Install Nagios3 on Ubuntu 13.10 VPS for monitoring virtual servers and services

In the following article we will guide you through the steps on how to install Nagios3 on a Ubuntu 13.10 VPS so you can monitor your virtual servers and services from your VPS.

Nagios3 is a robust and very powerful monitoring system which can help you monitor your virtual servers and the services running on your servers.

It is one of the best open-source monitoring systems out there.

Before proceeding any further, initiate a screen session by executing:

## screen -U -S nagios-screen

Then, make sure your Ubuntu 13.10 VPS is fully up-to-date by executing:

## apt-get update
## apt-get upgrade

If Apache2 is not installed on your vps, run the command below to install it:

## apt-get install apache2

Next thing to do, is to install Nagios and Nagios NRPE (Nagios Remote Plugin Executor) Plugins on your VPS by running:

## apt-get install nagios3 nagios-nrpe-plugin

you should be prompted to enter your nagiosadmin user’s password as shown below

if for some reason you’re not, then use the following command to set your nagiosadmin user’s password:

## htpasswd -c /etc/nagios3/htpasswd.users nagiosadmin

proceed with adding Apache’s www-data user to the nagios group:

## usermod -a -G nagios www-data

add executable bit for nagios group to everything under the /var/lib/nagios3/ directory:

## chmod -R g+x /var/lib/nagios3/

next, edit Nagios3 configuration file in /etc/nagios3/nagios.cfg and enable external commands by setting check_external_commands from 0 to 1:

## vim +/check_external_commands /etc/nagios3/nagios.cfg

restart Nagios and Apache and access your Nagios at http://your.hostname.com/nagios3

## service apache2 restart
## service nagios3 restart

Adding servers or services to nagios is done by creating a configuration file for a particular host. In this case, lets monitor a CentOS VPS (my.hostname.com) and some of the services running on it from your Nagios. So, create a configuration file for this VPS:

## cd /etc/nagios3/conf.d
## vim my.hostname.com.cfg

and add the following:

define host {
    use                      generic-host
    host_name                my.hostname.com
    alias                    host-cosini
    address                  XXX.XXX.XXX.XXX
}

define service {
    use                      generic-service
    host_name                my.hostname.com
    service_description      HTTP
    check_command            check_http
}

define service {
    use                      generic-service
    host_name                my.hostname.com
    service_description      SSH
    check_command            check_ssh!2219!
    notifications_enabled    0
}

define service {
    use                      generic-service
    host_name                my.hostname.com
    service_description      PING
    check_command            check_ping!100.0,20%!500.0,60%
}

define service {
    use                      generic-service
    host_name                my.hostname.com
    service_description      LOAD
    check_command            check_nrpe_1arg!check_load
}

define service {
    use                      generic-service
    host_name                my.hostname.com
    service_description      FTP
    check_command            check_nrpe_1arg!check_ftp
}

define service {
    use                      generic-service
    host_name                my.hostname.com
    service_description      DISK
    check_command            check_nrpe_1arg!check_storage
}

save and close the file and restart nagios3 for the changes to take effect:

## service nagios3 restart

access http://your.hostname.com/cgi-bin/nagios3/status.cgi?host=all
and see if the new server is shown in the interface.

In order to monitor some of the services running on our client CentOS 6 VPS, we need to install and configure NRPE on the server. To do that, first we need to enable the EPEL repository and install the packages by:

## rpm -Uvh http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
## yum install nrpe nagios-plugins-all

once installed, we need to configure NRPE by editing /etc/nagios/nrpe.cfg:

allowed_hosts=127.0.0.1
change to
allowed_hosts=127.0.0.1,XXX.XXX.XXX.XXX

where XXX.XXX.XXX.XXX is your Nagios VPS IP address

add/edit the following command:

command[check_ftp]=/usr/lib/nagios/plugins/check_procs -a proftpd
command[check_storage]=/usr/lib/nagios/plugins/check_disk -w 20% -c 10% -p /

enable NRPE on system start-up and start the service:

## chkconfig nrpe on
## service nrpe start

Of course, if you are one of our Linux VPS Hosting customers, you don’t have to do any of this, simply ask our admins, sit back and relax. Our admins will set this up for you immediately. For more updates, you can also read our guide on How to install Nagios3 and Check_MK on an Ubuntu 12.04 LTS VPS.

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