Step‑by‑Step Guide to Installing and Configuring Nagios on CentOS 7

1. Prepare the virtual machine

Create a CentOS 7 VM with 2 CPU cores, 4 GB RAM, NAT networking, LSI Logic SCSI controller and a 50 GB virtual disk. Enable hardware virtualization (Intel VT‑x/EPT or AMD‑V/RVI) in the VM settings.

2. Configure the network interface

vi /etc/sysconfig/network-scripts/ifcfg-ens33

3. Pre‑installation configuration

YUM repository

cd /etc/yum.repos.d/
mv CentOS-Base.repo CentOS-Base.repo.bak
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
yum clean all
yum makecache
yum repolist

Verify external network access

ping www.baidu.com

4. Install Nagios Core (4.4.3)

Disable SELinux

setenforce 0
sed -i 's/SELINUX=.*/SELINUX=disabled/g' /etc/selinux/config
getenforce

Install prerequisite packages

yum install -y gcc glibc glibc-common wget unzip httpd php gd perl postfix

Download and extract the source

cd /tmp
wget -O nagioscore.tar.gz https://github.com/NagiosEnterprises/nagioscore/archive/nagios-4.4.3.tar.gz
tar zxvf nagioscore.tar.gz

Compile and install

cd nagioscore-nagios-4.4.3/
./configure
make all
make install
make install-daemoninit
make install-commandmode
make install-config
make install-webconf

Create Nagios user and group, add Apache user

make install -groups -users
usermod -a -G nagios apache

Configure firewall (allow HTTP port 80)

yum install -y iptables-services
systemctl enable iptables
iptables -I INPUT -p tcp --dport 80 -j ACCEPT
service iptables save
ip6tables -I INPUT -p tcp --dport 80 -j ACCEPT
service ip6tables save

Create web‑interface admin user

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

Start services

service httpd restart
service nagios restart

5. Install Nagios Plugins (2.2.1)

Enable EPEL repository

cd /tmp
wget https://archives.fedoraproject.org/pub/archive/epel/6/x86_64/epel-release-6-8.noarch.rpm
rpm -ivh epel-release-6-8.noarch.rpm
cd /etc/yum.repos.d/
mv epel.repo epel.repo.backup
mv epel-testing.repo epel-testing.repo.backup
wget -O epel.repo https://mirrors.aliyun.com/repo/epel-7.repo
sed -i 's|^#baseurl=|baseurl=|g' epel.repo
sed -i 's|^metalink|#metalink|g' epel.repo
yum clean all
yum makecache

Install build dependencies

yum install -y gcc glibc glibc-common make gettext automake autoconf wget openssl-devel net-snmp net-snmp-utils perl-Net-SNMP

Download and extract plugin source

cd /tmp
wget --no-check-certificate -O nagios-plugins.tar.gz https://github.com/nagios-plugins/nagios-plugins/archive/release-2.2.1.tar.gz
tar zxf nagios-plugins.tar.gz

Compile and install plugins

cd nagios-plugins-release-2.2.1/
./tools/setup
./configure
make
make install

Restart services to apply plugins

touch /var/www/html/index.html
service nagios restart
service httpd restart

6. Verify installation

Open a web browser and navigate to http://<em>your‑server</em>/nagios. Log in with the nagiosadmin account created earlier. The Nagios web interface should display the configured services and host status.