In order for Nagios to be of any use to you, you're going to have to download and install some plugins.
Plugins are usually installed in the libexec/ directory of your Nagios installation (i.e. /usr/local/nagios/libexec).
Plugins are scripts or binaries which perform all the service and host checks that constitute monitoring. You can grab the latest release of the plugins from- http://www.nagios.org/download or http://sourceforge.net/projects/nagiosplug/
I downloaded the Plugin from here
For Installing Plugin
# tar xf nagios-plugins-1.4.2.tar
#./configure' to configure the package for your system.
Running `configure' takes awhile. While running, it prints some
messages telling which features it is checking for.
`make' to compile the package.
Optionally, type `make check' to run any self-tests that come with
`make install' to install the programs and any data files and
You can remove the program binaries and object files from the
source code directory by typing `make clean'. To also remove the
files that `configure' created (so you can compile the package for
a different kind of computer), type `make distclean'. There is
also a `make maintainer-clean' target, but that is intended mainly
for the package's developers. If you use it, you may have to get
all sorts of other programs in order to regenerate files that came
with the distribution.
Now the Installation of Plugin is completed !!!
After the Installation of Nagios-Plugin you will see a libexec directory created in /usr/local/nagios/
This will have all the necessary commands to check services.
For more options on those commands you can execute :
[root@mybox libexec]# ./check_http
check_http: Could not parse arguments
Usage: check_http -H
[-a auth] [-f
[-s string] [-l] [-r
[-P string] [-m