Nagios 4 - Monitor Server and Remote Client Configuration

Install NRPE v3 to Remote Client

cd /tmp
wget --no-check-certificate -O nrpe.tar.gz https://github.com/NagiosEnterprises/nrpe/archive/nrpe-3.2.1.tar.gz
tar xzf nrpe.tar.gz
cd /tmp/nrpe-nrpe-3.2.1/
./configure --enable-command-args
make all
make install
make install-config
echo >> /etc/services
echo '# Nagios services' >> /etc/services
echo 'nrpe    5666/tcp' >> /etc/services
make install-init
nano /usr/local/nagios/etc/nrpe.cfg
allowed_hosts=127.0.0.1,192.168.xx.xx

service nrpe start
/usr/local/nagios/libexec/check_nrpe -H 127.0.0.1


How to fix Nagios NRPE: Unable to read output issue
apt-get install nagios-plugins
cp /usr/lib/nagios/plugins/check_* /usr/local/nagios/libexec

Download  memory monitor tool to Remote Client
cd /usr/lib/nagios/plugins/
wget https://raw.githubusercontent.com/justintime/nagios-plugins/master/check_mem/check_mem.pl
mv check_mem.pl check_mem
chmod +x check_mem
./check_mem -f -w 20 -c 10

How to set and add commands to remote nrpe client
nano /usr/local/nagios/etc/nrpe.cfg

Find Default Commands
command[check_users]=/usr/local/nagios/libexec/check_users -w 5 -c 10
command[check_load]=/usr/local/nagios/libexec/check_load -r -w .15,.10,.05 -c .30,.25,.20
command[check_sda1]=/usr/local/nagios/libexec/check_disk -w 20% -c 10% -p /dev/sda1
command[check_zombie_procs]=/usr/local/nagios/libexec/check_procs -w 5 -c 10 -s Z
command[check_total_procs]=/usr/local/nagios/libexec/check_procs -w 150 -c 200
Add your Commands
command[check_cpu]=/usr/local/nagios/libexec/check_load -r -w .001,.002,.003 -c .004,.005,.006
command[check_mem]=/usr/local/nagios/libexec/check_mem -f -w 51 -c 50
command[check_disk]=/usr/local/nagios/libexec/check_disk  -w 99% -c 90% -p /dev/mapper/openfire402--vg-root
command[check_swap]=/usr/local/nagios/libexec/check_swap -w 20% -c 10%

service nrpe restart

How to set and add commands to Monitor Server
nano /usr/local/nagios/etc/servers/client.cfg

define host{
use                             linux-server
host_name                       Openfire402
alias                           server
address                         192.168.0.102
max_check_attempts              5
check_period                    24x7
notification_interval           30
notification_period             24x7
}
define service {
        use                             generic-service
        host_name                       Openfire402
        service_description             SSH
        check_command                   check_ssh
        notifications_enabled           1
        }
define service {
        use                             generic-service
        host_name                       Openfire402
        service_description             PING
        check_command                   check_ping!100.0,20%!500.0,60%
        notifications_enabled           1
        }
define service {
        use                             generic-service
        host_name                       Openfire402
        service_description             CPU
        check_command                   check_nrpe!check_cpu
        notifications_enabled           1
        }
define service {
        use                             generic-service
        host_name                       Openfire402
        service_description             RAM
        check_command                   check_nrpe!check_mem
        notifications_enabled           1
        }
define service {
        use                             generic-service
        host_name                       Openfire402
        service_description             Disk
        check_command                   check_nrpe!check_disk
        notifications_enabled           1
        }
define service {
        use                             generic-service
        host_name                       Openfire402
        service_description             Swap
        check_command                   check_nrpe!check_swap
        notifications_enabled           1
        }

Install SSL and SendEmail package
apt-get install libio-socket-ssl-perl libnet-ssleay-perl perl
apt-get install sendemail
touch /var/log/sendemail
chmod 666 /var/log/sendemail

Set SMTP AUTHENTICATION
nano /usr/local/nagios/etc/resource.cfg
$USER5$=xxx@gmail.com
$USER6$=smtp.gmail.com:587
$USER7$=username
$USER8$=password

Back up and modify email command
cd /usr/local/nagios/etc/objects/
cp commands.cfg commands-old.cfg
nano commands.cfg

# 'notify-host-by-email' command definition
define command{
        command_name notify-host-by-email
        command_line /usr/bin/printf "%b" "***** Nagios *****\n\nNotification Type: $NOTIFICATIONTYPE$\nHost: $HOSTNAME$\nState: $HOSTSTATE$\nAddress: $HOSTADDRESS$\nInfo: $HOSTOUTPUT$\n\nDate/Time: $LONGDATETIME$\n" | /usr/bin/sendemail -s $USER6$ -xu $USER7$ -xp $USER8$ -t $CONTACTEMAIL$ -f $USER5$ -l /var/log/sendemail -u "** $NOTIFICATIONTYPE$ Host Alert: $HOSTNAME$ is $HOSTSTATE$ **" -m "***** Nagios *****\n\nNotification Type: $NOTIFICATIONTYPE$\nHost: $HOSTNAME$\nState: $HOSTSTATE$\nAddress: $HOSTADDRESS$\nInfo: $HOSTOUTPUT$\n\nDate/Time: $LONGDATETIME$\n"
        }

# 'notify-service-by-email' command definition
define command{
        command_name notify-service-by-email
        command_line /usr/bin/printf "%b" "***** Nagios *****\n\nNotification Type: $NOTIFICATIONTYPE$\n\nService: $SERVICEDESC$\nHost: $HOSTALIAS$\nAddress: $HOSTADDRESS$\nState: $SERVICESTATE$\n\nDate/Time: $LONGDATETIME$\n\nAdditional Info:\n\n$SERVICEOUTPUT$" | /usr/bin/sendemail -s $USER6$ -xu $USER7$ -xp $USER8$ -t $CONTACTEMAIL$ -f $USER5$ -l /var/log/sendemail -u "** $NOTIFICATIONTYPE$ Service Alert: $HOSTALIAS$/$SERVICEDESC$ is $SERVICESTATE$ **" -m "***** Nagios *****\n\nNotification Type: $NOTIFICATIONTYPE$\n\nService: $SERVICEDESC$\nHost: $HOSTALIAS$\nAddress: $HOSTADDRESS$\nState: $SERVICESTATE$\n\nDate/Time: $LONGDATETIME$\n\nAdditional Info:\n\n$SERVICEOUTPUT$"
        }