CentOS 5 Nagios Installation
This Nagios installation is based on Nagios installation guide found in CentOS site. These are the steps in that may help. This is just a basic setup please don't expect advance setup. To learn more please read Nagios documentation and for more examples please visit this internal Nagios link. The link is a general example on how to configure some advance feature in Nagios in any system provided that nagios is alread running. Just substitute to your own path.
Create RPM Forge repository
Open a terminal and do the following commands
[mylogin@hostname nagios]# wget http://apt.sw.be/redhat/el5/en/i386/rpmforge/RPMS/rpmforge-release-0.3.6-1.el5.rf.i386.rpm
[mylogin@hostname folder]# rpm -ivh rpmforge*
Note: you will need to check your Operating Systems Architecture before downloading the rpmforege package. Please check adding yum repository page for additional information.
Check if the repository is enabled. enabled must be equal to 1.
[mylogin@hostname nagios]# vi /etc/yum.repos.d/rpmforge.repo
Tip: Disable all added yum repository if the configuration is done. This will prevent future conflicts with some packages during base upgrade.
Install Nagios (Server Side)
[mylogin@hostname nagios]# yum install nagios nagios-plugins nagios-plugins-nrpe nagios-devel
Install Nagios (Client Side)
[mylogin@hostname nagios]# yum install nagios nagios-plugins nagios-plugins-nrpe nagios-devel nagios-nrpe
Nagios Configuration
Before starting any configuration make it a habit to backup all configuration files. This will save us a lot of time in troubleshooting. Having a backup will also allow us to restore the most recent configuration to the system. We can also make the backup configuration as a future reference in case we need something :)
[mylogin@hostname nagios]# cd /etc
[mylogin@hostname nagios]# cp -frp nagios nagios.backup-<date>
[mylogin@hostname nagios]# vi /etc/nagios/nagios.cfg
Be sure to add the following lines after cfg_file=/etc/nagios/objects/localhost.cfg
cfg_file=/etc/nagios/objects/contactgroups.cfg
cfg_file=/etc/nagios/objects/hostgroups.cfg
cfg_file=/etc/nagios/objects/hosts.cfg
cfg_file=/etc/nagios/objects/services.cfg
cfg_file=/etc/nagios/objects/escalations.cfg
Create Nagios configuration files
[mylogin@hostname nagios]# cd /etc/nagios/objects/
[mylogin@hostname nagios]# touch contactgroups.cfg hostgroups.cfg hosts.cfg services.cfg escalations.cfg
[mylogin@hostname nagios]# chown nagios:nagios contactgroups.cfg hostgroups.cfg hosts.cfg services.cfg escalations.cfg
[mylogin@hostname nagios]# mv localhost.cfg localhost.cfg_orig
Separating the configuration files of Nagios will allow easy administration because the configuration files of Nagios are group according to its functions.
