When a new version of the Nagios Plugins is released, upgrading it is almost identical to installing it from scratch except the pre-requisites are usually already done. These steps show you how to upgrade Nagios Plugins on CentOS 6.5.

Nagios Plugins Installation instructions are located here:

https://support.nagios.com/kb/article.php?id=569

Download Nagios Plugins

• Type cd /tmp and press Enter
• Type wget http://nagios-plugins.org/download/nagios-plugins-2.1.1.tar.gz and press Enter
• Wait while the file is downloaded

Upgrade Nagios Plugins

The following steps will upgrade Nagios Plugins to 2.1.1.

• Type tar zxf nagios-plugins-2.1.1.tar.gz and press Enter
• Type cd nagios-plugins-2.1.1 and press Enter
• Type ./configure --with-nagios-user=nagios --with-nagios-group=nagios and press Enter
• Wait for the configure command to complete
• Type make and press Enter
• Wait for the make command to complete
• Type make install and press Enter
• Wait for the make install command to complete

This completes upgrading the Nagios Plugins. You can determine the version by execiting one of the plugins using the version argument:

Command:
/usr/local/nagios/libexec/check_by_ssh -V

Output:
check_by_ssh v2.1.1 (nagios-plugins 2.1.1)