Installation and configuration for Nagios/Icinga

0) Prerequisites

  • Apache
  • PHP
  • GCC compiler
  • GD development libraries

You can use yum to install these packages by running the following commands (as root):

yum install httpd php
yum install gcc glibc glibc-common
yum install gd gd-devel
yum install libjpeg libjpeg-devel libpng libpng-devel
yum install net-snmp net-snmp-devel net-snmp-utils

You also might need these packages if you don’t have them yet:

yum install make
yum install openssl-devel

1) Create Account Information

Become the root user.

su -l

Create a new nagios/icinga user account and give it a password.

/usr/sbin/useradd -m nagios
passwd nagios

OR

/usr/sbin/useradd -m icinga
passwd icinga

Create a new nagcmd/icinga-cmd group for allowing external commands to be submitted through the web interface. Add both the nagios/icinga user and the apache user to the group.

/usr/sbin/groupadd nagcmd
/usr/sbin/usermod -a -G nagcmd nagios
/usr/sbin/usermod -a -G nagcmd apache

OR

/usr/sbin/groupadd icinga-cmd
/usr/sbin/usermod -a -G icinga-cmd icinga
/usr/sbin/usermod -a -G icinga-cmd apache

2) Add RPMforge repo

Find the appropriate rpmforge-release package for your distribution at http://repoforge.org/use/. For example, you can install it like:

rpm -ivh http://pkgs.repoforge.org/rpmforge-release/rpmforge-release-0.5.2-2.el6.rf.x86_64.rpm

3) Install Nagios/Icinga

yum install nagios

OR

yum install icinga icinga-gui

4) Customize Configuration

Edit the /etc/nagios/objects/contacts.cfg or /etc/icinga/objects/contacts.cfg config file with your favourite editor and change the email address associated with the icingaadmin contact definition to the address you’d like to use for receiving alerts.

5) Configure the Web Interface

Create a nagiosadmin/icingaadmin account for logging into the web interface. Remember the password you assign to this account - you’ll need it later.

htpasswd -c /etc/nagios/htpasswd.users nagiosadmin

OR

htpasswd -c /etc/icinga/htpasswd.users icingaadmin

Restart Apache to make the new settings take effect.

service httpd restart

6) Install the Nagios Plugins

For both Nagios and Icinga, you need to install Nagios plugins.

yum install nagios-plugins-all

7) Modify SELinux Settings

See if SELinux is in Enforcing mode.

getenforce

Put SELinux into Permissive mode.

setenforce 0

To make this change permanent, you’ll have to modify the settings in /etc/selinux/config and reboot.

8) Start Nagios/Icinga

Add Nagios/Icinga to the list of system services and have it automatically start when the system boots.

chkconfig --add nagios
chkconfig nagios on

OR

chkconfig --add icinga 
chkconfig icinga on

Verify the sample Nagios/Icinga configuration files.

/usr/bin/nagios -v /etc/nagios/nagios.cfg

OR

/usr/bin/icinga -v /etc/icinga/icinga.cfg

If there are no errors, start Nagios.

service nagios start

OR

service icinga start

9) Login to the Web Interface

You should now be able to access the web interface at the URL below. You’ll be prompted for the username (nagiosadmin/icingaadmin) and password you specified earlier.

http://localhost/nagios/ OR http://localhost/icinga/

Click on the “Service Detail” navbar link to see details of what’s being monitored on your local machine. It will take a few minutes to check all the services associated with your machine, as the checks are spread out over time.

Monitor Remote Linux Host using Nagios/Icinga

1. Install and configure Nagios Plugins and NRPE on the remote host

1) Create nagios account

useradd nagios
passwd nagios

2) Install nagios-plugin and nrpe

yum install nrpe
yum install nagios-plugins-all

3) Edit nrpe.cfg to allow your nagios/icinga server and customise configuration

Edit nrpe configuration file:

vi /etc/nagios/nrpe.cfg

Find line allowed_hosts . it is a comma separated list. add your nagios server ip to the list

allowed_hosts=127.0.0.1,192.168.1.100

For customised configuration, please see nrpe.cfg.

4) IPTables

If you are running iptables or a firewall between the server and host, make sure that the host is allowing port 5666 from the server’s IP address.

5) Start nrpe service on system start up

chkconfig nrpe on

6) Start nrpe service

service nrpe start

2. Configure on the monitoring server to monitor remote host

1) Install nrpe

yum install nrpe

2) Check check_nrpe on the monitoring server

Verify whether monitoring server can talk to the remotehost. For example:

/usr/lib64/nagios/plugins/check_nrpe -H 192.168.1.3
NRPE v2.13

3) Create host and service definition for remotehost

Create a new configuration file /etc/nagios/objects/remotehost.cfg OR /etc/icinga/objects/remotehost.cfg to define the host and service definition for this particular remotehost.

For more details, please see scilinux2.cfg.

4) Restart the nagios/Icinga service

service nagios restart OR service Icinga restart

Examples of customising configuration

1. Check disk space on local host

# Define a service to check the disk space of the root partition
# on the local machine.
# Warning if < 25% free, critical if < 10% free space on partition.
define service{
        use                   local-service         ; Name of service template to use
        host_name             localhost
        service_description   Root Partition
        check_command         check_local_disk!25%!10%!/
        }

2. Check Apache on local host

# Define a service to check HTTP on the local machine.
define service{
        use                   local-service         ; Name of service template to use
        host_name             localhost
        service_description   HTTP
        check_command         check_http
        }

3. Check how many Apache processes are running on local host

1) Add check_daemons in /etc/nagios/objects/commands.cfg OR /etc/icinga/objects/commands.cfg

#check daemons
define command{
        command_name    check_daemons
        command_line    $USER1$/check_procs -c $ARG1$:$ARG2$ -C $ARG3$
        }

2) Add service in /etc/nagios/objects/localhost.cfg OR /etc/icinga/objects/localhost.cfg

# Define a service to check the number of currently running Apache procs
# on the local machine. Critical if the number is not in the range from 1 to 20

define service{
        use                    local-service         ; Name of service template to use
        host_name              localhost
        service_description    HTTP daemons
        check_command          check_daemons!1!20!httpd
        }

4. Check PostgreSQL on remote host

1) Add check_nrpe in /etc/nagios/objects/commands.cfg OR /etc/icinga/objects/commands.cfg on monitoring server

To check remote host, check_nrpe is essential.

Note: Make sure check_nrpe is in /usr/lib64/nagios/plugins($USER1$)

#check nrpe
define command{
        command_name    check_nrpe
        command_line    $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
        }

2) Add check_pgsql in /etc/nagios/nrpe.cfg on remote host

command[check_pgsql]=/usr/lib64/nagios/plugins/check_pgsql

3) Check check_pgsql on monitoring server

/usr/lib64/nagios/plugins/check_nrpe -H scilinux2 -c check_pgsql

If you see the error like:

CRITICAL - no connection to 'template1' (FATAL:  Ident authentication failed for user "nrpe")

Add user ‘nrpe’ on remote host.

su - postgres
createuser nrpe

4) Add service in /etc/nagios/objects/scilinux2.cfg OR /etc/icinga/objects/scilinux2.cfg

define service{
        use                    generic-service
        host_name              scilinux2
        service_description    check-pgsql
        check_command          check_nrpe!check_pgsql
        }

Note: All plugins in /usr/lib64/nagios/plugins, run them with -h for help. Fo example:

/usr/lib64/nagios/plugins/check_disk -h

References

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