Edit Nagios configuration file
[mylogin@hostname nagios]#vi /etc/nagios/nagios.cfg
comment cfg_file=/etc/nagios/objects/localhost.cfg with '#'
These are the contents of the configuration files:
contacts.cfg
[mylogin@hostname nagios]# vi /etc/nagios/objects/contacts.cfg
# Content of Nagios contacts.cfg
define contact{
contact_name nagiosadmin
use generic-contact
alias Nagios Admin
email admin-email-address
}
define contact{
contact_name pals
alias pals
use generic-contact
service_notification_period 24x7
host_notification_period 24x7
service_notification_options c,r
host_notification_options d,r
email pals@domain.com
}
define contact{
contact_name benjunne
alias benjunne
use generic-contact
service_notification_period workhours
host_notification_period workhours
service_notification_options c,r
host_notification_options d,r
email benjunne@domain.com
}
contactgroups.cfg
[mylogin@hostname nagios]# vi /etc/nagios/objects/contactgroups.cfg
# Content of contactgroups.cfg
# 'network-group' contact group definitions
define contactgroup{
contactgroup_name network-group
alias network-group
members pals,benjunne
}
# 'systems-database-group' contact group definitions
define contactgroup{
contactgroup_name systems-database-group
alias systems-database-group
members marlou,debbie
}
# 'technical-group' contact group definitions
define contactgroup{
contactgroup_name technical-group
alias technical-group
members dennis,arnel,steve
}
hosts.cfg
[mylogin@hostname nagios]# vi /etc/nagios/objects/hosts.cfg
# Contents of hosts.cfg
define host{
use linux-server
host_name localhost
alias localhost
address 127.0.0.1
}
# Production Server
define host{
use linux-server
host_name production-server
alias Production Server
address IP-ADDRESS
check_command check-host-alive
max_check_attempts 20
notification_interval 240
notification_period 24x7
notification_options d,u,r
}
# Test Server
define host{
use linux-server
host_name test-server
alias Test Server
address IP-ADDRESS
check_command check-host-alive
max_check_attempts 20
notification_interval 240
notification_period 24x7
notification_options d,u,r
}
hostgroups.cfg
[mylogin@hostname nagios]#vi /etc/nagios/objects/hostgroups.cfg
# Content of hostgroups.cfg still needs additional configuration
define hostgroup{
hostgroup_name linux-servers
alias Linux Servers
members localhost
}
services.cfg
[mylogin@hostname nagios]# vi /etc/nagios/objects/services.cfg
# Content of services.cfg
define service{
use local-service
host_name localhost
service_description PING
check_command check_ping!100.0,20%!500.0,60%
}
define service{
use local-service
host_name localhost
service_description Root Partition
check_command check_local_disk!20%!10%!/
}
define service{
use local-service
host_name localhost
service_description Current Users
check_command check_local_users!20!50
}
define service{
use local-service
host_name localhost
service_description Total Processes
check_command check_local_procs!250!400!RSZDT
}
define service{
use local-service
host_name localhost
service_description Current Load
check_command check_local_load!5.0,4.0,3.0!10.0,6.0,4.0
}
define service{
use local-service
host_name localhost
service_description Swap Usage
check_command check_local_swap!20!10
}
define service{
use local-service
host_name localhost
service_description SSH
check_command check_ssh
notifications_enabled 0
}
define service{
use local-service
host_name localhost
service_description HTTP
check_command check_http
notifications_enabled 0
}
# START PRODUCTION SERVER
define service{
use generic-service
host_name production-server
service_description HTTP
check_command check_http!-t 5 -p 8000
notifications_enabled 1
}
define service{
use generic-service
host_name production-server
service_description SSH
check_command check_ssh!-t 5 -r "OpenSSH_3.6.1p2" ; version match check
}
escalations.cfg
[mylogin@hostname nagios]# vi /etc/nagios/objects/escalations.cfg
# Content of escalations.cfg
define serviceescalation{
host_name production-server
service_description HTTP
first_notification 1
last_notification 0
notification_interval 30
contact_groups systems-database-group
}
Start Nagios
[mylogin@hostname nagios]# service nagios start
[mylogin@hostname nagios]# service nagios restart
[mylogin@hostname nagios]# service nrpe restart
[mylogin@hostname nagios]# chkconfig nagios on
[mylogin@hostname nagios]# chkconfig nrpe on
Troubleshooting Nagios
Below is a syntax that may help in trobleshooting nagios configuration error. It will produce a verbose output of the error message.
[mylogin@hostname nagios]# nagios -v /etc/nagios/nagios.cfg
Create Nagios user access.
This will ask you for your password. Please remember it. The command will also allow you to reset your password incase you forget.
[mylogin@hostname nagios]# htpasswd -c /etc/nagios/htpasswd.users nagiosadmin
Accessing Nagios
Open your favorite browser and point to Nagios Server
http://<your-nagios-server-domain-or-ip-address>/nagios/
This will propt a password. Please encode the user name nagiosadmin and the password that you entered.
