Prerequriments:
* 2 ubuntu 20.04 servers i.e for nagios & client with root login enabled
Step 1: update the repository
sudo apt update
Step 2: Enable root login
sudo sed -i 's/#PermitRootLogin prohibit-password/PermitRootLogin yes/' /etc/ssh/sshd_config
sudo systemctl restart ssh
sudo passwd #change the root password if necessay
reboot
Step 3: install dependent packages
ssh root@ip-addr
apt install -y autoconf bc gawk dc build-essential gcc libc6 make wget unzip apache2 php libapache2-mod-php libgd-dev libmcrypt-dev make libssl-dev snmp libnet-snmp-perl gettext
Step 4: download and extract nagios core
cd ~/
wget https://github.com/NagiosEnterprises/nagioscore/archive/nagios-4.4.6.tar.gz
tar -xf nagios-4.4.6.tar.gz
cd nagioscore-*/
Step 5: compile and install nagios
./configure --with-httpd-conf=/etc/apache2/sites-enabled
make all
Step 6: create nagios user, group & add the “www-data” apache user to nagios group
make install-groups-users
usermod -a -G nagios www-data
Step 7:Install nagios binaries, service daemon & command mode script
make install
make install-daemoninit
make install-commandmode
Step 8: Then,install sample script configuration
make install-config
Step 9: Now install the Apache configuration for Nagios and enact the mod_rewrite and mode_cgi modules.
make install-webconf
a2enmod rewrite cgi
Step 10:Now restart the Apache service.
systemctl restart apache2
Step 11: Create nagiosadmin user
htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
Note: now it will ask for a password for accessing the nagios dashboard.
Step 12: setup firewall rules to allow apache and nagios server port to firewall
for svc in Apache ssh
do
ufw allow $svc
done
Then, re-start the firewall service
ufw enable
Note :Type ‘y’ to activate the firewall service
ufw status numbered
Note : Both the ssh & apache service is added to firewall
Step 13 : Installing Nagios Plugins and NRPE Plugin
apt install monitoring-plugins nagios-nrpe-plugin
After the installation, go to “/usr/local/nagios/etc” and create a directory for all server hosts configuration
cd /usr/local/nagios/etc
mkdir -p /usr/local/nagios/etc/servers
Step 14: edit nagios config file “nagios.cfg”
nano nagios.cfg
In the config file uncomment the “cfg_dir”
cfg_dir=/usr/local/nagios/etc/servers
Step 15: edit “resource.cfg” file, by changing default configuration as
nano resource.cfg
$USER1$=/usr/lib/nagios/plugins
Step 16: Edit “object/contacts.cfg” , by adding mail addresses
nano object/contacts.cfg
define contact{
......
email email@host.com
}
Step 17: Edit “object/commands.cfg” , by adding the following lines at the end of file
nano object/commands.cfg
define command{
command_name check_nrpe
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
}
Note: All the basic nagios config has been completed
Step 18: Restart the nagios
systemctl start nagios
systemctl enable nagios
systemctl status nagios
Step 19: Restart apache server
systemctl restart apache2
Now, Open the browser and type the following url
http://ip-address/nagios (http://192.168.0.196/nagios)
Login in with the user “nagiosadmin” and type the password, a prompt will appear
Dashboard will be like:
Now Add Host to Monitor
Step 20: Install NRPE Server on client machine
ssh root@ip-addr
apt update
apt install nagios-nrpe-server monitoring-plugins
Step 21: go to the directory "/etc/nagios" and edit he config file "nrpe.cfg"
cd /etc/nagios
nano nrpe.cfg
Change the following
uncomment the "server_address" and add client address
server_address=192.168.0.197
allowed_hosts=127.0.0.1,::1,192.168.0.196
now edit "nrpe_local.cfg" config file in client machine
nano nrpe_local.cfg
change the ip addr with client machine ip addr, and paste the configuration in the file
command[check_root]=/usr/lib/nagios/plugins/check_disk -w 20% -c 10% -p /
command[check_ping]=/usr/lib/nagios/plugins/check_ping -H 192.168.0.197 -w 100.0,20% -c 500.0,60% -p 5
command[check_ssh]=/usr/lib/nagios/plugins/check_ssh -4 192.168.0.197
command[check_http]=/usr/lib/nagios/plugins/check_http -I 192.168.0.197
command[check_apt]=/usr/lib/nagios/plugins/check_apt
Now restart the nagios NRPE services
systemctl restart nagios-nrpe-server
systemctl enable nagios-nrpe-server
Check the NRPE server is up & running
systemctl status nagios-nrpe-server
Check Nagios & NRPE server in client
/usr/lib/nagios/plugins/check_nrpe -H 192.168.0.197
/usr/lib/nagios/plugins/check_nrpe -H 192.168.0.197 -c check_ping
Step 22: Adding host configuration to nagios server
cd /usr/local/nagios/etc
nano servers/client01.cfg
ADD THIS LINES BY CHANGING NAME AND IP-ADDRESS OF CLIENT
# Ubuntu Host configuration file1
define host {
use linux-server
host_name client01
alias UBUNTU-HOST
address 192.168.0.197
register 1
}
define service {
host_name client01
service_description PING
check_command check_nrpe!check_ping
max_check_attempts 2
check_interval 2
retry_interval 2
check_period 24x7
check_freshness 1
contact_groups admins
notification_interval 2
notification_period 24x7
notifications_enabled 1
register 1
}
define service {
host_name client01
service_description Check Users
check_command check_nrpe!check_users
max_check_attempts 2
check_interval 2
retry_interval 2
check_period 24x7
check_freshness 1
contact_groups admins
notification_interval 2
notification_period 24x7
notifications_enabled 1
register 1
}
define service {
host_name client01
service_description Check SSH
check_command check_nrpe!check_ssh
max_check_attempts 2
check_interval 2
retry_interval 2
check_period 24x7
check_freshness 1
contact_groups admins
notification_interval 2
notification_period 24x7
notifications_enabled 1
register 1
}
define service {
host_name client01
service_description Check Root / Disk
check_command check_nrpe!check_root
max_check_attempts 2
check_interval 2
retry_interval 2
check_period 24x7
check_freshness 1
contact_groups admins
notification_interval 2
notification_period 24x7
notifications_enabled 1
register 1
}
define service {
host_name client01
service_description Check APT Update
check_command check_nrpe!check_apt
max_check_attempts 2
check_interval 2
retry_interval 2
check_period 24x7
check_freshness 1
contact_groups admins
notification_interval 2
notification_period 24x7
notifications_enabled 1
register 1
}
define service {
host_name client01
service_description Check HTTP
check_command check_nrpe!check_http
max_check_attempts 2
check_interval 2
retry_interval 2
check_period 24x7
check_freshness 1
contact_groups admins
notification_interval 2
notification_period 24x7
notifications_enabled 1
register 1
SAVE & EXIT
Now restart the Nagios Server
References:
https://www.howtoforge.com/tutorial/how-to-install-nagios-on-ubuntu-2004/
https://support.nagios.com/kb/index.php
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