
wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-x.y.z.tar.gz
tar xzf nagios-x.y.z.tar.gz
cd nagios-x.y.z
./configure
make all
make install
make install-init
make install-commandmode
systemctl daemon-reload
systemctl restart nagios
</code>

==== References ====
  * https://assets.nagios.com/downloads/nagioscore/docs/nagioscore/4/en/upgrading.html